No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Taking stock: a review of the known parasites of the sleepy lizard, Tiliqua rugosa (Gray, 1825), a common lizard endemic to Australia
Abstract
Parasitism is a very common life strategy and although it results in harm to the host, it plays a vital ecological role in host population and community dynamics. The sleepy lizard, Tiliqua rugosa, is one of the best studied lizard species in Australia, to a large extent due to studies involving ticks that infest these lizards. In spite of this, little is known about most of the parasites that are known to infect sleepy lizards. The purpose of this review is to provide a synopsis of the species that have been reported as parasites of T. rugosa as a foundation for future studies.
... Our knowledge of pathogen challenges is also limited in squamates, although information for T. rugosa is more comprehensive than for most (54,55). The species and its interactions with parasites, primarily with ectoparasitic ticks, has been under continuous study for 40 y at a site in South Australia (56). ...
... The species and its interactions with parasites, primarily with ectoparasitic ticks, has been under continuous study for 40 y at a site in South Australia (56). In addition, tickborne rickettsia and protozoan parasites have also been identified in ticks associated with T. rugosa (55). Future directions should focus on how ab T cells or other components of the immune system may be compensating for the roles normally filled by gd T cells in other vertebrates. ...
T lymphocytes or T cells are key components of the vertebrate response to pathogens and cancer. There are two T cell classes based on their TCRs, αβ T cells and γδ T cells, and each plays a critical role in immune responses. The squamate reptiles may be unique among the vertebrate lineages by lacking an entire class of T cells, the γδ T cells. In this study, we investigated the basis of the loss of the γδ T cells in squamates. The genome and transcriptome of a sleepy lizard, the skink Tiliqua rugosa, were compared with those of tuatara, Sphenodon punctatus, the last living member of the Rhynchocephalian reptiles. We demonstrate that the lack of TCRγ and TCRδ transcripts in the skink are due to large deletions in the T. rugosa genome. We also show that tuataras are on a growing list of species, including sharks, frogs, birds, alligators, and platypus, that can use an atypical TCRδ that appears to be a chimera of a TCR chain with an Ab-like Ag-binding domain. Tuatara represents the nearest living relative to squamates that retain γδ T cells. The loss of γδTCR in the skink is due to genomic deletions that appear to be conserved in other squamates. The genes encoding the αβTCR chains in the skink do not appear to have increased in complexity to compensate for the loss of γδ T cells.
... Wild and captive reptiles are vulnerable to parasites both in vitro and in vivo. In Australia, there are more than 70 different species of ticks, 14 of which will parasitize reptiles [13]. Furthermore, Cryptosporidium infections have been reported in at least 57 reptilian species [14], with chronic cryptosporidiosis and lethality in some snakes [14,15]. ...
The highly endangered crocodile lizard (Shinisaurus crocodilurus) continues to be impacted by disease, especially in captive breeding populations. In this paper, based on high-throughput sequencing, we investigated parasitic infections in captive and wild crocodile lizard populations in the Daguishan National Nature Reserve and Guangdong Luokeng Shinisaurus crocodilurus National Nature Reserve. The results show that the overall parasitic infection rate in crocodile lizards was 33.33% (23/69). Four parasite genera were detected, including Eimeria, Cryptosporidium, Nematopsis, and Acanthamoeba, with infection rates of 15.94% (11/69), 17.39% (12/69), 7.25% (5/69), and 4.35% (3/69), respectively. Significant differences in the infection rate were found between the different parasite species (χ2 = 8.54, p < 0.05, chi-squared test). The parasitic infection rates in the captive and wild populations were 39.29% (22/56) and 7.69% (1/13), respectively, which were significantly different (p < 0.05, Fisher’s exact test). However, no significant differences in the infection rates of the four parasite genera were found between the captive and wild populations (p > 0.05, Fisher’s exact test). The parasitic infection rates in Daguishan and Luokeng were 34.09% (15/44) and 32.00% (8/25), respectively, which were not significantly different (p > 0.05, Fisher’s exact test). However, significant differences in terms of species were found in the two reserves (p < 0.01, Fisher’s exact test). Only Cryptosporidium infection showed a significant difference between the two regions (p < 0.01, Fisher’s exact test). Our results suggest that captive crocodile lizards are more susceptible to parasitic diseases than wild crocodile lizards and that Cryptosporidium infection varies by geographical region. This study provides basic information about the parasites of endangered crocodile lizards, as well as a reference for disease control and conservation.
