Amynthas phatubensis 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 : 37-40

Amynthas phatubensis Panha & Bantaowong sp. n. Figs 12

Description of holotype:

Dimensions; 110 mm by 4.3 mm at segment X, 4.3 at segment XX, 4.0 mm at clitellum; body cylindrical with 108 segments. Setae regularly distributed around segmental equators, numbering 51 at VII, 60 at XX, 15 between mp, setae formula AA:AB:ZZ:ZY= 1:1:1:1 at XIII with no ventral gaps. Single fp at XIV. Prostomium epilobic with tongue open. First dorsal pore at 5/6. Clitellum annular XIV–XVI with no setae.

A pair of mp is located ventro-laterally in XVIII, or at 9th seta line, 0.33 circumference apart ventrally, convex structure; distance between mp 4.2 mm. Porophores (protuberances bearing male aperture), papilla-like structures. Each mp surrounded by six flat, circular genital markings almost the same diameter as mp, also one pair is equatorial in XVII in line with the male pores. One pair of sp in intersegmental furrow 7/8, distance between pores 0.32 circumference ventrally apart; distance between sp 3.5 mm. Genital markings, rounded, flat, located close to sp, postsetal paired on VII very near 7/8, presetal paired on VIII.

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. Intestinal caeca originate from XXVII extending forward to XXIII, simple, long finger-shape. Hearts esophageal in X–XIII. Holandric; testes and funnels in ventrally joined sacs in X–XI. Seminal vesicles paired in XI–XII. Prostates in XVII–XX; prostatic ducts U-shape. Genital marking glands absent.

Ovaries in XIII. Sc one pair in VIII; ampulla large ovate sac, duct stout, short; long stalked diverticulum, convoluted kinks enclosed within membrane, spherical knob terminal. No nephridia on spermathecal ducts. A large sessile genital marking gland corresponding to each external genital marking in VII–VIII.

All the key morphological characters of the holotype and paratype specimens are given in Table 2.

Variation:

The holotype measures 110 mm body length with 108 segments; the twenty one paratypes range in size from 80-148 mm (108 ± 21.93 mm) body length with 85-114 segments (Table 2).

Type locality:

Tham Pha Tub Arboretum, Nan province, Thailand, 18°51'16.4"N, 100°44'10.1"E, 265 meters elevation (11th October 2009). We also collected another lot of further specimens from Tontong Waterfall, Nan province (location 3 in Figure 1), which is located about a hundred kilometers north of the type locality.

Etymology:

This species was named after the type locality, Tham Pha Tub Arboretum.

Type material:

The holotype (CUMZ 3204) and 15 paratypes (CUMZ 3205) and 10 paratypes (CUMZ 3212) are deposited in Chulalongkorn University, Museum of Zoology. Another four paratypes will be deposited in the Biozentrum Grindel und Zoologisches Museum, Hamburg, Germany (UHH), and three paratypes in the Natural History Museum, London (NHM).

Habitat:

Found in the top soil at about 10 cm depth, the soil surface was covered with leaf litter in a deciduous limestone forest at Tham Pha Tub Arboretum. The soil was carefully dug close to the casts. Many ariophantid snails, Cryptozona siamensis Pfeiffer, 1856 were on the ground or under leaf litter.

Diagnosis:

Amynthas phatubensis sp. n. is a medium to large sized terrestrial earthworm with a pair of mp surrounded by six genital papillae on segment XVIII. Within the zebrus-group, this species is diagnosed by the unique combination of dorsal pores in 5/6, simple digitate caeca, ventrally joined testis sacs, genital marking glands in the spermathecal segments, and the spermathecal characters of the large ovate ampulla, stalked diverticulum whose folds are membrane-bound, and spherical knob terminal diverticulum sac.

Remarks:

Amynthas phatubensis sp. n. has very simple characteristics of the genus, but among these, only the superficial male pores are external. In most newly collected specimens it was difficult to observe the pores or marks on the bodies. However, after preservation they can be seen more clearly. The internal organs are much more easily discerned. This new species is quite distinct when compared to the two closely related species from Laos, Amynthas chandyi Hong, 2008 and Amynthas namphouinensis Hong, 2008, which belong in the same zebrus-group. The two Laos species are a little bit smaller than Amynthas phatubensis sp. n., especially Amynthas chandyi . Even though Amynthas namphouinensis is much closer in appearance to Amynthas phatubensis sp. n., there are distinct differences between the type specimens (Figs 6 and 7). For example, the distance between the mp of Amynthas phatubensis sp. n. is 4.2 mm for the holotype and range from 3.0-4.5 mm (4.27 ± 0.57mm), while for Amynthas namphouinensis this was significantly smaller, ranging from 1.4-1.5 mm. The distance between a pair of sp is also different, being 3.5-4.5 mm (4.12 ± 0.4 mm) for Amynthas phatubensis sp. n. and 1.4-2.0 mm in Amynthas namphouinensis . The distance between the male pores as a fraction of the estimated circumference of the 18th segment is 0.30-0.33 in Amynthas phatubensis sp. n., but 0.10-0.14 circumference apart in Amynthas namphouinensis . Moreover, Amynthas phatubensis sp. n. has no genital marking glands on segments XVII–XIX, where Amynthas namphouinensis has sessile genital marking glands, but contains two distinct genital marking glands located close to sc that are absent in Amynthas namphouinensis .

Two populations of Amynthas phatubensis sp. n. were sampled, one from the type locality and one from Tontong waterfall. Distinct DNA barcode clusters corresponding to these populations had intra-cluster Kimura 2 parameter distances of 0.023 (N=9) and 0.016 (N=5) respectively. The inter-cluster divergence between the two populations is 0.084. Based on the morphological unity and the fact that the divergence is less than that usually seen between congeneric species pairs of earthworms ( Chang et al. 2007; Pérez-Losada et al. 2005, James et al. 2010), we choose to maintain the two populations as representing one species. By contrast, the inter-cluster divergence between these populations and three other morpho-species with the same spermathecal battery, from the same two sites is in the range of 0.269-0.294. A consensus sequence from the type locality specimens is in Appendix 1. Another use of COI barcode sequence from type material is in Blakemore et al. (2010).