Two new species of Metacyclops Kiefer, 1927 (Copepoda, Cyclopoida) from Thailand and an up-to-date key to the species recorded in Asia

Metacyclops sakaeratensis sp. nov. and M. brancelji sp. nov. are described as being present in the mountainous areas of Northeastern and Southern Thailand, respectively. Two new species resemble M. woni in both sexes, but they are easily distinguished from their Cambodian relative by having: 1) transverse suture on the dorsal surface of the genital double-somite, 2) serrated hyaline frill on the posterior margin of third pedigerous somite, 3) different length / width ratio of caudal ramus, and 4) a row of spinule on caudal surface of intercoxal sclerite of the third swimming legs. The significant differences between M. sakaeratensis sp. nov. and M. brancelji sp. nov. are present in both sexes, including the body size, integumental ornamentation of the body surface, length / width ratio of caudal ramus, armature of the fifth swimming leg, and the male sixth swimming leg. In addition, an up-to-date key to the female of all fifteen species of Metacyclops recorded in Asia is provided.

Two rare species of Danielsseniinae (Copepoda: Harpacticoida: Pseudotachidiidae) from the Kara and East Siberian Seas, with description of their previously unknown sexes

The previously unknown females of Danielssenia spitsbergensis Gee & Huys, 1994 and males of Mucrosenia kendalli Gee & Huys, 1994 (Pseudotachidiidae, Danielsseniinae) are described based on specimens collected in the Kara and East Siberian Seas. Females of D. spitsbergensis exhibit the main diagnostic features of the genus Danielssenia Boeck, 1873 (antennule four-segmented; proximal segment of antennary exopod with one seta; structure of all the mouthparts; absence of an inner seta on exopod-1 of P2–P4; P5 not fused medially and with distinct exopod and baseoendopod, the latter with five setae; genital field with small copulatory pore and short copulatory duct leading to seminal receptacle with paired anterior chambers). At the same time, these specimens also exhibit some distinctive features which are unique for the species but disagree with the generic diagnosis. These peculiarities validate the placing of D. spitsbergensis as species incertae sedis within Danielssenia and point out the necessity of examination of other ‘Danielssenia-like’ forms before the true taxonomic position of this species can be elucidated. Both males and females of M. kendalli exhibit the autapomorphies of the genus, viz. P2 endopod-2 with a mucroniform process reaching almost to end of endopod-3 (this sexually dimorphic character is more pronounced in the males but also present in females); P2 endopod-2 without inner seta; posterior displacement of caudal ramus seta II; presence of tuft of long setules at inner distal corner of caudal ramus; P2 endopod shorter than exopod; P2–P4 exopod-1 without inner seta. Furthermore, some particular features (anal somite and pseudoperculum morphology; female P1 endopod distinctly longer than exopod; P5 exopod with distinct suture on dorsal surface separating it from the baseoendopod; prominent mucroniform process on P2 endopod-2) of the Kara and East Siberian Sea specimens conform fully with the original description of M. kendalli but apparently differ from M. kliei (Smirnov, 1946), the single female of which was collected from the same region and depth. Therefore, the validity and definite status of the specimen described by Smirnov is still a matter of conjecture pending additional findings and, particularly, the discovery of the male.

Attheyella (Canthosella) thailandica sp. nov. (Copepoda, Harpacticoida, Canthocamptidae) from caves in Thailand

During this sampling campaign, the canthocamptid Attheyella (Canthosella) thailandicasp. nov. was collected from various caves in Thailand. The new species is widely distributed in the country and favours habitats, such as phytotelmata and wet soil. Attheyella (Canthosella) thailandicasp. nov. is the second member of the genus to be found in Thailand, after Attheyella (Canthosella) vietnamicaBorutzky (1967), which is most similar to it. Amongst Asian species, both A. (C.) thailandicasp. nov. and A. (C.) vietnamica have identical setal formulae, with a greater number of armatures on the distal endopods of legs 2–4. However, A. (C.) thailandicasp. nov. markedly differs from A. (C.) vietnamica in the insertion point of the dorsal seta and the presence of inner spinules on the caudal ramus. Additionally, the leg 4 endopod is two-segmented in A. (C.) thailandicasp. nov., but one-segmented in A. (C.) vietnamica.

