59 Systematic Parasitology 37: 59–66, 1997. c 1997 Kluwer Academic Publishers. Printed in the Netherlands. Echinorhynchus trachyrinci n. sp. (Acanthocephala: Echinorhynchidae) from macrourid fishes of the northeast Atlantic Matthew T. Wayland1 2, David I. Gibson1 and Christina Sommerville2 ; 1 2 Department of Zoology, The Natural History Museum, Cromwell Road, London, SW7 5BD, UK Institute of Aquaculture, University of Stirling, Stirling, FK9 4LA, UK Accepted for publication 1st November, 1996 Abstract Echinorhynchus trachyrinci n. sp. (Palaeacanthocephala: Echinorhynchidae) is described from Trachyrincus scabrus (Rafinesque) (Macrouridae: Trachyrincinae) (type-host) and T. murrayi Günther from the northeast Atlantic. The most important diagnostic features of this species are: the number of longitudinal rows of hooks 17–22; the number of hooks per row 17–22+; the maximum length of hook blade 38–52m; the proboscis width 139–224m; and the proboscis length to width ratio 3.9–6.4:1. E. trachyrinci n. sp. is differentiated from E. gadi, E. malacocephali, E. longiproboscis, E. petrotschenkoi, E. melanoglaeae, E. theragrae and E. sebastolobi. Metechinorhynchus malacocephali Parukhin, 1985 is transferred to Echinorhynchus as E. malacocephali n. comb Introduction The Macrouridae (Gadiformes) is a diverse family of about 300 species of deep-sea fishes (Cohen, Inada, Iwamoto & Scialabba, 1990). Most are benthopelagic, living over the continental slopes at depths of 2002,000 metres (Marshall, 1965). Acanthocephalans from macrourid fishes are most frequently determined as Echinorhynchus gadi Zoega in Müller, 1776 (= E. acus Rudolphi, 1802) (see Linton, 1901; Kabata, 1961; Mamaev, 1965; Radulescu, 1969; Noble, 1973; Redkuzubova, 1976; Szuks, 1980; Zubchenko, 1981a; Vassiliiadès, 1985; Kovalenko, 1986a). This taxon is now recognised to be a group of morphologically cryptic species (Väinölä, Valtonen & Gibson, 1994). Others are recorded as Echinorhynchus sp. (=Metechinorhynchus sp.) (Armstrong, 1974; Campbell, Haedrich & Munroe, 1980; Zubchenko, 1981b; Reimer, 1984; Houston & Haedrich, 1986; Kovalenko, 1986a). Relatively recently, two new species of Echinorhynchus, E. malacocephali (Parukhin, 1985) n. comb. and E. longiproboscis Rodjuk, 1986, have been described from macrourids of the Indian Ocean and South Atlantic. It seems likely that some of the records cited above may also represent these or other new taxa. During parasitological surveys of deep-sea fish of the northeast Atlantic, Dr R.A. Bray, of The Natural History Museum, London, collected specimens of an undescribed species of acanthocephalan from the intestine of Trachyrincus scabrus (Rafinesque) (=Lepidoleprus trachyrincus Risso; Trachyrhynchus trachyrhynchus Günther) and T. murrayi Günther. We describe this material below as a new species of the genus Echinorhynchus Zoega in Müller, 1776 (sensu Yamaguti, 1963; Amin 1985). T. scabrus (the roughsnout grenadier) and T. murrayi (Murray’s longsnout grenadier) are closely related, benthopelagic species, living at 400–1,500 metres and 530–1,630 metres respectively (Geistdoerfer, 1986). T. scabrus has a diet consisting of fishes, shrimps, mysids and copepods, and can attain a total length of over 50 cm (Geistdoerfer, 1986). T. murrayi feeds predominantly on copepods and amphipods (Mauchline & Gordon, 1984), and reaches a total length of at least 40 cm (Geistdoerfer, 1986). Materials and methods Important taxonomic characters of acanthocephalans display considerable morphological variation with age, sex, host species and geographical location (Amin, 60 1975; Amin & Redlin, 1980; Shostak, Dick, Szalai & Bernier, 1986). Following the recommendations of Amin (1975), the material used in this description was taken from more than one host species and from more than one locality, and includes both immature and mature worms. All of the material used in this study was fixed and stored in 80% alcohol. Material from fresh specimens of T. scabrus was collected at three localities: 58 210 N, 09 410 W–58 240 N, 09 390 W, depth 1,300– 1,320 metres; 56 400 N, 09 160 W–56 380 N, 09 160 W, depth 1,050–1,120 metres; 57 470 N, 09 490 W– 57 490 N, 09 500 W, depth 1,300–1,310 metres. British Museum (Natural History) registration numbers are 1988.2646–2650, 1988.2651–2662 and 1988.2632– 2636, respectively. In addition, three specimens of Trachyrincus murrayi were collected from