Orobdella koikei, Nakano, Takafumi, 2012

Nakano, Takafumi, 2012, A new species of Orobdella (Hirudinida, Arhynchobdellida, Gastrostomobdellidae) and redescription of Orobdella kawakatsuorum from Hokkaido, Japan with the phylogenetic position of the new species, ZooKeys 169, pp. 9-30 : 12-16

Orobdella koikei sp. n. Figs 2-5

Diagnosis.

In life, dorsal surface brown. Somites III and IV uniannulate, somites VIII–XXIV quadrannulate, somites XXV and XXVI triannulate. Pharynx reaching to XIV. Gastropore conspicuous at XIII a1 (slightly posterior to middle of annulus). Gastroporal duct, tubular, but bulbous at junction with gastropore and at junction with crop. Male gonopore at XI b6, female gonopore at XIII a1 (slightly posterior to middle of annulus), gonopores separated by 1/2 + 4 + 1/2. Paired epididymides in XVI/ XVII–XVII a2 to XIX a2/b5. Atrial cornua ovate.

Type materials.

KUZ Z156, holotype, dissected, collected from under a rock along a mountain trail at Sounkyo, Kamikawa, Hokkaido, Japan (43°43.36'N, 142°56.85'E; Alt. 712 m), by Naoki Koike on 17 August, 2010.

Five paratypes collected from Hokkaido, Japan. Two specimens from the type locality (43°43.36'N, 142°56.85'E; Alt. 712 m): KUZ Z157, dissected, by Naoki Koike on 17 August, 2010, and KUZ Z186, by TN on 19 September, 2011. KUZ Z145, dissected, from Hiratori (42°40.82'N, 142°25.44'E; Alt. 220 m), by Naoki Koike on 2 August, 2010. KUZ Z146, dissected, from Mt. Pisenaiyama, Shinhidaka (42°42.86'N, 142°38.30'E; Alt. 981 m), by Naoki Koike on 3 August, 2010. KUZ Z158, dissected, from Mt. Shokanbetsudake, Mashike (43°46.23'N, 141°30.63'E; Alt. 288 m), by Naoki Koike on 18 August, 2010.

Etymology.

The specific name is a noun in the genitive case formed directly from the name of Mr Naoki Koike, who collected many valuable specimens of Orobdella leeches from Hokkaido.

Description of holotype.

Body firm, muscular, elongated, gaining regularly in width in caudal direction, dorso-ventral depressed, sides nearly parallel from mid length to point just anterior to caudal sucker, BL 30.5 mm, BW 2.5 mm (Fig. 2). Caudal sucker ventral, oval, its diameter smaller than BW (Figs 2B, 3D). In life, dorsal surface brown, ventral surface grayish white. Color faded in preservative, without any dark lines (Fig. 2)

Somite I completely merged with prostomium (Fig. 3A). Somites II–IV uniannulate (Fig. 3A). Somite V biannulate, (a1+a2) = a3 (Fig. 3A), V a3 forming posterior margin of oral sucker (Fig. 3B). Somites VI and VII triannulate (Fig. 3 A–B). Somites VIII–XXIV quadrannulate, a1 = a2 = b5 = b6 (Fig. 3 A–B, E). Somites XXV and XXVI triannulate (Fig. 3 C–D), XXVI a3 being last complete annulus on venter (Fig. 3D). Somite XXVII uniannulate with one slight furrow on dorsal; anus behind it with no post-anal annulus (Fig. 3C).

Anterior ganglionic mass in VI a2 and a3. Ganglion VII in a2. Ganglion VIII in a2 and b5. Ganglion IX in a2. Ganglia X–XII in a2 and b5 of each somite (Fig. 4A). Ganglion XIII in b5 (Fig. 4A). Ganglia XIV and XV in a2 and b5 of each somite (Fig. 4A). Ganglia XVI–XXI in a2 of each somite (Fig. 4A). Ganglia XXII–XXIV in a1 and a2 of each somite. Ganglia XXV and XXVI in a1 of each somite. Posterior ganglionic mass in XXVII a2 and a3.

Eyes two pairs, first pair dorsally on posterior margin of II, second pair dorsolaterally on middle of V (a1 + a2) (Fig. 3A). Nephridiopores in 17 pairs, ventrally at posterior margin of a1 of each somite of VIII–XXIV (Fig. 3A, E). Papillae numerous, minute, hardly visible, one row on every annulus.

Pharynx agnathous, euthylaematous, reaching to XIII/XIV (Fig. 3F). Crop tubular, acaecate, in XIII/XIV to XIX b5/b6. Gastropore conspicuous, ventral, located slightly posterior to middle of XIII a2 (Fig. 3E, G). Gastroporal duct, winding and bulbous at junction with gastropore, tubular but bulbous at junction with crop, joining with crop in XIV a1 (Fig. 3F). Intestine tubular, acaecate, in XIX b5/b6 to XXIII a2. Rectum, tubular, thin-walled.

Male gonopore at middle of XI b6 (Fig. 3E). Female gonopore located slightly posterior to middle of XIII a2, inconspicuous, located behind gastropore (Fig. 3G). Gonopores separated by 1/2 + 4 + 1/2 annuli (Fig. 3E). Testisacs multiple, one or two testisacs on each side in each annulus, in XIX a2/b5 to XXIV a1 (Fig. 4A). Paired epididymides in XVI a2/b5 to XIX a2/b5 (Fig. 4A). Ejaculatory bulbs absent. Ejaculatory ducts in XI a2/b5 to XVI a2/b5, loosely coiled, each winding from each junction with epididymis, narrowing at junction with atrial cornu, then turning sharply inward toward atrial cornu without pre-atrial loop (Fig. 4 A–D). Pair of atrial cornua in XI b5 and b6, muscular, ovate (Fig. 4B). Atrium short, muscular, globular in XI b6 (Fig. 4 B–D). Penis sheath and penis absent. Ovisacs one pair, thin-walled, globular, in XIII a2 and b5 (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 ascending to female gonopore (Fig. 4E).

Variation.

In life, color generally same as holotype (Fig. 5). Somite III with slight furrow on dorsal (KUZ Z146). Somite IV with slight furrow on dorsal (KUZ Z158), or biannulate (KUZ Z146). Somite XXVI incomplete triannulate. Pharynx reaching to XIII b5/b6-XIV a1. Crop reaching to XIX b5-XX a1. Gastropore at middle of XIII. Gastroporal duct simple tubular (KUZ Z145 and Z146). Intestine reaching to XXIII a1-XXIV a2. Female gonopore at middle of XIII. Testisacs in XVIII a1-XIX a2/b5 to XXIII a2/b5. Epididymides in XVI/ XVII–XVII a2 to XIX a2/b5. Right or left oviduct crossing ventrally beneath nerve cord.

Distribution.

Known in mountainous regions of the central part of Hokkaido, Japan (Fig. 1).

Remarks.

The specimens examined in this study consist of small individuals. However, testisacs and ovisacs of the holotype, of which BL is 30.5 mm, are developed. In immature Orobdella specimens, testiscas are usually undeveloped, and hardly detected (Nakano pers. obs.). Therefore, there is a possibility that the holotype of this species is a mature leech.

Orobdella koikei is syntopic with Orobdella kawakatsuorum at Sounkyo (Locality No. 2 in Fig. 1). Specimens of Orobdella koikei collected from Sounkyo were clearly distinguished from those of Orobdella kawakatsuorum in Sounkyo by the number of annuli between the gonopores, annulation of XXV, morphology of the gastroporal duct and male atrium, and the length of epididymides. Therefore, Orobdella koikei can be treated as a distinct new species from Hokkaido.