Amynthas shinanmontis Tsai and Shen, 2007

Tsai, Chu-Fa, Shen, Huei-Ping, Tsai, Su-Chen & Lee, Hsun-Huang, 2007, Four new species of terrestrial earthworms belonging to the genus Amynthas (Megascolecidae: Oligochaeta) from Taiwan with discussion on speculative synonyms and species delimitation in oligochaete taxonomy, Journal of Natural History 41 (5 - 8), pp. 357-379 : 358-362

Amynthas shinanmontis Tsai and Shen , sp. nov.

( Figure 1 )

Type material

Holotype: a clitellate (mature) specimen (dissected) collected 16 June 1999 at Mt Shinan (elevation 2000 m) along Shihshan Forest Road in natural forest near the Middle Altitude Experimental Station , Taiwan Endemic Species Research Institute, Kaohsiung County by C. F. Tsai, S. C. Tsai, R. C. Jang, and S. T. Chang (coll. no. 1999-2-Shen) . Paratypes: two clitellates (dissected) collected 25 October 2000 at the same mountain road (elevation 1700 m) where holotype was collected by H. P. Shen, S. T. Chang, H. P. Yang, and C. Y. Chang (coll. no. 2000-75-Shen) .

Other material

Seven clitellates (three dissected) and 11 aclitellates collected 15 March 2000 along Rt 20 (elevation 2500 m) near Kuaigu , Kaohsiung County by C. F. Tsai, S. C. Tsai, H. S. Fang, H. P. Shen, S. T. Chang, H. P. Yang, and T. J. Lin (coll. no. 2000-19-Shen); seven clitellates (two dissected) collected 15 March 2000 along Rt 20 near Takuanshan Tunnel (elevation 2700 m) in Kaohsiung County near the border with Taitung County by C. F. Tsai, S. C. Tsai, H. S. Fang, H. P. Shen, S. T. Chang, H. P. Yang, and T. J. Lin (coll. no. 2000-20-Shen); five clitellates (two dissected) collected 15 March 2000 from Yakou, Taitung County (elevation 2700 m) by C. F. Tsai, S. C. Tsai, H. S. Fang, H. P. Shen, S. T. Chang, H. P. Yang, and T. J. Lin (coll. no. 2000-21-Shen); four clitellates (all dissected) and two aclitellates collected 15 March 2000 from Hsiangyang (elevation 2100–2300 m), Taitung County by C. F. Tsai, S. C. Tsai, H. S. Fang, H. P. Shen, S. T. Chang, H. P. Yang, and T. J. Lin (coll. no. 2000-22-Shen); four clitellates (one dissected) collected 25 October 2000 along Shihshan Forest Road in natural forest (elevation 2100 m) near the Middle Altitude Experimental Station , Taiwan Endemic Species Research Institute, Kaohsiung County by H. P. Shen, S. T. Chang, H. P. Yang, and C. Y. Chang (coll. no. 2000-72-Shen); 13 clitellates (five dissected) and seven aclitellates collected 26 October 2000 along a forest road in the Chuyunshan Nature Reserve (elevation 2150 m) in Kaohsiung County near the border with Taitung County by H. P. Shen, S. T. Chang, H. P. Yang, and C. Y. Chang (coll. no. 2000-77-Shen); four clitellates collected 26 October 2000 along a forest road in the Chuyunshan Nature Reserve (elevation 1850 m) in Kaohsiung County near the border with Taitung County by H. P. Shen, S. T. Chang, H. P. Yang, and C. Y. Chang (coll. no. 2000-78-Shen) .

Diagnosis

Medium earthworm; length (clitellates) 86–187 mm, segments numbering 75–114. Setae 31–43 in VII, 38–55 in XX, 6–11 between male pores. Spermathecal pores invisible. Male pores 0.20–0.28 body circumferences ventrally apart; each on an oval or round papilla-like or disc-like porophore, surrounded by three to five skin folds, often with a horizontal groove anteriorly, so that it looks like an eye. Spermathecae three pairs to absent; normal (large) size to nodule. Prostate glands paired and normal size to absent. Seminal vesicles two pairs, normal size to nodule. Genital papillae and accessory glands absent. Parthenogenetic.

External characters

Total length (clitellates) 86–187 mm. Clitellum length 1.74–5.27 mm and width 2.53– 5.19 mm. Prostomium epilobous. Segments numbering 75–114. Setae minute, 31–43 in VII, 38–55 in XX, and 6–11 between male pores in XVIII. First dorsal pore in 11/12–13/ 14. Spermathecal pores invisible externally. Female pore single, medio-ventral in XIV.

Male pores paired in XVIII, ventro-lateral, 0.20–0.28 body circumferences ventrally apart; each on an oval or round papilla-like or disc-like porophore, surrounded by three to five oval skin folds, often with a horizontal groove anteriorly, so that it looks like an eye ( Figure 1A ). Genital papillae absent in both preclitellar and postclitellar regions. Preserved specimens greyish brown on head and dorsum, dark grey on mid-dorsum, and light brown on ventrum. Clitellum light to dark grey in colour.

Internal characters

Septa 5/6–7/8 and 10/11–13/14 thickened, 8/9/10 missing. Nephridial tufts thick, on anterior faces of 5/6/7 septa. Gizzard large in IX–X. Oesophageal hearts enlarged in XI– XIII. Intestine starting enlarged in XV or XVI. Intestinal caeca paired in XXVII, simple, slender, extending anteriorly to XXII–XXV.

