Amynthas thakhantho Bantaowong & Panha, 2014

Bantaowong, Ueangfa, Somniyam, Pattana, Sutcharit, Chirasak, James, Samuel W & Panha, Somsak, 2014, Four new species of the earthworm genus Amynthas Kinberg, 1867, with redescription of the type species (Clitellata: Megascolecidae), Raffles Bulletin of Zoology 62, pp. 655-670 : 665-666

Amynthas thakhantho Bantaowong & Panha , new species

( Figs. 8 , 11E, F ; Table 2)

Material examined. Holotype: One adult ( CUMZ 3308 ), Wat Tham Phra, Tha Khantho, Kalasin, Thailand, (16°51ʹ57.10ʺN, 103°15ʹ17.60ʺE) 220 m in elevation, coll. P. Tongkerd, P. Pimvichai, B. Kongim and N. Nantarat, 15 October 2010. 10 paratypes: 7 adults ( CUMZ 3309 ), 1 adult ( ZMH), 1 adult ( NHMUK), and 1 adult ( ZRC), same collection data as for holoype.

Diagnosis. Large; length 320–402 mm. Male pores paired, superficial in segment XVIII, each on a transversely oval, slightly raised areas, four pairs of postsetal genital markings on segments XVII, XIX, XX and XXI. Spermathecal pores paired in segments 5/6–8/9. Spermathecae large sac-shaped ampulla, diverticulum long, coil or zigzag. Holandric, intestinal caeca simple, first dorsal pore in 12/13. Prostate glands large, its duct long slender, paired sessile genital marking glands on XVII, XIX, XX and XXI.

Description of holotype. Dimensions; 332 mm by 11.1 mm at segment VII, 10.7 mm at segment XX, 10.5 mm at clitellum; body cylindrical with 198 segments. Setae regularly distributed around segmental equators, numbering 108 at VII, 105 at XX, 23 between male pores, setal formula AA:AB:ZZ:ZY=1:1:2:1 at XIII. Single female pore at XIV. Prostomium epilobic. First dorsal pore at 12/13. Clitellum annular XIV–XVI with no setae.

Male pores paired located ventro-laterally in XVIII, 0.27 circumference apart ventrally, distance between male pores 8.5 mm. Male pores, superficial, small transversely oval, slightly raised. Four pairs of genital markings, postsetal on segments XVII, XIX, XX and XXI, in line with male pores. Four pairs spermathecal pores in 5/6–8/9, ventro-lateral, depressed in furrows, almost invisible, distance between the pores about 0.27 body circumference ventrally apart, distance between spermathecal pores 8 mm. No genital markings in or near spermathecal segments.

Septa 5/6–7/8 thick, 8/9–9/10 absent, 10/11–11/12 thin. Gizzard large behind 7/8, intestine begins at XV; the intestinal caeca originate at XXVII, simple and extend to XXIII. Typhlosole rudimentary. Lymph glands begin on dorsal intestinal wall of XXVII. Oesophageal hearts four pairs in X–XIII. Holandric; testes and funnels in X and XI. Large seminal vesicles paired in XI–XII. Prostate glands divided into numerous main lobes, extending from the segment XVI to segment XIX. Prostate duct long, slender with hairpin bend. Sessile genital marking glands present corresponding to each external genital marking in XVII, XIX, XX and XXI.

Ovaries in XIII. Spermathecae four pairs in VI–IX. Large sac ampulla with a long slender duct, clearly marked off from ampulla. The diverticulum slender and long with elongated oval seminal chamber, the distal half of its stalk zigzag or coiled.

Variation. The holotype measures 332 mm body length with 198 segments; the nine paratypes range in size from 320–402 mm (±31.86) body length with segments varied from 196–207. The genital markings on segments XVII, XIX, XX are present in all individuals, with an additional pair in XXI (5), or unpaired in XVI (3), XXI (2), and XXII (1).

Etymology. This species was named after Tha Khantho, Kalasin, the type locality of the new species.

Distribution. The new species is known only from the type locality.

Habitat. Top soil at about 15 cm depth, at pH 7, loamy soil. Worms produce columnar or tower-like castings about 20 cm high and 4 cm diameter.

Remarks. Amynthas thakhantho , new species, is similar to A. phucheefah , new species, with regard to holandry, spermathecal pores in 5/6–8/9, and the body size, but differs in male pore structure, and number and arrangement of genital markings in the male field. Amynthas thakhantho has four pairs of postsetal genital markings on segments XVII, XIX, XX, XXI, whereas A. phucheefah , new species, has six intersegmental pairs on 19/20–24/25 ( Table 2). Otherwise it also differs from other regional members of the corticis species group by a combination of body size and male field characters, as discussed for A. phucheefah .

Figures

Fig. 8. External and internal morphology of holotype (CUMZ 3308) of Amynthas thakhantho, new species: A, external ventral view; B, internal dorsal view; C, spermathecae. Dark arrow indicates the connection of the spermathecae and spermathecal pore.

Fig. 11. Photographs showing typical habitat types of the new species: A, B, Amynthas arenulus, new species. A, earthen dyke around paddy field; B, casting. C, D, Amynthas longicaeca, new species. C, dipterocarp forest; D, casting. E, F, Amynthas thakhantho, new species. E, organic gardening; F, tower–like casting.