Amynthas demptus Qiu & Jiang, 2019

Yuan, Zhu, Dong, Yan, Jiang, Jibao, Zhao, Qi & Qiu, Jiangping, 2019, Three new species of earthworms (Oligochaeta: Megascolecidae) from Yunnan Province, China, Zootaxa 4664 (3), pp. 390-400 : 392-395

Amynthas demptus Qiu & Jiang , sp. nov.

( Figure 1 )

Type material. Holotype. Clitellate specimen ( YN 201104 -03 A): China, Yunnan, Xishuangbanna Nature Reserve (22.16694° N, 100.87389° E), 694 m asl, red soil in tropical rain forest, 20 July 2011, J.B. Jiang, J. Sun, X.D. Lei and H.W. Feng . Paratypes. Four clitellate specimens ( YN201606-02 ): China, Yunnan, Pu’er, Peacock mountain forest park (24.42250° N, 100.87806° E), 1180 m asl, yellow soil at riverside, 11 June 2016, X. Gao, Y.F. Lu, J.Z. Jiang ; one clitellate specimen and one sub-adult specimen ( YN201734-07 ): China, Yunnan, Baoshan, Gaoligongshan Nature Reserve (25.71745° N, 98.84683° E), 1153 m asl, 10 August 2017, J.B. Jiang, Y. Dong, Q. Zhao, Z. Yuan ; four clitellate specimens ( YN201738-03 ): China, Yunnan, Ruili, Tongbiguan Nature Reserve (24.10335°N, 98.00866°E), 830 m asl, 11 August 2017, J.B. Jiang, Y. Dong, Q. Zhao, Z. Yuan .

NCBI accession numbers of some of the type specimens are listed in Table 2 .

Etymology. The Latin "demptus" means "removed". The species is named after its characteristic of not having male pores.

Diagnosis. Dimensions 90–130 mm by 4.7–5.6 mm at clitellum, segments 89–138. Setae numbering 33–54 at III, 68–85 at V, 82–98 at VIII, 90–111 at XX, 75–90 at XXV; 7–10 between spermathecal pores in VI; 7–11 between spermathecal pores in VII; Spermathecal pores three pairs in 5/6–7/8, about 1/6 body circumference ventrally apart. For holotype no male pores and papillae; for other material examined, no male pores for all specimens, no papilla for six specimens, five pairs papillae in XVII–XXI for three specimens, seven pairs papillae in XV–XXII for one sub-adult specimen. Spermathecae three pairs in VI–VIII. Ampulla thin, heart-shaped, diverticulum twisted, uniformly thick, the length about 1.2 times longer than that of ampulla.

External characters. Brown purple on dorsum, no pigment on ventrum. Dimensions 90–130 mm by 4.7–5.6 mm at clitellum, segments 89–138. Prostomium 1/2 epilobous. First dorsal pore in 11/12. Clitellum in XIV–XVI, smooth, setae absent, dorsal pores absent. Setae numbering 33–54 at III, 68–85 at V, 82–98 at VIII, 90–111 at XX, 75–90 at XXV; 7–10 between spermathecal pores in VI; 7–11 between spermathecal pores in VII; setal formula: AA = AB, ZZ = 2.0–2.2 ZY. Spermathecal pores three pairs in 5/6–7/8, ventral, about 1/6 circumference ventrally apart from each other, eye-shaped. For holotype no male pores and papillae; for other material examined, no male pores for all specimens, no papillae for six specimens, five pairs papillae in XVII–XXI for three specimens ( Fig. 1E ), eight pairs papillae in XV–XXII for one sub-adult specimen ( Fig. 1 G ). Female pore single, mid-ventral in XIV.

Internal characters. Septa 5/6–6/7 thick and muscular, 7/8 and 10/11–13/14 slightly thick, 8/9–9/10 absent. Gizzard in VIII–X, ball-like. Intestine enlarged from XV. Intestinal caeca paired in XXVII, extending anteriorly to XXV, transitional between simple and complex, smooth ventral and dorsal edges with 3–4 finger-shaped follicles. Hearts four pairs in X–XIII, the first pair long and thin, the others larger.

