Abstract: The Chilean jack mackerel Trachurus murphyi support an important fishery in the South-eastern Pacific Ocean and has declined considerably over time. T. murphyi have asynchronous ovarian development with an oceanic spawning (September to January). Despite the economic importance of this resource critical issue such as characteristics and dynamics of atresia, which affect the reproductive output, are unknown. Females of T. murphyi caught in different spawning seasons were analysed to describe patterns of prevalence and intensity of atresia. General linear models (GLM) were performed by using prevalence and intensity atresia as response variables and gonadosomatic index, condition factor, sea surface temperature, postovulatory follicles and month/year as explanatory variables. The batch fecundity and relative fecundity were compared between females showing atresia, postovulatory follicles and non-atretic females. The stages of atresia identified were alpha, beta and gamma. The GLM showed that variations in the prevalence and intensity of atresia were explained for all variables, except condition factor for prevalence, and gonadosomatic index for intensity of atresia. According to our results, the dynamic of alpha and beta atresia could be considered a potential proxy for any disruption of spawning season. The batch fecundity and relative fecundity were lowest compared with other Trachurus spp. This is the first assessment comparing fecundity between atretic and not atretic females for this species.

Resumen: El jurel, Trachurus murphyi sustenta una importante pesquería en el Pacífico sureste la que ha declinado considerablemente en el tiempo. T. murphyi tiene un desarrollo ovárico asincrónico con desoves oceánicos (septiembre a enero). A pesar de la importancia económica de este recurso, se desconocen aspectos críticos de su biología, como las características y la dinámica de la atresia, que pueden afectar el rendimiento reproductivo. Hembras de T. murphyi capturadas en distintas estaciones de desove fueron analizadas para describir los patrones de prevalencia e intensidad de atresia. Se realizaron modelos lineales generales (GLM) usando prevalencia e intensidad de atresia como variables de respuesta e índice gonadosomático, factor de condición, temperatura de la superficie del mar, folículos postovulatorios y mes/año como variables predictoras. La fecundidad parcial y la fecundidad relativa se compararon entre hembras con atresia, hembras con folículos postovulatorios y hembras no atrésicas. Las etapas de atresia identificadas fueron alfa, beta y gamma. El GLM mostró que las variaciones en la prevalencia e intensidad de la atresia fueron explicadas por todas las variables, excepto el factor de condición para la prevalencia y el índice gonadosomático para la intensidad de atresia. De acuerdo con estos resultados, la dinámica de alfa y beta atresia pueden considerarse un potencial proxy para cualquier interrupción de la temporada de desove. La fecundidad parcial y la fecundidad relativa fueron más bajas en comparación con otros Trachurus spp. En esta especie, se hace una primera evaluación que compara la fecundidad entre hembras con y sin atresia.

Five species of monogeneans collected from marine fishes of the Pacific coast of Chile and Perú were studied. Three of them are new species: Interniloculus chilensis n. sp. (Capsalidae), Neoheterobothrium insalaris n. sp. (Diclidophoridae) and Loxura peruensis n. sp. (Axinidae) parasitic on Sebastes capensis (Scorpaenidae), Paralichthys sp. (Bothiidae) and Belone scapularis (Belonidae), respectively. Two new combinations are proposed, Intracotyle neghmei (Microcotylidae) for Neobivagina neghmei Villalba, 1987 and Hargicotlyle conceptionensis (Diclidophoridae) for Choricotyle conceptionensis Villalba, 1987.

Specimens of Fissurella crassa (Archaeogastropoda) from Ilo, southern Perú, are infected with the adult stage of the digenetic trematode Proctoeces lintoni (Fellodistomidae). The histopatological analysis of the male and female gonads show a strong effect of the parasite on the structure and function of these organs. P. lintoni live unencysted in the gonads, and the main mechanical damage is originated by the action of a well developed acetabulum. Chemical actions of parasitic secretions may also be involved. The infected gonads show altered structure and the gametogenic processes is aborted. There is no evidence of hemocytic response, but leucocite infiltration is evident at least in male infected gonads. An increased content of polysaccarides is evident in infected gonads.

A quantitative and qualitative analysis of the parasite fauna of the sciaenid Stellifer minor (Tschudi) from Chorrillos, Peru, was made. Some characteristics of the infectious processes, in terms of intensity and prevalence of infection, as a function of host sex and size, are given. Moreover, comments on the characteristics of the parasite fauna, related with host role in the marine food webs are included. The parasite fauna of Stellifer minor taken of Chorrillos, Peru, include the monogeneans Pedocotyle annakohni, Pedocotyle bravoi, Rhamnocercus sp. and Cynoscionicola sp., the digenean Helicometra fasciata, the adult acantocephalan Rhadinorhynchus sp. and the larval Corynosoma sp., the nematode Procamallanus sp., the copepods Caligus quadratus, Clavellotis dilatata and Bomolochus peruensis and one unidentified isopod of the family Cymothoidae. A distinctive characteristic of the parasite fauna (Metazoa) of S. minor is the almost absence of larval forms.

The presence of three aspidocotyleans trematodes in marine fishes from Perú and Chile is reported. One of them, Lobatostoma veranoi from the intestine of Menticirrhus ophicephalu (Sciaenidae) is considered a new species. Distinct characteristcs of the new species are:a cirrus sac smaller than the pharynx; tail overlapping posteriorly the ventral disk; testis in the last third of the body and the presence of 64-66 marginal alveoli. The two other species are Lobatostoma pacificum Manter, 1940 found in Trachinotus paitensis Cuvier, 1830 from Perú and Chile and Lobatostoma Anisotremum Oliva & Carvajal, 1984 from the intestine of Anisotremus scapularis (Tschudi, 1844) from Perú.