Orobdella angustata Nakano 2018, sp. nov.
Creators: name: Nakano, Takafumi
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Annelida
Clitellata
Arhynchobdellida
Orobdellidae
Orobdella
Orobdella angustata

description: Orobdella angustata sp. nov.
[New Japanese name: kubire-kugabiru]
(Figs 1–3)
Diagnosis. Body length of pre-mature individuals exceeding 5 cm; possibly middle-type. Somite IV uniannulate, somites VIII–XXV quadrannulate. Male gonopore in middle of somite XI b6, female gonopore slightly anterior to middle of somite XIII a1, behind gastropore, gonopores separated by 1/2+4+1/3 annuli. Pharynx reaching to somite XIV a1/a2–a2. Gastropore conspicuous, slightly anterior to middle of somite XIII a1. Gastroporal duct bulbous. Paired epididymides in somites XVIII–XX, occupying 6–7 annuli. Paired ejaculatory ducts thick. Atrial cornua developed, hyperboloidal, i.e., each middle part constricted, then expanding at respective junction with ejaculatory duct.
Material examined. Holotype: KUZ Z1439, dissected, collected from Mt. Gomadanzan, Ryujinmura, Tanabe, Wakayama Prefecture (Kii Peninsula, Honshu island), Japan (34.06082°N, 135.564722°E; elev. 1285 m) by Naoki Koike on 10 October 2012. Paratypes (3 specimens): KUZ Z1440– Z1442, data same as for holotype (KUZ Z1440 was dissected) Description. Body firm and muscular, elongate, with constant width in caudal direction, dorsoventrally compressed, BL 54.3 mm, BW 5.5 mm (Fig. 1A, B). Caudal sucker ventral, elliptic, CL 2.6 mm, CW 3.2 mm (Figs 1B, 2D).
Somite I completely merged with prostomium (Fig. 2A). Somites II (=peristomium), III and IV uniannulate (Fig. 2A); somite II not separated from somite I. Somite V biannulate, (a1+a2)=a3; a3 forming posterior margin of oral sucker (Fig. 2A, B). Somites VI and VII triannulate, a1=a2=a3 (Fig. 2A, B). Somites VIII–XXV quadrannulate, a1=a2=b5=b6 (Fig. 2 A–E). Somite XXVI dorsally quadrannulate, a1>a2>b5=b6, ventrally triannulate, a1>a2<a3; a3 (=dorsally b5 and b6) being ventrally last complete annulus (Fig. 2C, D). Somite XXVII biannulate; a3 being dorsally last annulus with slight furrow (Fig. 2C). Anus behind somite XXVII; post-anal annulus absent (Fig. 2C).
Clitellum undeveloped.
Male gonopore in middle of somite XI b6 (Fig. 2E). Female gonopore slightly anterior to middle of somite XIII a1, inconspicuous, located posterior to gastropore (Fig. 2E, F). Gonopores separated by 1/2+4+1/3 annuli (Fig. 2E).
Anterior ganglionic mass in somite VI a2 and a3. Ganglion VII in a1 and a2. Ganglia VIII–XIII, of each somite, in a2 (Fig. 3A). Ganglia XIV–XV, of each somite, in a1 and a2 (Fig. 3A). Ganglion XVI in a2 (Fig. 3A). Ganglia XVII– XVIII, of each somite, in a1 and a2 (Fig. 3A). Ganglion XIX in a2 (Fig. 3A). Ganglia XX–XXIV, of each somite, in a1 and a2 (Fig. 3A). Ganglion XXV in somite XXIV b6 and somite XXV a1. Ganglion XXVI in somite XXV b6. Posterior ganglionic mass in somite XXVI a2 and a3 (=dorsally b5 and b6).
Eyes in 3 pairs, 1st pair dorsally on anterior margin of somite III, 2nd and 3rd pairs dorsolaterally on posterior margin of somite V (a1+a2) (Fig. 2A). Papillae numerous, minute, hardly visible, on row on every annulus.
Nephridiopores in 17 pairs, each situated ventrally at posterior margin of a1 of each somite in somites VIII–XXIV (Fig. 2B, D, E).
Pharynx agnathous, euthylaematous, reaching to somite XIV a1/a2 (Fig. 2G). Crop tubular, acecate, reaching to somite XX a1/a2. Gastropore conspicuous, ventral, slightly anterior to middle of somite XIII a1 (Fig. 2E, F). Gastroporal duct bulbous, winding at junction with gastropore, reaching to somite XIV a2 (Fig. 2G). Intestine tubular, acecate, reaching to somite XXIV a1/a2. Rectum tubular, thin-walled, straight.
Testisacs multiple, in somite XX b5 to somite XXV b6 (Fig. 3A); on right side, in total ~22 testisacs, 1 in XX, 4 in XXI, 4 in XXII, 6 in XXIII, 4 in XXIV, 3 in XXV; on lefl side, in total ~22 testisacs, 2 in XX, 4 in XXI, 4 in XXII, 5 in XXIII, 4 in XXIV, 3 in XXV. Paired epididymides in somite XVIII/XIX to somite XX b5, occupying 7 annuli (Fig. 3A). Paired ejaculatory ducts thick, in somite XI b5 to somite XVIII/XIX (Fig. 3A); loosely coiled in position posterior to ovisacs; each duct crossing ventrally beneath each ovisac, then nearly straight in position anterior to ovisacs; each noticeably winding from respective junction with epididymis, narrowing at junction with atrial cornua, then turning proximally toward atrial cornua without pre-atrial loop (Fig. 3A, B). Pair of muscular atrial cornua developed, hyperboloidal, in somite XI b5 and b6 (Fig. 3 A–D); each middle part constricted, then expanding at respective junction with ejaculatory duct. Atrium short, muscular, globular, in somite XI b5 and b6 (Fig. 3 B–D). Penis sheath and penis absent.
