Foregut morphology and feeding strategies in the syncarid malacostracan Anaspides tasmaniae: Correlating structure and function

Abstract

The foregut in malacostracan crustaceans is an ectodermally derived structure that shows morphological variation among taxa. Foregut morphology was studied in a syncarid, Anaspides tasmaniae, with the dual aims of describing the structure and of elucidating similarities and differences between A. tasmaniae and other malacostracans. The feeding habits of A. tasmaniae were also studied to correlate structure and function. The feeding strategy adopted by A, tasmaniae, predominantly detritivory, but preying occasionally on large food items, may be influenced by constraints of the morphology of the foregut. Scanning electron microscopy and conventional histological techniques revealed that the foregut of A. tasmaniae lacks ossicles and that internal skeletal elements are fashioned from invaginations of the external wall. These internal elements, which direct food particles and act as sieves, are densely setose. There is no evidence of calcification nor of the ossicles that characterize many decapod foreguts. The musculature is simple and acts principally to squeeze the entire foregut rather than to cause discrete movements of individual skeletal elements. The foregut of A. tasmaniae is not easily compared to the highly modified foreguts of decapods, but it shows many similarities to the foreguts of nondecapod taxa.