Orobdella mononoke, Nakano, Takafumi, 2012

Nakano, Takafumi, 2012, A new sexannulate species of Orobdella (Hirudinida, Arhynchobdellida, Orobdellidae) from Yakushima Island, Japan, ZooKeys 181, pp. 79-93 : 82-86

Orobdella mononoke sp. n. Figs 2-5

Diagnosis.

In life, dorsal surface of somites I–XIII, XXVII and caudal sucker grayish purple and of somites XIV–XXVI amber, ventral surface grayish white. Somite VI quadrannulate on dorsal, b1 = b2 <a2 = a3, and triannulate on venter, a1 = a2 = a3. Somite VII quadrannulate, somites VIII–XXV sexannulate, somite XXVI quinquannulate. Pharynx reaching to XIV. Gastropore conspicucous at XIII b2 (slightly anterior to middle of annulus). Gastroporal duct, winding at junction with gastropore, tubular but slightly bulbous at junction with crop. Male gonopore at XI c11/c12, female gonopore at XIII b2, behind gastropore, gonopores separated by 8 + 1/2 annuli. Paired epididymides in XV–XIX (approximately four somites). Atrial cornua developed, ovate.

Type materials.

KUZ Z224, holotype, dissected, collected from under a rock along a mountain trail at Shiratani–unsuikyo, Yakushima, Kagoshima Pref. (Yakushima Island), Japan (30°22.78'N, 130°34.49'E; Alt. 648 m), by Takafumi Nakano on 29 October, 2011.

Four paratypes collected from under rocks along mountain trails in Yakushima, Kagoshima Pref. (Yakushima Island), Japan, by Takafumi Nakano. Two specimens from the type locality: KUZ Z221 (30°22.87'N, 130°34.68'E; Alt. 649 m), dissected, on 28 October, 2011, and KUZ Z225 (30°22.75'N, 130°34.49'E; Alt. 646 m), on 29 October, 2011. Two specimens from Kusugawa on 28 October, 2011: KUZ Z222 (30°23.76'N, 130°35.25'E; Alt. 363 m), and KUZ Z223 (30°23.75'N, 130°35.25'E; Alt. 363 m), dissected.

Etymology.

The specific name is from the Japanese animation movie title 'Mononoke-hime (Princess Mononoke)'. The type locality of this new species is the origin of an epic forest in that movie. The specific name is a Japanese word, not a Latin or latinized word.

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 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. 4 A–B). Somite VII quadrannulate, a1 = a2 = b5 = b6 (Fig. 4 A–B). Somites VIII–XXV sexannulate. b1 = b2 = a2 = b5 = c11 = c12 (Fig. 4 A–E). Somite XXVI quinquannulate, b1 = b2 = a2 <b5 = b6, b5 and b6 with slight furrows on dorsal (Fig. 4 C–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. 5 A–D). Pair of atrial cornua in XI b5 and c11, muscular, ovate (Fig. 5 A–B, D). Atrium short, muscular, globular in XI c11 and c12 (Fig. 5 B–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).

Variation.

In life, color generally same as holotype (Fig. 2). Somites III and IV uniannulate. Pharynx reaching to XIV b5/c11-XIV c11/c12. Crop reaching to XXI b2/a2-XXI a2. Gastroporal duct joining with crop in XIV b5; immature specimen (KUZ Z223), simple tubular. Intestine reaching to XXIV b1-XXIV b5. Testisacs in XIX b1 to XXIV c11. Epididymides in XV a2 to XVIII c11. Immature specimen (KUZ Z223), pair of atrial cornua in XI c11, fusiform. Left oviduct crossing ventrally beneath nerve cord.

Distribution.

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

Phylogenetic position.

The ML tree with ln L = -14306.80 (Fig. 6) was nearly identical to the obtained BI tree (not shown). Monophyly of the genus Orobdella was confirmed (BS = 99 %, BPP = 100 %). The genus Orobdella then divided into two clades: clade A (BS = 99 %, BPP = 100 %) consisted of two species from Hokkaido, Japan, Orobdella kawakatsuorum Richardson, 1975 and Orobdella koikei ; and clade B (BS = 98 %, BPP = 100 %) included all the other Orobdella species. Clade B comprised two subclades: subclade B1 was Orobdella tsushimensis Nakano, 2011 from Tsushima Island, Japan; and subclade B2 (BS = 70 %, BPP = 100 %) was further divided into two subclades. Subclade B2a (BS = 92 %, BPP = 100 %) included Orobdella mononoke sp. n., Orobdella esulcata Nakano, 2010 from Kyushu, and two Orobdella species from the Ryukyu Archipelago, Orobdella dolichopharynx and Orobdella shimadae . Subclade B2b (BS = 73 %, BPP = 100 %) consisted of three species from Honshu, Japan, Orobdella whitmani Oka, 1895, Orobdella ijimai and Orobdella octonaria .

