Orobdella nakahamai, 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 : 82-85

Taxon classification Animalia Arhynchobdellida Orobdellidae

Orobdella nakahamai sp. n. Figs 6, 7, 8, 9

Type materials.

Holotype: KUZ Z1672, dissected, collected from under rocks of a small mountain stream at Mt. Takanosuyama (33.788°N, 133.271°E; Elev. ca. 1500 m; locality #4), Ino, Kochi Prefecture, Japan, by Ryosuke Okano on 4 July 2015. Paratype: KUZ Z1352, dissected, collected from under rocks of a small mountain stream at Mt. Iwagurosan (33.7516°N, 133.1533°E; Elev. ca. 1600 m; locality #5), Kumakogen, Ehime Prefecture, Japan, by Naoyuki Nakahama on 10 August 2010. For locality numbers, see Fig. 1.

Additional material.

KUZ Z1680, collected from Kaminodoi (32.942714°N, 132.841350°E; Elev. ca 140 m; locality #6, see Fig. 1), Shimanto, Kochi Prefecture, Japan, by Ryosuke Okano on 2 November 2015.

Type locality.

Japan, Kochi Prefecture: Ino, Ishizuchi Mountains, Mt. Takanosuyama (Shikoku).

Diagnosis.

Body length of mature individual greater than 15 cm. Somites IX–XXV octannulate. Clitellum in X c9 to XIII b4. Male gonopore in slightly posterior to middle of XI c11 or XI c10/c11, female gonopore in XIII b2/b3, behind gastropore, gonopores separated by 1/2 + 11 or 12 annuli. Pharynx reaching to XIV b1-b3/b4. Gastropore conspicuous, in XIII b2/b3. Gastroporal duct bulbous, slightly winding at junction with gastropore. Paired epididymides in XV to XVII, occupying 12 or 13 annuli (one and half somites). Atrial cornua ovate or ellipsoid.

Description of holotype.

BL 237.7 mm, BW 11.3 mm (Fig. 6). Caudal sucker ventral, elliptic, CL 3.9 mm, CW 6.5 mm (Figs 6B, 7D).

Somites III–V biannulate; III and V, (a1 + a2) = a3; IV, (a1 + a2)> a3; V a3 forming posterior margin of oral sucker (Fig. 7A, B). Somite VI dorsally quinquannulate, b1 = b2 <a2> b5 <b6; ventrally quadrannulate, a1 = a2> b5 <b6 (Fig. 7A, B). Somite VII quiquannulate, a1> b3 = b4 = b5 = b6, a1 with slight lateral furrow on each side (Fig. 7A, B). Somite VIII dorsally septannulate, a1 (with obvious secondary furrow, b1 = b2)> b3 = b4 = c9 = c10 = c11 = c12; ventrally octannulate, b1 = b2 = b3 = b4 = c9 = c10 = c11 = c12 (Fig. 7A, B). Somite IX octannulate, b1 = b2 = b3 <b4 = c9 = c10 = c11 = c12. Somites X–XXV octannulate, b1 = b2 = b3 = b4 = c9 = c10 = c11 = c12 (Fig. 7 C–E). Somite XXVI octannulate, b1 = b2 = b3 = b4 = c9 = c10 = c11> c12. Somite XXVII comprises three annuli, second and third annuli, respectively, with slight dorsal furrow; first annulus being ventrally last complete annulus (Fig. 7C, D). Anus behind somite XXVII (Fig. 7C).

X c9 and XIII b4, respectively, being first and last annuli of clitellum (Fig. 7E).

Male gonopore in slightly posterior to middle of XI c11 (Fig. 7E). Female gonopore in XIII b2/b3, inconspicuous, located posterior to gastropore (Fig. 7E, F). Gonopores separated by 1/2 + 11 annuli (Fig. 7E).

Anterior ganglionic mass in VI b5 and b6. Ganglion VII in a1. Ganglia VIII–X, of each somite, in b3 and b4. Ganglion XI in b4 (Fig. 8B). Ganglion XII in b3 and b4 (Fig. 8B). Ganglion XIII in b4 (Fig. 8B). Ganglia XIV–XVI, of each somite, in b3 and b4 (Fig. 8B). Ganglion XVII in b3 (Fig. 8B). Ganglion XVIII in b3 and b4. Ganglion XIX in b3. Ganglia XX and XXI, of each somite, in b3 and b4. Ganglia XXII–XXV, of each somite, in b3. Ganglion XXVI in b2. Posterior ganglionic mass in XXVI c10-c12.

Eyes undetectable.

Nephridiopores in 17 pairs, one each situated ventrally at posterior margin of b2 of each somite in VIII–XXIV (Fig. 7B, D, E).

Pharynx reaching to XIV b1 (Fig. 8A). Crop reaching to XXII c9. Gastropore conspicuous, ventral, in XIII b2/b3 (Fig. 7E, F). Gastroporal duct bulbous, slightly winding at junction with gastropore, joining with crop in XIII c12 (Fig. 8A). Intestine reaching to XXV/XXVI.

