Orobdella mononoke Nakano 2012

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 139.3 mm, BW 9.2 mm (Figs 2, 3). Caudal sucker ventral, oval, its diameter smaller than BW (Figs 3B, 4D). In life, dorsal surface of somites I–XIII, XXVII and caudal sucker grayish purple, and of somites XIV–XXVI amber (Fig. 2), ventral surface grayish white. Color faded in preservative, without any dark lines (Fig. 3). Somite I completely merged with prostomium (Fig. 4A). Somites II and III uniannulate (Fig. 4A). Somites IV and V biannulate, (a1+a2) = a3 (Fig. 4A), V a3 forming posterior margin of oral sucker (Fig. 4B). Somite VI quadrannulate on dorsal, b1 = b2 < a2 = a3, triannulate on venter, a1 = a2 = a3 (Fig. 4A–B). Somite VII quadrannulate, a1 = a2 = b5 = b6 (Fig. 4A–B). Somites VIII–XXV sexannulate. b1 = b2 = a2 = b5 = c11 = c12 (Fig. 4A–E). Somite XXVI quinquannulate, b1 = b2 = a2 < b5 = b6, b5 and b6 with slight furrows on dorsal (Fig. 4C–D), XXVI b5 being last complete annulus on venter (Fig. 4D). Somite XXVII comprising a few furrows; anus behind it with no post-anal annulus (Fig. 4C). Anterior ganglionic mass in VI a2 and a3. Ganglion VII in a1 and a2. Ganglia VIII–XV, XXII and XXIII in a2 of each somite (Fig. 5A). Ganglia XVI–XXI and XXIV in b2 and a2 of each somite (Fig. 5A). Ganglion XXV in b2. Ganglion XXVI in XXV c12 and XXVI b1. Posterior ganglionic mass in XXVI a2 and b5. Eyes three pairs, first pair dorsally on posterior margin of II (Fig. 4A), second pair dorsolaterally on middle of V (a1 + a2). Nephridiopores in 17 pairs, ventrally at posterior margin of a1 of each somite of VIII–XXIV (Fig. 4B, E). Papillae numerous, minute, hardly visible, one row on every annulus. Pharynx agnathous, euthylaematous, reaching to XIV/XV (Fig. 4F). Crop tubular, acaecate, in XIV/XV to XXI b2/a2. Gastropore conspicuous, ventral, located slightly anterior to middle of XIII b2 (Fig. 4E, G). Gastroporal duct, winding at junction with gastropore, tubular but slightly bulbous at junction with crop, joining with crop in XIV c11 (Fig. 4F). Intestine tubular, acaecate, in XXI b2/a2 to XXIV b2/a2. Rectum, tubular, thin-walled. Male gonopore in the furrow of XI c11/c12 (Fig. 4E). Female gonopore located slightly anterior to middle of XIII b2, inconspicuous, located behind gastropore (Fig. 4E, G). Gonopores separated by 8 + 1/2 annuli (Fig. 4E). Testisacs multiple, one or two testisacs on each side in each annulus, in XIX c11 to XXV b5 (Fig. 5A). Paired epididymides in XVI b2 to XIX b5 (Fig. 5A). Ejaculatory bulbs absent. Ejaculatory ducts in XI b5 to XVI b2, 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. 5A–D). Pair of atrial cornua in XI b5 and c11, muscular, ovate (Fig. 5A–B, D). Atrium short, muscular, globular in XI c11 and c12 (Fig. 5B–D). Penis sheath and penis absent. Ovisacs one pair, thin-walled, globular, in XIII a2 and b5 (Fig. 5A, E). Oviducts thin-walled, right oviduct crossing ventrally beneath nerve cord, both oviducts converging into common oviduct in XIII b2 (Fig. 5A, E). Common oviduct thin-walled, short, directly ascending to female gonopore (Fig. 5E).

Known from mountainous regions of Yakushima Island, Japan (Fig. 1).