Aquatic Sciences Meeting, Albuquerque 2001

SS39 Evolution in Aquatic Environments (Spatial and Temporal Connections)

Date: Monday, February 12, 2001, Time: 2:45:00 PM

Location: Dona Ana

Davidson, S, D, Graduate School of Oceanography - University of Rhode Island, Narragansett, USA, sarah@gso.uri.edu

AN ALTERNATIVE LIFE HISTORY RESPONSE TO THE PROBLEM OF TIME CONSTRAINTS IN THE ESTUARINE COPEPOD ACARTIA TONSA

The estuarine copepod Acartia tonsa occurs in Narragansett Bay, RI only during the warm-water months. Time-constraint research on terrestrial semelparous insects shows that females born late in the season are smaller at maturity than individuals born earlier. Fitness advantages of delaying maturation to attain large adult body size (increased fecundity, decreased predation) are overcome as the season progresses by the risk of not producing any offspring before the environment becomes inhospitable. Organisms maturing earlier in response to conditions signaling the season’s end are more likely to produce some offspring. Observations of lab-reared individual female Acartia tonsa suggest that they respond uniquely to the end of the season (as simulated by short photoperiod). Late season females mature at the same size as early season adults but in a contracted period of growth and development. Females therefore reproduce at a younger age in late season conditions. Contraction of total development period in A. tonsa is accomplished primarily during pre-metamorphic naupliar stages. This alternative life history response is consistent with other copepod research indicating that size and intermolt growth are rather inflexible.

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Aquatic Sciences Meeting, Albuquerque 2001

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