Background In Mexico, species of four families of free-living calanoid copepods have been recorded as inhabitants of several freshwater systems. These families are Centropagidae, Temoridae, Pseudodiaptomidae and Diaptomidae. The genera Leptodiaptomus and Mastigodiaptomus are the most speciose diaptomid genera in Mexico, and they inhabit natural and artificial lakes, ephemeral ponds, springs, and caverns. Leptodiaptomus is considered as an endemic Nearctic genus, whereas Mastigodiaptomus is a widely distributed Neotropical genus in the southern USA, Mexico, the Caribbean Islands and Central America. Based on new and recent evidence, Mastigodiaptomus diversity has been underestimated: six species of the genus were known before 2000. In this work three new Mastigodiaptomus species have been described from different regions of Mexico by using integrative taxonomy. We also gave amended diagnosis of M. nesus Bowman (1986) and M. patzcuarensis s. str. (Kiefer, 1938). Methods In this work, the taxonomic status of the species was clarified using modern, integrative method based on the COI gene as a DNA marker, plus micro-structural analysis (based on SEM and ligth microscopy). Results Three new species of Mastigodiaptomus were described based on genetic and morphological analyses: M. alexei sp. n., M. ha sp. n. and M. cihuatlan sp. n. Also amended description of M. nesus, morphological variation of M. patzcuarensis s. str., and a comparison of them with all known sequences within the genus are provided. These new findings show that in Mastigodiaptomus differences in several cuticular microstructures of several appendages (such as the antennules, the fifth legs, or the urosomites of these copepods) agree with the interspecific genetic divergence >3% observed in sequences of the COI gene, and the integration of this information is a powerful tool in species delineation.
de 142 publicaciones del período de 1841-2012. En el recuento se registraron 315 especies diferentes de amibas. Los grupos dominantes fueron Amebozoa, Rhizaria y Excavata, con una importante contribución de las amibas testadas y de los gimnamebidos del tipo acantamebidos. La mayoría de los trabajos se han realizado en los estados del centro de la República Mexicana, especialmente en el Distrito Federal, correspondiendo con la ubicación de los principales grupos de investigación. Nueve estados no tienen ningún estudio de amibas de vida libre incluyendo algunas de las regiones más biodiversas de México como Chiapas, Tabasco y Yucatán. El primer registro de amibas en nuestro país fue en 1841. El mayor número de registros se presenta a partir de los años sesenta del siglo pasado y ha mantenido una tendencia de constante crecimiento, la perspectiva es que existen todavía elevados números de especies amibianas por descubrir, muchas de ellas fundamentales para el funcionamiento de gran número de ecosistemas. Esta es la primera revisión del estatus en que se encuentran las investigaciones en México enfocada exclusivamente al grupo de las amibas de vida libre.Palabras clave: Protozoa, gimnamebas, amibas de vida libre, anfizóicas, amibas testadas.
A helminthological examination was performed on 114 specimens of sciaenids that were captured on the Alvarado coast, Veracruz, Mexico, between August 2004 and July 2006. Bairdiella chrysoura (n = 15); Cynoscion arenarius (n = 31); Menticirrhus americanus (n = 16); Menticirrhus littoralis (n = 33) and Umbrina coroides (n = 19). 26 parasites were identified at the species, 12 genus and 5 family levels, as follows: 21 digeneans (14 adults and 7 metacercariae), 9 monogeneans, 7 nematodes (4 adults and 3 larvae), 2 cestodes (larvae), and 4 acanthocephalans (adults). Digeneans and monogeneans were the most abundant. Helminths with the highest prevalence in all five communities were Pseudorhamnocercoides stichospinus and Tetraphyllidae. The species with highest mean intensity were Diplomonorchis leiostomi and Tetraphyllidae, and Hysterothylacium sp., were registered in the five communities. Significant correlations between the host total length and species richness, U. coroides (r = 0.54), and total length and abundance, M. americanus (r = 0.63), were found. The highest similarity was recorded among communities of M. americanus and M. littoralis. The infracommunities and component communities in species richness and diversity, in all cases, were within ranges observed in most marine fish helminth communities.
Peritrichs usually settle on the external surface and gills of crustaceans. However, their physiological effect on the host has not been studied. Respiratory rate is a susceptible index for some factors that affect an organism. To test if ciliates attached to the crustacean gills have a physiological effect, we measured crustacean oxygen consumption in a closed system. Crayfish Cambarellus (Cambarellus) montezumae were collected in Lago Xochimilco in Mexico City and were isolated in chambers. Two peritrich species, Cothurnia variabilis (32.5%) and Epistylis gammari (67.5%), were observed on the gills. The metabolic rate was evaluated by oxygen consumption with a polarimetric oximeter. Statistical analyses demonstrated that a density of ciliates attached to the gills of the crayfish above ~50 individuals increased oxygen consumption with a positive correlation to epibiont density. We conclude that C. variabilis and E. gammari ciliate epibionts attached to the gill of the crayfish Cambarellus (Cambarellus) montezumae cause an increase in metabolic rate.
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