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

publication ID

https://doi.org/ 10.11646/zootaxa.4664.3.6

publication LSID

lsid:zoobank.org:pub:A048266B-6FF5-4CB0-B3A7-EEB6774F40DD

persistent identifier

https://treatment.plazi.org/id/03967F7D-FFDB-FF8F-FF59-A0F95EFFFAE9

treatment provided by

Plazi

scientific name

Amynthas demptus Qiu & Jiang
status

sp. nov.

Amynthas demptus Qiu & Jiang , sp. nov.

( Figure 1 View 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 GoogleMaps . 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 GoogleMaps ; 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 GoogleMaps ; 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 GoogleMaps .

NCBI accession numbers of some of the type specimens are listed in Table 2 View 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 View FIGURE 1 ), eight pairs papillae in XV–XXII for one sub-adult specimen ( Fig. 1 G View FIGURE 1 ). 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 View FIGURE 1 ); 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 View FIGURE 1 ).

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 View 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.

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
VI

Mykotektet, National Veterinary Institute

Kingdom

Animalia

Phylum

Annelida

Class

Clitellata

Order

Opisthopora

Family

Megascolecidae

Genus

Amynthas

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