Laticola cyanus, 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 : 29-35

Laticola cyanus n. sp.

( Figs 13–14)

Type host: Epinephelus cyanopodus Richardson (Serranidae) .

Type locality: Lagoon off Nouméa, New Caledonia.

Site: Between secondary gill lamellae.

Type specimens: Holotype, JNC1625 A41, Passe de Dumbéa , off Nouméa, New Caledonia (22°20’S, 166°15’E, 25.x.2005).

Material examined: 918 specimens, including 75 ‘carmine’ (c) and 1 ‘picrate’ (p).

Comparative material examined: Type specimens of Laticola dae Journo & Justine, 2006 , MNHN .

Material deposited: Holotype (c) and 296 paratypes (11 c, 284 uc, 1 p), MNHN JNC546 , 1625 , 1626 ; paratypes, BMNH 2007.11.23.12. (c), 2007.11.23.13–14 (2 uc); USNPC 100406 (c), 100407 (2 uc); SAMA

AHC 29303 (c), 29304–5 (2 uc); HCIP M-461 (1 c, 2 uc); SZU 2007112105-1 (c), 2007112105-2–3 (2 uc).

Prevalence: 41 % (7/17) in all fish (Table 2); 58% (7/12) in large fish with ‘specific’ fauna ( Table 10).

Intensity: See Table 2; maximum calculated intensity 600; this species represented 61% of the total number of monogeneans, 65% of the diplectanids, and was the most abundant..

Etymology: From the host name.

Description. Body length h 503, c 487 (400–540, n = 16), uc 479±64 (400–680, n = 30), width h 249, c 232 (150–285, n = 16), uc 147±27 (100–250, n = 30). 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 29, c 36 (29–42, n = 13), of posterior eye-spot pair h 36, c 32 (27–39, n = 12).

Haptor differentiated from rest of body, less wide than body, width h 160, c 153 (132–175, n = 13), uc 151±10 (120–160, n = 30), 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 rows forming closed circles; rodlet thickness similar from centre to periphery, except 2–3 last rows with thinner rodlets; rodlets adjacent in all rows except 3–4 last row; ventral and dorsal squamodiscs similar; ventral squamodisc length h 47, c 50 (44– 52, n = 13), uc 47 (41–51, n = 10), width h 50, c 49 (47–52, n = 13), uc 49 (46–52, n = 10), with h 12, generally 12 (11–12, n = 20) rows of rodlets and always 2 closed circles in centre; total number of rodlets h 86, mean 89 (80–99, n = 20, individual variations in Table 8); dorsal squamodisc, length h 49, c 48 (40–56, n = 12), uc 46 (41–51, n = 10), width h 48, c 50 (45–54, n = 12), with h 11, 9–13 (n = 14) rows of rodlets and always 2 closed circles in centre; total number of rodlets h 85, mean 89 (85–96, n = 14, individual variations in Table 8).

Ventral hamulus with distinct handle and guard, outer length h 42, c 42±1.0 (40–44, n = 28), inner length h 40, c 40±1.3 (37–42, n = 28). Dorsal hamulus with indistinct guard, outer length h 39, c 38±1.5 (34–40, n = 30), inner length h 22, c 22±0.8 (20–23, n = 28). Dorsal (lateral) bars straight, with flattened medial extremity and cylindrical lateral extremity, length h 49, c 50±1.5 (48–53, n = 29), maximum width h 14, c 14±1.8 (11–18, n = 28). Ventral bar flat, bow-shaped, with constricted median portion and blunt extremities, length h 62, c 66 (62–69, n = 15), maximum width h 10, c 10 (10–12, n = 15); groove visible on its ventral side.

Pharynx subspherical, length h 39, c 39 (33–42, n = 16), width h 40, c 38 (32–45, n = 16). Oesophagus apparently absent, such that intestinal bifurcation immediately follows pharynx. Caeca simple, terminate blindly at level of posterior margin of vitelline field.

Testis transversally elongate, intercaecal, length h 26, c 39 (23–103, n = 16), width h 105, c 72 (33–127, n = 16). Vas deferens inconspicuous; seminal vesicle inconspicuous. Prostatic glands conspicuous, form two large fields on both sides of body from pharynx to mid-length of penis; prostatic reservoir single, small, connects with penis. Penis “spoon-shaped”: a curved funnel, made up of anterior cone and straight posterior tube; tube wider at extremity than at base. Posterior limit of tube smooth (no striations). Within penis anterior cone, 4 thin transversal walls limit 4 chambers. Thin cirrus inside penis from most anterior part of cone to end of tube; cirrus often protruding from distal extremity of tube. Inner length of penis h 43, c 43 (42–53, n = 15), uc 47 (44–51, n = 6); outer length h 66, c 62 (54–68, n = 15), uc 58 (54–62, n = 6); tube diameter at base h 5, c 5 (5–6, n = 16), uc 6 (5–7, n = 9); tube diameter at extremity h 11, c 11 (10–13, n = 16), uc 11 (9–12, n = 9).

Ovary subequatorial, intercaecal, pre-testicular, encircles right caecum. Ovary width h 110, c 103 (74– 135, n = 16). Oviduct passes medially to form oötype, surrounded by Mehlis’ gland; oötype short, opens into uterus. Uterus dextral, with thick wall. Vagina sinistral; unsclerotised vagina inconspicuous in preserved slides. No seminal receptacle seen. Sclerotised vagina a disc, with smaller hemisphere on one side. Small dorsal structure, heavily sclerotised, containing one chamber. Diameter of sclerotised disc h 15, c 15 (14–16, n = 16), uc 15 (14–16, n = 10). Egg xx.