Spermathecae varied in number from three pairs (sexthecate) to absent (athecate). For 20 clitellate specimens dissected, three pairs in VI – VIII for four specimens and one of them with degenerated spermathecae in VIII ( Figure 1B ); three spermathecae on one side in VI – VIII and a single one on the other side in VI or VII for three specimens; two in each of VI, VII and VII, VIII for one specimen; one pair in VI for one specimen; single one in VII for one specimen; and completely absent for 10 specimens ( Table I). Sizes and structure of spermathecae also varied from large (normal), vestigial, nodule to absent: large spermatheca with a peach-shaped ampulla with a very short, stout stalk or almost no stalk, and a diverticulum with a small, ovalshaped seminal chamber and a slender stalk ( Figure 1B ); vestigial spermatheca with a small degenerated ampulla and stalk, and no diverticulum; nodule-like spermatheca with a small, degenerated ampulla without stalk and no diverticulum .

Holandry: testis sacs small, two pairs in X and XI or both in XI. Vas efferens connected in XII or XIII in each side to form a large, straight vas deferens and then to prostatic duct in XVIII. Seminal vesicles two pairs in XI and XII, variable in size: large (normal) seminal vesicle with pink, follicular surface, and a small, reddish brown dorsal lobe, occupying an entire segmental compartment ( Figure 1C ); medium vesicle with highly folliculated surface and a large dorsal lobe, occupying about half of the segmental compartment ( Figure 1D ); vestigial vesicle and its dorsal lobe highly folliculated, occupying less than half of the compartment; and nodule-like vesicle, a small, irregular nodule without dorsal lobe. For 20 specimens dissected, large seminal vesicles for 12 specimens, medium for two specimens, vestigial for five specimens, and one specimen with large seminal vesicles on one side and medium on the other side ( Table I).

Prostate glands also variable in size from normal to absent (aprostatic) ( Table I): normal in XVI–XVIII for two specimens ( Figure 1E ), vestigial only in XVIII or XVII to XVIII for three specimens ( Figure 1F ), nodule-like for 12 specimens ( Figure 1G ), and absent for three specimens ( Figure 1H ). Prostatic duct thick, swollen, U-shaped or coiled ( Figure 1E– H ). One of the aprostatic paratypes has no left prostatic duct and left male porophore. Accessory glands absent in both preclitellar and postclitellar regions.

Etymology

The name shinanmontis is given to this species with reference to its type locality (elevation 2000 m) at Mt Shinan in southern Taiwan .

Remarks

Amynthas shinanmontis sp. nov. is a parthenogenetic earthworm, consisting of individuals that have a continuous spectrum in degeneration of spermathecae and male reproductive organs (prostate glands, prostatic ducts, and seminal vesicles) ( Table I). Most of the specimens examined have certain levels of degeneration of at least one of the organs. It is reasonable to consider that the specimens of A. shinanmontis studied are I 4 morph, an intermediate between Hp morph (with full reproductive organs but parthenogenetic) to ARZ morph (athecate, anarsenosomphic, and lacking all male reproductive organs) ( Gates 1956, 1972). The rates of the degeneration vary among organs and also among individuals. Some of the individuals degenerated to or over A morph (athecate), R morph (aprostatic and no male terminalia), or AR morph (athecate and no male terminalia), but none reached ARZ morph. Generally, the rate of degeneration is faster for spermathecae (10 of 20 specimens, athecate) than that of prostate glands (three specimens, aprostatic). Seminal vesicles have the slowest rate of degeneration (all specimens with seminal vesicles). For spermathecae, the degeneration is faster for those in VIII than VII and VI, and those in VI are the final ones to be lost.

When all ancestral forms of spermathecae and male reproductive organs ( Table I) are considered, it is reasonable to hypothesize that H morph (hermaphroditic bisexual form) is sexthecate earthworm with spermathecae in VI, VII, and VIII, belonging to the gracilis (5 hawayanus) species-group of the genus Amynthas ( Sims and Easton, 1972) . However, which known species the H morph belongs to is unknown. Amynthas shinanmontis somewhat resembles A. gracilis ( Kinberg, 1867) , but they are easily distinguishable by genital papillae at the male pores: absent in A. shinanmontis , and one to several postsetal papillae arranged in one or two oblique rows medial to each of the male pores in A. gracilis . Also, the former is endemic while the latter is peregrine. According to Gates (1972), when the ancestral H morph is unknown, all parthenogenetic morphs that can be similarly linked (affiliated) together by intermediates (continuous changes) are considered as one species. For species delimitation of parthenogenetic morphs, see the discussion section.

Figures

Figure 1. Amynthas shinanmontis sp. nov. (A) Ventral view of right male pore region (p, male porophore); (B) dorsal view of spermathecae of a 110-mm specimen (coll. no. 2000-77-Shen) (amp, ampulla; dv, diverticulum); (C) dorso-lateral view of right testis sacs (ts) and seminal vesicles (sv) of a 178-mm specimen (coll. no. 2000-21- Shen) (dl, dorsal lobe; vd, vas deferens; ve, vas efferens); (D) dorso-lateral view of right testis sacs and seminal vesicles of holotype; (E) large prostate gland (pg) of a 106-mm specimen (coll. no. 2000-77-Shen) (pd, prostatic duct); (F) vestigial prostate gland of a 178-mm specimen (coll. no. 2000-21-Shen); (G) nodule-like prostate gland of a 110-mm specimen (coll. no. 2000-77-Shen); (H) prostate gland absent for a 122-mm specimen (coll. no. 2000-21-Shen).