taxonID	type	description	language	source
03B0C1120003E53BFEADF910FF22FE55.taxon	description	(Figs 1 – 4)	en	Lai, Takafumi Nakano and Yi-Te (2025): A New Small-Sized Species of Orobdella (Hirudinea: Erpobdelliformes: Orobdellidae) from Mount Hehuan, Central Taiwan. Species Diversity 30 (2): 127-134, DOI: 10.12782/specdiv.30.127, URL: https://doi.org/10.12782/specdiv.30.127
03B0C1120003E53BFEADF910FF22FE55.taxon	diagnosis	Diagnosis. Body length of mature individuals reaching ~ 3 cm. Somite IV uniannulate, somites VIII – XXV quadrannulate. Male gonopore in middle of somite XI b 6, female in middle of somite XIII a 1, behind gastropore, gonopores separated by 1 / 2 + 4 + 1 / 2 annuli. Pharynx reaching to somite XIII / XIV. Gastropore conspicuous, in middle of somite XIII a 1. Gastroporal duct bulbous. Paired sperm duct bulbs, minute, in somite XVIII b 6 – XIX a 1. Paired epididymides in somites XVI – XVIII, occupying 10 – 11 annuli. Atrial cornua developed, ovate.	en	Lai, Takafumi Nakano and Yi-Te (2025): A New Small-Sized Species of Orobdella (Hirudinea: Erpobdelliformes: Orobdellidae) from Mount Hehuan, Central Taiwan. Species Diversity 30 (2): 127-134, DOI: 10.12782/specdiv.30.127, URL: https://doi.org/10.12782/specdiv.30.127
03B0C1120003E53BFEADF910FF22FE55.taxon	materials_examined	Material examined. Holotype: KUZ Z 1471, dissect- ed, near High Altitude Experimental Station of Endemic Species Research Institute, Hehuanshan National Forest Recreation Area, Renai Township, Nantou County, Taiwan (24.16203 ° N, 121.28622 ° E; elev. 2960 m), by Yi-Te Lai, 9 February 2013. Paratype: ASIZW 0001115, dissected, same locality and collector as for holotype (24.16439 ° N, 121.28571 ° E; elev. 2900 m), 21 March 2019.	en	Lai, Takafumi Nakano and Yi-Te (2025): A New Small-Sized Species of Orobdella (Hirudinea: Erpobdelliformes: Orobdellidae) from Mount Hehuan, Central Taiwan. Species Diversity 30 (2): 127-134, DOI: 10.12782/specdiv.30.127, URL: https://doi.org/10.12782/specdiv.30.127
03B0C1120003E53BFEADF910FF22FE55.taxon	description	Description. Body firm and muscular, elongate, with constant width in caudal direction, dorsoventrally compressed, BL 31.7 mm, BW 2.8 mm (Fig. 1 A, B). Caudal suck- er ventral, elliptic, CL 1.2 mm, CW 1.4 mm (Figs 1 B, 2 D). Somite I completely merged with prostomium. Somite II (= peristomium), III, IV uniannulate (Fig. 2 A). Somite V biannulate, (a 1 + a 2) = a 3; a 3 forming posterior margin of oral sucker (Fig. 2 A, B). Somites VI and VII triannulate, a 1 = a 2 = a 3 (Fig. 2 A, B). Somites VIII – XXV quadrannulate, a 1 = a 2 = b 5 = b 6 (Fig. 2 A – E). Somite XXVI triannulate, a 1 = a 2 <a 3; a 3 being ventrally last complete annulus (Fig. 2 C, D). Somite XXVII uniannulate (Fig. 2 C). Anus behind somite XXVII; post-anal annulus absent (Fig. 2 C). Male gonopore in middle of somite XI b 6 (Fig. 2 E). Female gonopore in middle of somite XIII a 1, inconspicuous, located posterior to gastropore (Fig. 2 E, F). Gonopores separated by 1 / 2 + 4 + 1 / 2 annuli (Fig. 2 E). Anterior ganglionic mass in somite VI a 2 and a 3 and somite VII a 1. Ganglion VII in a 2 and a 3. Ganglia VIII – XV and XIX, of each somite, in a 2 and b 5 (Fig. 3 B). Ganglia XVI – XVIII and XX – XXIII, of each somite, in a 2 (Fig. 3 B). Ganglion XXIV in a 1 and a 2. Ganglion XXV in somite XXIV b 6 and somite XXV a 1. Ganglion XXVI in somite XXV b 5. Posterior ganglionic mass in somite XXV b 6 and XXVI a 1 and a 2. Eyes in 3 pairs, 1 st pair dorsally, slightly anterior to middle of somite III, 2 nd and 3 rd pairs dorsolaterally on posterior margin of somite V (a 1 + a 2) (Fig. 2 A). Papillae numerous, minute, hardly visible, 1 row on every annulus. Nephridiopores in 17 pairs, each situated ventrally at posterior margin of a 1 of each somite in somites VIII – XXIV (Fig. 2 B, D, E). Pharynx agnathous, euthylaematous, reaching to somite XIII / XIV (Fig. 3 A). Crop tubular, acecate, reaching to somite XX a 1 / a 2. Intestine tubular, reaching to XXIV a 2 / b 5. Rectum tubular, thin-walled, straight. Gastropore conspicuous, ventral, in middle of somite XIII a 2 (Fig. 2 E, F). Gastroporal duct