Orobdella ibukifukuyamai, Nakano, 2022

Nakano, Takafumi, 2022, A new sexannulate species of Orobdella (Hirudinea, Arhynchobdellida, Orobdellidae) from Kii-Oshima Island, Japan, Evolutionary Systematics 6 (2), pp. 135-142 : 135

publication ID	https://dx.doi.org/10.3897/evolsyst.6.86308
publication LSID	lsid:zoobank.org:pub:4DE05AA8-7761-4DAF-B32A-739315B60D95
persistent identifier	https://treatment.plazi.org/id/824E7A4A-7FBC-49D7-B457-3EE3F40BBABA
taxon LSID	lsid:zoobank.org:act:824E7A4A-7FBC-49D7-B457-3EE3F40BBABA
treatment provided by	Evolutionary Systematics by Pensoft
scientific name	Orobdella ibukifukuyamai
status	sp. nov.

Treatment

Orobdella ibukifukuyamai sp. nov.

Figs 1 View Figure 1 , 2 View Figure 2 , 3 View Figure 3

Diagnosis.

Body length of mature individuals reaching ~15 cm. Somite VII quinquannulate, somites VIII-XXV sexannulate, b1 = b2 <a2 = b5> c11 = c12 (especially mid-body somites). Male gonopore in slightly anterior to middle of, or in middle of somite XI c12, female gonopore in somite XIII b2/a2, posterior to gastropore, gonopores separated by 1/2 + 8 annuli. Pharynx reaching to somite XIV a2/b5-b5. Gastropore conspicuous, in somite XIII b2/a2. Gastroporal duct thick tubular. Paired epididymides in somites XVI-XVIII, occupying 11-12 annuli. Atrial cornua developed, ovate, without pre-atrial loop. Dorsal surface reddish brown in life.

Material examined.

Holotype: Japan • Wakayama Prefecture, Kushimoto Town, Kii-Oshima Island, near Minato Shrine ; 33°28.3'N, 135°48.3'E; 20 Nov. 2021; I. Fukuyama leg.; KUZ Z4031 GoogleMaps . Paratype: Japan • same data as for holotype; KUZ Z4032 GoogleMaps .

Description

(based on the holotype KUZ Z4031). Body firm and muscular, elongate, with constant width in caudal direction, dorsoventrally compressed, BL 149.5 mm, BW 8.9 mm (Fig. 1A, B View Figure 1 ). Caudal sucker ventral, almost circular, CL 4.4 mm, CW 4.9 mm (Figs 1B View Figure 1 , 2C, D View Figure 2 ).

Somite I completely merged with prostomium. Somite II (= peristomium) uniannulate (Fig. 2A View Figure 2 ) Somites III-V biannulate (Fig. 2A View Figure 2 ): III and IV, (a1 + a2)> a3; V, (a1 + a2) = a3, a3 forming posterior margin of oral sucker (Fig. 2A, B View Figure 2 ). Somite VI triannulate, a1 (with obvious secondary furrow dorsally, b1 = b2)> a2 = a3 (Fig. 2A, B View Figure 2 ). Somite VII quinquannulate, b1 = b2 = a2 = b5 = b6 (Fig. 2A, B View Figure 2 ). Somites VIII-XXV sexannulate (Fig. 2A-E View Figure 2 ): VIII-XII, b1 = b2 = a2 = b5 = c11 = c12; XIII b1 = b2 <a2> b5 = c11 = c12; XIV and XV, b1 = b2 = a2 = b5 = c11 = c12; XVI-XVIII, b1 <b2 = a2 (b3 = b4 dorsally) = b5> c11 = c12 (Fig. 2E View Figure 2 ); XIX-XXII, b1 <b2 (c3 = c4 dorsally) = a2 (b3 = b4 dorsally) = b5> c11 = c12; XXIII and XXIV, b1 <b2 = a2 (b3 = b4 dorsally) = b5> c11 = c12; XXV and XXVI, b1 = b2 = a2 = b5 = c11 = c12. Somite XXVII dorsally quadrannulate, b1 = b2 = a2 <a3; b1 being ventrally last complete annulus (Fig. 2C, D View Figure 2 ). Anus posterior to somite XXVII; post-anal annulus absent (Fig. 2C View Figure 2 ).

Male gonopore slightly anterior to middle of somite XI c12 (Fig. 2F View Figure 2 ). Female gonopore in somite XIII b2/a2, inconspicuous, located posterior to gastropore (Fig. 2F, G View Figure 2 ). Gonopores separated by 1/2 + 8 annuli (Fig. 2F View Figure 2 ).

