Population biology of the crab Armases angustipes (Crustacea, Decapoda, Sesarmidae) at Brazilian tropical coast

Abstract

ABSTRACT. The semi terrestrial crabs are important elements of the fauna of coastal regions. The aim of this study was to analyze the population structure of Armases angustipes (Dana, 1852) at estuaries of the Ariquindá River, considered a non impacted area, and Mamucabas River, considered a few impacted area, on the south coast of state of Pernambuco, Brazil. The species occurred in all months of the year. The number of individuals per month varied, being higher in the months of transition between the seasons. This is probably due to significant seasonal variations of air and burrow temperature and burrow salinity. There was no sexual dimorphism in size of A. angustipes in the mangrove of Ariquindá River, but males were larger than females in the mangrove of Mamucabas River. In both estuaries, the sex ratio did not differ from Mendelian proportion, but showed a deviation for females. The analysis of temporal variation in sex ratio showed significant differences in some months of the year. These variations are due to cyclical events that act distinctly on each sex. In both estuaries, size classes of carapace width were equally represented by both sexes. The ovigerous females of A. angustipes occurred only in some months of the year, especially in summer, in both estuaries. Probably the high phytoplankton productivity observed in summer favors the reproductive activity, since these algae serve as food for the larvae. Specimens of the population of Rio Ariquindá are largest and wider than those of Mamucabas River. This fact, associated with the low abundance of crabs and the lower frequency of ovigerous females observed in Mamucabas River, is an indication that this population may be influenced by the environmental impacts that this estuary has received. KEYWORDS. Population dynamics, reproductive period, sesarmid.RESUMO. Biologia populacional do caranguejo Armases angustipes (Crustacea, Decapoda, Sesarmidae) na costa tropical brasileira. Os caranguejos semiterrestres são importantes elementos da fauna em regiões costeiras. O objetivo do presente trabalho foi analisar a estrutura populacional do caranguejo Armases angustipes (Dana, 1852) nos estuários dos rios Ariquindá, considerada uma área não impactada, e Mamucabas, considerada uma área pouco impactada, localizados no litoral sul do Estado de Pernambuco, Brasil. A espécie ocorreu em todos os meses do ano em ambos os estuários. O número de indivíduos variou entre os meses, sendo maior nos meses de transição entre as estações do ano. Isso, provavelmente, é devido às variações sazonais significativas da temperatura do ar e da toca e da salinidade da toca. Não houve dimorfismo sexual relativo aos tamanhos de A. angustipes no manguezal do Rio Ariquindá, mas os machos foram maiores do que as fêmeas no manguezal do Rio Mamucabas. Em ambos os estuários, a proporção sexual não diferiu da proporção mendeliana, mas mostrou um desvio para as fêmeas. A análise da variação temporal na proporção sexual pôde evidenciar diferenças significativas em alguns meses do ano. Essas v...

Larval dispersal of Brachyura in one of the largest estuarine/marine systems in the world

“…The rainfall intensity seems to be the parameter regulating A . rubripes reproduction in the equatorial region, as observed for Aratus pisonii (H. Milne Edwards, 1837) [ 121 , 122 ] and Armases angustipes (Dana, 1852) [ 123 ], which can be advantageous to these populations due to increased concentration of nutrients, higher tides—increasing the chance of transport over long distances—and increased seawater productivity, which favors the larval development in plankton [ 121 , 124 ].…”

Larval dispersal of Brachyura in the largest estuarine / marine system in the world

“…Two sets of samples were collected, horizontal and oblique haulsin each site at different coastal distances (23,53,83,158,198, and 233 km). Two zooplankton hauls were conducted: one horizontal subsurface at 0.5 m from the surface and another oblique ('V'-shaped, covering up to % of the local depth).…”

“…Our results confirm larval export, with all larval stages dispersed up to 123 km from the coast, and reproductive peak in January, the high rainfall period in the Amazon region. The rainfall intensity seems to be the parameter regulating A. rubripes reproduction in the equatorial region [155], as observed for Aratus pisonii (H. Milne Edwards, 1837) [156,157] and Armases angustipes (Dana, 1852) [158]. The spawning in the rainy season can be advantageous to these populations due to increased concentration of nutrients, higher tides -increasing the chance of transport over long distances -and increased seawater productivity, which favors the larval development in plankton [156,159].…”