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Bengaluru Monday, 27 August, 2018 - 07:57

Life around us is relentlessly diverse and the discovery of many new species every year supports this fact. The reptile world, so far, has about 10,800 species and the count has grown by 20% since the last decade. Hemidactylus, a genus of reptiles that includes the house geckos, is a diverse one with about 150 species spread over a wide geographic range. However, there still exist a few ‘cryptic’ species, where individuals of one species are identical to ones from another species by looks. Scientists use taxonomic and molecular studies to unravel this puzzle for species conservation.

In one such study, a team of researchers from the National Centre for Biological Sciences (NCBS), Bengaluru, Fergusson College, Pune and Veer Narmad South Gujarat University, Gujarat, have unravelled the taxonomy of Hemidactylus triedrus, a gekkonid lizard belonging to the genus Hemidactylus, commonly known as the termite hill gecko. The study was published in the journal PeerJ and was supported by the Singinawa Conservation Foundation and the Department of Science and Technology.

H. triedrus comprises of a group of closely related species spread over a wide geographical area including parts of Pakistan, India and Sri Lanka. Several species were thought to represent H. triedrus leading to taxonomic confusion, which has now been successfully resolved. “My colleagues and I have been working on documentation of reptiles across peninsular India. The fascination that my colleagues and I have for reptiles and documenting its diversity was the main motivation behind this study”, shares Mr Zeeshan Mirza, a researcher from NCBS and an author of the study.

The taxonomy of H. triedrus has an exciting history. The first description of this species was of a male by an unknown collector. Another researcher described a species from Nellore, Andhra Pradesh as H. subtriedrus and marked it as a distinct species without much molecular or morphological evidence. Thus, the validity of H. subtrierdus as a species was questioned. Following this, in 1871-72, another researcher reported H. subtriedrus from Erode, Tamil Nadu. In 1905, Nelson Annandale, a Scottish herpetologist, regarded the specimen from Erode as one that is an intermediate between H. triedrus and H. subtriedrus. However, in due course, the type specimen, based on which the description of subsequent discoveries of Hemidactylus genus is made, was lost from Annandale’s list of Indian gekkonid collection.

William Theobald, a naturalist and staff of the then Geological Survey of India and Burma, presented two accounts of the species concerning Hemidactylus; H. subtriedrus Jerdon (1853) and H. subtriedrus Theobald (1876). Hemidactylus triedrus lankae, the Sri Lankan population, was attributed as a subspecies of H. triedrus. Another group of  researchers proposed the validity of H. subtriedrus without any morphological data and declared that H. triedrus lankae was a species. Nonetheless, the specimens of H. triedrus lankae, based on which the nomenclature is carried out, are now missing or lost, making identification impractical.

In this study, the researchers set out to verify whether H. subtriedrus is a species by itself. They started by collecting a male specimen from Nellore, Andhra Pradesh, where the first specimen of this species was described and compared it with existing museum specimens. Given the widespread distribution and heterogeneity of landscapes in which the species is found, they also collected H. triedrus specimens from Pondicherry, Chennai, Maharashtra, Karnataka, Andhra Pradesh and Gujarat. Upon observation, they found that the specimen from Nellore was identical to those collected from Pondicherry and Chennai, confirming that H. subtriedrus is a synonym of H. triedrus, implying that both are the same species.

To provide evidence to the claim, the researchers recorded body measurements and meristic data like counting the scales, from the collection and museum specimens, followed by analysis of DNA that included a haplotype network to identify variations in the genes that accounts for new species. “A haplotype network is an analysis to identify distinct clusters within a population that might represent distinct species as in our case. In many cases, it is also used to evaluate gene flow from the source population which gives rise to distinct populations”, explains Mr Mirza. Morphological data and anatomy of the skull also underpinned the same.

The results revealed two new species in addition to H. triedrus—the highlight of the study. H. triedrus sensu stricto comprises of individuals from Nellore, Pondicherry and Sri Lankan, while the new species, called H. whitakeri sp. nov. and H. sahgali sp. nov. comprised of populations from from Karnataka, and Maharashtra, Gujarat and parts of Pakistan respectively.

What are the distinct characteristics of these new species? “Males of most gecko species possess a series of scales with a single pore around the cloacal region, and these may extend to the thigh of the animal. These pores are important diagnostic characters, and each species has a fixed number of these pores”, says Mr Mirza.  So, H. sahgali bears 11-15 of these pores and the other two species, H. triedrus and H. whitakeri bear 6-9. On the other hand, H. triedrus has trihedral tubercles, large modified scales which look like pimples, on their back whereas H. whitakeri has sub-trihedral tubercles.

The researchers believe that more work needs to be done regarding the discovery. “We are interested in defining the distribution of each of these species as there is limited data on the distribution, especially for H. whitakeri and H. triedrus. It will be interesting to find out if the ranges of these two species overlap or if they share the same habitat. Results from these will help formulate more interesting projects to study competition, hybridisation etc.”, says Mr Mirza before signing off.

Section: General, Science, Deep-dive Source:
Chennai Friday, 24 August, 2018 - 18:26

On the 20th and 21st of August 2018, the Institute of Mathematical Sciences, Chennai, organised a workshop on “Science, Journalism, Media: Communicating Science in a Changing India”, which was attended by about one hundred attendees. These included India's well-known scientists, science journalists, science communicators and aspiring science writers. Gubbi Labs was also invited to share our experiences in science communication so far.

This article is a brief summary of the discussions that transpired over the course of the two days along with some opinions and observations. For a detailed list of the panel topics and the panellists, please see here. The live tweets of the event are curated here, thanks to the team from NCBS and the videos of the workshop are available here.

The workshop was structured as a series of panel discussions, with each panel having four to six panellists and a moderator. In each session, each of the panellists spoke for a few minutes followed by questions and comments from the audience which the panellists could respond to.

During the first session, on what scientists want from journalists, it was argued that this is a slightly provocative question because on the one hand, asking pilots what they want from journalists would be absurd, while on the other hand, asking politicians what they want from journalists and asking journalists to follow that advice would be dangerous! So where exactly do scientists lie on this spectrum?

It was also pointed out that the aim of inculcating a “scientific temper” that is often widely proclaimed, including in the Constitution of the Republic of India, is not a purely technical matter of communication but has “socio-political” facets which determine what people believe and trust. This is a very pertinent point that is often missed or side-stepped by both scientists and science journalists in the face of the dominant discourse around science communication as being about conveying science to the public in an understandable manner.

There was also discussion about whether journalists should solely report science carried out in India or expand their horizons to report on scientific research elsewhere. The argument for focusing on Indian science is that Indian scientists receive relatively little coverage otherwise while the case for writing on world science is that it would provide more comprehensive coverage of scientific developments worldwide.

The second session titled, “Opinions differ on the shape of the Earth: Balance vs Accuracy” seemed to lack focus, perhaps because the topic wasn’t clearly stated. One panellist opined on the inclusivity of panels as a form of balance. Another panellist claimed that journalism originated with the Gazette de France in 1632 under the patronage of Louis XIII, and that nothing of that sort existed earlier. This claim is controversial, to say the least, even if one were to disregard journalism in antiquity. In fact, the word “gazette” likely owes its origin to the fact that a news bulletin published by the Republic of Venice cost one gazetta, a unit of currency. Similar publications are known to have existed in Ming China too.

R. Prasad, Science Editor of The Hindu giving his views on what has now become a controversial question.

The question of whether science journalists should report on pre-prints of papers posted on websites like arXiv.org was discussed. It was argued that peer-review is not a magic bullet, and therefore it is legitimate to report on research reported in pre-prints. While I have nothing against coverage of research reported in pre-prints, I feel that debating its merits prior to publication is premature. In short, publication in a peer-reviewed journal is a necessary but not sufficient condition for a research result to be considered well established and therefore worthy of debate. I have discussed my views on this topic in detail here.

It was felt that journalists should avoid “false balance,” i.e. giving equal coverage to opposing points of view, although substantial evidence supports one point of view over the other. On the other hand, it could be argued that granting equal time and opportunity to both sides is not a judgement about the quality of the arguments, but is merely offering an opportunity for the audiences to hear all cases and examine the evidence before reaching conclusions. In my view, failure to present and discuss the evidence objectively is a much greater danger than providing time for arguments unsupported by evidence.

The post-lunch session was opened by a discussion about, “Ancient Indian Aviation Technology: Pseudoscience in the media and from the government.” The Popperian notion of science based on empirical falsifiability was posed as the dividing line between science and pseudo-science. This view of science, although nearly universal among science writers particular from America, is not as well established among philosophers of science. While the Popperian view of science was well explained, there was no discussion of its limitations or challenges to it from various quarters, not just Kuhn in the twentieth century, but also others before Popper who set other kinds of criteria, starting as far back as Alhazen and Bacon.

One of the panellists argued against “scientism” by which the speaker meant the misapplication of scientific method and criteria to situations where they were apparently inapplicable. For example, it was argued that while scientific tests exist for mainstream medicine (pejoratively referred to as “allopathy”), no such tests exist for alternative medicine. This view was vigorously challenged during the discussion with the counterpoint that the effectiveness of any medication was testable through clinical trials or observational studies regardless of its origin or any metaphysics that went with it. It was not entirely clear which of these were the panellist’s own views as opposed to the views expressed in an editorial in a science publication that he was discussing. Finally, it was argued that falsifiability is a difficult concept to convey to the general public, a view that I find very difficult to agree with as it appears to be no more complex than other philosophical and scientific concepts that are generally conveyed.

There was a rather bizarre suggestion to create a repository of all the achievements and knowledge of ancient India to combat the ever-growing claims that some scientific principle or technology existed in ancient India.

