CSIRO PUBLISHING. Australian Journal of Zoology, 2007, 55,

CSIRO PUBLISHING www.publish.csiro.au/journals/ajz Australian Journal of Zoology, 2007, 55, 161 168 Nematodes from the water dragon, Physignathus lesueurii (Reptilia:Agamidae) in Australia, with a description of Spinicauda fluviatica, sp. nov. (Nematoda:Heterakoidea) Hugh I. Jones Discipline of Microbiology and Immunology, M502, University of Western Australia, Nedlands, WA 6009, Australia. Email: hjones@cyllene.uwa.edu.au Abstract. Abbreviata physignathi and Spinicauda fluviatica, sp. nov., were the predominant species of nematode recovered from the gastrointestinal tracts of 65 Physignathus lesueurii examined from eastern Australia. S. fluviatica, sp. nov., is distinguished from other known species by the large well sclerotised excretory sinuses in both sexes and by the relative lengths of the spicules and gubernaculum in males. This is the first species of Spinicauda to be described from an agamid lizard. Both these nematode species occur mainly or entirely in New South Wales within 100 km of the coast; P. lesueurii is the only known host of both species. The persistence of generalised apical dentition in A. physignathi and its high host-specificity suggests a long association with this lizard, which diverged early from the main agamid stock. The significant association of these two unrelated nematode species is attributed to the high density of P. lesueurii hosts along suitable rivers. Other nematode species identified in low numbers in one or two hosts only were Abbreviata antarctica, A. confusa, Maxvachonia brygooi and immature Dracunculus sp. in the gastrointestinal tract, encysted subserosal physalopterid larvae on two stomachs, and Oswaldofilaria samfordensis in the body cavity. Introduction The water dragon Physignathus lesueurii (Gray, 1831) (Agamidae) occurs in eastern Australia from eastern Victoria to Cape York. Its presence in New Guinea is not yet confirmed (Watkins-Colwell and Johnston 1999). It is semiaquatic and arboreal, frequently lying in branches over rivers and creeks and dropping into the water if disturbed (Cogger 1992). Feeding under water has not been confirmed (Greer 1989). Population density is high in suitable rivers in New South Wales, with 137 215 adults per km of river (Thompson 1993). It is the largest agamid lizard in Australia with the lowest mean body temperature yet measured (Wilson 1974); it diverged from the main agamid stock in Australia at an early stage (Honda et al. 2000), with fossil remains in north-west Queensland dating back to the Miocene (15 million years ago: Covacevich et al. 1990). Its parasite fauna has received little study. Mackerras (1962) described Oswaldofilaria innisfailensis from the subperitoneal tissues of this host, and Manzanell (1982) also identified O. samfordensis and O. pflugfelderi, as well as O. innisfailensis, from the connective tissues and body cavity of P. lesueurii in southern Queensland. Baylis (1924) described Abbreviata (=Physaloptera) physignathi from the unusual situation of the eye-socket of a specimen that had died in captivity in New Zealand, and this species has since been identified on several occasions from the stomach of this host (H. Jones, unpub. data). However, there have been no systematic studies of the gastrointestinal nematodes of this lizard. Several species or genera of nematodes are known to occur predominantly or exclusively in Australian agamid lizards (e.g. Skrjabinoptera goldmani Mawson, 1970 (Mawson 1970; Jones 1986, 1994), Maxvachonia brygooi Mawson, 1972 (Mawson 1972; Jones 1986, 1994) and Oswaldofilaria spp. (Manzanell 1982)). In view of the unique ecological and phylogenetic characteristics of P. lesueurii, this study was undertaken to determine its parasite fauna and attempt to place this in the context of the known nematode parasites in this reptile family. Materials and methods Sixty-five P. lesueurii preserved in museum collections were dissected and examined for gastrointestinal nematodes. Twentyfour were from Museum Victoria, three