Endogenous swimming rhythms in estuarine crab megalopae: implications for flood-tide transport


Journal Article

Up-estuary migration of crab larvae to adult habitats is thought to be accomplished by selective tidal transport in which late-stage larvae enter the water column on flood tides and remain on or near the bottom on ebb tides. This study measured endogenous rhythms in swimming by the last larval stage (megalopa) of blue crabs Callinectes sapidus and fiddler crabs Uca spp. Previous field studies found that megalopae of both species were only abundant in the estuarine water column on nocturnal rising tides. Megalopae were collected from the Newport River Estuary, North Carolina (34°41′N; 76°40′W) during August-September 1992 and swimming activity was recorded for 4.5 to 7 d under constant conditions with a video system. Rhythms exhibited by both genera in the laboratory were not identical to those recorded in the field. Uca spp. displayed a circatidal rhythm, with maximum swimming occurring near the time of high tide in the field. Rhythm amplitude increased when crushed oyster shells were present, which suggested that megalopae bury or cling to the substrate during quiescent periods. In contrast, C. sapidus had a circadian rhythm in which maximum swimming coincided with the day phase in the field. In most trials, the activity of blue crab megalopae was unrelated to the expected tidal cycle. It was concluded that a tidal rhythm in swimming was the behavioral basis of flood-tide transport for fiddler crab larvae. The endogenous rhythm in blue crabs does not participate in transport, which probably results from behavioral responses to environmental cues associated with flood tide. © 1994 Springer-Verlag.

Full Text

Duke Authors

Cited Authors

  • Tankersley, RA; Forward, RB

Published Date

  • February 1, 1994

Published In

Volume / Issue

  • 118 / 3

Start / End Page

  • 415 - 423

Electronic International Standard Serial Number (EISSN)

  • 1432-1793

International Standard Serial Number (ISSN)

  • 0025-3162

Digital Object Identifier (DOI)

  • 10.1007/BF00350298

Citation Source

  • Scopus