Observations on egg production rates and seasonal changes in the internal morphology of Mediterranean populations of Acartia clausi and Centropages typicus
- 209 Downloads
Egg production rates in wild populations of Acartia clausi and Centropages typicus, sampled biweekly in the Gulf of Naples from October 1985 to July 1987, showed marked seasonal fluctuations with maximum values in early spring that preceeded the annual maxima for adult female densities in summer. A positive correlation between chlorophyll a concentrations and egg production was evident only during the early spring phytoplankton bloom. A strong diminution in egg deposition occurred later in spring and continued throughout the summer notwithstanding high chlorophyll concentrations. In winter, when population abundances for adult females were lowest, egg production rates were always higher than in summer. Differences in egg production rates coincided with pronounced morphological changes between summer and winter populations of both species. The most striking of these changes consisted, in winter, in the presence of a dark brown fluid-like mass of granular material that seemed to freely bathe the gonads. The presence of this substance only during periods of elevated egg production suggests that it may enhance egg production rates when the adult population reaches minimum annual levels. Such a mechanism of self-regulation may operate to dampen the effects of environmental variability thereby contributing to maintain a ‘conservative’ structure in coastal copepod communities.
Key wordszooplankton copepods seasonal cycles reproduction
Unable to display preview. Download preview PDF.
- Bagnara, J. T. and M. E. Hadley, 1973. Chromatophores and color change. Prentice-Hall Inc., New Jersey, 202 pp.Google Scholar
- Gaudy, R., 1984. Biological cycle of Centropages typicus in the north-western Mediterranean neritic waters. Crustaceana suppl. 7: 200–213.Google Scholar
- Marshall, S. M. and A. P. Orr, 1955. The Biology of a Marine Copepod, Calanus finmarchicus (Gunnerus). Oliver and Boyd, Edinburgh. 188 pp.Google Scholar
- Scotto di Carlo, B. and A. Ianora, 1983. Standing stocks and species composition of Mediterranean zooplankton. In G. C. Carrada, T. S. Hopkins, Lj. Jeftic and S. Morcos (eds), Quantitative Analysis and Simulation of Mediterranean Ecosystems: The Gulf of Naples, a Case Study. Unesco Rep. Mar. Sci. 20: 59–69.Google Scholar
- Scotto di Carlo, B., C. R. Tomas, A. Ianora, D. Marino, M. G. Mazzocchi, M. Montresor, L. Petrillo, M. Ribera d’Alcalà, V. Saggiomo and A. Zingone, 1985. Uno studio integrato dell’ecosistema pelagico costiero del Golfo di Napoli. Nova Thalassia 7: 99–128.Google Scholar