Choanocotyle platti Tkach et Snyder, 2007

Type host:

Chelodina rugosa Ogilby, 1890

Localities

Type locality:Small billabong at Daly River Mango Farm, near Nauiyu Community, Northern Territory, Australia, 13° 44.302’S, 130° 40.838’E.

Other localities:Daly River, near Oolloo Crossing, Northern Territory, Australia, 14° 00.31’S, 131° 14.46’E; Mary River, Opium Creek Station, Northern Territory, Australia, 12° 34.62’S, 131°43.48’E.

Type specimens:

Holotype: Queensland Museum (QM) no. G228974 (labeled: ex. Chelodina rugosa, Daly River, Northern Territory, Australia, June 2005, SDS-05-53A). Paratypes: QM nos. G228975, G228976 (labeled: ex. Chelodina rugosa, Daly River, Northern Territory, Australia, June 2005, SDS-05-53A), and nos. G228977, G228978 (labeled: ex. Chelodina rugosa, Mary River, Opium Creek Station, Northern Territory, Australia, June 2005, SDS-04-59A). Paratypes: Harold W. Manter Laboratory (HWML) no. HWML48612 (6 slides labeled: ex. Chelodina rugosa, Daly River, Northern Territory, Australia, June 2005, SDS-05-32A).

GenBank number: EU196355.

Description (after Tkach and Snyder, 2007)

Body elongate, 6510; body width at level of ventral sucker 410. Tegument heavily spinose anteriorly, decreasing posteriorly, with smallest spines sparsely distributed at posterior end. Oral sucker very wide, 1020, incised ventrally, much wider than forebody when fully expanded; shape variable, occasionally funnel-shaped when retracted. Oral sucker surface aspinose. Prepharynx 280 long. Posterior part of esophagus folded in all specimens, looks like a pair of lateral diverticula (Fig. 1). Pharynx oval, 190 x 180. Esophagus short, 70, surrounded by unicellular glands. Cecal bufurcation 750 from anterior end of body. Thin-walled ceca extend to posterior end. Ventral sucker round, 220 x 210; distance from center of ventral sucker to anterior end 2200; ventral sucker from anterior end as percent of total body length 31.5. Oral : ventral sucker width ratio 4.86 : 1. Area anterior of ventral sucker aspinose. Under scanning electron microscopy two rings of sensory papillae observed on ventral sucker, the outer ring consists of six papillae and the inner ring consists of nine papillae (Fig. 2).
Common genital pore located ventrally at posterior margin of ventral sucker. Dorsal protuberance large, raised; located medially on dorsal surface posterior to ovarian complex. Ovary spherical to oval 180 x 170, median, approximately 2/3 of body length from anterior end, 2290 from posterior end. Seminal receptacle oval, 65 x 80, postero-sinistral and dorsal to ovary, usually slightly overlapping it. Mehlis’ gland large, posterior to ovary. Laurer’s canal opens dorsally at anterior margin of dorsal protuberance. Uterus intercecal, between ovary and ventral sucker. Distal portion of uterus passes dorsal to cirrus sac and ventral sucker, looping posteriorly along left margin of ventral sucker before entering genital atrium. Vitelline follicles small, scattered in posterior quarter of body; extending from posterior extremity anteriorly to posterior margin of ovary. Testes, oval, tandem, entire, in posterior quarter of body. Anterior testis 210 x 170; posterior testis 230 x 170; distance between testes 520 (separated by approximately 2 testis lengths); distance from posterior testis to posterior end of body 620. Cirrus sac length 730, maximum width 150, overlapping ventral sucker dorsally and curving posteriorly, entering genital atrium posterior to uterus. Bottom of cirrus sac at 420 from posterior margin of ventral sucker. Cirrus sac contains seminal vesicle, pars prostatica, cirrus. Bipartite seminal vesicle occupies approximately one-fourth of the cirrus sac length. Pars prostatica glandular; cirrus unarmed, evaginated cirrus not observed. Excretory bladder elongate, intracaecal, extending almost to ovary; excretory pore terminal. Eggs operculate; fully formed eggs in distal part of uterus 40 x 20.

Illustrations

Choanocotyle platti A, B, D, E. Holotype. C. Paratype. A. Overall view. B, C. Fully everted oral suckers. D. Posterior end of the body with vitellarium not shown. E. Distal parts of male and female reproductive system and ventral sucker. Scale-bars: A, D - 1 mm, B, C - 0. 5 mm, E - 0.25 mm. (from Tkach and Snyder, 2007)

Choanocotyle platti. SEM micrographs were taken from the same specimen that was used to obtain DNA sequence (GenBank #EU196355). A. Anterior part of the body. B. Tegumental spines on the ventral side of the body posterior to the oral sucker. C. Oral sucker region. Scale-bars: A - 250 µm, B - 25 µm, C - 50 µm.

Authors: Vasyl V. Tkach, Scott D. Snyder, Yuriy Kuzmin