from the Queensland Museum, four from the South Australian Museum, 33 from the Australian Museum and one from CSIRO in Canberra (dissected by D. M. Spratt); 43 lizards had been collected in New South Wales, 16 in Victoria and six in Queensland. Male P. lesueuri are larger than females but otherwise cannot be distinguished by external appearance; sexing of hosts from internal organs was not undertaken. Worms recovered were cleaned, cleared in chlorolactophenol or glycerine and examined using an Olympus BH series microscope. Drawings were made by means of a drawing tube. All specimens were returned to their respective museums or to the Australian Helminth Collection. Results Seven species of nematode were collected (Table 1). Abbreviata physignathi, A. confusa, A. antarctica (Spirurida: Physalopteridae), Dracunculus sp. (Spirurata: Dracunculidae), Spinicauda fluviatica, sp. nov., (Heterakoidea: Spinicaudidae), Maxvachonia brygooi (Ascaridida: Cosmocercidae) were recovered from the gastrointestinal tract and Oswaldofilaria samfordensis (Spirurida: Filariidae) in the body cavity. CSIRO 2007 10.1071/ZO06079 0004-959X/07/030161

162 Australian Journal of Zoology H. I. Jones Table 1. Nematode species recovered from 65 Physignathus lesueurii individuals Species No. Percentage Intensity infected infection (mean, range and s.d.) Abbreviata physignathi 31 48% 28, 1 208, 42.4 A. antarctica 1 1.5% 2 A. confusa 1 1.5% 1 Maxvachonia brygooi 2 3.1% 3,4 Dracunculus sp. 1 1.5% 1 Spinicauda fluviatica, sp. nov. 28 43.7% 16, 1 191, 37.4 Oswaldofilaria samfordensis 1 1.5% 2 Encysted physalopterid larvae 2 3.1% 1, 3 Nematodes collected from two lizards that died in Taronga Zoo were identified as A. physignathi. In addition, two stomachs contained one and three encysted physalopterid larvae subserosally on the stomach wall. S. fluviatica is considered to be a new species and is described below. Systematics and morphology Spinicauda fluviatica, sp. nov. Heterakoidea (Raillet & Henry 1912) Chabaud 1957 Heterakidae Raillet & Henry, 1912 Spinicaudinae Travassos, 1920 Material examined Holotype. Adult male, W.31684, recovered from stomach of Physignathus lesueurii. Australian Museum R153013, collected Tintenbar, 300 m north of Kirkland s Crossing, Friday Hut Road, New South Wales (28 47 S, 153 31 E), 15.i.1997. Allotype. Adult female, W.31685, same data as for holotype. Paratypes. 57, male and female, W.31686, same data as for holotype. Additional specimens. Specimens recovered from another 25 Physignathus lesueurii from New South Wales and two from Victoria have been assigned to this species (AM W.31716 W.31734; AHC 34255 34258; NMV F125561 F125564). Diagnosis With characters of the genus. Excretory sinuses at level of posterior oesophageal bulb large and well sclerotised; excretory pore circular, large. Copulatory spicules ~1/5 to 1/7 total length of worm, gubernaculum 1/4 length of spicules. Eggs finely pitted. Description (Table 2, Figs 1 8) Small spindle-shaped worms, males slightly smaller than females, disposed in bow-shaped curve, males with tail curved ventrally in approximate semicircle. Tail tapers to a fine point. Cuticle with small sessile papillae, more conspicuous in males than in females, in up to six rows along body, inconsistently spaced. Narrow lateral alae extend from near anterior end to tail in both sexes. Head retractable. Three thick lips. Dorsal lip bears two low wide papillae on external surface, doubled nature not readily discerned. Similar sessile papilla on external surface of each subventral lip, with single small inconspicuous papilla close to amphid. Amphids in small pit on subventral lips. Each lip bears single anteriorly directed cuticular Table 2. Measurements (mm) of Spinicauda fluviatica, sp. nov. Measurements Male holotype Male paratypes Female allotype Female paratypes (10 2 n) (n = 9) (10 2 n) (10 2 n) (n = 11) (10 2 n) Length 700 520 720 710 460 790 Maximum width 40 24 40 60 40 72 Pharynx length 6 5.6 9.2 68 56 72 Pharynx width 1.6 1.6 3.6 3.6 2.8 3.6 Oesophagus length 96 86 120 100 92 11.36 