Pseudorhabdosynochus podocyanus, 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 : 11-16

Pseudorhabdosynochus podocyanus n. sp.

( Figs 5–6)

Type host: Epinephelus cyanopodus Richardson (Serranidae) .

Type locality: Lagoon off Nouméa, New Caledonia.

Site: Between secondary gill lamellae.

Type specimens: Holotype, JNC1660 A25, Passe de Dumbéa , off Nouméa, New Caledonia (22°20’S, 166°15’E, 25.xi.2005).

Material examined: 51 specimens including 13 ‘carmine’ (c) and 1 ‘picrate’ (p).

Material deposited: Holotype (c) and 38 paratypes (7 c, 30 uc, 1 p), MNHN, JNC546 , 1625 , 1626 , 1660 ; paratypes, BMNH 2007.11.23.3. (c), 2007.11.23.4 (uc); USNPC 100400 (c), 100401 (uc); SAMA AHC 29296 (uc); M-458 (1 c, 1 uc); SZU 2007112102-1 (uc).

Prevalence: 35 % (6/17) in all fish (Table 2); 50% (6/12) in large fish with ‘specific’ fauna ( Table 10) in which it was the rarest species.

Intensity: See Table 2; maximum calculated intensity 14; this species represented 3.5% of the total number of monogeneans.

Etymology: An anagram based on the host name, cyanopodus .

Description. [Measurements based on 12 carmine specimens and 1 picrate specimen]. Body length h 330, c 420 (300–570, n = 11), width h 250, c 266 (170–320, n = 11). Tegument scaly; posterior region with scales on ventral and dorsal faces from squamodiscs to 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 26, c 34 (24–44, n = 11), of posterior eye-spot pair h 21, c 29 (21–37, n = 11).

Haptor differentiated from rest of body, less wide than body, width h 140, c 151 (130–190, n = 11), provided with 2 similar squamodiscs, 2 pairs of lateral hamuli, 3 bars and 14 marginal hooklets.

Squamodiscs round in shape, made up of rows of rodlets; central row sometimes forming closed oval; 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 similar; ventral squamodisc length h 70, c 65 (59–71, n = 10), width h 71, c 73 (68–82, n = 10), with h 14, generally 14 (13–15, n = 10) rows of rodlets and 0–1 closed oval; total number of rodlets h 188, mean 188 (161–201, n = 8, individual variations in Table 4); dorsal squamodisc, length h 74, c 68 (60–76, n = 10), width h 68, c 64 (56–70, n = 10), with h 15, generally 14 (13–15, n = 10) rows of rodlets and 0–1 closed oval; total number of rodlets h 165, mean 182 (165–209, n = 8, individual variations in Table 4).

* Holotype, drawn in Figs 6A, B; v, central row ‘v-shaped’ almost close; i, incomplete row.

Ventral hamulus with thick handle and distinct guard, outer length h -, c 36 (32–39, n = 14), p 40 (n = 2), inner length h 25, c 28 (25–30, n = 14), p 30 (n = 2). Dorsal hamulus with indistinct guard, outer length h -, c 32 (30–34, n = 18), p 33, (n = 2), inner length h -, c 20 (18–22, n = 15), p 21 (n = 2). Dorsal (lateral) bars straight, with flattened medial extremity and cylindrical lateral extremity, length h 51, c 52 (48–55, n = 22), p 60 (n = 2), maximum width h 15, c 15 (12–18, n = 19), p 17 (n = 2). Ventral bar flat, with slightly constricted median portion and blunt extremities, length h 77, c 78 (73–84, n = 11), p 83 (n = 1), maximum width h 11, c 12 (11–13, n = 11), p 14; groove visible on its ventral side.

Pharynx subspherical, length h 30, c 42 (30–51, n = 11), width h 28, c 34 (26–43, n = 14). 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 42, c 62 (40–93, n = 10), width h 90, c 87 (40–138, n = 10). 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 transforms into small bulb, followed by duct; duct connects with quadriloculate organ. Prostatic reservoir small, connects with quadriloculate organ. Quadriloculate organ with fourth (posterior) chamber slightly more sclerotised than 3 anterior chambers; first chamber with very thin anterior wall; fourth chamber ends in short sclerotised cone, prolonged by sclerotised tube; tube slightly wider at extremity than at base; end of tube prolonged by thin unsclerotised filament of variable length. Inner length of quadriloculate organ h 43, c 42 (38–46, n = 11), p 55; cone length h 5, c 6 (5–18, n = 11), p 6; tube length h 23, c 21 (19–25, n = 11); tube diameter at base h 3, c 3 (2–4, n = 11); tube diameter at extremity h 4, c 4 (3–5, n = 11); filament length h 7, c 4–13 (n = 9).

