Polypheretima medialis Lam, Nguyen & Nguyen, 2018

Lam, Dang H., Nguyen, Tung T., Hoang, Sam V. & Nguyen, Anh D., 2018, Two new earthworm species of the genus Polypheretima Michaelsen, 1934 (Clitellata: Megascolecidae) from central Vietnam, Raffles Bulletin of Zoology 66, pp. 572-579 : 573-575

Polypheretima medialis Lam, Nguyen & Nguyen , new species

( Fig. 2 )

Type material. Holotype: 1 mature specimen (CTU-EW.184. h01), regenerated forest (15°18′27.8″N, 107°44′12.2″E), Phuoc My Commune, Phuoc Son District , Quang Nam Province, 10/3/2017, coll. Lam Hai Dang.

Paratypes: 6 mature specimens (CTU-EW.184.p02) same data as for holotype; 5 mature specimens (CTU-EW.184. p03) regenerated forests (15°38′08″N, 107°40′13.5″E), Ta Bhing Commune, Nam Giang District , Quang Nam Province, 23/3/2017, all coll. Lam Hai Dang.

Other material. 2 mature specimens (CTU-EW.184.04), natural forests (15°19′15.6″N, 107°43′43.9″E), Phuoc My Commune, Phuoc Son District , Quang Nam Province, 10/3/2017 ; 3 mature specimens (CTU-EW.184.05), grasslands (15°22′24.6″N, 107°45′8.5″E), Phuoc My Commune, Phuoc Son District , Quang Nam Province, 05/3/2017 ; 3 mature specimens (CTU-EW.184.06), plantations (15°20′41.9″N, 107°44′25.5″E), Phuoc My Commune, Phuoc Son District , Quang Nam Province, 05/3/2017 ; 2 mature specimens (CTU- EW.184.07), natural forests (15°38′01.2″N, 107°43′42.1″E), Ta Bhing Commune, Nam Giang District , Quang Nam Province, 13/3/2017 , all coll. Lam Hai Dang.

Diagnosis. Medium sized worm, length 92–97 mm, diameter 4.8–5.1 mm, 129–145 segments. Prostomium epilobous. First dorsal pore in 12/13. Setal number: 65–73 in viii, 92–96 in xxx, 14–18 between male porophores in xviii. Spermathecal pores ventrally paired in intersegmental furrows 7/8/9. Genital markings mid-ventrally paired in presetal viii–ix and xvii–xix. Holandric. Intestinal caeca absent. Copulatory pouches absent.

Description. External characters: Body cylindrical, medium size; length 92–97 mm, diameter 4.8–5.1 mm, weight 1.67– 1.71 g, 129–145 segments. Body uniformly whitish grey. Prostomium epilobous (open). First dorsal pore in 12/13. Setae perichaetine, short; pre-clitellar setae stouter and sparser than post-clitellar setae; setal number: 65–73 in viii, 92–96 in xxx, 14–18 between male porophores in xviii. Clitellum annular, xiv–xvi, dark brown, smooth, without dorsal pores and setae. Female pore single, mid-ventral in xiv.

Spermathecal pores ventrally paired in intersegmental furrows 7/8/9. Two pairs of presetal genital markings in mid-ventral viii–ix. Male pores simple on conical porophores in xviii, without copulatory pouches; ventral distance between male porophores about 0.3× body circumference. Three pairs of round presetal genital markings in mid-ventral xvii–xix.

Internal characters. Septa 5/6/7/8 thickened, 8/9/10 absent, 10/11/12/13 thin. Oesophageal gizzard in viii–x. Intestinal origin at xv; caeca absent. Last hearts in xiii. Pharyngeal micronephridia developed in anterior faces of 5/6/7. Lymph glands absent. Typhlosole simple, lamelliform.

Two pairs of spermathecae in viii and ix. Spermathecal ampulla small, heart-shaped; duct about half of ampulla length. Diverticulum much shorter than ampulla, directly attached to the base of the spermathecal duct, distal part enlarged to form a transparent oval-shaped seminal chamber. Accessory glands invisible.

Holandric. Testis sacs separated in x and xi, ventrally. Seminal vesicles well developed, paired in xi–xii. Ovaries in xiii; oviduct invisible. Prostate glands poorly lobuled, paired in xvii–xix; prostatic ducts long, spiral, enlarged at distal end. Accessory glands invisible.

Etymology. The epithet “ medialis ” is an adjective to emphasise the location of genital markings.