Oesophagus width 4.8 5.6 6.4 6.4 4.8 7.2 Oesophagus bulb width 17 15 19 18.4 17.6 24 Nerve ring A 62 38.62 68 58 77 Excretory pore A 88 80 112 100 72 108 Excretory sinus length 10 8 12 10.4 10 15.2 Excretory pore width 2 2 3 3.2 1.6 3.2 Sucker width (internal) 10 0.08 0.11 Sucker depth (anterior) 3.6 2.0 3.2 Sucker depth (posterior) 5.2 3.6 6.0 Tail length 46.4 30 44 80 58 96 Spicule length 96 68 104 Spicule, % body length 13.7 13.1 15.7 Gubernaculum length 20 20 24 Gubernaculum:spicule 0.21 0.20 0.29 Vulva (% from anterior end) 46.75 37.5 50.0 Egg length 8.4 8.0 9.2 Egg width 4.8 4.4 6.0 A Distance from anterior end.

Nematodes from Physignathus lesueurii Australian Journal of Zoology 163 extension on medial surface, usually extending as far as or slightly beyond anterior tip of lip. Short pharynx leads via valve into long narrow oesophagus. Large flask-shaped bulb containing a valvular mechanism at posterior end of oesophagus. Nerve ring difficult to visualise, at about mid-length of oesophagus. Excretory pore circular in outline, large and conspicuous. Two large and conspicuous sinuses, bell-shaped, with thick walls with rugose external medial surface, at level of or immediately anterior to level of oesophageal bulb, lead anteriorly to this pore. Male Circular sucker immediately anterior to anus, ventrally directed, posterior portion slightly deeper than anterior. Approximately 14 pairs of sessile caudal papillae, variable in size, arranged from anteriorly as follows: two pairs of small papillae, near mid-ventral line, two pairs of larger well spaced papillae transversely across ventral surface immediately anterior to sucker; another two pairs of large similarly arranged paracloacally, immediately posterior to sucker, and two pairs of smaller papillae posterior to these. Postcloacally and midventrally, one small pair and two large pairs. In addition, one pair of dorso lateral papillae just before tip of tail, and two pairs of large and one of small papillae laterally or dorso laterally. Spicules similar, long, curved ventrally, tapering gradually to blunt tip, heavily sclerotised except at the tips, retracted in almost all specimens, one-sixth to one-seventh length of body. Gubernaculum straight, expanded at base and tapering to point, usually just extruded from cloaca, about one-quarter to one-fifth length of spicules. Female Vulva a narrow horizontal slit at mid-length of body. Eggs relatively large, elongated, length almost twice breadth, in some cases slightly flattened on one side, unembryonated, thickwalled, with finely pitted surface. Biology Locations in the host, and disposition of Abbreviata physignathi Abbreviata physignathi occurred almost exclusively in the stomach, with a few specimens present in the upper intestine in heavy infections. All specimens were dorsally curved and often tightly coiled, so that in females the vulva and anus were on the convex surface. One host had a mature male and female beneath each eyelid as well as five in the stomach. S. fluviatica and M. brygooi occurred in the lower intestine and rectum, and O. samfordensis within the body cavity. All other nematodes were recovered from the stomachs of their hosts. Prevalence, intensity and concurrent infections Abbreviata physignathi and S. fluviatica were the most prevalent nematodes, occurring in 48% and 44% respectively of lizards examined. Up to 208 A. physignathi were found (mean = 28, s.d. = 42.4); 35% of lizards contained <10 worms. Prevalence in New South Wales was 72%. Up to 191 S. fluviatica were found (mean = 15.7, s.d. = 37.4). Fewer than 10 worms were involved in 70% of infections; all worms in the Figs 1 6. Spinicauda fluviatica, sp. nov. 1, Anterior end, lateral view, showing oesophagus and excretory sinus. 2, Anterior end, en face. 3, Anterior end, ventral view, lips extended. 4, Oesophageal bulb and excretory sinus, lateral view. 5, Tail, female, lateral view. 6, Egg. Measurements in mm. Figs 7 8. Spinicauda fluviatica, sp. nov. 7, Tail, male, lateral view. 8, Tail, male, ventral view. Measurements in mm.

