Amynthas lacustris Yuan & 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 : 395-396

Amynthas lacustris Yuan & Jiang sp. nov.

( Figure 2 )

Type material. Holotype. Clitellate specimen ( YN201619-04 ): China, Yunnan, Erhai Nature Reserve (25.73222° N, 100.16611° E), 1966 m asl, shore of Erhai lake , black soil in field, 23 July 2016, X. Gao, Y.F. Lu, J.Z. Jiang .

Paratypes. Two clitellate specimens ( YN201701-01 ): China, Yunnan, Lijiang, Jade Dragon Snow Mountain Nature Reserve (26.95917° N, 100.20030° E), 2558 m asl, 01 August 2017, J.B. Jiang, Y. Dong, Q. Zhao, Z. Yuan ; five clitellate specimens ( YN201719-04 ): China, Yunnan, Dali, Cangshan Nature Reserve (25.78196° N, 100.09094° E), 2363 m asl, 06 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 species is named after its type locality by the shores of Erhai Lake.

Diagnosis. Dimensions 66–71 mm by 2.9–3.2 mm at clitellum, segments 59–87. Setae numbering 32–40 at III, 38–42 at V, 40–48 at VIII, 44–52 at XX, 56–62 at XXV; 6–7 between male pores; 8–10 between spermathecal pores in VI. Spermathecal pores in 5/6–6/7, about 1/3 body circumference ventrally apart. Male pores in XVIII, about 1/3 body circumference ventrally apart, with a presetal and a postsetal papilla medial to each pore, surrounded by two circular folds. Prostate glands at XVII–XXI, developed, thick, lobed. Spermathecae two pairs in VI–VII. Ampulla heart-shaped, spermathecal duct bent, length equal to the ampulla. Diverticulum about 2/3 as long as the main pouch (duct and ampulla together), terminal 4/5 dilated into a ribbon seminal chamber.

External characters. Light-gray pigment on dorsum and ventrum. Dimensions 66–71 mm by 2.9–3.2 mm at clitellum, segments 59–87. Prostomium 1/2 epilobous. First dorsal pore in 10/11. Clitellum in XIV–XVI, dust colour, setae absent, dorsal pores absent. Setae numbering 32–40 at III, 38–42 at V, 40–48 at VIII, 44–52 at XX, 56–62 at XXV; 6–7 between male pores; 8–10 between spermathecal pores in VI; setal formula: AA = 2.0–3.0 AB, ZZ = 2.0–2.2 ZY. Spermathecal pores two pairs in 5/6–6/7, ventral, about 1/3 body circumference ventrally apart, small, genital papillae absent. Female pore single mid-ventral in XIV. Male pores in XVIII, about 1/3 body circumference ventrally apart, each with one presetal and one postsetal papilla medial to each pore, surrounded by two circular folds.

Internal characters. Septa 5/6–7/8 thick and muscular, 10/11–13/14 slightly thick, 8/9–9/10 absent. Gizzard in VIII–X, ball-like; intestine enlarged from XV. Intestinal caeca started from XXVII and ended in XXV, between simple and complicated, finger-shaped, smooth ventral and dorsal margins with 3–4 finger-shaped small lobes. Hearts four pairs in X–XIII. Testis sacs two pairs in X–XI, ovoid, developed, enveloped in one membranous sac. Seminal vesicles two pairs, in XI and XII, the second pair extending in XIII, developed. Prostate glands in XVII– XXI, developed, thick, lobed, prostatic duct slender and transverse in XVIII.

Spermathecae two pairs in VI–VII. Ampulla heart-shaped or pear-shaped; spermathecal duct bent, length equal to the ampulla. Diverticulum about 2/3 as long as the main pouch (duct and ampulla together), terminal 4/5 dilated into a ribbon seminal chamber.

Remarks. Amynthas lacustris sp. nov. keys to Amynthas morrisi -group in Sims and Easton (1972). Species in this group have two pairs of spermathecal pores located in 5/6–6/7. A. lacustris appears to be closely related to Amynthas morrisi (Beddard, 1892) as described in Chang et al. (2009). Male pores of the two species are about 1/3 body circumference ventrally apart with a presetal and a postsetal papilla medial to each pore. However, the two species differ in body size, pigment, male pore and spermathecal pore regions. The body size of A. lacustris is smaller than in A. morrisi , and A. lacustris has a light body colour, in contrast to a "bright brownish gray or dark brown" pigment dorsally in A. morrisi ( Chang et al. 2009) . The male pores of A. lacustris are surrounded with two circular folds, but the male pores of A. morrisi are surrounded with several circular folds, and additional pre-setal papillae are present in XVIII and/or XIX in some specimens. A. lacustris has no genital markings in the spermathecal pore region, but A. morrisi usually has genital markings mid-ventral or medial to spermathecal pores in any or all of the segments V–VII ( Chang et al. 2009).

The arrangement of genital papillae in the male pore region of A. lacustris is also similar to that of Amynthas tripunctus ( Chen, 1946) from Sichuan and Amynthas fucatus Zhao & Jiang, 2013 from Hainan ( Zhao et al. 2013), both in the morrisi -group as well. However, male pores and genital papillae of A. tripunctus and A. fucatus are surrounded by three to five circular folds, and those of A. lacustris are surrounded by only two circular folds. Also, the three species are easily distinguished by the characters of body size, setal formula and intestinal caeca: body sizes of A. tripunctus and A. fucatus are larger than in A. lacustris ; setal formula of A. tripunctus is AA = 1.1–1.5 AB, ZZ = 1.1–1.2 ZY, A. fucatus is AA = 1.0–2.5 AB, ZZ = ZY, A. lacustris is AA = 2.0–3.0 AB, ZZ = 2.0–2.2 ZY; intestinal caeca of A. tripunctus and A. fucatus are simple, those of A. lacustris are between simple and complicated.

Nomenclatural note: " Amynthas lacustris sp. nov. " as introduced in Gao et al. (2018) refers to the same species but is a nomen nudum, unavailable in terms of Zoological Nomenclature, because no description in words was delivered to differentiate the taxon, and type material was not designated ( ICZN 1999, Articles 13.1.1., 16.4). The same applies to two further names in the same paper, " Amynthas wuliangmontis sp. nov. " and " Amynthas jingdongensis sp. nov. ", both unavailable. It is our contribution here that makes the name Amynthas lacustris available.

Figures

FIGURE 2. Amynthas lacustris Yuan & Jiang, sp. nov. A. Spermathecal pore region. B. Male pore region. C. Spermatheca. D. Intestinal caecum. E. Prostate gland.