Adrián Cervantes-Martínez

Limnological and morphometrical data of eight karstic systems `cenotes' of the Yucatan Peninsula, Mexico, during the dry season (February–May, 2001)

The karstic nature of the Yucatan Peninsula allows the formation of natural sink-holes from the dissolution of calcareous rock. These systems are almost the only epigean source of fresh water available in this region. In spite of their biological importance, little is known about the morphometric and limnologic characteristics of these karstic systems. We measured limnological variables in eight cenotes in central Quintana Roo during February–May, 2001. Zooplankton biomass and chlorophyll a were also measured in order to determine if the behavior of primary and secondary production was related to environmental parameters. Important short-term changes were observed in nutrients (NO3−, NO2−, PO43-), biomass, and chlorophyll a. The morphometrically conditioned productivity (MCP), which evaluates the cumulative effect of several morphometric variables on production (area, maximum length, shoreline development, perimeter), showed a negative correlation with respect to zooplankton biomass, as did also both pH and temperature. Conversely, NO3− and NO2− had a positive correlation with zooplankton biomass. No correlation was found for chlorophyll a. Significant differences in NO3− (F = 61.52, p<0.001), NO2− (F = 7.36, p<0.001), zooplankton biomass (F = 17.57, p<0.001), chlorophyll a (F = 62.19, p<0.001), and conductivity (F = 497.49, p<0.001) were found among the systems. These results indicate the existence of sharp differences between these karstic systems (oligotrophic, with smaller area, deep and less productive) and non-karstic ones, (eutrophic, larger area, shallow and more productive) but are similar to previous data from other karstic systems of Mexico and other parts of the world. However, understanding of these fragile tropical systems is in the initial phase. It is necessary to increase the intensity of these studies in order to allow a full explanation of their limnological behavior.

A checklist of the littoral cladocerans from Mexico, with descriptions of five taxa recently recorded from the Neovolcanic Province

By 1996 an inventory of Mexican cladocerans hadrecorded 48 species of which 22 belonged toChydoridae, Macrothricidae and Ilyocryptidae.Unfortunately, most of the surveys were made beforeresearchers knew that these crustaceans are notentirely cosmopolitan. For this reason and the lack ofdeposited type material, many of these records aredoubtful and need detailed analyses. In this study,material from 18 water bodies located in theNeovolcanic Province of Mexico is analyzed andcompared with the literature. Also, males of Camptocercus dadayi Stingelin and Leydigialeydigi (Schoedler) and new records Eurycercus longirostris Hann and Biaperturaintermedia (Sars) are described. Half of thetotal number of species recorded are American endemicsand represents a mixture of the North and SouthAmerican fauna, suggesting that Mexico constitutes atransition between Nearctic and Neotropicalzones.

Description of Eucyclops tziscao sp. n., E. angeli sp. n., and a new record of E. festivus Lindberg, 1955 (Cyclopoida, Cyclopidae, Eucyclopinae) in Chiapas, Mexico

Abstract Two new species of the freshwater cyclopoid genera Eucyclops are described, Eucyclops tziscao sp. n. and E. angeli sp. n. Both species belong to the serrulatus-group defined by morphological features such as: the presence of distal spinules or hair-like setae (groups N1 and N2) on frontal surface of antennal basis; the fourth leg coxa with a strong inner spine that bears dense setules on inner side, yet proximally naked (large gap) on outer side; and a 12-segmented antennule with smooth hyaline membrane on the three distalmost segments. Eucyclops tziscao sp. n. is morphologically similar to E. bondi and E. conrowae but differs from these species in having a unique combination of characters, including a caudal ramus 4.05±0.25 times as long as wide, lateral seta of Enp3P4 modified as a strong, sclerotized blunt seta, coxal spine of fourth leg with inner spinule-like setules distally, and sixth leg of males bearing a strong and long inner spine 2.3 times longer than median seta. Eucyclops angeli sp. n. can be distinguished by an unique combination of morphological features: the short caudal ramus; the long spine on the sixth antennular segment of A1; the presence of one additional group of spinules (N12’) on the caudal surface of A2; the presence of long setae in females, or short spinules in males on the lateral margin of fourth prosomite; the strong ornamentation of the intercoxal sclerite of P4, specially group I modified as long denticles; the distal modified setae of Exp3P3 and Exp3P4 in females and males; and the short lateral seta of P5. Finally, we report on a new record of E. festivus in México, and add data on morphology of the species.

