Endopodal Segment Of Leg Research Articles

Redescription of Hatschekia exigua Pearse, 1951 (Copepoda: Hatschekiidae), parasitic on the Squirrelfish Holocentrus adscensionis (Osbeck, 1765) (Actinopterygii: Holocentridae) off Ceará, Northeastern Brazil, with first description of the male.

The original description of Hatschekia exigua Pearse, 1951 neglected innumerous features of taxonomic value as well as morphometric data and illustrations. Posteriorly, other author tried to access the type material, but their poor state of preservation compromised a detailed redescription. Since then, this species is in need for new morphological data, mainly from fresh material. In the present work, three specimens of Holocentrus adscensionis from Mucuripe Bay, Fortaleza, State of Ceará, Northeastern Brazil, were parasitized by copepods on their gills. Parasites were fixed and preserved in 80% ethanol and cleared in 85% lactic acid for morphological observations using light microscopy. The females were identified as Hatschekia exigua by the cephalothorax representing about one-fourth of total body length, with lateral margins expanded into lateral lobes, first exopod with basal segment armed with one outer setae and terminal segment with three setae, first endopod with basal segment unarmed and terminal segment with five setae, leg 3 reduced to two setae and leg 4 reduced to single seta. Comparison with the type series revealed morphological differences in trunk and small appendages, which may be related to alterations in the specimens, caused by the mounting methodology and poor preservation. A detailed morphological analysis of the male revealedfor the first time that they differ from their closest congeners by having five setae on the last endopodal segment of leg 1, by smooth intercoxal sclerites on legs 1 and 2and by a proximolateral process on the third segment of antenna. Moreover, this work represents the first report of H. exigua in Brazil and the first hatschekiid copepod found off the coast of Ceará, highlighting that the diversity of Hatschekiidae in this oceanographic region still needs further investigation.

Description of a new Scottocheres Giesbrecht, 1897 (Copepoda, Siphonostomatoida, Asterocheridae), including an emended diagnosis and key for the genus

The siphonostomatoid copepod genus Scottocheres was established by Giesbrecht in 1897 and now includes nine species. Consequently, these new species introduced new characteristics that must be considered to define the genus. This study provides an emended diagnosis of the genus, describes a new species, discusses the geographic distribution and hosts of the genus, and includes a key to the species. The new species was found associated with the sponge Callyspongia in Todos-os-Santos Bay and can be distinguished from its congeners by a set of characters that includes the presence of a unique seta on the inner margin of the second endopodal segment of legs 1 to 4 and only two spines on the outer margin of third endopodal element of leg 1.

Two new species of Cryptopontius Giesbrecht, 1899 (Copepoda, Siphonostomatoida, Artotrogidae) associated with invertebrates from Northeastern Brazil.

Cryptopontius is the most species-rich genus in the family Artotrogidae with 25 species, being recorded in almost all oceans, except in the Arctic. However only three species of this genus have been recorded from the Brazilian coast, all of them along the coast of Pernambuco state. This study describes two new species of the genus. Cryptopontius phyllogorgius sp. nov. differs from other species by having 9-segmented antennule, and nine elements on the third exopodal segment of leg 4. Cryptopontius pentadikos sp. nov. differs from its congeners by having five expressed antennulary segments proximal to fused ancestral IX-XII, two setae on second endopodal segment of leg 1, eight elements on third exopodal segment of leg 1 and the free segment of leg 5 with two setae. A key to species of the genus Cryptopontius is provided.

Acusicola margulisae n. sp. (Copepoda: Ergasilidae) from freshwater fishes in a Nicaraguan crater lake based on morphological and molecular evidence.

The ergasilid copepod Acusicola margulisae n. sp. is described based on material from three species of cichlid, Amphilophus citrinellus (Günther), Parachromis managuensis (Günther), and Oreochromis sp., and from the poecilid Poecilia mexicana (Steindachner), in the crater Lake Asososca León, Nicaragua. This constitutes the 15th species described in the genus Acusicola Cressey, 1970. The new species differs from all its congeners by the relatively longer first endopodal segment of leg 1, and the size and number of setae on second endopodal segment of leg 1. We provide the first gene sequence for a species of Acusicola. To examine the intraspecific genetic variation of the new species collected from different host species, sequences of the mitochondrial barcode region cox1 were generated. In addition, partial regions of the 18S and 28S ribosomal RNA genes were sequenced and used to infer the phylogenetic relationships of the genus Acusicola within the family Ergasilidae Burmeister, 1835. The phylogenetic trees yielded the isolates of Acusicola margulisae n. sp. as a reciprocally monophyletic lineage, and as the sister taxa of five genera of ergasilid copepods. The genus Ergasilus von Nordmann, 1832 was recovered as a paraphyletic group. These analyses indicate that phylogenetic relationships are not yet well resolved and more representative species and genera of the family are required to provide a robust classification of this highly diverse group of copepods.

