Pseudorhabdosynochus cephalopholi, Saengpheng & Purivirojkul, 2022

Saengpheng, Chompunooch & Purivirojkul, Watchariya, 2022, Three new species of Pseudorhabdosynochus (Monogenea, Diplectanidae) from several species of Cephalopholis and Epinephelus (Perciformes, Serranidae) from Thailand, Parasite (Paris, France) 29 (48), pp. 1-14 : 5

Pseudorhabdosynochus cephalopholi n. sp.

urn:lsid:zoobank.org:act:69811A09-7C5C-4D38-B2CA-72D77973425C

Type host: Cephalopholis sonnerati (Valenciennes) ( Perciformes , Serranidae ).

Other host: C. miniata (Forsskål) ( Perciformes , Serranidae )

Type locality: Surat Thani Province, the lower Gulf of Thailand, Southern Thailand (9°48 0 10.1 00 N 99°55 0 31.1 00 E), May 2019 .

Type-material: Holotype, ZRC.PLA.1118; 2 paratypes, ZRC.PLA.1119-20; 2 paratypes, THNHM-Iv-19365-66; 20 paratypes, ZMKU-PM-002054-73; 2 paratypes from other host, C. miniata , ZMKU-PM-002074-75.

Site in host: Gills.

Infection indices: Prevalence 100% (4/4); mean intensity 62.5 individuals/fish (250/4).

Etymology: Species name derived from Cephalopholis , which is the name of the host genus (both type-host and other host). This monogenean species seems to be specific to this host genus.

Description ( Figs. 3 and 4 )

[Based on 25 specimens]. Body (including haptor) 393 long (260–645, n = 25), maximum width 106 (83–126, n = 25). Tegument smooth. Anterior region with 3 pairs of lateral head organs and 2 pairs of eye-spots; anterior pair smaller than posterior pair. Pharynx median, spherical, 24 (18–31, n = 25) × 24 (19–31, n = 25). Esophagus absent. Intestinal bifurcation immediately follows pharynx. Haptor differentiated from rest of body, 216 wide (167–261, n = 25), with 2 similar squamodiscs, 2 pairs of lateral hamuli, 3 bars, and 14 marginal hooklets. Dorsal and ventral squamodiscs round-shaped, made up of rows of rodlets; rodlets similar in width in all rows except last row with thin and separate rodlets; central rows form closed ovals. Dorsal squamodisc 39 long (30–56, n = 11), 41 wide (32–57, n = 11), with 8–10 rows of rodlets, the innermost of which form closed oval. Ventral squamodisc 39 long (34–43, n = 11), 43 wide (37–49, n = 11), with 8–10 rows of rodlets, the innermost of which form closed oval. Ventral hamulus with distinct guard and expanded deep root, elongated shaft and recurved toward the tip, outer length 41 (37–46, n = 25), inner length 31 (29–36, n = 25). Dorsal hamulus with indistinct guard and expanded deep root, elongated shaft and recurved toward the tip, outer length 35 (32–38, n = 25), inner length 22 (19–25, n = 25). Dorsal (lateral) bar straight, elongated, with flattened medial extremity and cylindrical lateral extremity, 72 long (64–79, n = 25), 10 wide (7–14, n = 25). Ventral bar flat, thin, elongated, with constricted median portion and pointed ends, 104 long (90–114, n = 25), 10 wide (8–14, n = 25); visible groove that extends to both thin extremities. Male quadriloculate organ divided into 4 chambers, inner length 40 (33–46, n = 25), fourth chamber ends in sclerotized cone, 10 long (7–12, n = 25), lengthened by sclerotized tube, 11 long (6–14, n = 25). Testis subspherical, intercecal. Ovary pretesticular, encircles right intestinal cecum. Vitelline follicles lateral, coextensive with intestinal ceca, confluent posterior to testis region and terminate anterior to peduncle. Egg ( Fig. 3D ) 86 long (74–91, n = 4), 51 wide (38–64, n = 4).

Sclerotized vagina with a complex sclerotized structure, aspect changes according to specimen and orientation ( Figs. 4A–4I ). Sclerotized vagina comprises anterior trumpet, followed by primary canal, primary chamber, secondary canal, secondary chamber, and accessory structure; trumpet in continuity with primary canal tube, long, coiled ( Fig. 4F ), or curved ( Figs. 4A–E and 4G–4I ) at around midlength, heavily sclerotized, progressively into primary chamber or form a bend in posterior region and progressively into primary chamber ( Fig. 4H ); secondary chamber communicates with primary chamber through a short secondary canal, and accessory structure connected to secondary chamber. Total length of sclerotized vagina (measured from distal extremity of trumpet to base of vagina, not considering curved length along coil or curve of primary canal) 25 (19–30, n = 25), length variable because of variation in coil or curvature of primary canal.

