Orobdella brachyepididymis, 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 : 81-82

Taxon classification Animalia Arhynchobdellida Orobdellidae

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

Type materials.

Holotype: KUZ Z1673, dissected, collected from under a rock along a road (33.87151°N, 134.12016°E; Elev. ca. 990 m; locality #2, see Fig. 1) at Mt. Ichinomori, Mima, Tokushima Prefecture, Japan, by TN on 7 July 2015. Paratype: KUZ Z1674, dissected, collected from under a rock along a road (33.87119°N, 134.12233°E; Elev. ca. 1014 m) at the type locality, by TN on 7 July 2015.

Type locality.

Japan, Tokushima Prefecture: Mima, Mt. Ichinomori (Shikoku).

Diagnosis.

Body length of mature individual reaching to ca. 5 cm. Somite IV uniannulate, somites VIII–XXV quadrannulate. Clitellum in XI b5 to XIII a2. Male gonopore in middle of XI b6, female gonopore in anterior margin of or slightly anterior to middle of XIII a1, behind gastropore, gonopores separated by 1/2 + 4 [+ (<1/2)] annuli. Pharynx reaching to XIV a1-a1/a2. Gastropore conspicuous, in anterior margin of or slightly anterior to middle of XIII a1. Gastroporal duct tubular, slightly bulbous at junction with gastropore. Paired epididymides in XX to XXI, occupying four annuli (one somite). Atrial cornua small ovate.

Description of holotype.

BL 51.6 mm, BW 5.2 mm (Fig. 2). Caudal sucker ventral, elliptic, CL 3.0 mm, CW 3.4 mm (Figs 2B, 3D).

Somites III, IV uniannulate; IV with slight dorsal furrow (Fig. 3A). Somite V biannulate, (a1 + a2) = a3; a3 forming posterior margin of oral sucker (Fig. 3A, B). Somites VI and VII triannulate; VI, a1 <a2> a3, a2 with slight dorsal furrow; VII, a1 = a2 = a3 (Fig. 3A, B). Somites VIII–XXV quadrannulate, a1 = a2 = b5 = b6 (Fig. 3 A–E). Somite XXVI triannulate; dorsally a1> a2 <a3, a3 with slight furrow; ventrally a1> a2 = a3; a3 being ventrally last complete annulus (Fig. 3C, D). Somite XXVII uniannulate with slight dorso-lateral furrows (Fig. 3C). Anus behind somite XXVII (Fig. 3C).

X b5 and XIII a2, respectively, being first and last annuli of clitellum (Fig. 3E).

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

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

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).

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

Pharynx reaching to XIV a1 (Fig. 3G). Crop reaching to XIX b5/b6. Gastropore conspicuous, ventral, in anterior margin of XIII a1 (Fig. 3E, F). Gastroporal duct tubular, but slightly bulbous and winding at junction with gastropore, joining with crop in XIV a1 (Fig. 3G). Intestine reaching to XXIV/XXV.

Testisacs (Fig. 4A); on right side, in XXI b6 to XXV b5, in total approx. 27 testisacs, 2 in XXI, 7 in XXII, 6 in XXIII, 7 in XXIV, 5 in XXV; on left side, in XXI b6 to XXV b6, in total approx. 25 testisacs, 2 in XXI, 5 in XXII, 7 in XXIII, 5 in XXIV, 6 in XXV. Paired epididymides; right epididymis in XX b5/b6 to XXI b5/b6, occupying 4 annuli; left epididymis in XX b6 to XXI b5/b6, occupying 4 annuli (Fig. 4A). Paired ejaculatory ducts, thick; right duct in XI b5 to XX b5/b6; left duct in XI b5 to XX b6; loosely coiled in position posterior to ovisacs; each widening from respective junction with epididymis, narrowing at junction with atrial cornua, then turning gradually inward toward atrial cornua without pre-atrial loop (Fig. 4 A–D). Pair of muscular atrial cornua small ovate, in XI b5 and b6 (Fig. 4 A–D). Atrium short, muscular, globular in XI b5 and b6 (Fig. 4 A–D).

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

Variation.

BL 36.3 mm, BW 3.5 mm, CL 1.8 mm, CW 2.2 mm. Somite IV uniannulate Somite VI triannulate, a1 = a2 = a3. Male gonopore in middle of XI b6, female gonopore in slightly anterior to middle of XIII a1, go nopores thus separated by 1/2 + 4 + (<1/2) annuli. Pharynx reaching to XIV a1/a2. Crop reaching to XX a1/a2. Gastropore in slightly anterior to middle of XIII a1. Gastroporal duct tubular, but slightly bulbous at junction with gastropore, joining with crop in XIV a2/b5. Intestine reaching to XXIV a1/b5. Testisacs undetectable. Paired epididymides; right epididymis in XX b5 to XXI a2/b5; left epididymis in XX a2/b5 to XXI a2; each occupying four annuli. Atrium in XI b6. Left oviduct crossing ventrally beneath nerve cord.

Colouration.

In life, dorsal surface grayish (Fig. 5); ventral surface whitish red; clitellum, when obvious, whitish grayish pale ochre (Fig. 5). Color faded in preservative.

Etymology.

The specific name is a compound noun in apposition derived from the Greek words transliterated into Latin, brachys (short) and epididymis (epididymis), referring to the fact that the epididymides of this species occupy only four annuli.

Distribution.

This species was found only from its type locality.

Natural history.

This species was found curled up under rocks in moist mountainous habitats. As oligochaete worms were observed in the digestive tract of a dissected specimen, KUZ Z1674, this species is an earthworm-eater, as are the other known Orobdella species.

A mature leech, KUZ Z1673, was collected on 7 July. Therefore, Orobdella brachyepididymis is considered to enter its reproductive season before early July.

Remarks.

The specimens were small (up to 52 mm), but the holotype was determined to be mature because it possessed an obvious clitellum and developed testisacs.

According to taxonomic studies ( Nakano 2010, 2012b, 2014, 2016, Nakano and Gongalsky 2014, Nakano and Lai 2012, Nakano and Seo 2014), the new species is distinguished from the eight quadrannulate species (i.e. Orobdella esulcata Nakano, 2010, Orobdella kawakatsuorum Richardson, 1975, Orobdella ketagalan Nakano & Lai, 2012, Orobdella koikei Nakano, 2012b, Orobdella masaakikuroiwai , Orobdella naraharaetmagarum , Orobdella tsushimensis Nakano, 2011a and Orobdella whitmani ) by the following combination of characteristics (Table 2): body length less than or reaching ca. 5 cm, IV uniannulate, XXV quadrannulate, gonopores separated by 1/2 + 4 [+ (<1/2)] annuli, gastroporal duct tubular, epididymides in XX to XXI and atrial cornua small ovate.