Named after the habitat from where it was found, Indosphenia kayalum is a new species of softshell clam discovered from Kochi’s kayal or backwaters.
The discovery, published in ZooKeys (an international, peer-reviewed scientific journal) last month, was made by a team which included scientists from the Cochin University of Science and Technology (Cusat).
“Enigmatic” clam
In 2016, one of Cusat’s researchers and co-authors of the new study, Philomina Joseph, collected some thin-shelled, fragile clams or kakka from the brackish waters of the Kochi backwaters. But back in the lab, the research team could not identify the clam from existing literature or descriptions.
To identify the “enigmatic” clam, the team studied its morphology in detail and compared its features with that of similar-looking softshell clams (of three genera, Sphenia , Corbula also called Potamocorbula , and Cuspidaria ) seen in the Indian subcontinent. They did this by also comparing museum specimens from the National Museum of Wales (Cardiff, the United Kingdom) and the Natural History Museum (London).
Morphological analyses under powerful microscopes revealed that their new find was distinct and therefore, a new species.
“We named it after kayal to make people aware about the ecological importance of our complex backwater ecosystems for conservation of our endemic fauna,” said S. Bijoy Nandan, a professor at Cusat and one of the scientists who led the study, apart from P. Graham Oliver (National Museum of Wales), a world authority on molluscs and Jayachandran P.R. (Cusat).
New genus
However, it was when they studied the morphology of the other species too for comparison that the scientists realised that all the Indian brackish water species assigned to one genus – Potamocorbula – in fact belong to the family, the Myidae, and not Corbulidae as is currently thought.
To confirm this, they also used genetic data of some of these species as well as that of the new clam they found in the Kochi backwaters. With this, the team reassigned species under three existing genera – Sphenia , Potamocorbula and Cuspidaria – to a new Indian genus, Indosphenia . The new clam species from Kochi also falls into this new genus.
The classification of clam species – many of which look very similar to each other – is a confusing field.
According to the authors, this is because H.B. Preston, a collector and shell dealer who discovered and reported many new clam species from across India, did not describe the morphology of the clam’s hinges, which is one of the distinguishing features for species identification.
Yet, taxonomy of these small estuarine and marine creatures is crucial because India supports extensive bivalve fisheries (mussels, oysters, and clams), with an estimated annual production of 84,483 tonnes, according to a report by the Central Marine Fisheries Research Institute.
Recently, the clam at a fishery in Kollam, which produces around 10,000 tonnes annually and earns over ₹10 crore for the country in foreign revenue, was reported as having been misidentified as short neck clam when it is actually Venus shell clam.
