On an anomaly in the cheliped of the portunid crab, Portunus pelagicus (Linnaeus)

Abstract

Portunus pelagicus is the dominant species and contributes substantially to the crab fishery along the Palk Bay and Gulf of Mannar coasts in the vicinity of Mandapam. On 23rd February 1966, a male specimen of this species with the carapace measuring 59 mm. in length and 132 mm. in breadth which had two additional dactyli on the left cheliped (Fig. 1) was collected from the gill net (Nandu valai) catches from Gulf of Mannar landed near the jetty of the Central Marine Fisheries Research Institute. Such an anomalous condition of the cheliped which appears to be rare has not been reported hitherto in this species and therefore a brief description is given below. The right cheliped of the specimen was unfortunately broken before collection.