PROCEEDINGS OF THE BIOLOGICAL SOCIETY OF WASHINGTON 113(3):739-760. 2000. Larval stages of Paradasygyius depressus (Bell, 1835) (Crustacea: Decapoda: Brachyura: Majidae) and a phylogenetic analysis for 21 genera of Majidae Gerhard Pohle and Fernando Marques (GP) Atlantic Reference Centre, Huntsman Marine Science Centre, Brandy Cove, St. Andrews, New Brunswick, E5B 2L7, Canada; e-mail:
[email protected] (FM) Departamento de Zoologia, Universidade Estadual Paulista, 18618-000 Botucatu, Sao Paulo, Brazil; e-mail:
[email protected] Abstract. — All larval stages and the first crab instar of Paradasygyius de-pressus (Bell) were obtained in laboratory culture. Larval development consists of two zoeal stages, followed by the megalopa. Each larval stage is described in detail. 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 instar appearing 11 ± 1 and 15 days after hatching, respectively. A phylogenetic analysis of 21 genera of Majidae is provided based on 34 zoeal and three megalopal characters. The phylogenetic analysis resulted in four equally par-simonious trees 173 steps long (CI = 0.66, RI = 0.71, and RC = 0.47) sup-porting 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 define Oregoniinae, Majinae, and Inachinae. Our phylogenetic hypothesis suggests that Oregoniinae is the most basal clade within the Majidae, and Majinae and 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 derived clade, followed by Achaeus Leach, Pyromaia Stimpson, Paradasygyius Garth, Ana-simus A. Milne-Edwards, and the most basal Stenorhynchus Lamarck. The sister-group relationships of the clade {Pisa Leach (Taliepus A. Milne-Edwards + Libinia Leach)), Mithrax Latreille and Microphrys H. Milne Edwards re-mained unresolved. Paradasygyius depressus (Bell, 1835) is achnopsis, Stimpson, 1871, Pyromaia an eastern Pacific majid crab known fi-om Stimpson, 1871, Anasimus A. Milne-Ed-the Gulf of California to Colombia (Garth wards, 1880, Leurocyclus Rathbun, 1897, 1958). Members of this genus were consid-and Aepinus Rathbun, 1897 differ signifi-ered to belong to the Inachinae (Rathbun cantly from the remaining Inachinae (Drach 1925), Inachidae sensu Guinot (1978). & Guinot 1982, Guinot & Richer de Forges However, recent morphological evidence of 1997). Accordingly, Drach & Guinot the skeleton from adults suggests that Par-(1983) resurrected the family Inachoididae adasygyius Garth, 1958 and the nine other Dana, 1851 to include these genera which American inachine genera Inachoides H. here are considered as Inachoidinae for Milne Edwards & Lucas, 1842, Collodes placement within the still widely recog-Stimpson, 1860, Euprognatha Stimpson, nized Majidae (e.g.. Griffin & Tranter 1986, 1871, Batrachonotus Stimpson, 1871, Ar-Ingle 1992, Melo 1996). Few larvae of in-
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