Decapoda) of Southwestern Atlantic plankton, Brazil

Abstract. The present study describes the morphology of Oplophoridae and Bresiliidae larvae collected during the cruise of the RV Thalassa in the Southwestern Atlantic Ocean in 1999. The larvae were caught by oblique hauls from the surface to 200 meters using a bongo net. Thirteen stages of five species of Oplophoridae (Acanthephyra sp.1 to 4, and Janicella spinicauda), and two stages of a single species of Bresiliidae (Discias sp.) were identified and described. All these larvae were very abundant in the shelf break, mainly those of Acanthephyra sp.1. Acanthephyra spp. larvae resembles in morphology those of Discias sp., with exception of the modified dactylus of first pereopod in the larvae of Discias sp. These similarities suggest convergence between Oplophoridae and Bresiliidae larval forms. In contrast, the larvae of Janicella spinicauda share little details with Acanthephyra larvae and are easily recognized by the long serrated rostrum on both ventral and dorsal margins