Amynthas recavus Yuan & Jiang, 2019

Yuan, Zhu, Dong, Yan, Jiang, Jibao & Qiu, Jiangping, 2019, Three new species of earthworms belonging to the genera Amynthas and Metaphire (Oligochaeta: Megascolecidae) from Yunnanı China, Journal of Natural History 53 (31), pp. 1961-1974 : 1961-1974

Amynthas recavus Yuan & Jiang sp. nov.

Type material

Holotype. One clitellate specimen ( YN201109-09 ): China, Yunnan, Xishuangbanna , Mengla County (21.40° N, 101.62° E), 722 m elevation, red soil in forest, 20 July 2013, J. B. Jiang, J. Sun, X.D. Lei and H.W. Feng.

Other materials. Two clitellate specimens ( YN201739-07 ): China, Yunnan, Ruili, Tongbiguan Nature Reserve (24.10° N, 98.01° E), 830 m asl, 11 August 2017, J.B. Jiang, Y. Dong, Q. Zhao, Z. Yuan.

Etymology

The species is named after its characteristic male pores.

Diagnosis

Dimensions 58–64 mm by 2.1–2.3 mm at clitellum, segments 82–84. Setae numbering 21–22 at III, 22–24 at V, 34–36 at VIII, 34–36 at XX, 36–40 at XXV; 9–10 (XVIII) between male pores; 11–12 (VI), 10–12 (VII), 12 (VIII) between spermathecal pores. Spermathecal pores in 5/6-8/9, about 2/5 body circumference ventrally apart. Male pores in XVIII, about 1/3 body circumference ventrally apart, each on top of a raised, elliptic, collapse-topped porophore, surrounded with one circular folds. Prostate glands at 1/2XVII-XIX, relatively small, one lump. Spermathecae four pairs, at VI-IX. The ampulla elongated oval-shaped; the ampulla duct uniformly thick, about 4/5 of the ampulla. The length of diverticulum about 3/5 of the main pouch (duct and ampulla together), terminal 1/4 slightly dilated into an ovoid seminal chamber.

External characters

Pigment on dorsum presents pink before clitellum, light brown on dorsum after clitellum, no pigment on ventrum. Dimensions 58–64 mm by 2.1–2.3 mm at clitellum, segments 82–84. Prostomium 1/2 epilobous. First dorsal pore in 12/13. Clitellum in XIV-XVI. S Setae numbering 21–22 at III, 22–24 at V, 34–36 at VIII, 34–36 at XX, 36–40 at XXV; 9–10 (XVIII) between male pores; 11–12 (VI), 10–12 (VII), 12 (VIII) between spermathecal pores; setal formula: AA = 1.0–1.1 AB, ZZ = 1.8 ZY.

Spermathecal pores four pairs in 5/6-8/9, ventral, about 2/5 circumference ventrally apart from each other, eye-shaped.

Female pore single mid-ventral in XIV.

Male pores one pair in XVIII, about 1/3 circumference ventrally apart from each other, each on top of a raised, elliptic, collapse-topped porophore, surrounded with one circular fold. One pair of oval, flat papillae in pre-setal XVII, and three oval, flat papillae in pre-setal XIX.

Internal characters

Septa 5/6-6/7 thick and muscular, 7/8 and 10/11-14/15 slightly thick, 8/9-9/10 absent. Gizzard in VIII-X, ball-like; intestine enlarged gradually from XVI. Intestine caeca start in XXVII, end in XXV, simple, finger-shaped, smooth ventral and dorsal margins. Hearts four pair in X-XIII, the first pair long and thin, the others are larger.

Testis sacs two pairs, in X-XI, oval, developed, separated from each other. Seminal vesicles two pairs, extending in XI-XII, relatively small. Prostate glands at 1/2XVII-XIX, relatively small, one single dense racemose mass, prostatic duct C-shaped.

Spermathecae four pairs, about 1.4 mm, in VI-IX. Ampulla thin heart-shaped, ampulla duct uniformly thick, the length of the duct about 4/5 of the ampulla. The length of diverticulum about 3/5 of the main pouch (duct and ampulla together), terminal 1/4 slightly dilated into an ovoid seminal chamber.

Remarks

Amynthas recavus sp. nov. belongs to the Amynthas corticis -group in Sims and Easton (1972). We compare it to Amynthas corticis (Kinberg, 1867) as described in Chang et al. (2009). Both species have four pairs of spermathecal pores in 5/6-8/9. However, the two species differ in body size, male pore and spermathecal pore regions. The body size of A. recavus is smaller than in A. corticis . The male pores of A. recavus are surrounded with one circular fold and about 1/3 body circumference ventrally apart with one pair of papillae in pre-setal XVII and three papillae in pre-setal XIX, but the male pores of A. corticis are surrounded with one or two circular folds with or without papillae. Both species have no genital markings in the spermathecal pore region, but the distance between spermathecal pores of A. recavus is about 2/5 circumference ventrally apart each other, that of A. corticis is about 0.28.

A. recavus also appears to be closely related to Amynthas yunlongensis (Chen & Xu, 1977) ( Table 3 ), a similar species was found from Yunlong in Yunnan Province. The prostate glands trend to degradation: the prostate of A. recavus is relatively small with only one lump; A. yunlongensis has prostatic duct only, no prostate gland. There are some differences between these species: the body of A. recavus is more slender, and its setae are more intensive; the distance between male pores of A. recavus is about 2/5 circumference ventrally apart each other, the distance between male pores of A. yunlongensis is about 1/3; papilla around male pores of the two species have a different spatial distribution; testis sacs and seminal vesicles in XI of A. recavus are independent of each other, but in A. yunlongensis , testis sacs wrap seminal vesicles in XI; the spermathecae of A. recavus are developed, while A. yunlongensis only 4 pairs of granulation porophores could be seen.

When compared to the new species with Amynthas exiguus (Gates, 1930) , the COI gene region of A. exiguus is 92% similar using a BLAST search (https://blast.ncbi.nlm.nih.gov/ Blast.cgi), yet we observed that A. recavus has a larger size body; the spermathecal pores of A. recavus are eye-shaped, while spermathecal pores of A. exiguus are minute and superficial; moreover, the characters of the male pores are different, details presented in Table 3 .

According to the molecular data ( Table 5 ), the K2P distances of combined COI and 12S sequences between A. recavusı A. yunlongensis and A. corticis are 15.9% and 14.9% respectively. Amynthas recavus and A. hiatus are in the same clade with 70% bootstrap support. But, A. recavusı A. yunlongensis and A. corticis were in different clades ( Figure 4 ).

Figures

Figure 4. Neighbour-joining (NJ) tree of these species: based on combined analysis of COI and 12S sequences. Bootstrap values (1000 replicates) of NJ analyses are shown above/below the main lineages. Lumbricus rubellus was used as the outgroup taxa.