Abstract.-The distribution and abundance of Octopus bimaculatus paralarvae and juveniles in the Pacific South of Mexico (i.e., 14 to 16°N) are described. A total of 15 paralarvae were collected during three plankton surveys in July, September and November 2001. Size of paralarvae ranged from 0.7 to 2.7 mm Dorsal Mantle Length (ML), with the smallest size corresponding to the ML at hatching. Additionally, three juveniles were collected by scuba diving in a coastal area in 2010, two small juveniles (7.4 and 9.6 mm ML) were found on a rocky area in May (15°40´N, 96°29´W) and one big juvenile (30 mm ML) was captured in a coral reef in December (15°44´N, 96°07´W). The geographic distribution of O. bimaculatus has been reported from California, USA to La Paz B.C.S (Mexico). This study provides new information on the abundance, distribution and size structure of early-stages of O. bimaculatus, redefining the geographic range of this species in the Tropical Eastern Central Pacific.
A. We recorded seasonal changes in the paralarval cephalopod communities collected off the southwestern coast of Baja California Sur, Mexico, during 2003. Simultaneous surface and oblique trawls were carried out with CalCOFI-type nets and CTD casts during spring and autumn 2003 on board the R/V Río Suchiate (Secretaría de Marina), at 85 sampling stations (Magdalena Bay to Cape San Lucas). The paralarval cephalopod community predominantly showed tropical affinity in both seasons. During autumn, 11 tropical taxa, 2 cosmopolitan taxa, and one temperate taxon were incorporated to the paralarval community recorded previously in spring and were associated with the decrease in Subarctic Water and the entrance of warm water masses to the study region, modifying the community indexes between seasons. The canonical correspondence analysis showed 2 groups significantly correlated with chlorophyll a concentrations and zooplankton volumes. Oblique tows provide better information on the paralarval cephalopod community, while surface tows can be an efficient method for monitoring and evaluating the hatching areas of the jumbo Pacific squid Dosidicus gigas through their paralarvae, which are included in the Sthenoteuthis oualaniensis-Dosidicus gigas complex (SD complex).Key words: paralarvae, community structure, SD complex, Baja California Sur. R .Se registró el cambio estacional en las comunidades de paralarvas de cefalópodos recolectadas frente a la costa suroccidental de Baja California Sur, México, durante 2003. Para lo anterior, se realizaron arrastres superficiales y oblicuos simultáneos con redes tipo CalCOFI y lances de CTD en 85 estaciones de muestreo (de bahía Magdalena a cabo San Lucas) durante primavera y otoño de 2003 a bordo del B/I Río Suchiate (Secretaría de Marina). La comunidad de paralarvas de cefalópodos fue mayormente tropical en ambas temporadas. Durante el otoño se adicionaron 11 taxones tropicales, 2 cosmopolitas y 1 templado a la comunidad registrada previamente en primavera, todos relacionados con la disminución de Agua Subártica y el ingreso de masas de agua cálida a la región; esto modificó los índices comunitarios entre las temporadas. El análisis de correspondencia canónica mostró la formación de 2 grupos correlacionados significativamente con la concentración de clorofila a y el volumen de zooplancton. Los arrastres oblicuos dan mayor información sobre la comunidad de paralarvas, mientras que los superficiales resultan eficientes para el seguimiento y la evaluación de las áreas de eclosión del calamar gigante del Pacífico, Dosidicus gigas, a través de sus paralarvas incluidas en el complejo Sthenoteuthis oualaniensis-Dosidicus gigas (complejo SD).Palabras clave: paralarvas, estructura de la comunidad, complejo SD, Baja California Sur.
In the Caribbean Sea and adjacent areas, squids of the genus Abralia are a key component in the cephalopod community. However, the distribution and abundance of their paralarvae in this region are unknown, as well as their morphology in early development, making their identification difficult. In this study, paralarvae of Abralia spp. from surface Neuston, subsurface Neuston, and multiple opening and closing nets and environmental sensor system (MOCNESS) (0–58 m) tows carried out in the Caribbean Sea were identified, describing the horizontal and vertical distribution of their abundance and their morphology and molecular identity. The greatest abundance of Abralia spp. was recorded in subsurface tows, distributed mainly off Chinchorro Bank, Cozumel, and Honduras, and in a stratum of 38–48 m depth in MOCNESS tows. Paralarvae showed evidence of ontogenetic migration with larger sizes distributed at greater depths. Sixty eight percent of Abralia spp. had sizes of 1.1–2.0 mm mantle length (ML), indicating that the Mesoamerican Barrier Reef System is an important area in the spawning and development of the genus. Fourteen paralarvae were sequenced using the Cytochrome Oxidase I gene (COI) resulting in the presence of two species: Abralia redfieldi and Abralia veranyi (99.01%–100% similarity), which could not be individually identified using the morphological analysis. However, we confirmed their geographical overlap along the Caribbean Sea and described the general morphology of the paralarvae between 1.1–6.0 mm ML.
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