An insight into the newly discovered crabs of Western Ghats; read more to see our journey to discovering these incredibly diverse and distinct species; such as the largely arboreal purple tree crabs and the electric pink and vermillion crabs found in laterite crevasses on a windy plateau!
A NEW DISCOVERY!
The first step to saving something is knowing about its existence.
The search for a species new to science, the quest to uncover the hidden complexities of the natural world, to be privy to the rarest of the rare is an extremely fulfilling journey. There is a small amount of adrenaline spurting through your body with each rock you upturn, each tree-hole you creep into, each stream that you splash through. The verdant green foliage of the flora revitalized by the monsoon play a game of hide-and-seek with the clouds, at times dropping the visibility to less than three metres!
Our task was out of a story-book; tramp through the dense rainforests of the Western Ghats and collect specimen and ecological data on the undiscovered species of crabs that dwell exclusively here- nowhere else on the planet. Spearheaded by Tejas, who has a sharp eye for these eight-legged (or ten-legged if you include the pincers/chelipeds- also earning them the title of ‘decapods’) creatures, our team comprised a few local individuals without whose traditional ecological knowledge we wouldn’t have been able to do a fraction of the work that we have.
While exploring the laterite rock formations on the super windy Chakul plateau, we came across an electric pink crab with bright vermillion legs nestled in a tiny crevasse filled with water. Coaxing it out with a blade of grass, we were stunned by the sheer riot of colours! This was a textbook example of aposematism; which refers to a set of anti-predator adaptations in the form of a bright warning colouration, warning potential predators that the animal is unpalatable. Similar to how the toadstool mushroom’s bright red and white colouration deters predators and reflects its inedibility.
I quickly fired off a few frames of this crab in its natural habitat before the roaring rains and blanket of fog cloaked us. Pranay on the west side shouted across the plateau saying that he had spotted another two as well. Tejas had his hands full with a juvenile and an adult male while Swapnil was all over the rocky outcrop collecting them in an empty Eclairs plastic box. We collected as conservatively as possible- a species as highly endemic as this was already under so much pressure, science should be the last to make a dent in their population. Back in Pune, Dr Pati spearheaded the lab work and spent long hours toiling and studying these specimen in his laboratory.
Next up we came across this resplendent purple crab nestled deep inside a tree hole where the rain water had collected. When I reached out to catch it, it scurried right around and up the bark of the tree with great ease and dexterity, much to my surprise. Although we had read some reports and surveys (from the early 1900’s by British explorers and taxonomists) about arboreal freshwater crabs, I hadn’t thought that they would be so well adapted to life on trees! Although a majority of all these purple crustaceans were found on trees we also found a few individuals along small streams. Anecdotal references suggest that these crabs are known to devour roadkilled snails.
One of the most interesting species that was discovered and described in this paper was Gubernatoriana thackerayi from Raghuvir Ghat. The striking species was found to be abundant on a short stretch along the winding slopes of the mountain but only the stretch of a few kilometres long. We scoured the wet slopes which were identical and contiguous with the ones on which these were found but to no avail. We couldn’t spot even one G. thackerayi before or after this stretch. I do not know whether it has anything to do with the weather conditions/ which direction the slope was facing/ direction of rain or simply our detection abilities; a more comprehensive study on these lines would no doubt be of great value in understanding the ecology of these species.
As the image below further illustrates, small congregations of G. thackerayi were also observed near some rocky crevasses which had a mix of females and males. It would be thoroughly interesting to understand the ecology of these incredibly rare and geographically restricted species especially in light of the sky island theory.
The crabs of the genus Gubernatoriana have these hairlike appendages on their legs- they fall under the category of Gecarcinucidae crabs and are found in freshwater.
All images and text by Arjun Kamdar
Read the abstract of the research paper here or access the full text here
Some media coverage:
The Better India,
The Hindu, Zootaxa,
The Free Press Journal,
Awe of Nature,
Ministry of Environment and Forests- Govt. of India