Interspecific interactions tested: two species of malarial parasite in a West African lizard

Plasmodium giganteum and P. agamae, parasites of the rainbow lizard, Agama agama, in West Africa were studied to determine the nature of any interspecific interactions between the two malaria species. The plasmodia are distributed in A. agama throughout the mesic zone of Africa; P. agamae is sometimes found as a solitary malaria species in populations of the lizard, but P. gigateum has not been found alone. In 3170 lizards from Sierra Leone the prevalence of lizard malaria at 22 sites varied considerably (8–90% of lizards were infected), but the ratio of the two species was similar among sites (52–91% P. agamae). Larger lizards were more often infected. Mixed infections occurred 2–5 times more often than expected by chance. Parasite density within individual hosts, or parasitemia, was similar for each species when alone or in mixed infection. Natural infections followed in laboratory lizards stayed at constant levels for as long as 211 days. The two species use different classes of host cells (P. giganteum in immature cells and P. agamae in mature erythrocytes) and may have different periods of peak transmission. Analysis of the data does not support a neutral relationship between P. giganteum and P. agamae, nor ongoing competition for resources or heterologous immunity. The data best support facilitation in which P. agamae alters the host in a way that allows more successful establishment of P. giganteum.     

Experimental test for premunition in a lizard malaria parasite (Plasmodium mexicanum)

Premunition in Plasmodium spp. is the prevention of superinfection by novel genotypes entering an already established infection in a vertebrate host. Evidence for premunition was sought for the lizard malaria parasite, P. mexicanum, in its natural host, the fence lizard, Sceloporus occidentalis. Clonal diversity (= alleles for the haploid parasite) was determined with the use of 3 microsatellite markers. Both naturally infected lizards (N = 25) and previously noninfected lizards (N = 78) were inoculated intraperitoneally (IP) with blood from donor infections and followed over a 3-mo period. Compared to the success of clonal establishment in all the naive lizards (78/78 successful), clones entering preexisting infections had a significant disadvantage (9/25 successful). The number of preexisting clones (1-2 vs. 3-4) within recipient infections had no effect on the success of superinfection. Infections that excluded entering novel clones did not have higher initial asexual parasitemia, but had a higher initial density of gametocytes, suggesting they were older. Infections allowing superinfection experienced a higher final parasitemia.     

Tree-based delimitation of morphologically ambiguous taxa: a study of the lizard malaria parasites on the Caribbean island of Hispaniola

Malaria parasites in the genus Plasmodium have been classified primarily on the basis of differences in morphology. These single-celled organisms often lack distinguishing morphological features, and this can encumber both species delimitation and identification. Six saurian malaria parasites have been described from the Caribbean island of Hispaniola. All six infect lizards in the genus Anolis, but only two of these parasites can be distinguished using morphology. The remaining four species overlap in morphology and geography, and cannot be consistently identified using traditional methods. We compared a morphological approach with a molecular phylogenetic approach for assessing the taxonomy of these parasites. We surveyed for blood parasites from 677 Anolis lizards, representing 26 Anolis spp. from a total of 52 sites across Hispaniola. Fifty-five of these lizards were infected with Plasmodium spp., representing several new host records, but only 24 of these infections could be matched to previously described species using traditional morphological criteria. We then estimated the phylogeny of these parasites using both mitochondrial (cytb and coxI) and nuclear (EF2) genes, and included carefully selected GenBank sequences to confirm identities for certain species. Our molecular results unambiguously corroborated our morphology-based species identifications for only the two species previously judged to be morphologically distinctive. The remaining infections fell into two well-supported and reciprocally monophyletic clades, which contained the morphological variation previously reported for all four of the morphologically ambiguous species. One of these clades was identified as Plasmodium floridense and the other as Plasmodium fairchildi hispaniolae. We elevate the latter to Plasmodium hispaniolae comb. nov. because it is polyphyletic with the mainland species Plasmodium fairchildifairchildi and we contribute additional morphological and molecular characters for future species delimitation. Our phylogenetic hypotheses indicate that two currently recognised taxa, Plasmodium minasense anolisi and Plasmodium tropiduri caribbense, are not valid on Hispaniola. These results illustrate that molecular data can improve taxonomic hypotheses in Plasmodium when reliable morphological characters are lacking.     

