Zeng, Chaoshu, and Naylor, Ernest (1996) Synchronization of endogenous tidal vertical migration rhythms in laboratory-hatched larvae of the crab Carcinus maenas. Journal of Experimental Marine Biology and Ecology, 198 (2). pp. 269-289.

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Abstract

Previous studies showed that freshly collected zoea-1 larvae of the shore crab Carcinus maenas from coastal waters possessed endogenous circatidal vertical migration rhythms. Present experiments demonstrate that zoea-1 larvae released by crabs which extruded eggs in the field but were then kept in laboratory constant conditions since collection, also exhibited endogenous circatidal vertical migration rhythms. Such rhythms were shown by newly hatched larvae from nearly all of 50 females which released larvae in the laboratory, some of which had carried eggs in the laboratory for up to 3–4 months. Thus, since entrainment by tidal variables could not have occurred during embryonic development in these cases, other synchronising factors must set the phase of the larval circatidal rhythms. Present results suggest that the hatching process itself is the main synchroniser; upward swimming occurred just after hatching and at 12.4 h intervals thereafter. This is consistent with previous observations of peak hatching in Carcinus primarily around nocturnal high tide, with larvae in the field exhibiting tidal vertical migration rhythms of ebb-phased upward swimming associated with dispersal during ebbing tides. The results appear to be the first to characterize a synchroniser for tidal swimming rhythms of planktonic larvae and to provide experimental evidence that the hatching process can serve as the synchroniser for a larval swimming rhythm

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