Larval stages of Paradasygyius depressus (Bell, 1835) (Crustacea : Decapoda : Brachyura : Majidae) and a phylogenetic analysis for 21 genera of Majidae

All larval stages and the first crab instar of Paradasygyius depressus (Bel l) were obtained in laboratory culture. Larval development consists of two zoeal stages, followed by the megalopa. Each larval stage is described in d etail. Beginning with the first zoea, the duration of each stage was 4--7 ( 4.5 +/- 0.7), 4-5 (4.5 +/- 0.5), and 7 days, the megalopa and first crab in star appearing 11 +/- 1 and 15 days after hatching, respectively. A phyloge netic analysis of 21 genera of Majidae is provided based on 34 zoeal and th ree megalopal characters. The phylogenetic analysis resulted in four equall y parsimonious trees 173 steps long (CI = 0.66, RI = 0.71, and RC = 0.47) s upporting the monophyly of Oregoniinae, Majinae, and Inachinae (with the ex clusion of Macrocheira De Haan incertae sedis). Based on general agreement of sister-group hypotheses, we provide sets of larval characters that defin e Oregoniinae, Majinae, and Inachinae. Our phylogenetic hypothesis suggests that Oregoniinae is the most basal clade within the Majidae, and Majinae a nd the clade (Epialtus H. Milne Edwards + Inachinae [excluding Macrocheira incertae sedis]) are sister taxa. Within Inachinae, all trees suggest that Inachus Weber and Macropodia Leach are sister taxa nested as the most deriv ed clade, followed by Achaeus Leach, Pyromaia Stimpson, Paradasygyius Garth , Anasimus A. Milne-Edwards, and the most basal Stenorhynchus Lamarck. The sister-group relationships of the clade (Pisa Leach (Taliepus A. Milne-Edwa rds + Libinia Leach)), Mithrax Latreille and Microphrys H. Milne Edwards re mained unresolved.