The first reports of wild caught Australian redclaw crayfish from Mexico, in the states of Morelos and Tamaulipas, are presented. Redclaw crayfish were first brought to Mexico in 1995 to initiate experimental cultures at several research centers. In the following years a number of private ventures started commercial cultures, several of which in the states of Morelos and Tamaulipas are thought to have been the sources for the wild populations recorded in this study. The farms that acted as the original sources have not been operating for at least 2 years. In Morelos, high densities and all size classes of redclaws, including ovigerous females, were captured in natural waterways; whereas in Tamaulipas they were found at four sites occurring in irrigation canals in an agricultural district. The size attained by the wild redclaws, the abiotic conditions in which they were found and the potential for spread within the drainage systems of the Balsas and Tamesi Rivers are discussed.

Rhizocephalan parasites are dioecious organisms, in that one or several dwarf males are implanted into the external part of the female parasite soon after it emerges from the interior of the host animal. The structure of the female externa and its resident males is crucial for understanding both the reproductive biology and the taxonomy of these specialized parasites. We use scanning electron microscopy and histological methods to study the anatomy of juvenile and the mature externae of the rhizocephalan barnacle Loxothylacus texanus parasitizing the blue crab Callinectes rathbunae. We put emphasis on the implantation of males and the histology of the female reproductive organs. In the virgin externae, male cyprids attach around a cuticular hood covering the mantle aperture, which is partially blocked by a plug of cuticle so only trichogon larvae, not cyprids, can access the mantle cavity. This resembles the situation known from Sacculina carcini. The mature externa is characterized by a visceral mass that contains the ovary, paired colleteric glands, a single male receptacle, but paired receptacle ducts. The proximal attachment of the visceral mass is located at some distance from the basal stalk, as is characteristic for the genus Loxothylacus. The internal anatomy of the mature externa of L. texanus is in most features similar to that seen in other species of the Sacculinidae, which comprises the majority of rhizocephalan species. However, the single receptacle creates a situation where the two implanted males cannot be kept separate as in most other rhizocephalans, but pass through spermatogenesis in a common chamber. This may have unknown effects on the reproductive biology such as male-male competition.

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RESUMEN.Se presenta un análisis estadístico de variables morfométricas del camarón de agua dulce Potimirim mexicana, que ha sido descrito como hermafrodita protándrico secuencial. El objetivo es probar estadísticamente, que los organismos pueden ser clasificados por sexo, analizando su longitud y otras variables morfológicas. Un total de 191 organismos fueron capturados en el río Máquinas, Veracruz, México. La técnica utilizada fue la de árboles de clasificación, que mediante probabilidades van determinando las variables significativas en la variable "respuesta", así como las que son necesarias para la discriminación. Esta técnica permitió corroborar la teoría que la longitud total del organismo es necesaria para la discriminación de la variable sexo, pero también generó el resultado que, estadísticamente, dos variables más son importantes en este proceso discriminatorio; el largo del segundo pleópodo y largo del carpo del tercer pereiópodo. La técnica generó un clasificación correcta de 82% utilizando las tres variables mencionadas. Lo significativo del proceso es que al generar los árboles de clasificación se muestran, de manera sencilla y práctica, las variables necesarias en este proceso, así como su nivel discriminatorio individual. Palabras clave: árboles de clasificación, Potimirim mexicana, Atyidae, Caridea.Classification trees of Potimirim mexicana (Decapoda: Caridea), a sequential protandrous hermaphrodite organism ABSTRACT. A statistical analysis of several morphometric variables of the freshwater shrimp Potimiirim mexicana, which has been described as a sequential protandrous hermaphrodite, is presented. The purpose of the study is to test, statistically, that organisms can be classified by sex, analyzing their size and other morphological variables. A total of 191 organisms were collected in the Máquinas River, Veracruz, Mexico. The technique used was that of classification trees, through which will likely determines the significant variables in the variable "response", as well as those required for discrimination. This technique corroborated the theory that the total length of the body is necessary for discrimination of the sex variable, but also brought the result that, statistically, two more variables are important in this discriminatory process, the length of the second pleopod and length of the carpus of the third pereiopod. The technique resulted in a correct classification of 82% using the three variables. What is significant is that the process generating the classification tree shown, in a simple and practical manneer, the variables necessary for this process and their individual discriminatory power. Keywords: classification trees, Potimirim mexicana, Atyidae, Caridea. ___________________Corresponding author: Fernando Alvarez (falvarez@unam.mx) INTRODUCCIÓNLos crustáceos presentan especies dioicas o de sexos separados, pero también existen especies hermafroditas simultáneas o secuenciales (Maynard, 1979;De Almeida & Buckup, 2000). Los hermafroditas secuenciales pueden, a su vez, ser protá...