Habitats. The new species was commonly found in natural forests (10–30 cm soil depth), regenerated forests (0–30 cm soil depth), grasslands (0–30 cm soil depth) and plantations (20–30 cm soil depth) in both Ta Bing and Phuoc My communes.

Remarks. The new species belongs to the bifaria -species group characterised by holandry and having simple male pores without copulatory pouches and spermathecal pores in intersegmental furrows ( Easton, 1979).

Regarding the arrangement of genital markings in the male region, the new species is similar to P. taprobanae ( Beddard, 1892) and P. kyhaensis ( Thai, 1996) found in Vietnam in having simple male pores and genital markings paired in both spermathecal and male regions and being holandric. However, the new species has two pairs of spermathecal pores in 7/8/9 while P. kyhaensis has four pairs in 5/6/7/8/9 and P. taprobanae has only one pair in 7/8. The new species also differs from P. kyhaensis in pre-clitellar setae being sparser than post-clitellar (65–73 in viii, 92–96 in xxx), genital markings mid-ventrally paired in xvii–xix, testes sacs separated, last heart in xiii, and last micronephridia in anterior face of 6/7. In contrast, P. kyhaensis has pre-clitellar setae being much crowded than post-clitellar (126 in viii, 62 in xxv), seven pairs of genital markings in xvii–xxi (one pair for each segment xvii, xx, xxi, and 4 pairs in xviii) ( Fig. 4 ), testes sacs connected, last hearts in xii, and last micronephridia in anterior face of 7/8. P. medialis , new species is also different from P. taprobanae in having genital markings mid-ventrally paired in xvii–xix and last hearts in xiii while P. taprobanae has genital markings paired in line with male porophores and last hearts in xii.

The new species is also somewhat similar to the bithecate P. annamensis ( Stephenson, 1931) and P. parataprobanae (Thai & Nguyen, 1993 in Nguyen, 1993) found in Vietnam in holandry and having first dorsal pore in 12/13. Nevertheless, P. medialis , new species has two pairs of spermathecal pores in 7/8/9 and genital markings in the male region while the other two species have only one pair of spermathecal pores which are in 6/7 for P. annamensis and in 7/8 for P. parataprobanae and no genital markings in the male region. The new species is also distinguished from P. annamensis in genital markings being present in the sper mathecal region (vs. absent) and absence of copulatory pouches (vs. presence). P. medialis , new species also differs from P. parataprobanae by having epilobous prostomium (vs. prolobous), separated testes sacs (vs. connected) and intestinal origin at xv (vs. at xvi).

The new species is also similar to P. sempolensis Easton, 1979 , P. pagudpudensis Hong & James, 2011 , and P. renschi ( Ude, 1932) in holandry and having two pairs of spermathecae and intestinal origin at xv. However, the new species has spermathecal pores paired in 7/8/9 whereas both P. sempolensis and P. pagudpudensis have paired spermathecal pores in 5/6/7. In addition, the new species has genital markings in xviii (absent in the other species), last hearts in xiii (in xii in both P. sempolensis and P. pagudpudensis but unknown in P. renschi ). Specifically, the new species is distinguished from P. sempolensis by having first dorsal pore in 12/13 (vs. 13/14) and no pseudovesicles (vs. presence in xiv). It is also differentiated from P. pagudpudensis in having genital markings mid-ventrally paired in viii–ix (vs. no genital markings), pre-clitellar setae (65–73 in viii) sparser than post-clitellar setae (92–96 in xxx) (vs. preciltellar setae (63 in vii) more crowded than post-clitellar setae (27 in xx), distance between male pores about 0.3× body circumference (vs. 0.23×), and separated testes sacs (vs. testes sacs connected). The species, P. renschi , is distinguished from P. medialis , new species, by having no genital markings and presence of copulatory pouches.

Figures

Fig. 2. Polypheretima medialis, new species, holotype. A1, A2, ventral view of male pores region; B, ventral view of spermathecal region; C1, C2, prostatic gland; D1, D2, spermathecae; E, male pore cross section slide; F, genital markings cross section slide. Scale bar: 1 mm.

Fig. 4. Polypheretima kyhaensis (Thai, 1996) redrawn following the original description (Thai, 1996). A, ventral view of male pore region; B, lateral view of spermathecal region; C, spermathecae; D, testis sacs (ts), seminal vesicles (sv), and ovaries (ov). Scale bar: 1 mm.