FEEDING IN MYODOCOPID OSTRACODS - FUNCTIONAL-MORPHOLOGY AND LABORATORY OBSERVATIONS FROM VIDEOS

High-resolution videos, scanning electron microscopy and histology wer e used to study the feeding mechanism of myodocopid ostracods from the Pacific Coast of Japan, as exemplified by Vargula hilgendorfii (Mulle r, 1890) and a few other cypridinid species. Ostracods observed in the laboratory were attracted to a wide spectrum of natural food sources, behaving as predators of living prey (e.g. polychaete annelids), as o pportunistic scavengers on dead animals (e.g. annelids, fishes, squid) , and also consuming artificial food. Food sources may be detected by chemoreception. The fourth limb (endopodites with strong sclerotized s etae) and the furcal lamellae (claws with teeth) act in coordination t o abrade and eventually tear open the protective integument of living/ dead prey such as annelids. The mandibular palps are used mainly to ho ld the food. Food sections and soft-body contents are transferred to t he mouth by the fourth limb (endopodial ''rake'') and fifth limb (exop odite with pectinate setae) and are passed to the oesophagus by the en dites (mandibles, fourth and fifth limbs). Food is subsequently pumped up to the stomach by peristaltic contractions of the oesophagus (ring muscles) and stored in the stomach pouch. The upper lip of biolumines cent (V. hilgendorfii) and non-bioluminescent species of Cypridinidae often contact food, suggesting that some of the glands housed in this organ may emit digestive enzymes prior to ingestion. Ostracods are abl e to ingest massive quantities of food within a few minutes and to sur vive starvation for several weeks. In V. hilgendorfii, the midgut is a huge sac-like organ with no partition and is lined with a single laye r of columnar epithelial cells. No differentiated hepatopancreas is pr esent. The cypridinid produces a single faecal pellet wrapped in a thi n reticulated, peritrophic membrane. Myodocopid ostracods exhibit a wi de range of feeding strategies (detritus-feeding, comb-feeding, scaven ging, predation, ectoparasitism) in both benthic and pelagic niches, a nd constitute a substantial source of food for many zooplankters. Adap tation of cypridinids to scavenging/predation is reflected in the morp hology of their furcae, mandibles, fourth and fifth limbs, and their d igestive system. Palaeontological data suggest that early Triassic cyp ridinids and possible late Ordovician myodocopids may have been carniv orous scavengers feeding on carcasses of cephalopods (ammonoids or ort hoconic nautiloids), thus playing the same role of ''recyclers'' as mo dern representatives of the group.