A new species of Ergasilus Nordmann, 1832 (Copepoda, Ergasilidae) from Brazil

Abstract

A new species of ergasilid copepod, Ergasilus foresti, is described from the zooplankton communities of the upper reaches of Piauí river estuary in northeastern Brazil, and of the Patos lagoon and the Taim hydrological system in southern Brazil. The establishment of the new taxon is justi ed by comparisons with all congeners exhibiting a 2-segmented endopod in the rst leg. This endopod is elongate and bears a unique rosette of spinules on the posterior surface of the distal segment. RÉSUMÉUne nouvelle espèce de copépode de la famille des Ergasilidae, Ergasilus foresti, est décrite, en provenance des communautés zooplanctoniques de l'estuaire du euve Piauí, au nord-est du Brésil, et de la lagune Patos et du système hydrologique de Taim au sud du Brésil. L'établissement de ce nouveau taxon est justi é par comparaison avec tous les congénères ayant une première paire de pattes à endopodite bisegmenté. Dans la nouvelle espèce, cet endopodite porte une rosette de spinules sur la face postérieure du segment distal.

A new species of Ergasilus (Copepoda: Cyclopoida: Ergasilidae) from coastal fishes of the Mexican Pacific

“…The new species, E. davidi, shows a combination of characters that includes: endopod of first leg with two segments, endopod of fourth leg with three segments, and first antennulary segment with a single seta. Boxshall et al (2002) stated that the possession of a first leg with a 2-segmented endopod, as in the new species, is an apomorphy shared by 24 known species of Ergasilus. Further, out of this group of species, only half of them have also a 2-segmented endopod on the fourth swimming legs; these 12 species are listed by Boxshall et al (2002).…”

“…Boxshall et al (2002) stated that the possession of a first leg with a 2-segmented endopod, as in the new species, is an apomorphy shared by 24 known species of Ergasilus. Further, out of this group of species, only half of them have also a 2-segmented endopod on the fourth swimming legs; these 12 species are listed by Boxshall et al (2002). Because this character (2-segmented fourth leg endopod) is not present in the new species, we compared its morphology with the remaining group of species with 2-segmented first leg endopod and 3-segmented fourth leg endopod.…”

“…However, E. cerastes differs from the new species in the armature of the first antennulary segment, with 3 setae rather than one in E. davidi, in the presence of a tooth-like process on thesecond antennal segment, this element being smaller and inserted in a different position in the new species, in the relative length of the fourth antennal segment, which is 0.6-0.7 as long as the third segment (Roberts 1969(Roberts , 1970 vs. 0.4-0.5 in E. davidi, in the ornamentation of the mandibular blades (symmetrically denticulate in E. cerastes vs. foliose, curved elements arranged in relatively irregular pattern in the new species), and in the armature of the maxilla (with normal spinules vs. mixed pattern of blunt elements and acute spinules). Among the South American species compared herein, the new species has also some important affinities with the Brazilian species E. foresti, including the proportions of the antennal segments and the presence of a prominent conical process on proximal position, the distal inner setae of the second endopodal segment being shorter than the proximal setae, and the presence of a rosettelike arrangement of spiniform elements on the same segment (see Boxshall et al 2002). However, both species differ in the general proportions of the body (narrow prosome in E. foresti vs. a wide, robust prosome in the new species), in the structure of the first endopodal segment of first legs (with expanded inner margin vs. normal condition in E. davidi), in the armature of the antennule (1, 11, 5, 4, 2 + 1ae, 7 + 1ae in E. foresti vs. 1, 11, 5, 3, 2 + 1 ae, 5 + 1 ae) and in the armature of the second antennal segment (a curved, blunt-ended inner spine in E. foresti, whereas this element is low, not curved in the new species).…”

“…Some specimens were dissected under the stereomicroscope; drawings were prepared using a camera lucida mounted on an E-200 Nikon compound FOLIA PARASITOLOGICA 55: 224-230, 2008 microscope. Copepod body and appendage terminology follows Boxshall et al (2002). The use of ecological and infection rate indicators including abundance, intensity, and prevalence follows Bush et al (1997).…”

“…According to Boxshall et al (2002) and Tavares and Luque (2005), the 12 species sharing this combination of characters include eight neotropical forms known from South America: E. argulus Cressey, 1970, E. caraguatatubensis Amado et Rocha, 1995, E. colomesus Thatcher et Boeger, 1983, E. cyanopictus Carvalho, Fig. 3.…”