Orientocreadium elegans, Besprozvannykh, Vladimir V., Ermolenko, Alexey V. & Deveney, Marty R, 2009

Besprozvannykh, Vladimir V., Ermolenko, Alexey V. & Deveney, Marty R, 2009, Orientocreadium elegans n. sp. and Orientocreadium pseudobagri Ya m a g u t i (Digenea: Orientocreadiidae), from freshwater fish of the Primorsky region (southern far east, Russia) with a description of their life cycles, Zootaxa 2176, pp. 22-32 : 27-30

Orientocreadium elegans n. sp.

( Figs. 1 C, 1D, 2B, 2C, 2D, 4)

Materials examined. 7 mature worms.

Definitive host: Pelteobagrus fulvidraco ( Bagridae : Osteichthyes).

Site of infection: rectum.

Type habitat: middle part of the Ilistaja River (Khanka Lake basin) at approximately 44o23’N, 132o25’E.

Date of collection: 2003.21.0 7.

Type-deposition: Holotype No. 41- Tr, paratypes No. 42- Tr. & 43- Tr. This material is held in the collection of the Zoological Museum (Institute of Biology and Soil Sciences, Far East Branch of the Russian Academy of Sciences, Vladivostok, Russia); e-mail: [e-mail]. Deposited: 2007.22.0 6.

Adult description (holotype, Fig. 1 C): Body 1.7 mm × 200, no changes in width. Tegument covered with spines. Oral sucker subterminal, 123 × 117. Ventral sucker 123 × 110, located 600 from anterior end of body. Pharynx 61 × 72, with a cruciform indentation on distal surface. Prepharynx 150 long, oesophagus 67 long. Prepharynx and oesophagus width variable; some contained ingested material and were wider. Intestinal bifurcation anterior to anterior margin of ventral sucker. Caeca 2, terminate blindly near posterior end of body.

Testes 2, oval, tandem, in midline, 168 apart, in the posterior third of body; anterior testis 117 × 110; posterior testis 150 × 112. Cirrus sac 290 × 50 mm, seminal vesicle bipartite, external seminal vesicle large, between proximal end cirrus sac and anterior margin ovary, internal seminal vesicle small. Cirrus with small spines, lies in midline of body; passes anterodorsal to ventral sucker, opens into shallow genital atrium. Genital pore median, just anterior to ventral sucker, one third of body length posterior to anterior body margin.

Ovary single, entire, 112 × 84, located on midline of body, just posterior to middle of body, anterior to testes. Mehlis’ gland posterior to ovary, Laurer’s canal present. Uterus coiled, occupies entire area between posterior testis and posterior body margin. Seminal receptacle uterine. Metraterm 200 long, with small spines, opens into genital atrium. Eggs operculate, 31–36 × 17–20, embryonated in utero. Vitellarium follicular, fields lateral, extending from level of ovary or slightly anterior to ovary posteriorly to 2/3 distance between posterior testis and posterior margin of body; follicles medium-sized; left field longer than right; extends beyond anterior margin of ovary; vitelline extent similar in all worms examined; gap may occur at level of posterior testis.

Excretory vesicle Y-shaped, with anterior margin just posterior to posterior testis; excretory pore terminal.

Remarks: Orientocreadium elegans n. sp. has vitelline follicles that do not reach the end of the body, placing it in a group of species with O. pseudobagri , O. siluri and O. chaenogobii . It can be differentiated from these species by the shape and size of body (see Table 1 ): O. elegans n. sp. is longer and narrower than O. pseudobagri and shorter and narrower than O. siluri and O. chaenogobii . The oral and ventral suckers of O. elegans n. sp. are approximately the same size, whereas the oral sucker is smaller than ventral sucker in O. chaenogobii . The suckers of O. elegans n. sp. are smaller than those of all other species of Orientocreadium and the pharynx is smaller than those of O. siluri and O. chaenogobii . Our new species further differs from O. siluri by the presence of spines on the cirrus and inside the metraterm; it also differs in that the ovary is located in the posterior half of the body in O. elegans n. sp., but is located in the anterior part of the body in O. siluri . Orientocreadiium elegans n. sp. has a cirrus sac that lies on the median line of body dorsal to the ventral sucker, whereas the cirrus sac of O. pseudobagri passes laterally around the ventral sucker. The cercariae of O. elegans n. sp. are larger in all respects than those of O. pseudobagri . There are clear differences between the chaetotactic structures of the cercariae of O. pseudobagri and O. elegans n. sp. but these features are not described for other Orientocreadium spp., preventing broader comparisons.

First intermediate hosts: Gastropoda – Lymnaea coreana (Martens) (under natural conditions), L. ussuriensis (Kruglov & Starobogatov) (experimentally) ( Lymnaeidae ).

Sporocyst: sac-shaped, 0.38–0.67 × 0.12–0.13 mm, birth pore terminal.

Site of infection: digestive gland.