Description of Barathricolathermophilus, a new species from a deep-sea hydrothermal vent field in the Indian Ocean with redescription of the Barathricola type species (Crustacea, Copepoda, Cyclopoida).

Re-study of the type species of the genus Barathricola Humes, 1999 (Copepoda, Cyclopoida, Schminkepinellidae) described from the Pacific Ocean (Juan de Fuca Ridge), and study of the species Barathricolathermophilussp. nov. from a deep-sea hydrothermal vent field on the Central Ridge in the Indian Ocean revealed a derived feature and widespread geographic distribution of this deep-sea genus of cyclopoids. The derived feature of Barathricola is the sexually dimorphic third endopodal segment of leg 3 possessing a small outer terminal spine together with spine-like outgrowths on this segment. The new species differs from Barathricolarimensis Humes, 1999 in not expressing sexual dimorphism in leg 5, having three spines and one seta on its exopod in both sexes (B.rimensis has three spines and one seta on the female exopod but three spines and two setae on the male exopod) and in having broader caudal rami which are 8.9 times longer than wide in the female (this ratio for B.rimensis is 11). An amended diagnosis of the genus Barathricola, a key and a table of morphological differences for all species of Schminkepinellidae are given.

A new species of Hamaticolax (Copepoda: Bomolochidae) from Helicolenus dactylopterus (Delaroche, 1809) (Scorpaeniformes: Sebastidae) in NW Mediterranean deep waters and notes on patterns of host use and host-specificity of the genus.

Hamaticolax juanji n. sp. is described from specimens collected from the blackbelly rosefish Helicolenus dactylopterus Delaroche 1809 (Scorpaeniformes: Sebastidae). It is the second Hamaticolax species described and reported from the Mediterranean Sea, after Ha. resupinus Pérez-i-García, Carrassón and Boxshall, 2017. It is distinguished from Ha. resupinus by the presence of only one dorsal naked seta on the third segment of the antennule (vs. four), two unequal short naked setae in distal part of the antenna (vs. four), and the absence of a minute spine on the third endopodal segment of leg 1, among others. It is differentiated from Ha. prolixus Cressey 1969 by a comparatively reduced fourth pedigerous somite, the presence of two naked setae on the third segment of the antennule (vs. three), two naked setae and three curved claws in the distal part of the apical segment of the antenna (vs. three and four), an outer naked seta on the basis of leg 2, and by larger length/width ratio of the third endopodal segment, among others. Hamaticolax juanji n. sp. also has relatively longer inner setae on the first and second endopodal segments of leg 4 than the two former species. Patterns of host-use and host-specificity of the genus Hamaticolax are also discussed. The frequently observed low host-specificity of its members may be better explained by host ecological similarity and host availability phenomena, rather than by host phylogenetic distance.

First Record of the Family Peltidiidae (Copepoda; Harpacticoida) from the Gulf of Mexico, with the Description of a New Species ofPeltidium

Female harpacticoid copepod specimens representing an undescribed species of Peltidium (Peltidiidae) were found from an unidentified species of Sargassum during a series of samplings carried out in 2014 in Tampa Bay, Florida, U.S.A. The new species, Peltidium camilae, is similar to P. nichollsi Geddes, 1968 and P. lerneri Geddes, 1968. These species share the female exopod of leg 5 with two inner and three apical setae, the second endopodal segment of leg 1 with three setae, and the third endopodal segment of legs 2-4 with three, five and four setae, respectively. Peltidium camilae n. sp. can be distinguished from P. nichollsi and P. lerneri by having a shorter endopod relative to the exopod on legs 2-4, apical claws on the terminal exopodal segment of leg 1 that are as long as the first exopodal segment of leg 1, and subequal middle and inner apical setae on the exopod of leg 5. This is the first record of the family Peltidiidae from the Gulf of Mexico.