thick, bulbous, winding at junction with gastropore, reaching to somite XIV a 1 (Fig. 3 A). Testisacs multiple (Fig. 3 B); on right side, in somite XIX a 2 to somite XXV a 1, in total ~ 22 testisacs, 3 in XIX, 2 in XX, 4 in each somite of XXI – XXIV, 1 in XXV; on left side, in somite XIX b 6 to somite XXIV b 6, in total ~ 20 testisacs, 1 in XIX, 4 in each somite of XX – XXIII, 3 in XXIV. Paired sperm duct bulbs minute; on right side, in somite XVIII b 6; on left side, in somite XIX a 1 (Fig. 3 B). Paired epididymides; right epididymis in somite XVI a 1 to somite XVIII b 5 / b 6, Partition Model 18 S and H 3 1 st position K 80 + I 28 S and H 3 2 nd position GTR + I + G H 3 3 rd position HKY + G COI and ND 1 1 st positions GTR + I + G COI and ND 1 2 nd positions GTR + I + G COI and ND 1 3 rd positions and 16 S GTR + I + G tRNACys – tRNAVal * and tRNALeu GTR + I + G occupying 11 annuli; left epididymis in somite XVI a 1 / a 2 to somite XVIII / XIX, occupying 11 annuli (Fig. 3 B). Paired ejaculatory ducts in somite XI b 5 to somite XVI a 1; coiled in position posterior to ovisacs; each duct crossing ventrally beneath each ovisac, then coiled in position anterior to ovisacs; each widening from respective junction with epididymis, narrowing at junction with atrial cornua, then sharply turning proximally toward atrial cornua without pre-atrial loop (Fig. 3 B). Pair of muscular atrial cornua developed, ovate, in somite XI b 5 and b 6 (Fig. 3 B – E). Atrium short, muscular, globular in somite XI b 5 and b 6 (Fig. 3 C – E). Paired ovisacs globular, in somite XIII a 2 and b 5 (Fig. 3 B, F). Oviducts thin-walled, left oviduct crossing ventrally beneath nerve cord (Fig. 3 B, F); both oviducts converging into common oviduct in somite XIII a 2. Common oviduct thin-walled, short, directly descending to female gonopore (Fig. 3 F). Variation. Measurements (n = 1, paratype only): BL 26.8 mm, BW 2.5 mm, CL 1.0 mm, CW 1.2 mm. Crop reaching to somite XIX / XX. Intestine reaching to somite XXIII a 2 / b 5. Testisacs; on right side, ~ 14 sacs in somite XIX a 2 to somite XXIV b 5; on left side, ~ 12 sacs in somite XIX a 2 to somite XXIV b 6. Paired sperm duct bulbs (Fig. 4); right bulb in somite XIX a 1; left bulb in somite XVIII b 6. Paired epididymides; right epididymis in somite XVI b 5 to somite XVIII / XIX, occupying 10 annuli; left epididymis in somite XVI a 1 / a 2 to somite XVIII b 6, occupying 11 annuli. Paired ejaculatory ducts; right duct in somite XI b 5 to somite XVI b 5; left duct in somite XI b 5 to somite XVI a 1. Paired ovisacs in somite XIII a 1 – b 6. Right oviduct crossing ventrally beneath nerve cord. Coloration. In life, dorsal surface bluish gray (Fig. 1 C); ventral surface yellowish or grayish white. Color faded in preservative.	en	Lai, Takafumi Nakano and Yi-Te (2025): A New Small-Sized Species of Orobdella (Hirudinea: Erpobdelliformes: Orobdellidae) from Mount Hehuan, Central Taiwan. Species Diversity 30 (2): 127-134, DOI: 10.12782/specdiv.30.127, URL: https://doi.org/10.12782/specdiv.30.127
03B0C1120003E53BFEADF910FF22FE55.taxon	distribution	Distribution and natural history. This species was collected only from the high-elevation area of Mt. Hehuan in the Central Mountain Range of Taiwan. Because both specimens possessing fully developed genital organs were collected in February and March, we estimate that the reproductive season of this species begins after March at the type locality. Molecular phylogenetic position. The ML (not shown) and BI (Fig. 5) trees had almost identical topologies, and were concordant with those of previous analyses (e. g., Nakano 2025). Orobdella minima formed a well-supported clade with the Taiwanese O. ketagalan Nakano and Lai, 2012 and O. meisai Nakano and Lai, 2017 (BS = 99 %, PP = 1.0). The monophyly of O. minima and O. ketagalan was fully supported (BS = 100 %, PP = 1.0).	en	Lai, Takafumi Nakano and Yi-Te (2025): A New Small-Sized Species of Orobdella (Hirudinea: Erpobdelliformes: Orobdellidae) from Mount Hehuan, Central Taiwan. Species Diversity 30 (2): 127-134, DOI: 10.12782/specdiv.30.127, URL: https://doi.org/10.12782/specdiv.30.127
