FOREGUT MORPHOLOGY AND FEEDING STRATEGIES IN THE SYNCARID MALACOSTRACAN ANASPIDES TASMANIAE - CORRELATING STRUCTURE AND FUNCTION

The foregut in malacostracan crustaceans is an ectodermally derived st ructure that shows morphological variation among taxa. Foregut morphol ogy was studied in a syncarid, Anaspides tasmaniae, with the dual aims of describing the structure and of elucidating similarities and diffe rences between A. tasmaniae and other malacostracans. The feeding habi ts of A. tasmaniae were also studied to correlate structure and functi on. The feeding strategy adopted by A. tasmaniae, predominantly detrit ivory, but preying occasionally on large food items, may be influenced by constraints of the morphology of the foregut. Scanning electron mi croscopy and conventional histological techniques revealed that the fo regut of A. tasmaniae lacks ossicles and that internal skeletal elemen ts are fashioned from invaginations of the external wall. These intern al elements, which direct food particles and act as sieves, are densel y setose. There is no evidence of calcification nor of the ossicles th at characterize many decapod foreguts. The musculature is simple and a cts principally to squeeze the entire foregut rather than to cause dis crete movements of individual skeletal elements. The foregut of A. tas maniae is not easily compared to the highly modified foreguts of decap ods, but it shows many similarities to the foreguts of nondecapod taxa .