Contributions to Zoology, 73 (3) (2004)Patsy A. McLaughlin; Rafael Lemaitre; Christopher C. Tudge: Carcinization in the Anomura – fact or fiction? II. Evidence from larval, megalopal and early juvenile morphology

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Zoeal phase

Knowledge of zoeal development in the Porcellanidae is appreciably more complete. Despite their distinctive, very elongate rostral and posterolateral carapace spines, porcellanid zoeas were considered by early carcinologists essentially to be very similar to those of the Brachyura (Müller, 1863). However, only two characters might conceivably link the porcellanids to the Brachyura, i.e., the reduced, somewhat rod-shaped antennal exopod and the lack of a functional exopod on the third maxilliped (Williamson 1974). Only in Petrocheles spinosus Miers, 1876, does the number of porcellanid zoeal stages exceed two, and only in this species do uropods develop before the megalopal stage. Wear (1965) described five zoeal stages for P. spinosus, with uropods developing in stage three, but with no pleopods developed in either the zoeal or megalopal stages. In all other porcellanids for which larval data are available, developing pleopods are present in ZII and become functional in the megalopal stage, only to be reduced or lost in subsequent juveniles stages. While paired, egg-bearing pleopods reappear in females, pleopods are completely absent in adult males unless the second pair develop as gonopods.