A study on the reproduction of
M. laciniatus in Lake La Caldera during the ice-free period of the years 1975, 1976 and 1977 has been carried out.
Values obtained as to sex ratio, production of spermatophores and eggs as well as fecundity and reproductive rates have allowed us to establish two well-differentiated periods in the breeding season of the population:
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A first period of maximum reproductive activity, at the beginning of the breeding season (before freezing of the lake), characterized by more males than females, a high rate of production of spermatophores and, generally, a low production of eggs and a low reproductive rate.
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A later period, following the thaw of the lake, and in which the population is composed mainly of nauplii and copepodids. Females dominate over males. Reproductive activity measured by the ratios of spermatophores per male and spermatophores per female is very limited. Conversely, high production of eggs and a high reproductive rate (most females are ovigerous) is observed.
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Mechanisms which determine both periods and their possible adaptive value, are discussed.
Keywords zooplankton - Calanoida - fecundity - sex ratio - reproductive rate
This research is a part of a Ph.D. Thesis submitted in fulfillment of the requirements for Doctor in Biology (University of Granada, Spain, April, 1981).