Orobdella ijimai Oka 1895
Creators: name: Nakano, Takafumi
Publisher: name: Zenodo
Year: 2011
Subjects: Biodiversity
Taxonomy
Animalia
Annelida
Clitellata
Arhynchobdellida
Gastrostomobdellidae
Orobdella
Orobdella ijimai

description: Orobdella ijimai Oka, 1895
(Figs. 2–4)
Orobdella ijimai Oka (1895): 284–285, pl. 28, figs. 2, 9–10, pl. 29, fig. B, pl. 30, figs. 2, 5–8; Oka (1910a): 19 (in part); Oka (1910b): 178 (in part); Oka (1935): 240; Oka & Nagao (1965): 574; Soós (1966): 376, 382, 397; Richardson (1971): 599 – 600; Lukin (1976): 466; Sawyer (1986): 680, 747.
Diagnosis. In life, dorsal surface yellowish green, ventral surface whitish yellow. Somite VII quadrannulate. Somites VIII–XXV complete sexannulate. Somite XXVI quadrannulate. Pharynx descending to XIII/XIV. Gastropore conspicuous at XIII b2. Gastroporal duct muscular, bulbiform, tortuous at junction with gastropore. Male gonopore at XI c12. Female gonopore inconspicuous at XIII b2, behind gastropore. Gonopores separated by 1/2 + 7 + 1/2 annuli.
Type specimens. The ten specimens, which were used in the original description of O. ijimai (Oka 1895), are automatically considered the syntypes in accordance with the Article 73.2 of the International Code of Zoological Nomenclature (International Commisson on Zoological Nomenclature 1999). I surveyed leech collection at NSMT and UMUT (see Materials and Methods above), however, I could not find out any type series of O. ijimai.
According to the Art. 75.1 of the Code, a neotype should be designated when 1) no name-bearing type specimen is believed to be extant and 2) a name-bearing type is necessary to define the nominal taxon objectively (International Commisson on Zoological Nomenclature 1999). The nomenclatural status of Orobdella ijiami does not apply the condition 2) above, because its type locality is only one place, Nikko, Japan and I did not collect any other sexannulate Orobdella species from the type locality. As shown at the Example of the Art. 75.2 of the Code, a neotype designation for such species like O. ijimai would be invalid (International Commisson on Zoological Nomenclature 1999). Therefore, I have not designated a neotype for O. ijimai in this study.
Materials examined. A total of six specimens newly collected from around the Inarigawa Sand-tap Dams at the type locality, Nikko, Tochigi Pref., Japan by Takafumi Nakano. Four specimens collected on May 26, 2010: KUZ Z108 (alt. 960 m, 36°47´01˝N, 139°34´54˝E), dissected; KUZ Z109 (alt. 946 m, 36°46´59˝N, 139°34´55˝E); KUZ Z110, dissected, and KUZ Z111 (alt. 940 m, 36°46´59˝N, 139°34´56˝E). Two specimens collected on May 28, 2010: KUZ Z112 (alt. 990 m, 36°47´08˝N, 139°34´54˝E); and KUZ Z113, dissected (alt. 1014 m, 36°47´13˝N, 139°34´51˝E).
Emended description. Body firm, muscular, elongated, maximum BL 93.3 mm (KUZ Z111), maximum BW 6.3 mm (KUZ Z110) (Fig. 2). Caudal sucker ventral, oval, its diameter slightly smaller than maximum body width (Fig. 3 D). In life, color variable, generally dorsal surface yellowish green, ventral surface whitish yellow, dorsal surface darker than ventral surface. Color faded in preservative, without any dorsal dark lines.
Somite I completely merged with prostomium (Fig. 3 A). Somite II uniannulate, slightly separated from I (Fig. 3 A). Somite III biannulate, (a1 + a2)> a3 (Fig. 3 A) or uniannulate (KUZ Z110). Somite IV biannulate, (a1 + a2)> a3 (Fig. 3 A). Somite V biannulate, a3 forming posterior margin of oral sucker (Fig. 3 A, B). Somites VI complete triannulate (Fig. 3 A, B). Somite VII complete quadrannulate. Somites VIII–XXV complete sexannulate, b1 = b2 = a2 = b5 = c11 = c12 (Fig. 3 A–E, H), X b5 the first annulus of the clitellum, XIII a2 the last annulus of the clitellum (KUZ Z110). Somite XXVI quadrannulate, a1 = a2 = b5> b6, b6 the last complete annulus on the venter (Fig. 3 C, D). Somite XXVII uniannulate or biannulate (Fig. 3 C). Anus behind XXVII (Fig. 3 C). Post-anal annulus absent (Fig. 3 C).
