Orobdella montipumila, Nakano, 2021

Nakano, Takafumi, 2021, A new species of Orobdella (Hirudinida, Arhynchobdellida, Orobdellidae) from the Tsukuba Mountains in Japan, Soil Organisms 93 (2), pp. 105-113 : 106-111

publication ID	https://doi.org/ 10.25674/SO93iSS2id154
publication LSID	lsid:zoobank.org:pub:8B39C5A8-9380-472F-89A4-7F95BB534336
persistent identifier	https://treatment.plazi.org/id/42716527-1F13-507E-2247-659F79E5FE14
treatment provided by	Felipe
scientific name	Orobdella montipumila
status	sp. nov.

Treatment

Orobdella montipumila sp. nov.

( Figures 1–3 View Figure 1 View Figure 2 View Figure 3 )

Diagnosis. Body length of mature individuals reaching ca. 5 cm. Somite IV uniannulate, somites VIII–XXV quadrannulate. Clitellum in somite XI b5 to somite XIII a2. Male gonopore slightly anterior to middle of, or in middle of somite XI b5, female gonopore slightly anterior to middle of, or in middle of somite XIII a1, behind gastropore, gonopores separated by 1/2 + 4 + 1/2 annuli. Pharynx reaching to somite XIV a1–a2. Gastropore conspicuous, slightly anterior to middle of, or in middle of somite XIII a1. Gastroporal duct bulbous. Paired epididymides in somites XVII–XX, occupying 7–11 annuli. Atrial cornua developed, ovate.

Type material. Holotype. KUZ Z3913 View Materials ( Fig. 1 View Figure 1 ), dissected, collected from under a stone along a mountain trail, Onokawa , Mt. Tsukubasan in Tsukuba Mountains , Sakuragawa , Ibaraki Prefecture (Honshu island), Japan (36.234870°N, 140.099470°E; elev. 520 m), by T. Nakano on 22 May 2019 GoogleMaps . Paratypes. In total 4 specimens collected in Tsukuba Mountains , Ibaraki Prefecture : KUZ Z1349 View Materials , from under a stone along a mountain stream, Mt. Kabasan, Ishioka (~ 36.2°N, ~ 140.18°E), by K. Eto on 27 Mar 2010 GoogleMaps ; KUZ Z1367 View Materials , litter, Mt. Wagakunisan, Kasama (~ 36.32°N, ~ 140.20°E), by GoogleMaps R. Ueshima on 27 Nov 2011 ; KUZ Z1557 View Materials , litter, along a forest road, Uwaso, Ishioka (36.254361°N, 140.132222°E; elev. 403 m), by GoogleMaps T. Nakano on 16 Jun 2014 ; and KUZ Z1560 View Materials , from under soil along a mountain trail, Menokawa, Mt. Tsukubasan, Sakuragawa (36.2337°N, 140.1039°E; elev. 510 m) by Y. Yamane on 16 Jun 2014 GoogleMaps ; KUZ Z1349 View Materials , Z1367 View Materials , Z1557 View Materials , dissected .

Description. Body firm and muscular, elongate, with constant width in caudal direction, dorsoventrally compressed, BL 39.7 mm, BW 3.8 mm ( Fig. 1A, B View Figure 1 ). Caudal sucker ventral, elliptic, CL 1.9 mm, CW 2.5 mm ( Figs 1B View Figure 1 , 2D View Figure 2 ).

Somite I completely merged with prostomium. Somite II (= peristomium), III, IV uniannulate ( Fig. 2A View Figure 2 ). Somite V biannulate, (a1 + a2) = a3; a3 forming posterior margin of oral sucker ( Fig. 2A, B View Figure 2 ). Somites VI and VII triannulate, a1 = a2 = a3 ( Fig. 2A, B View Figure 2 ). Somites VIII–XXV quadrannulate, a1 = a2 = b5 = b6 ( Fig. 2A–E View Figure 2 ). Somite XXVI dorsally triannulate, a1 = a2 = a3, ventrally biannulate a1 <(a2 + a3); (a2 + a3) being ventrally last complete annulus ( Fig. 2C, D View Figure 2 ). Somite XXVII biannulate ( Fig. 2C View Figure 2 ). Anus behind somite XXVII; post-anal annulus absent ( Fig. 2C View Figure 2 ).