New species of Leptocaris and a new record of Darcythompsonia inopinata (Harpacticoida: Darcythompsoniidae) from Colombia

Se hallaron tres especies de copépodos harpacticoides de la familia Darcythompsoniidae en muestras de agua tomadas de la Bahía del Rodadero (Colombia). Leptocaris colombiana sp. nov. pertenece al grupo brevicornis, y se caracteriza por la anténula de cinco segmentos, somita genital y tercer urosomita de la hembra discretos (no fusionados), ramas caudales con seis setas, exópodo de la antena representado por dos setas, alobase de la antena sin seta abexopodal, palpo mandibular reducido a una seta, primer segmento del endópodo de la pata uno con una seta interna y segundo segmento con dos setas apicales, y pata cinco con tres setas. Leptocaris vicina sp. nov. pertenece al grupo mangalis y es similar a L. stromatolicola en la fórmula de setas y espinas de las patas uno a cuatro, pata cinco de la hembra con dos setas internas pequeñas de la misma longitud y un elemento externo largo, anténula de la hembra de cinco segmentos, alobase de la antena con una seta abexopodal, exópodo de la antena reducido a dos setas, palpo mandibular reducido a una seta, maxila con dos enditos. Estas dos especies pueden distinguirse por la forma del opérculo anal, por la longitud relativa de los segmentos del endópodo de las patas dos y tres, y por la espina interna del segmento del endópodo de la antena. Finalmente, el registro de Darcythompsonia inopinata en el norte de Colombia representa un continuo a lo largo de la costa caribeña del dominio del Pacífico, subregión Brasileña.

Redescription of two species of Asterocheres Boeck, 1860 (Copepoda: Siphonostomatoida), A. corneliae Schirl, 1973 and A. boeckii (Brady, 1880), and proposal of a new genus for Asterocheres fastigatus Kim, 2010

<p class="HeadingRunIn" style="margin-top: 0cm; text-align: justify; text-justify: inter-ideograph; line-height: 12.0pt; page-break-after: auto;"><span style="font-size: 10pt;">Asterocheres <span style="font-size: 10pt;">Boeck, 1860 is the largest genus in the family Asterocheridae and includes approximately 96 nominal species. Nevertheless, according to Kim (2010), the current assignment of twelve of these species to Asterocheres is debatable, and fifteen species are too incompletely described for reliable comparisons to be made. In this paper, two species, A. corneliae Schirl, 1973 and A. boeckii (Brady, 1880), are redescribed and compared with their congeners. As a result of the comparison between A. boeckii and A. fastigatus Kim, 2010, a new genus, Kimcheres, is erected to accommodate the only species of Asterocheres displaying the armature formula (0-1) on the second endopodal segment of leg 4. The taxonomic position of A. longisetosus Nair & Pillai, 1984, considered as species inquirenda by Kim (2010), is discussed. Examination of the original description and illustrations, especially the antennules and the mandible, casts doubts on the validity of the species.<p class="MsoNormal">Asterocheres Boeck, 1860 is the largest genus in the family Asterocheridae and includes approximately 96 nominal species. Nevertheless, according to Kim (2010), the current assignment of twelve of these species to Asterocheres is debatable, and fifteen species are too incompletely described for reliable comparisons to be made. In this paper, two species, A. corneliae Schirl, 1973 and A. boeckii (Brady, 1880), are redescribed and compared with their congeners. As a result of the comparison between A. boeckii and A. fastigatus Kim, 2010, a new genus, Kimcheres, is erected to accommodate the only species of Asterocheres displaying the armature formula (0-1) on the second endopodal segment of leg 4. The taxonomic position of A. longisetosus Nair & Pillai, 1984, considered as species inquirenda by Kim (2010), is discussed. Examination of the original description and illustrations, especially the antennules and the mandible, casts doubts on the validity of the species.

