Orobdella naraharaetmagarum, Nakano, Takafumi, 2016

Nakano, Takafumi, 2016, A new quadrannulate species of Orobdella (Hirudinida, Arhynchobdellida, Orobdellidae) from western Honshu, Japan, ZooKeys 553, pp. 33-51 : 37-41

Taxon classification Animalia ORDO FAMILIA

Orobdella naraharaetmagarum sp. n. Figs 2, 3, 4, 5

Diagnosis.

Body length of mature individual less than 5 cm. Somite IV uniannulate, somites VIII–XXV quadrannulate. Male gonopore in middle of XI b6, female gonopore in middle of XIII a1, behind gastropore, gonopores separated by 1/2 + 4 + 1/2 annuli. Clitellum in XI b5 to XIII a2. Pharynx reaching to XIII b5/b6-XIII/XIV. Gastropore conspicuous, in middle of XIII a1. Gastroporal duct bulbous, slightly winding at junction with gastropore. Paired epididymides in XIV b6-XV b5 to XVIII b6-XX a2/b5, occupying 16-20 annuli (four to five somites). Atrial cornua developed, ellipsoid or ovate.

Type materials.

Holotype. KUZ Z1652, dissected, collected from under a rock along a mountain trail at Mt. Kanmuriyama, Hatsukaichi, Hiroshima Pref., Japan (34.47325°, 132.10362°; Elev. 757 m; locality number 5), by TN on 25 April 2015. Paratypes. Two specimens from near the type locality, along a forest road, "Japan National Route 488", Hatsukaichi, both dissected: KUZ Z1582, under a rock (34.50118°, 132.08933°; Elev. 790 m; locality number 5), by Yoshiko Yamane on 10 August 2014, and KUZ Z1654, under a rotten tree (34.50182°, 132.08961°; Elev. 791 m; locality number 5), by TN on 16 June 2015. For locality numbers, see Fig. 1.

Additional materials. In total four specimens were examined, all dissected. Three specimens collected from Hiroshima Pref., Japan: KUZ Z1360, from Hosomi, Kitahiroshima (34.685°, 132.292°; Elev. 470 m; locality number 4), by Yukiko Narahara on 9 July 2011; KUZ Z1380, from Mt. Azumayama, Hiwacho, Shobara (35.0639°, 133.0268°; Elev. 1010 m; locality number 2), by Ayane Maga on 3 October 2011; and KUZ Z1655, from under a rock along a mountain trail at Mt. Izaiyama, Hiwacho-Mitsugaichi, Shobara (35.00143°, 133.04640°; Elev. 906 m; locality number 3), by TN on 17 June 2015. KUZ Z1535, collected from under a rock along a mountain trail at Mt. Iimoriyama, Noigura, Kotoura, Tottori Pref., Japan (35.37603°, 133.59953°; Elev. 619 m; locality number 1), by TN on 11 December 2013. For locality numbers, see Fig. 1.

Etymology.

The specific name is a noun in the genitive case formed directly from the names of Ms Yukiko Narahara and Ms Ayane Maga, who collected specimens of this new species. Its stem is determined as “naraharaetmag” herein.

Description of holotype.

Body firm and muscular, elongate, with constant width in caudal direction, dorsoventrally compressed, BL 40.0 mm, BW 5.3 mm (Fig. 2). Caudal sucker ventral, elliptic, CL 2.4 mm, CW 3.0 mm (Figs 2B, 3D).

Somite I completely merged with prostomium (Fig. 3A). Somites II–IV uniannulate, II not separate from I (Fig. 3A). Somite V biannulate, (a1 + a2)> a3; a3 forming posterior margin of oral sucker (Fig. 3A, B). Somites VI and VII triannulate, a 1 = a2 = a3 (Fig. 3A, B). Somites VIII–XXV quadrannulate, a1 = a2 = b5 = b6 (Fig. 3 A–E). Somite XXVI dorsally triannulate, a1> a2 <a3, a3 with slight furrow; ventrally biannulate, (a1 + a2)> a3, (a1 + a2) with slight furrow; (a1 + a2) being ventrally last complete annulus (Fig. 3C, D). Somite XXVII uniannulate with slight dorsal furrow; anus behind it with no post-anal annulus (Fig. 3C).

Male gonopore in middle of XI b6 (Fig. 3E). Female gonopore slightly anterior to middle of XIII a1, inconspicuous, located posterior to gastropore (Fig. 3E, F). Gonopores separated by 1/2 + 4 + 1/2 annuli (Fig. 3E).