In my view, it is much more important to combat false scientific claims than fanciful, false claims about the history of science. Perhaps this point would be easier to appreciate if one considers an example well separated from present-day India in time and space. With the benefit of hindsight, few would take issue with the proposition that combating eugenics was of greater importance than countering false claims that Einstein plagiarised his work in inter-war central Europe.

The next session was about why there are so few women and minorities in science. This was perhaps the least well-conducted session of the day.

It was argued that “manels” (men-only panels) were to be called out and avoided. This is undoubtedly true if one were to be selecting jury panels from among the general public where both genders are roughly equal in number. But surely, if the panel is being selected from among a population that is already heavily gender-weighted, the issue to be addressed lies elsewhere, and not in the selection of the panel. In these circumstances, if there were to be affirmative action in panel selection without any other action, the underlying issues would remain unaddressed, and even less visible than before.

There was no discussion about minorities, which in the Indian context presumably was meant to refer to religious minorities. The stated reason was that the chair of the panel did not feel comfortable discussing issues relating to minorities as she did not belong to a minority group. In my view, this should have been communicated to the organisers in advance who could have then made alternative or additional arrangements. Furthermore, issues of representation of “oppressed nationalities” and “disadvantaged communities” was not even sought to be discussed. The same can be said of the vexed question of whether disadvantage should be located in individual circumstances or group identity or some combination of the two.

Following the workshop, some participants have expressed the view that sexual harassment in academia was not discussed at all (see here and here for more). The issue of sexual harassment was not raised in any of the panel discussions, but there were a few remarks and questions from the audience.

The final session of the first day, which sought perspectives from institutions, funders and policymakers, was dominated by criticism of the Indian science academies. This appeared to be taking off from a previous discussion that the author was not a part of, so it was difficult to make anything of it. There was an interesting suggestion of three-fold publication where scientists publish all research thrice over, once in peer-reviewed journals for fellow experts as is done presently, once for a somewhat more general audience but within the broader field and one final time for the general public. This would inevitably entail a substantial reduction in per capita output, but it was argued that it would come with an increase in quality.

The second day began with a discussion about what science journalists want from scientists, the topic of the first session of the first day, turned on its head. Journalists wanted scientists to be accessible and respond to queries in a timely fashion in addition to playing a more significant role in critiquing the work of other scientists. It was clarified that government rules do not prohibit scientists from talking to journalists about their work, but it was argued that directors of some institutes interpret the rules in a manner that prevents effective communication between scientists and journalists. Clearly, there is a need for a quick redressal mechanism in case journalists seek information, and directors of institutes block their requests citing government rules.

The second session was about communicating science in Indian languages. It was argued, persuasively, that contrary to the plaudits and at times glamour that accrues to English language science journalists, those working in Indian languages face greater difficulties and often bear the brunt of attacks on scientific temper and even physical attacks. Nevertheless, a substantial fraction of the Indian population is not conversant in English, and therefore science communication in Indian languages can have greater reach and effect. It was pointed out that journalists should not alienate themselves from the public and posit “the public” as a distinct category, but recognise that they too are part of the public. Some interesting examples of successful science journalism in Indian languages were exhibited. As very few people are conversant in multiple Indian languages, publicising such examples in English can enable others to follow suit in their own Indian languages.

The largest panel of the workshop discussing science communication in Indian languages.

The post-lunch session was about tackling stereotypes about science and scientists. There are many kinds of common stereotypes about science and scientists, and it was argued that scientists and science journalists must combat them. While false stereotypes, like science being about creating “dirty smells in a laboratory”, can and should be debunked, it is more difficult to deal with stereotypes that are generalisations drawn from normal behaviour, but perhaps misapplied as universals. For example, the stereotype that science journalists with PhDs are failed scientists may be right on average, but it does not mean that every such individual is a failed scientist. Nevertheless, it has a detrimental effect on science PhDs who would like to consider a career in journalism.

The session on “Science as Storytelling” set up a lively debate between those who argued that conveying scientific information in narrative form creates the illusion of understanding and others who contended that stories could help make science more interesting to those who may not otherwise be interested in science, and that they could always consult more technical sources if they wished to learn more.

Spoorthy Raman, Managing Editor of Gubbi Labs telling the story of science.

The final session on “Opportunities in Science and Science Journalism: Where are the jobs, the students and the teachers?” seemed to raise more questions than provide answers. It was generally agreed that opportunities are few and far between for aspiring and existing science journalists. At the same time, it was recognised that easy access to content creation on social media and electronic media means that those who do not need to derive an income from it can easily publicise their opinions and analyses.

In summary, it was a delightful two-day conference, perhaps one of the most enjoyable I have ever been to. The format of panel discussions greatly facilitated this and was best suited to the nature of topics discussed. I only wish the final session was left free for open discussion of all issues raised earlier amongst all participants with a moderator in place.

Section: General, Science, Events Source:
Bengaluru Friday, 24 August, 2018 - 08:12

The changing climate across the world is ringing alarm bells with its devastating effects on all life forms and their habitats. The crown of India, the Himalayas, a biodiversity hotspot famous for its climatic and altitudinal variations is not spared from these effects! There are about 10000 species of plants in the Himalayas, and about 3000 of them are endemic, found nowhere else. Most of the 300 species of mammals found in the Himalayan landscape are exclusively adapted for the mountain habitat and are the verge of calamity should the landscape and climate change. However, now that climate change is real and the habitats are changing, how are these animals and plants responding?

In a new study, researchers from the Indian Institute of Science (IISc), Bengaluru, and the University of Sheffield, UK, have studied how smaller herbivores, like the Royale’s pika (Ochotona roylei), are being sensitive to the alarming changes in the global climate. Pikas are known to be vulnerable to climate change in places other than the Himalayas, where there are reports of American pikas going extinct in the northwestern parts of the United States due to changes in the climate. The current study is published in the Journal of Molecular Ecology and is supported by the Commonwealth Professional Fellowship, DBT Research Associate programme and the Wellcome Trust-DBT India Alliance.

Most of the Himalayan vegetation today consist of C3 plants that thrive in wet, cold climate and higher elevations. They photosynthesise by absorbing carbon dioxide from the air and converting that into sugars. As temperatures increase, there is a looming risk that another class of plants, called ‘C4 plants’, which are best suited for hot and dry climate, could replace them. The C4 plants have a different photosynthesis process where they use the carbon dioxide bound to sugar rather than absorbing it from the air. Hence, the loss of C3 plants not only affects plant diversity but also has detrimental effects on herbivores who exclusively rely on these plants for their diet.

The researchers of this study started off by analysing the dietary composition of the Royle’s pika—small herbivores related to rabbits and play an essential role in the food chain of the mountain ecosystems. They are often eaten by many carnivores and raptors, especially during winter when all other rodents hibernate.

The study found that the diet of pikas included more than 70 genera of plants, out of which around 60% were endemic to the Himalayas. More than 90% of the analysed dietary plants of the Royle’s pika are found to be alpine C3 plants. “Pikas prefer C3 plants which are mainly herbaceous and are rich in nitrogen and moisture with low amounts of fibre”, says Dr Sabuj Bhattacharyya, the lead author of the study, talking about the findings. The researchers have non invasively estimated the dietary composition by collecting faecal samples of the Royle’s pika after which they have analysed them using a modern method called DNA metabarcoding.

“DNA metabarcoding can be very useful in diet analysis as it is often difficult to note down all the possible diet items through visual observation or faecal samples. This method allows us to combine the amplification product for multiple genes belongs to a large number of samples and sequence them simultaneously. This method can generate a very high amount of data even with very low-quality DNA samples such as faecal samples”, explains Dr Bhattacharyya.

How then would the pikas react to the changing climate? “Pikas are cold-adapted species and are now restricted to high elevation areas. If the climate in these elevations become hot, they would want to move to higher elevations to find a suitable habitat. However, in several mountains regions they are already on the top and have no place to go”, says Dr Bhattacharyya. “To survive, they either have to go down and find alternative habitats in other taller mountains or die. If they choose to go down to find other habitats, they will face challenges like hot environment, lethal heat stress, high predation risk, and the lack of food ”, he says.

When the pikas’ diet falls apart, it isn't just the loss of pikas! With the current rate of climate change predicting a reduction from 24 to 42% in endemic plant species in the Himalayas by 2080, there is so much more to lose! “The Royle's pika is classified as ‘least concern’, but my previous studies show that they are also sensitive to changes in snow or temperature like their American cousins, acting as indicators of climate change. The loss of pikas from food web will result in the breakdown of the entire food web in the alpine region”, warns Dr Bhattacharyya.

The study highlights just one aspect of the damage that the changing climate could bring in for the Himalayas. “Pikas are becoming a victim of climate change due to anthropogenic activities. If we do not accept the fact that climate change is real, and work together to mitigate its impact, then we might also lose our habitats/home like the pikas”, says Dr Bhattacharyya.

The researchers also emphasise the need for more such ecological studies on the effects of climate change in the battered Himalayas. “The Himalayans has not received much attention for long-term research to understand which species are already facing the negative impact of climate change. In general, the changing climate is predicted to bring in changes to the temperature and precipitation in this region. Hence, there are many more that would be affected by the resulting heat stress, change in food availability and increase in disease susceptibility”, says Dr Bhattacharyya, before signing off.

Section: General, Science, Ecology, Deep-dive Source:
Mumbai Thursday, 23 August, 2018 - 07:43

The Internet is the world’s largest ‘suggestion box’. Haven’t we all looked at the reviews left by millions before we buy a product online or decide to watch a movie? For online marketplaces, these reviews can help or dent their revenues. Hence, companies scramble to ‘understand’ the sentiment of their customers using tools that can read millions of such reviews each day and detect if the customer is happy, angry or disappointed. One such sentiment that has been difficult to comprehend is sarcasm.  A team led by Prof. Pushpak Bhattacharyya of IIT Bombay, have analysed various ways of detecting sentiments, especially sarcasm, in online text, using a computer.

