Procamallanus (Spirocamallanus) hexophtalmatis Moravec & Justine 2019, n. sp.

Procamallanus (Spirocamallanus) hexophtalmatis n. sp.

Figures 5, 6

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Type host: Speckled sandperch Parapercis hexophtalma (Cuvier) (Pinguipedidae, Perciformes).

Site of infection: Intestine.

Type locality: Near Récif Toombo, off Nouméa, New Caledonia, 22°32 0 934 S, 166°28 0 549 E (collected 4 November 2008).

Prevalence, intensity and details about fish: 1 fish infected/ 2 fish examined; 4 nematodes (Fish number: JNC 2736). The infected fish was 185 mm in fork length and 68 g in weight.

Deposition of type specimens: Helminthological Collection, Institute of Parasitology, Biology Centre of the Czech Academy of Sciences, České Budějovice, Czech Republic (male holotype and female allotype, both mounted on SEM stub, N–1202); Muséum National d’ Histoire Naturelle, Paris, France (two paratypes, MNHN JNC 2736).

Etymology: The specific name of this nematode relates to the genitive form of the species name of the host.

Description

General: Medium-sized nematode with finely transversely striated cuticle. Mouth aperture oval, surrounded by 12 submedian cephalic papillae arranged in three circles, each formed by four papillae; papillae of outer circle distinctly larger; each of four small inner papillae present near margin of oral aperture accompanied by distinct proximal pore; pair of small lateral amphids present (Figs. 5D, 6A and 6B). Buccal capsule orange, thick-walled, longer than wide, with simple, well-developed basal ring. Maximum width/length ratio of buccal capsule 1:1.25–1.27. Inner surface of capsule provided with 11–12 spiral ridges in lateral view, of which three incomplete (Figs. 5B, 5C and 5E). Muscular oesophagus shorter than glandular oesophagus; both parts of oesophagus somewhat expanded near their posterior ends (Fig. 5A). Intestine brown, narrow. Deirids small, simple, with rounded end situated just anterior to level of nerve ring (Figs. 5A, 5B, 5E, 5K and 6G). Excretory pore located at level of junction of both parts of oesophagus (Fig. 5A).

Male (one complete specimen, holotype; measurements of one incomplete specimen in parentheses): Length of body 15.52 (body with missing posterior end 10.74) mm, maximum width 272 (231). Buccal capsule including basal ring 84 (75) long, its width 66 (60); basal ring 9 (6) long and 42 (39) wide. Maximum width/length ratio of buccal capsule 1:1.27 (1:1.25). Spiral ridges 12 (11) in number, 3 (3) incomplete. Length of muscular oesophagus 394 (354), maximum width 81 (69); length of glandular oesophagus 598 (558), maximum width 111 (72); length ratio of muscular and glandular oesophagus 1:1.52 (1:1.58). Length of entire oesophagus and buccal capsule representing 7 (–)% of body length. Deirids, nerve ring and excretory pore 222 (219), 258 (245) and 503 (435) from anterior extremity, respectively. Posterior end of body ventrally bent, provided with wide, vesiculated caudal alae supported by pedunculate papillae; anteriorly alae interconnected by mound, forming a kind of pseudosucker, and posteriorly reaching to caudal terminal spines (Figs. 5F, 5G, 6C and 6D). Preanal papillae: three pairs of subventral pedunculate papillae, of which second and third pairs closer to each other than first and second pairs; postanal papillae: six pairs of pedunculate papillae, four subventral and two lateral (last pair representing phasmids); additional two pairs of small, transversely-elongate sessile ventral papillae surrounding cloacal opening (Figs. 5F and 5G). Spicules unequal, with sharply pointed distal ends; large (right) spicule 324 (–) long; small (left) spicule less sclerotized, 180 (–) long (Fig. 5F). Length ratio of spicules 1:1.80 (–). Gubernaculum absent. Tail conical, 164 (–) long, with two (dorsal and ventral) small terminal cuticular spines 3 (–) long (Figs. 5F and 5G).