A new deep-sea genus and species of the family Ecbathyriontidae (Copepoda: Siphonostomatoida) from the Gorda Ridge (North Pacific Ocean)

Adult females of Bathygordion cliffus new gen. and new sp. belonging to the family Ecbathyriontidae Humes, 1987 are described from the Gorda Ridge of the North Pacific Ocean. The copepods were found at depth of 2701 m on the margin of a hydrothermal vent field (Sea Cliff, GR-14) among invertebrates colonizing wood blocks deployed for 2 years. The new genus differs from the only monotypic genus Ecbathyrion Humes, 1987 reported from hydrothermal vents of the Galapagos Rift and the East Pacific Rise in a number of morphological features (such as three articulating abdominal somites, mandible with 1 palp bearing setae, base of leg 1 with inner seta, distal exopodal segment of leg 4 with four inner setae, leg 5 2-segmented), suggesting long evolutionary history of the deep-sea family endemic to hydrothermal vents of the East Pacific. The derived feature of the new genus is the presence of one terminal spine on the distal endopodal segment of leg 3 (instead of bearing two terminal setae in Ecbathyrion). The diagnosis of the family Ecbathyriontidae is emended.

A new species of Bestiolina (Copepoda: Calanoida: Paracalanidae) from the Northwestern Atlantic with comments on the distribution of the genus

A new species of the paracalanid copepod genus BestiolinaAndronov, 1991 is described from Laguna Mandinga, a coastal lagoon system of the eastern coast of the southern Gulf of Mexico. Bestiolina mexicana n. sp. most closely resembles B. sinica (Shen & Lee, 1966) and B. arabicaAli, Al-Yamani, and Prusova, 2007 but can be distinguished from these and other known congeners by the number and presence of posterior surface spinules on the second and third exopodal segments of female legs 2–4, and the number of spinules on the anterior surface of the second endopodal segment of legs 2–4. This is the only species of the genus with 3, 0, 0 spines on the exopodal segments of leg 2 and 2, 3 spines on the second endopodal segments of legs 3 and 4, respectively. The mandible blade of B. mexicana n. sp. has 2 large supplementary teeth which have not been hitherto observed in the other species of the genus. This is the smallest species in the genus and has some reductions in the armature of the mouthparts. The new species has been known to occur only from this lagoonal system in the Gulf of Mexico and it is the first species of Bestiolina recorded in the northern Atlantic Ocean. The presence of a member of this primarily Indo-Malayan genus in the northwestern Atlantic probably represents the result of its final divergence and is explained by dispersal processes related to the Pliocene conditions.

Two New Species of Clausidiidae (Copepoda, Poecilostomatoida) from Korea

Two new species of Clausidiidae, each belonging to the genera Clausidium Kossmann, 1875 and Hippomolgus G. O. Sars, 1917, are described from Korea. Clausidium maximus n. sp. is an associate of a burrowing decapod of the genus Callianassa living on the Korean coast of the Yellow Sea and has, as diagnostic characters, two inner setae on the second endopodal segment of legs 2-4, nine elements on the third exopodal segment of leg 4, an inner seta on the second exopodal segment of male leg 1, and a relatively large body size, exceeding 2.0 mm in the female. Hippomolgus limiticus n. sp. was found in the bottom sediments in the East China Sea. It is similar to H. furcifer G. O. Sars, but distinghuishable from the latter species by having shorter caudal rami, 4-segmented female maxilliped, and inner coxal spine (instead of seta) on legs 2 and 3. This is the first record on the genera Clausidium and Hippomolgus in the West Pacific.

First record of the genus Nitocrella Chappuis, 1923 (Copepoda, Harpacticoida, Ameiridae) from India, with a new phreatic species

Nitocrella galassiaen. sp. is described from phreatic waters in Andhra Pradesh state located in southeastern peninsular India. This is the first representative of the genusNitocrellaChappuis, 1923, described from the Indian subcontinent. Following Petkovski’s (1976) revision of the genusNitocrellas. str., the new species is assigned to thechappuisi-group of species. It differs from all other members of this group by a unique combination of the following characters: the male leg 1 basis has a short claw-like inner spine; the second exopodal segment of legs 1-4 has an inner seta; the apical endopodal segment of legs 2 and 4 has a single seta; leg 5 exopod in both sexes has three setae, and the baseoendopodal lobe has three setae in the female and two setae in the male; the male fifth antennular segment has a large aesthetasc; and the caudal ramus is 1.5 times as long as its greatest width and about 0.7 times as long as the anal somite. Among the hitherto known species of thechappuisi-group, the new species shows an allegedly close relationship with the IranianN. petkovskiiPesce, 1980. A brief note on the ecology of the new species is also added.

