Abstract
Two obligate cave-dwelling species of cyclopoid copepods (Copepoda, Cyclopoida) were discovered inside caves in central Thailand. Siamcyclops cavernicolus gen. et sp. nov. was recognised as a member of a new genus. It resembles Bryocyclops jankowskajae Monchenko, 1972 from Uzbekistan (part of the former USSR). It differs from it by (1) lack of pointed triangular prominences on the intercoxal sclerite of the fourth swimming leg, (2) mandibular palp with three setae, (3) spine and setal formulae of swimming legs 3.3.3.2 and 5.5.5.5, respectively, and (4) specific shape of spermatophore. Metacyclops thailandicus sp. nov. resembles M. cushae Reid, 1991 from Louisiana (USA). It differs from it by (1) distal segment of the endopod of the fourth swimming leg with one apical spine, (2) the fifth swimming legs with one broad segment, (3) the spine formula of the distal segment of the exopod of the swimming legs 3.4.3.3, and (4) well developed anal operculum reaching articulation with caudal rami. Detailed descriptions of the habitats of the new species and up-to-date keys to the genera and subgenera of the Bryocyclops and Microcyclops groups are provided, along with an updated list of obligate groundwater species of Copepoda in Southeast Asia.
Highlights
Current knowledge of freshwater cyclopoid copepods in Thailand and neighbouring countries is still insufficient
Siamcyclops cavernicolus gen. et sp. nov. was recognised as a member of a new genus
For the reasons listed above, we propose the establishment of the new genus Siamcyclops gen. nov. to accommodate the new stygobiotic species from Thailand
Summary
Current knowledge of freshwater cyclopoid copepods in Thailand and neighbouring countries is still insufficient. The most recent list of freshwater Cyclopoida from Thailand contains 45 taxa, most of them with Afroand Indo-Eurasian distributions (Alekseev & Sanoamuang 2006). Two new cyclopoid species from Thailand were described, Afrocyclops henrii from freshwater (Alekseev & Sanoamuang 2006) and Apocyclops ramkhamhaengi from brackish water (Chullasorn et al 2008). In comparison with other zoogeographical regions, the relatively low number of known and new taxa indicates the need for more intensive sampling in different regions and habitats in Thailand, including porous and fractured subterranean habitats, to improve our knowledge of copepod diversity in the Oriental region (Boxshall & Defaye 2008) as well as of subterranean diversity on a global scale (Culver & Sket 2000)
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