Factors Influencing Egg Extrusion in the American Lobster (Homarus americanus)

Abstract

American lobster (Homarus americanus) females characteristically extrude eggs in the summer of the year following a summer or autumn molt, but young females may extrude in the same year. Adult female lobsters were exposed to periods of 40, 80, or 120 d of short photophase (8 h light: 16 h dark) at different times during the molt cycle or as controls were kept under continuous long-day conditions (16 h light: 8 h dark). They were found to require 80 d of short photophase to complete primary vitellogenesis; they then completed secondary vitellogenesis and extruded following long day onset (LDO) only if the latter fell within ± 1400 dd6 (day-degrees above 6 °C) of the molt. The dependence of this latter relationship upon prior delayed extrusion and molting suggests that the decay in probability of LDO-elicited extrusion following the molt proceeds independently of the advance of the current molt cycle. The hypothesis is therefore rejected that the decay in extrusion potential following the molt is a result of increasing probability of interference from the oncoming premolt. Alternative hypotheses are discussed.