“Large organisations (political, commercial, etc.) use social media to understand what people think of them. This can also be applied to text such as employee appraisals, feedback forms in hotels, etc.”, explains Dr Aditya Joshi, and an author of the research published in ACM Computing Surveys. Online reviews come in various forms. Some are straightforward, clearly saying if the customer is happy or not. But there are some like this—“Absolutely incredible! This dye turned my hair the exact shade of red I’ve always wanted!” At first glance, it might appear to be a positive statement, unless this was a review for black hair dye. If a potential buyer knows that extra piece of information, she will be able to decipher the sarcasm in the review! Now, what if a computer is trying to analyse the sentiment? Can it detect the sarcasm? It can, says the current study as it sheds light on the different approaches used for detecting sarcasm in a body of text.

Sarcasm has been traditionally known to be a pain in the neck for many sentiment analysis systems. Therefore, a focused research on detection of sarcasm becomes useful,” says Dr Joshi talking about the motivation behind this study. Dr. Joshi, Prof Pushpak Bhattacharyya and Dr Mark Carman have co-authored a book, Investigations in Computational Sarcasm, which provides a holistic view of past work in computational sarcasm and the challenges and opportunities that lie ahead.

Approaches to detecting sarcasm

Just like humans, computers also ‘learn’ to detect sarcasm by looking at various examples of it. One way to help computers learn is to ‘train’ them using large-scale data from Twitter where hashtags like #sarcasm and #not indicate sarcastic tweets. But, Twitter is only one mode of communication, there are other websites without helpful hashtags that may also contain sarcastic text.

Therefore, one of the early approaches in this field was to identify sarcastic patterns like positive verbs with negative phrases, as in “I love being awake at 4 am with a headache!” and then use them as variables for a sarcasm or statistical classifier—a function that trains the computer to identify sarcastic text using a data set of examples. One of the studies described in the paper shows that using the Logistic Regression classifier---a classifier that checks if certain conditions are true or false for a statement---is accurate about 81% of the time.

Another method of obtaining samples is using human annotators to manually classify text as sarcastic or not, especially where the text is long and identifiers like hashtags are not present. This, however, presents a unique problem considering that annotators come from different backgrounds. “One of our papers talks about the role of cultures in detecting sarcasm. We compared Americans and Indians and how their perception of what constitutes sarcasm may differ,” explains Dr Joshi. The statement “It’s sunny outside and I am at work. Yay” was considered sarcastic by American annotators but non-sarcastic by their Indian counterparts due to India’s climate.

As we well know, sometimes even people struggle to understand the tone of emails and texts, or to tell if someone is being sincere when they exclaim, “I love your hair!” Then how does a computer understand the tone? Certain statements are obvious in their causticity - “Being ignored is the best feeling ever!” is rarely, if at all, to be taken at face value. On the other hand, the sentence, “I enjoy working on math problems all weekend!” could be construed as sarcastic for people who despise Mathematics, but a true statement for those who love the subject. In many instances, context is the key. Just as humans need a backstory, so do computers, and the recent trend in computational research is to make use of just that. In the case of tweets, the ones that are not specifically identified by the author as sarcastic require some backstory, i.e. the remarks that came before and after the target text. It gives an idea of the author’s past sentiment regarding that topic and helps the computer to gain an understanding of the person’s mindset and whether he or she was being sarcastic or not when he or she tweeted “Politicians are never wrong #politics”.

Sarcasm comes in flavours

Other directions that sarcasm detection has begun to take are identifying the different types of sarcasm, differentiating between irony and sarcasm, and incorporating language and culture-specific traits in the evaluation process. Although much of the research exists for English, the same methods can be used for other languages. “Since machine learning methods are based on extracting appropriate indicators of sarcasm, the methods hold, given that corresponding dataset in the respective language or culture is available. However, a (single) universal sarcasm classifier would be a myth,” states Dr Joshi. The dataset or the features of the classifier would have to be modified based on the language and culture of the area. “Mapping sarcasm detection approaches across cultures and languages is one possible way forward,” he adds.

However, in training systems to understand sarcasm, is there a possibility that these systems use sarcasm on us as well? Not automatically, says Dr Joshi, but they can be programmed to be sarcastic in the right situation. Siri, Cortana, or digital assistants on shopping portals are chatbots. They are computer programs that talk/act like humans. “Bots can likely be trained to be sarcastic, but they cannot be sarcastic all the time. So, if chatbots are mere assistants, it is important for software architects and others to evaluate situations in which a chatbot needs to be sarcastic! You wouldn't want a chatbot to be sarcastic in a formal setting. However, if an angry customer is rude to a chatbot for a long time, the bot might decide to pull out a sarcastic response. As you can clearly see, *when* a bot can be sarcastic is very similar to when a human can be sarcastic.”

It is all well and good for a sentiment detection system to tell if a statement is positive or negative. However, when the same system is able to comprehend sarcasm as well, it shows a 4% improvement in accurately identifying the emotion behind the text. “Advances in sarcasm detection are key missing pieces of the sentiment analysis puzzle. Sentiment analysis papers would merely shrug their shoulders when asked about their ability to handle sentiment in sarcastic sentences. With sarcasm detection, sentiment analysis systems can cover a larger ground,” signs off Dr Joshi.

Section: General, Science, Technology, Deep-dive Source:
ಬೆಂಗಳೂರು Wednesday, 22 August, 2018 - 09:02

ಹೆನ್ರಿ ಸುವಿಲ್ಲನ್ ಥಾಮಸ್ 1873 ರಲ್ಲಿ ಪ್ರಕಟವಾದ ತಮ್ಮ ‘ಎ ರಾಡ್ ಇನ್ ಇಂಡಿಯಾ’ ಎಂಬ ಪುಸ್ತಕದಲ್ಲಿ ಭಾರತೀಯ ಕ್ರೀಡಾ ಮೀನುಗಾರಿಕೆಯ ಹಲವು ಆಯಾಮಗಳನ್ನು, ಅದರ ತಂತ್ರೋಪಾಯಗಳನ್ನು ಉಲ್ಲೇಖಿಸುತ್ತಾರೆ. ಈ ಪುಸ್ತಕದಲ್ಲಿ ಮೋಜಿನ ಆಟಕ್ಕಾಗಿ ಬಳಸುವ ‘ಗೂನು ಬೆನ್ನಿನ ಮಹಶೀರ್ (ಸಿಹಿ ನೀರಿನ)’ ಮೀನಿನ ಬಗ್ಗೆ ಪ್ರಮುಖವಾಗಿ ಉಲ್ಲೇಖಿಸಿದ್ದಾರೆ. ಈ ಮೀನು ಸುಮಾರು 1.5 ಮೀಟರ್ ಉದ್ದ ಹಾಗೂ 55 ಕಿಲೊ ಗ್ರಾಮ್ ತೂಕದಷ್ಟು ದೈತ್ಯಾಕಾರವಾಗಿ ಬೆಳೆಯಬಹುದು. ದಕ್ಷಿಣ ಭಾರತದ ದೇಶೀಯ ಮೀನಾಗಿರುವ ಇದು, ಜಗತ್ತಿನ ಎಲ್ಲಾ ಮೀನುಗಾರರಿಗೂ ‘ದೈತ್ಯ, ಕಠಿಣ ಹೋರಾಟ ಮನೋಭಾವದ ಹಾಗೂ ಅತ್ಯಂತ ಪ್ರಮುಖ ಆಟದ ಮೀನು’ ಎಂದೇ ಪರಿಚಿತ. ಆದರೆ ವಿಪರ್ಯಾಸದ ಸಂಗತಿಯೇನು ಗೊತ್ತೇ? ಸುಮಾರು ನೂರೈವತ್ತು ವರ್ಷಗಳಿಂದ ಈ ಮೀನಿನ ತಳಿಯ ಬಗ್ಗೆ ಮಿತವಾಗಿ ತಿಳಿದಿದ್ದರೂ, ಅದರ ಬಗೆಗಿನ  ಅರಿವು ತುಂಬಾ ಸೀಮಿತವಾಗಿತ್ತು, ಈ ಮೀನಿಗೆ ವೈಜ್ಞಾನಿಕ ಹೆಸರನ್ನು ಕೂಡ ನೀಡಲಾಗಿರಲಿಲ್ಲ.

ಈ ವಿಷಯದಲ್ಲಿ ನಾವು ಇಂಗ್ಲೆಂಡಿನ ಬೌರ್ನಮೌತ್ ವಿಶ್ವವಿದ್ಯಾಲಯದ ವಿಜ್ಞಾನಿಗಳು ನಡೆಸಿದ ಸಂಶೋಧನೆಗೆ ಧನ್ಯವಾದ ತಿಳಿಸಲೇಬೇಕು. ಈ ಕ್ರೀಡಾ ಮೀನು ಕಾವೇರಿ ನದಿ ಹಾಗೂ ಅದರ ಉಪನದಿಗಳ ಸ್ಥಳೀಯ ಮೀನಾಗಿದ್ದು, ನೈಸರ್ಗಿಕ ಒತ್ತಡ ಹಾಗೂ ಜಲ ವಿತರಣಾ ನಿರ್ಬಂಧಗಳ ಕಾರಣದಿಂದ ಇಂದು ವಿನಾಶದ ಅಂಚಿಗೆ ಬಂದು ನಿಂತಿರುವುದು ನಿಜಕ್ಕೂ ವಿಷಾದದ ಸಂಗತಿ. ಇತ್ತೀಚಿನ ಅಧ್ಯಯನದಲ್ಲಿ ವಿಜ್ಞಾನಿಗಳು ಈ ಮತ್ಸ್ಯಜೀವಕ್ಕೆ ‘ಟಾರ್ ರೆಮಾದೇವಿ’ ಎಂಬ ವೈಜ್ಞಾನಿಕ ಹೆಸರನ್ನಿಟ್ಟಿದ್ದಾರೆ. 

