Amynthas chiakensis, Hong, Yong & James, Samuel W., 2013

Hong, Yong & James, Samuel W., 2013, Three new earthworm species of the genus Amynthas (Clitellata: Megascolecidae) from Mt. Chiak National Park, Korea, Zootaxa 3646 (1), pp. 75-81 : 76-80

Amynthas chiakensis sp. nov.

( Fig. 1 A, B)

Material. Holotype: clitellate (NIBRIV0000261338), Korea, Gangwon-do Province, Wonju-si, Socho-myon, Mt. Chiak (37°14.074'N, 128°59.151'E), 600–800 m, soil and litter layers, 9 August 2006, Y. Hong, N. J. Choi, and Y. P. Kim colls. Paratypes: 1 clitellate (NIBRIV0000261339); same data as for holotype. Nontype material: 5 clitellates, same data as for holotype.

Etymology. The species is named after the type locality.

Diagnosis. Spermathecal pores two pairs deep in 6/7–7/8; no genital markings in pre-clitellar segments; male pores at centers of small transverse oval porophores, near lateral margins of ventrum in XVIII, each with concentric wrinkled rings around the porophore, in which are embedded groups of small circular papillae, sometimes in C-shaped array open laterally; male pores 0.22–0.31 circumference apart ventrally; cecum manicate.

Description. Dimensions 70–82 mm by 4.0– 4.7 mm at segment X, 4.6–5.5 mm at segment XXX, 4.1–5.0 mm at clitellum; body cylindrical, segments 93–94. Setae spaced regularly around segment, numbering 54–63 at VII, 59–71 at XX, 18–22 between male pores, setal formula AA:AB:ZZ:YZ= 1:1:1:1 at XIII. Female pore single XIV on 0.3–0.4 mm circle. Prostomium epilobic with tongue open. Dorsal pigment brown, clitellum coffee color in formalin preservation. First dorsal pores at 12/13 (4), 11/12 (3). Clitellum annular XIV–XVI; setae invisible externally.

Male pores at centers of small transverse oval porophores, near lateral margins of ventrum in XVIII; each with concentric wrinkled rings around the porophore, in which are embedded groups of small circular papillae, sometimes in C-shaped array open laterally; male pores 0.22–0.31 circumference apart ventrally; 4.2–5.0 mm distance between male pores. Groups of 2–4 small genital papillae, paired presetal median to porophores in XVIII, or presetal anterior to the groups on the porophores; non-porophore genital papillae groups may be lacking. Spermathecal pores two pairs deep in 6/7–7/8, 0.25–0.34 ventral circumference apart; distance between spermathecal pores 4.0– 4.5 mm. Genital markings lacking.

Septa 4/5–6/7 thick, 7/8 thin, 8/9/10 absent, 10/11–12/13 thick. Gizzard large in VIII–X. Intestine begins in XV, lymph glands not found. Typhlosole absent. Intestinal cecum originating in XXVII and extending anteriorly about to XXIV, manicate with 4–5 small finger-shaped lobes decreasing in size ventrally. Esophageal hearts in X– XIII. Male sexual system holandric, testes and funnels in ventrally joined sacs in X–XI. Seminal vesicles small in XI–XII with dorsal lobes. Prostates in XVIII, extending from XVI–XXII; stout ducts straight to U-shaped, both glandular portions consist of 2 main lobes each divided into 5–6 small lobes. Small stalked genital papillae glands in XVIII; some almost hidden in body wall.

Ovaries in XIII. Spermathecae in VII and VIII; wrinkled ovate ampulla, duct shorter than ampulla; duct diameter and muscularity increase ectally, diverticulum chamber elongate fusiform, almost as long as ampulla, with thin muscular ental part of stalk, dramatically thicker ectal section, total stalk length greater than ampulla, stalk attaches near the base of spermathecal duct, no nephridia on spermathecal ducts. Genital marking glands are lacking.

Remarks. This species keys to the tokioensis group in Sims & Easton (1972), but differs from the previously known species with manicate cecum in lacking genital markings in the spermathecal segments. The diverticulum chamber is similar to that of A. tokioensis (Beddard, 1892) , but different in the stalk morphology by the enlarged ectal portion (as figured in Blakemore 2006). All the manicate species of the complex were collected from Korea. Amynthas vittatus (Goto & Hatai, 1898) , A. levis (Goto & Hatai, 1899) , A. shinkeiensis (Kobayashi, 1938) , (all probably synonyms of A. tokiensis and mostly variously modified parthenogenetic morphs according to Blakemore (2006)) and A. sonjaesiki Hong & James, 2009 also have manicate intestinal cecum. Resolving the taxonomic issues associated with extensive parthenogenetic modification of sexual characters is a difficult problem in this group of earthworms, among others (cf. Blakemore 2006), and will require extensive resampling for molecular data.

The present new species appears to be related to A. sanchongensis Hong & James, 2001 with respect of the shape of male pore region, but it differs in the genital markings. Amynthas sanchongensis has clusters of small genital markings anterior and posterior to each spermathecal pore, but A. chiakensis lacks these.