Testis sacs two pairs in X–XI, oval, developed, separated from each other. Seminal vesicles two pairs in XI– XII, first pair developed, second pair medium. Prostate glands and prostatic ducts vestigial or absent in the eleven dissected specimens: in seven specimens, prostate glands and prostatic ducts absent; in three specimens, prostate glands vestigial, small, occupying 3 segments in 1/5XVIII–2/3XX and with tiny, S-shaped prostatic ducts, accessory glands white, stalked, only in XVII–XIX ( Fig. 1E ); in one sub-adult specimen, prostate glands small, racemose, occupying 4 segments in 1/3XVII–1/3XX and with S-shaped prostatic ducts, accessory glands white, stalked, only in XV–XIV and XIX–XXII ( Fig. 1H ).

Spermathecae three pairs in VI, VII, VIII, each about 4.2 mm long. Ampulla thin, heart-shaped, about 3.0 mm long. Diverticulum uniformly thick, its total length about 1.2 times longer than that of ampulla, terminal 2/3 twisted, terminal portion of diverticulum not iridescent.

Remarks. Since male pores are absent in this species it remains undecided whether it belongs in Amynthas or in Metaphire , two genera that are distinguishable only by differences in the male pore structure ( Sims & Easton 1972; Zhang et al. 2016). Here the species is provisionally placed in Amynthas . A. demptus keys to Amynthas hawayanus - group in Sims and Easton (1972) with three pairs of spermathecal pores in 5/6–7/8, and it is easily separated from the other species of the hawayanus -group by lacking male pores.

Absence of male pores and associated structures should be understood as parthenogenetic degeneration. The degree of degeneration is often variable among specimens within a species and includes differences in number a position of spermathecae ( Gates 1972; Reynolds 1974). In the type series of A. demptus , the respective characters are also variable: male pores are absent and prostate glands and prostatic ducts vestigial or absent. However, spermathecae are stable and present in the same number and position in all specimens.

According to Gates (1972), Metaphire anomala (Michaelsen, 1907) is also found in Yunnan, China. This species has also three pairs of spermathecal pores in 5/6–7/8, and its size and segment and setal numbers are fairly similar to those of A. demptus . Furthermore, M. anomala is highly variable due to parthenogenetic degeneration, and often specimens without spermathecae or without male pores are dominant ( Gates 1925, 1972). M. anomala differs from A. demptus in that the spermathecal pores, when present, are about 1/4 body circumference ventrally apart ( Gates 1925), whereas they are about 1/6 body circumference ventrally apart in A. demptus . Further differences are as follows: 1st dorsal pore is in 12/13 (11/ 12 in A. demptus ); reddish dorsal pigment, deeper anterior to the clitellum, and with a marked greenish or purple iridescence (brown purple dorsal pigment in A. demptus ); setal formula of M. anomala : ZZ is often slightly smaller than ZY ( ZZ = 2.0–2.2 ZY in A. demptus ) ( Gates 1972).

Parthenogenetic degeneration of reproductive organs is also found in Amynthas catenus Tsai et al., 2001 , Amynthas hohuanmontis Tsai et al., 2002 , Amynthas shinanmontis Tsai & Shen, 2007 , and in Amynthas proasacceus Tsai et al., 2001 from Taiwan, China ( Tsai et al. 2001, 2002, 2007). A. demptus is easily distinguished from these three species by the characters of the spermathecae, setal number, body size, intestinal caeca, male pores and genital papillae ( Table 3 ). A. demptus has three pairs of normal and stable number spermathecae. A. catenus , A. hohuanmontis and A. shinanmontis have spermathecae varied from being absent to three pairs in VI–VIII and A. proasacceus has two to six spermathecae in VI–VIII. Distance between spermathecal pores in A. demptus is about 1/6 circumference ventrally apart from each other, but about 1/ 5 in A. catenus . In A. demptus , body size is larger and setal numbers are higher than in A. catenus , A. proasacceus and A. hohuanmontis . Based on genital papillae, preclitellar papillae of A. demptus , A. proasacceus and A. shinanmontis are absent. A. catenus has zero to nine preclitellar papillae in V–IX and three to nine postclitellar papillae in XVII–XXI. A. hohuanmontis has no preclitellar papillae and three to six pairs postclitellar papillae in XVIII. In addition, intestinal caeca of A. demptus are transitional between simple and complex, while those of the other four specimens are simple. Accessory glands of A. demptus are small and vestigial, or absent, while A. catenus and A. hohuanmontis have normal accessory glands.