Somite X b5 and somite XIII a2, respectively, first and last annuli of clitellum ( Fig. 2E View Figure 2 ).

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

Anterior ganglionic mass in somite VI a2 and a3, Ganglia VII–IX, of each somite, in a2. Ganglia X and XI, of each somite, in a2 and b5 ( Fig. 3A View Figure 3 ). Ganglia XII– XVIII, of each somite, in a2 ( Fig. 3A View Figure 3 ). Ganglion XIX in a1 and a2 ( Fig. 3A View Figure 3 ). Ganglion XX in a1 ( Fig. 3A View Figure 3 ). Ganglia XXI and XXII, of each somite, in a1 and a2. Ganglion XXIII in a1. Ganglion XXIV in a1 and a2. Ganglion XXV in somite XXIV b6 and somite XXV a1. Ganglion XXVI in somite XXV b5 and b6. Posterior ganglionic mass in somite XXVI a1 and (a2 + a3).

Eyes in 3 pairs, 1st pair dorsally on somite II/III, 2nd and 3rd pairs dorsolaterally on posterior margin of somite V (a1 + a2) ( Fig. 2A View Figure 2 ). Papillae numerous, minute, hardly visible, 1 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 View Figure 2 ).

Pharynx agnathous, euthylaematous, reaching to somite XIV a1 ( Fig. 2G View Figure 2 ). Crop tubular, acecate, reaching to somite XIX b5/b6. Intestine tubular, reaching to XXIV b5/b6, with 1 pouch-shaped intestinal ceca on left side in XIX a2 and b5, opening in behind junction between crop and intestine in somite XIX b5/b6, then ascending to somite XIX a2. Rectum tubular, thin-walled, straight. Gastropore conspicuous, ventral, in middle of somite XIII a2 ( Fig. 2E, F View Figure 2 ). Gastroporal duct bulbous, slightly winding at junction with gastropore, reaching to somite XIV a2/b5 ( Fig. 2G View Figure 2 ).

Testisacs multiple in somite XX a2 to XXV a2 ( Fig. 3A View Figure 3 ); on each side, in total ~21 testisacs, 3 in XX, 4 in each somite of somites XXI–XXIV, 2 in XXV. Paired epididymides; right epididymis in somite XVIII a1/a2 to somite XIX/XX, occupying 7 annuli; left epididymis in somite XVIII a1 to somite XIX/XX, occupying 8 annuli ( Fig. 3A View Figure 3 ). Paired ejaculatory ducts; right duct in somite XI b5 to somite XVIII a1/a2; left duct in somite XI b5 to somite XVIII a1; coiled in position posterior to ovisacs; each duct crossing ventrally beneath each ovisac, then loosely coiled in position anterior to ovisacs; each widening from respective junction with epididymis, narrowing at junction with atrial cornua, then loosely turning proximally toward atrial cornua without preatrial loop ( Fig. 3A, B View Figure 3 ). Pair of muscular atrial cornua developed, ovate, in somite XI b5 and b6 ( Fig. 3A–D View Figure 3 ). Atrium short, muscular, globular in somite XI b5 and b6 ( Fig. 3B–D View Figure 3 ).

Paired ovisacs globular, in somite XIII a2 and b5 ( Fig. 3A, E View Figure 3 ). Oviducts thin-walled, left oviduct crossing ventrally beneath nerve cord ( Fig. 3A, E View Figure 3 ); both oviducts converging into common oviduct in somite XIII a1/a2. Common oviduct thin-walled, short, directly descending to female gonopore ( Fig. 3E View Figure 3 ).

