Spatial pattern of distribution and reproductive strategy of vermiculate electric-rays Narcine vermiculatus.

In the study, the authors evaluate the spatial distribution pattern of vermiculate electric-ray Narcine vermiculatus using geostatistical techniques to predict its spatial distribution and indicate its reproduction strategy. From January 2008 to December 2009, 3333 specimens of vermiculate electric-ray were caught. Total length (LT ), sex, maturity stage, catch location and depth were recorded for each specimen. The LT of vermiculate electric-ray ranged from 6.7-24.6 cm. The authors estimate an irregular spatial structure, with a high-density patch ( x ¯ = 53 ind. ha-1 ) located on the east coast, which concentrates 65.2% of the specimens. The high-density patch consists mainly of large juveniles (13.3-19.5 cm LT ), sub-adults (14.0-19.8 cm LT ) and young adults (14.7-21.3 cm LT ). Data indicate that adults migrate to the high-density patch to reproduce. Males reached maturity at 14.5 cm LT , whereas females reached maturity at 19.3 cm LT . Vitellogenesis in female vermiculate electric-ray begins in June; ovulation, mating, fertilization and gestation in October and birth begins in February. This indicates an annual cycle with vitellogenesis and consecutive gestation, in females synchronized in reproduction. Fecundity was 1-8 ( x ¯ = 4), and the sex ratio of embryos was 1:1. The birth occurred between February and April, with an average size at parturition of 6.3 cm LT . Incidental capture of sub-adults and adults of N. vermiculatus by bottom trawls threatens the survival of this species.

Presence of pregnant females of the Gorgona guitarfish, Pseudobatos prahli, in the Mexican tropical Pacific.

Five specimens (four females and one male) of the Gorgona guitarfish, Pseudobatos prahli, were sighted during two dives carried out off the western Gulf of Tehuantepec. This document describes the reproductive condition of three adult females captured, two of which had uterine eggs, whereas one had embryos. The sighting and capture of specimens occurred during two Tehuano wind events; the authors, therefore, believe that variations in temperature and dissolved oxygen could have affected P. prahli, leading it to carry out temporal migrations towards coastal shallow waters.

A new species of Spirophilometra (Nematoda: Philometridae) from the yellowfin snook Centropomus robalito (Osteichthyes) in southern Mexico.

A new nematode species, Spirophilometra pacifica sp. n. (Philometridae), is described from gravid female specimens collected from the mouth cavity (the upper palate) of the fish (yellow snook) Centropomus robalito (Centropomidae, Perciformes) from the Chantuto-Panzacola system, Chiapas, in the Pacific coast of Mexico. Its morphology is very similar to that of the species originally described as Philometra centropomi Caballero, 1974, but the gravid females of S. pacifica are about three times longer (body length 11.63-18.17 mm); host species and the geographical distribution of both these forms also differ. Scanning electron microscope (SEM) examination of S. pacifica, used for the first time for a Spirophilometra species, confirmed the presence of numerous minute cuticular spines on the body surface, 14 cephalic papillae arranged in two circlets, and two small lateral papilla-like caudal projections. It is evident that some features of P. centropomi were incorrectly described (its types are not available) and this species is now transferred to Spirophilometra as S. centropomi (Caballero, 1974) comb. n.