a single locality: 50 320 N, 14 100 W; depth 1,600 metres. The digestive systems of these fish were frozen on capture and later defrosted and examined for parasites. A total of 54 worms were examined; 33 from T. scabrus (13 males, 20 females) and 21 from T. murrayi (10 males, 11 females). Acanthocephalans were cleared and mounted in creosote for light microscopy. Light microscope observations were used in the description of all characters except the number of hooks per row, since hook counts were found to be more reliable when made from threedimensional proboscis images produced by scanning electron microscopy (SEM) (see also Brown, Chubb & Veltkamp, 1986). Sixteen alcohol-fixed specimens were prepared for SEM examination. They were passed through an acetone series, critical point dried in carbon dioxide using a Balzers CPD 030, sputter coated in platinum using a Polaron E5100, and viewed in a Hitachi S2500 SEM at an accelerating voltage of 15 KV. Of the 54 specimens examined, only one male had a fully everted proboscis. In all other specimens the proboscis was partially or completely inverted. The sum of the lengths of the everted and inverted portions of each proboscis has been used as an estimate of the length of the fully everted proboscis. Full counts of the number of hooks per longitudinal row were possible for the slightly inverted proboscides of two males and one female. Measurements are in micrometres unless otherwise stated, with the mean and standard deviation in parentheses. Echinorhynchus trachyrinci n. sp. (Figures 1– 4) Type-host: Trachyrincus scabrus (Rafinesque). Type-locality: 58 20.90N, 09 41.10W–58 24.30 N, 09 39.30 W; depth 1,300–1,320 metres. Site: Intestine Other host: Trachyrincus murrayi Günther. Other localities: 56 400 N, 09 160 W–56380 N,  0 09 16 W, depth 1,050–1,120 metres; 57 470 N, 09 490 W–57490 N, 09 500 W, depth 1,300–1,310 metres; 50 320 N, 14 100 W, depth 1,600 metres. Type-material: Holotype BM(NH) 1988.2646; paratypes BM(NH) 1988.2647–2650. Description Trunk elongate, cylindrical, unarmed. Mature females larger than males. Maximum width at level of posterior tip of proboscis receptacle in females; position of maximum width variable in males. Proboscis cylindrical. Neck trapezoid, short. Hook blades longer than roots. Largest longest-bladed hooks found on anterior proboscis; posterior hooks shorter and stouter with the exception of basal 1–3 in each row. Basal hooks finer, less curved and with reduced root. Proboscis receptacle double-walled, with nerve ganglion situated at mid-length. Lemnisci normally shorter than proboscis receptacle, sometimes less than half length. Male Trunk length, excluding everted proboscis and bursa, 3.6–9.4 mm (6.6  1.59 mm). Maximum trunk width 430–910 (640  120). Proboscis width 139– 195 (168  16). Proboscis fully everted in only one male; length 679; length to width ratio 4.9 : 1. Estimated range of proboscis lengths 670–1,090 (875  150). Estimated range of proboscis length to width ratios 4– 6.4 : 1 (5.0  0.76 : 1). Number of rows of hooks 18– 22. Maximum number of hooks per row 17-22+ (full hook count not possible because proboscis tip inverted). Maximum length of hook blade 38–45 (40  3). Neck length 89–248 (150  41). Proboscis receptacle 1,034–1,914  173–349 (1,365  233  236  48). Lemnisci 445–1,240  108–356 (691  198  226  60). Reproductive system 54–73% length of body (66  0.05%). Testes elongate-oval, arranged in tandem, situated in median part of trunk. Testes may be separated by distance of up to 350, or overlap by up to 159. Anterior testis 413–1,123  210–476 (736  178  287  61). Posterior testis 362–811  203–413 61 (623  121  284  58). Typically 6 cement glands present (87% of specimens), but number ranges from 4–7; moniliform arrangement is most common (69.6% of specimens), but 17.4% of specimens have one pair of parallel glands and in 13.0% of specimens glands are clustered. Saefftigen’s pouch 629–1,304  95–222 (888  190  140  30). Penis conical, 47–76 (57  8) wide at base. Copulatory bursa opens subterminally, with maximum dimensions 1,280  755. Female Trunk length, excluding proboscis, 5.1–14.0mm (10.09  2.3mm). Maximum body width 572–1,018 (781  125). Proboscis width 148–224 (179  18). Estimated proboscis length 670–1,190 (950  145). Estimated proboscis length to width ratio 3.9–6.25:1 (5.1  0.68:1). Number of rows of hooks 17–22. Maximum number of hooks per