Professor C. Michael Bull was a great scientist and mentor, and an Associate Editor of this journal. While his research career spanned the fields of behavioural ecology, conservation biology and herpetology, in this article, we pay tribute to his major contribution to Australian parasitology. Mike authored more than eighty articles on host-parasite ecology, and revealed major insights into the biology and ecology of ticks from his long term study of the parapatric boundary of two tick species (Amblyomma limbatum and Bothriocroton hydrosauri) on the sleepy lizard (Tiliqua rugosa). In this article, we provide an overview of how this research journey developed to become one of the longest-running studies of lizards and their ticks, totalling 35 years of continuous surveys of ticks on lizards, and the insights and knowledge that he generated along that journey.
A respiratory disease syndrome has been observed in large numbers of wild shingleback lizards (Tiliqua rugosa) admitted to wildlife care facilities in the Perth metropolitan region of Western Australia. Mortality rates are reportedly high without supportive treatment and care. Here we used next generation sequencing techniques to screen affected and unaffected individuals admitted to Kanyana Wildlife Rehabilitation Centre in Perth between April and December 2015, with the resultant discovery of a novel nidovirus significantly associated with cases of respiratory disease according to a case definition based on clinical signs. Interestingly this virus was also found in 12% of apparently healthy individuals, which may reflect testing during the incubation period or a carrier status, or it may be that this agent is not causative in the disease process. This is the first report of a nidovirus in lizards globally. In addition to detection of this virus, characterisation of a 23,832 nt segment of the viral genome revealed the presence of characteristic nidoviral genomic elements providing phylogenetic support for the inclusion of this virus in a novel genus alongside Ball Python nidovirus, within the Torovirinae sub-family of the Coronaviridae. This study highlights the importance of next generation sequencing technologies to detect and describe emerging infectious diseases in wildlife species, as well as the importance of rehabilitation centres to enhance early detection mechanisms through passive and targeted health surveillance. Further development of diagnostic tools from these findings will aid in detection and control of this agent across Australia, and potentially in wild lizard populations globally.
Rickettsiosis is a potentially fatal tick borne disease. It is caused by the obligate intracellular bacteria Rickettsia, which is transferred to humans through salivary excretions of ticks during the biting process. Globally, the incidence of tick-borne diseases is increasing; as such, there is a need for a greater understanding of tick-host interactions to create more informed risk management strategies. Flinders Island spotted fever rickettsioses has been identified throughout Australia (Tasmania, South Australia, Queensland and Torres Strait Islands) with possible identifications in Thailand, Sri Lanka and Italy. Flinders Island spotted fever is thought to be spread through tick bites and the reptile tick Bothriocroton hydrosauri has been implicated as a vector in this transmission. This study used qPCR to assay Bothriocroton hydrosauri ticks collected from Tiliqua rugosa (sleepy lizard) hosts on mainland South Australia near where spotted fever cases have been identified. We report that, although we discovered Rickettsia in all tick samples, it was not Rickettsia honei. This study is the first to use PCR to positively identify Rickettsia from South Australian Bothriocroton hydrosauri ticks collected from Tiliqua rugosa (sleepy lizard) hosts. These findings suggest that B. hydrosauri may be a vector of multiple Rickettsia spp. Also as all 41 tested B. hydrosauri ticks were positive for Rickettsia this indicates an extremely high prevalence within the studied area in South Australia.
Nymphae of Amblyomma limbatum Neumann, engorged on the Australian sleepy lizard Tiliqua rugosa Gray infected with haemogregarine blood-stage gametocytes, were studied by light and electron microscope 3-57 days after detachment. Examined ticks demonstrated haemogregarine oocysts and sporogonic stages. Oocysts found in the intestinal epithelium, were three to five arm star-shaped, and divided into numerous sporokinetes. The sporokinetes spread to various tissues and, after transforming into hard-walled sporocysts, divided into sporozoites. This course of development in the vector is characteristic of the genus Hemolivia Petit, Landau, Baccam & Lainson, 1990 reported earlier from toads and ticks. The reported haemogregarinid is therefore described as Hemolivia mariae n. sp.