Figures

FIGURE 1. Amynthas demptus Qiu & Jiang, sp. nov. A. Spermathecal pore region. B. Male pore region. C. Spermatheca. D. Intestinal caecum. E. Male pore region and genital papillae in one specimen (YN201738-03) and two specimens (YN201606- 02). F. Left prostate gland (pg) and accessory glands (ag) corresponding to Fig. 1E. G. Male pore region and genital papillae in one sub-adult specimen (YN201734-07). H. Left prostate gland and accessory glands corresponding to Fig. 1G.

Tables

TABLE 3. A comparison of characters of Amynthas demptus sp. nov., Amynthas catenus Tsai et al., 2001, Amynthas hohuanmontis Tsai et al., 2002, Amynthas shinanmontis Tsai & Shen, 2007, and Amynthas proasacceus Tsai et al., 2001.

	A. demptus	A. catenus	A. hohuanmontis	A. shinanmontis	A. proasacceus
Body length (mm)	90–130	61–106	73–113	86–187	39–76
Body width (mm)	4.7–5.6	2.7–4.2	3.41–4.40	2.53–5.19	2.9–3.99
Segment number	89–139	85–103	85–103	75–114	57–106
Dorsal pigment	brown purple	whitish purple	light greyish brown	greyish brown	whitish pink
Ventral pigment	no	whitish gray	light gray	light brown	whitish gray
First dorsal pore	11/12	11/12 or 12/13	12/13	11/12–13/14	11/12
Setal number in III	33–54	20–27	data absent	data absent	data absent
Setal number in VII	78-96	29-38	32-41	31-43	33-40
Setal number in XX	90–111	41–47	42–46	38–55	43–51
Setal numbe between	7–10 (VI), 7–11 (VII)	7–9 (VI), 7–9 (VIII)	data absent	data absent	data absent
spermathecal pores Setal number between male	data absent	7–10	9–11	6–11	6–9
pores in XVIII Spermathecal pores	3 pairs in 5/6–7/8	0–3 pairs in 5/6–7/8	0–3 pairs in 5/6–7/8	invisible	invisible
Male pores	absent	paired in XVIII	paired in XVIII	paired in XVIII	paired in XVIII
Preclitellar genital papillae	absent	V–IX	absent	absent	absent
Postclitellar genital papillae	absent, XVII-XIX, or XV-XXII	XVII–XXI	XVIII	absent	absent
Intestine enlarged from	XV	XV or XVI	XV	XV or XVI	XV
Intestinal caeca	paired in XXVII, extending	paired in XXVII,	paired in XXVII,	paired in XXVII,	paired in XXVII, extending
	anteriorly to XXV, transitional	extending anteriorly to	extending anteriorly to	extending anteriorly to	anteriorly to XX, XXI or
Spermathecae	between simple and complex VI–VIII	XXII, simple vestigial or absent,	XXIV–XXII, simple absent to three pairs in	XXII–XXV, simple vestigial or absent,	XXIII, simple normal, vestigial or absent,
		number variable in	VI-VIII	number variable in	number variable in VI–VIII
Prostate glands	vestigial or absent	VI–VIII paired in XVIII, 3 to 4	vestigial or absent	VI–VIII paired in XVIII or absent	paired in XVIII, 3 to 6
Prostatic duct	absent or S-shaped	segments in XVI–XXI hook-shaped	C- or S-shaped	U-shaped or coiled	segments in XVI–XXI hook-shaped
Accessory glands	stalked, number variable in	solitary, stalked	round, stalked	absent	absent
XV–XXII