03B0C1120003E53BFEADF910FF22FE55.taxon	etymology	Etymology. The specific name is given based on its small body size, which is likely to be the smallest Orobdella species in Taiwan.	en	Lai, Takafumi Nakano and Yi-Te (2025): A New Small-Sized Species of Orobdella (Hirudinea: Erpobdelliformes: Orobdellidae) from Mount Hehuan, Central Taiwan. Species Diversity 30 (2): 127-134, DOI: 10.12782/specdiv.30.127, URL: https://doi.org/10.12782/specdiv.30.127
03B0C1120003E53BFEADF910FF22FE55.taxon	discussion	Remarks. Orobdella minima clearly belongs to the genus Orobdella because this new species possesses the generic diagnostic characteristics defined by Nakano (2016). The obtained trees also corroborate that this new species is explicitly classified as a member of this genus. The clitellum was not observed in any of the present specimens of O. minima, but nonetheless, they possessed fully developed male and female genital organs. Additionally, the body length of both individuals was up to ~ 3 cm. Therefore, we concluded that O. minima can be determined as a small-type species within Orobdella. Orobdella minima differs from the nine sexannulate and two octannulate species by its mid-body somites, which are quadrannulate. Except for O. ketagalan, O. minima is clearly distinguishable from the 14 quadrannulate congeners by the possession of paired sperm duct bulbs (vs. without sperm duct bulbs in 14 congeners; see Nakano and Prozorova 2024). Orobdella minima is readily distinguished from O. ketagalan by the presence of epididymides, which are absent in the latter. It also differs in having a developed bulbous gastroporal duct and ovate, well-developed atrial cornua (vs. a simple tubular duct and undeveloped coniform cornua in O. ketagalan) (cf. Nakano and Lai 2012). The present phylogenies recovered the monophyly of three Taiwanese quadrannulate species, O. minima, O. ketagalan, and O. meisai. Additionally, O. minima formed a clade with the middle-type O. ketagalan, and this clade was sister to the middle-type O. meisai. A previous study stated that the small-sized body length has evolved in parallel within the Japanese Orobdella (Nakano 2016, 2021). The obtained trees confirmed that the small body length has also evolved independently in the Taiwanese Orobdella. The present results also suggested that O. minima would retain the epididymides as a plesiomorphic feature among the Taiwanese Orobdella, because both O. ketagalan and O. meisai do not possess epididymides in their male genital organs (Nakano and Lai 2012, 2017). The absence of epididymides is not limited to O. ketagalan and O. meisai, but also observed in O. shimadae Nakano, 2011 and O. dolichopharynx Nakano, 2011 from the central Ryukyu Islands, which formed a monophyletic group with the Taiwanese species (Fig. 5). These two Ryukyu species also possess rudimentary gastroporal ducts (Nakano 2011). Given that the gastroporal duct serves as the spermatophore-receiving organ (Nakano 2017 b), this combination may suggest a functional relationship between a reduced or undeveloped gastroporal duct and the absence of epididymides. Supporting this idea, O. kawakatsuorum Richardson, 1975 and O. brachyepididymis Nakano, 2016, from Hokkaido and Shikoku, Japan, respectively, possess simple, tubular gastroporal ducts and also retain only short epididymides (Nakano 2012, 2016). Thus, although exceptions may exist, the presence and degree of development of epididymides may be functionally linked to the morphology of the gastroporal duct, potentially reflecting variations in spermatophore formation or copulatory behavior across species. Furthermore, the phylogenetic position of the new species suggested that the possession of sperm duct bulbs may be a synapomorphic character between O. minima and O. ketagalan that formed a fully supported clade within the genus.	en	Lai, Takafumi Nakano and Yi-Te (2025): A New Small-Sized Species of Orobdella (Hirudinea: Erpobdelliformes: Orobdellidae) from Mount Hehuan, Central Taiwan. Species Diversity 30 (2): 127-134, DOI: 10.12782/specdiv.30.127, URL: https://doi.org/10.12782/specdiv.30.127
