Amynthas piyakarnae Hong and James, 2024

Hong, Yong, Inkhavilay, Khamla & James, Samuel W., 2024, Three new earthworms of the Amynthas corticis-group (Clitellata: Megascolecidae) from the Nam Et-Phouleoi, Laos, Zootaxa 5405 (2), pp. 273-280 : 278

Amynthas piyakarnae Hong and James sp. nov.

( Fig. 4 )

Material. Holotype: 1 clitellate ( BDNUL 0060 ): Laos, Houaphanh Province, Viengthong District, Nam Et-Phouleoi NPA, Summit of Phouleoi Mountain , 2,273 m (20°16.323′N, 103°1.772′E), wet mossy forest, very thick organic soil surface, July 23, 2005, Boutong, Phimphet, Son, and K. Inkhavilay colls . Paratype: 1 clitellate ( BDNUL 0061 ), same data as holotype . Non-types: 1 clitellate, same data as for holotype .

Etymology. The species is named after the second author’s daughter, Piyakarn Inkhavilay.

Diagnosis. Spermathecal pores paired in 5/6–8/9 at 9 th setal line; male pores superficial at lateral ends of transverse elongate oval pads elevated equatorially on XVIII, pads surrounded by 3–4 small outer rings, 0.25–0.31 circumference apart; genital markings circular, pre-setal VIII, IX; row of 3–5 small round genital papillae pre-setal in XVIII, evenly spaced; 2 or 4 genital papillae in row, pre-setal in XIX; pinnate intestinal caeca, additional small caecal lobes on XXVIII, first dorsal pores in 5/6 or nearby.

Description. Dimensions 98–142 mm by 5.0– 5.5 mm at segment X, 4.5–5.2 mm at segment XXX, 4.5–4.7 mm at clitellum; body cylindrical, segments 66–129 (possibly some natural amputees). Setae regularly distributed around segmental equators, numbering 34–40 at VII, 57–58 at XX, 13–16 between the male pores, setal formula AA:AB:ZZ:YZ = 4:3:5:3 at XIII. Female pore single XIV on 0.3–0.4 mm oval porophore. Prostomium epilobic with tongue open, pigment dark red-brown on dorsal anterior, ventral I–IV only; clitellum coffee color, formalin preservation. First dorsal pore at 5/6 (2 individuals), 6/7 (1 individual). Clitellum annular XIV–XVI; setae invisible externally.

Male pores superficial at lateral margins of ventrum in XVIII at 9 th setal line, 0.25–0.31 circumference apart ventrally at lateral ends of transverse elongate elevated oval pads equatorial on XVIII, pads surrounded by 3– 4 small outer rings; row of 3–5 small round genital papillae pre-setal in XVIII, evenly spaced; 2 or 4 genital papillae in a row, pre-setal in XIX, 2 pre-setal in XX (one individual). Spermathecal pores paired in 5/6–8/9 at 9 th setal line, inconspicuous at lateral margins of ventrum, 0.27–0.29 circumference apart ventrally. Genital markings circular, paired pre-setal VIII and IX (2 individuals); pre-setal mid-ventral VIII and IX plus single left pre-setal IX (1 individual).

Septa 5/6/7 thick, 7/8 thinly muscular, 8/9/10 absent, 10/11–12/13 thinly muscular. Gizzard large in VIII– X. Intestine beginning in XV, lymph glands not found. Typhlosole thick low ridge from XXVII. Intestinal caeca originating in XXVII and extending anteriorly about to XXV, pinnate, each divided into 13–17 small finger-shaped lobes; 2–3 dorsal caecal lobes in XXVIII. Hearts esophageal X–XIII. Male sexual system holandric, testes and funnels in ventrally joined sacs in X and XI. Seminal vesicles paired in XI and XII; dorsal lobes lacking. Prostates in XVIII, and extending from XVII–XXII; glandular portions consist of 2 main lobes each divided again into 2–4 small lobes. Genital papillae glands in segments XVIII and XIX with very short stalks or sessile.

Ovaries in XIII. Spermathecae paired VI–IX; 2 pairs in VII; ampulla oval, small black spots on surface, slender ducts shorter than ampulla; diverticulum chamber chili-shaped, with stalk as long as ampulla attached near body wall, no nephridia on ducts. Mushroom-shaped genital marking glands in VIII and IX on ventral body wall.

Remarks. Like the other species described here, the distinctions from the main body of the A. corticis -group are the pinnate caeca and the forward position of the dorsal pores.

The new species similarly bears some superficial similarities to A. duplidiverticulatus , with respect to the shape of the male pore region and presence of genital papilla between the male pores. However, A. duplidiverticulatus has a greater number of setae compared to the new species (81 vs. 34–40 at VIII, and 66 at XIX vs. 58 at XX). A. duplidiverticulatus has simple intestinal caeca, but Amynthas piyakarnae sp. nov. has pinnate intestinal caeca. Spermathecal forms differ and A. duplidiverticulatus lacks genital marking glands, but the new species has the mushroom-shaped genital marking glands in VIII and IX on ventral body wall. The male pore region and genital papillae are unique to this species.

The Laos A. corticis -group appears in various forms. In particular, individuals of many species show different external characteristics, such as genital markings, and genital papillae. Even in the same location, they show different appearances depending on their habitat, or even on the same mountain in one region, depending on altitude. Even in the genus Amynthas , the corticis -group, which has four pairs of spermathecal pores, is highly variable. In the Laos A. corticis -group, the morphology of the intestinal caeca was important characteristic. Along with the simple, manicate, and pinnate types, it is one of the characteristics necessary for species recognition. In future research, research on the mutual evolution between these different types through molecular biological analysis of intestinal caeca types within the genus Amynthas corticis -group is expected to be an important clue for understanding this group.

Figures

FIGURE 4. Amynthas piyakarnae sp. nov. (A, B). A: ventral view; B: intestinal caeca; C: spermatheca. Scale bars 2 mm.