Prosorhynchus maternus Bray & Justine, 2006

Truong, Thuong Van, Palm, Harry W., Bui, Te Quang, Ngo, Huong Thi Thuy & Bray, Rodney A., 2016, Prosorhynchus Odhner, 1905 (Digenea: Bucephalidae) from the orange-spotted grouper Epinephelus coioides (Hamilton, 1822) (Epinephelidae), including Prosorhynchus tonkinensis n. sp., from the Gulf of Tonkin, Vietnam, Zootaxa 4170 (1), pp. 71-92 : 88-89

Prosorhynchus maternus Bray & Justine, 2006

( Fig. 1 . f)

Site. Intestine.

Locality. Cat Ba, Hai Phong (20°46'30"N, 107°04'38"E, July 2014).

Description. Measurement data based on one mature specimen ( Table 5), body elongate, widest at vitellarium level, posterior part narrowing. Tegument spinous; spines squamous, tiny reach to posterior extremity. Rhynchus elongate, with 5–6 muscular lobes around anterior rim. Mouth at the level of ovary and anterior testis level, inside anterior half of body. Pharynx spherical, muscular, in anterior half of body. Cecum oval, sac-like, extends anteriorly from pharynx, median to vitelline fields.

Testes 2, spherical, sub-oblique, slightly separated, anterior testis sinistral, posterior testis dextral, inside anterior half of body. Cirrus–sac elongate, muscular, not thick-walled, inside posterior one-third of body, does not reach to posterior testis. Seminal vesicle large, elongate-oval, sinistral in proximal portion of cirrus-sac. Parsprostatica long, in two distinct parts; proximal part narrow, curved proximally to form convoluted seminal duct, joins at dorsal posterior to seminal vesicle; distal part wider, straighter, surrounded by dense layer of gland-cells, lining of filaments in chevron arrangement. Ejaculatory is duct narrow, complex genital lobe inside genital atrium. Genital atrium large. Genital pore distinctly separated from posterior end.

Ovary oval, slightly pretesticular, dextral. Mehlis’ gland posterior to ovary. Uterus reaches anteriorly to anterior testis, posteriorly to cirrus-sac. Eggs tanned, numerous. Vitellarium consists of two lateral fields of 15 follicles, symmetrical, long vitelline field is sinistral, inside anterior half of body, not reaching the rhynchus. Excretory pore terminal; excretory vesicle extending is not seen.

Remarks. Prosorhynchus maternus was first reported from Epinephelus malabaricus off New Caledonia in 2006 by Bray & Justine (2006). Its descriptions and illustrations are very similar to our specimens ( Table 5). P. maternus differs from P. luzonicus , P. pacificus and P. atlanticus in a slender elongated rhynchus, the mouth is further anterior inside the anterior half of body, and the vitellarium does not reach close to the rhynchus. The cirrussac never reaches close to the posterior testis, whereas in P. luzonicus , P. pacificus and P. atlanticus the rhynchus is broad, the mouth is located in the middle of the body, the vitellarium reaches close to rhynchus, and the cirrus-sac often reaches to or close to the posterior testis (In P. luzonicus of this study, the vitellarium almost reaches to the rhynchus, the cirrus-sac usually reaches to the posterior testis, and may reach to the ovary). Prosorhynchus maternus differs from P. gonoderus ( Manter 1940a) in its slender elongated rhynchus with 5–6 lobes around the anterior margin and the relatively small cirrus-sac, whereas in P. gonoderus the rhynchus is broad, muscular and without lobes around the anterior rim; the mouth is often located further anteriorly and the cirrus-sac is relatively much larger.

Although only one specimen is in good condition, its clear features are very similar to P. maternus . Therefore, this worm is determined as P. maternus in the present study. This is the first report P. maternus from E. coioides and from Vietnamese waters.

Figures

FIGURE 1. Prosorhynchus spp. from groupers. a, b Prosorhynchus tonkinensis n. sp., note the spermatophore (a) and intended posterior extremity (b); c Prosorhynchus sp. A (VN); d Prosorhynchus sp. B (VN); e P. luzonicus; f Prosorhynchus maternus. Uterus in bold outline and treated as transparent. Scale bars: a, b, c, d = 100 µm; e, f = 200 µm.