164 Australian Journal of Zoology H. I. Jones most heavily infected hosts were small adults. Prevalence in New South Wales was 54%. Concurrent infection with A. physignathi and S. fluviatica was significantly correlated (χ 2 1 = 11.11, P < 0.001). Other species of nematode occurred in one or two hosts only, in numbers ranging from 1 to 4. Distribution and geographical range (Figs 9 and 10) All infections with A. physignathi occurred in New South Wales between 34.5 S (south of Sydney) and 29 S (the Queensland border) within 100 km of the coast. None were recovered from either Victoria or from Queensland. The range of S. fluviatica extended slightly further south, with two infections in Victoria and one in the Snowy Mountains; all infections were within 100 km of the coast. Size of hosts and infection The mean size (snout vent length) of hosts was larger in New South Wales (213 mm, range = 78 270 mm) than in Victoria (177 mm, range = 85 250 mm), though the size range was similar. There was no correlation between host size and infection with either A. physignathi or S. fluviatica; two of the smallest lizards from New South Wales (snout vent length 78 and 120 mm) contained three S. fluviatica, and 19 A. physignathi and one S. fluviatica respectively. The hosts with the two highest intensities of infection (208 with A. physignathi and 191 with S. fluviatica) were below the mean size. Food residues in host stomachs Two-thirds of stomachs examined contained food residues: 11 contained vegetable remains (including small twigs and 400 km 14 S 400 km 14 S 20 S 20 S Qld Qld 26 S 26 S NSW 32 S NSW 32 S Vic. Vic. 140 E 146 E 152 E 38 S 140 E 146 E 152 E 38 S Fig. 9. Distribution of Abbreviata physignathi in Physignathus lesueurii (empty circles, no infection, black circles, infection present). Dotted line limit of distribution of P. lesueurii. Fig. 10. Distribution of Spinicauda fluviatica, sp. nov. in Physignathus lesueurii (empty circles, no infection; black circles, infection present).

Nematodes from Physignathus lesueurii Australian Journal of Zoology 165 some large berries) and 32 contained arthropod remains. Apart from one centipede, one millipede and many beetle elytra, all appeared to be small prey items and no precise identifications were possible. A higher proportion of lizards in Queensland and New South Wales (72%) contained food residues than did the more southerly specimens from Victoria and South Australia (61%); food residues and presence of nematode infection were not correlated. Etymology From fluviaticus, Latin for of, or belonging to, rivers, referring to the habitat of the host. Discussion Systematics Species descriptions based on one or few individuals will not reveal the range in characters or range of vital measurements that may occur, and therefore descriptions of new species that differ only slightly from previously described species may have to be interpreted with caution. In the new species of Spinicauda described herein, several hundred specimens were seen, and these displayed variations in such features as disposition of somatic and caudal papillae. Specimens in poor condition made the examination of such features difficult and prone to misinterpretation. Nevertheless, the characters displayed by S. fluviatica are sufficiently distinctive and consistent to differentiate them from previously described species. Travassos (1920) erected Spinicauda and placed within it several species previously assigned to other genera. The most conspicuous features that differentiate S. fluviatica, sp. nov., from others in the genus are the prominent sclerotised excretory sinuses leading to the excretory pore. A large excretory sinus is described in S. voltaensis, but not in any other species. Two other species of Spinicauda have been described from Australia: S. australiensis (Baylis 1930) from the skink Tiliqua scincoides and S. moretonis from the python Morelia spilotes (Jones 1979a). The present species differs from S. australiensis and S. moretonis in the following respects: S. physignathi is larger than S. australiensis though similar in size to S. moretonis. The spicules