Heteropriapulus simplexioides, Mendoza-Franco & Hern & andez-Gomez & Caspeta-Mandujano, 2023

Mendoza-Franco, Edgar F., Hern, Raúl E., andez-Gomez & Caspeta-Mandujano, Juan M., 2023, New and previously known ectoparasitic monogenoids (Platyhelminthes) on native and non-native fishes from tributaries of the Usumacinta River basin (southern Mexico), a Neotropical transition zone, International Journal for Parasitology: Parasites and Wildlife 22, pp. 92-100 : 94-96

Heteropriapulus simplexioides n. sp. ( Fig. 2A–I )

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Type host: Pterygoplichthys pardalis (Castelnau, 1855) ( Loricariidae : Siluriformes ).

Type locality: Palizada river (18 ◦ 5′12.95″N, 92 ◦ 5′27.25″W) (tributary of the Usumacinta River basin) in the state of Campeche (southern Mexico) .

Site of infection: Gill lamellae.

Another host: Pterygoplichthys disyunctivus (Weber, 1991) from the Recreo river (17 ◦ 28′40.05″N; 91 ◦ 25′47.8″W) located in the municipality of Tenosique , in the state of Tabasco (southern Mexico). Prevalence and intensity of infection: 19 fish infected of 19 examined (100%); mean intensity of infection 11 parasites per infected fish from Palizada river; 11 of 11 fish examined from Recreo river (100%; 9) .

Specimens deposited: Holotype, CNHE (12045); 33 paratypes, CNHE (12046); 10 voucher specimens on P. disyunctivus from the Recreo river in CNHE (12047).

Etymology: The specific name indicates the similarity of the copulatory complex of this species to that of Heteropriapulus simplex Li and Huang (2012) .

Description (based on 10 specimens mounted unstained in Gray and Wess medium and 24 unstained with LA-GAP mixture; measurements of specimens on P. disyunctivus from the Recreo river are in brackets and those from the type locality are in parentheses): Body 164 (130–200; n = 25) [240 (120–305; n = 9)] long, fusiform; greatest width 60 (52–70; n = 5) [101 (55–120; n = 4)] usually in posterior trunk at level of gonads. Terminal cephalic lobes well developed, containing large head organ; 3 bilateral pairs of head organs lying posterior to cephalic lobes; cephalic glands indistinct. Accessory (melanistic) granules infrequent in cephalic region. Pharynx subspherical, 18–19 [26 (25–28; n = 3)] in diameter. Testis 8–10 x 10–13, ovate to pyriform; seminal vesicle tapered at each end, in left side of body near mid-length; prostatic reservoirs pyriform. Copulatory organ 42 (31–53; n = 26) [35 (28–48; n = 10)] long, with rounded base, elongated and slender sigmoid tube (distal region tapered), intertwined with accessory piece. Accessory piece 37 (31–43; n = 15) [28 (24–30; n = 4)] long, a single straight or arched unit. Germarium subspherical, 29 (24–35; n = 3) long, 24–25 wide. Vaginal pore mid-ventral; vaginal canal short, poorly sclerotized; seminal receptacle inconspicuous, immediately internal to vaginal pore. Vitelline follicles moderately dense. Peduncle broad to non-existent, slightly tapered posteriorly. Haptor 53 (45–60; n = 14) [64 (50–85; n = 5)] wide, heptagonal. Hooks 11 (10–12; n = 6) long, with upright acute thumb and slender shank. Ventral anchor 33 (31–37; n = 43) [35 (32–37; n = 15)] long, with flattened base, elongate shaft and point with recurved tip; base 10 (9–11; n = 13) [9 (8–11; n = 12)] wide; shaft and point of ventral anchors extending posteroventrally from haptor; anchor filament double, well developed (not illustrated). Dorsal anchor 20 (19–23; n = 25) [20 (19–21; n = 10)] long, with short to non-existent deep root, tapered superficial root, evenly curved shaft and elongate point extending past level of superficial root; base 7 (6–8; n = 10) [7 (6–9; n = 7)] wide. Ventral bar 45 (41–51; n = 12) [47 (41–51; n = 7)] long, slightly arched anteriorly, with tapered ends directed posteriorly. Dorsal bar 17 (16–19; n = 5) long, narrow, rod-shaped.

