Pseudorhabdosynochus samaesarnensis, 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 : 8-11

Pseudorhabdosynochus samaesarnensis n. sp.

urn:lsid:zoobank.org:act:FDF79967-ED74-4848-BBA7-DCBC12E813A8

Type host: Epinephelus lanceolatus (Bloch) ( Perciformes , Serranidae ).

Other hosts: E. coioides (Hamilton) , E. erythrurus (Valenciennes) , E. coeruleopunctatus (Bloch) , E. malabaricus (Bloch & Schneider) , sea cage-cultured hybrid grouper ( TGGG) ( E. fuscoguttatus ♀ × E. lanceolatus ³) and E. fuscoguttatus (Forsskål) ( Perciformes , Serranidae ).

Type-locality: Samaesarn Island in the Gulf of Thailand, Chonburi Province, Eastern Thailand (12°34 0 30.9 00 N 100°

0 00

57 33.7 E), September 2020.

Other locality: Libong Island in the Andaman Sea, Trang Province, Southern Thailand (7°13 0 00.3 00 N 99°21 0 36.0 00 E), April 2020 ; Ban Laem Hin , Phang-Nga Province in the Andaman Sea, Southern Thailand (8°10 0 55.5 00 N 98°20 0 35.3 00 E), May 2020 .

Type-material: Holotype, ZRC.PLA.2041; 2 paratypes, ZRC.PLA.2042-43; 2 paratypes, THNHM-Iv-19367-68; 1 paratype, ZMKU-PM-002076; 2 paratypes from other host, E. coioides , ZMKU-PM-002077-78; 2 paratypes from other host, E. erythrurus , ZMKU-PM-002079-80; 2 paratypes from other host, E. coeruleopunctatus , ZMKU-PM-002081-82; 2 paratypes from other host, E. malabaricus , ZMKU-PM-002083-84; 1 paratype from other host, sea cage-cultured hybrid grouper ( TGGG) ( E. fuscoguttatus ♀ × E. lanceolatus ³), ZMKU-PM-002085.

Site in host: Gills.

Infection indices: Prevalence 100% (one specimen examined and infected); 12 helminth specimens on the single grouper examined.

Etymology: The species name “ samaesarnensis ” was derived from “Samaesarn Island”, where the host fish Epinephelus lanceolatus was collected.

Description ( Figs. 5 and 6 )

[Based on 6 specimens]. Body (including haptor) 745 long (679–821, n = 6); maximum width 198 (160–234, n = 6). Tegument scaly (observed in some specimens). Anterior region with 3 pairs of lateral head organs and 2 pairs of eye-spots; anterior pair smaller than posterior pair. Pharynx median, spherical, 45 (39–47, n = 6) × 45 (39–47, n = 6). Esophagus absent. Intestinal bifurcation immediately follows pharynx. Haptor differentiated from rest of body, 220 wide (178–243, n = 6), with 2 similar squamodiscs, 2 pairs of lateral hamuli, 3 bars, and 14 marginal hooklets. Squamodiscs round-shaped, made up of rows of rodlets, the innermost 1–2 rows of which form closed ovals and last row of which are thinner and separated. Dorsal squamodisc 53 long (51–54, n = 4), 47 wide (44–50, n = 4), with 9–12 rows of rodlets, the innermost 1–2 rows of which form closed ovals. Ventral squamodisc 52 long (49–56, n = 4), 45 wide (41–52, n = 4), with 9–10 rows of rodlets, the innermost 1–2 rows of which form closed ovals. Ventral hamulus with distinct guard and expanded deep root, elongated shaft slightly arched and recurved toward the tip, outer length 48 (45–51, n = 6), inner length 37 (35–39, n = 6). Dorsal hamulus with indistinct guard and expanded deep root, elongated shaft slightly arched and recurved toward the tip, outer length 41 (40–41, n = 6), inner length 25 (24–27, n = 6). Dorsal (lateral) bar straight, with flattened medial extremity, 61 long (57–67, n = 6), 17 wide (16–19, n = 6). Ventral bar elongated, with constricted median portion and tapered ends, 94 long (92– 96, n = 6), 15 wide (14–16, n = 6); visible groove that extends to both thin extremities. Male quadriloculate organ with fourth (posterior) chamber slightly more sclerotized than 3 anterior chambers, inner length 56 (51–60, n = 6), fourth chamber ends in sclerotized cone, 12 long (10–13, n = 6), prolonged by sclerotized tube, 15 long (13–17, n = 6), end of tube prolonged by filament of variable length. Test is subspherical, intercecal. Ovary pretesticular, encircles right intestinal cecum. Vitelline follicles lateral, coextensive with intestinal ceca and terminate anterior to the peduncle. Egg not seen.

Sclerotized vagina with a complex sclerotized structure, aspect changes according to specimen and orientation ( Figs. 6A–6F ). Sclerotized vagina comprises anterior cup-shaped trumpet, followed by primary canal, primary chamber and accessory structure; thick-walled anterior cup-shaped trumpet in continuity with short straight or curved primary canal ( Fig. 6A ), thick-walled sclerotization and widens into a thick-walled primary chamber; accessory structure connects to the primary chamber. Total length of sclerotized vagina (measured from distal extremity of trumpet to base of vagina, not considering curve along primary canal) 27 (25–29, n = 6), length variable because of variation in curvature of primary canal.

Differential diagnosis

Pseudorhabdosynochus samaesarnensis n. sp. is distinguished from other Pseudorhabdosynochus species by the structure of its sclerotized vagina. Pseudorhabdosynochus samaesarnensis n. sp. has a vaginal structure similar to that of P. nhatrangensis from E. coioides (Hamilton) and E. bleekeri (Vaillant) off Vietnam. The structure of their sclerotized vagina was found to be very similar, but the number of rows of rodlets found in P. nhatrangensis was always 10 [ 7], while Note that P. nhatrangensis is not a valid species.

in P. samaesarnensis n. sp., the rows were found to vary in number from 9 to 13. In addition, the specimens of P. samaesarnensis n. sp. from E. lanceolatus were larger than those of P. nhatrangensis from E. coioides and E. bleekeri ( Table 2 ). However, P. nhatrangensis Dang, Bristow, Schander & Berland, 2013 is not a valid species because the article was not compliant with the new Article 8.5.3 of the International Code of Zoological Nomenclature ( ICZN) [ 3].

Figures

Figure 5. Pseudorhabdosynochus samaesarnensis n. sp. from Epinephelus lanceolatus from Samaesarn Island in the Gulf of Thailand. (A) Composite drawing (mainly from holotype), dorsal view. (B) Male quadriloculate organ, dorsal view. (C) Sclerotized vagina, dorsal view. (D) Ventral hamulus. (E) Dorsal hamulus. (F) Dorsal (lateral) bar. (G) Ventral bar. (H) Dorsal squamodisc. (I) Ventral squamodisc. (J) Hooklet. Scale-bars: (A) 200 µm. (B)–(J): 50 µm.

Figure 6. Variations (A)–(F) of the sclerotized vagina of Pseudorhabdosynochus samaesarnensis n. sp. from Epinephelus lanceolatus and E. coioides in the Gulf of Thailand. Abbreviations: Tr – trumpet, Ca1 – primary canal, Ch1 – primary chamber. As, accessory structure. Scalebar: 50 µm.