Caracterización histológica y morfológica del tracto digestivo de la merluza austral (Merluccius australis) / Histological and morphological characterization of the digestive tract of southern hake (Merluccius australis)

Las características anatómicas e histológicas del tracto alimentario de la merluza austral (Merluccius australis) se han estudiado con el fin de comprender la fisiología digestiva y formular alimentos balanceados adecuados. M. australis posee un esófago corto, un estómago en forma de y grande y un intestino corto. Histológicamente, el tracto digestivo está formado por cuatro capas: la mucosa, submucosa, muscularis y la serosa. El esófago es un órgano tubular corto de pared gruesa con una gran capacidad de distensión y abundantes células caliciformes secretoras de mucus que permite el paso de grandes presas. El estómago es grande y musculoso, con alta capacidad de distensión. No se observo la presencia de apéndices pilóricos. El intestino es corto y dividido en regiones: proximal, medio y distal. En la región anterior del intestino se observaron abundantes células caliciformes, que disminuyeron en la región media para finalmente dispersarse en la región posterior. Además, los enterocitos mostraron un aumento en la presencia de vacuolas supranuclear en la región posterior del intestino. Los resultados de este estudio anatómico e histológico indican que M. australis tiene un sistema digestivo similar a otros peces gadiformes, el cual está adaptado para digerir y absorber presas ricas en proteínas, principalmente pescados y crustáceos.

The anatomy and histology features of alimentary tract of southern hake (Merluccius australis) have been studied in order to understand the digestive physiology and formulate suitable feeds. M. australis has a short oesophagus, large y-shaped stomach and short intestine, and histologically, the digestive tract is formed by four layers: mucosa, submucosa, muscularis and serosa. The oesophagus is a short tubular thick-walled organ with a great distension capacity and abundant mucus secreting goblet cells allowing the passage of large preys. The stomach is large and muscular with high capability for distension. Pyloric caeca were not present. The intestine is short and divided into a proximal middle and distal segment. In the anterior region of the intestine was observed abundant goblet cells, which decreased in the middle region and finally dispersed in the posterior region. Additionally, enterocytes showed an increase in the presence of supranuclear vacuoles at the posterior region of the intestine. The results of this anatomical and histological study indicate that M. australis has a digestive tract similar to other gadiform fishes, which is adapted to digest and absorb protein-rich preys, mainly fish and crustacean.

Captura de peces no comerciales con espinel experimental de fondo en Isla Gorgona, Colombia, y su área de influencia / Non-commercial fish catches with experimental bottom long line fishing in Gorgona Island, Colombia, and its surroundings areas

Eels and moray eels are among the species that lack commercial value but that are important as bait. However, little information is available about Colombian fishing by-products. Between 2005 and 2009, field work was done in Gorgona National Natural Park and its surrounding areas, with a fishing line made of traditional “J” and circular or curve hooks. We analyzed the catch composition, comparing both types of hooks, emphasizing whether the circular hook modified or not non-commercial captures. Overall, 189 fishing throws where analyzed, standardizing the Catch Per Effort (CPUE) in number of individuals and in kilograms per 100 hooks per hour of task. A total of 50 species where captured, of which 14 are part of the non-commercial category. There were no significant differences for hook types (U=25228, P>0.1), and Gymnothorax equatorialis and Echiophis brunneus were the most abundant species. Both were concentrated in the northern sector of the study area, a rocky banks sector. The mean sexual maturity size was 57.0cm in G. equatorialis, and at 85.6cm in E. brunneus. Rev. Biol. Trop. 62 (Suppl. 1): 391-405. Epub 2014 February 01.

Durante los años 2005 a 2009 se realizaron faenas experimentales de pesca en el Parque Nacional Natural Gorgona y su área de influencia, con un espinel compuesto por anzuelos tradicionales J y circulares o curvos. Este estudio analiza la composición de las capturas comparando los dos anzuelos y enfatiza en si el anzuelo circular modifica o no las capturas no comerciales (descarte). En total se analizaron 189 lances de pesca estandarizándose la captura por unidad de esfuerzo (CPUE) en número de individuos y en kilogramos por 100 anzuelos por hora de faena. Se capturaron en total 50 especies, de las cuales 14 hacen parte de la categoría no comercial o de descarte. No se detectaron diferencias significativas en la CPUE de estas especies considerando el tipo de anzuelo (U=25228, p>0.1) siendo Gymnothorax equatorialis y Echiophis brunneus las especies más abundantes Al evaluar el patrón espacial de variación de la CPUE para estas especies, se encontró que ambas se concentran en el sector norte del área de estudio, asociada a la zona de bancos rocosos. Finalmente, se estableció la talla media de madurez sexual para G. equatorialis en 57.0cm y de E. brunneus en 85.6cm.

A new species of Nezumia (Gadiformes: Macrouridae) from Fieberling Guyot, eastern North Pacific Ocean

A new species of the macrourine genus Nezumia is described from specimens collected from the crest of Fieberling Guyot in the eastern North Pacific Ocean. The new species is distinguishable from all other Nezumia species chiefly on the basis of a high number of pelvic fin rays, a relatively high number of first dorsal fin soft rays, a steep blunt snout lacking scales ventrally, a relatively weak suborbital ridge, and a moderately long, thin barbel. Although possibly endemic to the Baja California Seamount Province, the new species appears to lack close relatives among the other Nezumia species of the eastern North Pacific Ocean. It might have arrived there either from a disjunct Tethyan distribution, thus retaining close relatives among the Atlantic Ocean species of Nezumia, or by way of stepping-stone dispersal from the Indo-west Pacific Ocean.

Notes on Galápagos grenadiers (Pisces, Gadiformes, Macrouridae), with the description of a new species of Coryphaenoides

Two unusual specimens of the grenadier genus Coryphaenoides were collected by the deep-submersible vehicle Johnson Sea-Link off the Galápagos. Unlike any other member of the genus, the snout in these specimens was rounded, non-protruding, naked anteriorly and ventrally, with no tubercular scales marking the terminal and lateral angles. They are herein described as Coryphaenoides gypsochilus. Additional specimens of grenadiers were procured by the Johnson Sea-Link, including the second and third specimens of Nezumia ventralis and the first record of Caelorinchus canus from these waters. Three species and one subspecies of Galápagos grenadiers are endemic.