Pseudorhabdosynochus chauveti, Sigura & Justine, 2008

Sigura, Aude & Justine, Jean-Lou, 2008, Monogeneans of the speckled blue grouper, Epinephelus cyanopodus (Perciformes, Serranidae), from off New Caledonia, with a description of four new species of Pseudorhabdosynochus and one new species of Laticola (Monogenea: Diplectanidae), and evidence of monogenean faunal changes according to the size of fish, Zootaxa 1695, pp. 1-44 : 16-21

Pseudorhabdosynochus chauveti n. sp.

( Figs 7–9)

Type host: Epinephelus cyanopodus Richardson (Serranidae) .

Type locality: Lagoon off Nouméa, New Caledonia.

Site: Between secondary gill lamellae.

Type specimens: Holotype, JNC1625 A27, Passe de Dumbéa , off Nouméa, New Caledonia (22°20’S, 166°15’E, 25.x.2005).

Material examined: 57 specimens including 16 ‘carmine’ (c) and 9 ‘picrate’ (p).

Material deposited: Holotype (c) and 28 paratypes (7 c, 12 uc, 9 p), MNHN, JNC1625 , 1626 , 1660 , 1661 ; paratypes, BMNH 2007.11.23.5. (c), 2007.11.23.6–7 (2 uc); USNPC 100402 (1 c, 1 uc), 100403 (1 uc); SAMA AHC 29297 (c), 29298 (uc); HCIP M-459 (1 c, 2 uc); SZU 2007112103-1 (c), 2007112103-2 (uc).

Prevalence: 47 % (8/17) in all fish (Table 2); 67% (8/12) in large fish with ‘specific’ fauna ( Table 10).

Intensity: See Table 2; maximum calculated intensity 48; this rare species represented 3.8% of the total number of monogeneans.

Etymology: Named after Professor Claude Chauvet, a renowned specialist of grouper biology, who kindly provided most of the fish hosts used in this study.

Description: Body wide; length h 590, c 517 (380–641, n = 13), width h 391, c 328 (220–461, n = 13). Tegument scaly; posterior region with scales on ventral and dorsal faces from squamodiscs to below level of ovary and testis. Anterior region with 3 pairs of head organs and 2 pairs of eye-spots; distance between outer margins of anterior eye-spot pair h 30, c 37 (29–50, n = 5), of posterior eye-spot pair h -, c 29 (22–37, n = 11).

Haptor differentiated from rest of body, less wide than body, width h 211, c 197 (170–244, n = 12), provided with 2 dissimilar squamodiscs, 2 pairs of lateral hamuli, 3 bars and 14 marginal hooklets.

Squamodiscs round in shape, made up of rows of rodlets; central rows forming closed ovals in certain cases (6/15); rodlets crenate in central rows; rodlets progressively thinner from centre to periphery; rodlets adjacent in all rows except last row; last row with very thin, separated rodlets; ventral and dorsal squamodiscs dissimilar; ventral squamodisc length h 76, c 71 (61–83, n = 10), width h 68, c 72 (65–80, n = 10), with h 14, generally 14 (13–16, n = 10) rows of rodlets and 0–1 closed oval; total number of rodlets h 178, mean 191 (178–206, n = 8, individual variations in Table 5); dorsal squamodisc, length h 86, c 76 (67–87, n = 7), width h 76, c 73 (66–78, n = 7), with h 15, generally 15 (13–16, n = 8) rows of rodlets and 0–1 closed ovals; total number of rodlets h 201, mean 200 (188-205, n = 6, individual variations in Table 5).

* Holotype, drawn in Figs. 8D,E; v, central row ‘v-shaped’ almost close; i, incomplete row.

Ventral hamulus with thick handle and distinct guard, outer length h 43, c 42 (39–45, n = 21), p 45 (41– 48, n = 16), inner length h 35, c 35 (30–39, n = 22), p 37 (36–39, n = 16). Dorsal hamulus with indistinct guard, outer length h 37, c 37 (32–40, n = 24), p 37 (35–40, n = 14), inner length h 23, c 23 (20–25, n = 16), p 23 (20–26, n = 14). Dorsal (lateral) bars straight, with flattened medial extremity and thick cylindrical lateral extremity, length h 64, c 61 (54–66, n = 24), p 67 (61–77, n = 16), maximum width h 16, c 16 (13–18, n = 22), p 16 (13–20, n = 16). Ventral bar flat, with slightly constricted median portion and pointed extremities, length h 90, c 91 (88–100, n = 12), p 98 (89–104, n = 9), maximum width h 13, c 14 (11–17, n = 12), p 15 (13–18, n = 9); groove visible on its ventral side.

Pharynx subspherical, length h 48, c 43 (28–54, n = 13), width h 46, c 40 (24–55, n = 13). Oesophagus apparently absent, such that intestinal bifurcation immediately follows pharynx. Caeca simple, terminate blindly at level of posterior margin of vitelline field.

Testis subspherical, intercaecal, length h 85, c 68 (51–95, n = 11), width h 142, c 116 (54–188, n = 11). Vas deferens emerges from antero-sinistral part of testis, enlarges into seminal vesicle; seminal vesicle in middle region of body, transforms into duct; duct forms bends then connects with quadriloculate organ. Prostatic reservoir small, connects with quadriloculate organ. Quadriloculate organ with fourth (posterior) chamber slightly more sclerotised than 3 anterior chambers; fourth chamber ends in short sclerotised cone, prolonged by sclerotised tube; diameter of tube regular; end of tube prolonged by thin unsclerotised filament of variable length. Inner length of quadriloculate organ h 42, c 43 (40–49, n = 13), p 59 (55–68, n = 10); cone length h 9, c 9 (8–11, n = 13), p 10 (8–12, n = 10); tube length h 28, c 21 (19–26, n = 13), p 19 (16–21, n = 10); tube diameter h 3, c 2 (2–3, n = 13), p 3 (2–3, n = 10); filament length h 6, c 0–37 (n = 13), p 0–29 (n = 10).

