Amynthas borealis 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 : 41-42

Amynthas borealis Panha & Bantaowong sp. n. Figs 14

Description of Holotype:

Dimensions; 54 mm by 3.5 mm at segment X, 3.8 at segment XX, 3.5 mm at clitellum; body cylindrical with 89 segments. Setae regularly distributed around segmental equators, numbering 39 at VII, 51 at XX, no visible setae between mp, setae formula AA:AB:ZZ:ZY= 2:1:1.5:1 at XIII. Single fp at XIV. Prostomium epilobic. First dorsal pore at 5/6. Clitellum annular XIV–XVI with no setae.

Mp pocket-like structures indistinctly occur in XVIII, 0.10 circumference apart ventrally; distance between mp 1.0 mm; porophores small, lip-like and surrounded by an elevated skin fold at medial pores, and there is a long ridge with a sharp posterior boundary traversing the body in front of the mp. Genital markings absent. Sp paired in 7/8 at 4th seta line, 0.10 circumference apart ventral; distance between sp 1.0 mm. Genital markings absent.

Septa 5/6 and 6/7 thick, 7/8 thin, 8/9 and 9/10 absent, 10/11-13/14 thin. Gizzard large within VIII–X, intestinal origin in XV, no lymph glands observed. Typhlosole small from XXVII. Ic originated from XXVII extending forward to XXV, simple 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; prostatic ducts long slender bent in U-shape. Genital marking glands absent.

Ovaries at XIII. Sc one pair in VIII; ampulla large sac-shape, flattened by gizzard, narrow duct shorter than ampulla. Diverticulum with elongated tubular shape, stalk attached to duct near body wall, with no genital marking glands.

All the key morphological characters of the holotype and paratype specimens are given in Table 4.

Variation:

The holotype measures 54 mm body length with 89 segments; the eight paratypes range in size from 42-45 mm (42.87 ± 1.25 mm) body length with 77-87 segments (Table 4).

Type locality:

Chaloemprakiat district, Nan province, Thailand, 19°34'48.5"N, 101°04'53.1"E, 513 meters elevation (7th August 2010).

Etymology:

The specific epithet “borealis” derived from Latin word “boreal” mean “north”. This name refers to the location of type locality in the north of Thailand.

Type material:

The holotype (CUMZ 3208) and seven paratypes (CUMZ 3209) are deposited in Chulalongkorn University, Museum of Zoology. Another two paratypes will be deposited in the Biozentrum Grindel und Zoologisches Museum, Hamburg, Germany (UHH), and another two paratypes in the Natural History Museum, London (NHM).

Habitat:

Found in the top soil at about 10 cm depth, the soil surface covered with the leaf litter of a deciduous limestone forest, mostly disturbed. The soil was carefully dug close to the casts.

Diagnosis:

Amynthas borealis sp. n. is a small sized terrestrial earthworm small male pores, a transverse ridge anterior to the male pores in XVII, and no genital mar kings. One pair of sc in VIII, each spermathecae consists of a large sac-shaped ampulla and elongated tubular shaped diverticulum. Testis sacs joined ventrally, intestinal origin XV, intestinal caeca simple, first dorsal pore in 5/6.

Remarks:

Amynthas borealis sp. n. is one of the smaller Amynthas . The characteristic male field is difficult to see in newly collected specimens but can be clearly observed after preservation. 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 similar to Amynthas borealis sp. n. However, distinctive differences include the distance between mp of the new species, being 1.0 mm in the holotype with a range of 0.8-1.0 mm (0.95 ± 0.09 mm) in Amynthas borealis sp. n. compared to 1.5-2.4 mm. The distance between the male pores as a fraction of the estimated circumference of the 18th segment is 0.10-0.14 in Amynthas borealis sp. n., but 0.14-0.32 in Amynthas chandyi . There are no genital markings in the new species; the distance between a pair of sp is also different, being 0.5-1.0 mm (0.9 ± 0.19 mm) in the new species compared to 1.2-1.5 mm for Amynthas chandyi . Moreover, Amynthas borealis sp. n. has no genital marking glands at all, whilst Amynthas chandyi exhibits circular genital markings in various locations, paired or single mid ventral in VII and VIII; usually 3 or 4 in total.