The complete larval development of Armases benedicti (Rathbun) (Decapoda, Sesarmidae), from the Amazon region, reared in the laboratory

São descritos e ilustrados em detalhes, os quatro estágios de zoea e um de megalopa do caranguejo Armases benedicti (Rathbun, 1897), a partir de larvas obtidas em laboratório. A média de duração de cada estágio larval foi 3, 2, 4, 4 e 13 dias, respectivamente. O período compreendido desde a eclosão até o surgimento do primeiro juvenil foi de 26 dias. Morfologicamente A. benedicti é muito similar às outras espécies do gênero, contudo, um pequeno espinho lateral é claramente observado na carapaça das zoeas desta espécie. Esta característica aparenta ser única dentre os Sesarmidae. Outra característica distinta desta espécie é a distribuição das cerdas do endópodo da maxila (2+2), o qual difere dos demais sesarmídeos que apresentam a distribuição (2+3), exceto para Sesarma tetragonum (Fabricius, 1798) o qual apresenta (2+2). Outras comparações morfológicas com trabalhos anteriores relacionados a larvas do gênero Armases Abele, 1992 são brevemente discutidas.

Redescription of megalopa and juvenile development of Pachygrapsus gracilis (Decapoda: Grapsidae) from the Amazon region, reared in the laboratory

ABSTRACT: This present study re-describes the megalopa stage and provides detailed morphological descriptions and main growth changes observed in stages I through VII of the juvenile instars of the dark shore crab Pachygrapsus gracilis (Saussure, 1858), from the Amazon region. The specimens in this study were reared in the laboratory and the megalopae were collected at Ajuruteua beach in northeastern Pará, Brazil. Previous studies had described the megalopa of P. gracilis from Mexican waters, as well as those of Pachygrapsus transversus (Gibbes, 1850) and Pachygrapsus marmoratus (Fabricius, 1787). A comparison between the Mexican and Amazonian populations of P. gracilis revealed significant morphological differences. The main difference is the presence of 3 elongated setae on the 5th pereiopods of individuals of the Amazonian population. The setal number and their arrangement in the appendages also differed. In P. gracilis, the male and female genital openings are observed from the juvenile instar III, whereas differentiation in male pleopods is observed only in juvenile instar V. In females, the pleopods undergo rapid differentiation during juvenile instar VI. These morphological comparisons and other observations on development are briefly compared and discussed with reports for other species.

Comparative morphology of the first zoea of twelve brachyuran species (Crustacea: Decapoda) from the Amazon region

The laboratory-hatched first zoeal stage of twelve brachyuran species collected in the estuarine area of the Caeté River in the Amazonian region are described and illustrated in the present study: P. americanus Saussure, 1857, Eurytium limosum (Say, 1818), Sesarma curacaoense De Man, 1892, S. rectum Randall, 1840, Armases rubripes (Rathbun, 1897), Aratus pisonii (H. Milne Edwards, 1837), Ocypode quadrata (Fabricius, 1787), Uca rapax (Smith, 1870), U. maracoani (Latreille, 1802), U. thayeri Rathbun, 1900, Ucides cordatus (Linnaeus, 1763) and Pachygrapsus gracilis (Saussure, 1858). Through intraspecific comparisons of the respective larval stage, an identification key was generated and provided. Most of the studied species presented morphological differences (e.g. type and presence or absence of setae) when compared to the same species previously described in the literature.