Geukensia demissa es un mitílido que invadió el estuario del Lago de Maracaibo. De este mejillón, por ser una especie nueva en el lago, se desconocen todos los aspectos relacionados con su biología reproductiva, por lo que en este trabajó se describió el ciclo reproductivo de este molusco bivalvo, a partitr de una población ubicada en el Estrecho del Lago de Maracaibo (Nazaret). Durante 12 meses (enero a diciembre) fueron recolectados 80 animales en la playa de Nazaret, sector El Moján. A cada animal se le realizó una disección, tomando muestras del fluido gonadal que posteriormente se observaron al microscopio para determinar la presencia y el estado de madurez de los gametos. Los diferentes estados de desarrollo gametogénico fueron tomados de la clasificación descrita por Shafee (1989). El índice gonadal se calculó mediante la ecuación IG = Σ (n × V)/N. Los resultados mostraron que esta especie tiene un ciclo reproductivo continuo, presentando ejemplares maduros y desovados durante todo el año. Se observaron dos procesos gametogénicos: el primero comenzó en la época seca y se extendió hasta el comienzo de la época lluviosa, cuando los gametos alcanzaron su máxima madurez; el segundo comenzó en la época lluviosa (septiembre) y se extendió hasta finales de noviembre cuando los gametos volvieron a estar maduros. Se observaron dos picos de desove, uno en el mes de julio y el otro a finales de diciembre. No se observó 100% de desove en la población. Se pudo apreciar sincronía en la madurez y el desove tanto en las hembras como en los machos.
Distribution and taxonomy of Pyrgophorus platyrachis (Caenogastropoda: Hydrobiidae) in the Sistema de Maracaibo, Venezuela. The presence of a microgastropod identified as Potamopyrgus sp. was detected previously in the Maracaibo System; nevertheless, a detailed morphological analysis identified this snail in other genera. The objective of this work is to update the distribution and taxonomy of Pyrgophorus platyrachis in the Maracaibo System, Venezuela in samples obtained between 2001 and 2009. The presence of hundreds of individuals of P. platyrachis were observed in the estuary, indeed in the localities of the Gran Eneal lagoon (4 111 snails), Peonías lagoon (229 snails), Punta Capitán Chico (758 snails), San Francisco (2 517 snails), Curarire (240 snails), Apon River mouth (173 snails), Ojeda City (240 snails), Bachaquero (128 snails) and Tomoporo de Agua (385 snails). We performed a taxonomical analysis, and emphasized in ecological aspects, such as the distribution of the species and habitat features, as near vegetation and type of associated sediment. We found three morphotypes of the species, one smooth, another with spiral striations and the other with spines. Smooth morphotype was exclusive of the Gran Eneal lagoon, Peonías lagoon, Punta Capitan Chico and Apon River mouth localities, whereas the other two morphotypes were found together in the remaining localities. According to our detailed anatomical and taxonomical analysis we propose a synonymy between P. platyrachis and the other species described like Pyrgophorus parvulus and Pyrgophorus spinosus.
Echinoderms are a major group of marine invertebrates that often play integral roles within the marine ecosystem. Studies about their occurrence, abundance, and distribution in Venezuela are focused in the central-eastern coasts; hence the aim of this study is to describe the echinoderm community in the north-western coast of the Gulf of Venezuela. Samples were collected from three sites in the Venezuelan Guajira Peninsula (Castilletes, Porshoure, and Kazuzain) where patchy coral reefs and seagrass meadows are abundant. According to the substrate, two methods were performed using quantitative (1 m² quadrates), and qualitative free-diving observations. All organisms were counted and identified to the lowest possible taxonomic level; finally, diversity (Shannon diversity index), richness (number of species), and dominance in the different sampled substrates were recorded. The updated list of echinoderms of the Gulf of Venezuela reported in this research, includes 20 genera, 15 families, 10 orders, four classes, and 28 species. The richest class was Ophiuroidea, with 18 species, followed by Asteroidea, Echinoidea and Holothuroidea, with three species each. Castilletes was the sampling site with the higher number of species (18 species), followed by Porshoure (15 species), and lastly Kazuzain (12 species). Our observations indicate that the number of species and abundance were higher when found in coral reefs (21 species, 80.69% of the total collected individuals) in contrast to the species found in seagrass beds (16 species, 19.31% of the total of individuals collected). This updated list of echinoderms represents 11.54% of the total diversity of the phylum in the marine areas from the coast of Venezuela; it is suggested that this percentage is greatly influenced by the differences of habitats and substrates alongside the north-western coast in the Gulf of Venezuela.
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