Southern Sea Lion Otaria Flavescens Research Articles

GEOGRAPHICAL VARIATION OF ENTEROPARASITISM IN THE SOUTHERN SEA LION OTARIA FLAVESCENS (SHAW, 1800) OFF THE COAST OF CHILE AS EVIDENCED WITH COPROLOGICAL TESTS: IMPLICATONS FOR ZOONOTIC RISKS.

The scarce information on the helminth fauna in otariids from the Southeastern Pacific comes mainly from stranded individuals or killed for that purpose. In this study, we compared the abundance and composition of enteroparasitic assemblages of Otaria flavescens using coprological techniques. Three sampling localities from north to south spanning 2,200 km off the Chilean coast were considered (Iquique, Viña del Mar, and Talcahuano). In all, 60 fecal samples were collected, and eggs belonging to 5 taxa were found in 91.6% of the samples. They were the anisakid nematodes Contracaecum and Pseudoterranova, the cestode Adenocephalus (syn. Diphyllobothrium), the trematode Ogmogaster, and the acanthocephalan Corynosoma. Samples from southern Chile (Talcahuano) showed the highest prevalence. Adenocephalus eggs had the highest prevalence and abundance in Iquique and Talcahuano, whereas Ogmogaster was the less prevalent and abundant in all sampling localities. Corynosoma eggs had similar prevalence and abundance among sampling localities, and Pseudoterranova eggs were absent in Iquique and with median prevalence values in Viña del Mar and Talcahuano. Thus, the composition of parasite egg assemblages was different between sampling localities. These differences between sampling localities may help to explain differential records of some zoonotic parasitoses such as pseudoterranovosis and diphyllobothriosis in Peru and Chile, where consumption of raw or marinated fish (ceviche) is common. For example, the lower diversity of parasite egg assemblages in the northern Chilean coast may be due to the absence or lower abundance of first intermediate/paratenic hosts of Pseudoterranova.

Ovarian folliculogenesis in the southern sea lion Otaria flavescens

AbstractPalma‐Cerda, F., Di Fiore, M.M., Sepúlveda, M., Duran L.R. and Raucci, F. 2011. Ovarian folliculogenesis in the southern sea lion Otaria flavescens. —Acta Zoologica (Stockholm) 93: 444–452.In Otaria flavescens, folliculogenesis occurs within ovary cortex. This process attains successively higher level of organization through cell proliferation and differentiation. Here, we identified eight major follicular stages from I to VIII, plus corpus luteum and corpus albicans. Otaria folliculogenesis is divided into (1) primordial follicle recruitment; (2) pre‐antral follicle development; (3) growth of antral follicle; and (4) follicle atresia. The primordial follicle is surrounded by thin and flat granulosa cells. As recruitment occurs, granulosa cells organize into cuboidal monolayer marking the transition into pre‐antral phase. Pre‐antral phase (from stage I to stage V) is characterized by follicular growth and theca layer formation. The typical feature of the antral phase (from stage V to pre‐ovulatory Graafian follicle or stage VIII) is the formation of a fluid‐filled cavity (antrum) within the follicle. In the Graafian preovulatory follicle, theca cells organize two distinguishable layers surrounding the follicle. In gravid females, the corpus luteum persists. In nongravid females, the corpus luteum transforms into corpus albicans. The corpus albicans is formed by granulosa, thecal cells, and invading blood tissue. Our results provide a detailed histological description of follicular development in O. flavescens and add new knowledge to the reproductive biology of this species.

Stable isotope analysis reveals pelagic foraging by the Southern sea lion in central Chile

The diet of Southern sea lion Otaria flavescens is poorly known along the coast of central Chile (32°–39°S), where a population of about 17,300 individuals occurs, in an ecosystem that sustains one of the world's most important fishing industries. The primary objective of this study was to reconstruct the diet and estimate Trophic Positions (TPs) of sea lions and their prey off central Chile using stable isotopes ( δ 13C and δ 15N). Our results showed that the diet of sea lions is primarily composed of pelagic prey, with the jack mackerel Trachurus murphyi as the principal prey item in the diet of sea lion (1–99th percentile: 20–66%), while demersal prey accounted for only 0–2.8%. We also found regional differences on the relative contribution of prey to the diet of sea lions. Animals that were sampled close to major fishing areas showed an increase in the relative contribution of jack mackerel to the diet as opposed to animals sampled away from these areas that displayed a relatively more heterogeneous diet. Trophic Positions (TPs) of sea lions prey items ranged between 3.39 for jack mackerel and 4.48 for pink cusk-eel ( Genypterus blacodes). The TP for sea lions was 4.57. Hence, our results showed a community composed by at least 5 trophic levels, with sea lion as the top predator. In summary, our study demonstrates that the Southern sea lion is displaying pelagic foraging off central Chile. We highlight the necessity of conducting further research on the trophic ecology and diving behavior of Southern sea lion to obtain a better understanding of their role as top predator.

Foraging patterns of breeding Dolphin GullsLarus scoresbiiat Punta Tombo, Argentina

The Dolphin GullLarus scoresbiiis a little‐known, rare species endemic to southern South America. Knowledge of its feeding ecology is essential for development of management and conservation strategies. To obtain information on their use of food resources and on the frequency and duration of their foraging trips, we followed seven individuals by radiotelemetry during the breeding season of 2002 at the Punta Tombo Reserve, Argentina. In 99% of mapped locations (n = 4069) the Gulls were within 2.4 km of their colony. Dolphin Gulls foraged mostly at the colonies of three other species, feeding on Magellanic PenguinSpheniscus magellanicusand Imperial CormorantPhalacrocorax atricepsregurgitates and on Southern Sea LionOtaria flavescensfaeces. The sea lion colony was the most frequently visited foraging area, accounting for 64% of the total (n = 260 trips). A similar trend was observed during both the incubation (60%,n = 38 trips) and the chick (64%,n = 40 trips) stages. The mean number of trips per day was 3.8 (range = 3–5), with a mean duration of 123 min (sd = ±27). Trip duration differed between foraging areas, being significantly longer at the sea lion than at the penguin and cormorant colonies. The small foraging range given by its particular feeding strategy suggests that Dolphin Gulls, in contrast to most other seabirds that range over large expanses of ocean in search of food, may be effectively conserved within protected areas during the breeding season.