A PRELIMINARY STUDY ON CERTAIN ASPECTS OF THE BIOLOGY AND THE CULTURE OF PARACALANUS CRASSIROSTRIS DAHL (COPEPODA, CALANOIDA)

Abstract

1. The biological aspects of Paracalanus crassirostris Dahl studied include the external morphology, complete life history, distribution, some aspects of its ecology and its culture under laboratory conditions. 2. The seasonal study was carried out during the period from April l968 to March 1969 whilst the samples for the study of diurnal distribution were collected from 3rd to 4th August 1970. 3. The details of the external morphology and identification of P. crassirostris have been discussed. 4. P. crassirostris occurs commonly in the tropical and subtropical coastal waters of the Atlantic, Indian and Pacific Oceans, being more abundant in estuarine waters. 5. This copepod was found to be more abundant in Johore Straits than in Singapore Straits. 6. It occurs throughout the year in large numbers in Johore Straits forming about 29% of the copepod population. They were most abundant in May-June and November-February which were the spawning periods of this copepod. 7. The younger stages were near the surface in the day but were distributed in deeper water at night. The adult animals were found in deeper water during the day but ascended to the surface during the night. 8. The complete life history of this copepod has been mapped out. This includes the development of the egg, nauplius, copedid stages and the adult. The development from the egg to the adult stages takes about 10 days for the male but 12 days for the female. One complete generation is about 14 days. The life span for the male is about 15 days whilst for the female it is about 23 days. 9. The sex ratio among the adult stage is 3 females to 1 male. 10. The cultured animals were always smaller than the animals found grow1ing naturally in the sea.11. The culture or Paracalanus crassirostris showed that under laboratory conditions, they could survive and breed for 3 to 6 generations in 30 days to 90 days. Whilst this copepod can definitely be cultured in the laboratory, much more experimental work must be carried out to unravel all the factors which play a role in the successful culture. Among these factors are the techniques of handling these minute animals without damage to them, the control of the environmental conditions of the culture medium such as temperature and metabolic contaminants, the type of food to be supplied for the various stages of growth and the control of ciliates and bacteria in the medium.