Abstract

The brown sea cucumber Isostichopus fuscus is highly prized and intensively fished, yet no studies of its reproductive cycle at its northernmost distribution site exist. To characterize its reproductive cycle, monthly surveys (Oct 2014-Dec 2016) that included gonad collection were conducted in 118 sites along the eastern coast of Baja California, including islands from Bahía San Luis Gonzaga (29o 49’ 14.18” N, 114 o 3’56.17” W) to the 28th parallel north. A total of 2 808 sea cucumber specimens were measured (mean length ± SD = 21.4 ± 6 cm) and weighed (375.6 ± 249 g). Seven hundred and seventeen organisms were dissected but only 553 gonads were suitable for processing through histological analysis to identify sex and developmental stage. Of these individuals, 224 were female, 162 were male, 157 were undifferentiated and 10 were hermaphrodites, resulting in a sex ratio that was significantly different from 1:1 (χ2 = 36.63, P = 0.03, df = 23). There was no statistical difference (p > 0.05) of either size or weight between males and females, but females were larger than males. The length-weight relationship observed was W = 0.18L2.4, r2 = 0.82, p <0.05 while the size-at-first-maturity was 16 cm. Five gonad stages were identified: 28% undifferentiated, 9% gametogenesis, 15% mature, 19% expulsion and 29% post-expulsion. The Oocyte Theoretical Diameter (OTD) was estimated by measuring the area of 10 291 oocytes, finding 2 307 individuals in oogenesis (mean ± SD of 65.3 ± 19.7 µm), 3 630 in maturity (66.0 ± 17.8 µm), 3 756 in spawning (73.8 ± 14.6 µm) and 868 in post-spawning (49.18 ± 20.7 µm). Modal progression analysis shows that oocytes increase 23% in size from oogenesis to maturity, and decrease 9%in size from maturity to spawning and, on average, oocytes are 72% smaller post-spawning that during spawning. Rev. Biol. Trop. 65(Suppl. 1): S180-S196. Epub 2017 November 01.

 
Keywords: reproduction, sea cucumber, Holothuroidea, oocyte diameter.