AB 17:119-128 (2012)  -  DOI: https://doi.org/10.3354/ab00467

ABSTRACT: The reproductive biology of Ophiocoma aethiops and O. alexandri was analyzed based on monthly time-series samples from May 2009 to April 2010 at Estacahuite Bay, Oaxaca,  in the Mexican tropical Pacific Ocean. We evaluated the relationship between the reproductive biology of both species and variations of sea-bottom temperature, salinity, pluvial precipitation, photoperiod (light hours) and chlorophyll. Sex ratio, gonadosomatic index (GSI), actual fecundity and oocyte size were determined. Monthly variations of the environmental factors were compared with variations of GSI. Both species are gonochoric ophiuroids and the ratio of males to females (1:1) was not significantly different throughout the year. There were significant differences in GSI values between the 2 species, but temporal variation patterns were similar. Gametogenesis showed synchrony among males and females and 4 stages were recognized for both sexes. Spawning occurred in females of O. aethiops from May to November and from April to December in O. alexandri. Main spawning for males of both species occurred from May to December, although there was always availability of mature spermatozoa. Mean oocyte size was 32 to 58 µm for O. alexandri and 47 to 63 µm for O. aethiops. Mean ± SD fecundity was 3.03 ± 1.72 million vitellogenic oocytes per female for O. aethiops and 1.61 ± 0.99 million for O. alexandri. The reproductive patterns of O. aethiops and O. alexandri are influenced by the local oceanic dynamics, as has been reported for other echinoderm species in the area, but they also have a high genetic (endogenous) element, because the observed patterns resemble those determined for the Panamian populations of these 2 species.

KEY WORDS: Echinoderms · Brittle stars · Ophiocoma · Reproductive cycle · Fecundity · Histology · Mexican Pacific · Environmental factors