This study yielded 11 new species, 1 new genus and a rediscovery of freshwater crabs after over 100 years! An insight into the ecology and discovery of these remarkably beautiful species in the heart of the UNESCO biodiversity hotspot, the Western Ghats of India.
Two years of intensive fieldwork across the Western Ghats through the monsoon-drenched cloud forests spear-headed by Tejas Thackeray followed an equally labourious mountain of lab-work by Dr SK Pati has resulted in this research paper. 11 new species, 1 new genus and a rediscovery of a species of crab after over a century!
It was a thrilling experience to be part of the fieldwork across these incredible landscapes- to firsthand experience and see principles of ecology playing themselves out! Some of the crabs that you shall see below are highly endemic due to the sky island theory; found only on one mountain despite the mountain beside it- just about 300 meters as the crow flies with identical vegetation, slope, terrain, rainfall etc, did not bear even one specimen.
This is because for small creatures such as these crabs, the mountain that they are found on is akin to an island surrounded by an impassable ocean- an impenetrable geographical barrier. Something that they cannot cross over and hence, over several thousands of years they have been able to establish a population only on that one particular mountain and not on the mountain just a stoneâ€™s throw away! A textbook example of insular (or island) biogeography and allopatric speciation- of species evolving in geographically isolated habitats.
This study does not revolve around a charismatic carnivore however, these minute eight-legged jewels play just as important a role in our understanding of the natural world and all that surrounds us. Tejas suggests that by looking at how these freshwater crabs came to occupy the ecological niches across the varied landscapes could throw light on the age of the Western Ghats and offer a better understanding of the happenings of the past- like little reproducing time-capsules.
I distinctly recall one incident from the survey around Kokankada while we were ascending an unnamed mountain, searching for crabs when it the weather took a turn all of a sudden. It started pouring down relentlessly, the cold stinging pellets of rain lashed our faces, the clouds forming an opaque layer- reducing our visibility to a couple of meters. We were talking about the different colour morphs of Sahyadriana waghi that we had come across- the probable reason for this kind of intra-specific variation- one a phantom grey white while the other with a deep rust-orange. When, a langur gave out a series of alarm calls that reverberated in the yawning rock gorges below us- drawing our attention. As if on cue, the clouds lifted and on the rock in front of us, surrounded by the blooming purple karvi flowers (it blooms once in eight years) like a regal emperor stood (the then undescribed) S.wallacei, cocking its eye to one side and staring at us sideways.
The adaptation of these crabs to their unique habitats and niches are incredible; the hair-like appendages on the legs of the Sahyadrianas help obtain a better grip on overhanging slick wet rocks, the incredible dexterity and limb strength of the Ghatiana atropurpurea that help it navigate amongst the trees- also being able suspending its body by a single toe when trying to hide. The bright colours that serve as a warning to predators; better known as aposematism- although they have the opposite effect on Swapnil- who is one of the best spotters in the country!
Hope that you enjoy the few images below!
I am heading out to the Western Ghats in the next few hours so am unable to write more in detail or put up more photos- but shall do so as soon as I return! Cheers!
I can be contacted on firstname.lastname@example.org in the meanwhile.
All text and photographs by Arjun Kamdar