A new anchialine Stephos Scott from the Yucatan Peninsula with notes on the biogeography and diversity of the genus (Copepoda, Calanoida, Stephidae)

Abstract Surveys of the anchialine crustacean fauna of the Yucatan Peninsula (YP), Mexico, have revealed the occurrence of calanoid copepods. The genus Stephos Scott, 1892, belonging to the family Stephidae is among the most frequent and widely distributed groups in anchialine caves but has not been hitherto recorded from the YP. Recent collections from an anchialine cave in an island off the northern coast of the YP yielded many specimens of a new species of Stephos. The new taxon, S. fernandoi sp. n., is described here based on male and female specimens. The new species is clearly distinguished from its congeners by the following characters: male left fifth leg with three terminal lamellae plus subdistal process, right leg with distal row of peg-like elements; female fifth leg with single long, acute apical process; genital double-somite with two rows each of 4 long spinules adjacent to operculum; legs 2-4 with articulated setae. The diversity of the genus shows regional differences; the Australia-Western Pacific region is the most diverse (eleven species), followed by the Mediterranean (seven species) and the Northeastern Atlantic (six species); only four species are known from the Northwestern Tropical Atlantic (NWTA). The morphology of the female fifth leg was examined to explore possible biogeographic trends in the genus; patterns suggest multiple colonization events in the highly diverse regions and a relatively recent radiation in the NWTA, characterized by anchialine forms. The introduction of stephid copepods in the region may be a relatively recent event derived from colonization of benthopelagic ancestral forms and subsequent invasion onto cave habitats. The new species appears to be linked to the strictly anchialine Miostephos.

Taxonomic evaluation of eleven species of Microcyclops Claus, 1893 (Copepoda, Cyclopoida) and description of Microcyclops inarmatus sp. n. from America

Abstract Description and meristic analysis of eleven species of Microcyclops recorded in America were performed based on the examination of type specimens and fresh material. Microscopic analysis of oral appendages, such as the shape and armature of the distal coxal endite of the maxilla, the ornamentation on the caudal surface of the antenna, and the intercoxal sclerites and armament of the inner basis of all swimming appendages, were characteristics that allowed the differentiation between species. Among these species, our study confirmed the synonymy of Microcyclops diversus Kiefer, 1935 with Microcyclops ceibaensis (Marsh, 1919). The results of our observations showed that Microcyclops alius (Kiefer, 1935) is a junior synonym of Microcyclops dubitabilis Kiefer, 1934; the latter being confirmed as a valid species. Also, it is proposed that the records of Microcyclops rubellus (Lilljeborg, 1901) and Microcyclops varicans (Sars, 1863) in America should be revised as there are serious doubts about their distribution in America. The analysis suggested that Microcyclops anceps pauxensis Herbst, 1962 is distinct from Microcyclops anceps var. minor Dussart, 1984 and that both are likely different from Microcyclops anceps anceps (Richard, 1897). Finally a full morphological description of adult females of Microcyclops inarmatus sp. n. is presented.

A new species of Mastigodiaptomus Light, 1939 from Mexico, with notes of species diversity of the genus (Copepoda, Calanoida, Diaptomidae)

Abstract A new species of the genus Mastigodiaptomus Light, 1939, named Mastigodiaptomus cuneatus sp. n. was found in a freshwater system in the City of Mazatlán, in the northern region of Mexico. Morphologically, the females of this new species are distinguishable from those of its congeners by the following combination of features: the right distal corner of the genital double-somite and second urosomite have a wedge-shaped projection, the fourth urosomite has no dorsal projection and its integument is smooth. The males are distinct by the following features: the right caudal ramus has a wedge-shaped structure at the disto-ventral inner corner; the basis of the right fifth leg has one triangular and one rounded projection at the distal and proximal margins, respectively, plus one hyaline membrane on the caudal surface close to the inner margin; the aculeus length is almost the width of the right second exopod (Exp2); and the frontal and caudal surfaces of the right Exp2 are smooth. Furthermore, the analysis of the COI gene of Mastigodiaptomus cuneatus sp. n. has revealed that Mastigodiaptomus albuquerquensis (Herrick, 1895) is its nearest congener, with 18.64% of genetic distance. A key for the identification of the known species of the genus is provided.