Ovary subequatorial, intercaecal, pre-testicular, encircles right caecum. Ovary width h 63, c 59 (33–77, n = 11). Oviduct passes medially to form oötype, surrounded by Mehlis’ gland; oötype short, opens into uterus. Uterus dextral. Unsclerotised vagina often inconspicuous, elongate. 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 unknown.

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 5). Sclerotised vagina comprises anterior trumpet, followed by straight primary canal, primary chamber and secondary chamber; primary canal cylindrical; longitudinal axis of primary canal often forming angle with longitudinal axis of primary chamber; canal continues into primary chamber; primary chamber large, pear-shaped, in continuity with primary canal; wall thick; secondary canal inserted on anterior part of primary chamber; secondary chamber sclerotised, spherical, ventral to primary chamber; accessory structure, curved, weakly sclerotised, inserted on secondary chamber and directed anteriorly. External surface of primary chamber smooth, internal surface with irregular ornamentation in anterior region, smooth in posterior region; no interior crest. Duct from sclerotised vagina to oötype connects to secondary chamber. Total length of sclerotised vagina h 29, c 28 (24–30, n = 11), p 33; external width of primary chamber h 12, c 11 (10–13, n = 11), p 14; internal maximum width of primary chamber h 9, c 8 (6–8, n = 11), p 12; internal maximum width of secondary chamber h 3, c 3 (2–4, n = 11), p 3. Orientation of sclerotised vagina: trumpet always anterior.

Differential diagnosis (in common with P. cyanopodus ). P. cyanopodus and P. podocyanus share the following characteristics of the sclerotised vagina: an anterior trumpet, a straight primary canal, a conspicuous heavily sclerotised primary chamber, and a smaller secondary chamber. Comparisons are here restricted to species with a distinct primary canal and large, heavily sclerotised chambers.

Four species have a coiled or curved primary canal, vs straight: P. malabaricus Justine & Sigura, 2007 and P. maternus Justine & Sigura, 2007 , both from E. malabaricus off New Caledonia, P. minutus Justine, 2007 from Cephalopholis sonnerati (Valenciennes) off New Caledonia and P. fuitoe Justine, 2007 , from E. macula- tus off New Caledonia ( Justine 2007a, b; Justine & Sigura 2007). In addition, the latter has a long, heavily sclerotised secondary canal, vs short.

P. venus Hinsinger & Justine, 2006 , from E. howlandi (Günther) off New Caledonia, has a pear-shaped primary chamber resembling that of P. podocyanus , but the primary canal is curved and the vagina is very large (total length 55) ( Hinsinger & Justine 2006a).

P. bacchus Sigura, Chauvet & Justine, 2007 , from E. coeruleopunctatus (Bloch) off New Caledonia, has a generally similar structure of the vagina but the primary chamber is very small, vs large ( Sigura, Chauvet & Justine 2007).

P. vagampullum ( Young, 1969) Kritsky & Beverley-Burton, 1986 from E. quoyanus (Valenciennes) off South China and Australia, has been redescribed by Beverley-Burton & Suriano (1981), Justine (2005a), and Zeng & Yang (2007). It is differentiated by the relative proportions of the primary canal and primary chamber, its wide cylindrical primary canal (vs shorter in the two species from E. malabaricus ) and the insertion of the secondary chamber in the posterior part of the primary chamber (vs anterior insertion).

P. auitoe Justine, 2007 , from E. maculatus off New Caledonia, is the species most resembling P. cyanopodus . The species has a very similar structure of the sclerotised vagina, and very similar measurements of the main sclerotised organs (ventral hamulus outer length 35 vs 36, dorsal hamulus outer length 33 vs 36, dorsal bar length 58 vs 60, ventral bar length 76 vs 84, quadriloculate organ inner length 51 vs 51. It can be differentiated by its short primary canal (longer in P. cyanopodus ), and absence of an interior crest in the primary chamber (present in P. cyanopodus ). The two species P. auitoe and P. cyanopodus are clearly very closely related.

The two new species P. cyanopodus and P. podocyanus are similar in many measurements ( Table 7) such as the length of the ventral and dorsal hamulus, of the ventral bar, and differ only slightly in lateral bar lengths (59 vs 52); both species have large squamodiscs with similar rodlet counts; for the quadriloculate organ, proportions and measurements of cone and tube are similar, but the inner length is slightly greater in P. cyanopodus (51 vs 42). The general structure of the vagina is similar in both species, but the shapes are clearly different. This distinction can be made on the following characters: longer primary canal in P. cyanopodus ; shape of primary chamber ovoid in P. cyanopodus vs pyriform in P. podocyanus ; presence of an interior crest in P. cyanopodus , absent in P. podocyanus ; total vaginal length, greater in P. cyanopodus (38 vs 28), with no overlap. These two species are probably closely related but the structures of their sclerotised vaginae are clearly distinct.