Masenia Chatterji, 1933

Curran, Stephen S., Dutton, Haley R., Warren, Micah B., Preez, Louis du & Bullard, Stephen A., 2021, Two new species of Cephalogonimidae Looss, 1899 (Digenea: Plagiorchioidea) from Africa (Mozambique and Guinea), including a new phylogenetic hypothesis for related plagiorchioids, International Journal for Parasitology: Parasites and Wildlife 14, pp. 228-240 : 232-234

3.2. Genus Masenia Chatterji, 1933

Masenia baroensis n. sp.

3.2.1. Description ( Figs. 4 and 5 )

[Based on 10 mature specimens] Body, oval, small, 660–854 long, 335–450 wide near midbody. Tegument covered by robust slightly recurved spines except near posterior end; body spines 8–11.5 long. Oral sucker funnel-shaped, terminal with subterminal mouth opening, 108–140 long, 105–153 wide, with opening surrounded by two rows of alternating elongated conical spines; rows containing 35–36 spines each (usually a total of 72 but spines may have dislodged in some specimens), interrupted dorso-terminally. Circumoral spines generally slightly larger than body spines; oral row 8–14 long; aboral row 8–11.5 long. Prepharynx directing dorsally and diagonally from base of oral sucker, very short, 5–20 long in two measurable specimens. Pharynx nearly spherical, 40–53 long, 40–55 wide. Oesophagus directing dorsally, very short, 10 long in a single measurable specimen. Ventral sucker nearly circular, 108–208 long, 128–208 wide. Oral to ventral sucker width ratio 1: 1.1–1.3 in 9 specimens without pressure (1: 1.6 in single compressed specimen). Forebody 150–250 long or 22–30% of body length (nine unflattened specimens). Intestine bifurcating in forebody immediately anterior to ventral sucker, caeca blind, extending to vicinity of posterior margin of posterior testis.

Testes subglobular, oblique, contiguous or overlapping, intercaecal; anterior testis submedian either on left or right side of body 88–165 long, 93–180 wide, posterior testis 98–160 long, 113–160 wide. Post-testicular space 170–220 long (nine measured) or 23–29% of body length. Cirrus sac club-shaped, sigmoidal, extending to posterior margin of ventral sucker, 300–430 long (eight measured), 75–165 wide (eight measured at widest portion across proximal seminal vesicle). Cirrus sac containing bipartite seminal vesicle, pars prostatica, and unarmed cirrus. Proximal portion of seminal vesicle 13–75 long, 25–55 wide (five measured), distal portion always larger, 75–135 long, 56–70 wide (six measured). Pars prostatica lacking diverticulum or well-defined prostatic bulb, 50–100 long, 33–70 wide (six measured). Cirrus elongate, 100–188 long (six measured). Cirrus sac communicating with small, elongated genital atrium; genital atrium dorsal to oral sucker, median, 20–30 long, 10–13 wide (six measured). Genital pore opening dorso-median, immediately posterior to terminal interruption of oral spines.

Ovary distinctly 2–4 lobed, submedian, amphitypic on the same side as posterior testis, at level of anterior testis but extending slightly anterior relative to it, sometimes overlapping anterior testis ventrally, 93–150 long, 63–120 wide. Ootype surrounded by Mehlis’ gland immediately adjacent and median relative to ovary (exact configuration obscured by eggs in uterus in all specimens). Seminal receptacle dorso-median to and immediately adjacent to ovary, ventral relative to and overlapping Mehlis’ gland, 50–128 long, 38–68 wide (three measured). Laurer’ s canal not observed. Vitellarium comprised of two lateral groups of 7–12 large subglobular to irregular-shaped follicles; follicles surrounding caeca, groups confined to region of ventral sucker. Vitelline reservoir transversely oval shaped, 38–50 long, 28–38 wide (two

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measured), immediately antero-ventral to seminal receptacle, submedian on same side as ovary. Proximal uterus dorso-median, descending from ovarian complex, coiling, and occupying most of hindbody. Distal uterus ascending ventrally on abovarian side, following curvature of cirrus sac, and communicating with indistinct metraterm; metraterm dorsal and parallel with cirrus sac, thin-walled, connecting with posterior end of genital atrium. Eggs filling uterus, oval, operculated, 23–28 long, 15–19 wide (20 measured from distal region of uterus).

Excretory bladder Y-shaped, main stem (visible in one specimen), 205 long or 27% of body length, terminating 18 posteriorly from posterior margin of posterior testis. Excretory system opening through excretory pore at terminal end.

