Huffmanela ossicola Justine, 2004

Justine, Jean-Lou, 2007, Huffmanela spp. (Nematoda, Trichosomoididae) parasites in coral reef fishes off New Caledonia, with descriptions of H. balista n. sp. and H. longa n. sp., Zootaxa 1628, pp. 23-41 : 35-37

Huffmanela ossicola Justine, 2004

( Figs 6–7 )

New host records and information on prevalence: Bodianus loxozonus (type-host): prevalence 4/11 (36 %). Details for additional infected specimens: JNC1087, Récif To, 22°29'30''S, 166°26'E, 28.iv.2004, FL 250, W 319; JNC1468, Récif Le Sournois (RLS), 22°31’S, 166°26’E, 8.iii.2005, FL 605, W 555; JNC1866, Récif Tabou, 15.vi.2006, FL 285, W 524; non infected specimens of similar sizes.

Bodianus busellatus Gomon, 2006 : prevalence 1/3 (33%). New host record. Details for infected specimen: JNC1221, near Récif Toombo, 22°32’S, 166°28’E, 10.viii.2004, FL 270, W 371; non infected specimens of similar sizes.

Bodianus perditio (Quoy & Gaimard) : prevalence 4/12 (25%). Host record briefly mentioned in Lim & Justine (2007). This contradicts the statement based on examination of two uninfected specimens ( Justine, 2004), that B. perditio was not a host. Details for infected specimens: JNC1469, RLS, 8.iii.2005, FL435, W 1600; JNC1526, Récif Aboré, 22°21’S, 166°16’E, FL 450, W 1900; JNC1969, RLS, 3.x.2006, FL 375, W 1050; JNC 2171, Récif Toombo, 30.v.2007, FL 253, W 312; non infected specimens of similar sizes.

Only heavy infections with numerous dark eggs were detected by examination of gill arch bones; it is likely that light infections, or recent infections with uncoloured eggs were not detected, and prevalences indicated above are probably underestimates.

Thirteen other species of labrids were examined, including a single specimen of Bodianus axillaris (Bennett) , and various numbers of Cheilinus chlorourus (Bloch) , C. trilobatus Lacepède , C. undulatus Rüppell , Choerodon fasciatus (Günther) , C. graphicus (De Vis) , Coris aygula Lacepède , Epibulus insidiator (Pallas) , Oxycheilinus diagrammus (Lacepède) , O. unifasciatus (Streets) , Stethojulis strigiventer (Bennett) , Thalassoma lutescens (Lay et Bennett) and T. nigrofasciatum Randall , and none was found to harbour H. ossicola in the gill archbones. In addition, gills from more than 200 non-labrid fish species were examined and no H. ossicola was found.

Gomon (2006) revised Bodianus , recognized ten subgenera, and grouped B. loxozonu s, B. busellatus and B. perditio , with six other species, within the subgenus Diastodon Bowdich ; in contrast, B. axillaris was classified within the subgenus Lepidaplois . Results suggest that H. ossicola is specific to members of Bodianus (Diastodon) .

Comparison of eggs between the different hosts. Table 5 shows that measurements were not exactly similar in each individual fish. In the type-host, B. loxozonus , length means ranged between 75.6–80.1. Measurements of egg lengths in the two other hosts, B. busellatus and B. perditio , fall within this range. One of the B. perditio specimens had egg widths greater than in other specimens.

* syntypes.

The morphology of eggs and especially aspects of the egg envelope with numerous thin filaments were similar in all hosts and organs. Length and width variations are interpreted as individual variation and it is concluded that it was the same species in the three hosts.

Comparison of egg measurements according to organ. In the original description ( Justine 2004), it was shown that small differences could be detected between eggs from different organs. In B. busellatus , measurements of eggs from the gills and the spinal cord were compared to the measurements of the syntypes from B. loxozonus ( Table 6 ). In B. loxozonus , the eggs were longer in the gills than in the spinal cord (81 vs 77 µm); in B. busellatus , in contrast, eggs were longer in the spinal cord (77 vs 75), and eggs were even shorter in the skull. However, all these variations were minor and the species can be recognized whatever the organ of origin, by its characteristic egg envelope and numerous filaments.

Hatching of larvae. Justine (2004) reported that no spontaneously hatched larva was found, even after incubation for four months in seawater. A similar experiment with B. perditio (JNC1526) with eggs from arch gill bones and with B. loxozonus (JNC1087) with eggs from arch gill bones and skull in saline gave similar negative results, i.e. no hatching was observed. Observation on eggs from several hosts also confirmed the original observation that larvae were immotile within eggs. In contrast, for fish JNC2171 ( Bodianus perditio ), slides prepared with tissue from the gills in saline or seawater showed numerous spontaneously hatched larvae, which showed feeble motility. Free L 1 larvae were 228 in length (200–265, n = 6) and 10 in maximum width. Why these specimens behaved differently than the others is unresolved. It is unlikely that these eggs were older and more mature than in other specimens because the fish was one of the smallest examined for this species.

X-ray examination of the skeleton of infected hosts. Two B. perditio of similar size were compared, one heavily infected (JNC1469), and one not infected. X-ray observations were done with the same X-ray apparatus with the same settings. Figure 7 shows the spinal cord in the two fish. No difference could be detected in the aspect or width of the spinal cord. It is concluded that the infection by H. ossicola does not alter the structure of the bones of the spinal cord.

It is possible, however, that the bone infection produces pain and thus perturbs the swimming of the infected fish, thus enhancing the probability of the fish being caught by a predator, and thus facilitating completion of the life-cycle.

Figures

FIGURE 7. X-ray photographs of the spinal cord in two Bodianus perditio. A. Specimen not parasitized by Huffmanela ossicola. B. Specimen heavily parasitized by Huffmanela ossicola. Negative prints.

FIGURE 6. A. Egg of Huffmanela mexicana Moravec et Fajer-Avila, 2000, for comparison with other species. B – D. Hatching eggs and larvae of Huffmanela ossicol a Justine, 2004 from the gills of Bodianus perditio.