Pontoscolex corethrurus ( Müller, 1856 )

Nguyen, Tung T., Trinh, Kim-Binh T., Nguyen, Hong-Lan T. & Nguyen, Anh D., 2017, Earthworms (Annelida: Oligochaeta) from islands of Kien Hai District, Kien Giang Province, Vietnam, with descriptions of two new species and one subspecies, Journal of Natural History 51 (15 - 16), pp. 883-915 : 885-888

Pontoscolex corethrurus ( Müller, 1856)

( Figure 2 )

Material examined

43 matures (CTU-EW 001.08) Hon Tre Island (09°58 ʹ 13.0 ʹʹ N, 104°51 ʹ 15.5 ʹʹ E;), Kien Hai District , Kien Giang Province, 13 November 2013, coll . Kim-Binh T . Trinh; 21 matures (CTU-EW 001.09) Lai Son Island (09°48 ʹ 48.5 ʹʹ N, 104°37 ʹ 32.4 ʹʹ E), Kien Hai District , Kien Giang Province, 15 November 2013, coll . Kim-Binh T . Trinh; 10 matures (CTU-EW 001.10)

An Son Island (09°41 ʹ 2.6 ʹʹ N, 104°21 ʹ 18.3 ʹʹ E), Kien Hai District , Kien Giang Province, 16 November 2013, coll . Kim-Binh T. Trinh.

Habitats

The species is commonly found in plantations, fruit gardens and natural forests in the study areas.

Remarks

The species is widely distributed in Vietnam ( Nguyen et al. 2016).

Family MEGASCOLECIDAE Rosa, 1891

Genus Amynthas Kinberg, 1867

Amynthas alteradamae ( Michaelsen 1934)

( Figures 3 and 4 )

Pheretima alteradamae Michaelsen, 1934: 540 , figs. XXVII–XXVIII.

Amynthas alteradamae – Sims & Easton 1972: 237.

Material examined

22 matures (CTU-EW 093.01) Hon Tre Island (09°58 ʹ 11 ʹʹ N, 104°50 ʹ 9.4 ʹʹ E), 82 m, Kien Hai District , Kien Giang Province, 12 November 2013, coll . Kim-Binh T . Trinh; 31 matures (CTU-EW 093.02) An Son Island (09°41 ʹ 11.8 ʹʹ N, 104°21 ʹ 10.1 ʹʹ E), Kien Hai District , Kien Giang Province, 17 November 2013, coll . Kim-Binh T . Trinh.

Diagnosis

Small size, length 38–58 mm, diameter 1.9–2.7 mm, 109–140 segments. Prostomium 1/2 epilobous. First dorsal pore in 12/13. Setal number 33–44 in viii, 42–54 in xxx, no setae between male porophores in xviii; setal distance aa = 1.7–2.0 ab, zz = 1.6–2.0 zy. Three pairs of spermathecal pores in lateroventral intersegments 5/6/7/8. Male pores located in xviii, without copulatory pouches. Genital markings absent in the spermathecal region, but one to three pairs around the male pores. Testis sacs separated. Holandric. Intestinal caeca simple, short, xxvii–xxv. Septa 8/9/10 absent.

Redescription

External characters. Body cylindrical, small size; length 38–58 mm, diameter 1.9– 2.7 mm, weight 0.1–0.25 g, 109–140 segments. Body uniformly whitish grey.

Prostomium 1/2 epilobous (open). First dorsal pore clearly distinct in 12/13. Setae perichaetine, short; pre-clitellar setae stouter and sparser than post-clitellar setae, 33–44 in viii, 42–54 in xxx, no setae between male porophores in xviii; setal distance aa = 1.7– 2.0 ab, zz = 1.6–2.0 zy. Clitellum annular, xiv–xvi, light brown, smooth, without dorsal pores, but with ventral setae. Female pore single, mid-ventral in xiv.

Spermathecal pores lateroventrally paired in intersegments 5/6/7/8. Genital markings absent in the spermathecal region.

Male pores directly opened in xviii, without copulatory pouches; ventral distance between male porophores about 0.3× body circumference. One to three pairs of genital markings around the male pores, and additionally one pair mid-ventral in xviii.

Internal characters. Septa 5/6/7/8 thickened, 8/9/10 absent, 10/11/12/13 thin. Oesophageal gizzard after viii. Intestinal origin at xv; caeca simple, short, within xxvii– xxv. Last hearts in xiii. Pharyngeal micronephridia developed in 5/6/7. Lymph glands from 22/23. Typhlosole simple, lamelliform (segments 27–45).

Spemathecae paired in vi–viii. Spermathecal ampulla large, oval-shaped, whitish yellow; duct about one-third ampulla length. Diverticula directly attached to base of ampulla duct; distal part enlarged to be opalescent seminal chamber. No accessory glands.

Holandric. Testis sacs separated in x, xi. Seminal vesicles whitish yellow, lobuled, well developed with two pairs in xi–xii. Ovaries invisible; oviduct on septum 12/13 posteriorly. Prostate glands deeply lobuled, paired in xvi–xxi; prostatic ducts short, cylindrical and straight. Two to three pairs of accessory glands clearly distinct, slightly elevated from body wall in xviii.

Habitats

The species was found in soils for long-term and short-term growth of trees.

Remarks

The species was only found in Phu Quoc Island ( Michaelsen 1934), and no other records have been reported since its description.

New material was found in two islands, Hon Tre and An Son, which are very close to the type locality, Phu Quoc Island . However, new material slightly differs from the original description in having a single female pore in midventral xiv, last hearts in xiii and an additional pair of genital markings in mid-ventral xviii. In contrast, the original description has two female pores in mid-ventral xiv, last hearts in xii, and no genital markings between the male pores.

The number of genital markings around the male pores is variable from two pairs (6 of 53 examined specimens) up to three pairs (27 of 53 specimens) or down to one pair (14 of 53 specimens). Several specimens lost a genital marking near the right male pore ( Figure 4 ).

Figures

Figure 2. Pontoscolex corethrurus (Müller, 1856) from Lai Son Island. (a, b) Clitellum; (c) living adult. Scale bar = 1 mm.

Figure 3. Amynthas alteradamae (Michaelsen 1934) from Hon Tre Island. (a,f) Male region (mp = male pore, gm = genital markings); (b) ventral view of spermathecal region (sp = spermathecal pore); (c, h) prostatic gland (ag = accessory gland); (d, g) spermathecae (amp = ampulla, dv = diverticulum); (e) intestinal caecum. Scale bar = 1 mm.

Figure 4. Variation of genital markings in the male region of Amynthas alteradamae (Michaelsen 1934).