Amynthas tertiadamae ( Michaelsen, 1934 )

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 : 890-892

Amynthas tertiadamae ( Michaelsen, 1934)

( Figure 6 )

Pheretima tertiadamae Michaelsen, 1934: 535 , figs XXIII–XXV.

Amynthas tertiadamae – Sims & Easton 1972: 235, 246.

Material examined

40 matures (CTU-EW 095.01) An Son Island (09°41 ʹ 11.1 ʹʹ N, 104°21 ʹ 10.8 ʹʹ E), Kien Hai District , Kien Giang Province, 17 November 2013, coll . Kim-Binh T. Trinh ; 39 matures (CTU-EW 095.02) same locality, but 13 October 2014 .

Diagnosis

Small size, length 68–92 mm, diameter 2.2–3.0 mm, 87–122 segments. Prostomium 1/2 epilobous. First dorsal pore in 12/13. Setal number 32–47 in viii, 43–53 in xxx, 6–10 between male porophores in xviii; setal distance aa> ab, zz> zy. Four pairs of spermathecal pores in lateroventral intersegments 5/6/7/8/9. Male pores located in xviii, without copulatory pouches. Genital marking absent in the spermathecal region, but two pairs in 17/18 and 18/ 19 in front of and behind the male pores, respectively. Testis sacs separated. Holandric. Intestinal caeca simple, xxvii–xxiv. Septa 8/9/10 absent.

Re-description

External characters. Body cylindrical, small size; length 68–92 mm, diameter 2.2– 3.0 mm, weight 0.29–0.54 g; 87–122 segments. Dorsum darkish brown, but ventrum paler.

Prostomium 1/2 epilobous (open) First dorsal pore in 12/13. Setae perichaetine, short; pre-clitellar setae stouter and sparser than post-clitellar setae, 32–47 in viii, 43–53 in xxx, 6–10 between male porophores in xviii; setal distance aa> ab, zz> zy. Clitellum annular, xiv–xvi, greyish brown, smooth and without setae and dorsal pores. Female pore single, mid-ventral in xiv.

Spermathecal pores four pairs, in lateroventral intersegments 5/6/7/8/9. Genital markings absent in the spermathecal region.

Male pores directly opened in xviii, without copulatory pouches; ventral distance between male porophores about 0.4× body circumference. Porophores slightly elevated from body wall. Two pairs of small, bean-shaped genital markings in front of and behind porophores 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, within xxvii–xxiv, enlarged basally. Last hearts in xiii. Pharyngeal micronephridia poorly developed in 5/6/ 7. Lymph glands from 16/17, small, lobuled. Typhlosole simple, lamelliform (segments 24–41).

Spemathecae paired in vi–ix. Spermathecal ampulla large, egg-shaped, whitish yellow; duct stout, about one-quarter ampulla length. Diverticula directly attached to base of ampulla duct, strongly coiled and folded, shorter than ampulla; distal part enlarged to be a seminal chamber. No accessory glands.

Holandric. Testis sacs separated in x, xi. Seminal vesicles well developed within xi–xii. Ovaries invisible; oviduct after septum 12/13. Prostate glands deeply lobuled, paired in xvi–xxi; prostatic ducts U-shaped, slightly bigger distally. Accessory glands invisible.

Habitats

All specimens were found in clay soils in natural forest and plantation.

Remarks

New material was collected in An Son Island , about 60 km southeastward from the type locality, Phu Quoc Island . New material totally agrees with Michaelsen (1934) ’s description.

The species is fairly close to Amynthas juliani ( Perrier 1875) by having first dorsal pore in 12/13, four pairs of spermathecal pores in intersegments 5/6/7/8/9, no copulatory pouches, simple intestinal caeca, deeply lobuled prostatic glands and genital markings in male region. However, A. juliani has larger size (260–389 mm in length) and more segments (126–260 segments), prolobous prostomium, three pairs of genital markings on setal rings of xvii, xix and xx, thickened septa 8/9, mushroom-shaped spermathecal ampulla, and diverticula being not coiled ( Perrier 1875).

Figures

Figure 6. Amynthas tertiadamae (Michaelsen, 1934). (a, e) Male region (mp = male pore, gm = genital markings); (b) ventral view of spermathecal region (sp = spermathecal pore); (c, f) intestinal caecum; (d, j) spermathecae (amp = ampulla, dv = diverticulum); (g, i) prostatic gland; (h) left male porophore, lateral view. Scale bar = 1 mm.