Amynthas srinan Panha & Bantaowong

Bantaowong, Ueangfa, Chanabun, Ratmanee, Tongkerd, Piyoros, Sutcharit, Chirasak, James, Samuel W. & Panha, Somsak, 2011, New earthworm species of the genus Amynthas Kinberg, 1867 from Thailand (Clitellata, Oligochaeta, Megascolecidae), ZooKeys 90, pp. 35-62 : 43-45

Amynthas srinan Panha & Bantaowong sp. n. Figs 15

Description of Holotype:

Dimensions; 47 mm by 1.8 mm at segment X, 2.3 at segment XX, 2.3 mm at clitellum; body cylindrical with 77 segments. Setae regularly distributed around segmental equators, numbering 36 at VII, 42 at XX, four between mp, setae formula AA:AB:ZZ:ZY= 1.5:1:2:1 at XIII. Single fp at XIV. Prostomium epilobic with tongue open. First dorsal pore at 4/5 or 5/6. Clitellum annular XIV–XVI with no setae.

Mp on circular porophores in XVIII, 0.30 circumference apart ventrally; distance between mp 1.5 mm. Genital markings small, postsetal, closely paired near mid ventral of XVII and XVIII. Sp paired in 7/8 at 6th setal lines, 0.26 circumference apart ventrally; distance between sp 1.5 mm. Genital markings tiny, closely paired on near mid ventral of VII and VIII.

Septa 5/6 and 6/7 thick, 7/8 thin, 8/9 and 9/10 absent, 10/11-13/14 thin. Gizzard globular within VIII–X, intestinal origin in XV, no lymph glands observed. Typhlosole small from XXVII. Ic originated from XXVII extending forward to XXIII, long finger-shape. Hearts esophageal in X–XIII. Holandric; testes and funnels in ventrally joined sacs in X–XI. Sv paired in XI–XII. Prostates in XVIII, extending between XVII–XX; prostatic ducts tightly folded twice. Genital marking glands paired in XVII and XVIII corresponding to external genital papillae, each consisting of a stalk with terminal multi-lobed glandular part.

Ovaries in XIII. Sc one pair in VIII; ampulla oval to kidney-shaped, with stout duct shorter than ampulla. Diverticulum with oval bulb terminal, stalk attached to duct near body wall. Genital markings stalked, corresponding to external genital papillae; each gland small consisting of a stalk with terminal multi-lobed glandular part.

All the key morphological characters of the holotype and paratype specimens are given in Table 5.

Variation:

The holotype measures 47 mm body length with 77 segments and the first dorsal pore located at 5/6; the twenty eight paratypes range in size between 35-47 mm (39.75 ± 4.27 mm) body length with 52-78 segments, and first dorsal pore at 4/5 (8 samples) or 5/6 (20 samples) (Table 5).

Type locality:

Srinan National Park, Nan province, Thailand, 18°22'11.1"N, 100°50'23.2"E, 607 meters elevation (30th September 2010).

Etymology:

This species was named after the type locality Srinan National Park.

Type material:

The holotype (CUMZ 3210) and 25 paratypes (CUMZ 3211) are deposited in Chulalongkorn University, Museum of Zoology. Another five paratypes will be deposited in the Biozentrum Grindel und Zoologisches Museum, Hamburg, Germany (UHH), and four paratypes in the Natural History Museum, London (NHM).

Habitat:

Found in the top soil at about 10 cm depth, the soil surface covered with leaf litters of deciduous forest. The soil was carefully dug close to the castes.

Diagnosis:

Amynthas srinan sp. n. is the smallest Amynthas ever collected in Thailand. Male pores on distinct round porophores, genital markings paired near mid ventral of VII, VIII, XVII and XVIII; each with genital marking glands. Each spermathecae consists of a kidney-shaped ampulla and an oval shaped diverticulum. Testes sacs ventrally joined, intestinal origin XV, intestinal caeca simple, first dorsal pores at 4/5 or 5/6.

Remarks:

Amynthas srinan sp. n., along with Amynthas exiguus exiguus and Amynthas tontong sp. n., is one of if not the smallest Amynthas recorded so far. It has external characteristics which are easily seen in both newly collected and preserved materials. Compared with the two other closely related species from Laos, Amynthas chandyi and Amynthas namphouinensis , which belong in the same zebrus-group, Amynthas chandyi is very similar in appearance to Amynthas srinan sp. n. However, they clearly differ in certain specific details of their significant characters, such as the distance between the mp which in Amynthas srinan sp. n. is 1.5 mm for holotype and ranged from 1.5-2.0 mm (1.41 ± 4.27 mm), while in Amynthas chandyi this ranged from 1.5-2.4 mm. The distance between the male pores as a fraction of the estimated circumference of the 18th segment is 0.24-0.30 in Amynthas srinan sp. n., and 0.14-0.32 in Amynthas chandyi . This is not convincing as a diagnostic difference, because there is significant overlap with the highly variable Amynthas chandyi . In addition, although genital markings are clearly observed in both Amynthas chandyi and Amynthas srinan sp. n. on the sc and mp areas, Amynthas srinan sp. n. has a much larger number and different arrangement of such markings. The distance between pairs of sp is quite similar, being 1.5-2.0 mm (1.34 ± 2.31mm) in Amynthas srinan sp. n. and 1.2-1.5 mm in Amynthas chandyi .