Last fortnight we read the exciting news about the five newly described species of crabs found in the forests of Maharashtra and Goa. Initially, I too was drawn into the semantic debate about the usage of the word ‘discovery’. That, more so, as I have pictures of some of these recently ‘discovered’ crabs taken in Ambolighat (near Sawantwadi), back in 2010. But, like most of my mega-fauna obsessed pals, I too didn’t dig deep enough to find out their scientific names or if taxonomic work had been undertaken. The obvious result was that even though we all technically knew about their existence and they walked around in plain sight, they were unknown to science as a distinct species.
So, automatically my nerdy curiosity pushed me to check if the crab diversity of Mumbai region has been documented. I pulled out a 2006 publication of the Zoological Suvey of India (ZSI), which described the invertebrate fauna of the Sanjay Gandhi National Park (SGNP). To my utter horror and disgust, there was one picture labelled as a ‘land crab’. Besides that there was zilch about these ecologically important crustaceans. My restlessness pushed me to pull out my copy of the 1974 Maharashtra State Gazetteer’s Fauna Volume. Thankfully, there was an entire chapter on terrestrial and freshwater invertebrates of Maharashtra (not including insects and spiders). But, just three species of crabs (Order Decapoda) found in Maharashtra were mentioned. The worst revelation was that there were only two sentences on the Wikipedia page describing the Family Gecarcinucidae, which includes 18 Genera and close to 300 species of all described freshwater crabs of the world.
The discovery of those five new species was slowly taking a different meaning for me. I had already spent 5-6 frustrating hours searching online for keys to identify the freshwater crabs of India. I pulled out all the freshwater crab pictures I had clicked in an effort of scientific identification. The keys I found made it obvious that the taxonomy of crabs is complicated. Various carapace features and the size of the male’s first pleopods (walking feet) are measured as the distinguishing features. Hence, either you have clear images or you need the specimen in your hand.
My images weren’t good enough for species identification, but they clearly showed that these amphibious crabs were as comfortable breathing on land with their psuedo-lungs, as they were in water with their gills. In fact, I remembered that I had often encountered crabs active at night (nocturnal) in paddy fields and on forest floors, either feeding on the roots of rice plants or rushing deep into burrows, dug with their chelipeds (pincers). Obviously, farmers hate them and engage the larger bull frogs to control them.
In and around Mumbai, I’ve seen brown, yellow, whitish and dark chocolate coloured freshwater crabs in streams at SGNP, Tungareshwar, Karnala, Tansa and even in Mulund Hills or inside Ismail Yusuf College.
These crabs walk tall with raised pincers when threatened and are opportunistic omnivores. Predators such as the common buzzard, kingfishers, jackals, otters and local tribal communities thrive on them.
Although, they have mastered the amphibious lifestyle many times over in the evolutionary time scale, their highly localised distribution and low fecundity (capacity to lay eggs) in comparison to their marine counterparts, has rendered them endangered. So, let’s help these Ferrari-eyed decapods continue their tip-toeing in our gurgling streams.
Write in to Anand at firstname.lastname@example.org