Detection of a malaria parasite (Plasmodium mexicanum) in ectoparasites (mites and ticks), and possible significance for transmission

Two species of sandflies (Lutzomyia) are competent vectors of Plasmodium mexicanum, a malaria parasite of lizards. The very patchy distribution of sites with high P. mexicanum prevalence in the lizards, and often low or even nil sandfly density at such sites, provoked an evaluation of 2 common lizard ectoparasites, the tick Ixodes pacificus and the mite Geckobiella occidentalis, as potential passive vectors. Plasmodium sp.-specific polymerase chain primers were used to amplify a long segment of the mitochondrial cytochrome b gene that is unlikely to survive intact if the parasite cells are killed within a blood-feeding arthropod. The segment was strongly amplified from sandflies (the positive control for the method) from 1 to 96 hr postfeeding on an infected lizard. For ticks, the gene fragment was poorly amplified at 0 hr postfeed, and not amplified after 2 hr. In contrast, strong amplification of the parasite DNA was observed from mites from 0 to 20 hr postfeed, and weak amplification even at 96 hr.     

Investigations on the Host Specificity of Dihomoxenous Sarcosporidia in the Intermediate and Definitive Host

ABSTRACT. Cross-transmission experiments were performed in order to determine the host specificity in the intermediate and definitive hosts of the four described dihomoxenous Sarcocystis species, S. gallotiae, S. stehlinii, S. simonyi , and S. dugesii from lacertid lizards of the genera Gallotia and Podarcis from the Macaronesian Islands. Sarcocysts of either species from experimentally infected lizards were fed to a variety of laboratory-bred lizard species of the genera Gallotia, Lacerta , and Podarcis . These sarcocysts proved to be infectious to all examined animals, showing no definitive host specificity in the tested genera. Lizards of the genera Chalcides and Tarentola , however, were not susceptible definitive hosts for S. gallotiae . The inoculation of experimentally obtained sporocysts of each of the four Sarcocystis species to various lacertid lizard species revealed varying degrees of intermediate host specificity, generally demonstrating each native host to be the most susceptible.     

Some Parasitic Protozoa from the Gambia

ABSTRACT. A new species of Eimeria from the fat-tailed gecko Hemidactylus brookei in Gambia, West Africa, was described and named E. helenae in honor of Mrs. Helen Levine. The oocysts averaged 22.2 μm and each contained four sporocysts (8.0 × 6.9 μ m) with two sporozoites per sporocyst. No schizogony or gametogony was discovered in the intestine, suggesting that these stages may occur in the liver or bile cannuli. The oocysts of an adeleid parasite of the insect prey of the centipede Scolopendrium morsitans were described. Plasmodium agamae, an eimeriid hemogregarine, Pirhaemocyton, and a Shellackia-type parasite were found in the blood of agamid lizards. The fruit bat Epomorphorus gambianus was commonly and heavily infected with Hepatocystis epomorphori.     

Some Blood Sporozoans from East African Reptiles*

SYNOPSIS. Six hundred and forty-one lizards belonging to 28 species, and 29 snakes belonging to 12 species from East Africa were examined for blood sporozoans. Eight species of lizards and 4 of snakes were positive. Tissue phases were seen in some infections; no proven arthropod vectors were found. Parasites are described from previously unreported hosts; new host records, and new stages in the life histories of previously named parasites are reported. The sporozoans belong to the genera Plasmodium, Haemoproteus, Haemogregarina or Hepatozoon, and probably Pirhemocyton. Reasons are given for the inadvisability of establishing new species of some of these on the basis of blood stages alone.     

