Abstract Thoe Bell, 1836 is amphi-American in distribution and includes small spider crabs with cryptic habits and rare records in the literature and carcinological collections. The taxonomy of the three recent and two fossil species currently known in the genus has been revised. A phylogenetic reconstruction conducted here based on the mitochondrial markers COI and 16S rRNA supports the monophyletic status of Thoe. The resulting phylogeny suggests a western Atlantic to eastern Pacific radiation of the genus.

Abstract This study investigated the temporal abundance, periods of reproduction and recruitment, gonad sexual maturity, and population structure of the swimming crab Achelous spinimanus (Latreille, 1819) in Macaé, a region of the Brazilian coast affected by upwelling events. The samples were collected monthly during one year. The crabs were counted, sexed and measured for maximum carapace width (MCW). Four developmental stages were described in males and females. Environmental variables as temperature, salinity, organic matter and Phi were measured. A Principal Components Analysis indicated that environmental variables were strongly correlated with seasons, affecting the abundance of this species, which was high during summer and autumn. The periods of reproduction and recruitment were also seasonal, with a peak of females with developed gonads and ovigerous females during autumn and immatures during summer and autumn. Males and females did not differ in size at gonad sexual maturity, estimated at 39.9 and 42.9 mm MCW, respectively. The environmental conditions in this upwelling region may have induced this population of A. spinimanus to show different characteristics and behaviors from other populations on the Brazilian coast, since alterations linked to the periods of reproduction and recruitment, as well as the population structure and distribution, may reveal different survival strategies of the species.

The spatial and seasonal distribution of different demographic groups of the swimming crab Callinectes ornatus was analyzed with respect to its population biology in three bays (Ubatumirim, Ubatuba, and Mar Virado) in southeastern Brazil. In each bay, monthly sampling was performed during two years along six transects, established at 5, 10, 15, and 20 m depth (parallel to the beach line), in a wave-sheltered area (7.5 m depth), and at an exposed site (10 m depth). Total abundance of crabs was similar among the bays. The presence of immature individuals, adult females, and breeding females was positively correlated with the bottom and surface temperatures, whereas adult males showed an opposite trend with respect to these factors. Immature and smaller individuals were most abundant along the sheltered and shallower transects. Males were more abundant along the shallower transects, and females at 15 and 20 m. This study revealed that different demographic groups occupy the habitat in different ways, according to local features. In general, southeastern Brazil offers a range of conditions that favor reproduction and consequently the maintenance and growth of the local population of C. ornatus, contributing to the relatively high abundance of the species in this coastal area.

Se analizó la distribución espacial y temporal de distintos grupos demográficos del cangrejo nadador Callinectes ornatus en cuanto a su biologia poblacional en tres bahias (Ubatumirim, Ubatuba y Mar Virado) en el sureste de Brasil. En cada bahia se realizaron muestreos mensuales durante dos años en seis transectos, establecidos a 5, 10, 15 y 20 m de profundidad (paralelo a la linea de costa), en una zona protegida del oleaje (7.5 m de profundidad) y en un sitio expuesto al oleaje (10 m de profundidad). La abundancia total de cangrejos fue similar entre bahias. Se observó una correlación positiva entre la presencia de individuos inmaduros, hembras adultas y hembras ovigeras con la temperatura del fondo y superficial, mientras que los machos adultos mostraron una tendencia opuesta con respecto a estos factores. La mayor abundancia de individuos inmaduros y pequeños fue detectada en los transectos protegidos y menos profundos. Los machos fueron más abundantes en los transectos menos profundos, y las hembras a 15 y 20 m de profundidad. Este estudio reveló que los diferentes grupos demográficos ocupan el hábitat de diferentes maneras, de acuerdo con las caracteristicas locales. En general, el sureste de Brasil ofrece diferentes condiciones que favorecen la reproducción y consecuentemente la continuidad y el crecimiento de la población local de C. ornatus, contribuyendo a la relativamente alta abundancia de la especie en esta zona costera.