Ovary subequatorial, intercaecal, pre-testicular, encircles right caecum. Ovary width h 95, c 78 (41–114, n = 12). Oviduct passes medially to form oötype, surrounded by Mehlis’ gland; oötype short, opens into uterus. Uterus dextral. Unsclerotised vagina often inconspicuous. Duct from sclerotised vagina to oötype inconspicuous. Vitelline fields extend posteriorly from posterior to pharyngeal level in 2 lateral bands, confluent in post-testicular region and terminate anterior to peduncle. Bilateral connections from vitelline fields to oötype inconspicuous. Egg in utero elongate, c 68–70 x 31–47 (n = 2), uc 95 x 36 (83–105 x 30–41, n = 8); this species had a higher proportions of specimens with eggs than the others.

Sclerotised vagina (nomenclature of parts according to Justine 2007a; see Figure 12) sinistral, a complex sclerotised structure; aspect changes according to specimen and orientation ( Figure 9). Sclerotised vagina comprises anterior trumpet, followed by coiled primary canal, primary chamber and secondary chamber; trumpet surrounded by heavily sclerotised irregular ring; primary canal cylindrical, always coiled once; canal continues into primary chamber; primary chamber small, ovoid, aligned and in continuity with primary canal; wall of primary chamber thick; secondary canal very thin, follows wall of primary canal and connects with anterior part of primary chamber; secondary chamber sclerotised, spherical, ventral to primary chamber; accessory structure small, inserted on secondary chamber, often inconspicuous. Duct from sclerotised vagina to oötype connects to secondary chamber ( Figure 9L). Total length of sclerotised vagina (measured from extremity of trumpet to posterior extremity, i.e. not taking in account curved length along bend and coil of canal) h 37, c 36 (30–40, n = 13), p 40 (34–45, n = 10); external diameter of primary chamber h 6, c 6 (4–7, n = 13), p 7 (6–8, n = 10); internal diameter of primary chamber h 2, c 2 (2–3, n = 13), p 3 (2–4, n = 10); external diameter of secondary chamber h 7, c 6 (5–8, n = 13), p 8 (6–10, n = 10); internal diameter of secondary chamber h 3, c 34 (2–3, n = 13), p 3 (2–74, n = 10). Orientation of sclerotised vagina: trumpet always anterior.

Remarks on a juvenile specimen. We report observation on a specimen in which the sclerotised vagina was already fully formed, thus allowing identification of the species. Measurements were: body length 425 (82% of adult mean), width 170 (52%), haptor width 200 (100%). Haptoral hard parts were of adult size. The male quadriloculate organ (inner length 45) and sclerotised vagina (length 31) had adult sizes, but their development was not completed. The sclerotised vagina ( Figure 8C) was almost similar to an adult organ, but the walls of the primary canal, primary chamber and secondary chamber were thinner than in adult organs, and the sclerotised ring around the trumpet was absent. The quadriloculate organ ( Figure 8B) had a more elongate general shape and much thinner external walls than an adult organ, and the cone and tube were indistinguishable. We conclude that the development of the female organs was more advanced than that of the male organs in this juvenile. These observations are similar to that done in an immature of P. manifestus Justine & Sigura, 2007 ( Justine & Sigura 2007), particularly in the late differentiation of the tube and cone of the quadriloculate organ.

Differential diagnosis. P. chauveti is very similar to P. euitoe Justine, 2007 , from E. maculatus off New Caledonia (Justine, 2007). Similarities include the shape of the sclerotised vagina, with similar general shape and presence of an heavily sclerotised ring around the trumpet. However, the trumpet ring is much more developed in P. chauveti than in P. euitoe . In addition, P. chauveti has longer ventral hamuli (outer length 42 vs 34), longer dorsal hamuli (outer length 37 vs 31), longer dorsal bars (61 vs 52) and especially a longer ventral bar (91 vs 68) than P.euitoe .

P. hirundineus Justine, 2005 , from Variola louti (Forsskål) off New Caledonia ( Justine, 2005b) is also similar to P. chauveti in the general shape of its sclerotised vagina. Again, P. chauveti can be differentiated by its heavily sclerotised ring around the trumpet, not found in P. hirundineus . The shape of the secondary chamber is also different (round in P. chauveti vs elongate in P. hirundineus ). In addition, P. chauveti has longer haptoral hard parts, especially the ventral bar (91 vs 71 in P.hirundineus ).

In the three species, the ventral and dorsal squamodiscs are dissimilar within a species, with in each case an elongate dorsal squamodisc and a round ventral squamodisc. However, the numbers of rodlets in the ventral squamodisc of each species are different, with 191 in P. chauveti , 135 in P. euitoe and 132 in P. hirundineus , and a dorsal squamodisc with respectively 200, 112 and 117 rodlets. The dorsal squamodisc of P. chauveti has more rodlets (200 vs 191) that the ventral squamodisc, a character not found in the other two species and probably not found in other species of Pseudorhabdosynochus , in which the ventral squamodisc is generally larger than the dorsal one.

These three species are clearly closely related, but P. chauveti can be distinguished by details of the morphology of the sclerotised vagina and by different measurements of the haptoral hard parts.