A New Deep-Sea Enhydrosoma (Copepoda, Harpacticoida, Cletodidae) from the Northern Gulf of Mexico

Enhydrosoma texana sp. nov. is described from the northern Gulf of Mexico. The new species is closely related to E. parapropinquum Gómez, 2003 from northwestern Mexico. Both species share several characters including an elongated cylindrical caudal ramus, an abexopodal seta of antennae, the structure of mouthpart appendages, seta formula of thoracic legs P1–P4, the shape of the P5 exopod in the female and the apophysis structure of P3 in males. However, the new species is distinguishable from E. parapropinquum by the shape of the rostrum, number of the antennular segments, the shape of the mandibular palp, the relative lengths of the thoracic legs, the shape of the apophysis of P3 in the male, setal number and length of the P5 exopod of the female, the length of the seta on P5 in the male and the relative lengths of the caudal ramus in both sexes. This is the deepest record of a species in the genus Enhydrosoma.

Redescriptions of Stenocypris major major (Baird, 1859) and Stenocypris major sketi Petkovski & Meisch, 1996 (Ostracoda: Crustacea), with discussion on their taxonomic position

Stenocypris major major (Baird, 1859) and Stenocypris major sketi Petkovski & Meisch, 1996 were encountered in the Eastern part of Thailand. These two taxa are thus re-described based on Thai materials. The taxonomic position of S. major sketi is revised and placed as a separated species due to the distinct features in the valves and the soft parts morphology, especially in the presence of the postero-dorsal expansion on both valves, the different patterns of the posterior inner lamella margins and the caudal ramus morphology. Therefore, S. sketi Petkovski & Meisch, 1996 is erected for S. major sketi. The occurrence of S. sketi in the present contribution is the first report in Thailand and Southeast Asia. This taxon is thus far endemic to the Oriental region. The selected diagnostic characters of the genus Stenocypris are also briefly discussed.

Phyllodiaptomus (Phyllodiaptomus) roietensis, a new diaptomid copepod (Copepoda, Calanoida) from temporary waters in Thailand and Cambodia, with a key to the species

Phyllodiaptomus (Phyllodiaptomus) roietensissp. nov. was collected from temporary water bodies in Roi Et and Nakhon Ratchasima provinces in northeastern Thailand and Kampong Thom Province in central Cambodia. The new species is closely related to Phyllodiaptomus (P.) surinensis Sanoamuang & Yindee, 2001 in that it shares common morphological characters in the males: urosomites 2–3, P5 intercoxal sclerite, right P5 Exp-2, and left P5 Exp. Minor differences on the right antennule, right caudal ramus, P5 basis and Enp exist. The females differ in their Pdg 5, genital double-somite, and P5. An updated key to the species of the genus Phyllodiaptomus Kiefer, 1936 is provided.

A New Species of Monstrillopsis Sars, 1921 (Copepoda: Monstrilloida) with an Unusually Reduced Urosome

Male monstrilloid copepods, described herein as Monstrillopsis paradoxa sp. nov., were collected from the Chuja Islands, Jeju, Korea, using a light trap. They display many of the common features of Monstrillopsis, including large, prominent eyes, an anteriorly positioned oral papilla, and four setae on each caudal ramus. Type-2 modification of the antennules further supports the assignment of the new species to Monstrillopsis. However, the present specimens have an unusually low number of urosomal somites, just three in total, compared to five in males of all congeneric species, and from four (in Cymbasoma) to five in males of all other monstrilloid genera. Up until now, in the Monstrilloida only females of Cymbasoma have been known to have as few as three urosomal somites.

Dolichoectasia of the internal carotid artery terminus, posterior communicating artery, and posterior cerebral artery: The embryonic caudal ramus internal carotid segmental vulnerability legacy

Dolichoectasia of the distal internal carotid artery, posterior communication artery (PCoA) and posterior cerebral artery is an extremely rare abnormality. Dolichoectasia of the internal carotid artery, PCoA and the P1 segment of posterior cerebral artery can be postulated its pathogenesis by the embryological perspective basis from caudal ramus of the internal carotid artery terminus. The pathogenesis and treatment strategy are not well established. We reviewed and proposed embryological perspective, pathogenesis, clinical setting, radiological findings and management of this rare malformation.