Cercariae and metacercariae of three species of the Microphallidae Travassos, 1920 were found in snails and crustaceans from tributaries of the Brisbane River, Queensland, Australia. Specimens of Maritrema brevisacciferum Shimazu et Pearson, 1991 and Microphallus minutus Johnston, 1948, which have previously been reported in Queensland, were found as cercariae in the tateid gastropod Posticobia brazieri (Smith) and as metacercariae of M. brevisacciferum in the atyid shrimp Caridina indistincta Calman and of M. minutus in the parastacid crayfish Cherax dispar Reik. Combined analysis of morphological and molecular data, based on newly generated ITS2 and partial 28S rDNA data, linked cercariae and metacercariae for both species. This is the first report of the first intermediate hosts of M. brevisacciferum and M. minutus. Infections of another unidentified microphallid metacercariae, Microphallidae gen. sp., were found in P. brazieri and C. indistincta. The sequences of metacercarial isolates from both hosts were identical. The data on the Microphallidae from Australia and species that develop in freshwater invertebrates were examined in detail.
The endoparasitic worms in reptiles from Tasmania and the islands of Bass Strait were recorded from dissections of nine TYmpanocryptis diemensis, six Tiliqua nigrolutea, 20 Cyclodomorphus casuarinae, 15 Egernia whitii, 17 Austrelaps superbus, 24 Notechis ater, seven Drysdalia coronoides and four Pelamis platurus. Thirteen species of worms were recorded, namely, the pentastomes Waddycephalus superbus and Wad-dycephalus ?sp. nov., an unidentified oxyurid nematode species, the nematodes Maxvachonia brygooi, M chabaudi, Strongyluris paronai, Moaciria sp., Paraheterotyphlum australe, Ophidascaris pyrrhus, Kreisiella sp., Abbreviata antarctica, the trematode Dolichoperoides macalpini and the cestode Oochoristica vacuo lata. The roundworm O. pyrrhus was most prevalent, occurring almost entirely in the Black Tiger Snake, N ater. The fluke D. macalpini was found, often at high intensity, in the Black Tiger Snake and in the Copperhead, A. superbus. No other worms occurred in more than two of any host species, and, apart from A. antarctica and S. paronai, all nematodes were at an intensity of four or less worms per host. Six of the 13 helminth species were recovered only from the Bass Strait islands. Previous studies in mainland Australia demonstrate that the reptile species examined in the present study (N ater), or related species in the same genera (Tiliqua, Cyclodomorphus, Egernia, Drysdalia), may support a greater range and number of nematodes. The possible reasons for the lower worm numbers in Tasmania include the effects of a cool and damp climate on the distribution of the worms' intermediate hosts and on the survival of free-living stages of the parasites, and geographical isolation.
ABSTRACT: Parasites are agents of disease in humans, livestock, crops, and wildlife and are powerful representations of the ecological and historical context of the diseases they cause. Recognizing a nexus of professional opportunities and global public need, we gathered at the Cedar Point Biological Station of the University of Nebraska in September 2012 to formulate a cooperative and broad platform for providing essential information about the evolution, ecology, and epidemiology of parasites across host groups, parasite groups, geographical regions, and ecosystem types. A general protocol, documentation– assessment–monitoring–action (DAMA), suggests an integrated proposal to build a proactive capacity to understand, anticipate, and respond to the outcomes of accelerating environmental change. We seek to catalyze discussion and mobilize action within the parasitological community and, more widely, among zoologists and disease ecologists at a time of expanding environmental perturbation.
The book Australian Ticks by F.H.S. Roberts (1970) is a land-mark in Australian tick biology. But it is time for a new and improved book on the ticks of Australia. The present book has identification guides and accounts of the biology and diseases associated with the 16 species of ticks that may feed on domestic animals and humans in Australia. These comprise five argasid (soft) ticks: Argas persicus (poultry tick), Argas robertsi (Robert's bird tick), Ornithodoros capensis (seabird soft tick), O. gurneyi (kangaroo soft tick), Otobius megnini (spinose ear tick); and 11 ixodid (hard) ticks, Amblyomma triguttatum (ornate kangaroo tick), Bothriocroton auruginans (wombat tick), B. hydrosauri (southern reptile tick), Haemaphysalis bancrofti (wallaby tick), H. longicornis (bush tick), Ixodes cornuatus (southern paralysis tick), I. hirsti (Hirst's marsupial tick), I. holocyclus (paralysis tick), I. tasmani (common marsupial tick), Rhipicephalus (Boophilus) australis (Australian cattle tick) and R. sanguineus (brown dog tick). We use an image-matching system to identify ticks, much like the image-matching systems used in field-guides for birds and flowers. Ticks may be identified by drawings that emphasise unique matrices of uniformly defined morphological characters that, together, allow these 16 ticks to be identified by morphology unequivocally. The species accounts have seven sections: (i) General; (ii) Differential diagnosis; (iii) Hosts; (iv) Life-cycle and seasonality; (v) Disease; (vi) Habitat and geographic distribution; (vii) Genes and genomes; and (viii) Other information. There are 71 figures and tables, including a glossary character matrices, drawings of life-cycles, drawings of genera, species, and colour photographs of tick biology.
