Larval release behaviors in the blue crab Callinectes sapidus: Role of chemical cues
Egg hatching by brachyuran crabs is often precisely timed relative to environmental cycles and may be controlled by the female, the developing embryos, or both. The current conceptual model for larval release in subtidal brachyuran crabs is that the exact time of release is controlled by the developing embryos. At the time of hatching, the eggs release pheromones that induce stereotypic larval release behaviors in ovigerous females consisting of rapid abdominal pumping. This behavior breaks open the eggs and results in synchronized hatching. To test this model, we examined the role of pheromone substances released by developing and hatching eggs in initiating this pumping behavior in ovigerous blue crabs Callinectes sapidus. Pumping behavior was used as a bioassay to determine if pumping activity changes with the developmental state of the eggs and to test the response of ovigerous crabs to (1) substances released by hatching eggs (hatch water), (2) substances present in homogenized eggs containing early- and late-stage embryos (homogenized egg water), and (3) substances released by developing eggs containing early- and late-stage embryos (egg conditioned water). Pumping activity associated with egg maintenance increased with embryo development. Pumping activity increased with increasing concentration of hatch water and the threshold concentrations for females possessing early- and late-stage eggs were similar. Water containing homogenized eggs also evoked larval release behaviors and response thresholds were the same for females exposed to early- and late-stage egg treatments. Egg conditioned water prepared from eggs containing late-stage embryos was more potent than water prepared from eggs with earlystage embryos. Collectively, these results support the model that larval release in C. sapidus is controlled by pheromones released from hatching eggs and indicate that (1) the responsiveness of ovigerous C. sapidus to the pheromones is relatively independent of the stage of embryo development, (2) homogenates of both early- and late-stage eggs contain similar pheromone concentrations, (3) pheromones are released during development and at the time of hatching, and (4) the concentration of pheromones released from developing eggs increases as the embryos mature. © 2002 Elsevier Science B.V. All rights reserved.
Tankersley, RA; Bullock, TM; Forward, RB; Rittschof, D
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