Monocotylidae Taschenberg, 1879

Nitta, Masato, 2019, A New Monocotylid Species, Neoheterocotyle quadrispinata n. sp. (Monogenea), Infecting Gills of Rhinobatos hynnicephalus in Japan, Species Diversity 24, pp. 145-150 : 146-149

Monocotylidae Taschenberg, 1879

[Tamban-chū-ka]

Heterocotylinae Chisholm, Wheeler, and Beverley-Burton, 1995 [New Japanese name: Iban-chū-a-ka]

Neoheterocotyle Hargis, 1955

[New Japanese name: Toge-iban-chū-zoku]

Neoheterocotyle quadrispinata n. sp.

[New Japanese name: Yotsu-toge-iban-chū]

( Figs 1 , 2 )

Holotype. Adult (NSMT-Pl 6381) collected from off Ōsaki-kami-jima island on 24 September 2015.

Paratypes. Fourteen specimens (NSMT-Pl 6382, 6383)

from off Ōsaki-kami-jima island on 25 July 2014; fifteen specimens (NSMT-Pl 6384) from off Tsuyazaki Port on 3 July 2016.

Description. Body ( Fig. 1A ) including haptor 625–1475 (996; n=11) long, 218–480 (349, n=11) wide at level of germarium. Head organs ten pairs (n=10), located along anterior margin of head. Four pairs of anterior ventral sac present. Eyespots dispersed over dorsal body surface between mouth and pharynx. Mouth ventral, subterminal. Pharynx muscular, spherical to oval, 99–237 (175, n=11) long, 55– 132 (85, n=11) wide. Esophagus not present, bifurcate intestine extending to end of body along each body margin. Pharyngeal glands present on either side of posterior part of pharynx.

Haptor elliptical, length 239–337 (296, n=11), width 269–379 (316, n=11), ventral surface of haptor with 1 central and 7 peripheral loculi. Pair of hamuli ( Fig. 1B ), length 55–69 (63, n=25). Single sinuous ridge present on ventral surface of all septa. Fourteen hooklets ( Fig. 1C ), length 10–12 (11, n=25), located in marginal valve as illustrated ( Fig. 1A ). Two pairs of fang-shaped, haptoral accessory sclerites of unequal size present on dorsal surface of haptor. Larger pair ( Fig. 1D ) length 28–44 (37, n=25), base width 15–27 (21, n=25), located on dorsal surface of posterior loculus. Smaller pair ( Fig. 1E ) length 18–33 (24, n=25), base width 9–20 (14, n=25), dorsal to each posterolateral loculi. Larger pair length to smaller pair length ratio, 1: 0.55–0.78; base ratio, 1: 0.56–0.88.

Testis single, with sinuous folds, posterior to germarium, 58–210 (161, n=10) long, 104–229 (156, n=10) wide. Vas deferens arising from anterior portion of testis, extending anteriorly and dorsal to vagina. Seminal vesicle located ventral over ejaculatory bulb, connected to right side of ejaculatory bulb ( Fig. 2 ). Ejaculatory bulb ( Fig. 2 ) muscular, oval, length 60–102 (79, n=11), width 35–68 (48, n=11). Male accessory glands enter posterior part of ejaculatory bulb. Sclerotized male copulatory organ consisting of penis and accessory piece ( Fig. 1F ). Penis curved proximally, length 88–113 (98, n=27), with accessory piece associated with most of entire length. Accessory piece slightly curved, with blade-shaped process on outside in distal, 77–101 (87, n=27) long.

Germarium dextral to body mid-region, elongate, wrapping around right intestine. Oötype length 68–149 (112, n=9), opening ventrally at unarmed common genital pore located lower left of ejaculatory bulb. Vaginal pore opening on left side of ventral body surface at level of base of ejaculatory bulb. Unsclerotized muscular vagina, 94–244 (150, n=9) long, 48–127 (87, n=9) wide, expanding middle part, connecting seminal receptacle through thin tube. Seminal receptacle 23–35 (29, n=7) long, 25–45 (30, n=7) wide. Vitellarium approximately co-extensive with intestine. Transverse vitelline duct lying at level of base of oötype.

Type host. Rhinobatos hynnicephalus ( Rhinopristiformes : Rhinobatidae ).

Type locality. Off Ōsaki-kami-jima island, Ōsaki-kamijima town, Hiroshima Prefecture, in the Seto Inland Sea (34°14′N, 132°48′E) .

Other locality. Off Tsuyazaki Port , Fukutsu city, Fukuoka Prefecture, in Genkai-nada, south Sea of Japan (33°47′N, 130°24′E) .

Site of infection. Gill filaments.

Etymology. The species name quadrispinata is from quadri (Latin), four, and spinata (Latin), spiny, referring to the two pairs of the haptoral accessory sclerites.

Japanese name. Ijima (1918) translated Heterocotylea as “Iban-a-moku” (a-moku means suborder), and the name is used for the new Japanese names “Iban-chū-a-ka” and “Toge-iban-chū-zoku” (“chū”, “a-ka”, and “zoku” mean worms, a subfamily, and a genus, respectively). The part of the new Japanese generic name, “toge” refers to the haptoral accessory sclerites, and the part of the new Japanese name of the species is “yotsu-toge” which refers to the two pairs of the haptoral accessory sclerites.

