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Food and trophic relationships of the developmental stages of marine copepods Euchaeta japonica marukawa and Calanus plumchrus marukawa Pandyan, Anna Soundram

Abstract

Studies of feeding of the life history stages of marine copepods Euchaeta japonica Marukawa and Calanus plumchrus Marukawa suggest that the first two naupliar stages of both species are non-feeding stages. Feeding starts with the third nauplius in both species. These and later stages feed readily on heat-killed, flagellates Dunaliella tertiolecta. The fifth and sixth nauplii of E. japonica and the fourth nauplius of C. plumchrus also feed on large diatoms; they were fed Ditylum brightwellii and Chaetoceros serpentrionalis, respectively. The sixth nauplius of both species, given a mixture of phytoplankton and zooplankton, feeds selectively on D. tertiolecta. In E. japonica copepodite stages one to six (female and male) are omnivorous, but food selectivity experiments suggest that copepodite stages one to six (female) are primarily carnivorous, whereas males (stage six) are primarily herbivorous. This difference in feeding habits accords with the morphology of the mouthparts. In C. plumchrus copepodites one to six (female) are morphologically adapted for a herbivorous diet, but copepodites three to six (female) are capable of feeding on zooplankton also. Copepodite stages three and five prefer zooplankton, whereas the older and younger stages prefer phytoplankton. Preference for the large-sized phytoplankton has been indicated in the feeding of copepodite stages of C. plumchrus both in a mixture of foods and in unialgal cultures. Temporal variation in feeding is conspicuous in copepodite stages of C. plumchrus, and is related to diel vertical distribution and availability of food. Copepodite stages of E. japonica show less pronounced temporal variation, and their feeding does not seem to be closely related to their vertical distribution. The quantity of food consumed by developmental stages of both species in the laboratory when compared with that available in the sea, suggests that the potential capacity for feeding by these animals is not usually reached in the sea.

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