Amynthas tortuosus
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Ordo: Opisthopora
Familia: Megascolecidae
Genus: Amynthas
Name
Amynthas tortuosus Qiu & Dong sp. nov. – Wikispecies link – ZooBank link – Pensoft Profile
Material
Holotype: 1 clitellate (C-GX201306-06A): China, Guangxi Zhuang Autonomous Region, Shiwan Mountain Nature Reserve ([http://ptp.pensoft.eu/redirect_to_googlemap.php?labels%5B0%5D=21.84739%C2%B0N%2C+107.88989%C2%B0E&coordinates%5B0%5D=21.84739%C2%B0N%2C+107.88989%C2%B0E 21.84739°N, 107.88989°E]), 553 m asl, black soil besides road, 13 May 2013, JP Qiu, Y Hong, JB Jiang, LL Zhang, Y Dong legit. Paratypes: 7 clitellates: 2 clitellates (C-GX201306-06B): same data as for holotype. 1 clitellate (C-GX201301-09): China, Guangxi Zhuang Autonomous Region, Shiwan Mountain Nature Reserve ([http://ptp.pensoft.eu/redirect_to_googlemap.php?labels%5B0%5D=21.48588%C2%B0N%2C+107.57018%C2%B0E&coordinates%5B0%5D=21.48588%C2%B0N%2C+107.57018%C2%B0E 21.48588°N, 107.57018°E]), 130 m asl, black sandy soil at riverside, 11 May 2013, JP Qiu, Y Hong, JB Jiang, LL Zhang, Y Dong legit. 4 clitellates (C-GX201305-07): China, Guangxi Zhuang Autonomous Region, Shiwan Mountain Nature Reserve (21.50396°N, 107.53350°E), 494 m asl, black sandy soil besides road, 13 May 2013, JP Qiu, Y Hong, JB Jiang, LL Zhang, Y Dong legit.
| Characteristics | A. tortuosus sp. nov. | A. carnosus | A. corticis | A. homosetus | A. exiguus aquilonius | A. stricosus |
|---|---|---|---|---|---|---|
| Body length (mm) | 55–86 | 110–340 | 45–170 | 116 | 39–63 | 72–97 |
| Body width (mm) | 2.5–2.8 | 4.0–9.0 | 3.0–6.0 | 5.2 | 1.9–2.6 | 2–2.8 |
| Pigment | ||||||
| dorsum | Purple brown before clitellum, light purple brown after | Dark brown or purple | Greenish brown | Dark chocolate on anterior, grey on other parts | Dark reddish brown | No pigment |
| ventrum | Light purple brown before clitellum, no after | Dark brown or purple | No | Grey | Light gray on ventrum | No pogment |
| First dorsal pore | 13/14 | 12/13 | 10/11 or 12/13, usually at 11/12 | 12/13 | 6/7 | 11/12 or 12/13 |
| Clitellum locality | XIV–XVI | XIV–XVI | XIV–XVI, occasionally shorter | XIV–XVI | XIV–XVI | XIV–XVI |
| Setal formula | AA=1.2-2.0AB, ZZ=1.4-2.0ZY | – | ||||
| Spermathecal pores | 4 pairs, in 5/6–8/9, 0.25C | 4 pairs in 5/6–8/9 or 3 pairs in 6/7–8/9, 0.33C | 4 pairs, 5/6–8/9, 0.33C | 4 pairs, in 5/6–8/9, 0.25C | 4 pairs, 5/6–8/9, ventral, 0.45C | 4 pairs, 5/6–8/9, 0.40C |
| Male pores | Middle, round, surrounded by 3–4 rhombic ridges, 0.25C | Round or elliptic | Small, circular to transverse elliptical di sc,0.24–0.30C | Roundish glandular area, about 1.5mm in diameter, 0.25C | Round, smooth, slightly elevated with a male aperture inconspicuous on lateral concave area, 0.23–0.30C | on a coniform glandular disc surrounded by a round pad, 0.33C |
| Papillae preclitellum | Four pairs of postsetal genital papillae in VI–IX | 8 papillae just overhead 8 spermathecal pores, 2 pairs preclitellar arranged on VIII and IX | Paired presetal and/or postsetal in some or all, near spermathecal pores | Invisible | presetal and postsetal, widely paired in 7, 8 and 9, number highly variable | Invisible |