In subclade B2a, monophyly of Orobdella dolichopharynx and Orobdella shimadae was well supported (BS = 93 %, BPP = 100 %). However, the precise phylogenetic position of Orobdella mononoke sp. n. in the sublcade could not be determined. In the ML analysis, Orobdella mononoke sp. n. and Orobdella esulcata formed a monophyletic clade, but this clade was not supported well (BS = 30 %). In the BI analysis, Orobdella mononoke sp. n. and two Ryukyu Archipelago species formed a monophyletic clade, but this relationship was not also supported (BPP = 77 %).

Remarks.

Orobdella mononoke sp. n. differs from the three other sexannulate congeneric species, Orobdella ijimai , Orobdella dolichopharynx , and Orobdella shimadae , in the following characteristics (Table 3): 1) dorsal surface bicolor, I–XIII, XXVII and caudal sucker grayish purple, XIV–XXVI amber; 2) VI quadrannulate on dorsal; 3) VII quadrannulate; 4) VIII sexannulate; 5) gonopores separated by 8 + 1/2 annuli; 6) pharynx reaching to XIV; 7) gastroporal duct tubular but bulbous at junction with crop; 8) epididymides in XV–XIX (approximately four somites); and 9) atrial cornua ovate. Orobdella mononoke sp. n. is clearly distinguished from Orobdella esulcata , Orobdella kawakatsuorum , Orobdella koikei , Orobdella tsushimensis , Orobdella octonaria and Orobdella whitmani , in having mid-body somites that are sexannulate; they are quadrannulate in Orobdella esulcata , Orobdella kawakatsuorum , Orobdella koike , Orobdella tsushimensis and Orobdella whitmani , and octannulate in Orobdella octonaria .

The trees obtained in this study are nearly identical to those obtained in other phylogenetic analyses of the genus Orobdella ( Nakano 2012; Nakano et al. 2012). However, the phylogenetic position of Orobdella mononoke sp. n. still remains uncertain. Further taxon samplings will be needed to obtain robust phylogeny of the genus Orobdella .

Orobdella mononoke sp. n. inhabits Yakushima Island, which is located in the northern part of the Ryukyu Archipelago (Fig. 1). In the Ryukyu Archipelago, two sexannulate Orobdella species have been described: 1) Orobdella dolichopharynx from Amamioshima Island; and 2) Orobdella shimadae from Okinawajima Island. These two species have the following characteristics in common: 1) long pharynx, reaching to somite XVI; 2) rudimentary gastroporal duct and absence of gastropore; 3) absence of epididymides; and 4) absence of male atrial cornua. Although Orobdella mononoke sp. n. is a sexannulate species, this species does not share such morphological characteristics. Orobdella mononoke sp. n. possesses 1) normal length pharynx for the genus Orobdella , 2) developed gastroporal duct and conspicuous gastropore, 3) epididymides in XV–XIX, 4) ovate atrial cornua. Molecular phylogenetic analyses in this study also could not show monophyly of the three species in the Ryukyu Archipelago, Orobdella mononoke sp. n., Orobdella dolichopharynx and Orobdella shimadae . These differences of morphological characteristics and molecular phylogenetic analyses suggest that Orobdella mononoke sp. n. is not closely related to Orobdella dolichoharynx and Orobdella shimadae . In vertebrates, the fauna of the Osumi Islands, in which Yaushima Island is included, is related to that of Kyushu ( Toda et al. 2003). In the case of leeches, Haemadipsa japonica Whitman, 1886, which inhabits Honshu, Shikoku and Kyushu, Japan, is distributed in Yakushima Island ( Itoh 2003). In islands of the Ryukyu Archipelago south of Yakushima Island, however, another species, Haemadipsa rjukjuana Oka, 1910, is distributed ( Lai et al. 2011). A recent molecular phylogenetic study revealed that Haemadipsa japonica and Haemadipsa rjukjuana are not closely related species ( Borda and Siddall 2011). These facts are collateral evidence that Orobdella mononoke sp. n. is not very closely related to Orobdella dolichopharynx and Orobdella shimadae . Whether or not this is true, additional inventory surveys and molecular phylogenetic studies are needed to reveal the phylogenetic relationships within and the biogeographical history of the genus Orobdella .