Diet seasonality in South American sea lions, Otaria flavescens, was studied using 252 scats from a male-exclusive haul-out site located in Puerto Quequén (38º37'S, 58º50'W) Argentina during 2001. Prey species were identified from hard remains and their relative importance was assessed considering frequency of occurrence, abundance and biomass. The main prey consumed by sea lions were teleost fish (20 species), followed by cephalopods (four species) and crustaceans. The raneya, Raneya fluminensis, was the most frequent prey year-round, and the most abundant in autumn and winter. The Argentine anchovy, Engraulis anchoita, and the stripped weakfish, Cynoscion guatucupa, were the most abundant prey in spring and summer, respectively. Seasonal differences in the sizes consumed were only found for C. guatucupa. The sea lions from Puerto Quequén showed a diverse diet, mainly feeding on demersal and pelagic prey. Our study fills a geographical gap on the seasonal variation of the diet of South American sea lions. Two main patterns emerged from studies conducted along the geographic range of the species: (1) O. flavescens is a generalist and opportunist feeder, preying on a wide range of species; mainly those of pelagic and demersal habits, (2) South American sea lions change the frequency and/or specific composition of their diet seasonally, possibly as a result of changes in the relative availability of each species in the environment.Resumen: La variación estacional en la dieta del león marino de América del Sur, Otaria flavescens, fue estudiada a partir de 252 heces recolectadas en una colonia no reproductiva de machos localizada en Puerto Quequén (38º37'S, 58º50'O) Argentina durante el año 2001. Las presas fueron identificadas a nivel de especie a partir de restos duros y su importancia relativa fue evaluada a partir del cálculo de la frecuencia de ocurrencia, la abundancia y la biomasa. Las principales presas consumidas por los leones marinos fueron peces (20 especies), cefalópodos (cuatro especies) y crustáceos. La raneya, Raneya fluminensis, fue la presa más frecuente durante todo el año y la más abundante en otoño e invierno. La anchoíta, Engraulis anchoita, y la pescadilla de red, Cynoscion guatucupa, fueron las presas mas abundantes en primavera y verano respectivamente. Diferencias estacionales en las tallas de las presas consumidas se encontraron sólo en C. guatucupa. Los leones marinos de Puerto Quequén muestran una dieta diversa, consumiendo principalmente especies demersales y pelágicas. Nuestro estudio completa un espacio geográfico con datos sobre la dieta y contribuye al estudio de la variación estacional de la misma en los leones marinos de América del Sur. Así, se completan los estudios a lo largo de casi todo el rango de distribución geográfica. Dos conclusiones principales surgen a partir del presente estudio: (1) O. flavescens es un predador generalista y oportunista que consume un amplio rango de especies, principalmente aquellas de hábitos pelágico y demersal, (2) Los leones marinos d...

No abstract

Patterns of trait integration reflect the underlying genetic and developmental architecture of morphology and significantly influence the direction of evolution. Nevertheless, the relationship between integration and disparity is complex and unlikely to be uniform across large phylogenetic and ecological scales. To date, there are little data comparing patterns of integration across major ecological transitions, limiting understanding of the processes driving changes in trait integration and their consequences. Here, we investigated patterns of cranial integration and disparity across pinnipeds, three closely related carnivoran families that have undergone a secondary adaptation to the aquatic niche with varying levels of ecological differentiation. With a three-dimensional geometric morphometric dataset of 677 specimens spanning 15 species, we compared five models of trait integration, and examined the effects of sexual dimorphism and allometry on model support. Pinnipeds varied greatly in patterns of cranial integration compared to terrestrial carnivorans. Interestingly, this variation is concentrated in phocids, which may reflect the broader range of ecological and life-history specializations across phocid species, and greater independence from the terrestrial habitat observed in that group, relative to otariids. Overall, these results indicate that major ecological transitions, and presumably large changes in selection pressures, may drive changes in phenotypic trait integration.

Dental anomalies comprise variations in number, shape, size, position and occlusion of teeth, mainly caused by genetic mechanisms. This study aimed to investigate the nature and prevalence of dental anomalies in a large sample of pinnipeds (Otariidae and Phocidae) and to discuss potential evolutionary and ecological implications. Thirty-four species in twenty genera were sampled. The dentition of the specimens examined was compared with the normal dental formula for the species, and supernumerary and congenitally missing teeth were identified and recorded. Agenesis was observed in 0.93 % of the specimens analyzed (n = 10), being more frequent in otariids. The posteriormost upper postcanines were the teeth absent most frequently. Supernumerary teeth were observed in 1.8 % of the specimens (n = 19), more commonly in phocids. Supernumerary teeth can be interpreted as either atavistic manifestations (particularly for the posteriormost postcanines in Otariidae) or cases of disturbances in dental morphogenesis leading to the formation of extra teeth when they occur in other positions of the tooth row. Morphological dental variants such as ectopic and geminated teeth were also recorded. Cases of dental anomalies should have a limited effect on the functional morphology of the feeding apparatus in pinnipeds, with little influence on the fitness and performance of the animals. Nevertheless, understanding patterns of dental variation should contribute to future studies aiming to elucidate aspects of dental evolution and the phylogenetic relationships of pinnipeds.