Feeding habits of Urotrygon microphthalmum (Myliobatiformes: Urotrygonidae) caught off northeastern Brazil

The feeding habits of Urotrygon microphthalmum, a Critically Endangered (CR) species, were investigated through stomach contents analysis from specimens caught on bottom double rigged otter trawls in Pernambuco state, Brazil, between March of 2010 and March of 2012. A total of 338 stomachs were analyzed, and 31 food items were identified in the diet of U. microphthalmum. The species ingests mainly shrimps. The diets between males and females were not different, and an ontogenetic diet shift was not observed. The estimated species' trophic level is 3.5, classifying it as a secondary order consumer.(AU)

Os hábitos alimentares de Urotrygon microphthalmum, uma espécie Criticamente Em Perigo (CR), foram investigados através de análise de conteúdo estomacal de espécimes capturados no arrasto duplo com portas no estado de Pernambuco, Brasil, entre março de 2010 e março de 2012. Um total de 338 estômagos foram analisados e 31 item alimentares foram identificados na dieta de U. microphthalmum. A espécie ingere principalmente camarões. A dieta entre machos e fêmeas não foi diferente e não foi observada mudança ontogenética na dieta. O nível trófico estimado da espécie é 3,5, classificando-a como consumidora de segunda ordem.(AU)

Feeding habits of the cockfish, Callorhinchus callorynchus (Holocephali: Callorhinchidae) from off northern Argentina

The feeding habits of Callorhinchus callorynchus were investigated in coastal waters off northern Argentina. The effect of body size, seasons and regions was evaluated on female diet composition using a multiple-hypothesis modelling approach. Callorhinchus callorynchus fed mainly on bivalves (55.61% PSIRI), followed by brachyuran crabs (10.62% PSIRI) and isopods (10.13% PSIRI). Callorhinchus callorynchus females showed changes in the diet composition with increasing body size and also between seasons and regions. Further, this species is able to consume larger bivalves as it grows. Trophic level was 3.15, characterizing it as a secondary consumer. We conclude that C. callorynchus showed a behavior of crushing hard prey, mainly on bivalves, brachyuran, gastropods and anomuran crabs. Females of this species shift their diet with increasing body size and in response to seasonal and regional changes in prey abundance or distribution.(AU)

RESUMEN Los hábitos alimentarios de Callorhinchus callorynchus fueron investigados en las aguas costeras del norte de Argentina. Se evaluó el efecto del tamaño del cuerpo, la temporada y la región sobre la composición de la dieta de las hembras mediante un enfoque de modelado de múltiples hipótesis. Callorhinchus callorynchus se alimentó principalmente de bivalvos (55,61% PSIRI), seguido de cangrejos brachyuras (10,62% PSIRI) y de isópodos (10,13% PSIRI). Las hembras de C. callorynchus presentaron cambios en la dieta con incremento del tamaño del cuerpo, la temporada y la región. Además, esta especie es capaz de consumir bivalvos de mayor tamaño a medida que incrementa el tamaño del cuerpo. El nivel trófico fue calculado en 3,15, caracterizando a esta especie como un consumidor secundario. Concluimos que C. callorynchus presentó un comportamiento de triturador de presas duras, principalmente bivalvos, cangrejos y gasterópodos. Las hembras de esta especie cambian su dieta con el incremento del tamaño del cuerpo y en respuesta a cambios temporales y regionales en la abundancia y distribución de sus presas.(AU)

Feeding ecology of elasmobranch species in southeastern Brazil

The feeding ecology of five elasmobranch species was studied on the southern coast of Rio de Janeiro, southwestern Atlantic Ocean. The specimens were caught with a trawl or bottom longline between January 2006 and August 2007. The diets of Psammobatis rutrum and Psammobatis extenta appeared to be basically carcino-benthophagous, with a very small niche width. Rioraja agassizii was basically carcino/ichthyo-benthophagous, also with a narrow niche, including teleost fish and shrimp, but in different proportions according to age and sex. Rhizoprionodon lalandii was ichthyophagous, not influenced by age or sex. The analyses of these species and Atlantoraja cyclophora indicated two trophic groups: one composed of the smaller rays, P. extenta and P. rutrum, which basically fed on small crustaceans, polychaetes and nematodes; and the other of R. lalandii and the larger rays R. agassizii and A. cyclophora, which preyed on teleost fish and brachyurans.(AU)

