Amynthas bantanensis Chanabun & Panha, sp. nov.

Chanabun, Ratmanee, Aoonkum, Anuwat, Seesamut, Teerapong, Bantaowong, Ueangfa & Panha, Somsak, 2023, Four new terrestrial earthworm species from the northeast Thailand (Oligochaeta, Megascolecidae), ZooKeys 1176, pp. 195-219 : 195

Amynthas bantanensis Chanabun & Panha, sp. nov.

Fig. 9

Type material.

Holotype: Adult specimen (CUMZ 3827) Ban Tan, Nawah, Nakhon Phanom, northeast of Thailand, 17°30'28.0"N, 104°05'48.0"E, 149 m a.m.s.l., 28 September 2018, coll. R. Chanabun, A. Aoonkum. Paratypes: 3 adults (CUMZ 3828), 2 adults (NHMUK); same collection data as for holotype.

Diagnosis.

Medium-large size, length 159-213 mm, diameter 8-10 mm, 105-149 segments. Paired male pores in segment XVIII, surrounded by four genital papillae each. Paired spermathecal pores in intersegments 6/7-8/9. Spermathecae elongated sacs, with slender and long stalks of the ampulla, diverticulum slender, long at the beginning, zigzagged at the center, and slender towards the end. Holandric. Intestinal caeca are simple. First dorsal pore in 12/13. Prostate gland large and well developed in XVI-XXII; its duct is short, smooth and curled like a spiral.

Description of holotype.

Length 191 mm, diameter 8 mm, body cylindrical, 127 segments. Preserved specimens are dark brownish on the dorsal part and pale gray on the ventral part. Setae are regularly distributed around the segmental equators, numbering 37 at segment VII, 57 at segment XX, and 12 between male pores at segment XVIII. Setal formula AA:AB:ZZ:ZY=1:1:2:1 at XIII. Single female pore mid-ventrally at segment XIV. Prostomium epilobic. First dorsal pore in 12/13. Clitellum annular in XIV-XVI with no dorsal pores or setae.

Male pores paired on the ventral side of XVIII, ~ 9 mm apart, distance 0.32 × body circumference. Male pores superficial, convex, each surrounded by four genital markings. Spermathecal pores three pairs in 6/7-8/9. The distance between each pair is ~ 0.41 × the body circumference ventrally apart. There are no genital markings in this area.

The septa in 5/6-7/8 thick, absent at 8/9-9/10, slightly thick in 10/11-11/12, thin in 12/13-14/15, and very thin behind 15/16. Gizzard large in IX. Intestine begins at segment XV. Vary long and simple intestinal caeca in XXVII-XIX. Esophageal hearts four pairs in segment X-XIII. Holandric; testes and funnels in X and XI. Seminal vesicles are paired, one in X-XI, the other one in XII-XIII. The prostate glands are large and well-developed, located in segments XVI-XXII and divided into several lobules. Prostate duct is relatively short, smooth, and spiraled.

Ovaries in segment XIII. Three pairs spermathecae in VII-IX. Spermathecae elongated sacs, with slender and long stalks of the ampulla, diverticulum slender, long at the beginning, zigzagged at the center, and slender towards the end.

Variation.

Five paratypes range in size from 159-213 mm (183.83 ± 20.54 mm) body length with 105-149 segments (124 ± 14.39 mm) (Table 4 ).

Etymology.

The name bantanensis is given to this species for its type locality at Ban Tan, Nawah, Nakhon Phanom.

Distribution.

This species is known only from the type locality.

Remarks.

Amynthas bantanensis sp. nov. is sexthecal with spermathecal pores in 6/7-8/9, belonging to the Amynthas aelianus species group. The new species differs from other Amynthas aelianus species group reported by body size, location of spermathecae and spermathecae, A. bantanensis sp. nov. is similar to A. burchardi from Sumatra, and A. osmastoni from the south Andaman Islands in body dimensions, but easily distinguished from A. burchardi which has a mid-ventral group of small circular papillae on segment XVIII, while they are absent in the new species. Amynthas osmastoni has genital markings at the pre-clitellum, which are absent in the new species. Amynthas bantanensis sp. nov. differs from A. monsoonus and A. huangi from Taiwan in that the new species has genital markings in the male pores region, whereas they are absent in A. monsoonus and A. huangi . Amynthas monsoonus has a smaller body size of 102 mm, a diameter of 3.6 mm, with 83 segments, and genital markings in segments VII-IX. Amynthas huangi has a smaller body size, a body range of 70 mm, a diameter of 3.5 mm, and 101 segments, and A. huangi has genital marking glands in the body wall in VI-IX, while the new species lacks them. The new species has genital markings in the male pores region, whereas they are absent in A. monsoonus and A. huangi .

Amynthas bantanensis sp. nov. differs from A. arenulus from Surin, Ubon Ratchathani, and Srisaket in that A. arenulus has a large transverse elliptical disc surrounded by an elevated rim with an indistinct male aperture located at the outer edge of each poropore and consists of a large sessile glandular mass on the body wall in this region, while the new species has genital markings at segment XVIII, near the male pore, but has no glandular mass on the body wall. Amynthas bantanensis sp. nov. is easily distinguished from A. fucosus from Burma and A. siam from Thailand because both previously reported species have smaller body sizes ( A. fucosus = 6 mm, A. siam = 3 mm). Amynthas fucosus has two pairs of genital markings at 17/18, 18/19, and A. siam has a single pair between the male pores, while the new species has four genital markings surrounded by male pores at segment XVIII. The new species, Amynthas bantanensis , is similar body dimensions to A. longicaeca from Chaiyaphum, but is easily distinguished by A. longicaeca having crescent-shaped genital markings and a large sessile glandular mass on the body wall, while the new species lacks it. Considering the differences between A. bantanensis sp. nov., A. auriculus sp. nov., and A. sakonnakhonensis sp. nov. see the respective remarks sections above and Table 5 .

Figures

Figure 9. External and internal morphology of Amynthas bantanensis sp. nov., holotype (CUMZ 3827) A external ventral view B internal dorsal view, and C spermatheca with location of spermathecal pore arrowed.