row 19–20+ (full hook count not possible because proboscis tip inverted). Maximum length of hook blade 41–52 (47  6). Neck length 76– 186 (127  36). Proboscis receptacle 1,145–2,028  186–318 (1,522  228  242  30). Lemnisci 343– 1,081  151–400 (699  167  270  66). Length of genital complex 887–2,413 (1,482  371). Body width at midpoint of uterus of gravid worms 292–604 (423  81). Vagina 60–120 (89  16) in width, provided with single sphincter; sphincter width 64–113 (81  13) and sphincter width to vagina width ratio 0.71–1.21:1 (0.93  0.15:1). Gonopore slightly subterminal. Eggs fusiform, with polar elongations of median envelope; dimensions of 130 eggs isolated from 5 females and measured when immersed in creosote 80–110  16–24 (91  7  20  2); dimensions of acanthors within eggs 45–57  10–16 (50  3  12  1). Remarks There is some evidence of sexual dimorphism in the morphometrics of this species, but this is probably related to the larger body size of female worms. The tegument of the trunk was folded in every specimen examined. This suggests that the specimens were not extended to their full length, by relaxation in water, prior to fixation. The trunk lengths of fully relaxed specimens are likely to be considerably larger on average, than those recorded in this study. The shape of many proboscis hooks was distorted in both light microscope and SEM preparations. Affected hooks appeared to have lost turgor and were often bent or folded. It was impossible to determine if this apparent distortion was an artifact of preparation, because living material was not available for comparison. In numerous specimens the hooks were partly or completely retracted into the proboscis. Preparation for SEM resulted in considerable shrinkage of proboscides. Proboscis widths measured from SEM micrographs were on average 23% (range 8–32%) smaller than light microscope observations. Ecological data All three specimens of Trachyrincus murrayi examined for parasites were found to be infected with E. trachyrinci n. sp. at a mean intensity of 39 worms per fish. The prevalence and intensity of infections in T. scabrus are not known. Discussion The previous echinorhynchid records from Trachyrincus scabrus are: Acanthocephalus lucii (Müller, 1776) Lühe, 1911 (as Echinorhynchus angustatus Rudolphi, 1809) from an unspecified locality (Porta, 1905); and E. gadi from off the coast of Senegal (Vassiliiadès, 1985). The validity of the first record is extremely dubious as A. lucii is typically a parasite of freshwater fishes (Petrochenko, 1956). Acanthocephalans have not previously been recorded from T. murrayi. Echinorhynchus trachyrinci n. sp. differs from E. gadi, the most common species of the genus in NE Atlantic fishes, in the number of proboscis hooks per longitudinal row, hook blade length and the proboscis length to width ratio. According to Shostak et al. (1986) E. gadi has a maximum of 10–15 hooks per longitudinal row (vs 17–22+), a maximum hook blade length of 50–79m for males (vs 38–45m) and 53–86m for females (vs 41–52m) , and a proboscis length to width ratio of 2.26–3.54:1 (vs 3.9–6.4:1). E. trachyrinci and E. gadi have overlapping ranges for number of longitudinal rows of hooks, proboscis length, proboscis width and egg length. E. trachyrinci is the third species of Echinorhynchus to be described from the Macrouridae; E. malacocephali (Parukhin, 1985) n. comb. is a parasite of Malacocephalus laevis (Lowe) of the Indian Ocean and South Atlantic, and E. longiproboscis Rodjuk, 1986 occurs in Dissostichus eleginoides Smitt (Nototheniidae) and Macrourus holotrachys Günther (Macrouridae) of the Falkland-Patagonian Shelf and South Georgia regions. E. malacocephali was orig- 62 Figure 1. Echinorhynchus trachyrinci n. sp. A. Holotype male, lateral aspect. B. Female, lateral aspect. C. Longitudinal hook row from a male; most anterior hook was retracted with proboscis tip and so has been omitted. Scale-bars: A, B, 1 mm; C, 50 m. 63 Figure 2. Echinorhynchus trachyrinci n. sp. A. Three different arrangements of cement glands. B. Posterior extremity of female. C. Eggs. Scale- bars: A, 1 mm; B, 200 m; C, 50 m. 64 Figure 4. Apical view of proboscis of Echinorhynchus trachyrinci n. sp. Scale-bar: 50 m. Figure 3. Lateral view of proboscis of Echinorhynchus trachyrinci n. sp. Scale-bar: 150 m. inally assigned to the genus Metechinorhynchus Petrochenko, 1956 by Parukhin (1985), but