Phylogenetic relationship between Contracaecum spp. (Nematoda, Anisakidae) parasitizing cormorants (Aves, Phalacrocoracidae) in Argentina.

Species of the genus Contracaecum (Family Anisakidae) exhibit a broad host and geographical distribution, parasitizing aquatic organisms such as piscivorous birds and mammals as their definitive hosts. Several Contracaecum species have been reported parasitizing cormorants (Family: Phalacrocoracidae) in South America. The objective of this study was to highlight phylogenetic relationships between Contracaecum species parasitizing cormorants based on both molecular analyses and the papillae arrangement on the male tail. Some Contracaecum species parasitizing Red-legged cormorants from the Ría Deseado (RD), and other nematodes parasitizing eight Neotropic cormorants from San Miguel del Monte lagoon (SMML), Argentina, were collected and analyzed. Both morphological and phylogenetic analyses allowed us to recognize two species: Contracaecum chubutensis parasitizing Phalacrocorax gaimardi, and Contracaecum australe parasitic in Phalacrocorax brasilianus. According to the obtained sequences (mtDNA cox2, ITS1, ITS2, and SSrRNA), Contracaecum sp. parasitizing P. gaimardi exhibited concordance with the previously reported C. chubutensis parasitizing P. atriceps from Bahía Bustamante, Chubut province. Likewise, Contracaecum sp. isolates parasitizing P. brasilianus showed concordance with C. australe from Chile. Besides, the papillae arrangement on the male tail allowed us to understand the interspecific and genetic relationships between the Contracaecum species. The analyses confirm that C. chubutensis specimens parasitizing P. gaimardi from RD present a new host record for the species, whereas, those C. australe specimens parasitizing P. brasilianus from SMML provide a new geographical record for the species and the extension of its distribution range. Present results also confirm the inland and marine distribution of C. australe and C. chubutensis, respectively.

Metapopulation dynamics and foraging plasticity in a highly vagile seabird, the southern rockhopper penguin.

Population connectivity is driven by individual dispersal potential and modulated by natal philopatry. In seabirds, high vagility facilitates dispersal yet philopatry is also common, with foraging area overlap often correlated with population connectivity. We assess the interplay between these processes by studying past and current connectivity and foraging niche overlap among southern rockhopper penguin colonies of the coast of southern South America using genomic and stable isotope analyses. We found two distinct genetic clusters and detected low admixture between northern and southern colonies. Stable isotope analysis indicated niche variability between colonies, with Malvinas/Falklands colonies encompassing the species entire isotopic foraging niche, while the remaining colonies had smaller, nonoverlapping niches. A recently founded colony in continental Patagonia differed in isotopic niche width and position with Malvinas/Falklands colonies, its genetically identified founder population, suggesting the exploitation of novel foraging areas and/or prey items. Additionally, dispersing individuals found dead across the Patagonian shore in an unusual mortality event were also assigned to the northern cluster, suggesting northern individuals reach southern localities, but do not breed in these colonies. Facilitated by variability in foraging strategies, and especially during unfavorable conditions, the number of dispersing individuals may increase and enhance the probability of founding new colonies. Metapopulation demographic dynamics in seabirds should account for interannual variability in dispersal behavior and pay special attention to extreme climatic events, classically related to negative effects on population trends.