In situ feeding habits of Oncaea (Copepoda: Poecilostomatoida) from the upper 250 m of the central red sea, with special reference to consumption of Appendicularian houses
1996
Ohtsuka, S. (Hiroshima Univ. (Japan)) | Boettger Schnack, R. | Okada, M. | Onbe, T.
Gut contents of 9 species and 4 forms of pelagic poecilostomatoid copepods of the genus Oncaea collected from the 0-250 m depth layer in the central Red Sea were examined with a differential interference and phase contrast microscope. Appendicularian houses were frequently detected in the guts irrespective of species, sex, time and depth of collection. Houses occurred on average more frequently in females (61%) than in males (42%), with Oncaea venusta f. typica and O. clevei showing the most extreme sex-related differences. Females of O. conifera, which is a strong vertical migrator, exhibited a corresponding daily feeding rhythm, with the highest feeding intensity during the night. Diatoms and unidentified minute particles were frequently found in the guts of all species, and these may have been derived indirectly from appendicularian houses or other detritus. Other zooplankters such as copepodids, copepod nauplii and chaetognaths were detected in the guts of relatively large species (0.7 mm in body length) and rarely in smaller ones (0.7 mm). The present and previous studies clearly reveal that attachment and feeding of both small and large species of Oncaea on appendicularian houses commonly occur in oligotrophic water in tropical and subtropical regions and in the deep seas. The ecological role of Oncaea in these waters is discussed in comparison to that of calanoids
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