In a study of ticks parasitizing reptiles in the western half of Australia, eight species, including two
undescribed ticks, were identified. The data confirm that three species, Amblyomma albolimbatum, Amb.
limbatum and Aponomma hydrosauri, have distributions which abut with very little overlap (i.e. they
are parapatric). Ap, fimbriatum is sympatric with Amb. albolimbatum and Ap. hydrosauri. The other
ticks identified, Aponomma sp. nov., Amblyomma sp. nov., Amb. calabyi and Ornithodoros gurneyi, were
not found in sufficient numbers to allow detailed descriptions of their distributions. Data are also
presented on the hosts of the ticks and on the occurrence of ticks on islands off the Western Australian
coast.
Parasites appropriate host resources to feed and/or to reproduce, and lower host fitness to varying degrees. As a consequence, they can negatively impact human and animal health, food production, economic trade, and biodiversity conservation. They can also be difficult to study and have historically been regarded as having little influence on ecosystem organization and function. Not surprisingly, parasitic biodiversity has to date not been the focus of much positive attention from the conservation community. However, a growing body of evidence demonstrates that parasites are extremely diverse, have key roles in ecological and evolutionary processes, and that infection may paradoxically result in ecosystem services of direct human relevance. Here we argue that wildlife parasites should be considered meaningful conservation targets no less relevant than their hosts. We discuss their numerical and functional importance, current conservation status, and outline a series of non-trivial challenges to consider before incorporating parasite biodiversity in conservation strategies. We also suggest that addressing the key knowledge gaps and communication deficiencies that currently impede broad discussions about parasite conservation requires input from wildlife parasitologists.
A model that weighs the energetic cost of parasitism for a predator against the energetic value of prey items that transmit the parasite to the predator suggests that there is often no selective pressure to avoid parasitized prey. This offers an explanation for why parasites so frequently exploit predators and prey as definitive and intermediate hosts, respectively. Furthermore, predators may actually benefit from their parasites if energetic costs of parasitism are moderate and prey capture is facilitated by parasites. Parasite species that benefit predators through modification of prey are not mutuatistic, however.
Reptiles and Amphibians of Australia is a complete guide to Australia’s rich and varied herpetofauna, including frogs, crocodiles, turtles, tortoises, lizards and snakes. For each of the 1218 species there is a description of its appearance, distribution and habits. Each species is accompanied by a distribution map and, in most cases, a colour photograph of the living animal. The book includes 130 simple-to-use dichotomous keys that in most cases allow a specimen in hand to be identified. In addition, it has a comprehensive list of scientific references for those wishing to conduct more in-depth research, an extensive glossary, and basic guides to the collection, preservation and captive care of specimens. This classic work, originally published in 1975, has been completely brought up to date. This seventh edition includes all species described prior to October 2013.
Certain groups of protozoan parasites, particularly haemosporidans, flagellates and coccidians, have been widely incriminated as controlling agents of wildlife populations, but this paper shall consider only their impact on avifauna. While it is generally believed that protozoans do act as limiting factors on avian populations, it is suggested that these conclusions, for the most part, are based on the impact of such diseases on populations which are not native to the region involved. It is further suggested that there are insufficient data to determine whether protozoan diseases do indeed have any substantial impact on natural populations. While it is entirely possible that such diseases may exert a controlling or limiting influence on bird populations, the lack of necessary baseline data precludes definitive conclusion. It is suggested therefore that before such questions can be answered, baseline data on such aspects as reproductive rates, survival rates, influence of climatic factors and non-protozoan diseases, etc., must be ascertained for each population in each area under study.
Coccidiosis, i.e. infection with Eimeria and Isospora spp., is of great economic importance in agriculture. This is especially true of poultry production but, with the adoption of more intensive systems of husbandry for other domestic animals, the disease is beginning to assume greater proportions in these species also (Gregory et al. 1980; Joyner et al. 1981; Fitzgerald 1980). In the case of poultry it is unlikely that the broiler industry would have developed to its present extent in the absence of a means of controlling the parasite, i.e. effective medication (Ryley 1982). Because of the ever-recurring problem of drug resistance this has necessitated a constant search for new compounds. The cost of this research, coupled with that of development and testing, has risen to such an extent that few pharmaceutical companies are now engaged in such work (Ryley 1982). The need for an alternative means of control is, therefore, becoming more urgent and is arousing considerable interest in the possibility of vaccination against the disease. Hitherto, effort has been concentrated on the development of live attenuated strains of the various Eimeria spp. for use as prophylactic agents since the limited attempts to induce protective immunity by the injection of various crude preparations of non-viable parasite material have been unsuccessful (see Rose and Long 1980).
