Metaphire peguana laisonensis Nguyen & Nguyen, 2017

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 : 900-902

Metaphire peguana laisonensis Nguyen & Nguyen subsp. nov.

( Figure 12 )

http://specieslsid:zoobank.org:act: B103AFC0-2035-4462-81EA-5F9CD9B222CD

Material examined

29 matures (CTU-EW 087.01) Lai Son Island (09°48 ʹ 10.5 ʹʹ N, 104°36 ʹ 51.3 ʹʹ E) Kien Hai District, Kien Giang Province, 15 November , leg . Kim-Binh T. Trinh.

Diagnosis

Body cylindrical, medium size, length 67–116 mm, diameter 3.5–4.5 mm, 70–115 segments. Prostomium 1/3 epilobous. First dorsal pore in 12/13. Setal number 30–41 in viii, 49–55 in xxx, 5–10 between male porophores in xviii; setal distance aa = 1.2–2.0 ab, zz = 1.2–2.0 zy. Three pairs of spermathecal pores, in lateral intersegments 6/7/8/9. Male pores located inside copulatory pouches in xviii. No genital markings in the spermathecal region, but two large, round pairs in xvii and xix, in line with male porophores. Testis sacs separated. Holandric. Intestinal caeca simple. Septa 8/9/10 absent.

Description

External characters. Body cylindrical, medium size; length 67–116 mm, diameter 3.5– 4.5 mm, segments 70–115, weight 0.54–1.48 g. Body uniformly light grey except clitellum brown. Setae perichaetine; pre-clitellar setae sparser than post-clitellar setae, 30–41 in viii, 49–55 in xxx, 5–10 between male porophores in xviii; setal distance aa = 1.2–2.0 ab, zz = 1.2–2.0 zy. Prostomium 1/3 epilobous (closed). First dorsal pore in 12/13. Clitellum annular, xiv–xvi, smooth and without setae and dorsal pores. Female pore single, mid-ventral in xiv.

Three pairs of spermathecal pores in lateral intersegments 6/7/8/9. Ventral distance between spermathecal pores about 0.5× body circumference. No genital markings in the spermathecal region.

Male pores ellipsoid-shaped, deeply located inside copulatory pouches in xviii; ventral distance between male porophores about 0.35× body circumference. Two pairs of genital markings behind and in front of setal rings of xvii and xix, respectively, in line with male pores.

Internal characters. Septa 5/6/7/8 thin, 8/9/10 absent, 10/11/12/13 thin. Oesophageal gizzard after viii. Intestinal origin at xv; caeca simple, within xxvii–xxiv, sometimes xxvii– xxii. Last hearts in xiii. Pharyngeal micronephridia developed in 5/6/7. Lymph glands lobuled, from 16/17. Typhlosole simple, lamelliform (segments 25–48).

Spermathecae paired in vii–ix. Spermathecal ampulla large, egg-shaped; duct short, about one-third ampulla length. Diverticula as short as duct, coiled and folded, directly attached to duct; distal part enlarged to be an opalescent seminal chamber. No accessory glands.

Holandric. Testis sacs developed in x, xi, separated. Seminal vesicles well developed in xi, xii. Ovaries well developed, opalescent in 12/13; oviduct after septum 12/13. Prostate glands deeply lobuled, paired in xvi–xx or xxi; prostatic ducts S-shaped, slightly smaller distally. Accessory glands paired in xvii and xix.

Habitat

It was found inside rocky hollows containing rich organic matter in the natural forests.

Remarks

The new subspecies agrees with the description of Metaphire peguana except for minor differences in locations of spermathecal pores and genital markings. Metaphire peguana peguana has spermathecal pores located ventrolaterally (ventral distance c.0.35× body circumference), genital markings paired in intersegments 17/18 and 18/19, diverticula duct attached to base of duct ( Figure 13 ). In contrast, the new subspecies shows spermathecal pores located laterally (ventral distance c.0.5× body circumference), genital markings paired in xvii and xix, diverticula attached to middle duct ( Figure 12 ). In addition, M. peguana laisonensis is slightly smaller and has fewer segments and setae than M. peguana peguana (length: 67–116 mm vs 115–154 mm; diameter: 3.5–4.5 mm vs 4.2–5.9 mm; segment number: 70–115 vs 112–125).

Sims and Easton (1972) listed the Metaphire peguana species group characterized by three pairs of spermathecal pores with the first pores at 6/7, and genital markings on 17/ 18 and 18/19. This group contains three species, M. peguana ( Rosa, 1890) , M. bahli ( Gates 1945) and M. saigonensis ( Omodeo 1957) . Thai (1983, 2000) and Nguyen et al. (2014) synomymized M. saigonensis with M. bahli because of similarity in the male region. Although Blakemore (2016) re-validated the species Metaphire saigonensis , we still think it is a junior synonym. The difference between M. saigonensis and M. bahli is very slight based on ventral distance between male pores (<0.2 versus 0.2). No more strong evidence supporting separation of these species is provided ( Table 1). However, it is unlikely to resolve this problem without type checking, and molecular data will be necessary to finally settle it.

Morphologically, members of the peguana species group are similar to each other; they share similar characters, e.g. spermathecal pores in 6/7/8/9, two pairs of genital markings in xvii and xix, or 17/18 and 18/19, morphology of male region and spermathecal region. However, they are distinguished from each other by ventral distance between spermathecal pores, between male pores, shape of genital markings in male region, and origin of spermathecal diverticula ducts ( Table 1). Besides morphological data, molecular data, for example, mitochondrial genes (cytochrome c oxidase subunit I or 16S rRNA) should be used to analyse the relationship of the peguana species group.

Figures

Figure 12. Metaphire peguana laisonensis subsp. nov. (a, f) Male region (mp = male pore, gm = genital markings); (b,e) lateral view of spermathecal region (sp = spermathecal pore); (c, i) prostatic gland (ag = accessory gland); (d, h) spermathecae (amp = ampulla, dv = diverticulum); (g, j) intestinal caeca. Scale bar = 1 mm.

Figure 13. Metaphire peguana (Rosa, 1890) from Dong Nai Province, Vietnam. (a, f) Male region (mp = male pore, gm = genital markings); (b) ventral view of spermathecal region (sp = spermathecal pore); (c, h) intestinal caecum; (d, i) spermathecae (amp = ampulla, dv = diverticulummm); (e, j) prostatic gland (ag = accessory gland); (g) male porophores and accessory glands, transverse body section. Scale bar = 1 mm.