RESUMO
The competitive exclusion principle establishes that the coexistence of closely related species requires a certain degree of resource partitioning. However, populations have individuals with different morphological or behavioral traits (e.g., maturity stages, sexes, temporal or spatial segregation). This interaction often results in a multi-level differentiation in food preferences and habits. We explored such resource partitioning between and within three batoid species: Hypanus dipterurus, Narcine entemedor, and Rhinoptera steindachneri in the southern Gulf of California, Mexico, using a combination of stomach content (excluding R. steindachneri) and stable isotope analyses. We found a clear differentiation between H. dipterurus and N. entemedor, where the latter exhibited more benthic habitats, supported by a greater association to infaunal prey and higher δ13C values. Though the degree and patterns of intra-specific segregation varied among species, there was a notable differentiation in both sex and stage of maturity, corresponding to changes in specialization (i.e., isotopic niche breadth) or trophic spectrum (varying prey importance and isotopic values per group). This work is a promising step towards understanding the dietary niche dynamics of these species in a potentially important feeding area within the southern Gulf of California, as well as the biological and ecological mechanisms that facilitate their coexistence.
Assuntos
Geraniaceae , Avaliação Nutricional , Humanos , California , Estado Nutricional , Preferências AlimentaresRESUMO
The fossil record of pinnipeds documents a suite of morphological changes that facilitate their ecological transition from a terrestrial to an aquatic lifestyle. Among these is the loss of the tribosphenic molar and the behavior typically associated with it in mammals: mastication. Instead, modern pinnipeds exhibit a broad range of feeding strategies that facilitate their distinct aquatic ecologies. Here, we examine the feeding morphology of two species of pinnipeds with disparate feeding ecologies: Zalophus californianus, a specialized raptorial biter, and Mirounga angustirostris, a suction specialist. Specifically, we test whether the morphology of the lower jaws facilitates trophic plasticity in feeding for either of these species. We used finite element analysis (FEA) to simulate the stresses during the opening and closing of the lower jaws in these species to explore the mechanical limits of their feeding ecology. Our simulations demonstrate that both jaws are highly resistant to the tensile stresses experienced during feeding. The lower jaws of Z. californianus experienced the maximum stress at the articular condyle and the base of the coronoid process. The lower jaws of M. angustirostris experienced the maximum stress at the angular process and were more evenly distributed throughout the body of the mandible. Surprisingly, the lower jaws of M. angustirostris were even more resistant to the stresses experienced during feeding than those of Z. californianus. Thus, we conclude that the superlative trophic plasticity of Z. californianus is driven by other factors unrelated to the mandible's tensile resistance to stress during feeding.
Assuntos
Caniformia , Leões-Marinhos , Focas Verdadeiras , Animais , Arcada Osseodentária , MandíbulaRESUMO
The size at which a certain fraction of a fish population reaches sexual maturity is an important parameter of life history. The estimation of this parameter based on logistic or sigmoid models could provide different ogives and values of length at maturity, which must be analyzed and considered as a basic feature of biological reproduction for the species. A total of 305 individuals of Narcine entemedor (N. entemedor) were obtained from artisanal fisheries in the Bahía de La Paz, Mexico. For the organisms sampled, sexes were determined and total length (TL) in cm was measured from October 2013 to December 2015. The results indicated that the females were larger, ranging from 48.5 cm to 84 cm TL, while males varied from 41.5 cm to 58.5 cm TL. The sex ratio was dominated by males ranging from 45-55 cm TL, while females were more abundant from 60 to 85 cm TL. Mature females were present all year long, exhibiting a continuous annual reproductive cycle. The length at maturity data were described by the Gompertz model with value of 55.87 cm TL. The comparison between models, and the model selection between them, showed that the Gompertz model had maximum likelihood and smaller Akaike information criterion, indicating that this model was a better fit to the maturity proportion data of N. entemedor.
RESUMO
O tempo de deterioração de frutas minimamente processadas é diretamente proporcional à sua taxa respiratória, sendo a temperatura de armazenamento um dos fatores que mais infl uenciam na vida de prateleira destes produtos. Os danos causados pelo corte aumentam a taxa respiratória e reações bioquímicas, tal como o escurecimento enzimático. O objetivo deste trabalho foi avaliar o efeito de três tipos de cortes (em fatias, cubos e metades) e duas temperaturas de armazenamento (5°C e 8°C) na taxa respiratória e na coloração de polpa de peras Packhams Triumph minimamente processadas e acondicionadas em embalagem rígidas de polietileno com tampa durante sete dias de armazenagem. Logo após o processamento, a taxa respiratória das frutas submetidas ao corte em fatias e armazenadas a 8°C, e ao corte em cubos e armazenadas a 5°C e 8°C apresentou-se 62% maior que peras submetidas ao corte em fatias e mantidas a 5°C. Aos sete dias de armazenamento, a taxa respiratória foi menor a 5°C, sem diferenças quanto ao tipo de corte. O tipo de corte afetou o atributo L (escurecimento) da polpa, com as metades e cubos não apresentando escurecimento (L=75,4-75,9), como as fatias (L=72,8). Os valores de a*, Hab e C* indicam que houve maior escurecimento das fatias armazenadas a 8°C.(AU)
