The morphology of Diogenidae megalopa collected in the southwestern Gulf of Mexico was analyzed; the characters considered were: number of segments from the flagellum of the antenna, size and shape of the carapace, number of setae of the scaphognathite of the maxilla, abdomen size, size and number of setae of the endopod and exopod of uropods and number of setae in the posterior margin of telson. A total of 4023 megalopae were obtained and eight species were identified: Calcinus tibicen, Clibanarius antillensis, C. vittatus, C. cubensis, Dardanus insignis, Paguristes sericeus, P. spinipes and Petrochirus diogenes. The species of genus Clibanarius are distinguished by the suboval shape of the telson and have less than nine setae in their posterior margin. The difference between Clibanarius species is given by the number of setae on the scaphognathite of the maxilla and the number of segments in the flagellum of the antenna. The scaphognathite of D. insignis and P. diogenes have more than 70 setae; the difference between these two species is the number of setae on exopods of the uropods. The megalopa of P. sericeus presented six segments on the antenna, P. spinipes and C. tibicen have 10 segments, the difference between these two species is that P. spinipes has 26 setae in the scaphognathite and C. tibicen has 65. With a morphological analysis it was possible to structure a key for genus and species identification. These keys are the first contribution for the identification of Diogenidae megalopae in the southwestern Gulf of Mexico.

Taxonomy and systematics A new species of Deutella (Amphipoda: Caprellidae) from the Gulf of Mexico Una especie nueva de Deutella (Amphipoda: Caprellidae) del golfo de México

Se presenta una lista actualizada y una clave ilustrada para la identificación de los 38 géneros marinos, estuarinos y estigobios de los misidáceos que habitan en el Mar Intra-Americano. Estos crustáceos incluyen 6 familias, 5 subfamilias y 5 tribus dentro de los órdenes Lophogastrida y Mysida. El primero contiene 5 géneros y el segundo 33; de éstos, 35 habitan el ambiente marino y el salobre, 2 el cárstico y 1, Antromysis, vive en cualquiera de los 3 ambientes. Los géneros Anchialina, Siriella, Mysidopsis, Mysidium y Heteromysis se distribuyen ampliamente en todo el Mar Intra-Americano. Contrariamente a Chalaraspidum, Euchaetomera, Eucopia, Gironomysis, Metamblyops, Mysidella, Palaumysis, Platymysis, Pleurerythrops, Pseudomma y Synerythrops con una distribución geográfica restringida. El Mar Caribe y el Golfo de México representan las 2 regiones biogeográficas con mayor número de géneros de misidáceos.