The metazoan parasites of four populations of the chub mackerel Scomber japonicus were analysed from two localities in the Atlantic Ocean (Madeira Islands, Portugal, and Rio de Janeiro, Brazil) and two localities in the Pacific Ocean (Callao, Peru, and Antofagasta, Chile), collected during 2002 and 2003. A total of 373 fish specimens were studied and 34 metazoan parasite species were obtained. Parasites identified from the populations of chub mackerel studied could be separated into three categories: parasites with a wide distribution, present in the Pacific and Atlantic, parasites proper of the Pacific Ocean and parasites proper of the Atlantic Ocean. The analyses of some highly specific parasites of the genus Scomber (i.e. monogeneans of the genus Kuhnia and didymozoid digeneans) strongly suggest the need for a revision of the taxonomic status of chub mackerels from the Atlantic and Pacific coast of America. The results demonstrated the usefulness of parasites as adequate tools to clarify the taxonomic status of their hosts.
The aims of the present study were to compare, using multivariate analyses, the degree of similarity of the endoparasite fauna of five fish species belonging to the order Gadiformes: Merluccius gayi, Merluccius australis, Macruronus magellanicus (Gadoidei) and Micromesistius australis and Nezumia pulchella (Macrouroidei), from the southern and central Chilean coast, and to evaluate whether the composition of the endoparasite fauna was determined by phylogenetic or ecological relationships. We employed our database of Merluccius australis, M. magellanicus and Micromesistius australis, which was complemented with published information for M. magellanicus, Merluccius australis, Micromesistius australis, M. gayi and N. pulchella. A higher number of endoparasite species was recorded for Merluccius australis, Micromesistius australis and M. magellanicus, namely Anisakis sp. and Hepatoxylon trichiuri, which is the most prevalent parasite among these hosts. Aporocotyle wilhelmi and Hysterothylacium sp. were detected only in M. gayi, whereas Lepidapedon sp. was found exclusively in N. pulchella. These results suggest that fish ecology rather than host phylogeny was the most important factor for the determination of similarity in parasite composition. This result could be explained by the similar trophic patterns of hosts and by the predominance of generalist larval species among these fish parasite communities.
The mussel Perumitylus purpuratus has been described as the first intermediate host for the digenea Proctoeces lintoni (Fellodistomidae) in the Chilean coast. The study of more than 3000 specimens of P. purpuratus, taken off northern Chile revealed the absence of sporocysts. Experimental infection of mussels with eggs obtained from the known host for P. lintoni was unsuccessful. We analyze the V4 region of the SSU rRNA of living sporocysts and cercariae obtained from P. purpuratus from central Chile in order to confirm the proposed life cycle for this digenea. Our results demonstrated that sporocysts and cercariae obtained from P. purpuratus do not belong to P. lintoni but to an undescribed digenea from the Chilean coast.
Females in numerous rodent species engage in communal nesting and breeding, in which they share one or more nests to rear their young. A potential cost of communal nesting and breeding is that mothers divert resources to unrelated offspring. One way mothers could avoid this cost is to recognize and favour their own young over unrelated offspring when allocating maternal effort. We assessed whether female degus (Octodon degus), a communally nesting and breeding caviomorph rodent, discriminate between their own and unrelated offspring during lactation. Female degus previously have been shown to distinguish between their own and unrelated pups when exposed to odours from both. We measured pup discrimination based on differences in the retrieval behaviour of females that were in early or intermediate lactation directed towards their own and unrelated offspring; offspring presented were of similar or different age. Before any event of pup retrieval, lactating females spent similar amounts of time and interacted to a similar extent with their own and unrelated pups. During pup retrieval, all lactating females transported both pups to the nest. Neither relatedness to pups, nor pup‐age differences, influenced the order in which pups were retrieved to the nest. Dams waited similar amounts of time before retrieving the first pup when the first transported young was their own or unrelated. Likewise, females waited similar amounts of time before retrieving the second pup when the pup transported first was their own or unrelated. The time between first and second pup transport events was longer when dams were in early when compared with intermediate lactation, but only when pups were of similar age. All experimental subjects nursed unrelated pups after they were retrieved. Collectively, our results do not support the hypothesis that communally breeding female degus use their recognition ability to discriminate against unrelated offspring in favour of their own young.
The value of the metazoan parasites of the anchoveta Engraulis ringens as biological tags for stock discrimination is assessed. Three hundred and fifty-nine specimens, obtained from six landing ports in northern and central Chile (Arica, Antofagasta, Caldera, Coquimbo, Valparaiso and Talcahuano) covering a latitudinal gradient of c. 18°, were analysed. Six metazoan parasite species (three ectoparasites and three endoparasites) were obtained. A correspondence analysis suggested that anchoveta from northern and central Chile are comprised of two stocks. Identification of stocks was largely based on qualitative differences (absence in southern localities of the monogenean Pseudanthocotyloides heterocotyle, a parasite proper of engraulids, and the copepod Caligus sp.) and quantitative differences in the prevalence of infection for the remaining species. Inertia and mass value for the correspondence analysis supported the hypothesis of two stocks.
Two species of Proctoeces Odhner, 1911 have been described in marine organisms from Chile: P. humboldti George-Nascimento & Quiroga (1983), parasitizing the gonads of keyhole limpets (Fissurella spp.), and P. chilensis Oliva (1984), an intestinal parasite of Sicyases sanguineus (Teleostei); both species were subsequently considered as P. lintoni Siddiqi & Cable (1960). To assist in the resolution of the taxonomic identification of Proctoeces species in marine organisms from Chile, phylogenetic studies using DNA sequences from the V4 region of the SSU rRNA gene were performed. Several specimens of P. lintoni were isolated from keyhole limpets (Fissurella spp.) and clingfish (S. sanguineus) from Bahia San Jorge (23°40'S) and Bahia Concepción (36°50'S). Phylogenetic analyses were conducted using three different approaches: a neighbour-joining (NJ), a maximum likelihood (ML) and Bayesian inference (BI). The phylogenetic analysis confirms that specimens of Proctoeces obtained from keyhole limpets and those specimens from the clingfish are in fact the same species. We prefer to consider our specimens as Proctoeces cf. lintoni, as the morphology of Proctoeces appears to be of doubtful value and genetic information about P. lintoni Siddiqi & Cable (1960) is not available. In addition, our results strongly suggest that there are at least three species in this genus.
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