LARVAL DEVELOPMENT OF THE BRAZILIAN MUD CRAB PANOPEUS AUSTROBESUS WILLIAMS, 1983 (DECAPODA: XANTHIDAE) REARED IN THE LABORATORY

ABSTRACT The South American mud crab Panopeus austrobesus was described only recently (Williams, 1983) as 1 of 6 distinct species that formerly had been considered local "forms" of Panopeus herbstii Milne Edwards, 1834, sensu lato. The larval development in this group of closely related species has been described only in P. herbstii sensu stricto (or, possibly, Panopeus obesus?) from Beaufort, North Carolina. In the present study, larvae of Brazilian P. austrobesus were reared in the laboratory from hatching to metamorphosis. Development consists of a nonfeeding prezoea, 4 zoeae, and 1 megalopa stage. Duration of each of the zoeal stages at 25°C is 4-6 d, and in the megalopal stage about 10 d, i.e., total larval development duration lasts approximately 1 month. The morphology of the larvae is described and compared with that of larvae of P. herbstii sensu stricto (?) and of the 3 species of Panopeus, P. americanus, P. occidentalis, and P. bermudensis, that occur on the Brazilian coast and for which descriptions have recently become available. Comparison of characters considered plesiomorphic reveals that each larval stage can be clearly distinguished from the corresponding stage in P. herbstii sensu stricto (?) and in the other species. Surprisingly, some morphological characters of larvae of P. austrobesus show similarity more to P. bermudensis than to P. herbstii (?) from Beaufort. Possible relationships among these species are discussed, and an identification key is given for the larval stages of the above mentioned Brazilian species of Panopeus.