“ಇಂತಹ ಅದ್ಭುತವಾದ ಜಗತ್ಪ್ರಸಿದ್ಧ ಜೀವಿಯೊಂದು ವೈಜ್ಞಾನಿಕ ಹೆಸರನ್ನು ಪಡೆಯುವ ಮೊದಲೇ ಅಳಿವಿನಂಚಿಗೆ ಬಂದು ನಿಂತಿರುವುದು, ನಿಜವಾಗಿಯೂ ನಂಬಲಾಗದ ಸಂಗತಿ” ಎನ್ನುತ್ತಾರೆ ಬೌರ್ನಮೌತ್ ವಿಶ್ವವಿದ್ಯಾಲಯದ ಮುಖ್ಯ ವಿಜ್ಞಾನಿ ಆಡ್ರಿಯನ್ ಪಿಂಡರ್. ಇವರು  ಮಹಶೀರ್ ತಳಿಯ ರಕ್ಷಣೆಗಾಗಿ ಸ್ಥಾಪಿಸಲಾಗಿರುವ ಮಹಶೀರ್ ಟ್ರಸ್ಟ್ನ ನಿರ್ದೇಶಕರು ಕೂಡ ಹೌದು.

ಎಲ್ಲವೂ ಸರಿ, ಆದರೆ ಹೆಸರಲ್ಲೇನಿದೆ? ಎಂದು ನೀವು ಪ್ರಶ್ನಿಸಬಹುದು. ವೈಜ್ಞಾನಿಕ ಹೆಸರಿಲ್ಲದಿರುವ ಕಾರಣಕ್ಕಾಗಿಯೇ ‘ಗೂನು ಬೆನ್ನಿನ ಮಹಶೀರ್’ ಮೀನನ್ನು ಐ.ಯು.ಸಿ.ಎನ್. ಸಂಸ್ಥೆ ತನ್ನ ‘ಅಳಿವಿನಂಚಿನಲ್ಲಿರುವ ತಳಿ’ಗಳ ಪಟ್ಟಿಯಲ್ಲಿ ಸೇರಿಸಿಕೊಂಡಿರಲಿಲ್ಲ. ಈ ಪಟ್ಟಿಯು ಜಗತ್ತಿನ ಎಲ್ಲ ಅಳಿವಿನಂಚಿನ ಸಸ್ಯರಾಶಿ ಹಾಗೂ ಪ್ರಾಣಿ-ತಳಿಗಳನ್ನು ಒಳಗೊಂಡಿದೆ. ಈ ಮೀನಿಗೆ ನಿರ್ದಿಷ್ಟ ಸಂರಕ್ಷಣೆಯ ಸ್ಥಾನ ಇರದಿರುವ ಕಾರಣದಿಂದ, ಮೀನಿನ ಸಂಖ್ಯೆಗಳ ಮೇಲ್ವಿಚಾರಣೆ ಇಲ್ಲದೆಯೆ ಅವುಗಳನ್ನು ಉಳಿಸಲು ಯಾವುದೇ ಕ್ರಮಗಳನ್ನು ತೆಗೆದುಕೊಳ್ಳಲು ಕೂಡ ಸಾಧ್ಯವಾಗಿಲ್ಲ.

ಸಿಡಿಮದ್ದುಗಳನ್ನು ಬಳಸಿಕೊಂಡು ಮಾಡುವ ಅತಿಯಾದ ಮೀನುಗಾರಿಕೆಯ ಕಾರಣದಿಂದ ಸಾಮೂಹಿಕವಾಗಿ ಮೀನುಗಳು ನಾಶವಾಗುತ್ತಿವೆ ಎಂಬುದು ಇಲ್ಲಿ ಗಮನಿಸಬೇಕಾದ ಸಂಗತಿ. ಮಾನವನ ಸ್ವಾರ್ಥಕ್ಕಾಗಿ ತನಗಿಷ್ಟ ಬಂದಂತೆ ನಿರ್ಮಿಸಿಕೊಳ್ಳುವ ಆಣೆಕಟ್ಟುಗಳು, ಕಾವೇರಿ ನದಿಯುದ್ದಕ್ಕೂ ಕಟ್ಟಲಾಗಿರುವ ತಡೆಗೋಡೆಗಳು ಗೂನು ಬೆನ್ನಿನ ಮಹಶೀರ್ ಮೀನಿಗೆ ಹಾನಿಯನ್ನುಂಟು ಮಾಡಿವೆ. 2004 ರಿಂದ ಈಚೆಗೆ, ಮೀನು ಹಿಡಿಯುವವರ ಸಹಾಯದಿಂದ ಕಲೆ ಹಾಕಿರುವ ಮಾಹಿತಿಯ ಪ್ರಕಾರ, ಈ ತಳಿಯ ಮೀನಿನ ಸಂಖ್ಯೆಯಲ್ಲಿ ಗಣನೀಯವಾಗಿ ಇಳಿಕೆಯಾಗಿರುವುದು ಕಂಡು ಬಂದಿದ್ದು, ಈ ಮೀನನ್ನು ಅಳಿವಿನಂಚಿಗೆ ನೂಕಿದೆ.

“ಈ ಜಾತಿಯ ಮೀನುಗಳನ್ನು ರಕ್ಷಿಸುವುದು ಅನಿವಾರ್ಯ ಎಂಬುದು ನಮ್ಮ ಅರಿವಿನಲ್ಲಿತ್ತು. ಕಾವೇರಿ ನದಿಯ ಈ ಸಾಂಪ್ರದಾಯಿಕ ಜಾತಿಯ ಮೀನು ನಾಶವಾದಲ್ಲಿ, ಅದರಿಂದ ನದಿಯಲ್ಲಿ ಅನೇಕ ತ್ವರಿತ ಪರಿಣಾಮಗಳೂ ಸಹ ಉಂಟಾಗಬಹುದು. ಇವು ಪರಭಕ್ಷಕ ಜೀವಿಗಳಾಗಿರುವುದರಿಂದ ಗೂನು ಬೆನ್ನಿನ ಮಹಶೀರ್ ಮೀನಿನ ನಾಶವು ನದಿಯ ಉಳಿದ ಜೀವಿಗಳ ಸಂಖ್ಯೆಯನ್ನು ಹೆಚ್ಚಿಸಿ, ವಿಶಾಲವಾದ ಜೀವವೈವಿಧ್ಯತೆಗೂ ಸಹ ಎಡೆಮಾಡಿ ಕೊಡಬಹುದು” ಎನ್ನುವ ಸೂಕ್ಷ್ಮ ಸಂದೇಶವನ್ನು ಆಡ್ರಿಯನ್ ನೀಡುತ್ತಾರೆ.

ಈ ಮೀನಿಗೆ ವೈಜ್ಞಾನಿಕ ಹೆಸರನ್ನು ನೀಡುವ ದೃಷ್ಟಿಯಿಂದ ಮೊದಲ ಹಂತವಾಗಿ ವಿಜ್ಞಾನಿಗಳು ವರ್ಗೀಕರಣಕ್ಕೆ ಸಹಾಯವಾಗುವಂತಹ ಇವುಗಳ ಮಾದರಿಗಳನ್ನು ಸಂಗ್ರಹಿಸಲಾರಂಭಿಸಿದರು. ಇದರ ಸಲುವಾಗಿಯೆ ಕಾವೇರಿ ನದಿಯ ಹರಿವಿರುವಂತಹ ರಾಜ್ಯಗಳಾದ ಕರ್ನಾಟಕ, ಕೇರಳ ಹಾಗೂ ತಮಿಳುನಾಡಿನ ವಿಜ್ಞಾನಿಗಳನ್ನೊಳಗೊಂಡತಹ ಒಂದು ವಿಶೇಷ ತಂಡವೊಂದನ್ನು ನಿರ್ಮಿಸಿ, ಮೀನಿನ ದೇಹದ ಉದ್ದಳತೆ ಹಾಗೂ ಡಿಎನ್ಎ ಸ್ಯಾಂಪಲ್ಗಳನ್ನು ಕಲೆಹಾಕಿದರು.

“ಇದು ಅಳಿವಿನಂಚಿನಲ್ಲಿರುವ ಜೀವರಾಶಿ ಎಂದು ತಿಳಿಯುವಷ್ಟರಲ್ಲಿಯೇ, ಇವುಗಳ ಮಾದರಿಗಳನ್ನು ಹುಡುಕುವುದು ಬಹುದೊಡ್ಡ ಸವಾಲು ಎಂಬುದರ ಅರಿವು ನಮಗಾಗತೊಡಗಿತು” ಎಂದು ತಮ್ಮ ಅನುಭವವನ್ನು ಆಡ್ರಿಯನ್ ಹಂಚಿಕೊಳ್ಳುತ್ತಾರೆ.

ಕೊನೆಗೂ ವಿಜ್ಞಾನಿಗಳು ಸ್ಥಳೀಯ ಬುಡಕಟ್ಟು ಜನಾಂಗದ ಬೆಸ್ತರು ಹಾಗೂ ಮೀನುಗಾರರ ಸಹಾಯದಿಂದ ತಮಿಳುನಾಡಿನ ಮೊಯ್ಯಾರ್ ನದಿಯಲ್ಲಿ ಮಹಶೀರ್ ಮೀನಿನ ಸಂಖ್ಯೆ ಹೆಚ್ಚಿಗೆ ಇರುವುದನ್ನು ಕಂಡುಹಿಡಿದರು.