The deterioration rate of minimally processed fruit is proportional to its respiratory rate, and the storage temperature is one of the factors that most infl uence it. Damages caused by cutting increase respiration and biochemical reactions such as browning. The objective of this study was to evaluate the effect of three types of cuts (sliced, diced and in halves) and two storage temperatures (5°C and 8°C) on the respiratory rate and color attributes of Triumph Packhams pears stored in closed rigid polyethylene containers for seven days. After processing, the respiratory rate of pears slices stored at 8°C and pear cubes stored at 5 and 8°C was 62% higher than the pear cut into slices and stored at 5°C. On day seven, the respiratory rate was lower at 5°C and did not show any differences according to the type of cut. The type of cut affected the color parameter L (lightness). The fruit cut in alves and cubes did not show any browning (L = 75.4 to 75.9), as opposed to the sliced fruit (L = 72.8). The values of a*, C* and Hab indicated that slices stored at 8°C showed the highest browning rate.(AU)
Assuntos
Pyrus/classificação , Contaminação de Alimentos/análise , Bioquímica , Manipulação de Alimentos , Temperatura , Taxa RespiratóriaRESUMO
O tempo de deterioração de frutas minimamente processadas é diretamente proporcional à sua taxa respiratória, sendo a temperatura de armazenamento um dos fatores que mais infl uenciam na vida de prateleira destes produtos. Os danos causados pelo corte aumentam a taxa respiratória e reações bioquímicas, tal como o escurecimento enzimático. O objetivo deste trabalho foi avaliar o efeito de três tipos de cortes (em fatias, cubos e metades) e duas temperaturas de armazenamento (5°C e 8°C) na taxa respiratória e na coloração de polpa de peras Packhams Triumph minimamente processadas e acondicionadas em embalagem rígidas de polietileno com tampa durante sete dias de armazenagem. Logo após o processamento, a taxa respiratória das frutas submetidas ao corte em fatias e armazenadas a 8°C, e ao corte em cubos e armazenadas a 5°C e 8°C apresentou-se 62% maior que peras submetidas ao corte em fatias e mantidas a 5°C. Aos sete dias de armazenamento, a taxa respiratória foi menor a 5°C, sem diferenças quanto ao tipo de corte. O tipo de corte afetou o atributo L (escurecimento) da polpa, com as metades e cubos não apresentando escurecimento (L=75,4-75,9), como as fatias (L=72,8). Os valores de a*, Hab e C* indicam que houve maior escurecimento das fatias armazenadas a 8°C.
The deterioration rate of minimally processed fruit is proportional to its respiratory rate, and the storage temperature is one of the factors that most infl uence it. Damages caused by cutting increase respiration and biochemical reactions such as browning. The objective of this study was to evaluate the effect of three types of cuts (sliced, diced and in halves) and two storage temperatures (5°C and 8°C) on the respiratory rate and color attributes of Triumph Packhams pears stored in closed rigid polyethylene containers for seven days. After processing, the respiratory rate of pears slices stored at 8°C and pear cubes stored at 5 and 8°C was 62% higher than the pear cut into slices and stored at 5°C. On day seven, the respiratory rate was lower at 5°C and did not show any differences according to the type of cut. The type of cut affected the color parameter L (lightness). The fruit cut in alves and cubes did not show any browning (L = 75.4 to 75.9), as opposed to the sliced fruit (L = 72.8). The values of a*, C* and Hab indicated that slices stored at 8°C showed the highest browning rate.
Assuntos
Bioquímica , Contaminação de Alimentos/análise , Manipulação de Alimentos , Pyrus/classificação , Taxa Respiratória , TemperaturaRESUMO
All species of sawfish are listed by the International Union for the Conservation of Nature (IUCN) as endangered or critically endangered. In fact, the smalltooth sawfish Pristis pectinata, and the largetooth sawfish Pristis pristis, have been declared to be regionally and locally extinct from the US Atlantic coast and the Gulf of California, Mexico, respectively, likely due to overfishing. However, here we dispute these claims by illustrating how lack of existence of a given species within a region can be misconstrued as evidence for extinction.(AU)
Todas as espécies de peixe-serra são qualificadas pela União Internacional para a Conservação da Natureza como ameaçadas ou criticamente ameaçadas de extinção. De fato, o peixe-serra-de-dentes-pequenos, Pristis pectinata, bem como o peixe-serrade-dentes-grandes, Pristis pristis, têm sido declarados como regionalmente e localmente extintos da costa atlântica dos EUA e do Golfo da Califórnia e México, respectivamente, provavelmente devido ao excesso da pesca. No entanto, aqui pretendemos questionar estas extinções ilustrando como a falta de evidências da existência de uma espécie em uma região pode ser mal interpretada como evidência de extinção.(AU)
Assuntos
Animais , Espécies em Perigo de Extinção/estatística & dados numéricos , Elasmobrânquios/classificaçãoRESUMO
All species of sawfish are listed by the International Union for the Conservation of Nature (IUCN) as endangered or critically endangered. In fact, the smalltooth sawfish Pristis pectinata, and the largetooth sawfish Pristis pristis, have been declared to be regionally and locally extinct from the US Atlantic coast and the Gulf of California, Mexico, respectively, likely due to overfishing. However, here we dispute these claims by illustrating how lack of existence of a given species within a region can be misconstrued as evidence for extinction.(AU)
Todas as espécies de peixe-serra são qualificadas pela União Internacional para a Conservação da Natureza como ameaçadas ou criticamente ameaçadas de extinção. De fato, o peixe-serra-de-dentes-pequenos, Pristis pectinata, bem como o peixe-serrade-dentes-grandes, Pristis pristis, têm sido declarados como regionalmente e localmente extintos da costa atlântica dos EUA e do Golfo da Califórnia e México, respectivamente, provavelmente devido ao excesso da pesca. No entanto, aqui pretendemos questionar estas extinções ilustrando como a falta de evidências da existência de uma espécie em uma região pode ser mal interpretada como evidência de extinção.(AU)