Devido à lacuna de conhecimento sobre os elasmobrânquios estudamos a ecologia alimentar de cinco espécies desse grupo, no litoral sul do Rio de Janeiro. Os exemplares foram capturados por rede de arrasto e espinhel de fundo, entre janeiro de 2006 e agosto de 2007. As dietas de Psammobatis rutrum e Psammobatis extenta se mostraram basicamente carcino-bentofagas, com uma largura de nicho estreito. Rioraja agassizii foi considerada carcino/ictio-bentófaga, também com uma largura de nicho estreita. A espécie se alimenta com peixe e camarão, mas em proporções diferentes de acordo com a idade e sexo. A dieta de Rhizoprionodon lalandii foi considerada ictiófaga e não é influenciada pela idade ou sexo. As análises destas espécies e Atlantoraja cyclophora indicaram a formação de dois grupos tróficos: um composto pelas raias menores, P. extenta e P. rutrum, que basicamente se alimentam de pequenos crustáceos, poliquetos e nematodas; e o outro de R. lalandii e as raias maiores R. agassizii e A. cyclophora, que predam peixes teleósteos e brachyuras.(AU)

Diet composition and feeding habits of the eyespot skate, Atlantoraja cyclophora (Elasmobranchii: Arhynchobatidae), off Uruguay and northern Argentina

The eyespot skate, Atlantoraja cyclophora, is an endemic species from the southwestern Atlantic, occurring from Rio de Janeiro, Brazil, to northern Patagonia, Argentina. The feeding habits of this species, from off Uruguay and north Argentina, were evaluated using a multiple hypothesis modelling approach. In general, the diet was composed mainly of decapod crustaceans, followed by teleost fishes. Molluscs, mysidaceans, amphipods, isopods, lancelets and elasmobranchs were consumed in lower proportion. The consumption of shrimps drecreased with increasing body size of A. cyclophora. On the other hand, the consumption of teleosts increased with body size. Mature individuals preyed more heavily on crabs than immature individuals. Teleosts were consumed more in the south region (34º - 38ºS) and crabs in the north region (38º - 41ºS). Shrimps were eaten more in the warm season than in the cold season. Prey size increased with increasing body size of A. cyclophora , but large individuals also consumed small teleosts and crabs. Atlantoraja cyclophora has demersal-benthic feeding habits, shifts its diet with increasing body size and in response to seasonal and regional changes in prey availability and distribution.(AU)

La raya de círculos, Atlantoraja cyclophora , es una especie endémica del Atlántico Sudoccidental, que se distribuye desde Río de Janeiro, Brasil, hasta el norte de la Patagonia, Argentina. Los hábitos alimentarios de esta especie fueron evaluados frente a la costa de Uruguay y norte de Argentina, utilizando un enfoque de modelado de múltiples hipótesis. En general, la dieta estuvo compuesta principalmente por crustáceos decápodos (71,37 %IRI), seguido de peces teleósteos (28,54 %IRI). En menor proporción fueron consumidos moluscos, misidáceos, anfípodos, isópodos, anfioxos y elasmobranquios. El consumo de decápodos Natantia disminuyó con el incremento del tamaño del cuerpo de A. cyclophora . Por otro lado, el consumo de teleósteos se incrementó con el incremento del tamaño del cuerpo. Individuos maduros consumieron cangrejos en mayor proporción que individuos inmaduros. Los teleósteos fueron consumidos mayormente en la región sur (34º - 38ºS) y los cangrejos en la región norte (38º - 41ºS). Los decápodos Natantia fueron más consumidos en la estación cálida que en la estación fría. El tamaño de las presas consumidas se incrementó con el aumento del tamaño corporal de A. cyclophora , pero individuos de mayor tamaño no abandonadon el consumo de pequeños cangrejos y teleósteos. Atlantoraja cyclophora presenta hábitos alimentarios demersal-bentónicos, cambia su dieta con el incremento del tamaño corporal y en respuesta a cambios estacionales y regionales en la disponibilidad y distribución de las presas.(AU)

Purification and characterization of a phospholipase A2-IIA from common stingray (Dasyatis pastinaca) intestine.

A phospholipase A2 belonging to IIA group secretory PLA2 was isolated and purified to homogeneity from the intestine of common stingray (Dasyatis pastinaca) using acidic treatment (pH 1.5) and ammonium sulphate precipitation methods combined with single-column ion-exchange chromatography. The purified enzyme was found to be a glycosylated monomeric protein with a molecular mass of about 14 kDa. The stingray sPLA2-IIA had optimum activity at 45°C, unlike known mammalian PLA2-IIAs, which show optimum activity at 37°C. The purified enzyme exhibited a specific activity of 290 U/mg at optimal conditions (pH 9.5 and 45°C) in the presence of 6 mM NaDC and 8 mM CaCl2 with egg yolk as substrate. The NH2-terminal sequence of the enzyme and some protein fragments obtained from its tryptic digestion were also determined. All sequences obtained were similar to those of sPLA2-IIA. The enzyme also showed good stability in the presence of organic solvents, acidic and alkaline pH media and high temperature conditions. Thus, the purified enzyme exhibited a number of unique and promising properties, making it a potential possible candidate for future applications in the treatment of phospholipid-rich industrial effluents and synthesis of useful preparations for the food production and processing industry.