* Holotype, drawn in Figs. 13D, 14U; c, closed central row; i, incomplete row.

Note on a juvenile specimen. In a juvenile specimen (body length 280, 58% of adult size), the general structure of the sclerotised vagina was similar to that of adult specimens but the diameter of the disc was smaller (12 vs 15, 80%) and the small dorsal structure had a thin wall (vs heavily sclerotised) ( Fig. 14J).

Differential diagnosis. Laticola was created to accommodate the diplectanids from Lates calcarifer (Bloch) . Some confusion exists with three papers (Wu & Li 2005; Wu, Li, Zhu & Xie 2006; Yang, Kritsky, Sun, Zhang, Shi & Agrawal 2006) describing almost simultaneously these monogeneans, added to multiple previous descriptions of the same species (see Yang et al. 2006). Pseudorhabdosynochus yangjiangensis Wu & Li has been considered a junior synonym of L. paralatesi ( Nagibina, 1976) Yang et al., 2006 ( Yang et al. 2006). Pseudorhabdosynochus seabassi Wu, Li, Zhu & Xie, 2005 is certainly a species of Laticola , and has a thistle-shaped vagina which resembles that of L. lingaoensis Yang et al., 2006 ; if this synonymy is ascer- tained, L. lingaoensis , the type-species of Laticola will have to be renamed L. seabassi , because of priority in description. Formal nomenclatural changes are not proposed here because they would require examination of all type specimens, a task beyond the scope of this paper.

Notwithstanding the nomenclatural problems stated above, it seems that only 4 species are known in Laticola prior to the current description of a new species ( Table 9). Three are parasites of Lates calcarifer (Centropomidae) and one is a parasite of E. maculatus (Serranidae) . Measurements are of little help for differentiating the species ( Table 9). L. latesi (Tripathi, 1957) Yang et al., 2006 is immediately differentiated from all other species by presence of a single squamodisc. Based on the morphology of the vagina, two groups can be differentiated: one group without a discoid sclerotised vagina, including L. latesi , L. lingaoensis , and L. paralatesi , and a group with a discoid sclerotised vagina, including L. dae Journo & Justine, 2006 and L. cyanus .

* ‘Length’ for the three first species; outer length for the latter 2 species.

L. cyanus can be differentiated from the three species from Lates calcarifer by the presence of a discoid sclerotised vagina. It can be differentiated from L. dae , from E. maculatus in New Caledonia, which shares the presence of a sclerotised discoid vagina, by a smaller penis length (62 vs 94), smaller diameter of the sclerotised vagina (15 vs 19) and fewer closed circles in the squamodiscs (2 vs 2–3). In addition, the distal extremity of the penis in L. cyanus is smooth while that of L. dae has longitudinal striations.

Relationships of Laticola spp. with a group of species of ‘ Diplectanum’ with a similar ‘spoon-shaped’ penis, but which is much smaller, remain to be clarified ( Justine, 2007a, b); these species are D. grouperi Bu et al., 1999 from E. coioides , D. uitoe Justine, 2007 from E. maculatus ; D. nanus Justine, 2007 , from C. sonnerati , and D. maa Justine & Sigura, 2007 from E. malabaricus .

Remarks. Although certain species of Pseudorhabdosynochus are shared between E. maculatus and young E. cyanopodus , it is worth mentioning that no specimen of L. dae was found in E. cyanopodus , suggesting strict specificity for this species of Laticola .

Composition of the diplectanid fauna in the two fish, E. maculatus and E. cyanopodus , shows striking similarities, with, in each case, a dominant species (a species of Laticola in both fish) and a series of rarer species (nine species of Pseudorhabdosynochus and Diplectanum in E. maculatus , four species of Pseudorhabdosynochus in E. cyanopodus ). Clearly, species of Laticola are the main diplectanids in each of these two fish species, and this situation contrasts dramatically to that found in other groupers: more than 20 species of groupers have been investigated in New Caledonia, and others in other locations, and no species of Laticola has been reported from these other species. Close phylogenetic relationships exist between E. maculatus and E. cyanopodus (Damien Hinsinger, unpublished, based on genetic analysis). It is likely that a common ancestor of these two species has acquired a species of Laticola , which later differentiated into two different species, one in each fish species.

The sharing of some monogenean species by E. cyanopodus and E. maculatus warrants some comment:

— E. maculatus has eight species of Pseudorhabdosynochus . Of these, only two were found in very small number in young E. cyanopodus , suggesting that the six other species have a very strict specificity.

— The relative abundance of diplectanids in E. maculatus is strikingly different between L. dae , the most abundant species with almost 50% of the specimens, and the species of Pseudorhabdosynochus , each with 2– 7% of the total; however, specimens of L. dae were not found in E. cyanopodu s. This means that infection of E. cyanopodus is not a function of the relative abundance of infective stages of monogeneans from E. maculatus , but that specificity plays a role; P. duitoe and P. huitoe are apparently the only species able to switch hosts.

— No specimens of P. duitoe or P. huitoe were found in older E. cyanopodus , showing that the apparently ‘accidental’ infection by these species is later lost by older specimens. Perhaps host immunity is stronger in old E. cyanopodus , which discard the few monogeneans they acquired in their youth.