This work represents a continuation of a previous article about the cyclopoid copepod fauna in arid areas of north-central México, in this case about the subfamily Eucyclopinae. From samples previously collected (1985-2008) and from new samples, we reviewed the eucyclopine copepod fauna from this vast arid area of México. Three priority ecore-gions (CONABIO) were included, comprising part of the states of Aguascalientes, Zacatecas, San Luis Potosí, Durango, Chihuahua, and Coahuila. Up to 22 species of the Eucyclopinae were found, among which 18 are new state records. Diagnoses and taxonomic illustrations of the species recorded are provided together with a comparative analysis of the specimens examined. The records reported in this paper plus those previously published on the subfamily Cyclopinae, represented a 20% increase in the list of species of Cyclopoida from inland waters present in México. An overall bio-geographic analysis of the Cyclopoida was performed; it shows a high degree of endemism in this region (20%), similar to that detected for the group in the Yucatan Peninsula (19%). Using a Similitude Analysis (Jaccard) we found that the fauna of the northern arid areas is very similar to that of central México and southern United States. Another group was formed by the Caribbean, Central America, and southern México. There is a considerable divergence between the South American cyclopoid fauna with the rest of the continent.

Este trabajo representa la continuación de un artículo previo relativo a la fauna de copépodos ciclopoides de las zonas áridas del centro-norte de México, en este caso de la subfamilia Eucyclopinae. Con base en muestras previamente recolectadas (1985-2008) y de nuevas recolecciones, revisamos la fauna de euciclópinos de estas extensas zonas áridas de México. El estudio incluyó tres ecoregiones prioritarias (CONABIO) que incluyen parte de los estados de Aguascalientes, Zacatecas, San Luis Potosí, Durango, Chihuahua y Coahuila. Se encontraron 22 especies de Eucyclopinae así como 18 nuevos registros estatales. Se proporcionan diagnosis e ilustraciones taxonómicas de las especies encontradas y se presentan análisis comparativos de los especímenes examinados. Los registros reportados en este artículo junto con los de la subfamilia Cyclopinae previamente publicados, representaron un incremento de 20% en la lista de especies de ciclopoides de aguas continentales presentes en el país. Se efectuó un análisis biogeográfico conjunto de los Cyclopoida que muestra un alto grado de endemismo en esta particular región geográfica (20%), similar al detectado para el grupo en la península de Yucatán (19%). Mediante un análisis de similitud (Jaccard), se encontró que la fauna de las zonas áridas norteñas es muy similar a la del centro del país y a la del sur de los Estados Unidos. Otro grupo afín está presente en el Caribe insular, América Central y sur de México. Existe una diferencia considerable entre la fauna de ciclopoides de Sudamérica con respecto a la del resto del continente.

From a series of biological samples collected from different freshwater environments in Costa Rica, Central America, the exotic Asian cyclopoid Mesocyclops thermocyclopoides Harada, 1931 was identified. We analyzed the morphology and appendage ornamentation of different Neotropical populations of this species, including specimens from Honduras, southeastern Mexico, and Costa Rica. We also examined Asian specimens from Taiwan, Indonesia, Vietnam, and Thailand, and performed a comparison of the Neotropical and Asian populations including a Principal Component Analysis (PCA). The Neotropical and Asian specimens show subtle morphological variations in the antennules, antennae, mandibles, swimming legs 1-4, and fifth legs. Some characters in the Neotropical group appear to diverge from the Asian pattern and the PCA indicated that intercontinental populations of M. thermocyclopoides are far from being homogeneous. These intra-specific differences are described to expand the known morphological range of this species and to provide the first comparative analysis of an exotic copepod in the Americas. Our analysis suggests that the geographic isolation of the American populations and the subtle morphological divergences with respect to the Asian patterns could be related to speciation processes in the Neotropical region, but also intra-Asian differences are reported. In the Neotropical region this species appears to be restricted to southeastern Mexico, Central America, and one Caribbean island; its potential as biological control of mosquito might enhance its spread in the region.

Freshwater cyclopoid copepods represent a group whose diversity and biogeography has been studied in different areas of Mexico, but its knowledge in arid environments, mainly in the Central-Northern region of the country, was still limited. From samples previously obtained (1985-2008) and also from new collections, we reviewed the copepod of the subfamily Cyclopinae from water bodies of this extense arid zone of Mexico. This study incorporated three priority eco-regions (CONABIO), that include the states of Aguascalientes, Zacatecas, San Luis Potosí, Durango, Chihuahua and Coahuila. Up to 16 species of the subfamily Cyclopinae were found, including 3 undescribed species (one Acanthocyclops, two Microcyclops) and other species that are probable endemics in this region of the country. The genus Metacyclops is recorded for the first time in Mexico. Diagnoses and taxonomic illustrations of the species are provided together with a comparative analysis of the specimens examined. Up to 22 new state records of cyclopines are presented; this is also the first taxonomic survey on freshwater copepods focused in this arid area of Mexico. With the findings reported here the number of species of Cyclopinae occurring in Mexico increased from 37 to 43 (16%).

Los copépodos ciclopoides de aguas continentales representan un grupo cuya diversidad y biogeografía han sido estudiadas en distintas zonas de México pero su conocimiento en los ambientes áridos, principalmente en la región centro-norte del país, era muy limitado. A partir de muestras previamente obtenidas (1985-2008) y de nuevas recolecciones, se revisaron los copépodos de la subfamilia Cyclopinae de los cuerpos de agua de esta extensa zona árida de México. El estudio abarcó tres eco-regiones prioritarias (CONABIO) que incluyen los estados de Aguascalientes, Zacatecas, San Luis Potosí, Durango, Chihuahua y Coahuila. Se encontraron 16 especies de Cyclopinae, incluyendo 3 especies no descritas (una de Acanthocyclopsy dos de Microcyclops) y otras posiblemente endémicas de esta región del país; se registra por primera vez al género Metacyclops en México. Se proporcionan diagnosis e ilustraciones taxonómicas de las especies encontradas y se hacen análisis comparativos de los especímenes examinados. Se presentan 22 nuevos registros estatales de ciclópinos; se trata, además, del primer estudio taxonómico de los copépodos continentales enfocado a esta región árida de México. Con los hallazgos presentados el número de especies de Cyclopinae presentes en México aumentó de 37 a 43 (16%).