3.2.1.2. Remarks. Heteropriapulus ( Jogunoori et al., 2004; Kritsky, 2007 (as amended by Acosta et al., 2017) accommodates dactylogyrid species having eyespots dissociated, gonads overlapping, unarticulated copulatory organ and accessory piece, MCO tubular (sigmoid or straight), accessory piece composed of a single or variable number of subunits, vaginal pore mid-ventral, and ventral anchors lacking roots with elongate shaft imperceptible joining point. Currently, eight species of Heteropriapulus have been recognized from South American loricariid catfishes of Pterygoplichthys , Hypostomus and Rhinelepis (see Acosta et al., 2017). Some of these species of Heteropriapulus , described and/or reported from India, China, Japan and Mexico are from their introduced or invasive hosts of South America origin ( Jogunoori et al., 2004; Mendoza-Franco et al., 2012; Nitta and Nagasawa, 2013; Rodríguez-Santiago et al., 2016). Based on comparative copulatory complex morphology, H. simplexioides n. sp. on P. pardalis from Palizada River (southern Mexico) most resembles H. simplex which was originally described by Li and Huang (2012) on Hypostomus plecostomus (Linnaeus) introduced to China and later reported by Acosta et al. (2017) on Pterygoplichthys ambrosettii (Holmberg) from Brazil. Both species, H. simplexioides n. sp. and H. simplex possess an accessory piece as a single straight unit. Heteropriapulus simplexioides n. sp. differs from H. simplex by the shape of its MCO, i.e., an elongate, slender sigmoid tube and intertwined with accessory piece (a robust sigmoid tube in H. simplex ). Furthermore, H. simplexioides n. sp. can be distinguished by having a slender dorsal bar (robust in H. simplex ), dorsal anchor with elongate point extending past level of superficial root (moderately short point in H. simplex ), and by the size of its ventral anchor (length 31–37 vs 15–20, 24–31 in H. simplex from Li and Huang [2012)] and Acosta et al., [2017], respectively) and slightly by the size of its ventral bar (41–51 length vs 48–58, 50–74 in H. simplex from Li and Huang, [2012] and Acosta et al., [2017], respectively) (see Fig. 2 in the present study and Fig. 3 in Acosta et al., 2017). The introduced P. pardalis to southeastern Mexico was initially reported to be parasitized with Heteropriapulus sp. from Lacantún river in the state of Chiapas (Mendoza-Franco et al., 2012) and infected with Heteropriapulus heterotylus Jogunoori et al., 2004 (also on P. disyunctivus ) from two localities (Santa Gertrudis and La Rivera) of the Palizada River (Rodríguez-Santiago et al., 2016). However, what is noteworthy is that these latter authors also reported Urocleidoides vaginoclaustrum Jogunoori et al., 2004 ( Dactylogyridae ) on P. pardalis . Urocleidoides vaginoclaustrum was originally described on the green swordtail Xiphophorus helleri Heckel, 1848 ( Poeciliidae ) and its

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occurrence on P. pardalis seems unlikely to happen because species of Urocleidoides sensu stricto (see Kritsky et al., 1986), are only known from hosts of the Characiformes, Cyprinodontiformes and Gymnotiformes (see MendozaFranco and Reina, 2008; Mendoza-Franco et al., 2015; Santos and Domingues, 2023) and the potential transfer of U. vaginoclaustrum from native hosts to siluriforms, i.e., P. pardalis appears low. Furthermore, Rodríguez-Santiago et al. (2016) did not provide any supplemental observation and/or morphometric data for reporting U. vaginoclaustrum (which was misspelled as vaginoclastrum) which is morphologically well differentiated (see Mendoza-Franco et al., 2015) from Heteropriapulus spp. (i.e., the elongate shaft and point with recurved tip is lacking in U. vaginoclaustrum ) to support the occurrence of U. vaginoclaustrum on P. pardalis . Heteropriapulus simplexioides n. sp. represents the first description of a dactylogyrid on a non-native host species of Pterygoplichthys in Mexico.

Figures

Fig. 2. Heteropriapulus simplexioides n. sp. on Pterygoplichthys pardalis (Loricariidae) from the Usumacinta river basin (southern Mexico). A – whole mount (composite, ventral view); B, C, and E – copulatory complexes; D – ventral anchor; F – dorsal anchor; G – hook; H – dorsal bar; I – ventral bar.

Fig. 3. Haptoral and copulatory complex sclerites of Heteropriapulus heterotylioides n. sp. on Pterygoplichthys pardalis (Loricariidae) from the Usumacinta river basin (southern Mexico). A, B, and C – copulatory complexes (A and C in dorsal view; B in ventral view); D – ventral anchor; E – hook; F, G and H – dorsal anchors; I and J – ventral bars; K and L – dorsal bars; M – vaginal tube.