Type host: globe fish, Tetraodon lineatus L., ( Tetraodontiformes : Tetraodontidae ).

Site in host: intestine.

Type locality: Niandan River , Republic of Guinea .

Other locality: Niger River, Republic of Guinea.

Prevalence: Six worms from one of two fish examined from the Niger River; four worms from one of three fish examined from Niandan River.

Specimens deposited: Holotype USNM 1642452 ; 9 paratypes USNM 1642453-1642461 .

Sequence deposited: GenBank No. MW586925.

ZooBank Life Science Identifier: urn:lsid:zoobank.org:pub:9C6- BAB41-1974-41C3-ACCA-554730276E8A.

Etymology: The species is named for the town of Baro, Republic of Guinea, which is surrounded by the drainage from which the specimens were collected.

3.2.2. Remarks

Masenia baroensis n. sp. conforms to the diagnosis for the Cephalogonimidae in having a small, oval body, spinous tegument, genital pore at the anterior extremity, and being parasitic in the digestive tract of a freshwater fish ( Jones and Bray, 2008). We placed the new species in Masenia because it has two circumoral rows of approximately 35–36 spines each (72 total), encircling the oral sucker. Just as in the previously described species, we observed amphitypic orientation of the ovary and gonadal systems in M. baroensis . Specimens having the ovary on the left side have the anterior testis on the right side and the cirrus sac and metraterm approach the genital atrium from the right side of the body ( Fig. 4 ). In contrast, specimens having the ovary on the right side have the anterior testis on the left side and the cirrus sac and metraterm approach the genital atrium from the left side of the body ( Fig. 5 ).

Prior to this study, Masenia contained 24 accepted species, with five confined to infecting freshwater catfishes in Africa, and approximately 19 species confined to infecting Asian fishes (12 limited to freshwater catfishes, two infecting a snakehead species [ Channidae ] in India, and four infecting marine fishes in Indian coastal waters) ( Chandra and Saxena, 2016; Madhavi and Bray, 2018; Scholz et al., 2018; Dumbo et al., 2019a). The accepted African species are: Masenia proteropora (Thomas, 1958) Kudlai, Scholz & Smit, 2018 , which infects a clariid catfish, Clarias anguillaris (L.), in Ghana; Masenia bangweulensis (Beverly-Burton, 1962) Kudlai, Scholz & Smit, 2018 , which infects the clariid Clarias ngamenis Castelnau , in Zambia; Masenia ghanensis ( Fischthal & Thomas, 1968) Kudlai, Scholz & Smit, 2018 , which infects a clariid, Heterobranchus longifilis Valenciennes , in Ghana; Masenia synodontis ( Khalil & Thurston, 1973) Kudlai, Scholz & Smit, 2018 , which infects a mochokid, Synodontis victoriae Boulenger, in Lake Victoria; and Masenia nkomatiensis Dumbo, Dos Santos & Avenant-Oldewage, 2019 , which infects a clariid, Clarias gariepinus (Burchell) , in Mozambique.

Masenia baroensis is unique among its African congeners in having a non-catfish host, a distinctly 3–4 lobed ovary, and has an exceptionally high number of circumoral spines (72). The ovary is entire in M. bangweulensis , M. ghanensis , M. proteropora , and M. nkomatiensis but may be slightly lobed in M. synodontis (see Khalil and Thurston, 1973). Masenia proteropora has 50–58 circumoral spines ( Dumbo et al., 2019a). Masenia bangweulensis has 48 circumoral spines ( Beverley-Burton, 1962). Masenia ghanensis has 56 circumoral spines ( Fischthal and Thomas, 1968). Masenia synodontis has 36–40 circumoral spines ( Khalil and Thurston, 1973). Masenia nkomatiensis has 50 circumoral spines ( Dumbo et al., 2019a). Masenia baroensis differs further from M. proteropora and M. synodontis in having a funnel-shaped rather than subspherical oral sucker (see Thomas, 1958a; Khalil and Thurston, 1973), and uniquely among the African congeners, M. synodontis has a ventral sucker smaller than the oral sucker ( Khalil and Thurston, 1973).

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M. gomtia and M. ritai (see Agrawal, 1963; 1964; Sircar and Sinha, 1970). Masenia baroensis superficially resembles the fifteenth and final Asian congener compared, the marine species Masenia carangai Gupta & Tandon, 1985 , which was described and remains known based on a single specimen that infected jack ( Carangoides armatus [Ruppell]) in the Bay of Bengal on the northeastern coast of India. Both species have approximately 72 circumoral spines, similar oral to ventral sucker width ratios, similar anatomy of the male terminal genitalia (proximal portion of bipartite seminal vesicle is smaller than distal), and similar configurations of the vitellarium. Never-the-less, M. baroensis differs from M. carangai by having a relatively wider, less elongated body (ratio of body length to width ~1: 0.5 compared with ~1: 0.26 in M. carangai ), and the caeca terminate further in the hindbody in M. baroensis (to the post-testicular zone rather than middle of the testicular zone in M. carangai ) (see Gupta and Tandon, 1985).

