A taxonomic study of the larvae of four thalassinid species (Decapoda, Thalassinidea) from the Gulf of Mexico Nguyen Ngoc-Ho Laboratoire de Biologic animale, Universite de Nancy I, C.O. 140, 54037 Nancy, France. Introduction Larvae of American mud-shrimps belonging to the superfamily Thalassinidae are poorly known. The complete larval stages of only three species have been described to date: Upogebia pugettensis (Dana) by Hart (1937), Upogebia affinis (Say) by Sandifer (1973) (family Upogebiidae), both described from plankton collected material, and Naushonia crangonoides Kingsley by Goy & Provenzano (1978), the first stage of which was described from plankton material and the remaining ones from laboratory reared specimens. The recent material of decapod larvae from the Gulf of Mexico collected by the Virgilio Uribe Cruise (August 1972) contains numerous samples of thalassinid larvae from some stations (see Station List deposited in the Crustacea Section, British Museum (Natural History), London). Three species of Upogebia, one of which is probably U. affinis (Say), have been identified in this material and also a species belonging to the family Laomediidae and tentatively assigned to the genus Axianassa. The latter shows strong affinities to some larvae attributed by Menon (1933) to the subfamily Upogebiinae but is considered here as laomediid. As two families of the Thalassinidea are considered in this Mexican plankton, it is convenient to discuss the representatives of each under separate headings: A. Description of the larvae of three species of Upogebia Leach from the Gulf of Mexico with observations on larvae and adults of Upogebia in the collections of the British Museum (Natural History), London. B. Description of the larvae of a species of the Laomediidae attributed to Axianassa from the Gulf of Mexico. C. The relationship between larvae of the Laomediidae, those of the Upogebiidae and the adults of the Glypheidae. Materials and methods Larvae were sorted from plankton samples taken during the Virgilio Uribe Cruise during August 1972; they were preserved in 5% formalin. The size of the larvae given in the descriptions are the carapace length (c.l.) measured from the tip of the rostrum to the posterior border of the carapace in the mid-line, and the total length (t.l.) measured from the tip of the rostrum to the posterior margin of the telson. Drawings were made, using a camera lucida, from whole larvae or dissected appendages mounted in a drop of water. A. Larval stages of three species of Upogebia Three species of larval Upogebia can be recognized in the Mexican plankton material. No characters have been found that enabled the separation of the first larval stage which was Bull. Br. Mus. nat. Hist. (Zool.) 40 (5) : 237-273 Issued 30 July 1 98 1
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