Anterior ganglionic mass in VI a1–a3. Ganglion VII in a2. Ganglia VIII–XXV in a2 of each somite, except ganglion XIV in b5 (Fig. 3 H). Ganglion XXVI in a1. Posterior ganglionic mass in XXVI b5 and b6.
Eyes three pairs, first pair dorsally on posterior margin of II, second and third pairs dorsolaterally on posterior margin of V (a1 + a2) (Fig. 3 A). Nephridiopores 17 pairs, ventrally at posterior margin of b2 of each somite, at VIII– XXIV (Fig. 3 B, E). Papillae numerous, minute, hardly visible, one row on every annulus.
Pharynx agnathous, euthylaematous, reaching to XIII/XIV. Crop tubular, acecate, reaching to XX c11/c12– XXI a2 (Fig. 4). Gastropore conspicuous, ventral, at middle of XIII b2 (Fig. 3 E, G). Gastroporal duct muscular, tortuous at junction with gastropore, bulbiform, joining with crop in XIV b1–b2 (Fig. 3 F). Intestine tubular, acecate, reaching to XXIV a2/b5–c11, one pair of undeveloped chambers at junction with crop or chamber absent (Fig. 4). Rectum tubular, thin-walled.
Male gonopore at the middle or posterior of XI c12 (Fig. 3 E). Female gonopore at XIII b2, inconspicuous, diagonally behind gastropore (Fig. 3 G). Gonopores separated by 1/2 + 7 + 1/2 annuli (Fig. 3 E). Testisacs multiple, two or three testisacs on each side in each annulus, in XVIII c11–XIX a2 to XXV b1–b5 (Fig. 3 H). Epididymides in XVI b5/c11–c11/c12 to XVIII c11–XIX a2 (Fig. 3 H). Ejaculatory bulbs absent. Ejaculatory ducts in XI b5 to XVI b5/c11–c11/c12, loosely coiled, widen gradually from each junction with epididymis, narrow at each junction with atrial cornu, then turning sharply inward toward atrial cornu without pre-atrial loop (Fig. 3 H–K). Atrial cornua in XI b5 to c12, muscular, nearly oviform (Fig. 3 H–K). Atrium short, muscular, globular in XI c12 (Fig. 3 I–K). Ovisacs one pair, thin-walled, globular, in XIII a2 to c11 (Fig. 3 H, L). Oviduct thin-walled, left oviduct crossing ventrally beneath nerve cord, both oviducts converging into common oviduct in XIII a2 (Fig. 3 H, L). Common oviduct thin-walled, short, directly descending to female gonopore (Fig. 3 L).
Remarks. The original description of O. ijimai is accurate in the number of annuli, 1/2 + 7 + 1/2 annuli, between gonopores (Oka 1895). This characteristic, possessing total 129 annuli and having complete sexannulate mid-body somites have been the key external features of O. ijimai. Characteristics of the specimens examined in this study were coincident with the above characteristics in the original description. Specimens newly collected from Nikko were thus identified as O. ijimai.
Oka (1895) and Soós (1966) treated O. ijimai without any reference to a gastroporal duct. But Orobdella ijimai has a conspicuous gastropore and bulbiform gastroporal duct (Fig. 3 F, G). However, an inconspicuous female gonopore is distinguished beside a conspicuous gastropore only by a greater magnification. Therefore, a gastropore of O. ijimai is easily mistaken for a female gonopore.
Oka (1895) noted that this species had post-ceca. In the examined specimens of Orobdella ijimai, I could not establish any crop ceca or intestinal ceca. But the intestine has an undeveloped chamber at the junction with crop (Fig. 4). Therefore, the post-ceca in the original description by Oka (1895) might be those chambers as mentioned by Richardson (1975). The original description also noted that O. ijimai possesses the first pair of eyes on the anterior margin of III, the first pair of nephridiopores at IX b2 and the last pair of nephridiopores at XXV b2. However, the first pair of eyes is on the posterior margin of II (Fig. 3 A), the first pair of nephridiopores is at VIII b2 (Fig. 3 B) and the last pair of nephridiopores is at XXIV b 2 in the examined specimens.
Distribution and ecology. Known from Honshu, Shikoku, Kyushu, Japan (Oka & Nagao 1965). Oka (1910a; b) recorded O. ijimai from Amamioshima Island in the Ryukyu Archipelago, Japan. However, the sexannulate Orobdella leech from that island is another species as described below. Leeches were found under rocks or fallen leaves.
description: Published as part of Nakano, Takafumi, 2011, Redescription of Orobdella ijimai (Hirudinida: Arhynchobdellida: Gastrostomobdellidae), and two new species of Orobdella from the Ryukyu Archipelago, Japan, pp. 1-15 in Zootaxa 2998 on pages 3-6, DOI: 10.5281/zenodo.207870