Body size and egg production in the marine copepod Acartia hudsonica during a winter‐spring diatom bloom in Narragansett Bay

Abstract

Seasonal changes in size and egg production in the copepod Acartia hudsonica were investigated during the 1984 winter-spring bloom in Narragansett Bay. Possible food limitation was investigated lhrough comparisons of short-term weight change and egg production rate in copepods incubated in ambient Narragansett Bay water and in bay water enriched with cultured algae. A preliminary experiment showed that egg production responded in ~24 h to a change in food availability at 4"C-the coldest experimental temperature. Food was not limiting in February-April, but mild food limitation developed in May-June, affecting body weight more than egg production. These results contrast with strong food limitation of the summer dominant, Acar;!ia tonsa. Empirical regressions describe relationships between A. hudsonica length and weight, and egg production in relation to temperature, weight, and field Chl a.A separate study suggested that A. hudsonica adults were dominated by changing age groups lduring the winter-spring period. Present results indicate that the adult age distribution affects mean body weight, condition factor, and egg production rate, especially in April and May when the autumn-hatched, over-wintering copepods are being replaced by newly matured, winter-spring hatched adults.

Food availability effects on reproductive strategy: the case of Acartia tonsa (Copepoda: Calanoida)

“…This could be due to loss of female reproductive ability with age, as observed in other studies (e.g. Durbin et al 1992). No variation in egg size was ob served between the different food treatments in this study ( Fig.…”

“…They caused the total biochemical composition (μg) per egg produced by females held at higher food concentration to be significantly less than those produced by food-limited females. To the extent that inadequate food availability is a feature of the natural environments of animals (Bellantoni & Peterson 1987, Durbin et al 1992, it may be that this was a consequence of Acartia's reproductive strategy under food-limited conditions.…”

“…As has been done for other copepod species (e.g. Guisande & Harris 1995), the effect of low food conditions on the biochemical composition of A. tonsa eggs also needs to be investigated because low food conditions are a feature of the natural environments of the species (Bellantoni & Peterson 1987, Durbin et al 1992.…”

Effects of temperature and food abundance on grazing and short‐term weight change in the marine copepod Acartia hudsonica

“…Maximal daily ration (% body C d-l) of adult female Acartia hudsonica compared with estimated maximal daily growth rate of copcpodite stages Cl-C5. Dry weight data from preserved A. hudsonica collected at the same locality in 1976; weights corrected for estimated 29.5% weight loss in Formalin (Durbin and Durbin 1978). Development time (0, d) from egg to adult female as a function of temperature (T, "C) was estimated from several sources (Landry 1975a,b; where D = 1,288 (T + 2.327)-*.4774, and duration of Cl-C5 = 0.3290 (Landry 1975b).…”

“…Comparisons of the critical concentration (C,) for Acartia hudsonica fed Thalassiosira constricta at four temperatures (heavy lines) with total and > lokm C concentrations in Narragansett Bay during winter-spring 1984. C concentrations estimated from Chl a, assurning C : Chl a = 60 (Durbin et al 1975). physiological condition: Cowles et al 1988;Kiorboe 1989).…”