ASSOCIATIONS 587 



pubescens is enveloped by a colonial anemone Epizoanthus, and the crab 

 is said eventually to dissolve the protective gastropod shell. Another 

 pagurid, Paguropsis typica, carries an anemone Anemonia mammilifera 

 directly on its back without making use of a shell (17). 



The necessity of some manner of protection or immunity towards the 

 nematocytes of the coelenterate is evident in commensal relationships of 

 the kind just described. In the cloak-anemone-hermit-crab association, 

 it appears that the blood of Eupagurus contains an antibody effective 

 against the toxins of Adamsia, which are fatal to other species of hermit 

 crabs (3). 



Commensalism with coelenterates involves a wide variety of marine 

 animals besides Crustacea. In coral reefs of the Indo-Pacific region perma- 



Fig. 14.4. Eupagurus prideauxi and its Commensal, 

 the Cloak Anemone Adamsia palliata 



The basal disc of the anemone is wrapped around the shell inhabited by the crab, and 

 as the latter grows, the anemone provides increased accommodation for it. 



nent associations are found between damsel-fishes (Pomacentridae) and 

 certain large actinians. Species of Amphiprion, for example, find shelter 

 among the stinging tentacles of sea-anemones (Stoichactis, Actinia). The 

 damsel-fish never ventures far from the host-anemone, and when disturbed 

 it may even retreat into the digestive cavity of the latter. A very close 

 association is involved in these cases, for the damsel-fish is never found 

 apart from the anemone, is dependent on it for protection and cares for 

 the anemone in various ways. There are indications that the damsel-fish 

 is not insensitive to the cnidoblasts of the anemone, but the latter, in 

 some way, becomes conditioned to the presence of the fish (34, 105). 



Various pelagic coelenterates harbour or shelter a variety of com- 

 mensals. Some Scyphomedusae are often accompanied by young fish: 

 Cyanea capillata by young whiting {Gadus merlangus), and Rhizostoma 

 cuvieri by Jack-fish {Trachurus trachurus) and hyperiid amphipods. These 

 animals swim underneath the jellyfish, where they are sheltered and pro- 