Amynthas chiakensis sp. nov. is similar to one other species described from Korea, Amynthas sonjaesiki , with which it shares the same array of hearts, missing septa, segment of intestinal origin and vestigial typhlosole. This combination of characters differentiates these two species from other group members. Genital papillae of the male pads are useful for taxonomy of Amynthas and have been used throughout the history of the genus (Hong & James 2001, 2009). However, A. sonjaesiki differs from Amynthas chiakensis sp. nov. only in having numerous small genital markings close to the spermathecal pores in VII (8–11 per group) and VIII (11–16 per group), while this new species has none anywhere in VII or VIII in the seven specimens examined. It is recognized that genital markings are often variable within a species, but in this case there was no variation within the study collection. The two species were found in different locations, Mt. Chiak and Mt. Songni. It is very interesting that many species of Amynthas with spermathecal pores in 6/7 and 7/8 have been found in Korea, Japan, Taiwan, Vietnam, and Laos, but only few in the south of China.

Amynthas gyeongriae sp. nov. ( Fig. 1 C, D)

Material. Holotype; clitellate (NIBRIV0000261340): Korea, Gangwon-do Province, Wonju-si, Socho-myon, Mt. Chiak (37°14.074’N, 128° 59.151’E), 600–800 m, soil and litter layers, 9 August 2006, Y. Hong, N. J. Choi, and Y. P. Kim colls. Paratype: 1 clitellate (NIBRIV0000261341): same data as for holotype. Other material: 1 clitellate specimen, same data as for holotype.

Etymology. Named for the late Park Gyeong Ri (1926–2008), a great Korean writer who lived near Mt. Chiak.

Diagnosis. Spermathecal pores three pairs just posterior to 5/6–7/8; no genital markings in pre-clitellar segments; male field with large oval raised pads, each pad surrounded by white outer ring and extending from 17/ 18–18/19; male pores 0.16–0.28 circumference apart; caeca simple with ventral margin pockets.

Description. Dimensions 115–135 mm, by 5.5–7.0 mm at segment X, 6.5–7.0 mm at segment XXX, 5.0– 6.5 mm at clitellum; body cylindrical, segments 106–115. Setae spaced regularly around segments, numbering 26–42 at VII, 66–67 at XX, 13 between male pores, setal formula AA:AB:ZZ:YZ= 4:3:3:3 at XIII. Female pore single XIV on 1.2–1.3 mm oval porophore. Prostomium epilobic with tongue open, dorsal light brown, clitellum coffee color in formalin preservation. First dorsal pore at 12/13. Clitellum annular XIV–XVI, setae invisible externally.

Male field with large circular-shaped raised pads; each pads surrounded by white outer ring and extending from 17/18–18/19 with transverse seminal groove curve around posterior edge of oval male pad in XVIII, male pores in grooves at medial edge of oval pad, 0.16–0.28 circumference apart ventrally; around 4.6–5.0 mm distance between male pores, genital papillae absent. Spermathecal pores three pairs just posterior to 5/6–7/8, each pore a short transverse slit with elevated margin, 0.25–0.44 ventral circumference apart from each other; 4.9–7.0 mm distance between spermathecal pore. Genital markings lacking.

Septa 5/6–7/8 thick, 8/9/10 absent, 10/11–12/13 thick. Gizzard globular in VIII–IX. Intestine begins in XV, lymph glands not found. Typhlosole thick, 1/4 intestine diameter from XXVII. Intestinal caeca originating in XXVII and extending anteriorly about to XXI, simple finger-shaped with 8 more or less small distinct pockets on ventral margins. Esophageal hearts in X–XIII. Male sexual system holandric, testes and funnels in annular sacs in X, XI, sacs include hearts, dorsal vessel in X, hearts in XI. Seminal vesicles paired in XI, XII, without dorsal lobes, vesicles of XI inside testes sac. Prostates in XVIII, extending from XVI–XX, short stout ducts, glandular portions consist of 2 main lobes, each main lobe divided again into 4–5 small finger-shaped branches. Genital papillae glands are lacking.

Ovaries in XIII. Spermathecae in VI–VIII; ampulla globular-shaped, smooth, slender ducts as long as or longer than ampulla, diverticulum chamber cylindrical with rounded chamber as long as spermathecal ducts, stalk shorter; no nephridia on spermathecal ducts. No genital marking glands.

Remarks. Amynthas gyeongriae sp. nov. keys to the gracilis (hawayanus) group in Sims & Easton (1972). However few of these are known to have annular testes sacs enclosing the other organs of segments X and XI, and the peregrine morphs/synonyms of A. gracilis Kinberg, 1867 never have large oval male porophores. Several gracilis -group species have been recorded from Korea: A. agrestis (Goto & Hatai, 1899) , A. gibbus Hong & James, 2001 , A. serratus (Kobayashi, 1936) , A. vallis (Kobayashi, 1936) , A. palgongensis Hong, 2001 , and A. minjae Hong, 2001 . Among them, the species with simple intestinal caeca are A. serratus , A. vallis , A. palgongensis , and A. minjae .

