Anatomical characterization of the digestive system of the pufferfish (Chilomycterus spinosus spinosus)

Descriptive studies of the fish digestive system are fundamental because they provide information on the biology of the species. Thus, the objective of this study was to morphologically describe the digestive system of the pufferfish, Chilomycterus spinosus spinosus. For this, adult specimens of pufferfish (n = 10) of both sexes were used. The animals were fixed with 10% aqueous formaldehyde solution, dissected, analyzed descriptively and photographed. The results demonstrate that the pufferfish has a morphologically modified digestive system, which is adapted to the defense behavior. This species presents a pouch-shaped diverticulum, that is called abdominal pouch, which allows the expansion of the celomatic cavity and the temporary storage of food. Although it is used to store food, macroscopically the abdominal pouch does not show gastric folds. However, this absence is compensated by a small intestine containing innumerable villi.

Morphological Studies on the Gills of Puffer Fish (Lagocephalus sceleratus, Gmelin, 1789) / Estudios Morfológicos en Branquias del Pez Globo (Lagocephalus sceleratus, Gmelin, 1789)

In the present study, we focused on the morphology of L. sceleratus gills using gross anatomy, scanning electron microscopy as well as light microscopy. Results of this study revealed that the gill openings appeared as simple slits anterior to the pectoral fin without distinct opercular cover. The gill system consisted of three pairs of gill arches carrying two rows of gill rakers on its concave border and gill filaments on its convex border. SEM showed that all surfaces of the gill arch were characterized by the presence of the longitudinal ridges with many taste buds in addition to many spines around the rakers. Histologically, the gill arch was composed of curved bar of hyaline cartilage with slightly elevated area corresponding to the sites of gill rakers. Each filament was formed of a thin central cartilaginous core surrounded by peripheral cartilaginous matrix and covered by primary epithelial layer with abundant mucous cells. The chloride cells appeared mainly near to the base of secondary lamellae. Each gill filament gave rise to a very large number of secondary lamellae on both sides. The epithelial lining of the secondary lamellae comprised epithelial pavement cells, few mucous cells and pillar cells. The latter interposed the enriched blood capillaries. These findings suggest that L. sceleratus gills have characteristic morphological features that are related to adaptive functions for feeding habits, osmoregulation and respiratory mechanism with in their living environment.

El objetivo fue estudiar la morfología de las branquias de Sceleratus L. desde la anatomía macroscópica, microscopía electrónica de barrido, así como la microscopía de luz. Los resultados revelaron que las aberturas branquiales aparecían como simples rendijas por delante de la aleta pectoral sin una cubierta opercular distinta. El sistema branquial consistió en tres pares de arcos branquiales con dos filas de branquiespinas en sus filamentos branquiales frontales y cóncavos en el margen. La microscopía de barrido mostró que todas las superficies del arco branquial se caracterizaron por la presencia de crestas longitudinales con muchas papilas gustativas, además de una cantidad importante de espinas alrededor de los rastrillos. Histológicamente, el arco branquial se compone de una barra curva de cartílago hialino con una zona ligeramente elevada, correspondiente a los sitios de branquiespinas. Cada filamento se formó por un delgado núcleo central cartilaginoso rodeado de matriz cartilaginosa periférica y cubierto por una capa epitelial primaria con abundantes células mucosas. Las células de cloruro aparecieron principalmente cerca a la base de laminillas secundaria. Cada filamento de las branquias en ambos lados dio origen a un gran número de laminillas secundarias. El revestimiento epitelial de laminillas secundarias estaba formado de células epiteliales, algunas células mucosas y células sostenedoras. Estos hallazgos sugieren que las branquias de L. sceleratus tienen características morfológicas que están relacionadas con las funciones de adaptación de los hábitos de alimentación, la osmorregulación y el mecanismo respiratorio de acuerdo a su entorno.

Ecología trófica del pez Arothron meleagris (Tetraodontiformes: Tetraodontidae) en el arrecife de Los Frailes, Baja California Sur, México

Trophic ecology of the fish Arothron meleagris (Tetraodontiformes: Tetraodontidae) from Los Frailes reef, Southern Baja California, Mexico. Monthly samples were taken from November 2004 to October 2005 in the Los Frailes reef, BCS, Mexico. The objective was to determine the feeding habits of the pufferfish, Arothron meleagris, as well as possible variations in feeding patterns due to size and/or sex. We captured 101 specimens, with all stomachs contained food. The index of relative importance (IRI) was used to determine the main items; which were non-identified organic matter (NIOM) (30.44%), Echinometra vanbrunti (26.25 %), Porifera (12.63 %), Pocillopora spp. (11.84%), Bryozoa (5.37 %) and Porites spp. (4.83 %). Levin’s index indicated a low trophic niche breadth (Bi= 0.12) and allowed us to determine that A. meleagris is a specialist predator with strong preferences towards certain food types. The Morisita-Horn index showed a high trophic overlap between sexes ( or = 0.78), seasons (hot and cold or = 0.95) and among sizes (small and medium or = 0.94; small and large or = 0.74; medium and large or = 0.83). Rev. Biol. Trop. 57 (1-2): 113-123. Epub 2009 June 30.

Con la finalidad de determinar los hábitos alimenticios del tamboril de oro Arothron meleagris, así como sus posibles variaciones de alimentación por talla y sexo, se realizaron muestreos mensuales de noviembre 2004 a octubre 2005, en el arrecife de Los Frailes, Baja California Sur, México. Se capturaron un total de 101 ejemplares, en los cuales todos los estómagos contenían alimento. Se aplicó el índice de importancia relativa (IIR) para determinar los principales categorías alimenticias (ítems), los cuales fueron: Echinometra vanbrunti (26.25 %), Porifera (12.63 %), Pocillopora spp. (11.84%), Bryozoa (5.37 %) y Porites spp. (4.83 %). El índice de Levin indica baja amplitud del nicho trófico (Bi= 0.12) por lo que se le puede considerar como un depredador especialista con marcadas preferencias hacia algunos tipos alimentarios. El índice de Morisita-Horn indicó que existe un traslape alto entre las dietas por sexo (hembras y machos o = 0.78), temporadas (cálida y fría o = 0.95) y entre tallas (chica y mediana o = 0.94, chica y grande o = 0.74, mediana y grande o = 0.83).