Anterior ganglionic mass in VI a2 and a3. Ganglion VII in a2. Ganglia VIII–X, of each somite, in a2. Ganglia XI and XII, of each somite, in a2 (Fig. 4A). Ganglion XIII in a2 and b5 (Fig. 4A). Ganglion XIV in a2 (Fig. 4A). Ganglia XV–XX, of each somite, in a1 and a2 (Fig. 4A). Ganglia XXI–XXIII, of each somite, in a2. Ganglion XXIV in a1. Ganglion XXV in b6 of XXIV and a1 of XXV. Ganglion XXVI in b5 and b6 of XXV. Posterior ganglionic mass in (a1 + a2) of XXVI.

Eyes in three pairs, first pair dorsally on posterior margin of II, second and third pairs dorsolaterally on posterior margin of V (a1 + a2) (Fig. 3A). Papillae numerous, minute, hardly visible, one row on every annulus.

Nephridiopores in 17 pairs, one each situated ventrally at posterior margin of a1 of each somite in VIII–XXIV (Fig. 3B, D, E).

Pharynx agnathous, euthylaematous, reaching to XIII b5/b6 (Fig. 3G). Crop tubular, acecate, reaching to XIX b5/b6. Gastropore conspicuous, ventral, slightly anterior to middle of XIII a1 (Fig. 3E, F). Gastroporal duct bulbous, slightly winding at junction with gastropore, joining with crop in XIV a1 (Fig. 3G). Intestine tubular, acecate, reaching to XXIV a1. Rectum tubular, thin-walled, straight.

Testisacs multiple (Fig. 4A); on right side, in XVIII b6 to XXIV a2, in total app. 28 testisacs, 1 in XVIII, 3 in XIX, 5 in XX, 4 in XXI, 6 in XXII, 7 in XXIII, 2 in XXIV; on left side, in XIX a1 to XXV a2, in total app. 27 testisacs, 5 in XIX, 6 in XX, 4 in XXI, 4 in XXII, 4 in XXIII, 3 in XXIV, 1 in XXV. Paired epididymides; right epididymis in XIV b6 to XVIII b6, occupying 17 annuli; left epididymis in XIV/XV to XVIII b6, occupying 16 annuli (Fig. 4A). Ejaculatory bulbs absent. Paired ejaculatory ducts; right duct in XI a2/b5 to XIV b6; left duct in XI a2/b5 to XIV/XV; coiled in position posterior to ovisacs; each duct crossing ventrally beneath each ovisac, then curved in position anterior to ovisacs; each widening from respective junction with epididymis, narrowing at junction with atrial cornua, then turning sharply inward toward atrial cornua without pre-atrial loop (Fig. 4A). Pair of muscular atrial cornua ellipsoid, in XI b5 and b6 (Fig. 4 A–D). Atrium short, muscular, globular in XI b5 and b6 (Fig. 4 B–D). Penis sheath and penis absent.

Paired ovisacs globular; right ovisac in XIII a2 and b5; left ovisac in XIII a1 and a2 (Fig. 4A, E). Oviducts, thin-walled, left oviduct crossing ventrally beneath nerve cord; both oviducts converging into common oviduct in XIII a2 (Fig. 4A, E). Common oviduct thin-walled, short, directly descending to female gonopore (Fig. 4E).

Variations.

BL 48.2 (KUZ Z1654)-33.0 (KUZ Z1360) mm, BW 4.4 (KUZ Z1535)-2.7 (KUZ Z1380) mm, CL 2.5 (KUZ Z1654)-1.2 (KUZ Z1380) mm, CW 3.0 (KUZ Z1654)-1.8 (KUZ Z1360, Z1380) mm. Somite XXVI triannulate, a1 = a2 <a3 (KUZ Z1380, Z1582); KUZ Z1360, Z1535, Z1654, Z1655, a3 with slight dorsal furrow. Somite XXVII uniannulate or biannulate (KUZ Z1360). Male gonopore generally in middle of XI b6, rarely slightly anterior or posterior to middle of XI b6. Female gonopore in middle of XIII a1, slightly anterior or posterior to middle of XIII a1. X b5 and XIII a2, respectively, being first and last annuli of clitellum. Eyes generally three pairs; KUZ Z1654, Z1655, first pair dorsally on anterior margin of III; KUZ Z1582, multiple eyes detected, one eye on left dorsal of II/III, one small eyespot on right dorsal of III, one small eyespot on left dorsal of III/IV, one small eyespot on right dorsal of IV, and two pairs of eyes dorsolaterally on posterior margin of V (a1 + a2). Pharynx reaching to XIII b5/b6-XIII/XIV. Crop reaching to XIX b5/b6-XX a1. Gastropore in middle of XIII a1, slightly anterior or posterior to middle of XIII a1. Gastroporal duct generally bulbous; KUZ Z1360, Z1582, tubular. Intestine reaching to XXIII/ XXIV–XXIV /XXV. Testisacs multiple; right side app. 11-24 sacs in XIX b6-XX b5 to XXIV b5-b6; left side app. 11-23 sacs in XIX b6-XX a2 to XXIII b6-XXV a1. Paired epididymides; right epididymis in XV a1-XV b5 to XIX a2-XX a2/b5, occupying 17-20 annuli; left epididymis in XV a1-XV b5 to XIX b5-XX a2, occupying 17-20 annuli. Paired ejaculatory ducts, curved, loosely curved, or straight in position posterior to ovisacs. Atrial cornua ovate, fusiform, or ellipsoid in XI b5 and b6; KUZ Z1535 in XI b5-XII a. Atrium generally in XI b5 and b6; KUZ Z1535, Z1582 in XI b6. Paired ovisacs generally in XIII a2 and b5; KUZ Z1535, undeveloped, in XIII a2. Right or left oviduct crossing ventrally beneath nerve cord; KUZ Z1380 both oviducts converging into common oviduct in XIII a1/a2.

