Abstract
The semi-aquatic freshwater earthworm genus Glyphidrilus Horst, 1889 from Thailand was investigated based on extensive recent collecting. The species in this genus were characterized by their external and internal morphological characters of the location of wings, genital openings, genital organ structures and their locations, as well as the dimensions of body length and number of segments. Several type specimens were compared with both previous and newly collected materials. Ten new species are described from several river systems in Thailand; as Glyphidrilus borealis sp. n., Glyphidrilus chaophraya sp. n., Glyphidrilus chiensis sp. n., Glyphidrilus huailuangensis sp. n., Glyphidrilus kratuensis sp. n., Glyphidrilus quadratus sp. n., Glyphidrilus trangensis sp. n., Glyphidrilus wararamensis sp. n., Glyphidrilus vangthongensis sp. n. and Glyphidrilus vesper sp. n. Each species is endemic to a single river system. All 26 previously described species are re-described, and eight lectotypes have been designated. An identification key and a morphological comparison summary are provided.
Highlights
Species of the genus Glyphidrilus Horst, 1889 are unfamiliar earthworms living on an ecotone between terrestrial and freshwater ecosystems of rivers, streams, canals, ponds, swamps or even in paddy rice system
The new species was found on the canal connected to waterfall in sandy loam topsoil (70% sand, 26% silt, 4% clay, pH 7.1–7.5) covered with the worm casts in the north of Thailand at middle to higher elevations (388–677 m amsl)
In Thailand, it occurs in various types of natural freshwater habitats of rivers, streams, canals, ponds and even in paddy areas
Summary
Species of the genus Glyphidrilus Horst, 1889 are unfamiliar earthworms living on an ecotone between terrestrial and freshwater ecosystems of rivers, streams, canals, ponds, swamps or even in paddy rice system. Later Michaelsen (1897) described G. stuhlmanni from Tanzania, and reported several more Asian species from India, Nepal, Ceylon, Burma, the Andaman Islands, Malay Peninsula, and Thailand (Michaelsen 1902, 1910, 1922, Stephenson 1916, 1924, 1930, Rao 1922, Gates 1945, 1958, Chen and Xu 1977, Zicsi 1996, Shen and Yeo 2005, Chanabun et al 2011, 2012a, b). Glyphidrilus biodiversity has probably been influenced by river system changes, given that these worms live in or near waterfalls, small streams, rivers, canals, swamps, and paddy systems (Figs 3, 4). The interconnections among these diverse microhabitats allow gene flow, but when connections are severed, independent evolution in isolation can lead to speciation. There are some endemic species within each drainage system, but there are some wider distributed species
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