Despite an extremely voluminous international literature relating to herptiles and bacteria of the genera Salmonella and Arizona, there are few reports which suggest these bacteria are pathogenic for amphibians or reptiles. Extensive listings of serotypes recovered from live or dead herptiles exist, with the greater proportion of isolates coming from vivarium collections or animals destined for the pet trade (Hoff and White, 1977). However, the emphasis for examining these animals has come from two sources, curiosity and public health concern, rather than herptilian husbandry. The reptiles, especially, have been shown to be a rich source of Salmonella and Arizona organisms for bacteriological study. The public health concern derives from the fact that both genera of bacteria are known to embrace human pathogens.
A single female Amblyomma triguttatum triguttatum found on a sleepy lizard, Tiliqua rugosa, in the mid-north of South Australia constitutes a new host and locality record for this tick. As A. t. triguttatum is involved with the natural cycle of Coxiella burnetii in Australia, the new locality record may indicate the potential for spread of this disease
The life cycle of many bacterial species requires a transition between two very distinct environments. Their primary habitat is the gastro-intestinal tract of the host, while their secondary habitat, during transmission from one host to another, consists of environments external to the host such as soil, water and sediments. Consequently both host and environmental factors will shape the genetic structure of enteric bacterial populations. This study examined the distribution of four Salmonella enterica subspecies in a population of sleepy lizards, Tiliqua rugosa, in a semi arid region of South Australia. The lizards living within the 1920 m by 720 m study site were radio tracked, and their enteric bacteria sampled at regular intervals, throughout their activity season in the years 2001, 2002 and 2006. Four of the six subspecies of S. enterica were present in this population, and were non-randomly distributed among the lizards. In particular the subspecies S. enterica diarizone was restricted to lizards living in the most shaded parts of the study site with an overstorey of Casuarina trees. Experiments undertaken to investigate the survival of S. enterica cells under semi-natural conditions, revealed that cell survival decreased with increased exposure to elevated temperatures and UV light. Among the three S. enterica subspecies tested, S. enterica diarizone consistently had an average expected lifespan that was shorter than that observed for the other two subspecies. There was no indication in the data that there was any competitive dominance hierarchy among the S. enterica subspecies within individual hosts. Thus the non-random distribution of S. enterica subspecies in this population of lizards appears to be driven by their different survival characteristics in the external environment.
Copyright © 2015, American Society for Microbiology. All Rights Reserved.
Seventy species of ticks are known from Australia: 14 soft ticks (family Argasidae) and 56 hard ticks (family Ixodidae). Sixteen of the 70 ticks in Australia may feed on humans and domestic animals (Barker and Walker 2014). The other 54 species of ticks in Australia feed only on wild mammals, reptiles and birds. At least 12 of the species of ticks in Australian also occur in Papua New Guinea. We use an image-matching system much like the image-matching systems of field guides to birds and flowers to identify Ixodes holocyclus (paralysis tick), Ixodes cornuatus (southern paralysis tick) and Rhipicephalus (Boophilus) australis (Australian cattle tick). Our species accounts have reviews of the literature on I. holocyclus (paralysis tick) from the first paper on the biology of an Australian tick by Bancroft (1884), on paralysis of dogs by I. holocyclus, to papers published recently, and of I. cornuatus (southern paralysis tick). We comment on four controversial questions in the evolutionary biology of ticks: (i) were labyrinthodont amphibians in Australia in the Devonian the first hosts of soft, hard and nuttalliellid ticks?; (ii) are the nuttalliellid ticks the sister-group to the hard ticks or the soft ticks?; (iii) is Nuttalliella namaqua the missing link between the soft and hard ticks?; and (iv) the evidence for a lineage of large bodied parasitiform mites (ticks plus the holothyrid mites plus the opiliocarid mites).