Schellackia occidentalis n.sp., a Blood-inhabiting Coccidian Found in Lizards in Southern California

SUMMARY. Schellackia occidentalis n. sp., is described from the following lizards from southern California: Sceloporus occidentalis becki, S. o. biseriatus , and Uta stansburiana hesperis. Evidence is presented to show that lizards become infected by ingestion of the lizard mite Geckobiella texana. The mite acts as a passive vector by swallowing infected erythrocytes. After ingestion of the mites carrying parasitized red cells, the lizard is infected by migration of the sporozoites into the lizard's intestinal epithelial cells. Schizogony and sporogony occur in the intestinal wall of the lizard. Sporozoites appear in the peripheral blood from 30 to 45 days after ingestion of infected mites. This is the first species of the genus Schellackia to be described in the Western Hemisphere.     

Parasites in a biodiversity hotspot: a survey of hematozoa and a molecular phylogenetic analysis of Plasmodium in New Guinea skinks

A sample of 204 skinks (Squamata: Scincidae) from 10 genera representing 24 species were collected from 10 different localities in New Guinea and examined for blood parasites. Hemogregarines, trypanosomes, microfilarial worms, and 8 infections showing 2 distinct morphological types of malaria parasites (Plasmodium sp.) were observed. Molecular sequence data, in the form of mitochondrial cytochrome b sequences from the Plasmodium infections, showed 2 distinct clades of parasites, 1 in Sphenomorphus jobiense hosts and 1 in Emoia spp., which correspond to the 2 morphotypes. There was substantial genetic variation between the 2 clades, as well as within the clade of Emoia parasites. Nearly half of the skinks sampled had green blood pigmentation, resulting from the presence of biliverdin in the plasma; however, only 1 of these lizards was infected with Plasmodium sp. and only 2 had any blood parasites. These preliminary results suggest a high degree of phylogenetic diversity but a very low prevalence of Plasmodium spp. infections in the skinks of this globally important biodiversity hot spot.     

Clonal diversity within infections and the virulence of a malaria parasite, Plasmodium mexicanum

Both verbal and mathematical models of parasite virulence predict that genetic diversity of microparasite infections will influence the level of costs suffered by the host. We tested this idea by manipulating the number of co-existing clones of Plasmodium mexicanum in its natural vertebrate host, the fence lizard Sceloporus occidentalis. We established replicate infections of P. mexicanum made up of 1, 2, 3, or >3 clones (scored using 3 microsatellite loci) to observe the influence of clone number on several measures of parasite virulence. Clonal diversity did not affect body growth or production of immature erythrocytes. Blood haemoglobin concentration was highest for the most genetically complex infections (equal to that of non-infected lizards), and blood glucose levels and rate of blood clotting was highest for the most diverse infections (with greater glucose and more rapid clotting than non-infected animals). Neither specific clones nor parasitaemia were associated with virulence. In this first experiment that manipulated the clonal diversity of a natural Plasmodium-host system, the cost of infection with 1 or 2 clones of P. mexicanum was similar to that previously reported for infected lizards, but the most complex infections had either no cost or could be beneficial for the host.     

Molecular phylogeography and systematics of the arid-zone members of the Egernia whitii (Lacertilia: Scincidae) species group

We assembled a molecular phylogeny for the arid-zone members of the Egernia whitii species group to test Pianka's [Zoogeography and speciation of Australian desert lizards: an ecological perspective, Copeia (1972) 127-145] hypothesis that habitat specificity to the three major arid-zone vegetation communities is the primary cause of lizard speciation within the arid interior of Australia. This hypothesis predicts that species should exhibit phylogeographic structuring concordant with the major arid-zone vegetation types. Sequence data were obtained from four of the five arid-zone members of the E. whitii species group, and from across the ranges of the ecologically generalized E. inornata and E. multiscutata and the more specialized E. striata. We targeted a fragment (696 base pair (bp)) of the mitochondrial genome comprising the 3' half of the ND4 gene. We analysed the data using parsimony, maximum likelihood and Bayesian methods. Our phylogeny confirms the monophyly of the arid-zone members of the species group, although the phylogenetic relationships among species were not fully resolved. Although our topology does not support the recognition of the existing subspecies within E. multiscutata, there is a substantial phylogeographic break between South Australian/Victorian (Clade 1) and Western Australian (Clade 2) populations. We found considerable phylogeographic structure within E. inornata, with six major clades identified. However, these clades were not concordant with the distribution of habitat types in the arid-zone. Phylogeographic structure was also observed in the more specialized E. striata, although our analysis revealed close phylogenetic affinities between the sympatric species E. striata and E. kintorei. Shimodaira-Hasegawa topology tests were equivocal in regard to whether the phylogeographic structure within E. striata was in accordance with Pianka's predictions. Although our data failed to provide strong support for the suggestion that ecological and habitat factors are responsible for the diversification of arid-zone lizards, most E. inornata and E. striata populations had similar habitats, indicating that adaptation to particular habitats may have some role in the speciation of lizards in the Australian arid-zone.     

