Orobdella okanoi, Nakano, Takafumi, 2016

Nakano, Takafumi, 2016, Four new species of the genus Orobdella from Shikoku and Awajishima island, Japan (Hirudinida, Arhynchobdellida, Orobdellidae), Zoosystematics and Evolution 91 (1), pp. 79-102 : 85-86

Taxon classification Animalia Arhynchobdellida Orobdellidae

Orobdella okanoi sp. n. Figs 10, 11, 12, 13

Type material.

Holotype: KUZ Z1671, dissected, collected from under a rock along a mountain trail at Mt. Kuishiyama (33.67636°N, 133.51556°E; Elev. ca. 910 m; locality #3, see Fig. 1), Kochi, Kochi Prefecture, Japan, by Yoshiko Yamane on 5 July 2015.

Additional material.

KUZ Z1491, dissected, collected from in soil along a road at Mt. Iwagurosan (33.755278°N, 133.148333°E; Elev. ca 1510 m; locality #5, see Fig. 1), Saijyo, Ehime Prefecture, Japan, by Yoshiko Yamane on 22 August 2013.

Type locality.

Japan, Kochi Prefecture: Kochi, Tosayamatakakawa, Mt. Kuishiyama (Shikoku).

Diagnosis.

Dorsal surface reddish. Somite VII quinquannulate. Somite VIII–XXVI sexannulate. Male gonopore in slightly posterior to middle of XI c11/c12, female gonopore in middle of XIII b2, behind gastropore, gonopores separated by 8 + 1/2 annuli. Pharynx reaching to XIV b1-b2/a2. Gastropore conspicuous, in middle of XIII b2. Gastroporal duct bulbous, slightly winding at junction with gastropore. Paired epididymides in XV to XVII, occupying 8-11 annuli (one and half to almost two somites). Pre-atrial loop absent. Atrial cornua ellipsoid.

Description of holotype.

BL 95.2 mm, BW 5.8 mm (Fig. 10). Caudal sucker ventral, elliptic, CL 2.3 mm, CW 3.7 mm (Figs 10B, 11D).

Somite III uniannulate (Fig. 11A). Somites IV and V biannulate; IV, (a1 + a2)> a3 (Fig. 11A); V, (a1 + a2) = a3; V a3 forming posterior margin of oral sucker (Fig. 11A, B). Somite VI triannulate, a1 (dorsally b1 = b2)> a2 = a3 (Fig. 11A, B). Somite VII quinquannulate, b1 = b2 = a2 = b5 = b6 (Fig. 11A, B). Somites VIII–XXVI sexannulate, b1 = b2 = a2 = b5 = c11 = c12 (Fig. 11 A–E). Somite XXVII comprises two annuli; first annulus being ventrally last complete annulus (Fig. 11C, D). Anus behind somite XXVII (Fig. 11C).

Male gonopore in XI c11/c12 (Fig. 11E). Female gonopore in slight posterior to middle of XIII b2, inconspicuous, located posterior to gastropore (Fig. 11E, F). Gonopores separated by 8 + 1/2 annuli (Fig. 11E).

Anterior ganglionic mass in VI a1 and VII b1. Ganglion VII in b2 and a2. Ganglion VIII in a2. Ganglion IX in a2 and b5. Ganglion X in a2. Ganglion XI in a2 and b5 (Fig. 12A). Ganglion XII in a2 (Fig. 12A). Ganglion XIII in a2 and b5 (Fig. 12A). Ganglia XIV and XV, of each somite, in a2 (Fig. 12A). Ganglion XVI in b2 and a2 (Fig. 12A). Ganglia XVII (Fig. 12A) and XVIII, of each somite, in a2. Ganglion XIX in b2 and a2. Ganglia XX–XXII, of each somite, in a2. Ganglia XXIII–XXV, of each somite, in b2 and a2. Ganglion XXVI in b1 and b2. Posterior ganglionic mass in XXVI b5-c12.

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. 11A).

Nephridiopore in 17 pairs, one each situated ventrally at posterior margin of b2 of each somite in VIII–XXIV (Fig. 11B, D, E).

Pharynx reaching to XIV b1 (Fig. 11G). Crop reaching to XXII b1. Gastropore conspicuous, ventral, in slightly posterior to middle of XIII b2 (Fig. 11E, F). Gastroporal duct bulbous, slightly winding at junction with gastropore, joining with crop in XIV b1 (Fig. 11G). Intestine reaching to XXV b5/c11.