This chapter analyzes the taxonomic position of Dicrocoeliidae family and several of its genus and species. The biology of the major species causing veterinary diseases such as Dicrocoelium dendriticum, Dicrocoelium hospes, Dicrocoelium chinensis, Eurytrema pancreaticum and Platynosomum fastosum, has been reviewed. All these species have an indirect life cycle, involving two intermediate hosts (molluscs as first and ants, grasshoppers and lizards as second). Dicrocoelium dendriticum is a very widespread hepatic trematode in the ruminants of many countries in Europe, Asia, North Africa and North America, even affecting humans. Dicrocoelium hospes is widely distributed in the savanna areas of Africa south of the Sahara, while D. chinensis has mainly been found in ruminants in East Asia and some European countries (probably imported from Asia). Eurytrema pancreaticum is a common parasite whose adults live in ruminant bile ducts, gall bladder, pancreatic ducts and intestines in Europe, Madagascar, Asia and South America. Adult P. fastosum live in the liver, gall bladder and pancreas of birds and mammals in Europe, Africa, Asia, North, Central and South America. Information about the epidemiology, pathology, clinical aspect, diagnosis, treatment, control, prevention and economic impact mainly of Dicrocoeliosis produced by D. dendriticum, as well as of Eurytrematodosis and Platynosomiosis has been included.
Intestinal trematodes are among the most common types of parasitic worms. About 76 species belonging to 14 families have been recorded infecting humans. Infection commonly occurs when humans eat raw or undercooked foods that contain the infective metacercariae. These parasites are diverse in regard to their morphology, geographical distribution and life cycle, which make it difficult to study the parasitic diseases that they cause. Many of these intestinal trematodes have been considered as endemic parasites in the past. However, the geographical limits and the population at risk are currently expanding and changing in relation to factors such as growing international markets, improved transportation systems, new eating habits in developed countries and demographic changes. These factors make it necessary to better understand intestinal trematode infections. This chapter describes the main features of human intestinal trematodes in relation to their biology, epidemiology, host–parasite relationships, pathogenicity, clinical aspects, diagnosis, treatment and control.
Parasites of all kinds alter the behaviour of their hosts. In many systems, these behavioural modifications appear adaptive for the parasite, by facilitating the completion of its life cycle. However, not all parasitized hosts are under the influence of parasites. This may be due to the timing of the onset of behavioural manipulation by the parasites: changes in behaviour may coincide with completed parasite development and only appear late in the infection. In addition, certain hosts may oppose the parasite's attempts at manipulating their behaviour. Hosts with high expected future reproductive success, i.e. young hosts or hosts that have not yet reproduced, are more likely to benefit by opposing the influence of parasites, as their expected gains would outweigh the costs of opposition. Such conditional opposition would be a better alternative to resistance to infection itself if resistance is costly, and would explain the considerable variability often observed in the behavioural responses of parasitized hosts. Future tests of these ideas should give insights into the coevolution of hosts and parasites and the parasites' struggle for the control of host behaviour.
This study examines the biology of gastric nematodes in two communities of lizards from the Great Victoria Desert, and develops an hypothesis for their evolution. Abbreviata antarctica A. hastaspicula, A, levicauda, A. tumidocapitis, Skrjabinoptera goldmanae, Kreisiella chrysocampa, Physalopteroides filicauda, Wanaristrongylus ctenoti and W. papangawurpae were recovered from 3023 lizards of 45 species from two different habitats. Genera in the Physalopterinae (Abbreviata, Skrjabinoptera and Kreisiella) exhibited narrow host specificities, Abbreviara and Skrjabinoptera occurring as adults only in larger host species (Varanus gouldii, V. tristis and Pogona minor). P. filicauda and encysted larvae of Physalopterinae occurred widely in the smaller lizard species in all five families represented. Eight of the nine nematode species were recovered from both lizard populations, and differences in prevalence and number of host species infected are discussed in terms of core hosts providing an infective pool. Associations were derived between parameters of infection (prevalence, intensity and abundance) and host size across and within species; abundance of nematodes in Ctenotus skinks correlated with host geographical range. Epidemiological evidence is presented that suggests that termites are intermediate hosts to species of Physalopterinae, and that Orthoptera may be intermediate hosts to P.filicauda. It is suggested that species in the Physalopterinae arose in smaller lizards (where they are now represented by the morphologically primitive Kreisiella), and that they were acquired by large predatory species by host capture, and in which they are now speciating. The small lizards now act as paratenic hosts to their larvae, and the niches left vacant have been occupied by P. filicauda. It is concluded that P.filicauda is at an early non-interactive phase and that Abbreviata and Skrjabinoptera are at an evolutionary phase, and are evolving along with their hosts. Thus, the two principal nematode groups arose at different times in response to the radiation and ecology of their hosts, and are at different stages in their own evolution.