Differential diagnosis

Pseudorhabdosynochus cephalopholi n. sp. is distinguished from other Pseudorhabdosynochus species by the structure of its sclerotized vagina, in addition to the differing lengths of some sclerotized organs and the number of rows of rodlets in each squamodisc. Pseudorhabdosynochus minutus from C. sonnerati out of the Barrier reef off Nouméa, New Caledonia has the following characteristics. The general morphology of its sclerotized vagina and its size (25 µm), body size (270– 550 µm versus 260–645 µm in P. cephalopholi n. sp.), number of rows of rodlets in each squamodisc (10–11 rows of rodlets and a 0–1 closed oval), and host species ( C. sonnerati ) are similar to those of P. cephalopholi n. sp. Pseudorhabdosynochus minutus can be distinguished, however, by the chamber structure of its sclerotized vagina ( P. minutus has spherical chambers, unlike the chambers in P. cephalopholi n. sp.). Pseudorhabdosynochus argus from C. argus out of the Barrier reef off Nouméa, New Caledonia has a sclerotized vagina similar to that of P. cephalopholi n. sp., characterized by an anterior trumpet followed by a long primary canal. Pseudorhabdosynochus argus can be distinguished, however, by the size of its sclerotized vagina (38 µm vs. 25 µm in P. cephalopholi n. sp.); the morphology of its sclerotized vagina, with the primary canal coiled in its anterior part, just after the trumpet (see [ 15]), unlike in P. cephalopholi n. sp.; its body size (888 µm versus 393 µm); and the different lengths of its sclerotized organs: of its ventral hamulus, outer length of 53 µm versus 41 µm and inner length of 44 µm versus 31 µm; of its dorsal hamulus, outer length of 44 µm versus 35 µm and inner length of 27 µm versus 22 µm; of its ventral bar, 79 µm long versus 104 µm long; of its quadriloculate organ, inner length of 58 µm versus 40 µm; and of the cone of its quadriloculate organ, 22 µm long versus 10 µm long ( Table 1 ). Pseudorhabdosynochus sp. Justine, 2007 from C. boenak (Bloch) out of Heron Island, Queensland, Australia has a sclerotized vagina similar to that of P. cephalopholi n. sp., characterized by an anterior trumpet followed by a long primary canal. Pseudorhabdosynochus sp. can be distinguished by the following: the morphology of its primary canal, the shapes of its chambers, and the number of rows of rodlets in each of its squamodiscs (7 rows of rodlets, including 0–2 closed rows versus 8–10 rows of rodlets and an innermost row closed oval in P. cephalopholi n. sp.). Pseudorhabdosynochus sp. generally resembles a dwarf P. argus [ 15]. Pseudorhabdosynochus euitoe Justine, 2007 from E. maculatus (Bloch) out of the Barrier reef off Nouméa, New Caledonia has a sclerotized vagina similar to that of P. cephalopholi n. sp., characterized by an anterior trumpet followed by a long, coiled primary canal. However, the trumpet is characterized by a heavily sclerotized ring at the trumpetcanal limit in the P. euitoe (which is absent in P. cephalopholi n. sp.). Pseudorhabdosynochus fuitoe Justine, 2007 from E. maculatus out of the Barrier reef off Nouméa, New Caledonia has a sclerotized vagina similar to that of P. cephalopholi n. sp., characterized by an anterior trumpet followed by a heavy, long, coiled or curved primary canal, but the shapes of their chambers differ [ 14]. Pseudorhabdosynochus manifestus Justine & Sigura, 2007 from E. malabaricus (Bloch & Schneider) out of the Lagoon off Nouméa, New Caledonia is differentiated by its sclerotized vagina and its cone-shaped primary canal that is coiled in its anterior part and straight in its posterior part (which is absent in P. cephalopholi n. sp.) [ 20].

Figures

Figure 3. Pseudorhabdosynochus cephalopholi n. sp. from Cephalopholis sonnerati in the lower Gulf of Thailand. (A) Composite drawing (mainly from holotype), dorsal view. (B) Male quadriloculate organ, dorsal view. (C) Sclerotized vagina, dorsal view. (D) Egg. (E) Ventral hamulus. (F) Dorsal hamulus. (G) Dorsal (lateral) bar. (H) Ventral bar. (I) Dorsal squamodisc. (J) Ventral squamodisc. (K) Hooklet. Scale-bars: (A) 100 µm; (B)–(K) 50 µm.

Figure 4. Variations (A)–(I) of the sclerotized vagina of Pseudorhabdosynochus cephalopholi n. sp. from Cephalopholis sonnerati in the lower Gulf of Thailand. Abbreviations: Tr – trumpet, Ca1 – primary canal, Ch1 – primary chamber, Ca2 – secondary canal, Ch2 – secondary chamber, As – accessory structure. Scale-bar: 50 µm.