Testisacs (Fig. 12A); on right side, in XVII b5 to XXV c12, in total approx. 94 testisacs, 5 in XVII, 13 in XVIII, 12 in XIX, 13 in XX, 11 in XXI, 12 in XXII, 10 in XXIII, 10 in XXIV, 8 in XXV; on left side, in XVII c11 to XXIV c12, in total approx. 86 testisacs, 3 in XVII, 15 in XVIII, 11 in XIX, 13 in XX, 13 in XXI, 10 in XXII, 11 in XXIII, 10 in XXIV. Paired epididymides; right epididymis in XV c11/c12 to XVII b2, occupying 9 annuli; left epididymis in XV c11/c12 to XVII b1/b2, occupying 8 annuli (Fig. 12A). Paired ejaculatory ducts in XI b5 to XV c11/c12; slightly coiled in position posterior to ovisacs; each duct crossing ventrally beneath each ovisac, then loosely 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. 12 A–D). Pair of muscular atrial cornua ellipsoid, in XI b5-c12 (Fig. 12 A–D). Atrium short, muscular, globular in XI c11 and c12 (Fig. 12 A–D).

Paired ovisacs; right ovisac in XIII a2 and b5; left ovisac in XIII a2-c11 (Fig. 12A, E). Oviducts; left oviduct crossing ventrally beneath nerve cord; both oviducts converging into common oviduct in XIII a2 (Fig. 12A, E). Common oviduct directly descending to female gonopore (Fig. 12E).

Variation.

BL 143.2 mm, BW 7.6 mm, CL 3.1 mm, CW 4.0 mm. Somite III uniannulate with slight dorsal furrow. Somite XXVII comprises two annuli, each annulus with slight dorsal furrow. Male gonopore in posterior margin of XI c11. Female gonopore in middle of XIII b2. Eyes in three pairs, firs pair dorsally on anterior margin of III. Pharynx reaching to XIV b2/a2. Crop reaching to XXII a2. Gastropore in middle of XIII b2. Gastroporal duct joining with crop in XIV b2. Intestine reaching to XXIV c12. Testisacs; on right side, in XVII b2 to XXI b5, in total approx. 64 testisacs, 8 in XVII 13 in XVIII, 18 in XIX, 17 in XX, 8 in XXI; on left side, in XVII b2 to XXIV c11, in total approx. 99 testisacs, 7 in XVII, 10 in XVIII, 17 in XIX 17 in XX, 15 in XXI, 13 in XXII, 11 in XXIII, 9 in XXIV. Paired epididymides; right epididymis in XV a2 to XVI/XVII, occupying 10 annuli; left epididymis in XV a2 to XVII b1, occupying 11 annuli. Paired ejaculatory ducts curved in position anterior to ovisacs. Paired atrial cornua; right cornu in XI c12 and XII b1; left cornu in XI b5 and c11. Paired ovisacs in XIII a2 and b5.

Colouration.

In life, dorsal surface red-purple (Fig. 13) or pinkish gray; ventral surface grayish red-purple or whitish red. Color faded in preservative; dark line present from VI a1 (b2) to XIV b5 in KUZ Z1491.

Etymology.

The specific name is a noun in the genitive case formed directly from the name of Mr Ryosuke Okano, who collected valuable specimens of Orobdella leeches.

Distribution.

The type locality of this species is located in the central region of Shikoku, Japan. In addition, this species was collected from the Ishizuchi Mountains. According to the collection localities, this species is considered to inhabit the central mountainous region of Shikoku.

Natural history.

This species was found curled up under a rock or in soil in moist mountainous habitats. Oligochaete worms were found in the digestive tract of the holotype, and thus this species is an earthworm-eater. The reproductive season of Orobdella okanoi remains unclear because no individuals of this species with a clitellum have been collected.

Remarks.

According to taxonomic studies on sexannulate Orobdella species ( Nakano 2011b, 2012a), Orobdella okanoi differs from the four known sexannulate species, Orobdella dolichopharynx Nakano, 2011b, Orobdella ijimai Oka, 1895, Orobdella mononoke Nakano, 2012a and Orobdella shimadae Nakano, 2011b, as well as the new sexannulate species described below in having the following characteristics (Table 4): dorsal surface reddish, somite VII quinquannulate, somite VIII sexannulate, 8 + 1/2 annuli between gonopores, pharynx reaching to XIV, gastroporal duct bulbous, epididymides in XV to XVII, pre-atrial loop absent and atrial cornua ellipsoid. Orobdella okanoi is clearly distinguished from quadrannulate and octannulate species in having sexannulate mid-body somites.

The right atrial cornu of one specimen, KUZ Z1491, is caudad. Because its right side testisacs only reach somite XXI, the right side of its male genital organ may be a result of abnormal development.