Anterior ganglionic mass in somite VI a2 and a3. Ganglion VII in somite VII b2. Ganglia VIII and IX, of each somite, in b2 and a2. Ganglia X and XI, of each somite, in a2 (Fig. 3B View Figure 3 ). Ganglia XII and XIII, of each somite, in b2 and a2 (Fig. 3B View Figure 3 ). Ganglion XIV in somite XIV a2 (Fig. 3B View Figure 3 ). Ganglion XV in somite XV b2 and a2 (Fig. 3B View Figure 3 ). Ganglion XVI in somite XVI a2 (Fig. 3B View Figure 3 ). Ganglia XVII-XXII, of each somite, in b2 and a2 (Fig. 3B View Figure 3 ). Ganglia XXIII and XXIV, of each somite, in a2. Ganglion XXV in somite XXV b2 and a2. Ganglion XXVI in somite XXVI b1 and b2. Posterior ganglionic mass in somite XXVI c11 and c12.

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

Nephridiopores in 17 pairs, each situated ventrally at posterior margin of b2 of each somite in somites VIII-XXIV (Fig. 2B, D, F View Figure 2 ).

Pharynx agnathous, euthylaematous, reaching to somite XIV a2/b5 (Fig. 3A View Figure 3 ). Crop tubular, acecate, reaching to somite XXI c11/c12. Intestine tubular, acecate, reaching to somite XXV b1/b2. Rectum tubular, thin-walled, straight. Gastropore conspicuous, ventral, in somite XIII b2/a2 (Fig. 2F, G View Figure 2 ). Gastroporal duct thick, tubular, slightly winding at junction with gastropore, reaching to somite XIV a2 and connecting with anteriormost part of crop (Fig. 3A View Figure 3 ).

Testisacs multiple in somite XIX b1 to XXV c12 (Fig. 3B View Figure 3 ); on right side, in total ~83 testisacs, 13 in XIX, 14 in XX, 13 in XXI, 11 in XXII, 12 in XXIII, 11 in XXIV, 9 in XXV; on left side, in total ~80 testisacs, 12 in XIX, 12 in XX, 13 in XXI, 14 in XXII, 11 in XXIII, 10 in XXIV, 8 in XXV. Paired epididymides; right epididymis in somite XVII b1 to somite XVIII/XIX, occupying 12 annuli; left epididymis in somite XVII b1/b2 to somite XVIII/XIX, occupying 11 annuli (Fig. 3B View Figure 3 ). Paired ejaculatory ducts; right duct in somite XI b5 to somite XVII b1; left duct in somite XI b5 to somite XVII b1/b2; coiled in position posterior to ovisacs; each duct crossing ventrally beneath each ovisac, then nearly straight in position anterior to ovisacs; each widening from respective junction with epididymis, narrowing at junction with atrial cornua, then turning proximally toward atrial cornua without pre-atrial loop (Fig. 3B, C View Figure 3 ). Pair of muscular atrial cornua developed, ovate, in somite XI b5-c12 (Fig. 3B-E View Figure 3 ). Atrium short, muscular, globular in somite XI c11 and c12 (Fig. 3C-E View Figure 3 ).

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

Coloration

(based on the holotype KUZ Z4031 and paratype KUZ Z4032). In life, dorsal surface reddish brown (Fig. 1C View Figure 1 ); lateral surface ocher; ventral surface whitish yellow. Color faded in preservative; dark mid-dorsal line present from somite VII b6 to somite XXVII only in paratype.

Variation

(based on the paratype KUZ Z4032). Measurements: BL 121.1 mm, BW 6.3 mm, CL 3.3 mm, CW 4.1 mm. Somites XVI-XXI sexannulate, b1 = b2 <a2 (b3 = b4 dorsally) = b5 (c9 = c10 dorsally)> c11> c12. Pharynx reaching to somite XIV b5. Crop reaching to somite XXI/XXII. Gastroporal duct reaching to somite XIV a2/b5. Intestine reaching to somite XXV b1. Paired epididymides in somite XVI b2/a2 to somite XVIII b1/b2, occupying 11 annuli. Paired ejaculatory ducts in somite XI b5 to somite XVI b2/a2; coiled in position anterior to ovisacs. Paired ovisacs; right ovisac in somite XIII a2-c11; left ovisac in somite XIII a2 and b5. Right oviduct crossing ventrally beneath nerve cord.

Etymology.

The specific name is dedicated to Mr Ibuki Fukuyama who collected the specimens of the new species.

Distribution.

This species was collected only from the type locality.

Molecular phylogenetic position and genetic distances.

The ML (Fig. 4 View Figure 4 ) and BI (not shown) trees had identical topologies, and were explicitly concordant with those of previous analyses (e.g., Nakano 2021). Orobdella ibukifukuyamai was placed within the clade that consists of the sexannulate O. yamaneae Nakano, 2016 and O. okanoi Nakano, 2016 and octannulate O. nakahamai Nakano, 2016. The monophyly of these four species was fully supported (BS = 100%, PP = 1.0). Within this clade, the monophyly of O. ibukifukuyamai and O. yamaneae was implied (BS = 64%, PP = 0.91); nonetheless, the present phylogenies failed to resolve robust relationships among the four species.