Testisacs (Fig. 8B); on right side, in XVII c9 to XXV c11, in total approx. 164 testisacs, 7 in XVII, 18 in XVIII, 24 in XIX, 21 in XX, 21 in XXI, 20 in XXII, 23 in XXIII, 16 in XXIV, 14 in XXV; on left side, in XVII b4 to XXV c12, in total approx. 160 testisacs, 6 in XVII, 15 in XVIII, 24 in XIX, 20 in XX, 22 in XXI, 18 in XXII, 18 in XXIII, 21 in XXIV, 16 in XXV. Paired epididymides in XV c9 to XVI/XVII, occupying 12 annuli (Fig. 8B). Paired ejaculatory ducts in XI c9 to XV c9; coiled in position posterior to ovisacs; each duct crossing ventrally beneath each ovisac, then running straight 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. 8 B–E). Pair of muscular atrial cornua ovate, in XI c9-c11 (Fig. 8 B–E). Atrium short, muscular, globular in XI c10 and c11 (Fig. 8 B–E).

Paired ovisacs in XIII b3 and b4 (Fig. 8B, F). Oviducts; right oviduct crossing ventrally beneath nerve cord; both oviducts converging into common oviduct in XIII b3/b4 (Fig. 8B, F). Common oviduct directly descending to female gonopore (Fig. 8B, F).

Variations.

BL 162.3-180.4 mm, BW 7.6-98 mm, CL 3.3-4.3 mm, CW 5.6 mm. Somite VI quadrannulate, a1 (dorsally b1 = b2) = a2 (dorsally b3 = b4)> b5 <b6, or dorsally quinquannulate, b1 = b2 <a2> b5 <b6. Somite VII quinquannulate, a1 (dorsally b1 = b2 in KUZ Z1680)> b3 = b4 = b5 = b6. Somite VIII octannulate, b1 = b2 <b3 <b4 = c9 = c10 = c11 = c12, or ventrally septannulate, a1 (b1 = b2)> b2 = b3 = b4 = c9 = c10 = c11 = c12. Somite IX octannulate, b1 = b2 = b3 = b4 = c9 = c10 = c11 = c12. Somite XXVI dorsally octannulate, b1 = b2 = b3 = b4> c9 = c10 = c11 = c12, ventrally septannulate, b1 = b2 = b3 = b4> c9 = c10 <b6, or sexannulate, b1 = b2 = b3 = b4 = b5 <b6 (c11 = c12). Somite XXVII comprises two annuli, first annulus with slight three dorsal furrows, or comprises four annuli. Eyes in one pair, dorsally on posterior margin of II (KUZ Z1352). Pharynx reaching to XIV b3/b4. Crop reaching to XXII b1/b2. Gastroporal duct joining with crop in XIV b3. Intestine reaching to XXV b4. Male gonopore in XI c10/c11 (KUZ Z1680), thus gonopores separated by 12 annuli. Testisacs in XVII c10 to XXV c11; on right side, in total approx. 122 testisacs, 5 in XVII, 18 in XVIII, 17 in XIX, 18 in XX, 16 in XXI, 15 in XXII, 14 in XXIII, 10 in XXIV, 9 in XXV; on left side, in total approx. 126 testisacs, 4 in XVII, 16 in XVIII, 19 in XIX, 21 in XX, 17 in XXI, 13 in XXII, 13 in XXIII 11 in XXIV, 12 in XXV. Paired epididymides in XV c10/c11 to XVII b3/b4, occupying 13 annuli. Pair of muscular atrial cornua ellipsoid. Left oviduct crossing ventrally beneath nerve cord; both oviducts converging into common oviduct in XIII b3.

Colouration.

In life, dorsal surface bluish gray (Fig. 9); ventral surface bluish white; clitellum, when obvious, paler than other body parts (Fig. 9). Color faded in preservative.

Etymology.

The specific name is a noun in the genitive case formed directly from the name of Mr Naoyuki Nakahama, who collected a specimen of this new species.

Distribution.

This species was collected from the Ishizuchi Mountains and south-western part of Kochi Prefecture. The lowest elevation among the localities was ca. 140 m, and the highest was ca. 1600 m. The locality data for this species suggested that it is distributed in mountainous regions in the western part of Shikoku, Japan. Its distribution may not be restricted by habitat elevation.

Natural history.

Mature leeches with an obvious clitellum, KUZ Z1352 and Z1672, were collected on 4 July and 10 August, respectively, in the Ishizuchi Mountains. Therefore, the reproductive season of Orobdella nakahamai in the mountains begins before or during July, and then continues at least to early August.

Remarks.

Orobdella nakahamai is only the second octannulate large-type species known within the genus. According to Nakano (2012c), this species can be distinguished from another octannulate species Orobdella octonaria by the following combination of characteristics (Table 3): female gonopore in XIII b2/b3, gonopores separated by 1/2 + 11 or 12 annuli and epididymides in XV to XVII. Orobdella nakahamai is clearly distinguishable from the quadrannulate and sexannulate species of this genus because it possesses octannulate mid-body somites.