Sequence data. The newly generated sequence of the 28S rDNA (858 bp) and CO1 (890 bp) were submitted to DDBJ (accession nos. LC428038 and LC469716 , respectively) .

Molecular data comparison. BLAST searches of the sequences did not have any identical hit. The closest hits of newly generated sequence of the 28S rDNA are Troglocephalus rhinobatidis Young, 1967 ( AF348364 and AF026110 , 90.2% and 89.9% similarity with 99% and 98% coverage, respectively), Neoheterocotyle rhinobatidis ( Young, 1967) ( AF026107 and AF348361 , 89.8% and 89.2% similarity with 98% and 99% coverage, respectively), Neoheterocotyle rhynchobatis (Tripathi, 1959) ( AF348363 , 89.2% similarity with 99% coverage), and Neoheterocotyle rhinobatis (Pillai and Pillai, 1976) ( AF348362 , 88.1% similarity with 99% coverage). The closest hits of newly generated sequence of the CO1 are Benedenia cf. seriolae FAS-2013 ( KC633872 – 633877, 76.6–78.7% similarity with 45–59% coverage). Two registered sequences of Neoheterocotyle rhinobatidis ( AF026107 and AF348361 ) show 92.7% similarity with 100% coverage.

Remarks. This new species corresponds to the diagnostic characteristics of the genus Neoheterocotyle ( Chisholm 1994) . Currently, with the inclusion of the new species, 12 species of Neoheterocotyle are regarded as valid: N. bychowskyi ( Timofeeva, 1981) ; N. darwinensis Chisholm and Whittington, 2000 ; N. djiddensis (Pillai and Pillai, 1976) ; N. forficata ( Timofeeva, 1981) ; N. inpristi Hargis, 1955 ; N. ktarii Neifar, Euzet, and Ben Hassine, 2001 ; N. nagibinae ( Timofeeva, 1981) ; N. quadrispinata n. sp.; N. rhinobatidis ; N. rhinobatis ; N. rhynchobatis ; and N. robii Vaughan and Chisholm, 2010 ( Chisholm and Whittington 1997, 2000; Neifar et al. 2001; Vaughan and Chisholm 2010). Neoheterocotyle quadrispinata n. sp. having two pairs of dorsal haptoral accessory sclerites differs from the other Neoheterocotyle species , except N. forficata and N. rhinobatidis ( Hargis 1955; Young 1967; Timofeeva 1981; Chisholm 1994; Chisholm and Whittington 1997, 2000; Liu 2001; Neifar et al. 2001; Vaughan and Chisholm 2010). The penis is curved proximally and covered almost the entire length by the accessory piece having a blade-shaped process in N. quadrispinata n. sp., whereas the accessory piece of N. forficata is associated with the distal half of the penis and lacks a process, the penis of N. rhinobatidis is straight, and its accessory piece has no blade-shaped process ( Young 1967; Timofeeva 1981; Chisholm and Whittington 1997; Liu 2001). Furthermore, dorsal haptoral accessory sclerites of N. forficata are all similar in shape and size ( Chisholm and Whittington 1997), but those of N. quadrispinata n. sp. are unequal size ( Fig. 1D, E ).

Figures

Fig. 1. Neoheterocotyle quadrispinata n. sp. Holotype (NSMT-Pl 6381) for A, paratypes (NSMT-Pl 6383) for B–F. A, whole mount (ventral view); B, hamulus; C, hooklet; D, sclerotized haptoral accessory sclerite associated with posterior loculus; E, sclerotized haptoral accessory sclerite associated with posterolateral loculus; F, male copulatory organs (from two specimens, left: ventral view, right: dorsal view). Scale bars: A, 200µm; B, D–F; 20µm, C, 10µm. Abbreviations for morphological characters: ap, accessory piece; amg, anteromedian gland; cgp, common genital pole; dh, dorsal haptoral accessory structure; ej, ejaculatory bulb; ey, eyespots; g, germarium; h, hamulus; ho, hooklet; in, intestine; m, mouth; mag, male accessory gland; mco, male copulatory organ; o, oötype; od, oviduct; p, penis; ph, pharynx; phg, pharyngeal glands; r, sinuous ridge; s, anterior ventral sac; sr, seminal receptacle; sv, seminal vesicle; t, testis; tv, transverse vitelline duct; v, vagina; vd, vas deferens; vi, vitellaria; vo, vaginal opening. Abbreviations for measurements of hard parts: apl, accessory piece length; asl, haptoral accessory sclerite length; asw, haptoral accessory sclerite base width; hl, hamulus length; hol, hooklet length; pl, penis length.

Fig. 2. Light micrograph of ejaculatory bulb of Neoheterocotyle quadrispinata n. sp. (NSMT-Pl 6382, dorsal view). Scale bar: 30µm. Abbreviations: ap, accessory piece; ej, ejaculatory bulb; p, penis; mag, male accessory gland; sv, seminal vesicle.