in the male are significantly longer than those in S. australiensis (600 650 µm) and considerably longer than those in S. moretonis (270 310 µm). They are also proportionately longer, being approximately one-fifth of the total worm length (15.8% of total length in S. australiensis and 6.5% of total length in S. moretonis). The gubernaculum is also longer than in these two species, and is one-quarter of the spicule length (~22% in S. australiensis and ~50% the spicule length in S. moretonis). Caudal papillae are similar to those in S. australiensis but more numerous than those in S. moretonis, though in a series of examinations there is variety in these papillae; as some specimens were poorly preserved, this variety may have been artefactual. The eggs of S. australiensis also have a finely sculpted surface, as in S. fluviatica, but are smooth-shelled in S. moretonis. In comparing measurements, however, it must be noted that the numbers of S. australiensis measured are not recorded, and only four of each sex were measured in S. moretonis. Thus this species is similar to S. australiensis in many respects, differing primarily in the size and ratio of the spicules and gubernaculum, the presence of somatic alae and the conspicuous sclerotised excretory sinuses. Species of Spinicauda have been described from reptiles and from some amphibians from many other parts of the world: S. spinicauda from the lizard Tejus teguexin in Brazil (Travassos 1920), S. sonsinoi from chameleons and skinks in Egypt (Moravec et al. 1987), S. hardwickii from the gecko Eublepharis hardwickii in India (Deshmukh and Choudhari 1979), S. regiensis from a captive Python regius in North America (Platt and Bush 1979), S. eryxi from the brown sand boa Eryx johnii in India (Agrawal 1966), S. inglisi from two species of chameleon in Madagascar (Chabaud and Brygoo 1960), S. dugesii from the lacertid lizard Podarcis dugesii in Madeira (Sanchez Gumiel et al. 1991), S. longispiculata from Gekko gecko in Java (Baylis 1929), S. murhari from Python molurus in India (Naidu 1981), S. fisheri from the amphibian Platymantis pelewensis in the Pacific Palau Islands (Bursey and Goldberg 2004), and S. voltaenesis in a toad (Bufo sp.) in Upper Volta, Africa (Baker and Bain 1981). In addition to the conspicuous excretory sinuses, S. fluviatica, sp. nov., differs from the above species in the following respects: in S. fluviatica the copulatory spicules are up to twice the length of those in all other described species except S. dugesii, S. voltaensis (in which the gubernaculum is lacking: Baker and Bain 1981) and S. longispiculata. S. komodoensis from the mock viper Psammodynastes pulverulentus in Komodo, Indonesia (Pinnell and Schmidt 1977), possesses a very deep posteriorly directed sucker, and has been transferred to the genus Moaciria (Baker and Bain 1981). Somatic papillae are not mentioned as being present in S. australiensis, S. voltaensis or S. murhari. The finely sculpted or pitted surface of the eggs is conspicuous in all gravid female specimens of S. fluviatica. A similar condition is described in S. australiensis (Baylis 1930), S. inglisi (Chabaud and Brygoo 1960) and S. spinicauda (Travassos 1920); eggs are smoothshelled in S. sonsinoi (Moravec et al. 1987), S. fisheri (Bursey and Goldberg 2004) and S. dugesii (Sanchez Gumiel et al. 1991), are said to be viviparous in S. eryxi (Agrawal 1966), and were measured but their surface not commented on in S. regiensis and S. murhari. No eggs were present in the uterus of S. voltaensis, and the descriptions of S. komodoensis and S. hardwickii are based on a single male each. Three species in the related genus Moaciria (Spinicaudinae) have been recorded from reptiles in Australia; all are readily distinguished from Spinicauda by the presence of caudal alae, the much deeper posteriorly directed precloacal sucker and the short tail (Jones 1979b). Biology Nematodes in the genus Abbreviata are widespread in the larger species of lizards and in many snakes in Australia, and exhibit varying degrees of host-specificity. A. physignathi has been recorded only in P. lesueurii. A. antarctica, on the other hand, is found in the larger reptile species in the families Varanidae (Johnston and Mawson 1941a, 1941b; Jones 2005), Agamidae (Jones 1986), Scincidae (Jones 1992) and Elapidae (Jones 1978). A. anomala and A. pilbarensis possess a row of