There is considerable confusion related to the taxonomy of Asian species in Masenia . Jones and Bray (2008) and Dumbo et al. (2019a) accepted 18 Asian species of Masenia and the latter study listed the hosts and countries from which they were described. Chandra and Saxena (2016) accepted the additional species Masenia dayali ( Gupta & Puri, 1984) Chandra & Saxena, 2016 , and we address that species in the discussion. Herein we accept 17 Asian species belonging in Masenia and compare M. baroensis with 15 of those. This decision is explained in the discussion. We differentiated M. baroensis from the 15 Asian congeners using circumoral spine count, sucker width ratio, configuration of the vitellarium, body shape, features of the male terminal genitalia, and extent of the caeca in the hindbody.

In having ~72 circumoral spines, M. baroensis is easily differentiated from the following eight Asian congeners: Masenia collata Chatterji, 1933 (~53 circumoral spines), Masenia moradabadensis ( Srivastava, 1951) Dumbo, Dos Santos & Avenant-Oldewage, 2019 (52 circumoral spines), Masenia dayali Gupta, 1955 (~55 circumoral spines), Masenia fossilisi Gupta, 1955 (~52 circumoral spines), Masenia vittatusia Agrawal, 1963 (52 circumoral spines), Masenia fukienensis ( Tang & Lin, 1973) Dumbo, Dos Santos & Avenant-Oldewage, 2019 (50–64 circumoral spines), Masenia quiloni (Gupta & Tandon, 1984) Madhavi, 2011 (58 circumoral spines), Masenia gwaliorensis ( Bhadauria & Dandotia, 1986) Dumbo, Dos Santos & Avenant-Oldewage, 2019 (56 circumoral spines) (see Chatterji, 1933; Srivastava, 1951; Gupta, 1955; Agrawal, 1963; Tang and Lin, 1973; Bhadauria and Dandotia, 1986; Madhavi and Bray, 2018). In having the oral sucker smaller than the ventral sucker, M. baroensis is differentiated from two more Asian species (both marine) that have an oral sucker larger than ventral sucker: Masenia orissai Gupta & Tandon, 1985 , Masenia upeneusi Gupta & Puri, 1984 (see Gupta and Tandon, 1985; Gupta and Puri, 1984). The distribution of the vitelline follicles serves to differentiate M. baroensis from two additional Asian congeners. Masenia chauhani Agarwal & Singh, 1989 , and Masenia jaunpurensis Maurya & Singh, 2004 both have vitelline follicles extending anteriorly to the oesophageal level (see Agrawal, 1963; Dumbo et al., 2019a), whereas the vitelline follicles are confined to clusters on either side of the ventral sucker in M. baroensis . Masenia baroensis differs from both Masenia gomtia Agrawal, 1963 and Masenia ritai Sircar & Sinha, 1970 (name discussed below) by having a broader, less elongated body (ratio of body length to width ~1: 0.5 in M. baroensis compared with ~1: 0.25 in M. gomtia and ~1: 0.038–0.39 in M. ritai ). Additionally, the proximal part of the bipartite seminal vesicle is smaller than the distal part in M. baroensis ; whereas the opposite is true for both

Figures

Fig. 4. Masenia baroensis n. sp. from the intestine of the globe fish, Tetraodon lineatus L. Ventral view of holotype. Abbreviations: anterior testis, at; caeca, c; cirrus, ci; cirrus sac, cs; excretory bladder, eb; distal portion of seminal vesicle, ds; excretory pore, ep; genital atrium, ga; genital pore, gp; metraterm, m; ovary, ov; pars prostatica, pp; proximal portion of seminal vesicle, ps; posterior testis, pt; uterus (drawn with eggs omitted), u; vitelline follicle, vf.

Fig. 5. Masenia baroensis n. sp. from the intestine of the globe fish, Tetraodon lineatus L. Anterior portion from a specimen having the ovary on the right side of the body. Abbreviations: aboral row of circumoral spines, ar; cirrus, ci; cirrus sac, cs; genital atrium, ga; genital pore, gp; metraterm, m; oral row of circumoral spines, or; oral sucker, os.