it is here transferred to Echinorhynchus (sensu Yamaguti, 1963; Amin, 1985) because the former taxon is poorly defined (see Huffman & Kliever, 1977; Amin & Redlin, 1980; Shostak et al., 1986) and incongruent with allozyme data (Väinölä et al., 1994). E. trachyrinci differs markedly from E. malacocephali in proboscis size and armature; the latter species has proboscis of dimensions 310–450  110–140m (vs 670–1,190  139–224m) and is armed with only 14 rows of 10 hooks (Parukhin, 1985). The new species displays some similarities to E. longiproboscis, with overlapping ranges for the proboscis dimensions and the number of longitudinal rows of hooks, and the males of both species usually have a moniliform cement gland arrangement. Discriminating characters are the number of hooks per longitudinal row and the maximum hook blade length; E. longiproboscis has 15–16 hooks per row (vs 17–22+) and the blade length of the largest hook is 67m (vs 38–52m) (see Rodjuk, 1986). As far as we are aware, the only other Echinorhynchus species to have been recorded from a macrourid is E. petrotschenkoi (Rodjuk, 1984) Zdzitowiecki, 1989. Specimens of this species were recently collected from Macrourus whitsoni (Regan) caught in the Weddell Sea at a depth of 630–1540 metres (Dr K. Zdzitowiecki, personal communication). E. trachyrinci can be readily differentiated from E. petrotschenkoi, because it has more hooks per longitudinal row (17–22+ vs 9–15) and a smaller maximum hook blade length (38–52m vs 59–87m) (see Zdzitowiecki, 1989). The species closest to E. trachyrinci is probably E. melanoglaeae Dollfus, 1960. The only description of the latter species was based on a single adult male collected from Guentherus altivela Osorio (as Melanoglaea ventralis Barnard) (Ateleopodiformes: 65 Ateleopodidae) caught off Senegal at a depth of 500– 600 metres (Dollfus, 1960). Nearly all of the morphometrics which Dollfus recorded for this specimen (i.e. number of longitudinal rows of hooks, number of hooks per row, body dimensions, proboscis length, maximum width of proboscis, proboscis receptacle dimensions and testes dimensions) fall into the range of variation displayed by E. trachyrinci. Nevertheless, the proboscis of E. melanoglaeae tapers considerably such that its basal width is twice that at the apex, whereas the proboscis of E. trachyrinci varies little in width along its length. E. melanoglaeae also has a slightly smaller maximum blade length of 36m (vs 38–52m) and a smaller proboscis length to width ratio of 3.6:1 (vs 3.9–6.4:1). In view of these differences and the considerable differences in host and locality, we have little hesitation in considering these two taxa distinct. Two other species are morphologically somewhat similar to E. trachyrinci: E. theragrae Dydenko, 1992, a parasite of Theragra chalcogramma (Pallas) (Gadiformes: Gadidae) from Peter the Great Bay, Sea of Japan; and E. sebastolobi Kovalenko, 1986, a parasite of Sebastolobus alascanus Bean (Scorpaeniformes: Scorpaenidae) from the Okhotsk Sea. E. theragrae has the same hooks formula as E. trachyrinci, but can be distinguished by its wider proboscis (240–260m vs 139–224m ) and greater maximum hook blade length (59–70m vs 38–52m) (see Dydenko, 1992). E. sebastolobi differs from E. trachyrinci in having fewer longitudinal rows of hooks (16 vs 17–22+) and a greater maximum hook blade length (68–79m) (see Kovalenko, 1986b). E. trachyrinci has been reported here from off the coasts of western Scotland, north west Ireland and south west England. However, if this parasite’s range is correlated with that of its definitive hosts, it may extend south to the Cape Verde Islands and west to the coasts of the Americas off Labrador (see Cohen et al., 1990). Acknowledgements We would like to thank Dr R.A. Bray for collecting the material. We also gratefully acknowledge assistance from the staff of the Electron Microscope Unit and Mrs E.A. Harris of The Natural History Museum, London. This study was supported by a NERC CASE studentship. References Amin, O.A. (1975) Variability in Acanthocephalus parksidei Amin, 1974 (Acanthocephala: Echinorhynchidae). Journal of Parasitology, 61, 307–317. Amin, O.A. (1985) Classification. In: Crompton, D.W.T. & Nickol, B.B. (Eds) Biology of the Acanthocephala. Cambridge: Cambridge University Press, pp. 27–72. Amin, O.A. & Redlin, M.J. 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