María Teresa González

Similascarophis n. gen. n. spp. (Nematoda: Cystidicolidae) parasitizing marine fishes off the Chilean coast.

Similascarophis (Cystidicolidae) n. gen. is proposed. In the mouth of specimens of this genus, submedial labia are absent and pseudolabia do not have any part projecting toward the central oral opening. These nematodes were obtained from the alimentary tract of 7 marine fish species along the coast of Chile: Bovichthys chilensis Regan, Eleginops maclovinus (Cuvier), Pinguipes chilensis (Valenciennes), Cilus gilberti (Abbott), Cheilodactylus variegatus Valenciennes, Girella laevifrons (Tschudi), and Graus nigra Philippi. Morphology and morphometry are compared between 2 new Similascarophis species: Similascarophis maulensis n. sp. and S. chilensis n. sp., which differ in the presence of sublabia and in the length of the glandular esophagus and left spicule. We also recorded Similascarophis sp. in 2 other host species, which showed some distinct proportional measurements, although these differences were not sufficiently clear to identify them as a new species.

Biogeographic patterns of metazoan parasites of the bigeye flounder, Hippoglossina macrops, in the southeastern Pacific coast.

We examined the metazoan parasite fauna of the bigeye flounder, Hippoglossina macrops, in a latitudinal gradient of the southeastern Pacific (ca. 25°S–33°S) to assess whether their parasites show latitudinal and/or biogeographical patterns, and to determine if these patterns agree well with those observed for free-living organisms. In total, 331 fish from 6 localities were analyzed. Eighteen parasite species, including 5 ecto- and 13 endoparasites, were found in the bigeye flounder. Neoheterobothrium chilensis, Floridosentis sp., and Corynosoma australe were the most prevalent parasite species. Ecto- and endoparasites of H. macrops showed different latitudinal patterns. Only endoparasite species show a distributional pattern concordant with biogeographic areas recognized for free-living organisms; this finding was supported by cluster analyses showing 2 major divisions. The first joined the most northern localities (25°S–26°S), and the second consisted of 2 subgroups: (1) 28°S–30°S, and (2) 31°S– 32°S. A multivariate analysis of infracommunities showed significant differences in the parasitic load of H. macrops from different latitudes. The latitudinal differences in the prevalence and abundance of the parasites might be explained by differing oceanographic conditions in water masses. These physical conditions could affect the dispersal ability of the infective stages of ectoparasites, and produce zoogeographical breaks that could affect the distribution of intermediate hosts (invertebrate and vertebrate prey), subsequently affecting the transmission of endoparasites.

Hermaphroditism in Marine Mussel Perumytilus purpuratus (Lamarck, 1819), (Mollusca: Mytilidae)

Los bivalvos marinos son principalmente especies gonocoricas. Sin embargo, ocasionales especimenes hermafroditas pueden encontrarse. Una descripcion histologica de dos (de 179) especimenes hermafroditas del chorito Perumytilus purpuratus (Lamarck, 1819) es registrada, los que fueron colectados en la bahia de San Jorge (24S). La baja proporcion de hermafroditas de Perumytilus purpuratus sugiere que podria ser un fenomeno accidental, aun asi otras posibles causas son discutidas en el presente estudio.

TWO NEW SPECIES OF ENCOTYLLABE (MONOGENEA: CAPSALIDAE) BASED ON MORPHOMETRIC AND MOLECULAR EVIDENCE: PARASITES OF TWO INSHORE FISH SPECIES OF NORTHERN CHILE

Abstract:  Two new species, Encotyllabe cheilodactyli and Encotyllabe antofagastensis (Monogenea: Capsalidae), have been found in the pharyngeal plates of Cheilodactylus variegatus and Anisotremus scapularis, respectively, in northern Chile (23°38′N, 70°24′W). Descriptions of the new species were based on morphometric and molecular evidence. Both species differ from previously described species of the genus by a combination of characteristics, including the size and relative position of the testes and the shapes of the major and small hamulus. In addition, E. cheilodactyli is unique among the known species of Encotyllabe due to the testes crossing the equatorial line of the body proper, and E. antofagastensis is unique among the known species of Encotyllabe due to its penis structure and anatomy leading to the genital pore. The analysis of the cytochrome c oxidase I gene as well as morphometric analyses demonstrated that the specimens belonged to 2 different species.

