Abstract
This study analyzed the reproductive cycle of Chiton virgulatus and its relationship with air temperature (AT) sea and surface temperature (SST), photoperiod, and tidal cycle (TC) in Bahía de La Paz, in the coast of the Gulf of California. Monthly samples were collected from September 2008 to September 2009. The parameters recorded included total length, total weight, and gonad weight of each organism; the gonad was processed using a histological technique, and the gonadal index and length at first maturity (L50) were estimated. C. virgulatus displays partial spawning with a reproductive peak in summer and autumn (July to December). The frequency of ripe organisms was associated with rises in SST (30.6 ºC), AT (29.9 ºC), and TC (68 cm, high tidal), while photoperiod (longer days) regulated the frequency of developing organisms. The length at first maturity was 29.7 mm. Chiton virgulatus is a polyplacophoran species in which high temperatures and high tides influence reproductive timing, while an increase in daylight boosts gonad development.
Highlights
Two polyplacophoran species, Chiton articulatus (Sowerby in Broderip and Sowerby, 1832) and Stenoplax magdalenensis (Hinds, 1845), are exploited intensively and with no restriction throughout their distribution range along the Mexican Pacific coast for use as human food, as bait for lobster fishing, and for manufacturing handicrafts (Ríos-Jara et al 2006)
The anatomical structure of the gonad showed features similar to those already described for other chiton species, including Onithochiton quercinus, Chiton pelliserpentis, Plaxiphora paeteliana, C. articulatus, and Chiton albolineatus (Sakker 1984, Avila-Poveda & AbadíaChanona 2013)
The sex ratio was 1:1 throughout the year. This differs from what has been reported for other polyplacophoran species, including Acanthopleura granulata and Chiton tuberculatus (Glynn 1970), Chiton cumingsii (Ishiyama 1995, Sotil 2004), and A. gemmata (Barbosa et al 2009), in which the sex ratio is biased towards males
Summary
Chiton articulatus (Sowerby in Broderip and Sowerby, 1832) and Stenoplax magdalenensis (Hinds, 1845), are exploited intensively and with no restriction throughout their distribution range along the Mexican Pacific coast for use as human food, as bait for lobster fishing, and for manufacturing handicrafts (Ríos-Jara et al 2006). Chiton virgulatus Sowerby II, 1840 is a species endemic to the coasts of the Gulf of California (Gonzalez 1993), for which no studies addressing its abundance are available. This species may be a resource with fishery potential. The existing studies on C. virgulatus describe the oogenesis of this species considering three oocyte development stages (previtellogenic oocyte, immature vitellogenic oocyte, and mature vitellogenic oocyte) (Vélez-Arellano et al 2014). Some studies describe the diversity of diatoms in the diet of C. virgulatus and conclude that diatoms are not the only food source for this species (Siqueiros-Beltrones & Argumedo-Hernandez 2012). Studies on the reproductive cycle of C. articulatus in Mexico are scarce (Rojas-Herrera 1988, HolguinQuiñones & Michel-Morfín 2002, Flores-Campaña et al 2007, García-Ibáñez et al 2013, Morfin-Jiménez et al 2014, Ramírez-Álvarez et al 2014)
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