Dr. George-Nascimento-Failla, Mario

We assessed compositional and aggregate properties of fish assemblages inhabiting rocky intertidal pools of the coast of central Chile. Its association to sampling regions, localities, tidepool volume or dominant substrate was examined. A total of 1502 individual fish representing 20 species were collected in 49 single-time sampled tidepools from 3 localities at Valparaíso and 5 from the Biobío region. The dissimilarity in composition of the fish assemblages was larger between regions than among localities within regions. The most abundant taxa in Valparaíso were Helcogrammoides chilensis and Scartichthys viridis. In Biobío were Calliclinus geniguttatus, Gobiesox marmoratus, Myxodes viridis and Ophiogobius jenynsi. There were significant and positive but not strong correlations between the volume of tidepools with the total fish number and species richness. There were no significant correlations with dominance, diversity and total fish biomass. Consequently, density in biomass, density in number of fishes, and in number of species decreased similarly and steeply with tidepool volume in Valparaíso and Biobío regions, indicating a strong size effect of tidepool volume in both regions. These results indicate that community composition variability is independent of aggregate community and that a biogeographical compositional transition occurs in this area.

Notothen fishes (Nototheniidae) have been recorded on the coasts of South America, from 35°S to southern. Little is known about the biology of intertidal notothen fishes or their relationships with other species, including parasites. Here, we analyzed the parasitic fauna of a species of Notothenia collected from the rocky intertidal of Lebu, south-central Chile (36°S) and compared the parasite community of this host with other 9 fish species commonly found in rocky intertidal pools. Among the tested species, Notothenia sp. had the highest parasite richness (21 parasitic taxa vs. 1 to 9 parasitic taxa). The composition of parasite species was different among fishes, with similarity indices between 0 and 33%. The parasite composition of Notothenia sp. was most similar to Calliclinus geniguttatus (27%). The most abundant and prevalent parasites found in Notothenia sp. were the copepod Caligus cf. cheilodactyli, Tetraphyllidea larvae, anisakid nematodes, and several acanthocephalan species, which are typical of other fish from the subtidal and bento-demersal zones. Therefore, we conclude that the juveniles of Notothenia sp. were a few months old and had their parasites when reaching the intertidal zone, acquired some generalist parasites during their stay in this habitat, such as Holobomolochus chilensis and Lecithaster macrocotyle. Most notothen fishes are from Antarctic and Sub-Antarctic waters, therefore, it is possible that this fish came from another habitat but also from the austral region of South America. Notothenia sp. could not be specifically identified because of different results between morphological and genetic analyses.

The most studied digenean of marine organisms in Chile is by far Proctoeces humboldti, a parasite of the intestine of the clingfish Sicyases sanguineus and gonad of the keyhole limpet Fissurella spp. (progenetic metacercariae). The mussel Perumytilus purpuratus has been suggested as the first intermediate host for this digenean. In a study examining the parasites of S. sanguineus from central Chile, we found specimens of Proctoeces showing significant morphological differences with P. humboldti. To assist in the resolution of the taxonomic identification of these specimens, as well sporocysts obtained from the mussel P. purpuratus from central and northern Chile, phylogenetic studies using DNA sequences from the SSU rRNA, as well the LSU rRNA and Cox 1 gene were performed. Results showed that the clingfish S. sanguineus is a host for two species of Proctoeces (P. humboldti and P. syciases n. sp.) along the northern and central Chilean coast, without geographic separation; the mussel P. purpuratus is the first intermediate host for P. syciases n. sp. but not for P. humboldti in central and northern Chile. Fissurellids (Archaeogastropoda) along the Chilean coast harbor only progenetic stages of P. humboldti, but there is no evidence of progenesis for P. syciases. The reinstatement of Proctoeces humboldti is strongly suggested.