MUD-LOBSTERS OF SINGAPORE WITH SPECIAL REFERENCE TO THE GENUS UPOGEBIA

Abstract

Mud lobsters belonging to 3 genera, and 8 species were studied. These animals were collected from several beaches and offshore islands around Singapore. In addition to general collecting, sponges were collected and worn pieces of coral and coral boulders were also investigated.

The species collected were:- Thalassina anomala Callianassa maxima Upogebia (Upogebia) spinifrons Upogebia (Upogebia) sp.nov. Upogebia (Calliadne) ancylodactyla Upogebia (Calliadne) amboinensis Upogebia (Calliadne) hexaceras Upogebia (Calliadne) octoceras var. Each species shows a distinct habitat preference. T. anomala and Upogebia (U) sp.nov. are mangrove forms, Callianassa maxima burrows in sandy beaches, Upogebia (Calliadne) ancylodactyla inhabits worn coral boulders and the others are sponge dwellers. An intensive study was made of the new species including its feeding and burrowing behaviour. This animal burrows by means of its first and second pair of thoracic legs. Mud, is loosened by the chelae and carried in a mud-basket formed by the long setae on .the 1st and 2nd pair of legs. This animal is a filter feeder as indicated by the long setae on the first and second pairs of legs. Food currents are created by the beating of the pleopods. The setae are placed in such a way that the water strains from inside the mud basket out. Burrows of mud lobsters were very definite with very firm linings of fine mud. They were usually Y shaped, two branches of which had small openings. Burrows of the mangrove species were many branched. In the laboratory, glass tubings with both ends opened were used as substitute burrows. The animal holds itself in the burrow by pressing the top of the carapace firmly against the top of the burrow. The spines and tufts of hair on the rostrum and carapace hold the animal in position. Walking in the burrow is achieved by the third and fifth pair of thoracic legs. The fourth pair of thoracic legs were held up and outwards and act as balance organs. The animal defends itself by thrusting its chelipeds forwards with the chelae wide open, or it moves back in jerks by flapping the uropods. Mud lobsters hardly leave their burrows once established in them. In their burrows they are protected from great changes in salinity, pH and temperature. They are also well protected as their soft bodies make them highly vulnerable.