Metacyclops woni n. sp., a New Cyclopoid Species (Copepoda: Cyclopoida: Cyclopidae) from Cambodia

A new cyclopoid species belonging to the genus Metacyclops Kiefer, 1927 is described, based upon the specimens from a temporary pool in a forest of Mt. Phnom Domnak Dambouk, situated in the southwestern part of Cambodia. Metacyclops woni sp. nov. is characterized by its quite short caudal rami, about 2.5 times longer than wide, with a spinule row on anterior quarter of lateral margin. This new species belongs to the species group with the spine formula 3,4,4,3 of swimming legs 1-4. Among the members of the species group with the combination of characters of 11-segmented antennule and a single apical spine on the second endopodal segment of leg 4, it most resembles M. deserticus Mercado-Salas and Suarez-Morales, 2013 from Mexico in carrying an outermost caudal seta slightly longer than the innermost caudal seta and an apical spine on the second endopodal segment of leg 4 slightly shorter than the segment. However, it differs clearly from the present new species by much longer caudal rami with lateral caudal seta at nearly halfway of lateral margin of the ramus and smooth posterior margin of intercoxal sclerites of legs 1-4. This is the first record of the genus Metacyclops from Cambodia and the fourth one from Southeast Asia.

A new marine cyclopoid copepod of the genus Neocyclops (Cyclopidae, Halicyclopinae) from Korea.

A new cyclopoid species of the genus Neocyclops Gurney, 1927 is described. Type specimens were collected from a beach on south-western coast of the Korean Peninsula by rinsing intertidal coarse sandy sediments. Neocyclops hoonsooi sp. n. is most characteristic in showing the conspicuous chitinized transverse ridges originating from the medial margins of the coxae of all swimming legs. The new species is most similar to Neocyclops vicinus, described from the Brazilian coast, and Neocyclops petkovskii, from Australia. All three species share a large body size (more than 750 µm long), the presence of an exopodal seta on the antenna, two setae on the mandibular palp, the same seta/spine armature on the third endopodal segment of leg 3 (3 setae + 3 spines), and the fairly long inner distal spine on the third endopodal segment of the female leg 4. However, Neocyclops hoonsooi sp. n. differs from both species by the much shorter caudal rami (less than 1.7 times as long as wide) and the shorter dorsal caudal seta VII. Furthermore, Neocyclops hoonsooi is clearly distinguished from Neocyclops vicinus by the 10-segmented antennule (vs 12 segments in Neocyclops vicinus), and from Neocyclops petkovskii by the elongate inner distal spine on leg 5 exopod and the 3-segmented leg 5 in male (vs 4-segmented in Neocyclops petkovskii). A tabular comparison of characters separating Neocyclops hoonsooi from its closest allies and a key to Neocyclops species from the Indo-Pacific Ocean are provided. This is the first record of the genus Neocyclops from the northern Pacific.

A new genus of speleophriid copepod (Copepoda: Misophrioida) from a cenote in the Yucatan, Mexico with a phylogenetic analysis at the species level.

A new genus and species of speleophriid copepod, Mexicophria cenoticola gen. et sp. nov., is described based on material collected from a cenote in the Yucatan Peninsula of Mexico. It is characterised by relatively reduced fifth legs that are located adjacent to the ventral midline in both sexes, by the possession of a bulbous swelling on the first antennulary segment in both sexes, and by the reduced setation of the swimming legs. The presence of just one inner margin seta on the second endopodal segment of legs 2 to 4 is a unique feature for the family. A phylogenetic analysis places the new genus on a basal lineage of the family together with its sister taxon, Boxshallia Huys, 1988, from Lanzarote in the Canary Islands, and recovers the existing genera as monophyletic units. The zoogeography is discussed at local, regional, ocean basin and global scales.

Two new species of asterocherid (Copepoda: Siphonostomatoida) associated with a sponge from the Strait of Messina, Italy: taxonomic and ecological traits

Two new species of asterocherid associated with sponges are described from the Mediterranean Sea. They are Psilomyzon laetitiae sp. nov. and Psilomyzon sarcotragusicola sp. nov. The genus Psilomyzon consists of only one known species, P. pauciseta. The two new species can be easily distinguished from the cogener species by reduction of the endopod of leg 4. In P. pauciseta the leg 4 endopod is 3-segmented, with the third segment reduced; in both new species it is 2-segmented, with the second segment carrying an inner projection, possibly homologous to the third segment of the leg 4 endopod of P. pauciseta. In the two new species, the bifid outer process on male leg 4 second endopodal segment seems to be serially homologous to the similar processes on the same segment in legs 1–3, whereas the inner projection may represent a vestigial element of the third endopodal segment of leg 4.http://zoobank.org/urn:lsid:zoobank.org:pub:33BF0653-BBA9-426B-B365-5D8C62DFD44A

