Glyphidrilus bisegmentus Chanabun & Panha, 2012

Chanabun, Ratmanee, Sutcharit, Chirasak, Tongkerd, Piyoros, Tan, Shau-Hwai Aileen & Panha, Somsak, 2012, Three new species of semi-aquatic freshwater earthworms of the genus Glyphidrilus Horst, 1889 from Malaysia (Clitellata: Oligochaeta: Almidae), Zootaxa 3458, pp. 120-132 : 121-124

Glyphidrilus bisegmentus Chanabun & Panha , sp. n.

( Figs 1, 2A, 3, Table 1)

Type material. Holotype: One clitellate ( CUMZ 3276 ) ( Fig. 3), Air Banun Pandig, Perak, Malaysia, 496 meters in elevation, S. Panha, R. Chanabun, P. Tongkerd and C. Sutcharit leg., 27 May 2011. 17 clitellates and 8 aclitellates as paratypes ( CUMZ 3277 ), 3 clitellates ( ZMH OL14575 ), 3 clitellates (NHM), same collection data as for holotype.

Other material. 22 clitellates and 4 aclitellates ( CUMZ 3278 ), muddy swamp near Kratu waterfall, Kratu, Phuket, Thailand, 07°55'55.5''N, 098°19'23.3"E., 11 m asl, 11 December 2009 .

Type locality. River banks of Air Banun Pandig, Perak, Malaysia, 05°38'13.4''N, 101°42'41.1"E, 496 m asl .

Etymology. This new species was named after the character of having wings only on two segments at 18–19.

Diagnosis. Small sized limicolous earthworm with distinct expanded tissues of clitellar wing organs on the lateral sides of the body in 18–19. Clitellum in 16, 17–23, 24. Female pores, male pores and spermathecal pores not visible. Genital markings absent. Four pairs of seminal vesicles in 9–12, with the pair in segment 12 largest. Intestinal origin in 15. Ovaries in 13–14. Prostates, accessory glands, and spermathecae absent.

Description of holotype. Dimensions: body length 71 mm, diameter 2.3 mm in segment 8, 2.4 mm before clitellar wings in segment 17, 2.0 mm after wings in segment 20 within the clitellum; body cylindrical in anterior part, quadrangular in transverse section behind clitellum. 217 segments. Body colour pale brown with variations from red to pink at adjacent tissues of wing portion in different individuals of newly collected specimens after placement in 30% ethanol for narcotization. At posterior end dorsal surface considerably broader than ventral. Stout wings like lateral ridges in bc extending through segments 18–19 in clitellar region. Prostomium zygolobous. Dorsal pores absent. Clitellum annular in 17–24. Four pairs of setae per segment from 2, setal formula aa:ab:bc:cd:dd = 1.0:0.5:1.1:0.5:1.2 in segment 8. Female pores, male pores and spermathecal pores not visible. Genital markings absent.

Septa 4/5–7/8 thicker, 8/9–11/12 thick, from 12/13 to last segment thin. Gizzard small, globular within 8–9. Intestine enlarged from 15. Dorsal blood vessel anterior to 9. Hearts from 9–11. No nephridia distinguishable in first 14 segments. Four pairs of seminal vesicles in 9–12, pair in segment 12 larger than the others but pair in segments 10 and 11 very small. Ovaries in 13–14. Prostate and accessory glands, and spermathecae absent.

Variation. Body length 40–71 mm (57.06±20.50), with 152–252 segments. Wings always in 18–19 (covering 2 segments), clitellum in 16, 17–23, 24 (covering 6–9 segments). Genital markings always absent.

Habitat. Found on the shore but in proximity to the river water, in the sandy loam topsoil with 65% sand, 35% silt, with pH 7.2, and also under the water at about 5–10 cm in depth. The bank of river was covered with worm casts at Air Banun Pandig, Perak, Malaysia and at Kratu Waterfall, Kratu, Phuket, Thailand.

Distribution. The new species is known from the type locality, Air Banun Pandig, Perak, Malaysia and from a muddy swamp near Kratu waterfall, Kratu, Phuket, Thailand.

Remarks. This athecal species is quite distinct from others of the genus, which typically have several spermathecae per segment in several segments and wings on more than two segments. Among the species bearing spermathecae, G. malayanus from the Malay Peninsula is most similar to G. bisegmentus sp. n. in the location of the clitellum. However, the other characters are specifically different. Glyphidrilus malayanus has longer wings in 17, ¾18, 18–⅓21, ⅓22, 22 and spermathecae in 14/15–16/17. Glyphidrilus bisegmentus sp. n. differs from the Laotian athecal G. vangviengensis by the following characteristics: G. vangviengensis has longer wings in 24, 25–31, 32, and longer clitellum in 19, 20–35, 36, 37 ( Table 1).

Material of other species examined for comparison. Glyphidrilus malayanus Michaelsen, 1902: 35 : one clitellate (syntype ZMH V5875 ); type locality: Malay Peninsula , Lubock Paku, Pahang River. Glyphidrilus vangviengensis Panha & Chanabun, 2011: 216 , Figs. 1–3; one clitellate (holotype CUMZ 3221 ) and 10 clitellates (paratypes CUMZ 3222 ) ; type locality: river banks of Song River at Vangvieng, Veintiane Province, Laos .