Paired ovisacs globular; right ovisac in somite XIII a2 and b5; lefl ovisac in somite XIII a2 (Fig. 3A, E). Oviducts thin-walled, lefl oviduct crossing ventrally beneath nerve cord (Fig. 3A, E); both oviducts converging in to common oviduct in somite XIII a1/a2. Common oviduct thin-walled, short, directly descending to female gonopore (Fig. 3E).
Variation. Measurements (mean±1SD, followed by ranges in parentheses; n =4, including holotype): BL 51.9± 2.7 mm (48.9–54.3 mm), BW 5.1± 0.28 mm (4.8– 5.5 mm), CL 2.4± 0.14 mm (2.4–2.6 mm), CW 2.8± 0.45 mm (2.3–3.2 mm). Somite XXVI generally triannulate, a1>a2<a3. Pharynx reaching to somite XIV a2. Crop reaching to somite XX a2/b5. Gastroporal duct reaching to somite XIV a2/b5. Intestine reaching to somite XXIV a2/ b5. Testisacs in somite XIX a2 to somite XXV b5; both sides, ~29 sacs, respectively. Paired epididymides occupying 6 annuli, respectively; right side in somite XVII/XVIII to somite XIX a2/b5; lefl side in somite XVIII a1 to somite XIX a2/b5. Paired ejaculatory ducts; right side in somite XI b5 to somite XVII/XVIII; lefl side in somite XI b5 to somite XVIII a1; coiled in position posterior to ovisacs. Paired ovisacs in somite XIII a2 and b5.
Coloration. In life, dorsal surface bluish black; ventral surface bluish white. Color faded in preservative.
Distribution. This species was collected only from its type locality.
Natural history. Although both dissected individuals possessed developed testisacs, their clitella were undeveloped, and hardly detected. The reproductive season of the new species thus remains unclear.
Etymology. The specific name is a participle in nominative singular derived from the Latin word angustatus (narrowed) referring to the fact that the male atrial cornua of this new species are constricted in their upper-middle parts.
Molecular analyses results. The BI tree (mean ln L =&minus;28673.07; Fig. 4) for estimating the phylogenetic position of the new species had an identical topology to that of the ML tree (ln L =&minus;29119.04; not shown). Orobdella angustata belonged to a well-supported clade (BS=99%, PP=1.0) containing the other four quadrannulate species inhabiting the western part of Honshu, Shikoku and northern Kyushu. Orobdella esulcata Nakano, 2010 formed a sister clade to the other four species including O. angustata. The monophyly of O. angustata and the well-supported clade consisting of O. brachyepididymis Nakano, 2016, O. kanaekoikeae Nakano, 2017 and O. naraharaetmagarum Nakano, 2016 (BS=100%, PP=1.0) was also fully supported (BS=100%, PP=1.0).
Remarks. Orobdella angustata unquestionably belongs to Orobdella because it possesses the generic diagnostic characteristics defined by Nakano (2016a); its molecular phylogenetic position also recovers the taxonomic position of the new species.
According to previous studies (Nakano 2010, 2011, 2012; Nakano and Lai 2012; Nakano 2014; Nakano and Seo 2014; Nakano 2016a, b, 2017b; Nakano and Lai 2017), the new species clearly differs from the other 11 quadrannulate congeners in having short epididymides in somite XVIII–XIX to somite XIX–XX that are occupying 6–7 annuli, thick ejaculatory ducts, and hyperboloidal developed atrial cornua (see Table 2). The new species differs from the six sexannulate species and two octannulate species by its midbody somites that are quadrannulate.
Because all the present individuals of O. angustata bear undeveloped clitella, it remains uncertain whether this new species is assigned to the small or middle types. The obtained phylogenies showed that O. angustata is phylogenetically close to the three “small-type” species, O. brachyepididymis, O. kanaekoikeae and O. naraharaetmagarum. However, the dissected specimens possessed fully developed genital organs, and thus they could be identified at least as pre-mature leeches. Because the body lengths of the dissected individuals exceed 5 cm, it is highly possible that O. angustata can be designated as a “middle-type” species. Future field surveys should collect individuals of O. angustata with obvious clitella, and reveal the natural history as well as the body length group of this species.
The male atrial cornua of Orobdella angustata show quite unique characteristics among those of the other Orobdella species. However, in this new species, the gastroporal duct, which is a spermatophore receptor of Orobdella leeches (Nakano 2017b), bears the bulbous feature that is common in the other congeners whose gastroporal ducts are developed. The characteristics of the gastroporal duct of O. angustata imply that its spermatophore may not be distinctive despite the noteworthy atrial cornua of the new species.
description: Published as part of Nakano, Takafumi, 2018, A New Quadrannulate Species of Orobdella (Hirudinida: Arhynchobdellida: Orobdellidae) from Kii Peninsula, Japan, pp. 43-49 in Species Diversity 23 (1) on pages 44-48, DOI: 10.12782/specdiv.23.43, http://zenodo.org/record/4583973