Three artotrogids (Crustacea: Copepoda: Siphonostomatoida) from the Ross Sea, Antarctica

The Artotrogidae, one of the most primitive of siphonostomatoid families, consists currently of 117 species in 21 genera. Most of these species (65%) are poorly or incompletely described since they have been rarely recorded in recent decades and, when encountered, have been found in very low numbers. During the 19th Italian Antarctic Expedition, with the RV Italica, to the Ross Sea in austral summer 2004, some artotrogid copepods were collected. This paper redescribes two species of artotrogid copepods, which are known only from the Southern Ocean, Neobradypontius neglectus and Cryptopontiuslatus, and describes for the first time a male of the genus Neobradypontius. Furthermore, a new species is described and added to Sestropontius, increasing the number of known species of this genus to three. The main discrepancies between the original descriptions and the specimens of the two species collected from the Ross Sea redescribed here were on the armature of the antennary exopod and leg 5. The new species, Sestropontius italicae, shares with its most similar congener, S. mckinnoni, the armature of the third endopodal segment of leg 1 and leg 2 and that of the third exopodal segment of leg 4. However, the segmentation of the antennae and the armature on the antennary exopod are different.Keywords: Antarctica; Artotrogidae; redescription; Neobradypontius; Sestropontius; CryptopontiusTo access larger versions of Figs. 2–12 please see the supplementary file in the column to the right (under Article Tools)(Published: 8 December 2014)Citation: Polar Research 2014, 33, 24135, http://dx.doi.org/10.3402/polar.v33.24135

A new species of Peltidium Philippi, 1839 (Crustacea, Copepoda, Harpacticoida) from the Pacific coast of Mexico

During the analysis of phytal meiobenthic samples collected from a rocky-sandy beach in the state of Nayarit, in the Mexican Pacific, several specimens of harpacticoid copepods were obtained and taxonomically examined. These specimens were found to represent an undescribed species of the peltidiid genus Peltidium Philippi, 1839. The new species, Peltidium nayarit sp. n. is described herein. It resembles Peltidium nichollsi Geddes and Peltidium lerneri Geddes from Bahamas but also the widespread Peltidium speciosum Thompson & Scott and Peltidium purpureum Philippi. The new species from the Mexican Pacific differs from its known congeners by its possession of a unique combination of characters, including a modified pectinate seta on the antennary exopod, three terminal setae on the second endopodal segment of leg 1, third exopodal segment of leg 1 with three elements, inner terminal claw twice as long as outer claw, female fifth leg with 5 exopodal setae, exopodal setae I-III stout, spinulose and seta IV being as long as seta V. This is the second species of the family known to be distributed in the Eastern Tropical Pacific and in Mexico. Pending additional data, the distribution of this species appears to be restricted to this area of the Mexican Pacific.

A new species of Metacyclops Kiefer, 1927 (Copepoda, Cyclopidae, Cyclopinae) from the Chihuahuan desert, northern Mexico

A new species of the freshwater cyclopoid copepod genus Metacyclops Kiefer, 1927 is described from a single pond in northern Mexico, within the binational area known as the Chihuahuan Desert. This species belongs to a group of Metacyclops species with a 3443 spine formula of swimming legs. It is morphologically similar to Metacyclops lusitanus Lindberg, 1961 but differs from this and other congeners by having a unique combination of characters, including a caudal rami length/width proportion of 3.5–3.8, a innermost terminal seta slightly longer than the outermost terminal seta, intercoxal sclerites of legs 1-4 naked, a strong apical spine of the second endopodal segment of leg 1 and one row of 6-8 small spinules at the insertion of this spine. The finding of this species represents also the first record of the genus in Mexico and the third in North America, where only two other species, Metacyclops gracilis (Lilljeborg, 1853)and Metacyclops cushae Reid, 1991 have been hitherto reported. This is also the first continental record of a species of Metacyclops from an arid environment in the Americas. This species appears to be endemic to the Chihuahuan Desert, thus emphasizing the high endemicity of this area.