Resumen del producto

The reproductive cycles of marine invertebrates are regulated by endogenous (genetic origin) and exogenous factors (environmental changes). It has been demonstrated that in some organisms from the intertidal zone the photoperiod is a variable that triggers gametogenesis. Chiton virgulatus Sowerby, 1840, is an endemic intertidal species from the Mexican Pacific coast. It has a fishery potential, because Mexican chi­tons are used for handcrafts, for human consumption or as bait in lobster harvesting and other organisms. In Mexico, the administration or regulation of fisheries on benthic invertebrates, is partially based on the knowledge of the reproductive cycle. We studied the relationship between the reproductive cycle of C. virgulatus and photoperiods. Twenty-five adult chitons were collected monthly between September 2008 and September 2009. The gonads were embedded in paraffin, and 5 ?m thick sections were stained with hematoxylin and eosin. Four phases of gonad development were identified: undifferentiated, developing, ripeness and spawning; additionally the gonadosomatic index (GI) was calculated. Spawning occurred in two periods, the most intense from July to December, with the highest frequency in December (20%), and the second from February to March with a lower frequency (4%). The stages of development and undifferentiation were significantly associated (P <0.05) with photoperiod (Rs =0.49, Rs =0.34, respectively). In conclusion, the gonad development of C. virgulatus is strongly related to more enlightened days and gonadal differentiation is associated with shorter light days.

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