Dos nuevas especies de pterópodos gimnosomados del Golfo de California (Gymnosomata: Pneumodermatidae)

Two new species of gymnosomatous mollusks from the central portion of the Gulf of California, Mexico are described based on radular characteristics. Pneumoderma cicimarensis sp. nov., has a similar morphology to Pneumoderma atlanticum pacificum (Oken, 1815), but differs in the presence of one lobe on the median portion of the wing, a lack of chromatophores in the body and the shape of the radular teeth. The second species Pneumodermopsis tacoi sp.nov., has a similar radula to Pneumodermopsis ciliata (Gegenbaur, 1855) but differs significantly in the number of rows of the radula and the shape of the central tooth.Se describen dos nuevas especies de moluscos gymnosomatous procedentes de la porción media del Golfo de California, basados en características de la rádula. Pneumoderma cicimarensis sp. nov., presenta una morfología similar a Pneumoderma atlanticum pacificum (Oken, 1815), pero difiere en la presencia de un lóbulo en la porción media del ala, la usencia de cromatóforos en el cuerpo y en la forma de la rádula. La segunda especie Pneumodermopsis tacoi sp. nov., presenta una rádula similar a Pneumodermopsis ciliata (Gegenbaur, 1855), pero difiere considerablemente en el número de filas en la rádula y en la forma del diente central. &nbsp

Larval development of the spotfin tonguefish (Symphurus oligomerus Mahadeva and Munroe, 1990) (Pleuronectiformes: Cynoglossidae) from the Gulf of California, Mexico

Larval and early juvenile stages of Symphurus oligomerus are described from 24 specimens from the Gulf of California. Meristic features were 48 – 49 total vertebrae, 87–94 dorsal-fin rays, 73–77 anal-fin rays, 12 caudal-fin rays, and five hypural bones. Seven larvae and one juvenile were cleared and stained to obtain the pterygiophore formula (1-3-2-2-2) that confirmed the identification of S. oligomerus. The pigment pattern from preflexion to juvenile stage consists of three bands on the dorsal margin and two bands on the ventral margin formed by star-shaped melanophores on the left side of the body. The intestine in preflexion to postflexion larvae forms an abdominal projection that ends in a short conical appendix. The intestine is supported by three cartilaginous struts; larvae with these physical attributes are called exterilium larvae. Preflexion larvae have two elongated dorsal-fin rays, and in flexion to postflexion larvae the second to the fourth dorsalfin rays are elongate. We found an apparent connection between the size at metamorphosis of the species of Symphurus and the depth distribution range of adults such that the fish species that metamorphose at a larger size have a deeper distribution as adults and exterilium larvae seem to correspond to species that have deeper distributions

LISTS OF SPECIES 204 Fish larvae in Bahía Sebastián Vizcaíno and the adjacent oceanic region, Baja California, México

Abstract: The taxonomic composition of the fish larvae assemblage of Bahía Sebastián Vizcaíno and the adjacent oceanic region is presented based on oblique zooplankton hauls made during 12 oceanographic surveys between fall 1997 and fall 2000. In total, 186 taxa representing 71 families were collected. Myctophidae, Phosichthyidae, and Engraulidae were the most abundant during winter and Myctophidae, Merlucciidae, and Bathylagidae during spring. In summer and fall Phosichthyidae and Myctophidae were the most abundant. During 1999 and 2000, seasonal variability was identified in the area by the fish larvae composition, defining winter and fall as a low diversity period and spring and summer as a high diversity period. Interannual variability was detected with an El Niño event, with higher larval abundances of tropical and subtropical taxa, and a La Niña event, with high abundances of larvae of Engraulis mordax

Pastoreo del mesozooplancton sobre el fitoplancton en la Bahía de La Paz, B. C. S., México

During October 2002 a time series was generated to measure the daily grazing rates of mesozooplankton, it was recorded the changes of the chlorophyll a concentration at a station in La Paz Bay, Mexico. The grazing coefficient (g), phytoplankton growth coefficient (k), clearance rate (F), and ingestion rate (I) were estimated as initial reference for the study area. Grazing rates presented values ranging from 0.72-1 to 2.74 ind·d-1; phytoplankton growth coefficient ranked from 0.03 to 0.76 d-1 Clearance rate was from 11.9 to 45.6 ml·ind-1·d-1, and the ingestion rate fluctuated from 5.2 to 18.4 Cla·ind-1·d-1. The mesozooplankton was capable of remove 1.0 to 43 % of potential daily production. The ingestion and clearance rates had similar daily variation pattern along the study; phytoplankton growth coefficient values were lower than grazing rate. The results showed that mesozooplankton might consume about 17% of phytoplankton production in this coastal area. This assessment on mesozooplankton feeding at La Paz Bay is a step to a better understanding of the plankton dynamic in this subtropical area.Durante octubre de 2002 se generó una serie de tiempo para medir la tasa de alimentación diaria del mesozooplancton, estudiando los cambios de la concentración de clorofila a en una estación en la Bahía de La Paz, México. El coeficiente de consumo o tasa de pastoreo (g), el coeficiente de crecimiento de fitoplancton (k), la tasa de aclaramiento del agua (F) y la tasa de ingesta (I) fueron estimados como una referencia inicial para el área de estudio. La tasa de pastoreo tuvo valores entre 0.72-1 y 2.74 ind·d-1; mientras que el coeficiente de crecimiento del fitoplancton fue de 0.03 a 0.76 d-1. La tasa de aclaramiento de agua se determinó entre 11.9 y 45.6 ml·ind-1·d-1 y la tasa de ingesta entre 5.2 y 18.4 Cla·ind-1·d-1. El mesozooplancton pudo remover del 1.0 al 43 % de la producción potencial diaria. Las tasas de aclaramiento y de ingesta tuvieron una variación diaria similar a lo largo del estudio; el coeficiente de crecimiento día a día, fue menor al de pastoreo a lo largo del estudio. Los resultados mostraron que el mesozooplancton puede consumir alrededor del 17% de la producción diaria de fitoplancton en la zona estudiada. Esta primera aproximación sobre la alimentación del mesozooplancton en la bahía de La Paz, permite una mayor comprensión de la dinámica planctónica en esta área subtropical

