Systematic Parasitology (2006) 64:131–145 DOI 10.1007/s11230-006-9034-x
Springer 2006
Three nematode species from elasmobranchs off New Caledonia Frantisˇ ek Moravec1,* & Jean-Lou Justine2 Institute of Parasitology, Academy of Sciences of the Czech Republic, Branisˇovska´ 31, 370 05, Cˇeske´ Budeˇjovice, Czech Republic 2 ´ Equipe Bioge´ographie Marine Tropicale, Unite´ Syste´matique, Adaptation, E´volution (UPMC, CNRS, MNHN, IRD), Institut de Recherche pour le De´veloppement, BP A5, 98848 Noume´a Cedex, New Caledonia 1
Accepted for publication 24th October, 2005
Abstract Nematode specimens of three species, Terranova scoliodontis (Baylis, 1931) (Ascaridida, Anisakidae), Echinocephalus sinensis Ko, 1975 and E. overstreeti Deardorff & Ko, 1983 (both Spirurida, Gnathostomatidae) were collected from the tiger shark Galeocerdo cuvier, the ray Aetobatus cf. narinari and the blotched fantail ray Taeniura meyeni, respectively, from the coastal waters of New Caledonia, South Pacific. Their examination, including scanning electron microscopy (SEM), made it possible to obtain some new data on their morphology, e.g. in relation to the number and arrangement of male caudal papillae in T. scoliodontis and both Echinocephalus spp., the presence of ventral cuticular ornamentations in T. scoliodontis and the number of transverse spines on the cephalic bulb in Echinocephalus spp. All these species are reported for the first time from New Caledonian waters and G. cuvier is a new host species for T. scoliodontis. SEM examination of the fourth-stage larvae of E. overstreeti from the type-host showed the presence of anterior dorsal and ventral groups of minute spines on the cephalic bulb to be an important taxonomic feature for the interspecific distinction of Echinocephalus larvae and questions previous data on the occurrence of E. overstreeti larvae in many elasmobranch fishes and molluscs in Australian waters. Re´sume´ Des Ne´matodes appartenant a` trois espe`ces, Terranova scoliodontis (Baylis, 1931) (Ascaridida, Anisakidae), Echinocephalus sinensis Ko, 1975 et E. overstreeti Deardorff & Ko, 1983 (tous deux Spirurida, Gnathostomatidae) ont e´te´ collecte´s respectivement du requin tigre Galeocerdo cuvier et des raies Aetobatus cf. narinari et Taeniura meyeni, des eaux coˆtie`res de Nouvelle-Cale´donie, Pacifique Sud. Leur e´tude, en particulier en microscopie e´lectronique a` balayage (MEB) a permis d’obtenir de nouvelles informations sur leur morphologie, par exemple sur le nombre et la disposition des papilles caudales maˆles chez T. scoliodontis et les deux espe`ces d’Echinocephalus, la pre´sence d’ornementations cuticulaires ventrales chez T. scoliodontis, et le nombre d’e´pines transversales sur le bulbe ce´phalique des Echinocephalus. Toutes ces espe`ces sont mentionne´es pour la premie`re fois des eaux de Nouvelle-Cale´donie et G. cuvier est un nouvel hoˆte pour T. scoliodontis. L’examen au MEB de la larve de quatrie`me stade d’E. overstreeti, provenant de l’hoˆte-type, a montre´ que les groupes ante´rieurs et poste´rieurs de petites e´pines sur le bulbe ce´phalique sont un caracte`re taxonomique important pour la distinction interspe´cifique des larves d’Echinocephalus et met en doute des informations ante´rieures sur la pre´sence de larves d’E. overstreeti chez de nombreux E´lasmobranches et Mollusques des eaux d’Australie.
