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: 82-84

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Prosorhynchus   sp. B (VN)

( Fig. 1 View FIGURE 1 .d)

Site. Intestine.

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

Description. Based on one specimen ( Table 1). Body elongate, widest at vitelline region. Tegument spinous; spines squamous, tiny, reach to posterior extremity. Rhynchus conical, muscular, longer than wide, blunt at posterior end. Mouth near mid body, just anterior to posterior testis, inside anterior half of body. Pharynx globular, anterior-dextral to posterior testis. Cecum oval, sac-like, extends anteriorly from pharynx.

Testes 2, sub-spherical, oblique, anterior testis sinistral to ovary. Cirrus–sac elongate, not thick walled, not reaching to posterior testis, located in posterior half of body. Seminal vesicle tubular, extending about half-length of cirrus-sac. Pars-prostatica relatively narrow, with dorsal-ventral loop near middle of cirrus-sac. Ejaculatory duct narrow, complex genital lobe inside genital atrium. Genital atrium large. Genital pore distinctly separated from posterior end.

Ovary oval, dextral to anterior testis. Uterus reaches anteriorly as far as anterior testis, extending posteriorly to posterior margin of cirrus-sac. Eggs tanned, numerous. Vitellarium forming an arch of 24 follicles, beginning at posterior testis level and covering cecum and gonads. Excretory pore terminal. Excretory vesicle not seen.

Remarks. As only a single specimen with clear features could be observed, which differs from all other known species, we herewith record it as Prosorhynchus   sp. B ( VN) due to the lack of further material.

The comparison diagram visual key of Prosorhynchus   sp. B ( VN) ( Fig. 4) demonstrates that Prosorhynchus   sp. B ( VN) does not differ from P. lafii   , P. maternus   and P. pacificus   in the visual key. However, it still can be distinguished by its arched vitellarium. In P. lafii   from the Brown-marbled Grouper Epinephelus fuscoguttatus (Forsskål)   off Queensland, Australia ( Bott & Cribb 2009), P. maternus   from E. malabaricus   off New Caledonia ( Bray & Justine 2006) and P. pacificus   from M. olfax   off Galapagos Islands waters ( Ecuador)( Manter 1940a), the vitelline follicles are in two lateral fields.

Figure 4 illustrates that two species have one black square against their name, namely P. caudovatus   and P. luzonicus   . However, P. caudovatus   from Epinephelus   sp. from off Suez (Red Sea, Egypt) ( Eckmann 1932) differs from Prosorhynchus   sp. B ( VN) in its filamented eggs. Further, it also differs in one major (Rhynchus %) and three minor distinguishing features in the visual keys ( Table 4 View TABLE 4 ). Prosorhynchus   sp. B ( VN) is clearly distinguished from P. luzonicus   from L. calcarifer in Philippine   waters ( Velasquez 1959) by its arched vitellarium. In the visual keys, Prosorhynchus   sp. B ( VN) also is distinguished from P. luzonicus   in PTR % ( Table 4 View TABLE 4 ) but it does not differ in this feature considering the new data on P. luzonicus   from Bray & Justine (2013) and the present study (see Table 4 View TABLE 4 ).

The visual key demonstrates that P. atlanticus   , P. jexi   , P. jupe   , P. promicropsi   and P. serrani   have two black squares against their name. Prosorhynchus atlanticus   from the Gag Mycteroperca microlepis (Goode & Bean)   and M. bonaci   off Florida ( Manter 1940b) is distinguished from Prosorhynchus   sp. B ( VN) in its vitellarium in two follicles fields, whereas in Prosorhynchus   sp. B ( VN), the vitellarium is an arched form. Prosorhynchus jexi   from the Longfin Grouper Epinephelus quoyanus (Valenciennes)   off Australia ( Bott & Cribb 2009) differs from Prosorhynchus   sp. B ( VN) in two clustered lateral vitelline fields. Prosorhynchus jupe   from ‘ Promicrops   guttatus   (presumably the Red Hind Epinephelus guttatus   [Linnaeus]) in Brazilian waters ( Kohn 1967) is distinguished from Prosorhynchus   sp. B ( VN) in its tandem vitelline fields, and P. promicropsi   from Promicrops itaiara   off Florida ( Manter 1940b) is distinguished from Prosorhynchus   sp. B ( VN) in its vitellarium in two fields and the cecum extended anteriorly beyond the vitellarium. Prosorhynchus serrani   from Variola louti   off New Caledonia ( Durio & Manter 1968) is distinguished from Prosorhynchus   sp. B ( VN) in its thick walled cirrus-sac. Furthermore, Prosorhynchus   sp. B ( VN) differs from all of the above species in some major and minor distinguishing features as seen in table 3.

TABLE 4. Ratio comparison of Prosorhynchus sp. B (VN), yellow shading shows major distinctions.

Length Width % Rhynchus % PreVRt % PreUR %
Prosorhynchus   sp. B (VN) 1597 20 18 20 37
P. luzonicus   824–1860 20–34 18–25 15–28 29–44
P. lafii   1040–1184 15–22 18 26 34
P. maternus   2052–2227 19–21 13–17 19–23 34–41
P. pacificus   1206–1444 25–27 18–19 26–31 41–46
P. luzonicus   1060–2020 22–25 10–19 20 42
P. caudovatus   2000–4000 18–20 10–12 18–31 25–46
P. atlanticus   705–1677 27–33 24–26 23–25 36–49
P. jexi   1104–1424 19–25 15 20 32
P. jupe   1520–2530 13–21 6–11 15–24 29–42
P. promicropsi   1498–1957 18–20 13–15 35 44
P. serrani   1027–2245 22 12–18 20 17