Glyphidrilus mekongensis Panha & Chanabun, 2012

Chanabun, Ratmanee, Bantaowong, Ueangfa, Sutcharit, Chirasak, Tongkerd, Piyoros, James, Samuel W. & Panha, Somsak, 2012, A New Species Of Semi-Aquatic Freshwater Earthworm Of The Genus Glyphidrilus Horst, 1889 From The Mekong River (Oligochaeta: Almidae), Raffles Bulletin of Zoology 60 (2), pp. 265-277 : 266-267

Glyphidrilus mekongensis Panha & Chanabun , new species

( Figs. 1 , 2 , 3A,D , 4 )

Material examined. — Holotype: One adult ( CUMZ 3215 ), Thailand, bank of Mekong River at Khong Chiam District , Ubon Ratchathani Province (15°18'57.1"N, 105°30'43.9"E), 101 m in elevation, coll. S. Panha, R. Chanabun, P. Tongkerd, C. Sutcharit & U. Bantaowong, 6 Nov.2010. 21 paratypes: 15 adults ( CUMZ 3216 ), 3 adults ( ZMH), 3 adults ( NHM), and 2 adults ( ZRC), same collection data as for holotype.

Diagnosis. — Glyphidrilus mekongensis , new species, medium to large sized semi-aquatic freshwater earthworm with distinct expanded tissues of clitellar wing organs on the lateral sides of the body in 24–34. Female pores, male pores and spermathecal pores not visible. Genital markings present in 23. Four pairs of seminal vesicles in 9–12, with the pair in segment 12 largest. Intestinal origin in 17. Ovaries in 13–14. Prostate and accessory glands and spermathecae absent.

Etymology. — This new species is named after the Mekong River, an international river. The locality is a part of this famous river and for this is the first time of this worm genus ever recorded from this river.

Description of holotype. — Dimensions: 132 mm body length by 2.9 mm at the anterior body region in segment 8 and 3.1 mm before the clitellar wings in segment 18, 3.6 mm after wings in segment 40 within the clitellum, body

cylindrical in the anterior part but quadrangular in transverse section view after clitellum, with 228 segments. The body is pale brown with variation from red to pink colouration at adjacent tissues of the so called wing portion in different individuals of newly collected specimens after placement in 30% ethanol for narcotization. Dorsal surface considerably broader than the ventral at the posterior end. The clitellar wings on ventro-lateral part of the clitellum in 24–34, 8.5 mm long, and about 0.6 mm wide on both sides. Prostomium zygolobous. Dorsal pores absent. Clitellum annular shape in 19–38. Four pairs of setae per segment from 2, setae formula aa:ab:bc:cd:dd = 2.9:1.0:1.8:1.9:2.3 in 8. Female pores, male pores, and spermathecal pores not visible. Genital markings: paired between b and c in 23.

Septa 5/6–8/9 thicker, 9/10–14/15 thick, and 15/16 to the last segment thin. Gizzard small, globular within 8. Intestine enlarged from 15. Dorsal blood vessel aborted anterior to 7. Hearts from 7–11. No nephridia distinguishable in the first 12 segments. Four pairs of seminal vesicles in 9–12, with the pair in segment 12 larger than the others. Ovaries in 13–14. Prostate and accessory glands and spermathecae absent.

Figures

Fig. 1. Map of Ubon Ratchathani Province showing type locality of Glyphidrilus mekongensis, new species (arrow head) located on the shore of the Mekong River at Khong Chiam District.

Fig. 2. Photographs showing: A, casts; B, cocoon (arrow head); C, habitat, of Glyphidrilus mekongensis, new species in a bay structure with rock front barrier at the Mekong River.

Fig. 3. The colouration of newly collected specimens just after the first step preservation in 30% ethanol:A, Glyphidrilus mekongensis, new species (paratype CUMZ 3216); B, Glyphidrilus malayanus from Tok Bok Hotspring, Kelantan, Malaysia (CUMZ 3218); C, Glyphidrilus singaporensis topotype specimen (CUMZ 3217); D, cocoon characters of Glyphidrilus mekongensis, new species (paratype CUMZ 3216).

Fig. 4. External and internal morphology of holotype (CUMZ 3215) of Glyphidrilus mekongensis, new species: A, external ventral view; B, internal dorsal view; C, newly hatched worm characters (paratype CUMZ 3216).