*Author for correspondence (E-mail:
[email protected])
132 Introduction The taxonomy of nematodes of both the ascaridid genus Terranova Leiper & Atkinson, 1914 and the spirurid genus Echinocephalus Molin, 1858, which mainly comprise species from elasmobranchs, remains rather confused, mainly because of the inadequate descriptions of many species. Therefore, the only resolution of this unsatisfactory situation is a detailed study of available material, most of which has been newly collected, where new methods (e.g. SEM and DNA studies) can also be applied. Parasitological examinations of some large elasmobranchs off the southwestern coast of New Caledonia carried out in 2003 and 2004 revealed, among other helminths, adults of an anisakid and two gnathostomatid nematodes not previously recorded from New Caledonian waters. The results of detailed studies of these parasites are presented herein.
Materials and methods Elasmobranchs caught for this work are large species which are not usually examined and which require adapted means and special organisation for catching them and performing parasitological examination. Two blotched fantail rays Taeniura meyeni Mu¨ller & Henle were spear-fished off Noume´a, New Caledonia, along the internal part of the barrier reef, c.30 km offshore. Specimen JNC954 was a female, disc length 1.13 m, approx. weight 100 kg, caught 3 November 2003; specimen JNC955 was a male, disc length 1.00 m, approx. weight 50 kg, caught 4 November 2003. A female spotted eagle ray Aetobatus cf. narinari (Euphrasen), reference number JNC956, was spear-fished off Noume´a, New Caledonia (wingspan 590 mm, body length 320 mm, tail 1.2 m, weight 2.4 kg, date 5 November 2003, approx. location 2234¢S, 16640¢E). Because this ray belongs to a species complex, a line drawing of the dorsal spot pattern was published (Marie & Justine, 2005) for future identification of the specimen when the A.narinari species complex is resolved. All three rays were speared by Prof. Claude Chauvet (University of New Caledonia, Noume´a). Two tiger sharks Galeocerdo cuvier (Pe´ron & Lesueur) were line-caught in Baie de Prony, southern coast of New Caledo-
nia (2224¢S, 16653¢E). Specimen JNC1207 (female, total length 3.41 m, weight 250 kg) was caught for parasitological purposes (20 July 2004). Specimen JNC1414 (female, total length 3.40 m, weight unknown) was line-caught by local fishermen because it was considered a danger for children. In all cases, fish were obtained alive and the parasites collected were in excellent condition; the nematodes were fixed alive in hot 70% ethanol. However, specimens of Echinocephalus sinensis Ko, 1975 from A. cf. narinari were collected from the spiral intestine, which was fixed in formalin for cestodes. For light microscopical examination, they were cleared with glycerine. Drawings were made with the aid of a Zeiss microscope drawing attachment. Specimens used for scanning electron microscopy (SEM) were transferred to 4% formaldehyde solution and then postfixed in 1% osmium tetroxide, dehydrated through a graded ethanol series, critical point dried and sputtercoated with gold; they were examined using a JEOL JSM-6300 scanning electron microscope at an accelerating voltage of 15 kV. All measurements are in micrometres unless otherwise indicated. Fish names are according to Froese & Pauly (2005). Family Anisakidae Railliet & Henry, 1912 Terranova scoliodontis (Baylis, 1931) Johnston & Mawson, 1945 Syn. Porrocaecum scoliodontis Baylis, 1931 Host: Tiger shark, Galeocerdo cuvier (Pe´ron & Lesueur) (Carcharhinidae: Carcharhiniformes). Site: Stomach and intestine. Not in spiral intestine. Locality: South Pacific Ocean, off southern coast of New Caledonia, Baie de Prony, collected 20 July, 2004 and 22 November, 2004. Prevalence and intensity: 20 and 81 specimens found in two host sharks examined. Voucher specimens: Muse´um National d’Histoire Naturelle, Paris (JNC1207F, G, JNC 1414D,H,J) and Institute of Parasitology, ASCR, Cˇeske´ Budeˇjovice (N-847). Description (Figures 1, 2) General. Large, whitish nematodes with transversely striated cuticle. Maximum width near middle of body. Lips almost equal in size; anterior
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Figure 1. Terranova scoliodontis (Baylis, 1931). A, anterior end of male, lateral view; B, cephalic end of male, dorsal view; C,D, tail of male, lateral and ventral views; E, posterior end of male, lateral view; F, egg; G, tail of female, lateral view; H, distal end of spicule; I, caudal ornamentation of male, ventral view. Scale-bars: A,E, 1 mm; B,H,I, 100 lm; C,D, 200 lm; F, 30 lm; G, 500 lm.