The new species is similar to A. palgongensis from Mt. Palgong with respect to male disc shape and lack of genital markings and genital papillae, but this species differs from A. gyeongriae sp. nov. by having circular male discs with T-shaped seminal grooves, set with legs of 'T's pointed laterally. Also Amynthas gyeongriae sp. nov. has more setae between the male pores (13) than A. palgongensis (1–4).

Amynthas wonjuensis sp. nov. ( Fig. 1 E, F)

Material. Holotype: clitellate (NIBRIV0000261342); Korea, Gangwon-do Province, Wonju-si, Socho-myon, Mt. Chiak (37 14.074’N, 128° 59.151’E), 600–800 m, soil and litter layers, 9 August 2006, Y. Hong, N. J. Choi, and Y. P. Kim coll s.

Etymology. The species is named for its type locality.

Diagnosis. Spermathecal pores two pairs in 5/6–6/7, male pores superficial in XVIII on small oval-shaped white porophores lateral to large roughly circular raised genital papillae; male pores 0.15 circumference apart.

Description. Dimensions 49 mm by 3.5 mm at segment X, 3.3 mm at segment XXX, 3.5 mm at clitellum; body cylindrical, segments 69. Setae distributed regularly around segmental equators, numbering 45 at VII, 49 at XX, 6 between male pores, setal formula AA:AB:ZZ:YZ = 2:2:3:3 at XIII. Female pore single XIV on 0.4 mm oval porophore. Prostomium epilobic with tongue open, dorsal light brown, clitellum light-coffee color in formalin preservation. First dorsal pore at 12/13. Clitellum annular XIV–XVI; setae invisible externally.

Male pores superficial in XVIII on very small oval white porophores lateral to large roughly circular raised genital papillae, 0.15 circumference apart ventrally; 2.0 mm between male pores. Spermathecal pores two pairs in 5/6–6/7, 0.22 circumference apart ventrally; 2.7 mm between spermathecal pores. Genital markings lacking.

Septa 5/6–7/8 thin, 8/9/10 absent, 10/ 11/12–13/14 thinly muscular. Gizzard large in VIII–X. Intestine begins in XV, lymph glands not found. Typhlosole vestigial from XXVII. Intestinal caeca originating in XXVII and extending anteriorly about to XXIII, simple finger-shaped sacs. Esophageal hearts in X–XIII. Male sexual system holandric, testes and funnels in ventral paired sacs in X, XI. Seminal vesicles paired in XI, XII; full of transparent cysts, large without dorsal lobes. Prostates in XVIII extending from XVII–XIX, stout ducts straight to U-shaped; both glandular portions consist of 2 main lobes each divided again into 4–5 small lobes. Thick genital papillae glands attached to wall in XVIII medial to prostate ducts.

Ovaries in XIII. Spermathecae in VI and VII; ampulla small spherical, slender muscular ducts as long as ampulla, diverticulum chamber kinked or coiled longer than ampulla, stalks muscular, no nephridia on spermathecal ducts.

Remarks. Amynthas wonjuensis sp. nov. belongs to the morrisi group in Sims & Easton (1972), which is composed of 33 nominal species, more or less. Many of them have either midventral single genital markings in one or more segments (spermathecal segments and/or the male field area) or paired markings close to the midventral line (Blakemore 2006, pp. 258–259). Amynthas wonjuensis sp. nov. has no such markings. Among the morrisi group, the following species and subspecies have been reported from Korea: A. fibulus fibulus (Kobayashi, 1936) , A. fibulus ranunculus (Kobayashi, 1936) , A. kobayashii (Kobayashi, 1938) , A. koreanus (Kobayashi, 1938) , A. geojeinsulae (Song & Paik, 1970b), A. draconis Hong & James, 2001 , A. naejangensis Hong & James, 2001 , A. piagolensis Hong & James, 2001 , A. taebaekensis Hong & James, 2001 , and A. angulatus Hong, 2007 . The present species has small oval-shaped white porophores lateral to large roughly circular raised genital papillae, in which it is different from other Korean Amynthas with pads in the male field. If such pads are present, the pores are usually in seminal grooves on the pads. The pads are present in A. draconis , A . fibulus ranunculus, A . geojeinsulae, A. naejangensis and A. angulatus , and in these cases there are seminal grooves in the pads. Though A. fibulus fibulus has pads, the pores are in the center of the pads without seminal grooves. The pads are absent from A. koreanus , A. piagolensis and A. taebaekensis and the pores are not in seminal grooves, but are simple. Amynthas kobayashii has very large reniform pads with the male pores situated at the lateral margin of each pad, and no setae between the male pores.

Other morrisi group species were reported in Beddard (1892, 1895, 1896), Chen (1933, 1936, 1938, 1946), Gates (1926, 1936, 1968), Michaelsen (1892, 1923, 1927), and Rosa (1894) recorded some species in morrisi group, but all these earthworms species had different genital markings and male pore shapes.

Figures

FIGURE 1. Amynthas chiakensis sp. nov. (A, B), Amynthas gyeongriae sp. nov. (C, D), and Amynthas wonjuensis sp. nov. (E, F). A, C, E. Ventral view. B, D, F. Spermathecae. Scale bars = 5 mm (A, C, E), 2.5 mm (B, D, F).