Amynthas hiatus Qiu & Yuan, 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 hiatus Qiu & Yuan sp. nov.

Type material

Holotype. One clitellate specimen ( YN201107-14 ): China, Yunnan, Xishuangbanna Nature Reserve (21.61° N, 101.58° E), 694m elevation, red soil in tropical rain forest, 20 July 2013, J.B. Jiang, J. Sun, X.D. Lei and H.W. Feng.

Etymology

The species is named after its characteristic dentate-shaped caecum.

Diagnosis

Dimensions 156 mm by 5.5 mm at clitellum, segments 130. Setae numbering 26 at III, 34 at V, 44 at VIII, 64 at XX, 66 at XXV; 9 between male pores (XVIII); 14 between spermathecal pores (VIII). Spermathecal pores in 7/8-8/9, about 1/3 body circumference ventrally apart. Male pores in XVIII, about 1/3 body circumference ventrally apart, each on top of a large raised pulvinate pad, surrounded with four circular folds. Prostate glands at XVI-XIX, moderately developed, thick, massive leaf composition. Spermathecae two pairs in VIII- IX; ampulla heart-shaped, ampulla duct thick and short, length about 2/5 of the ampulla. The length of diverticulum as long as the main pouch (duct and ampulla together), terminal 1/3 dilated into an ovoid seminal chamber.

External characters

Puce dorsal pigment, no pigment on ventrum. Dimensions 156 mm by 5.5 mm; segments 130. Prostomium 1/3 epilobous. First dorsal pore in 12/13. Clitellum in XIV-XVI, smooth, no setae and dorsal pores. Setae numbering 26 at III, 34 at V, 44 at VIII, 64 at XX, 66 at XXV, 9 between male pores (XVIII), 14 between spermathecal pores (VIII); setal formula: AA = AB, ZZ = 1.8 ZY.

Spermathecal pores two pairs in 7/8-8/9, ventral, about 0.33 circumference ventrally apart from each other, pores not clear.

Female pore single mid-ventral in XIV, oval.

Male pores one pair in XVIII, about 0.33 circumference ventrally apart from each other, each on top of a lager raised pulvinate pad, surrounded with four circular folds. Between male pore level, post-setal in XVII and presetal in XIX, one pair of round flat papillae with depressed centres, and spacing about 1/4 perimeter. The area surrounded by four papillae and two chamber present large and slightly swollen glandular region.

Internal characters

Septa 5/6-6/7 thick, 7/8 and 10/11-13/14 slightly thick, 8/9-9/10 absent. Gizzard in VIII-X, barrel-shaped. Intestine enlarged gradually in XVIII, XV-XVIII very fine, enlarged again in XIX. Intestine caeca start from XXVII and end in XX, transitional between simple and complex, ventral and dorsal edges with obvious small serrated. 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, not developed. Prostate glands at XVI-XIX, moderately developed, thick, massive leaf composition. Prostatic duct C-shaped, at XVIII.

Spermathecae two pairs, at VIII-IX, the first pair about 1.9 mm, the second pair about 2.2 mm. Ampulla heart-shaped, ampulla duct thick and short, length about 2/5 of the ampulla. The length of diverticulum as long as the main pouch (duct and ampulla together), terminal 1/3 dilated into an ovoid seminal chamber.

Remarks

Amynthas hiatus sp. nov. belongs to the Amynthas aeruginosus -group in Sims and Easton (1972). In appearance, A. hiatus is somewhat similar to Amynthas triastriatus (Chen, 1946) which is one of the key species in the A. aeruginosus -group. The first dorsal pore of A. hiatus is in 12/13, the setae are uniformly thick and the rear body denser, the male pores area is complicated, the prostate glands are moderately developed. However, the first dorsal pore of A. triastriatus is in 10/11, the setae longer before VIII and the rear body is uniformly dense, the papillae in the male pore area only present medial to each male pore in XVIII, the ampulla duct is wide, and the prostate glands are absent.

Another similar species is Amynthas robustus (Perrier, 1872) . Amynthas robustus is a common species in Asia. This species and the new species share some similar characters: normal or developed prostate, and no accessory glands near the prostate. But, the differences are obvious; for example, the body size of the new species is larger than A. robustus ; pigment of the new species is puce on the dorsum and no pigment on ventrum, but light red or reddish brown in A. robustus ; locality of the first dorsal pore; intestine caeca of the new species is between simple and complicated, while that of A. robustus is simple.

A comparison of characters between this new species and two other similar species has been given in Table 2 .

According to the molecular data, the K2P distances of COI sequences and combined COI and 12S sequences between A. hiatus and the other similar species in the A. aeruginosus -group are shown in Table 5 . The distances were> 15%, but A. hiatus is more similar to A. robustus than A. triastriatus . In the NJ tree ( Figure 4 ), the three species were not in the same clade.

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.