Fisheries Laboratory Hiroshima University
Ocean Research Institute University of Tokyo
- 海の研究 = Umi no Kenkyu (Oceanography in Japan) (ISSN:21863105)
- vol.6, no.5, pp.299-320, 1997-10-05
The feeding ecology of marine pelagic copepods has been intensively studied since the 1910's. Recently, many new techniques, such as high-speed cinematography, deep-sea ROV, and SCUBA, have been introduced for direct observatios of their feeding behavior. These have clearly revealed that particle-feeders employ suspension feeding but not filter-feeding and that appendicularian houses are important food items for some pelagic calanoid, harpacticoid, and poecilostomatoid copepods. Particle-feeders commonly utilize microzooplankton such as ciliates and copepod nauplii and fecal pellets. Detritivory, strict selective predation, and gorging have been found exclusively in oceanic copepods. Five calanoid families Diaixidae, Parkiidae, Phaennidae, Scolecitrichidae, and Tharybidae with special sensory setae on the mouthparts and the poecilostomatoid Oncaea are considered to be adapted for feeding on detrital matter such as appendicularian houses. Some heterorhabdids probably inject a venom or anesthetic into prey animals to capture them. In the laboratory, predation on fish eggs and larvae by copepods, rejection of some dinoflagellates by calanoids, developmental inhibition of copepod eggs by feeding on some diatoms, and copepods' reactions to fecal pellets were demonstrated. Pelagic copepods constitute an assemblage of evolutionarily different groups. Among the 10 orders, calanoids supposedly first colonized the marine pelagic realm, and, at present, are most successfully adapted of any order to this environment by a wide variety of feeding mechanisms. They have developed a wide variety of feeding mechanisms. On the other hand, poecilostomatoids have secondarily become adapted to pelagic environments and are loosely associated with fish larvae and pelagic invertebrates, such as salps and appendicularians, for feeding. The calanoid family Heterorhabdidae consists of 2 particle-feeding, 3 carnivorous, and 2 intermediate genera. A phylogenetic analysis showed that the carnivores could have originated from the particle-feeders through the intermediate conditions, and that the mouthpart elements of the carnivores could be derived from those of the particle-feeders with modifications of the original elements and no addition of novel structures. Recent studies demonstrate that some copepods such as scolecitrichids and Oncaea can efficiently feed on nanoplankton trapped in appendicularian houses, and also suggest that suspension-feeders may transport diatom resting spores into the sea-bottom in the epipelagic zone and metals in the deep-sea bottoms through their feeding behavior, and that epipelagic carnivores may compete with fish larvae for copepod nauplii and dinoflagellates.