Are foraminifers (Protozoa) important food for small isopods (Crustacea) in the deep sea?

Gut contents of three small (<6mm) species of munnopsid asellote isopod cru staceans (Eckinozone arctica, Ilyarachna bergendali and I. touleivi) from b athyal depths in the Nordic Seas were examined. The species feed mainly on benthic foraminifers, and their gut contents reflect the functional capabil ity of the mouthparts in partitioning the food. Fragments of small and frag ile calcareous foraminifer protozoans and small hard agglutinating foramini fers were most important in the guts of Echinozone arctica, which has round ed mandibular molar process, suited for crunching the foraminifers. Dark- a nd light-gray stercomata (foraminifer fecal pellets) from soft agglutinatin g foraminifers were most important in the guts of Ilyarachna bergendali, wh ose molar process has a wide crunching cusp and a sharp cutting edge. The g ut contents of Ilyarachna torleivi were similar to the contents of I. berge ndali, but differed somewhat from those of E. arctica. The results indicate that foraminiferivory may be common among small munnopsid asellote isopods and that the isopods may specialize in certain foraminifer species or gene ra. The strength of the foraminifer test map be an important aid against pr edation. This study indicates that small, yet poorly known, soft-shelled an d agglutinating foraminifers with a low nutritional value may be important as food for deep-water isopods and that foraminifers may be an important li nk between phytodetritus and the macrofauna. (C) 2000 Elsevier Science Ltd. All rights reserved.