Coloration.

In life, dorsal surface bluish gray (Fig. 5A, B), or gray; ventral surface reddish white or ash gray; clitellum, when obvious, whitish gray (Fig. 5B). Color faded in preservative; KUZ Z1535 with one dorsal black line from VIII b5 to XXVI a2.

Distribution.

This species was primarily collected in Hiroshima Prefecture in Chugoku District, Honshu, Japan, and in Tottori Prefecture. The lowest elevation among the localities was 470 m, and the highest was 1010 m. The locality data for this species suggested that it is distributed in mountainous regions in Chugoku District, Honshu, Japan.

Natural history.

This species was generally found curled up under rocks or rotten trees in moist mountainous habitats (Fig. 5 C, D). Oligochaete worms were sometimes observed in the digestive tract during specimen dissection. Therefore, this species is an earthworm-eater, as are the other known Orobdella leeches.

A mature leech with an obvious clitellum was collected on 16 June. Moreover, the holotype, which appeared to have a clitellum (Fig. 5A), was collected on 25 April. These findings suggest that the reproductive season of the new species begins in May and then continues at least to mid-to-late June.

Remarks.

The new species unambiguously belongs to Orobdella as it has all the generic diagnostic characteristics defined in Nakano et al. (2012): post-anal annulus absent; pharynx agnathous, euthylaematous; gastropore in XIII; gastroporal duct lying on female organ; gonopores separated by more than one full somite; testisacs multiple; male atrium in XI without penis sheath and penis; ovisacs globular in XIII; female median reproductive system essentially lacking.

The specimens were small (up to 48 mm). However, one leech (KUZ Z1654) was determined to be mature because it possessed an obvious clitellum. The holotype, which had a body length of 40 mm, also possessed a slightly developed clitellum and developed testisacs. Two specimens (KUZ Z1360, Z1582) possessed a tubular gastroporal duct. This tubular gastroporal duct was thought to be observed in immature individuals because these two specimens had undeveloped, undetectable testisacs.

Taxonomic studies ( Nakano 2010, 2012b, 2014, Nakano and Gongalsky 2014, Nakano and Lai 2012, Nakano and Seo 2014) indicate that the new species differs from the seven other quadrannulate species (i.e., Orobdella esulcata , Orobdella kawakatsuorum Richardson, 1975, Orobdella ketagalan Nakano & Lai, 2012, Orobdella koikei , Orobdella masaakikuroiwai , Orobdella tsushimensis Nakano, 2011a, and Orobdella whitmani Oka, 1895) by the following combination of characteristics (Table 2): body length less than 5 cm, IV uniannulate, gonopores separated by 1/2 + 4 + 1/2 annuli, XXV quadrannulate, gastroporal duct bulbous, epididymides in XIV to XX, atrial cornua developed, ellipsoid or ovate. Among the above seven quadrannulate species, two species, Orobdella koikei and Orobdella masaakikuroiwai , are known to have body lengths shorter than 5 cm. Orobdella naraharaetmagarum can be distinguished from these two species by the annulation of XXV and the length of the epididymides.

The new species is distinguishable from the four sexannulate species Orobdella dolichopharynx Nakano, 2011b, Orobdella ijimai Oka, 1895, Orobdella mononoke Nakano, 2012a, and Orobdella shimadae Nakano, 2011b and the octannulate species Orobdella octonaria Oka, 1895, since Orobdella naraharaetmagarum possesses mid-body somites that are quadrannulate.