No abstract

The latitudinal gradient of species diversity is a widely recognized but poorly understood phenomenon. In marine systems, differences in dispersal abilities among species may pose an additional problem in identifying the processes that affect diversity. We compared latitudinal diversity gradients along two parallel continental coasts, the east and west coasts of South America, of two groups of Crustacea (Brachyura and Anomura), which exclusively exhibit planktonic development. We also evaluated the species-area and the energy-input hypotheses. Diversity decreased with increasing latitude for both groups in both oceans. Results suggest that the spatial structure of sea surface temperature (SST) explains diversity of both groups at large, but not small (< 5°), scales. Range size and latitude were not correlated. We hypothesize that SST differentially affects taxa with contrasting modes of development, influencing patterns of diversity. We suggest that developmental modes of marine organisms should be considered in future diversity analyses.

RESUMEN. Se analiza y se resume toda la información disponible sobre las pesquerías de crustáceos Decápodos comerciales del Mar Epicontinental Argentino y del talud contiguo. En la actualidad son cinco las especies que tienen valor comercial. Dos anomuros: Lithodes santolla (centolla) y Paralomis granulosa (centollón), dos peneidos: Pleoticus muelleri (langostino) y Artemesia longinaris (camarón) y un braquiuro: Ovalipes trimaculatus (cangrejo nadador). Mediante campañas y viajes a distintas regiones donde se hallan y explotan estos crustáceos se dispone de una importante información biológico-pesquera, relativa a las épocas y zonas de reproducción, crecimiento, reclutamiento, áreas de concentraciones pescables, fluctuaciones, etc, lo que ha permitido recomendar un ordenamiento adecuado en la pesquería de alguna de ellas. Se destaca las poblaciones de langostino del litoral patagónico, por ser el recurso de mayor importancia. Desde 1980 ha crecido la extracción de langostino en forma significativa, con fluctuaciones anuales, llegando en algunos años a volúmenes de desembarques de más de 25.000 tm lo que sobrepasa los 100 millones de dólares americanos en valor de exportación.

Sexual maturity, temporal reproductive pattern, and recruitment of juveniles were examined for the penaeoid shrimp Artemesia longinaris sampled for five and a half years in a tropical locality off the coast of São Paulo (23º S), Brazil. Monthly samples were taken from January 1998 to June 2003 at depths between 5 and 45 m. Ovarian maturity was used to examine breeding in adult females. Recruitment was defined as the percentage of juveniles of the total number of individuals in each month and season. A total of 10 288 females and 5 551 males were collected. Estimated sizes (carapace length) at the onset of sexual maturity were 11.0 mm and 13.4 mm for males and females, respectively. Over the five and a half years, females with ripe gonads were found in every season, with the highest percentages in summer (January-March). Juvenile shrimps occurred year-round. These results suggest a continuous reproduction of A. longinaris with temperature acting as an environmental stimulus for the duration of the ovary development cycle. These data and the hypothesis of the intrusion of the South Atlantic Central Water mass, which lowered water temperature and raised plankton production, suggest that the end of spring and the beginning of summer were the principal reproductive months. The classical paradigm of continuous reproduction at lower latitudes, with increased seasonality of breeding period at higher latitudes seems to apply to this species. Rev. Biol. Trop. 55 (Suppl. 1): 39-48. Epub 2007 June, 29.