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Figure 2. Terranova scoliodontis (Baylis, 1931), SEM micrographs. A, cephalic end, apical view; B, ventrolateral lip; C, cephalic end with distinct dorsal lip, subdorsal view; D, detail of denticles on lip, subapical view; E, posterior end of male with distinct caudal papillae and ventral postanal cuticular ornamentation, subventral view; F, pre-anal region of male with distinct pre-anal papillae and ventral pre-anal cuticular ornamentations, ventral view; G, deirid and lateral line, lateral view; H, detail of ventral pre-anal ornamentations of male, ventral view. Scale-bars: A-D,H, 10 lm; E,F, 100 lm.
135 margin of each lip formed into 2 widely separated lobes curved towards median line and median furrow, provided with continuous row of fine teeth (Figure 2A–D). Dorsal lip bearing 2 subdorsal double papillae in approx. its basal third (Figure 2C); each ventrolateral lip with 1 double subventral papilla, 1 small single papilla and minute amphid situated laterally (Figure 2B). Interlabia absent. Lateral alae indistinct, reduced to lateral grooves (Figure 2G). Deirids well developed, situated short distance posterior to level of nerve-ring (Figures 1A, 2G). Oesophagus long, narrow (Figure 1A). Ventriculus elongate, c.2.5 times shorter than oesophagus, with anterior and posterior ends usually somewhat expanded. Caecum long, extends considerably anterior to ventriculus (Figure 1A). Excretory pore situated ventrally between bases of ventrolateral lips (Figure 2A,B). Tail of both sexes conical. Male (5 specimens). Length of body 57.94– 78.62 mm, maximum width 1.56–2.18 mm. Lips 54–95 long. Length of oesophagus 3.33–4.35 mm (6–7% of body length), maximum width 258–326. Nerve-ring 748–925 from anterior extremity. Ventriculus 1.82–2.28 mm long, maximum width 313–380. Intestinal caecum 2.63–2.72 mm long, 272–283 wide. Posterior end of body curved ventrally. Spicules equal, 3.48–3.85 mm long, representing 4.5–6.6% of body length. Distal end of each spicule provided with transparent conical membrane (Figure 1H). Total of 26–29 pairs of small subventral papillae present, 22–24 being pre-anals, 1–2 adanals and 3 postanals; first pair of postanal papillae doubled. In addition to subventral postanal papillae, 2 pairs of lateral postanals present, 1 near mid-length of tail and 1 near tail tip. Median pre-anal papilla on anterior cloacal lip poorly developed. Well-developed plectane present posterior to cloacal aperture, being composed of 4 transverse cuticular plates with rounded lateral ends in ventral view; these ends resemble papillae in lateral view (Figure 1C). Ventral precloacal surface ornamented with modified annules forming 2 ventrolateral fields; each annule with row of minute longitudinal supports (crests) (Figure 2F,H). Tail 598–666 long, pointed. Female (3 specimens). Length of body 64.19– 79.08 mm, maximum width 2.22–2.45 mm. Lips 68–82 long. Length of oesophagus 3.99–4.65 mm,
representing 6% of body length; maximum width 313–435. Nerve-ring 884–925 from anterior extremity. Ventriculus 1.82–2.38 mm long, maximum width 340–449. Intestinal caecum 2.52– 3.16 mm long, 280–340 wide. Vulva situated 26.32–30.05 mm from anterior extremity, at 38–41% of body length; vagina directed posteriorly from vulva. Eggs in uterus spherical, thinwalled, smooth, 44–54 in diameter, with uncleaved content (Figure 1F). Tail 802–816 long. Comments This species was originally described by Baylis (1931) from the stomach and intestine of the carcharhinid shark Scoliodon sp. [probably Rhizoprionodon acutus (Ru¨ppel) according to Bruce & Cannon, 1990] off the eastern Australian coast (Cleveland Bay, Townsville, Queensland) and has not been recorded since. Gibson & Colin (1982) synonymised it with Terranova brevicapitata (Linton, 1901), a species inadequately described from Galeocerdo tigrinus (= G. cuvier) and later reported from Carcharias (= Carcharhinus) obscurus (Lesueur) from the North Atlantic Ocean (USA) (Mozgovoy, 1953). However, Deardorff (1987) re-established it, showing important differences in the descriptions of these two species. Bruce & Cannon (1990) also emphasised that T. scoliodontis should be considered a valid species until T. brevicapitata is redescribed in detail; they considered the absence of postcloacal ventral plectanes in the latter a main differentiating feature between these species. Bruce & Cannon (1990) redescribed T. scoliodontis on the basis of light microscopical examinations of paratype specimens. The morphology and measurements of specimens of the present material correspond, more or less, to the descriptions of the type-specimens of T. scoliodontis (see Baylis, 1931; Bruce & Cannon, 1990). However, they differ in a lower number of pairs of pre-anal papillae (22–24 vs 30–33) and a somewhat more complicated anterior margin of the lips; the presence of a very small median precloacal papilla and ventral pre-cloacal cuticular ornamentations were not previously reported in T. scoliodontis. Since these differences are negligible (numbers of pre-anal papillae may be highly variable in ascaridoid species and some morphological details can be properly seen only by SEM), the specimens from G. cuvier off New Caledonia
136 are considered to belong to T. scoliodontis. The present finding of this species represent new host and geographical records. Family Gnathostomatidae Railliet, 1895 Echinocephalus sinensis Ko, 1975 Host: Ray, Aetobatus cf. narinari (Euphrasen) (Myliobatidae: Rajiformes). ‘‘A. narinari ’’ is a species complex (Marie & Justine, 2005). Site: Spiral intestine. Locality: South Pacific Ocean, off Noume´a, New Caledonia (5 November 2003). Prevalence and intensity: three nematode specimens in 1 fish examined. Voucher specimens: Muse´um National d’Histoire Naturelle, Paris (JNC 956B) and Institute of Parasitology, ASCR, Cˇeske´ Budeˇjovice (N-848). Description (Figures 3, 4) Male (3 specimens). Medium-sized nematodes with fairly thick, finely transversely striated cuticle. Length of body 34.41–35.54 mm, maximum width 694–775. Anterior end provided with large lateral pseudolabia 95–122 long, each bearing pair of double papillae and amphid (Figures 3B, 4B,C). Medial part of pseudolabium elongated dorsoventrally, trilobed; each lobe bears 2 cuticular thickenings along external edges. Posterolateral margins of pseudolabia smooth. Non-serrate interlabia present between pseudolabia. Cephalic bulb prominent, 476–503 long, 612–666 wide, armed with 22–26 transverse rows of small claw-shaped spines 12 long (including their roots); some rows discontinuous; spines of neighbouring rows not touching each other, being distinctly separated by rings of unarmed cuticle 18–24 long (Figures 3A,B, 4A). Oesophagus 5.26–5.64 mm long (15–16% of body length), maximum width 367–449, not clearly divided into anterior muscular and posterior glandular portions (Figure 3A). Four cervical sacs present, ending posteriorly 2.80– 3.02 mm from anterior extremity. Nerve-ring and deirids 775–789 and 857–966, respectively, from anterior end of body. Posterior end of body curved ventrally. Spicules almost equal, 1.12–1.40 mm long (3.2–3.9% of body length) (Figure 3C). Weakly sclerotised V-shaped guber-
naculum c.100 long. Simple vesicular caudal alae c.1 mm long. Caudal papillae 7 pairs: 2 pairs of subventral pre-anals, 1 pair of lateral adanals and 4 pairs (2 subventral and 2 lateral) of postanals. Pair of small lateral phasmids present near end of tail (Figure 3C). Ventrolateral regions adjacent to cloaca with rugose areas consisting of irregularly shaped papillary and knob-like structures situated on transverse rows of ridges (Figures 3C, 4D). Tail conical, 925– 1,061 long. Comments The morphology of specimens of the present material is close to that of E. sinensis Ko, 1975 (see Ko, 1975; Deardorff & Ko, 1983). However, they