Seasonal variation in fish bycatch associated with an artisanal flounder fishery on Coquimbo Bay, Chile

Seasonal bycatch composition of the flounder gillnet fishery in the Coquimbo Bay, between October 2006 and November 2007 was analyzed. Landed species were identified and weighted (kg). These data set was used to estimate the relative importance of weight and frequency of occurrence of each species in relation to the total catch. To evaluate the seasonal variation of landed species, we performed cluster analyses (based on frequency of occurrence, mean weight, CPUE), and correspondence analysis (frequency of occurrence; CPUE). Thirty-two species were recorded as bycatch, being the most frequent species, the Chondrichthyan, Callorhinchus callorhynchus, Squatina armata and Mustelus mento. Paralichthys spp., C. callorhynchus, M. mento, Myliobatis chilensis, S. armata and Thyrsites atun, were strongly associated with spring and summer seasons; while Sciaena deliciosa and Merluccius gayi were associated with winter and autumn.

Determining Intermediate Hosts for Opecoelidae and Microphallidae Species (Platyhelminthes: Trematoda) in the Southeastern Pacific Coast, Using Molecular Markers

Abstract Metacercarial stages of digeneans were collected from decapod crustaceans inhabiting intertidal rocky zones in central Chile. The digeneans were identified through a molecular analysis based on the V4 region of the 18S ribosomal RNA gene. We analyzed 356 crustaceans belonging to 10 species, 115 intertidal fish belonging to 6 species, and 4 specimens of 1 coastal bird species. In total, 74.1% of crustaceans were parasitized with metacercariae. We found 1 species of Opecoelidae. This species showed low genetic divergence (0% and 0.1%) with adult digeneans found in intertidal fish and with the species Helicometrina labrisomi infesting a subtidal fish from northern Chile (Labrisomus philippii). Additionally, we found 2 species of Microphallidae, 1 closely related to Maritrema (1.3% genetic distance) and the other related to Microphallus (5% genetic distance). Therefore, our findings showed that the decapod crustaceans are relevant hosts in food webs from the southeastern Pacific coast. Furthermore, we found 5 species of crustaceans as second intermediate hosts for H. labrisomi and 2 species as secondary intermediate hosts for 2 Microphallidae, which contribute to elucidate parts of their life cycles through molecular markers and extended the host distribution of H. labrisomi in the southeastern Pacific coast.

Sexual Differentiation and size at First Maturity of the Mussel Choromytilus chorus (Molina, 1782) (Mollusca, Bivalvia) in Northern Chile.

Abstract: The mussel Choromytilus chorus (Molina, 1782) is a commercially and ecologically important bivalve, which is extensively distributed along the Chilean coast (20°S–54°S). However, there are no previous studies regarding the reproductive aspects of this species in the northern part of its range. Mussels were collected at Caleta Errázuriz, along the Antofagasta coast (ca. 24°S), between December 2014 and June 2015. A total of 1620 individuals were examined using histological techniques and macroscopic visual inspection. Seventeen size categories, which included individuals from 5 mm to 100 mm in length, were analyzed. The size at the onset of sexual differentiation and the size at first sexual maturity (50% mature individuals) were determined. Males comprised 49% of the total sample, and 51% were females. Mussels from 5–22 mm in valve length were undifferentiated and from 22–24 mm were sexually differentiated. The size at first sexual maturity was recorded as 38–40 mm. In vitro fertilization trials demonstrated that sexually differentiated individuals were able to produce viable gametes. The biological parameters analyzed for C. chorus were similar to those recorded for populations of this bivalve from the southern latitudes. However, the lower number of eggs per female and the smaller egg size suggests that the population parameters may be different for C. chorus between the northern and southern latitudes.

Report of pathogens and parasites in Perumytilus purpuratus from San Jorge Bay, Antofagasta, Chile

Perumytilus purpuratus is a mussel commonly found on the entire Chilean coastline. The knowledge of pathogens and parasites of this mollusc, as well as for many other species, inhabiting the Chilean coast remains largely unknown. This study aims to survey parasites and pathogens in P. purpuratus from San Jorge Bay, Antofagasta, Chile. From September to October 2009, 160 specimens of this bivalve were collected. Ciliates, virus-like, rickettsia-like organisms (RLO) and digeneans were recorded. The most prevalent parasites were metacercariae of digeneans in gonads (50.83%), gill ciliates (37.5%), and digestive gland viruses-like (37.5%). Only the prevalence of digeneans increased with host size, but any relationship between these variables was found in the other pathogens.