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.
Highlights
The dark shore crab Pachygrapsus gracilis (Saussure, 1858) has a wide distribution, occurring in the western Atlantic from the Caribbean to Texas, French Guiana, Brazil (Trinidad and from Ceará to Rio Grande do Sul) and Argentina, In the eastern Atlantic the species occurs from Senegal to Angola (MELO 1996, POUPIN et al 2005)
Pachygrapsus Randall, 1839 megalopae was described in the past from individuals collected in the natural environment: P. marmoratus (Fabricius, 1787) by GUERAO et al (1997), P. transversus (Gibbes, 1850) by FLORES et al (1998) and P. gracilis by CHÁRAZO-OLVERA & ROCHA-RAMÍREZ (2007)
Two studies on the juvenile growth and morphology of this group are available in the scientific literature: GUERAO et al (1997) for P. marmoratus and FLORES et al (1998) for P. transversus
Summary
The dark shore crab Pachygrapsus gracilis (Saussure, 1858) has a wide distribution, occurring in the western Atlantic from the Caribbean to Texas, French Guiana, Brazil (Trinidad and from Ceará to Rio Grande do Sul) and Argentina, In the eastern Atlantic the species occurs from Senegal to Angola (MELO 1996, POUPIN et al 2005). A. Abrunhosa scribes the megalopa stage of P. gracilis inhabiting the Amazon region, and describes important morphological changes observed during the growth from juvenile instars I to VII, of. The growth (carapace width) of each subsequent juvenile instar showed an increase during the days of culture and molts (Fig. 3).
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
