Four new crab species found in Kerala

T. Nandakumar, Thiruvananthapuram
The Hindu, October 25, 2015

Researchers at the Department of Aquatic Biology and Fisheries, University of Kerala, have reported the discovery of four new species of crab from the Kerala coast, highlighting the crustacean diversity in the State.

The discovery of three hermit crabs has been recorded as part of a collaborative research project by A. Biju Kumar, head of the department; R. Reshmi, research scholar, and Tomoyuki Komai of the Natural History Museum and Institute, Chiba, Japan. The findings have been published in Zootaxa, the international journal of taxonomy.

The first of the new hermit crab species named Paguristes luculentus was collected off the coast of Kollam. It represents the ninth of the genus known from Indian waters. The species name luculentus (meaning colourful) refers to the livid living colour of the crustacean.

The second species Diogenes canaliculatus is light brown or tan and named after the longitudinal furrows on the outer surface of the arm of the left chelate leg.

The narrow bodied animal lives inside a shell shaped like an elephant tusk. Both the hermit crabs belong to the family Diogenidae, which are left handed hermits because the left claw is larger.

Collected from Neendakara, Kollam, the third species Pagurus spinossior belongs to another hermit crab family Paguridae known as right handed crabs and is tan in colour. The name spinossior refers to the strong armature on the clawed legs of the species.

A new species of pinnotherid crab, Afropinnotheres ratnakara was found inside the brown mussel (Perna perna) at Kovalam. The species was named ratnakara which means Indian Ocean in Sanskrit, as the genus was reported for the first time from the Indian Ocean.

Ubiquitous animals

Hermit crabs are ubiquitous animals often not considered to be ‘true’ crabs as they lack an external shell on their soft abdomen which leaves them vulnerable to predators. To protect themselves, they live in abandoned gastropod (snail) shells and often select larger shells as they grow up. Their last two pairs of legs are small and modified and, along with their uropods (appendages at the end of the abdomen), are used to clamp onto the internal whorls of the shell.

More than 40 species of hermit crabs were documented from the Kerala coast during the research project.

The University of Kerala is finalising a memorandum of agreement with Prof. Peter Ng Kee Lin, Head of the Lee Kong Chian Natural History Museum, Singapore, for a detailed study of the biogeography of crustaceans of Indian coastal waters.