Nine species of nematode were recovered from the gastrointestinal tract of 82 lizards in the genus Tiliqua and 41 lizards in the genus Cyclodomorphus (Scincidae) in Western Australia. Parapharyngodon fitzroyi, sp. nov. possesses lateral alae in males and a prominent postanal cone bearing two very small papillae. There is no sclerotised V-shaped accessory piece, and the spicular pouch opens immediately posterior to the anus. The female's tail is rounded with a small slightly posteriorly-directed terminal spike. This nematode possesses some characteristics of Thelandros, and it is suggested that the taxonomic criteria differentiating these two genera have yet to be clarified. P. fitzroyi occurred at low prevalence and generally low intensity in Tiliqua multifasciata and Cyclodomorphus branchialis in the centre and north of the State. Thelandros trachysauri exhibited morphological variability, with two spicule lengths in males, and a wide range in tail lengths in the female. This species predominated at high intensity in Tiliqua rugosa in the south ana west, and Pharyngodon tiliquae occurred at high intensity and prevalence in Tiliqua occipitalis.,Tiliqua multifasciata and Cyclodomorphus branchialis throughout the State. Despite extensive sympatry between two pairs of these oxyurid species, and a limited area of sympatry between all three, these nematodes did not occur concurrently in the same individual to any significant extent. Abbreviata antarctica occurred at high prevalence and intensity in T. occipitalis in the south and west of the State. Encysted physalopterid larvae were only seen in the stomachs of T. multifasciata, in central and northern areas. Other species recorded were Abbreviata tumidocapitis (larva only), Kreisiella lesueurii, Pseudorictularia disparilis, Physalopteroides filicauda and Maxvachonia brygooi. Differences in the nematode communities in these four lizard species can be related to host diet, geographical range of host and of nematode (possible environmental constraints on the free-living stages), and perhaps inherent insusceptibility to infection.
The nematodes Abbreviata antarctica, A. confusa, A. hastaspicula, A. levicauda, A. glebopalmae sp. nov., A. kimberleyensis sp. nov. and Tanqua tiara were collected from nine species of Varanus monitor lizards in tropical northern Australia. A. glebopalmae sp, nov. is characterised by dorso-ventral enlargement of the pseudolabia, hypertrophy of the anterior end of the oesophagus and an anteriorly situated vulva. A. kimberleyensis sp. nov. differs from A. perenticola (which is allopatric) by having denticles at the dorsal and ventral corner of each pseudolabium, and a row of 6-8 fine even denticles on the subdorsal and subventral medial surface of each pseudolabium.
Species of Abbreviata were recovered from between one and six host species, and each species of Varanus harboured between one and four species of Abbreviata. In each host species usually one (or in some cases two) nematode species were dominant. Ecological factors rather than susceptibility to infection appeared to be the major determinants of the composition of this nematode fauna.
Physalopteroides filicauda, Maxvachonia brygooi, M. chabaudi, and Wanaristrongylus ctenoti were also recovered, probably as accidental infections, and Dioctowittus denisoniae, Hastospiculum gouldi and Oswaldofilaria sp. were recovered from serous cavities. Hastospiculum drysdaliae is reduced to synonomy with H. gouldi.
Twelve species of nematode were recovered from the gastrointestinal tract of 115 lizards in the genus Pogona (Agamidae) in Western Australia. Seven species belonged to the Physalopteridae, and three new species are described: Abbreviata pilbarensis, sp. nov., occurs only in the Pilbara region and possesses relatively small dorsal and ventral pseudolabial teeth, inconstant and irregular small denticles on the medial pseudolabial surface, left spicule more than twice the length of the right, vulva with short wide posteriorly directed tubular extension, and thick-shelled eggs; Abbreviata anomala, sp. nov., occurs throughout the State, and possesses small pseudolabia, small dorsal and ventral pseudolabial teeth, an even row of 40-60 small denticles lining the medial pseudolabial surface, left spicule 3-4 times the length of the right, five pairs of pedunculate pericloacal papillae, and females with truncated rounded tail and vulva 3-5% of body length from anterior end; Kreisiella lesueurii, sp. nov., was identified from the south-west, and possesses a row of fine even denticles extending the width of the medial pseudolabial margin, no apical, dorsal or ventral pseudolabial teeth, a restricted area of tubercles on the male ventral tail surface, a short and thick right spicule, four pairs of pedunculate pericloacal papillae, caudal alae not meeting anteriorly and not extending to the tip of the tail, and females with truncated rounded tail and anteriorly placed vulva. The male of Maxvachonia brygooi is described: it possesses lateral alae and differs from M. chabaudi only in the larger size of the gubernaculum and spicules. Other species recorded were Strongyluris paronai, Physalopteroides filicauda, Skrjabinoptera goldmanae, Abbreviata antarctica, Pseudorictularia disparilis, one species of Oxyuroidea, and two species of Trichostrongyloidea.