ಇಲ್ಲಿ ನಡೆಸಿದ ಅಧ್ಯಯನಗಳು ಹಾಗೂ ವಿಶ್ಲೇಷಣೆಗಳು ತೋರಿಸುವಂತೆ, ಗೂನು ಬೆನ್ನಿನ ಮಹಶೀರ್ ಮೀನಿನ ಡಿಎನ್ಎ ಕ್ರಮವು ವಿಶಿಷ್ಟವಾಗಿದೆ, ಇದು ಹಿಂದೆ ವಿವರಿಸಿದ ಎಲ್ಲಾ ಜಾತಿಗಳ ಮೀನುಗಳಿಗಿಂತ ಭಿನ್ನವಾಗಿದೆ ಎಂಬುದು ನಿಜಕ್ಕೂ ಕುತೂಹಲಕಾರಿ ಸಂಗತಿ. ಸಂಶೋಧಕರು ತಾವು ಹೊಸ ಜಾತಿ ಮೀನೊಂದನ್ನು ಗುರುತಿಸಿದ್ದೇವೆಯೆಂದೇ ನಂಬಿದ್ದರು. ಆದರೆ 2007 ರ ಅಧ್ಯಯನವೊಂದು ಅದಾಗಲೇ ಈ ತರಹದ ಮೀನಾದ ‘ಟಾರ್ ರೆಮಾದೇವಿ’ ಬಗ್ಗೆ ವಿಶ್ಲೇಷಿಸಿರುವುದು ಕಂಡುಬಂದಿತು. ಆದರೆ ಈ ಅಧ್ಯಯನದ ಮಾಹಿತಿಗಳು ಪೂರ್ಣ ಪ್ರಮಾಣದ್ದಾಗಿರಲಿಲ್ಲ. ಕಾವೇರಿ ನದಿಯ ಉಪನದಿಯಾದ, ತಮಿಳುನಾಡು ಹಾಗೂ ಕೇರಳದ ಪಂಬರ್ ನಲ್ಲಿ ಕಂಡು ಬರುವ ಒಂದು ಪುಟ್ಟ ಮೀನಿನ ಜಾತಿಯ ಕೆಲವು ಮಾದರಿಗಳನ್ನು ಮಾತ್ರವೇ ಇದು ಸಂಗ್ರಹಿಸಿತ್ತು. 

ಆದರೆ ಈ ಮಾಹಿತಿ ಇನ್ನಷ್ಟು ಕುತೂಹಲವನ್ನು ಕೆರಳಿಸಿತು. ಇದರ ಪರಿಣಾಮವಾಗಿ ಸಂಶೋಧಕರು ಟಾರ್ ರೆಮಾದೇವಿ ಮೀನಿನ ಭೌಗೋಳಿಕ ಮೂಲವನ್ನು ಹುಡುಕಲು ಹೊರಟರು. ಮ್ಯೂಸಿಯಂನ ಕೆಲವು ಮಾದರಿಗಳನ್ನು ವಿವರವಾಗಿ ಪರಿಶೀಲಿಸಿದರು. ಈ ತನಿಖೆಯ ಫಲಿತಾಂಶಗಳು ಗೂನು ಬೆನ್ನಿನ ಮಹಶೀರ್ ಮೀನು ವಾಸ್ತವವಾಗಿ ಟಾರ್ ರೆಮಾದೇವಿಯನ್ನೇ ಹೋಲುತ್ತದೆ ಎಂದು ದೃಢಪಡಿಸಿದವು. ಇದೇ ಆಧಾರದ ಮೇರೆಗೆ ಸಂಶೋಧಕರು ತಮ್ಮ ಸಂಶೋಧನೆಗಳನ್ನು PLOS ONE ಪತ್ರಿಕೆಯಲ್ಲಿ ಪ್ರಕಟಿಸಿದರು.

ಈ ಸಂಶೋಧನಾ ಅಧ್ಯಯನ ವಿಜ್ಞಾನ ಜಗತ್ತಿನಲ್ಲಿ ಎಂತಹ ಸಂಚಲನವನ್ನು ಸೃಷ್ಟಿಸಿತೆಂದರೆ, ಇಂಟರ್ನ್ಯಾಷನಲ್ ಯೂನಿಯನ್ ಫಾರ್ ಕನ್ಸರ್ವೇಶನ್ ಆಫ್ ನೇಚರ್ (ಐ.ಯು.ಸಿ.ಎನ್.) ಕೂಡಲೆ ಎಲ್ಲಾ ತಜ್ಞರ ಒಂದು ತುರ್ತು ಸಭೆಯನ್ನು ಪುಣೆಯಲ್ಲಿ  ಏರ್ಪಡಿಸಿತು. ಸಭೆಯಲ್ಲಿ ‘ಟಾರ್ ರೆಮಾದೇವಿ’ಯ ರೆಡ್ ಲಿಸ್ಟ್ ಅಸೆಸ್ಮೆಂಟ್ನ ಕರಡು ಪ್ರತಿ ಸಿದ್ಧವಾಯಿತು ಅಂದರೆ ಈ ಮೀನನ್ನು ‘ಅಳಿವಿನಂಚಿನಲ್ಲಿರುವ ತಳಿ’ಗಳ ಪಟ್ಟಿಗೆ ಸೇರಿಸುವ ಕರಡು ಪ್ರತಿಯನ್ನು ಸಿದ್ಧಪಡಿಸಲಾಯಿತು. "ಜೀವರಾಶಿಗಳನ್ನು ಹಾಗೂ ಅವುಗಳ ವಿಶಿಷ್ಟ ತಳಿಗಳನ್ನು ವಿನಾಶದಿಂದ ರಕ್ಷಿಸಲು, ಅವುಗಳಿಗೆ ಅತೀ ಅಗತ್ಯವಾದ ರಕ್ಷಣೆ ಮತ್ತು ತಕ್ಷಣದ ಸಂರಕ್ಷಣಾ ಯೋಜನೆಯನ್ನು ನೀಡುವ ನಿಟ್ಟಿನಲ್ಲಿ ಇದೊಂದು ಪ್ರಮುಖ ಕ್ರಮವಾಗಿದೆ" ಎಂದು ಆಡ್ರಿಯನ್ ವಿವರಿಸುತ್ತಾರೆ. 

“ಸದ್ಯದ ಪರಿಸ್ಥಿತಿಯಲ್ಲಿ ಗೂನು ಬೆನ್ನಿನ ಮಹಶೀರ್ ಮೀನು ಒಂದು ನಿರ್ಬಂಧಿತ ಹಾಗೂ ಅಪಾಯಕಾರಿ ಸ್ಥಿತಿಯಲ್ಲಿರುವ ತಳಿಯಾಗಿದೆ. ಇದನ್ನುಳಿಸುವ ದೃಷ್ಟಿಯಲ್ಲಿ ಅತೀಯಾದ ಗಮನ ಹಾಗೂ ಕಾರ್ಯ ಎರಡರ ಅವಶ್ಯಕತೆಯೂ ಇದೆ” ಎಂಬ ಕಳಕಳಿಯ ಮಾಹಿತಿಯನ್ನು, ಕೇರಳದ ‘ಮೀನುಗಾರಿಕೆ ಮತ್ತು ಸಾಗರ ಅಧ್ಯಯನ’ಗಳ ವಿಶ್ವವಿದ್ಯಾಲಯದ ಸಹಾಯಕ ಪ್ರಾಧ್ಯಾಪಕರಾಗಿರುವ ಡಾ. ರಾಜೀವ್ ರಾಘವನ್ ನೀಡುತ್ತಾರೆ. ಇವರು ಐ.ಯು.ಸಿ.ಎನ್ ನ ಫ್ರೆಶ್ವಾಟರ್ ಫಿಶ್ ರೆಡ್ ಲಿಸ್ಟ್ ಅಥಾರಿಟಿಯ ಸಂಯೋಜಕರು ಹಾಗೂ ಈ ಅಧ್ಯಯನದ ಸಹ-ಲೇಖಕರೂ ಕೂಡ ಹೌದು.

“ಕರ್ನಾಟಕ, ಕೇರಳ ಹಾಗೂ ತಮಿಳುನಾಡಿನ ಜೀವ ನದಿಯಾಗಿರುವ ಕಾವೇರಿಯಲ್ಲಿನ ಈ ಅಪರೂಪದ ಗೂನು ಬೆನ್ನಿನ ಮಹಶೀರ್ ಮೀನಿನ  ಭವಿಷ್ಯ ದಕ್ಷಿಣ ಭಾರತದ ಪಾಲುದಾರರ ಇಚ್ಛಾಶಕ್ತಿ ಹಾಗೂ ಸಹಕಾರದ ಮೇಲೆಯೇ ಸಂಪೂರ್ಣವಾಗಿ ಅವಲಂಬಿತವಾಗಿದೆ” ಎಂದು ಡಾ. ರಾಜೀವ್ ತಮ್ಮ ಮಾತನ್ನು ಮುಂದುವರೆಸುತ್ತಾರೆ.