| Papillae postclitellum | 2 presetal crescent indented-topped genital papilla medial of male pores | 2 paired presetal genital on XVIII and IX, 1 pair postsetal genital on XVIII | Present or absent, occasionally one or more near male pore | Invisible | presetal and postsetal, widely paired in XVII, XVIII and XIX, number highly variable | postsetal, single or paired in XVII, XIX and XX |
| Prostate glands | XVII–XXII | Well developed | XVII–XX, rudimentary or absent | XVI–XXI | XVI–XX, wrinkled | XVI–XX, coarsely lobate |
| Spermathecae | About 2.4mm long, ampulla slender heart-shaped; duct short | Ampulla oval or pear-shaped, duct equal to or slightly shorter than ampulla | Ampulla ovoid | – | Ampulla peach-shaped, stalk straight, much shorter than ampulla | About 1.6mm long; ampulla heart-shaped, gradually slender duct as long as ampulla |
| Diverticulum | About 2.0mm long, terminal 4/5, swollen, S-shaped twisted seminal chamber | One-third to half of ampulla, slender stalk and a wider seminal chamber | Blunt ovioid, straight stalk | Shorter, seminal chamber ovoid and whitish | Shorter, seminal chamber rudimentary or absent, straight or slightly bent | As long as main spermathecal axis, slender, terminal 0.4 dilated into a band shaped chamber |
| Accessory glands | 1 stalked accessory gland observed near the ental part of each spermatheca | – | Stalked, coelomic, bound down to parietes or retained within body wall | Invisible | round, stalked observed in spermathecal pores and male pores region | Invisible |
Diagnosis
Dimensions 55–86 mm by 2.5–2.8 mm at clitellum, 55–83 segments. First dorsal pore in 13/14. Setae numbering 24–26 at III, 34–36 at V, 34–36 at VIII, 32–36 at XX, 36–40 at XXV; 8–9 between male pores; setae between spermathecal pores numbering 9–12 at VI, 10–12 at VII, 12–13 at VIII. Four pairs of spermathecal pores in 5/6–8/9, eye-like. Four pairs of postsetal genital papillae in VI–IX, 0.20 circumference ventrally apart from each other. One pair of male pores in XVIII, each on the top of a central, round porophore surrounded by three or four rhombic ridges, with one presetal crescent indented-topped genital papilla medial of each male pore. Ampulla slender, heart-shaped; duct short. Diverticulum shorter than main pouch, terminal 4/5 slightly dilated into a swollen, S-shaped twisted seminal chamber. Prostate glands well developed.
Description
External characters: Pre-clitellum, purple-brown pigment on dorsum, light purple-brown on ventrum. Post-clitellum, light purple-brown on dorsum, no pigment on ventrum. Clitellum taupe. Dimensions 76 mm by 27 mm at clitellum. 75 segments. Prostomium ½ epilobous. First dorsal pore in 13/14. Setae numbering 24 at III, 34 at V, 36 at VIII, 36 at XX, 40 at XXV; 8 between male pores; Setae between spermathecal pores numbering 11 at VI, 10 at VII, 13 at VIII. Setae formula AA = 1.2-2.0AB, ZZ = 1.4-2.0ZY. Clitellum annular, pale taupe, in XIV–XVI, setae not visible externally. Four pairs of spermathecal pores in 5/6–8/9, eye-like, 0.25 circumference ventrally apart from each other. Four pairs of postsetal genital papillae in VI–IX, 0.20 circumference ventrally apart from each other. One pair of male pores in XVIII, 0.25 circumference apart ventrally, each on the top of a central, round porophore surrounded by three or four rhombic ridges, with one presetal crescent indented-topped genital papilla in the center of each male pore region (Figure 2A). Single female pore in XIV.
