Phyllodiaptomusparachristineae, a new species of copepod (Copepoda, Calanoida, Diaptomidae) from the floodplain of the lower Mekong River Basin in Thailand and Cambodia.

Phyllodiaptomus (Phyllodiaptomus) parachristineaesp. nov., a new diaptomid copepod, was collected from 30 sites in the lower Mekong River Basin floodplain in northeastern Thailand and nine sites in Cambodia. The new species is the 13th species of the genus to have been recorded across Asia. It has a wide range of habitats, occurring in small to large, temporary to permanent water bodies, and it can be found at any time of the year. The morphology of the new species is most similar to that of the males of P. (P.) christineae, having a comb on the antepenultimate segment on the right antennule, symmetrical caudal rami, a narrow hyaline lamella on the left P5 basis, a distal accessory spine on the right P5Exp-2, and a single-lobed Enp on the right P5. On the other hand, the males of the new species have second and third urosomites without hair-like setae on the ventral margin, a rounded distal margin of the P5 intersclerite plate, a semi-circular lamella on the right P5 basis, a strong principal lateral spine inserted at the proximal 1/3 of the right P5Exp-2, and a two-segmented left P5Enp. Morphological differences among species in the subgenus Phyllodiaptomus (Phyllodiaptomus) as well as the distribution and habitats of the 13 species and two subspecies of Phyllodiaptomus in Asia are discussed.

Elaphoidella longiramus sp. nov. (Copepoda: Harpacticoida, Canthocamptidae), a new species of cave-dwelling copepod from central Thailand.

A new species of harpacticoid copepod belonging to the genus Elaphoidella is described, based on materials collected from Thae Wa Phithak Cave, Lopburi Province, central Thailand. Specimens of Elaphoidella longiramus sp. nov. were found in a water bucket that was fully filled by dripping water from the cave ceiling. Of the 32 Elaphoidella species recorded from Southeast Asia, E. longiramus sp. nov. is the 14th member of this genus reported from Thailand. The new species is most similar to E. thailandensis by having four well-developed setae on the exopod of the female fifth leg. The endopod of the fourth leg is lacking, and the first leg has a two-segmented endopod in both sexes. However, it is distinguished from E. thailandensis by having elongated caudal rami, the exopod with a seta-like spinule on the inner margin of the female fifth leg, a different setal formula on the third exopod of the second to fourth legs, a different number of teeth on the anal operculum, and a different number of ventral spinules on the anal somite.

New species of Elaphoidella Chappuis, 1929 and Schizopera Sars, 1905 (Copepoda: Harpacticoida) from two caves in northeastern and southern Thailand.

Two new copepod species from two caves in northeastern and southern Thailand are described. Elaphoidella isana sp. nov. and Schizopera paktaii sp. nov. were collected from the unsaturated zone of freshwater pools fed only by dripping water. They are closely related to E. intermedia Chappuis, 1931 and S. validior Sars, 1909, respectively. Elaphoidella isana sp. nov. can be distinguished from its closest relative by the armature of P4 and P5, and by the ornamentation of caudal rami. Schizopera paktaii sp. nov. differs from its relative S. validior in the armature of P1, P5 and caudal rami.

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.

Bryocyclopsasetus sp. n. and the presence of Bryocyclopsmuscicola (Menzel, 1926) from Thailand (Crustacea, Copepoda, Cyclopoida, Cyclopidae).

The description of Bryocyclopsasetus sp. n. and the record of B.muscicola (Menzel, 1926) from Thailand are presented. The new species is most similar to B.maewaensis Watiroyram, Brancelj & Sanoamuang, 2012, the cave-dwelling species described from northern and western Thailand. They share morphological characteristics, such as the free margin of the anal operculum which is ovated and serrate, the same setae and the spines formulae on P1-P4Exp-2 (setae: 5.5.5.4; spines: 3.3.3.3) and Enp-2 of P1-P2, P4 (setae formula 3.4.3) in both sexes. The new species is easily distinguished from B.maewaensis due to typical divergent caudal rami, the absence of coxal seta on P1, and the absence of blunt-tipped setae on P2-P3Exp-2. A dichotomous key to the species of Bryocyclops group I sensuLindberg (1953) is proposed.

A new species of Mongolodiaptomus Kiefer, 1938 from northeast Thailand and a key to the species (Crustacea, Copepoda, Calanoida, Diaptomidae).

This study describes the new species Mongolodiaptomus loeiensissp. n. collected from a temporary pond nearby a cave located in Loei Province, in northeastern Thailand. Mongolodiaptomus loeiensissp. n. is similar to M. calcarus (Shen & Tai, 1965) in the male but can be distinguished from its congeners by the following unique characteristics in the males: (1) the right caudal ramus has 3 ventral chitinous prominences; (2) intercoxal plate of P5 is produced into 2 spine-like lobes on distal margin; (3) the basis of right P5 has a subglobular chitinous prominence on mid-distal caudal surface; and (4) the principal lateral spine on the right Exp-2 P5 is extremely bent at its tip. The occurrence of diaptomid copepods in the study area is discussed and an identification key to worldwide species of the genus Mongolodiaptomus Kiefer, 1938 is presented herein.

Two new stygobiotic species of Elaphoidella (Crustacea: Copepoda: Harpacticoida) with comments on geographical distribution and ecology of harpacticoids from caves in Thailand.

Elaphoidella thailandensis sp. nov. and E. jaesornensis sp. nov., collected during an investigation of cave-dwelling copepod fauna in the northern part of Thailand, are described and figured herein. The new species were collected from pools filled by percolating water from the unsaturated zone of a karstic aquifer in Phitsanulok and Lampang Provinces, respectively. Elaphoidella thailandensis, from Tham Khun cave, is distinguished from its congeners by the two-segmented endopod of pediger 1, the absence of endopod on pediger 4, and the setal formula 4, 5, 6 for the distal exopodal segment of pedigers 2-4. Elaphoidella jaesornensis, from Tham Phar Ngam cave, is distinguished from its most closely related species, E. namnaoensis Brancelj, Watiroyram & Sanoamuang, 2010, by the armature formula of the endopod of pedigers 2-5. The geographical distribution and ecology of Harpacticoida from Thai caves is also presented.