Saturday, March 4, 2023

[Diplopoda • 2020] Eutrichodesmus cambodiensis • A New Micropolydesmoid Millipede of the Genus Eutrichodesmus Silvestri, 1910 (Polydesmida: Haplodesmidae) from Cambodia, with A Key to Species in mainland Southeast Asia


Eutrichodesmus cambodiensis Srisonchai & Panha, 

in Srisonchai, Likhitrakarn, Sutcharit, Jeratthitikul, Siriwut, Thrach, Chhuoy, Ngor & Panha, 2020

The micropolydesmoid millipede family Haplodesmidae is here recorded from Cambodia for the first time through the discovery of the first, new species of the genus Eutrichodesmus Silvestri, 1910: E. cambodiensis sp. nov. This new species is described from two limestone habitats in Kampot Province, based on abundant material. It is easily distinguished from all related congeners by the following combination of characters: body greyish-brown; limbus roundly lobulate; solenomere partially divided from acropodite by a digitiform lobe, but without hairpad. Brief remarks on the previously-proposed “pecularis-group” are provided and a second group, the “demangei-group”, is established and discussed on the basis of morphological evidence, updating the number of recognised species groups of Eutrichodesmus to two. Detailed morphological illustrations, photographs and a distribution map, as well as remarks on its habitat and mating behaviour of the new species are presented. Furthermore, the current distributions of all 55 presently-known species of Eutrichodesmus are provided and a key to all 23 species that occur in mainland Southeast Asia is given.

Keywords: Karst, new species, Southeast Asia, taxonomy

Order Polydesmida Pocock, 1887
Suborder Polydesmidea Pocock, 1887

Family Haplodesmidae Cook, 1895

Genus Eutrichodesmus Silvestri, 1910
Type species: Eutrichodesmus demangei Silvestri, 1910

Photographs of live Eutrichodesmus cambodiensis sp. nov., paratypes (CUMZ–hapld00002)
A pairs of mating couples B male and C mating couple. Not to scale.

Eutrichodesmus cambodiensis Srisonchai & Panha, sp. nov.
Diagnosis: Body with incomplete volvation; metaterga with three transverse rows of regular and round tubercles, but no mid-dorsal projection (outgrowth) on metaterga; distofemoral process on gonopod telopodite very short, inconspicuous. Similar in all these characters to E. griseus Golovatch et al., 2009, but differs in having (1) live specimens and freshly preserved material pale greyish-brown or pale brown in colour; (2) the limbus crenulate, but not spinulate, crenulations being slightly longer than broad; (3) the acropodite curved and long, unciform, attenuated near tip; with a free solenomere starting from about midway; and (4) the solenomere digitiform, papillate, without hairpad.

Etymology: The specific epithet reflects the name of the country “Cambodia” where all specimens were collected and to which the new species appears to be endemic; adjective.

Habitat at the type locality of Eutrichodesmus cambodiensis sp. nov. 
A limestone outcrop B, C humid rock wall, sinkholes and crevices
D co-occurrence of the new species with microsnail, Hypselostoma cambodjense Benthem Jutting, 1962
and E mating couple (male on top).

Ruttapon Srisonchai, Natdanai Likhitrakarn, Chirasak Sutcharit, Ekgachai Jeratthitikul, Warut Siriwut, Phanara Thrach, Samol Chhuoy, Peng Bun Ngor and Somsak Panha. 2020. A New Micropolydesmoid Millipede of the Genus Eutrichodesmus Silvestri, 1910 from Cambodia, with A Key to Species in mainland Southeast Asia (Diplopoda, Polydesmida, Haplodesmidae). ZooKeys. 996: 59-91. DOI: 10.3897/zookeys.996.57411