The pairwise COI uncorrected p -distance between the holotype and paratype of O. ibukifukuyamai was 0.2% (2/1267 nucleotides were polymorphic). The COI genetic divergence between O. ibukifukuyamai and the closely related O. yamaneae was 4.6-4.9% (mean = 4.7%); that between O. ibukifukuyamai and O. okanoi was 4.4-5.0% (mean = 4.7%) (Table 1 View Table 1 ). The COI genetic distance between O. okanoi and O. yamaneae was 5.8-6.0% (mean = 5.9%).

Remarks.

The morphological features (see Nakano 2016) as well as molecular phylogenetic position of O. ibukifukuyamai clearly elucidated that this new species belongs to the genus Orobdella . Only two specimens of the new species could be examined in this study, but nonetheless, their morphological characteristics and DNA sequences successfully ensured the distinct species status of O. ibukifukuyamai within Orobdella .

The new species is distinguishable from the six sexannulate congeners, O. dolichopharynx Nakano, 2011, O. ijimai Oka, 1895, O. mononoke Nakano, 2012, O. okanoi , O. shimadae Nakano, 2011, and O. yamaneae by the following combination of characteristics ( Nakano 2011, 2012, 2016; Table 2 View Table 2 ): dorsal surface reddish in life, quinquannulate somite VII, sexannulate somite VIII, 1/2 + 8 annuli between gonopores, pharynx reaching to somite XIV, thick tubular gastroporal duct, epididymides in somites XVI-XVIII that occupy 11-12 annuli, and developed ovate atrial cornua without pre-atrial loop. Orobdella ibukifukuyamai can be distinguished from the four sexannulate species, i.e., O. dolichopharynx , O. ijimai , O. mononoke and O. shimadae by its somite VII that is quinquannulate (quadrannulate in O. dolichopharynx , O. ijimai and O. mononoke , and triannulate in O. shimadae ). Additionally, O. ibukifukuyamai is distinguishable from O. dolichopharynx and O. shimadae by the developed gastroporal duct and atrial cornua (both organs are rudimentary in O. dolichopharynx and O. shimadae ). Orobdella ibukifukuyamai , O. okanoi and O. yamaneae shares several morphological features, i.e., a large body size reaching ~15 cm, a similar annulation pattern of somites VII and VIII, and a similar position of epididymides. However, O. ibukifukuyamai can be discriminated from O. okanoi and O. yamaneae by the reddish brown dorsal surface and ocher lateral surface, the possession of 1/2 + 8 annuli between the gonopores, and the ovate atrial cornua without pre-atrial loops (in O. okanoi , uniformly reddish dorsal to lateral surface, 1/2 + 8 annuli between gonopores, and ellipsoidal atrial cornua without pre-atrial loops; in O. yamaneae , uniformly purplish dorsal to lateral surface, 1/2 + 7 + 1/2 annuli between gonopores, and ovate atrial cornua each with slight pre-atrial loop). Orobdella ibukifukuyamai can be clearly distinguished from the quadrannulate and octannulate species, in which the closely related O. nakahamai is included (see Table 2 View Table 2 ), by its sexannulate mid-body somites.

The present molecular phylogenies recovered the close relationships among the three morphologically-similar sexannulate species, O. ibukifukuyamai , O. okanoi , and O. yamaneae . The calculated interspecific COI distances between O. ibukifukuyamai and O. okanoi (4.4-5.0%) was almost equal to those between O. ibukifukuyamai and O. yamaneae (4.6-4.9%). A previous study indicated that the COI divergences between the two closest species O. kanaekoikeae Nakano, 2017b and O. brachyepididymis Nakano, 2016, which are morphologically well-differentiated from each other, were 3.6-4.6% ( Nakano 2017b). Therefore, the present distance values can support the distinctive taxonomic status of O. ibukifukuyamai within the lineage that consists of the sexannulate Orobdella species. Additionally, the present phylogenies recovered the monophyly of the octannulate O. nakahamai and the three sexannulate species; the monophyly of O. nakahamai , O. okanoi and O. yamaneae has been already shown by previous studies (e.g., Nakano 2021). Given the fact that O. nakahamai possesses the octannulate mid-body somites denoted as b1 = b2 = b3 = b4 = c9 = c10 = c11 = c12, and O. ibukifukuyamai bears the sexannulate mid-body somites, of which annuli a2 and b5 are, respectively, subdivided dorsally, defined as b1 = b2 <a2 (b3 = b4 dorsally) = b5 (c9 = c10 dorsally)> c11 = c12, the new species may exhibit annulation that is the transitional state (= secondarily octannulate dorsally) between sexannulate and octannulate Orobdella species.