Variation. Measurements (mean ± 1SD, followed by ranges in parentheses; n = 5, including holotype): BL 37.8 ± 9.6 mm (21.3–50.3 mm), BW 3.9 ± 1.1 mm (2.3– 5.1 mm), CL 1.9 ± 0.4 mm (1.2–2.4 mm), CW 2.4 ± 0.6 mm (1.4–2.8 mm). Somite XXVI triannulate a1 = a2 <a3; a3 being ventrally last complete annulus. Male gonopore slightly anterior to middle of somite XI b6, or in middle of somite XI b6. Female gonopore slightly anterior to middle of somite XIII a1, or in middle of somite XIII a1. Pharynx reaching to XIV a2. Crop reaching to somite XIX b5/b6– XIX/XX. Intestine reaching to somite XXIII/XXIV–XXIV a1. Gastroporal duct reaching to somite XIV a2–somite XIV b5/b6. Testisacs; right side ~26 sacs in somite XX b5 to somite XXV a1–b5; left side ~26 sacs in somite XX a2 to somite XXV a1–b6. Paired epididymides; right epididymis in somite XVII a2/b5–b6 to somite XIX b5–somite XX a2, occupying 9–11 annuli; left epididymis in somite XVII a2/ b5–b5/b6 to somite XIX b6–somite XX a1/a2, occupying 10 annuli. Paired ejaculatory ducts; right side in somite XI b5 to somite XVII a2/b5–b6; left side in somite XI b5 to somite XVII a2/b5–b5/b6; loosely coiled, or nearly straight in position anterior to ovisacs. Paired ovisacs in somite XIII a2 and b5, or in somite XIII a2–b6. Right or left oviduct crossing ventrally beneath nerve cord.

Coloration. In life, dorsal surface yellowish brown ( Fig. 1C View Figure 1 ); ventral surface whitish yellow; clitellum, when obvious, paler than other body parts ( Fig. 1C View Figure 1 ). Color faded in preservative.

Distribution. This species was collected only from Tsukuba Mountains.

Natural history. This species was found curled up under rocks or fallen leaves in moist habitats in the Tsukuba Mountains ( Fig. 1D View Figure 1 ). Because mature individuals bearing an obvious clitellum were collected on 22 May 2019 and 16 June 2014, it is estimated that the reproductive season of this species begins before early June.

Etymology. The specific name is a compound adjective in nominative singular derived from the Latin words, mons (mountain) and pumilus (dwarf), referring to the fact that this small-type new species inhabits Tsukuba Mountains.

Molecular phylogenetic position. The BI (mean ln L = −46390.05; Fig. 4 View Figure 4 ) and ML (ln L = −46373.90; not shown) trees had almost identical topologies, and very closely matched those of previous analyses ( Nakano 2018, Nakano & Prozorova 2019). Orobdella montipumila was clustered into a well-supported clade (BS = 80 %, PP = 0.99) that comprised seven other Orobdella species. This lineage was split into three clades. The first clade (BS = 100 %, PP = 1.0) comprised the middle-type sexannulate O. ijimai Oka, 1895 and the large-type octannulate O. octonaria Oka, 1895 , both of which are distributed in Honshu ( Nakano 2017a). The second clade (BS = 90 %, PP = 1.0) included the middle-type quadrannulate O. whitmani Oka, 1895 , the small-type quadrannulate O. masaakikuroiwai , the middle-type sexannulate O. okanoi Nakano, 2016b and O. yamaneae Nakano, 2016b , and the large-type octannulate O. nakahamai Nakano, 2016b ; while the former two species are indigenous to Honshu ( Nakano 2017a), the latter three species have been described from Shikoku and an adjacent islet ( Nakano 2016b). The last lineage comprised only O. montipumila . Precise relationships among the three clades could not be elucidated.

The respective COI (LC616660–LC616663), tRNACys –16S (LC616664–LC616667) and tRNALeu – ND1 (LC616668–LC616671) sequences, which were obtained from the holotype and three paratypes of O. montipumila , were almost concordant with each other. The present phylogenies certified that the holotype and three paratypes of O. montipumila belong to a single species (BS = 100 %, PP = 1.0).