166 Australian Journal of Zoology H. I. Jones small denticles along the medial margin of the labia (Jones 1986). Both occur in Pogona lizards from drier and more tropical areas, and in both species the denticles are smaller and less pronounced than in A. physignathi. A related genus, Kreisiella, possesses an even row of labial margin denticles without the apical, dorsal and ventral denticles, and occurs in smaller desert skinks and geckos, especially Egernia inornata (Jones 1985). A second species of Kreisiella was described from Pogona minor (Jones 1986). The condition of small denticles occurring along the medial labial margin thus appears to be restricted predominantly to agamid lizards; those of A. physignathi, however, are larger and less differentiated from the apical, dorsal and ventral denticles than in the previous species. The retention of generalised apical characters in the form of numerous unspecialised denticles (to a more marked degree than in any other Australian species of Abbreviata), the relatively high prevalence of infection, and its restriction to one host species indicate a close and successful association with P. lesueurii, and may reflect the early divergence of this lizard from the main agamid stock. However, the presence of low numbers of nematodes of other species, which are widespread in other species of sympatric reptiles, indicates that P. lesueurii is not fully ecologically isolated. The unusual site of adult worms beneath the eyelids of the host, as in the type description (Baylis 1924) and in one host in the present study (though not all eyelids were examined), is noteworthy, and may be related to aspects of the hosts physiology, or to its aquatic environment. Other species of physalopterid nematodes exhibit similar prevalence in the larger Australian agamid lizards, e.g. Skrjabinoptera goldmanae in Pogona spp. (30%) and in Chlamydosaurus kingii (50%) (Jones 1986, 1994). Spinicauda fluviatica is the first nematode in this genus to be described from an agamid lizard; none were found in 115 Pogona spp. or in 24 Chlamydosaurus kingii (Jones 1986, 1994). The finding of Spinicauda spp. in Morelia spilotes and Tiliqua spp. in north Queensland (Baylis 1930; Jones 1979a), and their absence from the rectums of 82 Tiliqua spp. in Western Australia (Jones 1992), suggest that a more humid or wetter environment may be necessary for the survival of the free-living stages of this genus. Prevalence and intensity of Spinicauda spp. are variable: S. moretonis (Jones 1979a) occurred in 1 of 49 pythons examined, and S. australiensis was collected from T. scincoides on several occasions (Baylis 1930); S. dugesii occurred in 17% of 412 Podarchis dugesii at a low mean intensity of 1.8 (Sanchez Gumiel et al. 1991), S. fisheri in 2 of 7 Platymantis pelewensis at intensities of 7 and 57 (Bursey and Goldberg 2004), and S. sonsinoi in 1 of 5, 2 of 5 and 1 of 19 of three species of chameleon in Egypt, at intensities of 6 123 (Moravec et al. 1987). Travassos (1920) reported that S. spinicauda was relatively rare. The prevalence and maximum intensity of S. fluviatica are therefore higher than in other species for which records are available. Prevalence, intensity and geographical range have not been reported in other species of Spinicauda. The restricted and correlated distribution of the two principal nematodes, A. physignathi and S. fluviatica, is of interest, as spirurid nematodes require an arthropod intermediate host, whereas Heterakoidea are monoxenous (Anderson 1992). However, the few specimens of P. lesueurii from Queensland may not represent the true status of these two nematode species in the more northerly parts of its range. The southern limit of distribution of A. physignathi may relate to the southern distribution of the (unknown) intermediate arthropod host. A possible explanation for the significant