are somewhat larger (body length 34.41 vs 16– 32 mm), they have fewer transverse rows of spines on the cephalic bulb (22–26 vs 26–29) and the third pair of caudal papillae is adanal instead of preanal (Deardorff & Ko, 1983); but these differences seem to be within the limit of intraspecific variability. Taking into account that they come from either the same or closely related species of the fish host, they are considered to belong to E. sinensis. Echinocephalus sinensis was originally described by Ko (1975) from the ray Aetabatus flagellum [= Aetobatus narinari (Euphrasen)] from the South China Sea (off Hong Kong), and Ko et al. (1980) studied the anatomy of the cephalic end in adults and larvae from rays and oysters, respectively; later this species was partly redescribed based on the same material by Deardorff & Ko (1983). The only other record of adults of this species (without a description) is that by Beveridge (1987) from A. narinari off the Australian coast (Moreton Bay); later Beveridge (1991) made an error in citing this finding as from the host Dasyatis fluviorum Ogilby, but another Echinocephalus species (E. overstreeti Deardorff & Ko, 1983) was reported from this host in his 1987 paper. The present finding represents the first record of E. sinensis from the New Caledonian waters and data on the morphology of specimens from the South Pacific Ocean are provided for the first time. Larvae of E. sinensis have previously been commonly found in oysters Crassostrea gigas (Thunberg) in Hong Kong (Ko, 1975). Juvenile forms of E. sinensis have also been reported from six species of teleosts off the West African
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Figure 3. Echinocephalus sinensis Ko, 1975, male. A, anterior part of body, lateral view; B, cephalic end, lateral view; C, caudal end, ventral view; D, spines on cephalic bulb. Scale-bars: A, 500 lm; B, 200 lm; C, 300lm; D, 30 lm.
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Figure 4. Echinocephalus sinensis Ko, 1975, SEM micrographs of male. A, anterior end, dorsoventral view; B, cephalic end, apical view; C, cephalic end, dorsoventral view; D, detail of area rugosa; E, rows of spines on cephalic bulb; F, deirid; G, caudal end of male, ventral view; H, region of cloacal opening with distinct caudal papillae and area rugosa, ventral view. Scale-bars: A-C,G,H, 100 lm; D-F, 10 lm.
139 coast (Obiekezie et al., 1992); however, this identification is uncertain, because there are so far no known morphological criteria which reliably distinguish Echinocephalus larvae (Beveridge, 1991).
Echinocephalus overstreeti Deardorff & Ko, 1983 Host: Blotched fantail ray, Taeniura meyeni Mu¨ller & Henle (Dasyatidae: Rajiformes). Site: Stomach. Locality: South Pacific Ocean, off Noume´a, New Caledonia (3 and 4 November 2003). Prevalence and intensity: In both of the T. meyeni examined; intensity 7 and 9 specimens (total of 6 males, 6 females and 4 larvae). Voucher specimens: Muse´um National d’Histoire Naturelle, Paris (JNC 954B and JNC 955A) and Institute of Parasitology, ASCR, Cˇeske´ Budeˇjovice (N-849). Description (Figures 5–7) General. Large nematodes with finely transversely striated cuticle. Cephalic end provided with 2 large pseudolabia, each bearing pair of double papillae and amphid (Figures 5C, 6E,F). Medial part of pseudolabium dorsoventrally elongated, trilobed; each lobe with 2 cuticular thickenings along external edges. Posterodorsal and posteroventral part of base of each pseudolabium with distinct cuticular serrations (Figures 5C, 6D,G). Small triangular, serrate interlabia (1 dorsal and 1 ventral) present between pseudolabia. Cephalic bulb prominent, armed with 23–35 transverse rows of small, elongate spines; some rows discontinuous; rows of spines close to each other but nonoverlapping (Figures 5A,B,D, 6A,B). Oesophagus long (12–15% of body length), widest near its posterior end, not clearly divided into anterior muscular and posterior glandular portions. Four cervical sacs present, extending posteriorly to about mid-length of oesophagus (Figure 5A). Deirids well developed, situated somewhat posterior to level of nerve-ring (Figure 6H). Tail conical. Male (6 specimens). Length of body 30.33– 42.49 mm, maximum width 625–925. Length of pseudolabia 177–258. Cephalic bulb 394–530 long, 544–843 wide. Transverse rows of spines 23–35 in