"ನಾವು ಅಳಿವಿನಂಚಿನಲ್ಲಿರುವ ಪ್ರಭೇದಗಳ ಬಗ್ಗೆ ಚರ್ಚಿಸುವಾಗ ದೈತ್ಯ ಪಾಂಡಾ ಮತ್ತು ಬಂಗಾಳದ ಹುಲಿಗಳಂತಹ 'ಪ್ರಮುಖ' ಜಾತಿಗಳ ಬಗ್ಗೆಯೇ ಯೋಚಿಸುತ್ತೇವೆ. ಇವೆರಡನ್ನೂ ಸಹ ಪ್ರಸ್ತುತವಾಗಿ ಐ.ಯು.ಸಿ.ಎನ್. ನ ಪಟ್ಟಿಯಲ್ಲಿ 'ದುರ್ಬಲ' ಮತ್ತು 'ಅಪಾಯಕಾರಿ' ಎಂದು ಪರಿಗಣಿಸಲಾಗಿದೆ. ಆದರೆ ‘ಗೂನು ಬೆನ್ನಿನ ಮಹಶೀರ್ ಮೀನು’ ಇಂದು ಉಳಿದೆರಡು ಚಿರಪರಿಚಿತ ಜೀವಿಗಳಿಗಿಂತಲೂ ಆತಂಕಕಾರಿ ಸ್ಥಿತಿಯಲ್ಲಿದೆ. ಆದ್ದರಿಂದ ಈಗಾಗಲೆ ವೈಜ್ಞಾನಿಕ ಹೆಸರನ್ನು ನೀಡಲಾಗಿರುವ ಹಿನ್ನಲೆಯಲ್ಲಿ, ಅಧಿಕೃತವಾಗಿ ಈ ಮೀನನ್ನು ‘ಅಪಾಯಕಾರಿ ಸ್ಥಿತಿಯಲ್ಲಿರುವ ಜೀವಿ’ ಎಂದು ವರ್ಗೀಕರಿಸಬಹುದು. ಪರಿಣಾಮವಾಗಿ ಭವಿಷ್ಯದಲ್ಲಿ ಅದರ ಉಳಿಯುವಿಕೆಯನ್ನು ಖಚಿತಪಡಿಸಿಕೊಳ್ಳಲು ದೃಢವಾದ ಕ್ರಮಗಳನ್ನು ನಾವು ಕೈಗೊಳ್ಳಬಹುದು" ಎಂದು ಅಧ್ಯಯನದ ಪರಿಣಾಮಗಳ ಬಗ್ಗೆ ಆಡ್ರಿಯನ್ ವಿವರಿಸುತ್ತಾರೆ. 

Section: General, Science, Ecology, Deep-dive Source:
मुंबई Wednesday, 22 August, 2018 - 07:39

शहरात जागेसाठी वाढत्या मागणीमुळे नागरिकांना आसपासच्या परवडणार्‍या ग्रामीण क्षेत्रात स्थलांतरित व्हावे लागत आहे. ह्या क्षेत्रांना परि-शहरी क्षेत्र म्हणतात आणि तिथे ग्रामीण आणि शहरी घटकांचे मिश्रण असते. भारतीय तंत्रज्ञान संस्था, मुंबई ह्यांनी केलेल्या एका अभ्यासात असे दिसून आले आहे की मुंबईच्या आसपास असलेल्या परि-शहरी क्षेत्रात नैसर्गिक संसाधनांवर ताण पडतो आहे आणि उपजीविकेची साधने आता प्रामुख्याने अकृषि-क्षेत्रातील झाली आहेत.

योग्य नियोजन न करता परि-शहरे क्षेत्र विकसित झाली तर ते समस्यांना आमंत्रण देण्यासारखे आहे कारण त्यामुळे शहरी गरजा पूर्ण करण्यासाठी मोठ्या प्रमाणात कृषी क्षेत्र बदलते. शहरी भागातील अनियोजित, पसरलेल्या अनियंत्रित वाढीपेक्षा परि-शहरी क्षेत्र वेगळे असते कारण त्यात अजूनही मोकळी जमीन, शेती अशी काही ग्रामीण घटके असतात. परि-शहरी क्षेत्र विकसित होताना पाण्यासारख्या नैसर्गिक संसाधनांचा गैरवापर होतो, स्थानिक लोकांच्या उपजीविकेचे साधन बदलते, आणि पर्यावरणाचे नुकसान होते. या अभ्यासाचे मार्गदर्शक व स्थापत्य अभियांत्रिकी विभागाचे प्रमुख, प्राध्यापक टी आय एल्डो म्हणतात, "परि-शहरीकरणाचा अभ्यास फक्त शहरी व्यवस्थापन समस्यांचा एक भाग म्हणून नाही तर परि-शहरी क्षेत्रांच्या दृष्टिकोनातून झाला पाहिजे."

संशोधकांनी बृहन्मुंबईच्या परिघावरील चार गावांचा अभ्यास केला -- कर्जत उप-जिल्ह्यातील माणगाव तर्फ वसारे, मूळगाव तर्फ वसारे, कोंढाणे आणि साल्पे. २००१ आणि २०११ सालचे जनगणना अहवाल त्यांनी वापरले, आणि विशेष रूपाने निर्माण केलेली प्रश्नावली वापरुन ४० व्यक्तिंचे सर्वेक्षण केले. त्याचबरोबर त्यांनी गावातील प्रमुख व्यक्तिंबरोबर चर्चा करून गावातील लोकांचे तपशील आणि उपजीविकेची साधने,जमीन आणि पाण्याचा वापर इत्यादी विषय समजून घेतले.

अभ्यासात असे दिसून आले की २००१ साली २०% लोकांचे उपजीविकेचे मुख्य साधन शेती होते. पण २०११ सालपर्यंत फक्त ९% लोक शेती करत होते. वर्तमान काळात स्वल्प प्रमाणात शेती होते कारण शेतजमीन खाजगी कंपन्यांच्या ताब्यात आहे. जे शेतकरी स्वत:च्या जमिनीवर शेती करत होते किंवा इतरांच्या जमिनी कसत होते त्यांच्यावर पण दुष्प्रभाव झाला. ते आता विटांच्या भट्टीत काम करतात किंवा नदी खोर्‍यातून रेतीचे खनन करतात. जी जमीन पूर्वी सुपीक होती तिथे आता श्रीमंत लोकांचे फार्महाऊस, बंगले आणि मंगल कार्यालये बांधली आहेत.

अनेक बेकायदेशीर वीट भट्ट्या सुरू झाल्या आहेत. अभ्यासात असे दिसून आले की ह्या भट्ट्या अनौपचारिक रोजगार निर्माण करतात आणि त्याचबरोबर आसपासच्या वाढत्या बांधकामाला कच्चा माल पण पुरवतात. ह्या सर्व प्रक्रियेत पर्यावरण प्रदूषित होते. भट्ट्यांना अविरत पाणी पुरवठा आवश्यक असल्यामुळे परि-शहरी क्षेत्रातील नैसर्गिक संसाधनांवर मोठ्या प्रमाणात ताण पडतो.

वरील कारणांमुळे चारही परि-शहरी क्षेत्रात पाण्याची तीव्र टंचाई निर्माण होताना दिसते. ह्या भागातले वार्षिक पर्जन्यमान राष्ट्रीय सरासरीपेक्षा तिप्पट, म्हणजे ३६९१ मिमी असते. तरीही पावसाळा संपला की पाण्याची टंचाई सुरू होते. फार्महाऊस आणि हॉटेलमध्ये वैयक्तिक वापरासाठी किंवा आंब्यासारख्या फळबागेतील पिकांना पाणी देण्यासाठी खोदलेल्या कूप नलिकांमुळे भूजल पातळी खालावली आहे. गावकर्‍यांसाठी पाण्याचे मुख्य स्रोत असलेल्या उघड्या विहिरी आता कोरड्या पडल्या आहेत. फक्त शहरी गरजा पूर्ण करण्यासाठी पाण्याच्या प्रवाहाची दिशा बदलण्यात येते आणि बंधारे बांधण्यात येतात आणि त्यामुळे समस्या अधिक तीव्र होत आहे.

मग ही गावे स्वत:च्या हक्कांसाठी का लढत नाहीत? प्राध्यापक एल्डो ह्यांच्या मते, "विद्यमान स्थानिक स्वराज्य संस्था कमकुवत आहेत,व प्रत्यक्ष निर्णय घेताना सांविधिक संस्थांना डावलले जाते."ही परि-शहरे प्रमुख शहराच्या प्रशासकीय सीमांच्या बाहेर असल्यामुळे, अनेकदा प्रशासकीय गोंधळ होतो आणि मग आरोपप्रत्यारोप होऊ शकतात. आपल्याला हे सर्व घटक समजले तरच आपण त्यात काही तरी बदल करू शकतो.

आपली शहरे अतिजलद वेगाने विस्तारित होत असल्यामुळे परि-शहरीकरण टाळता येणार नाही. पण ह्या प्रक्रियेचे व्यवस्थापन अधिक चांगल्या पद्धतीने करता येईल आणि त्यासाठी पारंपारिक शहर-केन्द्रित धोरणांच्या ऐवजी इतर पर्याय शोधावे असे अभ्यासकांचे मत आहे. प्राध्यापक एल्डो ह्यांच्या मते,"शहर-केन्द्रित योजनांचा सगळ्यात मोठा तोटा म्हणजे त्यात गृहीत धरले जाते की शहरी समस्या सोडवल्या आणि जागेचे शहरी पद्धतीने नियोजन केले तर परि-शहरे अधिक चांगल्या प्रकारे संचालित करता येतील. खरं तर, ग्रामीण क्षेत्र आणि शहरांत अधिकार, परिस्थिती आणि सामर्थ्य ह्यातील भिन्नता कमी करण्यासाठी आपल्याकडे दीर्घकालीन आणि विकेन्द्रित यंत्रणा असायला हवी".

परि-शहरीकरणाच्या समस्येसाठी समाधान शोधायला भारत सरकारने राष्ट्रीय रर्बन मिशन स्थापित केले आहे. प्राध्यापक एल्डो सावधपणे आशावादी आहेत. ते म्हणतात, "मोठ्या प्रमाणात विकेंद्रीकरण आणि नैसर्गिक संसाधनांच्या व्यवस्थापनात नागरिकांना सहभागी करून घेण्याचे धोरण वापरणे नक्कीच योग्य दिशेने टाकलेले पाऊल असेल".

शहरांचा विस्तार होत राहणार आणि आपल्याला ते बदल दिसत राहणार. मात्र ह्या संक्रमणात आपण हरवून जायला नको.