Natural and experimental infection of the lizard Ameiva ameiva with Hemolivia stellata (Adeleina: Haemogregarinidae) of the toad Bufo marinus

Developmental stages of a haemogregarine in erythrocytes of the lizard Ameiva ameiva (Teiidae), from Pará State, north Brazil, were shown to be those of Hemolivia by the nature of the parasite's sporogonic cycle in the tick Amblyomma rotondatum. The type species, Hemolivia stellata Petit et al., 1990 was described in the giant toad Bufo marinus and the tick Amblyomma rotondatum, also from Pará State, and in view of the fact that A. ameiva and Bufo marinus share the same habitat and are both commonly infested by A. rotondatum, the possibility that the parasite of A. ameiva is H. stellata had to be considered. Uninfected lizards fed with material from infected ticks taken from B. marinus, and others fed with liver of toads containing tissue-cysts of H. stellata, were shown to subsequently develop typical Hemolivia infections, with all stages of the development similar to those seen in the naturally infected lizards. Conversely, a juvenile, uninfected toad became infected when fed with sporocysts of Hemolivia in a macerated tick that had fed on an infected A. ameiva and pieces of liver containing tissuecysts from the same lizard. The remarkable lack of host specificity shown by H. stellata, in hosts so widely separated as an amphibian and a reptile, is discussed.     

Clonal diversity of a lizard malaria parasite, Plasmodium mexicanum, in its vertebrate host, the western fence lizard: role of variation in transmission intensity over time and space

Within the vertebrate host, infections of a malaria parasite (Plasmodium) could include a single genotype of cells (single-clone infections) or two to several genotypes (multiclone infections). Clonal diversity of infection plays an important role in the biology of the parasite, including its life history, virulence, and transmission. We determined the clonal diversity of Plasmodium mexicanum, a lizard malaria parasite at a study region in northern California, using variable microsatellite markers, the first such study for any malaria parasite of lizards or birds (the most common hosts for Plasmodium species). Multiclonal infections are common (50-88% of infections among samples), and measures of genetic diversity for the metapopulation (expected heterozygosity, number of alleles per locus, allele length variation, and effective population size) all indicated a substantial overall genetic diversity. Comparing years with high prevalence (1996-1998 = 25-32% lizards infected), and years with low prevalence (2001-2005 = 6-12%) found fewer alleles in samples taken from the low-prevalence years, but no reduction in overall diversity (H = 0.64-0.90 among loci). In most cases, rare alleles appeared to be lost as prevalence declined. For sites chronically experiencing low transmission intensity (prevalence approximately 1%), overall diversity was also high (H = 0.79-0.91), but there were fewer multiclonal infections. Theory predicts an apparent excess in expected heterozygosity follows a genetic bottleneck. Evidence for such a distortion in genetic diversity was observed after the drop in parasite prevalence under the infinite alleles mutation model but not for the stepwise mutation model. The results are similar to those reported for the human malaria parasite, Plasmodium falciparum, worldwide, and support the conclusion that malaria parasites maintain high genetic diversity in host populations despite the potential for loss in alleles during the transmission cycle or during periods/locations when transmission intensity is low.     

