ON THE FEEDING AND COMPARATIVE BIOLOGY OF IRON IN COELENTERATE-ASSOCIATED GAMMARIDEAN AMPHIPODA (CRUSTACEA) FROM N NORWAY

Data are presented on the morphology of the mandible, morphometry of t he stomach, composition of stomach contents, fine structure of the ven tral caeca, and concentration of trace metals (Fe, Cu, Zn, Cd, Mn) in three species of coelenterophagous amphipod: Andaniexis sp. L (Stegoce phalidae), Stenothoe brevicomis G.O. Sars (Stenothoidae) and Onisimus normani G.O. Sars (Lysianassidae) collected from sites off Tromso, N. Norway. Andaniexis sp. L. has a blade-like incisor and highly distensi ble stomach compatible with functioning ecologically as a gluttonous b atch processor of soft food. Stomachs in animals of this species from one site contained nematocyst-bearing soft tissue of coelenterate orig in (identity not established) and sand grains, together with occasiona l polychaete remains. Andaniexis sp. L. from two sites differed in ter ms of their gut fullness and contribution of coelenterate material to the diet. Octahedral crystals of ferritin were variably present in cel ls of the ventral caeca; these crystals being a typical feature of the Fe detoxification system of stegocephalid amphipods. The Fe, Cu and Z n concentrations of Andaniexis sp. L., however, did not differ between sites. Stenothoe brevicomis also has a well developed, cutting inciso r. This species, though, has a small stomach, compatible with its cont inuous association with its host sea anemone [Actinostola callosa (Ver rill)]. Analysis of stomach contents showed that it can consume the te ntacular tissue of Actinostola callosa. Onisimus normani, also has a b lade-like incisor. It lives within the enteron of sea anemones (Actino stola callosa, Bolocera tuediae) and consumes mesenterial tissue. Alth ough both Stenothoe brevicomis and Onisimus normani proved to have Fe concentrations which were no different from those in Andaniexis sp. L. , only the last-mentioned species exhibited ferritin crystals. The rea son for this difference in Fe handling strategy is presently unclear a nd may require knowledge of the Fe challenge posed by the unknown food organism of Andaniexis sp. L. in explanation.