THIRUVANANTHAPURAM: The sea off Kovalam coast is home to a rare crustacean - a crab which belongs to a genus that has never before been sighted in the Indian Ocean. Researchers at the Department of Aquatic Biology and Fisheries at Kerala University, who discovered it, have aptly named it Afropinnotheres Ratnakara, in which ‘Ratnakara’ means Indian Ocean in Sanskrit.
Though the department was also part of discovering three new new species of hermit crabs, this rare species steals the limelight. Afropinnotheres is a genus which was previously recorded in the Atlantic Ocean. “We are confused about finding it here. It could have been introduced by ballast water. Or may be, it could have evolved on its own,” said A Biju Kumar, head of the Department of Aquatic Biology and Fisheries.Pinnotherid crabs live commensally inside clams, mussels and such bivalve mollusks, benefiting from the protective shell. In this case, the crab was found inside ‘kallumekkai’ or brown mussel (Perna Perna).
Biju Kumar conducted the research in collaboration with Peter Ng Kee Lin, head of Lee Kong Chian Natural History Museum, Singapore. The department and Kerala University is finalising a memorandum of agreement with the Singapore expert for a detailed study on biogeography of crustaceans of Indian coastal waters. The three hermit crabs which were discovered are ‘Paguristes Luculentus’, ‘Diogenes Canaliculatus’ and ‘Pagurus Spinossior’. Specimens of these species were collected off Neendakara coast, in Kollam. The new species, which were discovered at a depth of 50 m, are normally not found on the coast.
The publication of the new species of hermit crabs were done as a collaborative research work of Biju Kumar and research scholar R Reshmi with Tomoyuki Komai, a hermit crab taxonomy expert at Natural History Museum and Institute, Chiba, Japan. “Before this study, the number of hermit crab species reported off Kerala coast was less than 10. But, our study revealed close to 40 species, including the three new species that we discovered,” says Biju Kumar. The research papers appeared in the international journal of taxonomy, Zootaxa.