Female (one larvigerous specimen, allotype; measurements of one incomplete ovigerous specimen in parentheses): Length of body 24.00 (body with missing anterior end 14.31) mm, maximum width 571 (394). Buccal capsule including basal ring 99 (–) long and 78 (–) wide; basal ring 9 (–) long and 54 (–) wide. Maximum width/length ratio of buccal capsule 1:1.27 (–). Number of spiral ridges 11 (–). Length of muscular oesophagus 476 (–), maximum width 108 (–); length of glandular oesophagus 816 (–), maximum width 138 (–); length ratio of muscular and glandular oesophagus 1:1.71 (–). Length of entire oesophagus and buccal capsule representing 6 (–)% of body length. Deirids, nerve ring and excretory pore 299 (–), 313 (–) and 585 (–), respectively, from anterior extremity. Vulva pre-equatorial, 11.70 (–) mm from anterior extremity, at 49 (–)% of body length. Vulval lips not elevated. Vagina directed anteriorly from vulva. Uterus filled with numerous larvae 444–480 long and six in maximum width with slender tail (uterus with eggs); tail tip of larvae provided with six digital processes (Figs. 6E and 6F). Female tail broad, rounded, its posterior end abruptly narrowed to form digit-like protrusion provided with 2 (2), dorsal and ventral, small terminal cuticular spikes; length of entire tail 82 (58); digit-like protrusion 39 (21) long, 15 (12) wide, length of spines 3 (3) (Figs. 5H, 5I and 5J).

Remarks

As with the previous species, P. (S.) hexophtalmatis n. sp. also belongs to the morphological group of species of the subgenus Spirocamallanus characterized by the presence of wide caudal alae, three pairs of pedunculate preanal papillae, two unequal spicules and two caudal spikes on a digital projection in the female (see above). Of the species of this group occurring in the Indo-Pacific region, based on the length of the right spicule, P. hexophtalmatis n. sp. is similar to P. anguillae (289–384 µm vs 324 µm), P. gobiomori (318–348 µm), P. guttatusi (204– 350 µm), P. istiblenni (263–302 µm), P. monotaxis (279– 315 µm), P. rigbyi (315–360 µm) and P. variolae (327–357 µm) [17, 22, 25, 26, 29 – 31, 33, 35, 40, 46].

However, all these species, except for P. variolae, have deirids situated near the mid-point between the base of the buccal capsule and the nerve ring (vs deirids situated just anterior to the nerve ring). Based on this feature, the new species resembles only P. variolae, in which, however, the deirids are located slightly posterior (vs anterior) to the level of the nerve ring. Although P. variolae and P. hexophtalmatis n. sp. have the same numbers (11–12) of spiral ridges in the buccal capsule and the body lengths of their gravid (larvigerous) females are identical (approximately 24 mm), the new species differs from P. variolae in the length ratio of the muscular and glandular portions of the oesophagus (1: 1.5–1.6 in males and 1: 1.7 in the gravid female vs 1: 1.1–1.3 in males and 1: 1.3 in the gravid female), location of the excretory pore at the level of the muscular and glandular oesophageal junction (vs somewhat posterior to this junction) and in that the vagina of the gravid female is directed anteriorly (vs posteriorly) from the vulva. Whereas the tail of both gravid and subgravid females in the new species is widely rounded (Figs. 5H and 5I), that of the gravid female of P. variolae is somewhat more conical. Moreover, both these species differ in the family of their fish hosts (Pinguipedidae vs Serranidae).

In addition to a different location of deirids (see above), P. anguillae, P. istiblenni, P. monotaxis and P. rigbyi usually have more numerous spiral ridges in the buccal capsule (10–15, 12–15, 10–17 and 13–14, respectively vs 11–12), whereas the ridges of P. gobiomori are less numerous (8–10). These five species also differ from P. hexophtalmatis n. sp. in the family of their hosts (Anguillidae, Blenniidae, Lethrinidae, Sciaenidae and Eleotridae, respectively vs Pinguipedidae).

Moravec et al. [27] reported Procamallanus (Spirocamallanus) sp. 1 from P. hexophtalma in New Caledonia. However, although the general morphology of the only available specimen (subgravid female) was similar to that of P. hexophtalmatis n. sp., the spiral ridges in its buccal capsule were more numerous (16), deirids were located approximately at 2/3 of a distance between the base of the buccal capsule and the nerve ring and its tail was more conical as compared with that of the subgravid female of P. hexophtalmatis, resembling thus P. monotaxis [27]. Therefore, allocation of this specimen to P. hexophtalmatis is uncertain. Rigby and Adamson [39] reported P. monotaxis, originally described from a lethrinid fish from Hawaii [35], from Parapercis millepunctata (Günther) and members of several other fish families in French Polynesia, but this identification needs to be confirmed. In New Caledonia, P. monotaxis was recorded only from Lethrinus spp. [25].

The SEM examination of the first-stage larva of P. hexophtalmatis shows that the tail tip bears six digitiform processes (Figs. 6E and 6F). Similar caudal processes were previously observed in first-stage larvae of Camallanus cotti and C. lacustris [24] and those of two Procamallanus species from African freshwater fishes [18]. Apparently, these caudal processes serve the larva to better attach by its tail to the bottom, after the larvae are released into the water [24].