CLASSIFICATION OF EUPAGURUS (HERMIT CRAB)
KINGDOM :- ANIMALIA (Multicellular eukaryotic organisms)
PHYLUM :- ARTHROPODA (Jointed appendages.)
SUB-PHYLUM:- CRUSTACEA (Exoskeleton thick, antennae 2 pairs, jaws 3 pairs.)
CLASS :- MALACOSTRACA (Free-living Crustacea with compound eyes, biramous antennules, mandibles, 8 thoracic and 6 abdominal segments having appendages.)
ORDER :- DECAPODA (Carapace present; first three thoracic limbs from maxillipedes.)
FAMILY :- PAGURIDAE (Abdomen flexed.)
GENUS :- Eupagurus (The Hermit crab)
Cosmopolitan. It is found from Alaska to lower California and Main to Florida. At Mumbai and Goa beaches. Eupagurus is a very favourite sea-shore animal.
HABIT AND HABITAT
Eupagurus leads a commensal life. It occupies a gastropod shell and it adjusts in the coils of shell with appendages protruding.
GENERAL CHARACTERSTICS OF EUPAGURUS (HERMIT CRAB)
- Commonly known as Hermit-crab.
- Eupagurus (Hermit crab) is a peculiar crustacean having extreme modifications in order to adjust in the coils of molluscan shells. Modifications are as under :
- Body is reduced in varying degree and asymmetrical but shows usual divisions into head, thorax and abdomen.
- Carapace reduced and not fused at the sides with epistome. It covers head. Rostrum absent.
- Head contains antennules, antennae and stalked eyes. Thoracic appendages protrude through the opening of the shell. First thoracic leg is chelate and rest reduced. Right chelate leg is very large as compared to left and it acts as lid or operculum.
- Abdomen is asymmetrical, soft fleshy, elongated and twisted or bent under the thorax.
- Abdominal appendages of the right side absent while those of left side reduced. Sixth left abdominal appendages (uropod) adapted for holding the body in hollow objects.
- Seventh and eighth thoracic appendages are reduced and remain inside the mollusc shell.
- Uropods are hooked and notched in the shell.
Hermit crab inside the gastropod shell and sea anemone over the shell associate themselves to lead a commensal life. The hermit-crab by its appendages takes sea anemone to varied places for food and in tum sea-anemone protects itself as well as the crab by its stinging cells. When the growth of the body demands, the Eupagurus selects a new large shell and deserts the old one. There is no metabolic dependency in above association.
The animal has protruding thoracic appendages, from mollusc shell and all above characters hence it is Hermit-crab (Eupagurus).