Section: General, Science, Society, Deep-dive Source:
लखनऊ Wednesday, 22 August, 2018 - 07:26

अच्छे स्वस्थ्य के लिए शुद्ध पेय जल एक महत्वपूर्ण ज़रूरत है। अशुद्ध जल पीने से हैज़ा, दस्त, पेचीस, हेपेटाइटिस-ए, और टायफॉइड जैसी बीमारियाँ होती हैं। भारत जैसे देश में, जहाँ २१ प्रतिशत संक्रामक बीमारियाँ दूषित जल के कारण फैलती हैं और साफ-सुरक्षित पेय जल की अनुपलब्धता के कारण प्रतिदिन ५०० से ज़्यादा बच्चे ५ वर्ष की आयु के भीतर ही  दस्त  के शिकार हो जाते हैं, शुद्ध पेय जल उपलब्ध कराना सर्वोपरि आवश्यकता है। वैज्ञानिक तथा औद्योगिक अनुसंधान परिषद (सी.एस.आई.आर.) के भारतीय विषविज्ञान अनुसंधान संस्थान (सी.एस.आई.आर. - आई.आई.टी.आर.) ने एक यंत्र विकसित किया है जो शुद्ध पेय जल की समस्या को हल करने में महत्वपूर्ण योगदान करेगा।

बाज़ार में जल शुद्धिकरण यंत्र नया नहीं है। परन्तु, इनमें से कई या तो बहुत महंगे होते हैं जिसका भार हर व्यक्ति वहन नहीं कर सकता या फिर उनका रख-रखाव बहुत महंगा पड़ता है। सी.एस.आई.आर.-आई.आई.टी.आर. के शोधकर्ताओं द्वारा विकसित ओनीर नामक जल शुद्धिकरण यंत्र इन सबसे अलग है। यह एक इलेक्ट्रॉनिक यंत्र है जो सौर ऊर्जा से चलता है, और इससे प्राप्त एक लीटर शुद्ध पानी की लागत दो पैसे से भी कम आती है। जबकि अल्ट्रा वायलेट (यूवी) जल शुद्धिकरण यंत्र साफ दिखने वाले पानी में से सूक्ष्मजीवों का सफाया करते हैं, ओनीर खारे या गंदे पानी में से भी सूक्ष्मजीवों का सफाया करने में सक्षम है।

यह जल शुद्धिकरण यंत्र एनोडिक ऑक्सीकरण- ऑक्साइड फिल्म बनाने की एक विद्युतरासायनिक प्रक्रिया, के सिद्धांत पर काम करता है । सी.एस.आई.आर.-आई.आई.टी.आर. के निदेशक प्रोफेसर आलोक धवन का कहना है कि- “इस यंत्र में इस्तेमाल नवीन तकनीक से सभी रोग-जनक जीवों- वायरस, जीवाणु, फफूंद, प्रोटोज़ोआ और सिस्ट से छुटकारा पाया जा सकता है तथा यह तकनीक विश्व स्वास्थ्य संगठन (डब्ल्यू. एच. ओ.) और पर्यावरण संरक्षण एजेंसी (ई.पी.ए.) द्वारा पीने योग्य पानी के लिए निर्धारित राष्ट्रीय और अंतर्राष्ट्रीय मानकों के अनुसार समुदायों को सुरक्षित पेयजल उपलब्ध कराती है।”

ओनीर दो संस्करणों में उपलब्ध है - घरेलू और व्यावसायिक। घरेलू संस्करण ५ मिनट में १० लीटर पानी की आपूर्ति कर सकता है और व्यावसायिक संस्करण एक घंटे में ४५० लीटर पानी की आपूर्ति कर सकता है। इस यन्त्र के अनूठे  मॉड्यूलर बनावट के कारण इसमे परिवर्तन करके प्रतिदिन पाँच हज़ार से एक लाख लीटर तक पानी का शुद्धिकरण किया जा सकता है। क्योंकि यह यंत्र सौर ऊर्जा संचालित है, यह दूर-दराज़ के गांवों के रहवासियों जहाँ बिजली की समस्या है और फेरीवालों को साफ पेय जल उपलब्ध करा सकता है।

यह पहला ऐसा पानी शुद्धिकरण यंत्र है जिसका रख-रखाव न के बराबर है। प्रोफेसर धवन के अनुसार इस यंत्र में एक स्मार्ट व्यवस्था अंतर्निहित होती है जो इसके परिचालन के भिन्न चरण की तात्कालिक जानकारी देता है और इसमें सेल्फ-क्लीन व्यवस्था के साथ पानी भरने के लिए स्वचालित बटन भी है जो  निरंतर  शुद्धपेय जल उपलब्ध करता है। इसके अलावा इसमें पानी को छानने के लिए किसी झिल्ली की आवश्यकता नहीं होती और इसलिए बार-बार  झिल्ली बदलने की भी कोई आवश्यकता नहीं है। यदि पानी में उच्च स्तर के संपूर्ण विघटित ठोस (टी.डी.एस.) या अन्य रासायनिक प्रदूषक मौजूद हैं तो विशेष प्री-फिल्टर का उपयोग किया जा सकता है।

अन्य तकनीकों के मुकाबले ओनीर को इस तरह बनाया गया है कि पानी में आवश्यक खनिजों का संरक्षण हो सके। “रिवर्स ऑस्मोसिस (आर.ओ.) जल शुद्धिकरण के उपयोग से सम्बंधित एक सामान्य समस्या है कि शुद्धिकरण प्रक्रिया के दौरान ज़रूरी खनिजों का ह्रास हो जाता है। ओनीर की अनूठी कीटाणुरोधक प्रक्रिया आवश्यक प्राकृतिक खनिजों को बरकरार रखती है और इस प्रकार यह हमारे स्वास्थ और कल्याण के लिए फायदेमंद भी है”, ऐसा प्रोफेसर धवन ने कहा।

सी.एस.आई.आर.-आई.आई.टी.आर. के वैज्ञानिकों ने ओनीर का व्यावसायिक प्रतिरूप जारी किया है और कई अवसरों पर इसका सफलतापूर्वक परीक्षण भी किया है। वास्तव में सी.एस.आई.आर.-आई.आई.टी.आर. के स्टॉफ ओनीर पेय जल का नियमित इस्तेमाल करते हैं। सी.एस.आई.आर. स्पोर्ट्स मीट और लखनऊ के किसान मेले के दौरान ५ हज़ार से ज़्यादा प्रतिभागियों को इसी यंत्र से पीने का पानी उपलब्ध कराया गया था।

ओनीर सभी के लिए साफ पेय जल उपलब्ध कराने का वादा करता है और यह  स्वस्थ देश की ओर बढ़ता हुआ एक सही कदम है। तो हम कितनी जल्दी इस यंत्र को  बाज़ार में देख पाएंगे? प्रोफेसर धवन के कथनानुसार, सी.एस.आई.आर.- आई.आई.टी.आर. लोगों की प्रतिक्रिया प्राप्त करने के लिए पूरे लखनऊ में ५-६ प्रायोगिक इकाइयाँ लगाने की प्रक्रिया में है। यह तकनीक व्यावसायीकरण के लिए तैयार है और कई निजी कंपनियां इसमें अपनी दिलचस्पी ले रही हैं। 

Section: General, Science, Technology, Health, Deep-dive Source:
Mumbai Tuesday, 21 August, 2018 - 07:12

Graphene, a two-dimensional, sheet-like variant of carbon, is a much sought-after material in science and engineering. Scientists are not only trying to explore and exploit its properties but are also looking for efficient and cost-effective methods to produce it. In a recent study, Prof Rajiv Dusane and Dr Shilpa Ramakrishna from the Indian Institute of Technology Bombay (IIT Bombay) have devised a new method to grow nanographene films on a copper foil with the help of atomic hydrogen at relatively lower temperatures compared to conventional methods.

Since its first unambiguous synthesis and identification in 2004, graphene has been widely studied since it has exceptional mechanical and electrical properties. One of the primary techniques used to synthesize graphene is the chemical vapour deposition where a carbon-containing compound like methane is exposed to temperatures as high as 1000℃.  Due to the heat, the carbon atoms break free and get deposited on a substrate plate. Copper is mostly used as the substrate because of its desirable thermal properties.

However, a significant disadvantage of this method is that the substrate also needs to be maintained at high temperatures. "The high temperature does not allow the use of other types of materials as substrates. Also, processes involving high temperatures demand a high cost of instrumentation and maintenance," explains Dr Shilpa. But, bringing down the temperature is not an option because, at lower substrate temperatures, the deposit will remain as amorphous carbon and not crystallize into graphene.

Previous studies had reported the crucial role played by atomic hydrogen in the deposition of diamond films and polymeric films over a given substrate. Taking a cue, the researchers of this study, published in the journal Materials Chemistry and Physics, decided to employ a similar technique. Instead of setting a high temperature for the copper substrate, they kept it at 600℃ and placed tungsten filament heated to 2000℃ above it. They then passed methane gas through this assembly, which resulted in the deposition of a layer of amorphous carbon on the copper substrate. Hydrogen gas was then passed over the filament, where the hydrogen atoms split and interacted with the amorphous carbon, leading to its conversion into graphene.

The method proposed by the researchers is called 'hot wire chemical vapour deposition' and is better than traditional methods on many counts. Since the dissociation or splitting of the methane molecules is very efficient, the required concentration of gas compared to conventional methods is significantly less. Also, the heated filament consumes less power, thereby considerably reducing the otherwise high substrate temperature required for graphene growth. These factors, in turn, bring down the overall cost of production as well.

A nanoscale study of the produced graphene showed that it is possible to control the growth of graphene by varying the exposure time and concentration of hydrogen. This finding could help potential studies that explore the use of atomic hydrogen chemistry, instead of just substrate-carbon interaction, to tailor the properties of graphene film at the nanoscale.

