An investigation on the effect of photoperiod and temperature on vertebral band deposition in little skate Leucoraja erinacea
An investigation was undertaken to determine whether photoperiod or temperature have an effect on the timing of vertebral opaque–transluscent band-pair deposition in captive young-of-the-year (YOY) little skate Leucoraja erinacea. The experimental design consisted of a randomized complete block split plot design with two factors: temperature and light. Temperature was nested within light and therefore four variables were tested: 1) constant light, 2) constant temperature, 3) seasonal light and 4) seasonal temperature. For 18 months, L. erinacea experienced accelerated seasonal conditions of temperature and light to mimic 3 years of growth. This study provides primary and supporting evidence that seasonal photoperiod and temperature, respectively, have no effect on timing of vertebral band-pair deposition in captive L. erinacea. Vertebral analysis of surviving L. erinacea (n = 6, time = 18 months) showed that all produced 1–1·5 band pairs, while centrum edge analysis (n = 56) showed timing of winter and summer band deposition were similar regardless of treatment. The winter band (translucent) appeared in February 2007 and January 2008 while the summer band (opaque) showed up in July for both 2007 and 2008 and mimicked patterns observed in the wild. While temperature and photoperiod appear to have no effect on timing of band-pair deposition in YOY L. erinacea, other mechanisms which may influence band deposition should be investigated including the effect of food ration and the presence of a circa-annual rhythm and hormone secretion.
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