Polypheretima dorsotheca 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 : 908-913

Polypheretima dorsotheca Nguyen & Nguyen sp. nov.

( Figure 16 )

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Material examined

Holotype. 1 mature (CTU-EW 100.h01) Lai Son Island (9°47 ʹ 55.2 ʹʹ N, 104°37 ʹ 24.8 ʹʹ E), Kien Hai District , Kien Giang Province, 15 November 2013, coll. Kim-Binh T. Trinh . Paratypes: 15 matures (CTU-EW 100.p02) sampled together with holotype.

Non-types. 20 matures, 14 juveniles (CTU-EW 100.03) same data as holotype .

Diagnosis

Body cylindrical, small size, length 60–138 mm, diameter 3.0– 4.3 mm, segments 97–202. Prostomium 1/3 epilobous. First dorsal pore in 12/13. Setal number 36–50 in viii, 53–70 in xxx, 11–20 between male porophores in xviii; setal distance aa = 1.0–2.0 ab, zz = 1.0–2.0 zy. Spermathecal pores multiple in dorsal intersegments 4/5/6/7. Male pores located inside copulatory pouches in xviii. No genital markings in the spermathecal region, but two pairs in front of setal rings of xvii and xix, in line with male porophores. Testis sacs separated. Holandric. Intestinal caeca absent. Septa 8/9/10 absent.

Etymology

‘ dorsotheca ’ a noun in apposition to emphasize the spermathecal pores in dorsum.

Description

External characters. Body cylindrical, small size; length 60–138 mm, diameter 3.0– 4.3 mm, segments 97–202, weight 0.41–1.39 g. Dorsum grey while ventrum paler; clitellum brown. Setae perichaetine; pre-clitellar setae sparser than post-clitellar setae, 36–50 in viii, 53–70 in xxx, 11–20 between male porophores in xviii; setal distance aa = 1.0–2.0 ab, zz = 1.0–2.0 zy. Prostomium 1/3 epilobous (open). First dorsal pore in 12/13. Clitellum annular, xiv–xvi, smooth and with setae and dorsal pores. Female pore single, mid-ventral in xiv.

Multiple spermathecal pores in dorsal intersegments 4/5/6/7. No genital markings in the spermathecal region.

Male pores large, round, located inside copulatory pouches in xviii; ventral distance between male porophores about 0.35× body circumference. Two pairs of smooth, largely round genital markings on setal rings of xvii and xix, in line with male pores.

Internal characters. Septa 5/6/7/8 thickened, 8/9/10 absent, 10/11/12 thin. Oesophageal gizzard after viii. Intestinal origin at xv; caeca absent. Last hearts in xiii.

nov., and Polypheretima mekongmontis .

Pharyngeal micronephridia developed in 5/6/7. Lymph glands from 15/16. Typhlosole simple, lamelliform (segments 23–51).

Spemathecae variable, about 14–30 altogether in v–vii: 2–9 in v, 7–13 in vi, and 3–10 in vii ( Table 3). Spermathecal ampulla oval-shaped; duct very large, almost same size as ampulla. Diverticula cylindrical, as short as duct, attached to base of duct; distal part enlarged to be an opalescent seminal chamber. No accessory glands.

Holandric. Testis sacs in x–xi, separated. Seminal vesicles well developed in xi–xii. Ovaries invisible; oviduct after septum 12/13. Prostate glands deeply lobuled, paired in xvii–xxi; prostatic ducts C-shaped, slightly smaller distally. Two pairs of accessory glands in xvii and xix.

Remarks

The new species is closely similar to its congener, P. mekongmontis Nguyen, Tran & Nguyen, 2014 from An Giang Province. Both species have the same morphology of male region, two pairs of genital markings on xvii and xix, multiple spermathecae, first dorsal pore in 12/13. However, P. mekongmontis has spermathecal pores on the ventrolateral side, fewer spermathecae (16–19), duct long, about two-thirds length of ampulla, diverticula attached to middle ducts, last hearts in xii, lymph glands absent. In contrast, P. dorsotheca sp. nov. is characterized by having spermathecal pores on the dorsum, more spermathecae (14–30), shorter duct (about one-third length of ampulla), diverticula attached to base of ducts, last hearts in xiii, lymph glands from 15/16.

The new species is also fairly close to P. insularis sp. nov. from Hon Tre Island by having three thecal segments in v–vii, epilobous prostomium, and no genital markings in the spermathecal region. However, P. dorsotheca sp. nov. differs from P. insularis sp. nov. in a location of spermathecal pores (dorsal versus dorsolateral), and the number of genital markings in the male region (two pairs in xvii and xix versus a pair in xix).

A detailed comparison between the two species is provided in Table 4.

Key to earthworm species recorded in Hon Tre, Lai Son and An Son islands, southern Vietnam

(1) Setae eight per segment; setae quincuaxial in posterior segments. Clitellum saddle-shaped, xiv–xxii ..................................................................... Pontoscolex corethrurus Perichaetine. Clitellum annular, xiv–xvi. Female pore in xiv; male pores in xviii or xix............................................................................................................................................................ 2

(2) Instestine without caeca ............................................................................................................... 3 Instestine with caeca ...................................................................................................................... 5

(3) Prostomium prolobous. Spermathecal pores ventrolaterally. Two pairs of genital markings in xvii and xix........................................................ Polypheretima mekongmontis Prostomium epilobous. Spermathecal pores not ventrolaterally. One or two pairs of genital markings in male region.......................................................................................... 4

(4) Spermathecal pores dorsolaterally. A pair of genital markings in xix............................ ..................................................................................................... Polypheretima insularis sp. nov. Spermathecal pores dorsally. Two pairs of genital markings in xvii and xix.............. ................................................................................................ Polypheretima dorsotheca sp. nov.

(5) Copulatory pouches absent......................................................................................................... 6 Copulatory pouches present ....................................................................................................... 8

(6) Three pairs of spermathecal pores in 5/6/7/8.......................... Amynthas alteradamae Four pairs of spermathecal pores in 5/6/7/8/9 ................................................................... 7

(7) Many genital markings in both spermathecal and male regions.................................... ................................................................................................................ Amynthas exiguus exiguus No genital markings in spermathecal region, but two pairs in xviii............................... ....................................................................................................................... Amynthas tertiadamae

(8) Male pore in xix. Four pairs of spermathecal pores.......... .......... Metaphire anomala Male pore in xviii. Fewer than four pairs of spermathecal pores ............................... 9

(9) More than one pair of spermathecae per segment.......... Metaphire kiengiangensis One pair of spermathecae per segment.............................................................................. 10

(10) Two pairs of spermathecal pores in 5/6/7. Intestinal caeca manicate........................... ....................................................................................................................... Metaphire mangophila Three pairs of spermathecal pores in 6/7/8/9. Intestinal caeca simple.................. 11

(11) No genital markings in the male region....................... ....................... Metaphire houlleti Two pairs of genital markings in the male region.......................................................... 12

(12) Male region strongly concave. Genital markings in 17/18 and 18/19........................... ..................................................................................................................................... Metaphire bahli Male region not concave. Genital markings in xvii and xix................................................ .............................................................................. Metaphire peguana laisonensis subsp. nov.

Figures

Figure 16. Polypheretima dorsotheca sp. nov. Holotype. (a, e) Male region (mp = male pore, gm = genital markings); (b, c) spermathecae (amp = ampulla, dv = diverticulum); (d, f) prostatic gland (ag = accessory gland); (g) ventral view of spermathecal region (sp = spermathecal pore). Scale bar = 1 mm.