Internal characters. Septa 5/6–7/8 thick and muscular, 10/11–12/13 slightly thickened, 8/9–9/10 absent. Gizzard ball-shaped, in VIII–X. Intestine enlarged distinctly from XVI onwards. Intestinal caeca paired in XXVII, simple, smooth, extending anteriorly to XXIV. Four pairs of esophageal hearts in X–XIII, the first pair very thin, the last three pairs developed. Ovaries in XIII. Four pairs of spermathecae in VI–IX, small, 2.4 mm long. Ampulla slender, heart-shaped; duct short. Diverticulum 2.0 mm long, slightly shorter than main pouch, terminal 4/5 slightly dilated into a swollen, S-shaped twisted seminal chamber (Figure 2B). One stalked accessory gland observed medial to each spermathecal duct. Holandric: two pairs of testis sacs in X–XI, separated from each other, developed. Two pairs of seminal vesicles in XI–XII, well developed. Prostate glands well developed, inserting in XVIII and extending from XVII–XXII, coarsely lobate, prostatic duct C-shaped, uniform thickness. No accessory glands observed.
Etymology
The species is named after the crooked shape of its diverticulum.
Remarks
Amynthas tortuosus sp. nov. is a comparatively small earthworm and shares some similarities to A. carnosus and A. corticis. All of them have genital markings both on the spermathecal and the male pore regions and share similar setal numbers. However, the body size of A. tortuosus sp. nov. is very distinct from others. The new species has roughly half the body size of A. carnosus and A. corticis, both in length and width. The first dorsal pore is in 13/14 and the distance between the spermathecal pores and male pores is less than those of A. carnosus and A. corticis. Moreover, A. tortuosus sp. nov. has long diverticulum with an S-shaped twisted seminal chamber and eight stalked accessory glands observed near the spermathecal duct, rather than a straight or slender stalk and an absence of accessory glands in A. carnosus.
We also compare the new species with Amynthas homosetus (Chen 1938[1]) described from Hainan Island, which has a very similar distance between the male pores and spermathecal pores, and similar setal numbers. The differences between the two species are as follows: the body size of A. tortuosus is much smaller than A. homosetus; the size of prostate glands is larger in A. tortuosus; the shape of the seminal chamber is S-shaped twisted in A. tortuosus, while it is ovoid in A. homosetus; and several genital markings are present in the spermathecal pore region and male pore region in A. tortuosus sp. nov., while these markings are absent in A. homosetus.
The body size of A. tortuosus sp. nov. is similar to Amynthas exiguus aquilonius Tsai et al., 2001 described from Taiwan Island and Amynthas stricosus Qiu & Sun, 2012 described from Hainan Island. The first dorsal pore of the new species is in 13/14, but in 6/7 in A. exiguus aquilonius, and in 11/12 or 12/13 in A. stricosus. The new species has more closely spaced spermathecal pores than A. exiguus aquilonius and A. stricosus. Additionally, A. exiguus aquilonius has more genital papillae observed in spermathecal pores and male pores region than the new species. Accessory glands are observed in spermathecal pores and male pores region in A. exiguus aquilonius, but in the new species, accessory glands are only observed in spermathecal pores region. Furthermore, A. stricosus has a band shaped chamber, no genital papillae near spermathecal pores region, no accessory glands, and papillae observed in XVII, XIX and XX, but the new species has a S-shaped twisted seminal chamber, four pairs of genital papillae in spermathecal pores region, accessory glands near spermathecal duct, and no genital papillae observed in XVII, XIX and XX. Details of the comparison are showed in table 3.
Original Description
- Dong, Y; Law, M; Jiang, J; Qiu, J; 2019: Three new species and one subspecies of the Amynthas corticis-group from Guangxi Zhuang Autonomous Region, China (Oligochaeta, Megascolecidae) ZooKeys, 884: 23-42. doi
Images
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Other References
- ↑ Chen Y (1938) Oligochaeta from Hainan, Kwangtung.Contributions from the Biological Laboratory of the Science Society of China Zoological series12: 375–427.