concurrent infections of these two nematodes may be the high density of lizards along river habitats, thus facilitating successful transfer of nematode eggs or larval stages: A. physignathi infected two specimens of P. lesueurii that had been collected from the Gloucester River in New South Wales, where Thompson (1993) found a high density of these lizards. P. lesueurii is very common in the coastal areas of the Brisbane River drainage; in contrast, its distribution is patchy in mid-eastern and in north-eastern Queensland, and it appears to be scarce in some of these areas (P. Couper, pers. comm.). The absence of any correlation between host size and infection suggests that females, which are smaller than males, are as liable to infection as males. Smaller lizards may have been either males or females that had not yet reached full size, indicating that the lizards can acquire infection at a relatively early stage in their growth. The higher proportion of lizards without food in their stomachs in the more southerly parts of their range, where digestive processes would be slower due to lower ambient temperatures, suggests that food intake is lower (and the lizards are, on average, smaller), and this may also be a factor in the lower prevalence of infection. A. antarctica and A. confusa were accidental infections; both species occur sympatrically in Varanus varius in eastern Australia (Johnston and Mawson 1941a; H. Jones, unpub. data). M. brygooi was recorded from Amphibolurus muricatus from New South Wales (Mawson 1972), and is widely distributed throughout much of Australia. Skrjabinoptera goldmanae, which is predominantly a parasite of agamid lizards, has been recorded from hot and arid environments (western New South Wales) (Mawson 1970) and from tropical environments in northern Australia (Jones 1994), and its absence from P. lesueurii probably relates to this lizard s allopatric distribution and specialised semiaquatic habitat. Nematodes in the genus Dracunculus have recently been described from Australia (Jones and Mulder 2007); these occurred in water pythons (Liasis fuscus) in the Northern Territory, and the finding of an immature specimen near Sydney illustrates that the genus evidently occurs widely in Australia. If this species requires an aquatic arthropod as an intermediate host, as in Dracunculus medinensis, the finding of an immature specimen within the stomach of one P. lesueurii may be the result of accidental ingestion, or indicate that P. lesueurii also feeds on aquatic prey; Greer (1989) suggests that this host does feed underwater, and stomach flushing recovered only terrestrial prey (M. Thompson, pers. comm.). O. samfordensis is readily identifiable by the character of the spicules (Manzanell 1982). The shorter length of the single female (45 mm) and the slightly more anterior vulva than in the original description is attributed to its immaturity, as no microfilariae were visible within the eggs. The preserved condition of the lizards precluded a more thorough examination of the body cavity and lining membranes, and the prevalence of Oswaldofilaria may have been higher.

Nematodes from Physignathus lesueurii Australian Journal of Zoology 167 Conclusions The nematode fauna of Physignathus lesueurii is dominated by two species: Abbreviata physignathi in the stomach and Spinicauda fluviatica in the rectum. Both are known to occur only in this host species, suggesting a successful ecological or evolutionary association with this genetically isolated large aquatic lizard. The presence of the two nematode species is closely correlated, and is probably a function of the high density of lizards in rivers where they occur. Other nematodes recovered were probably accidental infections, as all occur at higher intensity and prevalence in other Australian reptiles. Acknowledgements I thank Dianne Bray, Museum Victoria, Patrick Couper, Queensland Museum, Mark Hutchinson, South Australian Museum, and Ross Sadlier, Australian Museum, for allowing me to examine lizards in their care, and for providing collection data. 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