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Marine Ecology Progress Series

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MEPS 649:83-96 (2020)  -  DOI:

The relative influence of nature vs. nurture on the expression of circatidal rhythms in the American horseshoe crab Limulus polyphemus

Tyler N. Thomas1, Winsor H. Watson III2, Christopher C. Chabot1,*

1Department of Biological Sciences, Plymouth State University, Plymouth, NH 03264, USA
2Department of Biological Sciences, University of New Hampshire, Durham, NH 03823, USA
*Corresponding author:

ABSTRACT: The horseshoe crab Limulus polyphemus exhibits rhythmic locomotor behavior that is controlled by both internal clocks and external tidal cycles. Recent findings demonstrate that adult horseshoe crabs from a 2 tides d-1 environment usually express 2 bouts of activity d-1, while adults from areas with 1 dominant tide d-1, or with negligible tides (atidal), generally express 1 bout of activity d-1. Horseshoe crabs from these different environments are genetically distinct, so it is not known if these behavioral differences are driven by genetics or by the tides they experience early in life. To address this question, freshly spawned horseshoe crab eggs from populations that experience these 3 distinct environmental tidal regimes were reared in the laboratory under 1 of the above 3 artificial tidal conditions. Then the activity of individual larval and 2nd instar juveniles was recorded over 3 wk using video tracking software. Endogenous circatidal rhythms were present in most (88/108) of the freshly molted juveniles from all 3 populations, even when they were raised in atidal conditions, indicating a strong genetic influence. To our knowledge, this is the first demonstration of the presence of genetically driven endogenous circatidal rhythms in an individual juvenile marine organism. Nevertheless, the early environment was also capable of having an impact, because it significantly affected rhythm expression in crabs in the 1 tide d-1 population. Thus, overall, the tidal environment to which horseshoe crab eggs are exposed during development appears to have less of an influence than genetics on their expression of tidal rhythms of locomotion.

KEY WORDS: Circatidal · Circalunidian · Early environment · Limulus polyphemus · Horseshoe crabs · Biological clocks · Larvae

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Cite this article as: Thomas TN, Watson WH III, Chabot CC (2020) The relative influence of nature vs. nurture on the expression of circatidal rhythms in the American horseshoe crab Limulus polyphemus. Mar Ecol Prog Ser 649:83-96.

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