number; length of spines (including roots) in middle of bulb 9–15. Length of entire oesophagus 3.97–5.21 mm (12–13% of body length), maximum width 408–517. Nerve-ring and deirids 789– 1,006 and 952–1,156, respectively, from anterior extremity. Cervical sacs ending 2.24–3.45 mm from anterior end of body. Posterior end of body curved ventrally. Spicules almost equal, 1.71– 2.31 mm long (5.4–6.4% of body length). Gubernaculum indistinct. Simple vesicular caudal alae present; area rugosa composed of minute bosses extending in lateral regions approx. between 3rd–6th pairs of caudal papillae. Caudal papillae 8 pairs: 2 subventral pairs pre-anal, 1 subventral pair adanal and 5 pairs (1 lateral, 4 subventral) postanal. Pair of small lateral phasmids just posterior to last pair of caudal papillae (Figures 5F–H, 7F). Tail 354–544 long. Female (4 non-gravid specimens). Length of body 25.77–37.81 mm, maximum width 571–911. Length of pseudolabia 163–177. Cephalic bulb 408–435 long, 585–680 wide. Transverse rows of spines 30–35 in number; length of spines (including roots) in middle of bulb 9–15. Length of entire oesophagus 3.79–4.91 mm (13–15% of body length), maximum width 408–585. Nerve-ring and deirids 748–870 and 979–1,074, respectively, from anterior extremity. Cervical sacs ending 2.42–2.49 from anterior end of body. Vulva in posterior part of body, 24.54–36.38 mm from anterior extremity (at 95–96% of body length), 408–462 anterior to anus; vagina directed anteriorly from vulva (Figure 5E). No eggs in uteri. Tail 843–966 long. Fourth-stage larva (4 specimens). Body 14.59– 26.90 mm long, maximum width 408–789. Very narrow, hardly visible lateral alae starting some distance posterior to deirids and extending posteriorly to about level of anus. Pseudolabia simple, 40–42 long; each with 2 well-developed papillae and amphid. Small rounded interlabia present (Figure 7A). Cephalic bulb 272–422 long, 340–422 wide, armed with 6 transverse rows of claw-shaped spines 24–57 long (including their roots); size of spines gradually increasing from first to sixth row (Figure 7A,B). In addition, 2 groups of minute spines, 1 dorsal and 1 ventral, present between interlabia and first anterior ring of larger spines on cephalic bulb; each group consisting of spines arranged in 3 rows of 2, 2 and 6 spines; 2 larger
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Figure 5. Echinocephalus overstreeti Deardorff & Ko, 1983. A, anterior end of male, lateral view; B, cephalic end of male, lateral view; C, pseudolabium, lateral view; D, anterior end of male, dorsoventral view; E, posterior end of female, lateral view; F,G, caudal end of male, ventral and lateral views; H, posterior end of male, lateral view; I, tail tip of female. Scale-bars: A, 500 lm; B,F,G, 200 lm; C,I, 100 lm; D,E,H, 300 lm.
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Figure 6. Echinocephalus overstreeti Deardorff & Ko, 1983, SEM micrographs of male. A, anterior end, dorsoventral view; B, anterior end, apical view (focused on spines of cephalic bulb); C, detail of spines on middle region of cephalic bulb; D, serration on posterior edge of pseudolabium; E, cephalic end with distinct pseudolabia and interlabium; sublateral view; F, interlabia, apical view; G, detail of serrations on outer lobes of pseudolabia and on interlabium, dorsoventral view; H, deirid; I, detail of anteriormost rows of spines on cephalic bulb. Scale-bars: A,B,E,F, 100 lm; D,G,H, 10 lm. Abbreviations: a, amphid; p, cephalic papilla.