海南岛蜥蜴类多样性

经过多年调查,共得海南岛蜥蜴类动物标本238号,隶属5科16属22种。综合文献记录,海南岛实有蜥蜴类动物8科19属28种,约占全国总数的17％,多于福建,与广东省（含香港）相当,略少于台湾和广西。海南蜥蜴类均为东洋界物种,物种多样性较高,但特有种较少。     

Microsatellite DNA markers for three toad-headed lizard species (Phrynocephalus vlangalii, P. przewalskii and P. guttatus)

To assess the impact of natural landscapes on the population structure of lizards, 10 polymorphic microsatellite DNA markers were developed for the Qinghai toad-headed lizard, Phrynocephalus vlangalii. The number of alleles at these informative loci ranged from four to 28. The novel markers and those previously developed for Phrynocephalus przewalskii were cross-tested among three toad-headed lizard species P. vlangalii, P. przewalskii and P. guttatus. A high cross-utility rate of more than 58% was observed among these three species. These markers are expected to be useful tools for taxonomic considerations as well as population genetic analysis and future conservation management.     

Clonal diversity of a malaria parasite, Plasmodium mexicanum, and its transmission success from its vertebrate-to-insect host

Infections of the lizard malaria parasite Plasmodium mexicanum are often genetically complex within their fence lizard host (Sceloporus occidentalis) harbouring two or more clones of parasite. The role of clonal diversity in transmission success was studied for P. mexicanum by feeding its sandfly vectors (Lutzomyia vexator and Lutzomyia stewarti) on experimentally infected lizards. Experimental infections consisted of one, two, three or more clones, assessed using three microsatellite markers. After 5 days, vectors were dissected to assess infection status, oocyst burden and genetic composition of the oocysts. A high proportion (92%) of sandflies became infected and carried high oocyst burdens (mean of 56 oocysts) with no influence of clonal diversity on these two measures of transmission success. Gametocytemia was positively correlated with transmission success and the more common vector (L. vexator) developed more oocysts on midguts. A high proportion (74%) of all alleles detected in the lizard blood was found in infected vectors. The relative proportion of clones within mixed infections, determined by peak heights on pherograms produced by the genetic analyser instrument, was very similar for the lizard’s blood and infections in the vectors. These results demonstrate that P. mexicanum achieves high transmission success, with most clones making the transition from vertebrate-to-insect host, and thus explains in part the high genetic diversity of the parasite among all hosts at the study site.     

A New Malaria Parasite Plasmodium (Sauramoeba) heischi in Skinks (Mabuya striata) from Nairobi, with a Brief Discussion of the Distribution of Malaria Parasites in the Family Scincidae

ABSTRACT. A new species of malaria parasite, Plasmodium (Sauramoeba) heischi , is described from African skinks (Mabuya striata). Eleven individuals of 90 specimens collected in Nairobi were found to be infected. The new parasite is a large species, characterized by spindle-shaped gametocytes, the female often with a subterminal nucleus. The schizonts produce up to 65 nuclei and cause great hypertrophy and distortion of the host cell. Although similar to P. (Sauramoeba) giganteum in dimensions and merozoite numbers, P. heischi is easily distinguished by gametocyte and schizont shapes.     

Gastrointestinal helminths of the lizard Chalcides ocellatus from Benghazi, Libya

Chalcides ocellatus, a scincid lizard, sampled during October 1998 to December 1999 from Benina (farmland) and Al-Kueffia (a rocky area) in Benghazi, Libya, was found to harbour three intestinal nematodes, Pharyngodon mamillatus, Thelandros alatus and Parapharyngodon micipsae, and an intestinal cestode, Oochoristica tuberculata. Thelandros alatus, P. micipsae and O. tuberculata were recorded for the first time in C. ocellatus. Parapharyngodon micipsae was detected in C. ocellatus from Benina and O. tuberculata from lizards in Al-Kueffia. The majority (87.6%) of C. ocellatus were infected with helminth parasites and the levels of infection were higher in males than in females but this difference was not significant. Pharyngodon mamillatus recorded the highest number of nematode parasites in C. ocellatus, although there was no relationship between the number of nematode parasites recovered and host density. In lizards infected with the cestode O. tuberculata, males had shorter snout-vent lengths than females. From a total of 153 C. ocellatus, 120 (78.4%) showed single and 14 (9.2%) showed mixed parasitic infections. Mixed infections between different species of nematodes were not observed.