Redescription of two species of (Copepoda, Cyclopoida) and use of ordination models to classify American species.

Two species of the freshwater copepod genus are redescribed, Dussart, 1984, and Dussart, 1984 from type specimens. Redescription includes the microstructure of intercoxal sclerites and the basipodites of thoracic appendages, as well as the urosomal microstructure. According to the cluster (UPGMA and Euclidean distance) and PCA analyses performed, it was possible to improve the resolution between the American species by considering characters such as the distal region of antennal basis, the maxillary ornamentation, and the thoracic appendages, especially the intercoxal sclerites and medial margin of the basipodite of the first to fourth trunk limbs.

Evaluation of arsenic effects on Paracyclops novenarius Reid, 1987: a cyclopoid copepod in central-north of Mexico.

Description and morphological analysis of copepods inhabiting a water body with high arsenic concentrations (32.79 to 62.29 mg L) were performed to identify some effect on the development of individuals due to the arsenic concentrations.

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

A new species of the genus Light, 1939, named 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.

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

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).

An example of how barcodes can clarify cryptic species: the case of the calanoid copepod Mastigodiaptomus albuquerquensis (Herrick).

Background: The freshwater calanoid Mastigodiaptomus is a genus with high richness in the Americas and is composed of nine species, seven recorded in Mexico and four that are apparently endemic to small areas. Mastigodiaptomus albuquerquensis is a common, widely distributed species ranging from the southern USA to Central America. This species can be easily identified by a notable butterfly-like sclerotization on the basis of the right fifth leg of males.

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.

Two new species of the freshwater cyclopoid genera Eucyclops are described, Eucyclops tziscao sp. n. and E.