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Figure 7. Echinocephalus overstreeti Deardorff & Ko, 1983, SEM micrographs of larva and male from Taeniura meyeni. A-E, larva (A,B, anterior end, dorsoventral and apical views; C, detail of group of three anterior ventral rows of reduced spines (arrows) on cephalic bulb, ventral view; D, oral aperture demarcated by pseudolabia, apical view; E, caudal end with distinct lateral alae); F, caudal end of male, ventral view. Scale-bars: A,B,E,F, 100 lm; C,D, 10 lm.
143 spine-like formations present laterally to third row of 6 spines (Figure 7C). Oesophagus 3.26– 3.29 mm long. Four cervical sacs present. Nervering 476–625 from anterior extremity. Deirids just posterior to level of nerve-ring. Tail conical, pointed, 204–408 long (Figure 7E). Comments The morphology of specimens of the present material is mainly in accordance with the descriptions of E. overstreeti Deardorff & Ko, 1983. In the original description, Deardorff & Ko (1983) reported a somewhat smaller body length in both males (21–30 vs 30–42 mm) and females (15–30 vs up to 38 mm), shorter spicules (0.6–1.4 vs 1.7– 2.3 mm) and a somewhat different number and different arrangement of male caudal papillae (seven pairs: three pre-anal, one adanal and three postanal). However, according to Beveridge (1987), who redescribed the species from Australian specimens, the males and females were 55–60 and 58–63 mm long, respectively, the spicules measured 1.7–1.9 mm and there were three pairs of pre-anal and four pairs of postanal papillae in the male. The first, lateral pair of postanals was probably overlooked by these authors. Whereas the cephalic bulb of specimens of the present material was armed with 23–35 transverse rows of spines, Deardorff & Ko (1983) and Beveridge (1987) reported 30–43 and 29–40 rows, respectively; however, the character of spines in our specimens (Figure 4C) appears to be identical with that illustrated by Deardorff & Ko (1983). Taking into account that E. overstreeti was described from the same host species in the South Pacific, the New Caledonian specimens from T. meyeni are considered to belong to this species. Echinocephalus overstreeti was originally described from the ray Taeniura melanospilos Bleeker (= syn. of T. meyeni) from off the Marquesas Islands by Deardorff & Ko (1983). Later adult specimens of this species were reported also from two species of rays, Dasyatis sephen (Forska˚l) (Dasyatidae) and Myliobatis australis Macleay (Myliobatidae), and the shark Heterodontus portusjacksoni (Meyer) (Heterodontidae) from Australian coastal waters (Beveridge, 1987, 1991); gravid females were found only in the last named host. E. overstreeti was also reported (but not described) from the ray Urogymnus asperrimus (Bloch &
Schneider) from Eniwetok (also spelled Enewetak) Atoll in the Marshall Islands of the eastern Pacific (Brooks & Deardorff, 1988). The present finding represents the first record of E. overstreeti from coastal waters of New Caledonia. According to Beveridge (1987), E. overstreeti differs from E. uncinatus Molin, 1858, a species originally described from European elasmobranchs and redescribed in detail by Beveridge (1985), mainly in the form and structure of the rugose area (however, this has not been studied by SEM in E. uncinatus). Differences between these two species should also include the number and arrangement of caudal papillae, according to Hoberg et al. (1998), but the number of pairs in E. overstreeti was found in this paper to be identical (eight), although their arrangement was different to that reported by Beveridge (1985) for E. uncinatus. In addition to adults of E. overstreeti in elasmobranchs from Australian coastal waters (see above), Beveridge (1987) reported fourth-stage larvae of this species from an additional 10 elasmobranch species (rays and sharks) belonging to different families: Aptychotrema vincentiana (Haacke), Callorhynchus milii Bory de Saint-Vincent, Dasyatis brevicaudatus (Hutton), D. thetidis Ogilby, Hypnos monopterygium (Shaw), Orectolobus maculatus (Bonnaterre), Parascyllum ferrugineum McCulloch, Raja whitleyi