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Neuromast morphology and distribution are characterized during early ontogeny of anchoveta (Engraulis ringens) and common sardine (Strangomera bentincki). Although both species share morphological features, they show several differences during their early ontogeny, such as size at hatching and yolk absorption. Larvae were obtained from incubation of planktonic eggs (at 12°C), collected during the spawning season 2001 (August-September) at Coliumo Bay. The neuromasts were observed from hatching to 25 days, and the pattern of neuromast appearance, in newly hatched larva, until yolk absorption, was determined using Janus Green staining and scanning electronic microscope. Results showed a similar pattern of neuromast development in both species. At hatching, two pairs of neuromasts were observed in the cephalic area and 8-9 in the rest of the body, which increased to 19 pairs and to 30-39 pairs at a larval size of 11 mm, respectively. On the average, 12 hair cells per neuromast were counted, with little variation among neuromasts. The polarity of these hair cells was closest to multiple polarity. Neuromast positioning for both species, anchoveta and common sardine larvae, are similar to those of Engraulis mordax and Clupea harengus, respectively. The similar development pattern of these species seems to be related to similar functional constraints and close taxonomic affinity. Se caracteriza la distribución y morfología de los neuromastos en la ontogenia temprana de la anchoveta (Engraulis ringens) y sardina común (Strangomera bentincki). Aunque ambas especies comparten varias características morfológicas, muestran diferencias durante la ontogenia temprana, tales como tamaño a la eclosión y absorción de vitelo. Las larvas fueron obtenidas desde la incubación de huevos planctónicos a 12°C, recolectados en la bahía Coliumo durante la estación reproductiva 2001 (agosto-septiembre). Los neuromastos fueron observados desde la eclosión hasta los 25 días posteriores, usando la tinción vital de verde de Jano y microscopía electrónica de barrido. Los resultados muestran un patrón similar de desarrollo en ambas especies. A la eclosión se observaron 2 pares de neuromastos en la región cefálica y entre 8 y 9 en el resto del cuerpo, que a la longitud de 11 mm aumentan a 19 y entre 30 y 39 pares respectivamente. En promedio, se contabilizaron 12 células ciliadas por neuromasto con escasa variación entre neuromastos, con una polaridad cercana a la polaridad múltiple. La posición de los neuromastos de ambas especies, anchoveta y sardina, fueron similares a las descritas para Engraulis mordax y Clupea harengus, respectivamente. El patrón similar de desarrollo de estas especies parece relacionado con sus restricciones funcionales y estrecha afinidad taxonómica.

This communication informs that presence of the Chilean mussel, Mytilus chilensis (Hupe 1854) in the coast of the Bay of Concepcion (Chile) reported in the scientific literature is an erroneous identification, being Mytilus galloprovincialis (Lamarck 1819) the right species. Esta comunicación informa que la presencia de Mytilus chilensis (Hupe 1854) citada en la literatura científica para la costa de la Bahía de Concepción (Chile) no es correcta, siendo Mytilus galloprovincialis (Lamarck 1819) la identificación taxonómica válida.

El presente estudio analiza la distribución espacial y variabilidad temporal de huevos y larvas de Strangomera bentincki y Engraulis ringens en los periodos de desove principal y secundario, en la zona adyacente a la desembocadura del río Itata, Chile. La información se obtuvo de 7 cruceros oceanográficos entre 1996 a 2005. Se analizó la abundancia y distribución espacial de huevos y larvas en preflexión para ambas especies y la magnitud de las variaciones en su abundancia. Los resultados mostraron que huevos de ambas especies tienden a concentrarse en la costa. La cobertura espacial de larvas en preflexión es mayor que en huevos, en dirección costa-océano. La distribución de los estadios tempranos de sardina común y anchoveta en la plataforma continental frente a la desembocadura el Río Itata fueron variables inter-anualmente. La variación de abundancia entre años fue mayor para huevos que para larvas en ambas especies siendo mayor en los huevos que en las larvas. Las mayores abundancias de huevos y larvas de anchoveta y sardina común se encontraron en salinidades entre los 32 psu y 34 psu, sin embargo, en ocasiones (año 2005) fue posible observar agrupaciones en salinidades menores (20 a 24 psu) en la zona adyacente a la desembocadura del río Itata. El área inmediatamente adyacente a la desembocadura, sin embargo, presentó bajas abundancias de huevos y larvas de estas especies durante los periodos estudiados. This study assesses the spatial and temporal variations in eggs and larval distributions of Engraulis ringens and Strangomera bentincki during their peak and secondary spawning periods, in the zone adjacent to the Itata River mouth, Chile. The information on abundance and distribution of the early life stages of both fish species was obtained from seven oceanographic cruises performed out between 1996 and 2005. The abundance and distribution of eggs and preflexión larvae of both species and, in order to detect potential variations in abundance was analyzed. Our results showed that eggs of both species tended to aggregate at the coast. The spatial extensions of preflexion larvae were broader than that of eggs of both species, along a coast- to- ocean direction. The distribution of the early life stages of both species over the continental shelf off the Itata River mouth was variable inter-annually. These egg and larval abundances showed significant variations among years and the eggs abundance was higher than of larvae. The highest egg and larval abundances occurred at salinities between 32 psu and 34 psu. However, occasionally it was possible to find aggregations in lower salinities (20-24 psu) in the nearby zone of the Itata river mouth. The area contiguous to the river mouth, however, showed low abundance of egg and larvae during the period studied.

To describe and quantify morphological abnormalities during the embryonic development of Strangomera bentincki an area nearby the Itata River mouth was sampled during the reproductive season 2007. Abnormality levels (3-13 %) were coincident with reported levels for other Clupeids species inhabiting areas with similar environmental characteristics to the area studied. Type and abnormalities prevalence were coincident with those reported for other fish species. Blastopore irregular closing and the embryonic axis twist were the most frequent in the samples. These abnormality types would be caused by errors during the epiboly, which can occur spontaneously, influenced by internal or external factors.

The feeding behaviour of larvae of four Clupeiform fish species (Sardinops sagax, Strangomera bentincki, Ethmidium maculatum and Engraulis ringens) was studied using specimens collected from September to November 1987 in Concepcion Bay, Chile. The indices of food preference (α) of Chesson, of diet overlap (D) of Schoener and (L) of Hurlbert, were used. Similar feeding patterns were found in the larvae of the four species. The diet included several developmental stages of copepods: eggs, nauplii and copepodites. The larvae of Engraulis ringens showed an early euriphagy. There were no significant differences in food preference between the species, except for Ethmidium maculatum, which showed a high preference for eggs, even at larger larval sizes. A general trend for preference for larger prey as larvae grow is displayed by the other species. No significant difference was found between sampling periods. A high level of diet overlap was found, regardless of the index used to estimate it.

DOCTOR EN CIENCIAS BIOLOGICAS FONDECYT FONDECYT