Variación estacional de la producción de huevos del copépodo calanoideo Centropages furcatus (Dana, 1852) en la Bahía de La Paz, México

The egg production rate (EPR) was estimated for Centropages furcatus in Bahia de La Paz, Baja California Sur, Mexico during 2003. This species is one of the most abundant and frequent copepod in the zone. The highest egg production in carbon estimations for C. furcatus were observed in summer (1.20 ± 0.7 µg C female-1 d-1) and the lowest was found during spring (0.58 ± 0.42 µg C female-1 d-1). The longest prosome length (PL) was registered in summer (1.15 ± 0.05 mm) and the shorter during autumn (1.01 ± 0.04 mm). No significant correlation was found in a daily base between EPR and PL with chlorophyll a (Chl a) concentration neither the sea surface temperature (SST). In temporal scale, in winter, spring and summer the SST was low (<23.2°C) in contrast, autumn presented high SST (>27 °C). Chl a was low (<1 mg m-3) in winter, spring and autumn, whereas in summer it was high (>3 mg m-3). Although the correlation was non significant between the biological parameters and the environmental variables (p> 0.05), the species showed high values of LP and TPH in summer when SST were low and the concentration of Chl a was high.Se estimó la tasa de producción de huevos (TPH) para Centropages furcatus en la Bahía de la Paz, Baja California Sur, México, durante 2003. Esta especie es una de las más abundantes y frecuentes de los copépodos en la zona. La estimación en carbono de la producción de huevos fue máxima en verano (1.20 ± 0.7 µg C hembra-1 d-1) y mínima en primavera (0.58 ± 0.42 µg C hembra-1 d-1). La mayor longitud del prosoma (LP) fue registrada en verano (1.15 ± 0.05 mm) y la menor en otoño (1.01 ± 0.04 mm). No hubo correlación significativa entre LP y TPH con la concentración de clorofila a (Cl a) ni con la temperatura superficial del mar (TSM). En invierno, primavera y verano la TSM fue menor a 23.2 °C, a diferencia de otoño que presentó TSM mayores a 27 °C. En relación a la Cl a, tanto en invierno, primavera y otoño los valores fueron menores a 1 mg m-3, mientras que en verano fueron mayores a 3 mg m-3. Aunque la correlación no fue significativa (p >0.05) entre los parámetros biológicos y las variables ambientales, la especie presentó valores altos de LP y TPH en verano cuando la TSM fue baja y la concentración de Cl a fue la más alta

Cambios diarios en la composición y abundancia de copépodos planctónicos al sur de Bahía de La Paz (Octubre 2002)

The goal of this work to analyze the changes in the copepods community, and its relationships with the sea temperature, chl-a concentration and tidal level south of Bahía de La Paz during October 2002. The statistical analysis split the study period with different communities. During the first phase, the oceanic and neritic-oceanic species were dominant (e.g. Labidocera acutifrons, L. acuta, L. diandra, and L. trispinosa), whereas during the second period an increase of the abundance and species richness of coastal and estuarine species was measured (e.g. Acartia lilljeborgii, A. clausi, Nannocalanus minor, and Canthocalanus pauper). These changes were mainly associated with changes in the tide level with respect to de mean sea level as well as with the chlorophyll-a concentration.El objetivo de este trabajo fue analizar los cambios de la comunidad de copépodos y su relación con la temperatura del mar, concentración de Cl a y la altura de la marea al sur de Bahía de La Paz durante octubre del 2002. El análisis estadístico dividió el periodo de estudio en dos etapas con distintas comunidades. En la primera etapa dominaron especies oceánicas y neríticooceánicas (Ej. Labidocera acutifrons, L. acuta, L. diandra, L. trispinosa), y en la segunda se incrementó la abundancia y número de especies costeras y lagunares (Ej. Acartia lilljeborgii, A. clausi, Nannocalanus minor y Canthocalanus pauper). Estos cambios, se asociaron principalmente a cambios en la altura de la marea con respecto al nivel medio del mar y a incrementos en la concentración de Cl a

Grupos de larvas de peces recurrentes en la Costa Occidental de Baja California Sur y región central del Golfo de California.

impreso y digita