Larval morphology of the sesarmid crab, Aratus pisonii (H. Milne Edwards, 1837) (Decapoda, Brachyura, Grapsoidea) from laboratory-reared material

Three ovigerous females of the crab, Aratus pisonii (H. Milne Edwards, 1837) (Sesarmidae) were captured from a coastal lagoon in Mazatlán, Mexico. Larvae were reared in the laboratory from hatching to the megalopa stage. The morphology of the four zoeal stages and the megalopa is described and illustrated. Morphological comparisons are made with previous descriptions of this species from Jamaica and Brazil, and with all known descriptions for the larvae of Armases Abele, 1989, the closest similar genus. Several differences are observed with regard to earlier descriptions of Aratus pisonii, and additional characters, such as the previously undescribed cephalothoracic setation of the larval stages and the mouthparts of the megalopa, are described and illustrated.