Concurrent infection with M. brygooi and S. goldmanae was positively correlated, and prevalence and intensity of both species increased with host size, in Pogona minor mitchelli. Prevalence and intensity of infection, and species diversity, were highest in the northern, subtropical parts of the State, and lowest in the drier central and southern inland. Cysts containing physalopteran larvae were present in the stomach wall of many hosts; prevalence and intensity of cysts was highest in the northern area.
Six species of nematode in the genus Abbreviata were recovered from the stomachs of 58 Varanus
gouldii, s.l., in Western Australia: A. hastaspicula, A. barrowi, A, antarctica, A. levicauda, sp. nov.,
A. tumidocapitis, sp. nov., and an unnamed species. A. occidentalis Jones, 1978 is reduced to
synonomy with A. antarctica (Linstow, 1899). A, hastaspicula was recovered from all hosts examined
except those from the south-west of the State, where it was replaced by A. antarctica. A. levicauda
and A. tumidocapitis occurred concurrently with one or both of the above species. Th'e increase in
A. hastaspicula numbers with host size in V. gouldii, s.s., (P<0,05) and in V. panoptes (P<0,05)
indicates that there is no effective host immune response. A. hastaspicula numbers were unaffected
by concurrent A. levicauda infection. There was a positive correlation between numbers of Abbreviata
sp. larvae and A. hastaspicula (P<0.01), and between Abbreviata sp. larvae and A. antarctica (P<0.01),
in V. gouldii, s.s. No larvae were seen in the stomach wall of these Varanus, and it is concluded that
those which occur commonly in this situation in elapid snakes are probably larvae of A. hastaspicula
or A. levicauda, which appear to be unable to mature in these hosts.
Four new species of Abbreviata (Physalopteridae) are reported from Western Australian snakes, viz. Abbreviata barrowi, sp. nov., Abbreviata occidentalis, sp. nov., Abbreviata kumarinae, sp. nov., and Abbreviata aechmespiculum, sp, nov. Larval Abbreviata not identifiable to species were found in almost half the snakes examined. These were almost absent from the south-west part of Western Australia and were most prevalent in the north of the state. Infections could not be related to season, or to food residues in the hosts. It is suggested that these larvae were unable to mature in the snakes, which were acting as paratenic hosts, and that the most likely definitive hosts were Varanus lizards. A key to the Abbreviata species from Australian and Papua New Guinea reptiles is provided.
The taxonomy of the species of Aponomma and Amblyomma listed by Roberts (1953) from Australia has been examined. Ap. trachysauri (Lucas) is now considered synonymous with Ap. hydrosauri (Denny) and the species previously determined as Ap. hydrosauri is now Ap. concolor Neumann. Other synonymy noted includes Ap. tropicum Roberts with Ap. concolor, Ap. simplex Cooper & Robinson, and Ap. ecinctum Neumann with Ap. jimbriatum (C. L. Koch), Ap. decorosum (L. Koch) with Ap. undatum (Fabricius), and Amblyomma sternae Roberts with Amb. loculosum Neumann. Further information is given on the host range and geographical distribution of the species of both genera, and the nymphs of Amb. moreliae (L. Koch) and Amb. loculosum are described.
A study has been made of the Australian species of Aponomma and
Amblyomma (Ixodoidea).
Nine species of Aponomma were determined, namely A. trachysauri,
A. hydrosauri, A. auruginans, A. decorosum, A. simplex, A. trimuculatum, A.
tachyglossi, A, tropicum, and A. pulchrum, the last three species being new.
Two previously described species, namely A. quadratum and A. ecinctum, were
recognized among the material available for study. A detailed description
given of each species together with essential figures. Keys to the males,
females, and nymphs are included.
Twelve species of Amblyomma were seen. Species previously described
included A. moreliae, A. limbatum, A. albolimbatum, A. triguttatum, A. australiense,
and A. papuanu. A. postoculatum and A. helvolum were not recognized
among the material available for study. A. papuana is recorded from Australia for
the first time. Four new species, namely A. sternne, A. echidnae, A. macropi,
and A. moyi, are described. Keys to the males and females are given.