In the future, Prof. Dusane and his team plan to devise a more comprehensive method for synthesising graphene. “Utilising the chemistry of atomic hydrogen, we plan to devise a further improved methodology to grow graphene at low temperature using hot wire chemical vapour process,” says Prof. Dusane.

Section: General, Science, Deep-dive Source:
Bengaluru Monday, 20 August, 2018 - 07:25

The Hindu epic Ramayana describes how the protagonist Rama, with help from an army of apes, builds a bridge from the peninsula of India to Sri Lanka, to free his wife Sita from the clutches of Ravana. While the existence of such a bridge is still subject to much debate, geological evidence suggests that a thirty-kilometre long 'bridge of the sea' did form a land connection between India and Sri Lanka not so long ago. In a recent study, researchers Aparna Lajmi and Rohini Bansal in Dr. Praveen Karanth's lab at Indian Institute of Science in collaboration with Dr. Varad Giri, have traced the trail of Indian geckos that were once believed to have crossed this bridge.

Peninsular India and Sri Lanka, which were land fragments that separated from Madagascar about 90 million years ago and merged with Asia, have shared a large part of their geological history. The first separation of India and Sri Lanka happened in the early Miocene era, roughly 15 million years ago. Since then, the two landmasses have reconnected and severed many times, most recently about 10,000 years ago, due to the rising sea levels. This separation has allowed animals in Sri Lanka to become unique and evolve independently, in a process called endemism.

In this study, published in the Zoological Journal of the Linnean Society, the researchers studied the dispersal patterns of the Indian endemic Hemidactylus geckos, or commonly called house geckos, to Sri Lanka, when the land bridge was above sea level. The study was supported by grants from the Department of Science and Technology, Government of India, and The Rufford Small Grants Foundation.

What makes studying the dispersions of geckos interesting? “Island systems provide an exciting setting to study lineage diversification of a species because they are an isolated landmass. However, even though it is an island, Sri Lanka’s intermittent connections with India provides an ideal system to study the role of dispersal in the formation of an island's biodiversity”, says Prof. Praveen Karanth from IISc and an author of the study, in an interview with Research Matters.

Existing research on dispersal patterns of geckos points to two different hypotheses—one, the repeated exchange of fauna between India and Sri Lanka, and two, the in situ formation of endemic new species of geckos in Sri Lanka. To study these hypotheses, the researchers chose the Hemidactylus gecko as they are endemic to the Indian subregion (peninsular India and Sri Lanka) and have more than 27 different species.

The researchers started off by analysing the genetic makeup of the geckos found in the Indian subregion and used their findings to construct an 'evolutionary tree'. The evolutionary tree provides information about the time when the first geckos crossed over from India to Sri Lanka via the sea bridge. Based on this analysis, the researchers then studied how speciation—the formation of a new species due to evolution over a long period—occurred, and reconstructed the historical area of the gecko’s distribution.

“The dispersals of these geckos occurred millions of years ago, and hence their impact on the ecosystem is difficult to access. However, this study and others indicate that the intermittent connection between India and Sri Lanka has had a profound impact on the island's biota”, says Prof. Karanth on whether the geckos crossing over into Sri Lanka affected the ecosystem of the island.

Out of the 27 species that are descendants of the Indian Hemidactylus gecko, the evolutionary tree showed three distinct groups. The first group consists of large geckos with smooth bodies, the second of small-bodied terrestrial geckos endemic to India and Pakistan, and the third, medium to large-sized geckos with rough, bumpy skin. They have dispersed to Sri Lanka several times, and some have now evolved to be endemic to the Sri Lankan ecosystem. The study suggests that the evolution of these species in Sri Lanka is a result of their separation from their Indian counterparts when the sea levels rose in the Miocene era.

The study also found that some gecko species like H. scabriceps (scaly gecko) and H. lankae (Sri Lankan leaf-toed gecko) that inhabit the semiarid open habitats survived in both India and Sri Lanka. The Indian subcontinent underwent a drastic change in vegetation during the Late Miocene era where some forests gave way to open grassland habitats. Although these changes caused the extinction of wetland adapted animals like caecilians and shield-tail snakes, those that were adapted to open habitats, like the Sitana lizards, survived and formed new species. The land bridge between India and Sri Lanka was re-established around this period, allowing for a faunal exchange.

Wet-zone gecko species like H. hunae (spotted giant gecko) and H. depressus (Sri Lankan leaf-nosed gecko) that are now endemic to Sri Lanka are thought to have colonised the country earlier, while the dry zone species appear to have colonized the island in more recently with the establishment of a drier haitat and the reconnection between India and Sri  Lanka roughly 5 to 10 million years ago in the late Miocene era. The results of the study show that multiple dispersals from peninsular India to Sri Lanka explain the pattern of distribution of the Hemidactylus geckos. These results support the hypothesis that Sri Lankan fauna is a subset of Indian fauna. However, unlike the other fauna of Sri Lanka like freshwater crabs, shrimp, tree frogs and caecilians, the geckos have not undergone in situ diversification. Also, there is no evidence of the Sri Lankan species dispersing back into India.

On the other hand, some gecko species like the H. frenatus (common house gecko), H. parvimaculatus (spotted house gecko) and H. leschenaultii (Leschenault's leaf-toed gecko),  found in both India and Sri Lanka, live in habitats influenced by human settlements and are commensals with humans. They derive some benefits from living near humans but don’t affect the human settlement or cause any harm. The researchers postulate that they might have dispersed to Sri Lanka very recently with the help of human transport—a hypothesis they plan to test in the future.

“A more detailed population genetic study of the dry zone and human commensal species needs to be undertaken. We plan to use population genetics approaches to study the origin and evolution of Sri Lankan commensals”, says Prof. Karanth, on the future directions of his research.

Section: General, Science, Ecology, Deep-dive Source:
Bombay Friday, 17 August, 2018 - 08:10

Studying cells grown in a lab, called cell cultures, is essential to our understanding of their growth and functioning in our body. A common cell culture used in such studies is called adherent cells, which require a substrate or a surface to grow on. The chosen substrate usually resembles the extracellular matrix—a group of molecules that surround and support the cell, giving it its shape and structure. In a recent study, researchers at the Indian Institute of Technology Bombay (IIT Bombay) have shown that cell density—the number of cells grown on a unit volume—can also influence the morphology and function of cells.

Adherent cells form ‘adhesion sites’, which are a set of localised contact points on the substrate, with the help of proteins called integrins. These integrins are connected to actin fibres of the cell's skeleton (cytoskeleton) via a complex group of molecules called focal adhesions. When a cell adheres to a substrate, mechanical stimuli are transmitted and converted to biochemical signals through the focal adhesions, and this is crucial for various cellular processes and functions.

In the current study, published in the journal Biomaterials Science, the researchers have observed the growth and cellular traction—the stress exerted by human mesenchymal stem cells—as it spreads on a polyacrylamide substrate. Human mesenchymal stem cells are adult stem cells that are adherent and grow into skeletal, cartilage or fat tissues, depending on the growth environment. The researchers show that not only the substrate stiffness but also the cell density can be tuned to monitor and control the morphology and function of a cell. The study was supported by fellowships from the Wellcome Trust-DBT India Alliance and InStem, Department of Biotechnology.

For their experiments, the researchers prepared polyacrylamide (PAA) gel of different stiffness, coated it with collagen, the protein found in our muscles, bones and skin, and added human mesenchymal stem cells to it. PAA acts as the substrate as it is inert and its stiffness can be controlled. The collagen layer provides the adhesive support to the mesenchymal cells. The researchers used different densities of the stem cells on substrates with different stiffness.

The study found that for a substrate with low stiffness and lesser cellular density, the cells did not spread and were seen to be circular in shape. However, when the cellular density or the substrate stiffness increased, a gradual change was observed. The cells on the substrate started developing directed protrusions and spread preferentially towards their neighbouring cells, reducing the distance between each other. They formed different patterns of strings, network and at sufficiently high density, a near complete monolayer. The individual cells no longer remained circular; instead, they were more polarised in shape.

On investigating further on the observed behaviour, the researchers found the formation of mature focal adhesions and thick actin fibres, indicating a high traction force. Generally, an increase in the cell traction is known to cause an increase in cell spreading, but this is known to occur only on a stiffer or rigid substrate. Here, even on a substrate with low stiffness, the traction force was seen when the cellular density was high. Thus, when the cell density is increased, a soft substrate behaved like a rigid one.

Interestingly, the researchers observed that cell shapes and cell traction in the soft substrate resembled those on the rigid surface. Since this phenomenon was only seen when there was a high cellular density, the clue seemed to lie in the neighbouring cells. Adherent cells can sense strain in the substrate caused by the nearby cells. Initially, the cells randomly spread on the substrate, but when under strain, they form focal adhesion at that site and spread preferentially towards it. If there are neighbouring cells and both the cells sense strain at the same place, the competing pull of the cells may result in stiffening the substrate locally. When such preferential spreading occurs, cells form a pattern over the substrate.

The study presents an intriguing observation related to a cell function called proliferation. Previous studies have shown that human mesenchymal cells grown on a soft substrate tend to remain inactive and dormant. However, the results of the current study point out that at high cellular densities, these cells grown on a soft substrate start proliferating and proceed with their cell cycle, turning the substrate rigid. Thus the cell density can be tuned to switch the cell function from a dormant state to active proliferation.

“Our findings indicate that closely spaced cells sense the tension caused by their neighbours and start spreading in response. In summary, cell crowding and the resultant increase in apparent stiffness due to cellular traction can override many of the known effects of the substrate stiffness on cellular morphology and functions”, observe the authors. Studies like this enhance our knowledge on the factors that affect the cell-matrix and might aid in developing better models for studies related to tissue development.

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