Cercaria ( Fig. 2 B): body oval, 220–290 × 130–150, spines from anterior margin to level of ventral sucker. Eyespots absent. Oral sucker 45–60 × 45–53, stylet 22 × 3–5. Oesophagus shorter than prepharynx. Pharynx spherical, 25–34 in diameter. Intestinal bifurcation at level of anterior margin of ventral sucker. Caeca 2, short, terminating blind near middle of ventral sucker. Three pairs of penetration glands both sides of ventral sucker; ducts open laterally to stylet. Ventral sucker 42–56 × 45–53, 100–120 from anterior body margin. Genital primordia between ventral sucker and Y-shaped excretory bladder. Flame cell formula: 2[(3+3+3)+(3+3+3)]=36. Tail 0.16–0.22 х 0.031–0.035 mm. Sensory apparatus ( Fig. 4 ): CI= 1V 1, 5 V2, 1 V3; CII= 1V 1, 1 V2; 1V 3, 1 V4; CIII= 2V 1, 2 V2, 2 V3; CIV= 2V 1, 3 V2, 4 V3; St= 26V, 8–9D1, 2L1, 8D2, 5D3; AI=1– 2 V, 3L, 1D; AII= 1V, 2L, 1D; AIII=2D, 2L; M= 2V, 2–6D; PIII= 2V, 2D; S=9S1, 5S2; U=2.

Pattern of emergence: The patterns of emergence and host-finding behaviours of the cercariae of O. elegans n. sp. and O. pseudobagri are identical.

Second intermediate hosts (shown experimentally): Gastropoda - Anisus centrifugops Prosorova & Starobogatov and Helicorbis sujfunensis (Planorbidae) , Cipangopaludina ussuriensis (Bellamyidae) , Bivalvia – Pisidiidae g.sp.; Osteichthyes - Perccottus glehni (Eleotridae) , Pseudorasbora parva (Schlegel) (Cyprinidae) ; Amphibia - Rana dybowskii , juv. ( Ranidae ).

Metacercaria ( Fig. 2 C, D): cyst thin walled, transparent, oval or rounded, 150–160 × 130–150 mm. Metacercaria body 220 × 110–130, covered with spines. Oral sucker 53 × 59 mm, prepharynx and oesophagus well-developed. Pharynx diameter 22–25, cruciform indentation on terminal surface. Ventral sucker rounded, diameter 42–48 mm. Caeca short. 10 (glandular?) ducts open at anterior end of body; glands not observed. Excretory bladder with granular content. Stylet lost in development to the adult stage, stylet observed inside cyst post-penetration.

Site in host: muscles and mesenteries.

Figures

FIGURE 4. Arrangement of the sensillae of the cercaria of Orientocreadium elegans n. sp..

FIGURE 1. A. Orientocreadium pseudobagri from Perccottus glehni, adult, ventral view. B. Orientocreadium pseudobagri from Pelteobagrus fulvidraco, adult, ventral view. C. Orientocreadium elegans n. sp., holotype. D. Orientocreadium elegans n. sp., paratype. E. Cirrus sac of Orientocreadium pseudobagri.

FIGURE 2. A. Cercaria of Orientocreadium pseudobagri from Lymnaea coreana, ventral view. B. Cercaria of Orientocreadium elegans n. sp. from Lymnaea coreana, ventral view. C. Metaercaria of Orientocreadium elegans n. sp. from Phoxinus lagowskii, ventral view. D. Metacercaria of Orientocreadium elegans n. sp. from Pseudorasbora parva, ventral view.

Tables

TABLE 1. Measurements of adult specimens of Orientocreadium spp. (in Μm).

O. pseudobagri ex Perccottus glehni (n=5)	ex Pseudobagrus fulvidraco (n=5)	O. elegans n. sp. (7 specimens)	O. siluri (from Skrjabin, 1954; Skrjabin & Koval, 1963)	O. chaenogobii (from Shimazu, 1990)
Body 890–1330 × 190–290	1170–1470 × 220–280	960–1900 × 150–220	1000–2500 × 260–480	990–2130 × 460–630
Oral sucker 112–150 × 110–134	Ø 112–134	95–123 × 89–117	110–190 × 130–200	120–200 × 130–200
Ventral sucker Ø 112–140	Ø 0.112–0.140	84–123 × 89–117	Ø 120–190	140–240 × 150–260
Prepharynx length 44–67	67–84	78–150	70–150	50–90
Pharynx 56–67 × 61–78	61–78 × 78–84	56–61 × 61–84	Ø 0.080–0.120	60–110 × 90–120
Oesophagus length 61–72	39–72	45–67	–	30–80
Anterior testis Ø 95–127	127–168 × 110–134	84–123 × 84–134	160–190 × 170–180	80–270 × 120–240
Posterior testis 110–150 × 110–127	140–200 × 145–160	84–150 × 84–140	160–190 × 170–180	80–270 × 120–240
Ovary 84–123 × 84–140	112 × 110–145	67–117 × 67–112	Ø 150–170	190 × 140–200
Cirrus sac 200–230 × 56–67	220–300 × 50–61	210–300 × 45–56	–	200–350 × 60–90
From anterior end of body to:
Ventral sucker 290–390	390–470	350–600	–	–
Anterior testis 500–760	730–820	630–1140	–	–
From posterior end of body to:
Ventral sucker 490–810	660–850	530–1160	–	–
Posterior testis 200–290	180–260	180–400	–	–
Nearest vitelline 100–190 follicle	78–160	78–180	–	–