Iredale, Trygonorhina guanerius Whitley and Urolophus mucosus, and from the scallops (Mollusca) Pecten albus Tate and Chlamys bifrons (Lamarck). Although the conspecificity of Echinocephalus larvae from scallops and adults from Heterodontus portusjacksoni (Meyer) was supported by allozyme electrophoresis (Andrews et al., 1988), this can be questioned on the basis of the morphology of larvae found in the type-host off New Caledonia. Whereas Beveridge (1987) described two groups (one dorsal and one ventral) of minute spines (each consisting of two short rows of two and three spines) anterior to six major rows in Echinocephalus larvae from scallops, each such group in larvae from T. meyeni is formed by three rows of two, two and six spines, and two additional altered spine-like formations are situated laterally to the third row (Figure 7,C). Recently, the senior author examined by SEM a similar Echinocephalus larva from a Mexican teleost and found these groups of spines to be very similar to those in the present material, but the third
144 row was formed only by three spines instead of six. In our opinion, these groups of spines may differ in larvae of different species of Echinocephalus and thus can provide a rather reliable taxonomic criterion for their identification. However, it is necessary to stress that these spines have to be studied using SEM, because some of them may be hardly visible under the light microscope. To date, only the larvae of E. pseudouncinatus Millemann, 1951, E. sinensis and those considered to be E. overstreeti have been described in some detail (Millemann, 1951; Ko, 1975; Beveridge, 1987). Of these, however, only the last named was studied by SEM, so existing data on the structure of their dorsal and ventral groups of spines may be unreliable. In our opinion, the larvae reported by Beveridge (1987) and Andrews et al. (1988) as E. overstreeti from various elasmobranchs and molluscs belonged to another Echinocephalus species.
Negative results for other elasmobranchs Whittington (1998) commented on the necessity, previously unrecognised in the parasitological literature, of publishing negative results, and we share this opinion, especially if hosts are from locations in which parasitological data are scarce or absent. The following large sharks were examined off New Caledonia and did not have nematodes in either the stomach or intestine: Carcharhinus amblyrhynchos (Bleeker), Negaprion acutidens (Ru¨ppell) and Nebrius ferrugineus (Lesson).
Acknowledgements Amandine Marie is thanked for her enthusiasm and skill in organising the team needed for the capture of a large tiger shark. Other students involved in fishing operations and the collection of parasites were Eric Bureau, Maya Robert, Chloe´ Journo, Nathaniel Cornuet, Isabelle Jollit, Sylvain Richer de Forges and Violette Justine; Marc Negrello, on board the R/V ‘Enzo’; and Nicole Fabre, Laurent Pascal and Augustin ‘Jean-Pierre’ Agourere are thanked for their help in shark fishing. Prof. Claude Chauvet (UNC, Universite´ de Nouvelle-Cale´donie, Noume´a, New Caledo-
nia) and Jean-Louis Pagnon are gratefully thanked for collecting fish on board the R/V ‘Alcyon’. Soazig Le Mouellic (UNC) and Angelo di Matteo (IRD) provided technical help. Prof. Louis Euzet (Se`te, France) provided help and advice during the parasite collection and preparation. Peter Last (CSIRO, Australia) gave advice on the identification of the spotted eagle ray. Thanks are also due to the staff of the Laboratory of Electron Microscopy of the Institute of Parasitology, ASCR, at Cˇeske´ Budeˇjovice for their technical assistance and Irena Husa´kova´ from the Department of Helminthology of the same Institute for her help with the preparation of the illustrations. The authors are very grateful to Dr David Gibson, Natural History Museum, London for revising the English and his help with the literature. This study was partly supported by grant no. 524/06/0170 from the Grant Agency of the Czech Republic and by the research project (Z60220518) of the Institute of Parasitology, Academy of Sciences of the Czech Republic.
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