Arthonia epipolytropa Hafellner & Grube and Arthonia subclemens Hafellner, Grube & Muggia are described as new to science. Both are specific parasites of Lecanora polytropa s. lat., but of differing pathogenicity and of very different appearance. Whereas the clearly parasitic Arthonia epipolytropa with its agglomerated ascomata is presently known with certainty from a number of localities along the arch of the Alps (Austria, Italy, Switzerland), other parts of Europe (Norway, Albania) and northern America (USA), the less harmful A. subclemens with its isolated sunken ascomata is currently known only from a small number of localities in the Eastern Alps (Austria, Italy) and various mountain ranges in southern Europe (Spain, North Macedonia, Greece). The species are compared with other Arthonia species known from Lecanora or one of its recently segregated genera. A key to the fungi regularly found on Lecanora polytropa s. lat. is presented.

The taxonomy of species of Bivesicula Yamaguti, 1934 is analysed for samples from holocentrid, muraenid and serranid fishes from Japan, Ningaloo Reef (Western Australia), the Great Barrier Reef (Queensland), New Caledonia and French Polynesia. Analysis of three genetic markers (cox1 mtDNA, ITS2 and 28S rDNA) identifies three strongly supported clades of species and suggests that Bivesicula as presently recognized is not monophyletic. On the basis of combined morphological, molecular and biological data, 10 species are distinguished of which five are proposed as new. Bivesicula Clade 1 comprises seven species of which three are effectively morphologically cryptic relative to each other; all seven infect serranids and four also infect holocentrids. Bivesicula Clade 2 comprises three species of which two are effectively morphologically cryptic relative to each other; all three infect serranids and one also infects a muraenid. Bivesicula Clade 3 comprises two known species from apogonids and a pomacentrid, and forms a clade with species of Paucivitellosus Coil, Reid & Kuntz, 1965 to the exclusion of other Bivesicula species. Taxonomy in this genus is made challenging by the combination of low resolving power of ribosomal markers, the existence of regional cox1 mtDNA populations, exceptional and unpredictable host-specificity and geographical distribution, and significant host-induced morphological variation.

Although parasites represent a major component of biodiversity, they remain poorly assessed, especially in remote regions. In this study, we screened 461 reptiles from Socotra, the largest and most biologically diverse archipelago in Arabia. Using 18S rRNA primers, we detected various apicomplexan parasites, namely haemogregarines, sarcocystids and eimeriids. Haemogregarines were the most common and genetically diverse, followed by sarcocystids (genus Sarcocystis) and eimeriids (genera Isospora and Lankesterella). All were related to parasites of other reptiles, including species from Arabia, Northern Africa and Asia. Like their 29 endemic reptile hosts, almost all Socotran parasites presented high genetic divergence and ecological differences from those found elsewhere, and probably represent undescribed endemic species. Among hosts, skinks were the most parasitized, which contrasted with similar studies from other areas, probably due to their more generalist diet and habitat use. As expected due to its high species richness, geckos harboured the highest parasite diversity in the archipelago. Parasite diversity also seemed to be correlated to island size, as the largest island harboured most haplotypes. This study emphasizes the importance of screening parasites in wild hosts from remote regions and of considering host ecology to understand disease transmission across taxa.

Acanthocephalans are parasites with complex lifecycles that are important components of aquatic systems and are often model species for parasite-mediated host manipulation. Genetic characterization has recently resurrected Pomphorhynchus tereticollis as a distinct species from Pomphorhynchus laevis, with potential implications for fisheries management and host manipulation research. Morphological and molecular examinations of parasites from 7 English rivers across 9 fish species revealed that P. tereticollis was the only Pomphorhynchus parasite present in Britain, rather than P. laevis as previously recorded. Molecular analyses included two non-overlapping regions of the mitochondrial gene – cytochrome oxidase and generated 62 sequences for the shorter fragment (295 bp) and 74 for the larger fragment (583 bp). These were combined with 61 and 13 sequences respectively, from Genbank. A phylogenetic analysis using the two genetic regions and all the DNA sequences available for P. tereticollis identified two distinct genetic lineages in Britain. One lineage, possibly associated with cold water tolerant fish, potentially spread to the northern parts of Britain from the Baltic region via a northern route across the estuarine area of what is now the North Sea during the last Glaciation. The other lineage, associated with temperate freshwater fish, may have arrived later via the Rhine/Thames fluvial connection during the last glaciation or early Holocene when sea levels were low. These results raise important questions on this generalist parasite and its variously environmentally adapted hosts, and especially in relation to the consequences for parasite vicariance.

The epicontinental fauna of the Iberian Peninsula is strongly influenced by its geographical history. As the possibilities for dispersion of organisms into and from this region were (and still are) limited, the local fauna consists almost exclusively of endemic species. Almost all Iberian freshwater fishes of the families Leuciscidae and Cyprinidae are endemic and on-going research on these taxa continually uncovers new species. Nevertheless, information on their host-specific parasites remains scarce. In this study, we investigate the diversity and phylogenetic relationships in monogeneans of the genus Dactylogyrus (gill ectoparasites specific to cyprinoid fish) in the Iberian Peninsula. Twenty-two species were collected and identified from 19 host species belonging to Cyprinidae and Leuciscidae. A high degree of endemism was observed, with 21 Dactylogyrus species reported from Iberia only and a single species, D. borealis, also reported from other European regions. Phylogenetic analysis split the endemic Iberian Dactylogyrus into two well-supported clades, the first encompassing Dactylogyrus parasitizing endemic Luciobarbus spp. only, and the second including all Dactylogyrus species of endemic leuciscids and four species of endemic cyprinids. Species delimitation analysis suggests a remarkable diversity and existence of a multitude of cryptic Dactylogyrus species parasitizing endemic leuciscids (Squalius spp. and representatives of Chondrostoma s.l.). These results suggest a rapid adaptive radiation of Dactylogyrus in this geographically isolated region, closely associated with their cyprinoid hosts. Moreover, phylogenetic analysis supports that Dactylogyrus parasites colonized the Iberian Peninsula through multiple dispersion events.

This study aimed to evaluate the simultaneous infections of Haemonchus contortus and Haemonchus placei in sheep, as well as the production of hybrids. A parental group of lambs (n = 6) were mix-infected with 2000 infective larvae (L3) of H. placei and 2000 L3 of H. contortus. Faecal samples were taken from each of these six lambs to produce the first generation of L3 (F1-L3) in individual cultures. These F1-L3 were used to infect 12 lambs; six of them were euthanized at 42 days (Group F1-42) and six at 84 days (Group F1-84) post infection. Polymerase chain reaction (PCR) analysis, using species-specific primer pairs, was the gold standard method for identification of Haemonchus adult species and hybrids. The establishment rate of both species was similar in the parental group: 51.7% H. contortus and 48.3% H. placei. Of the 219 adult specimens from groups F1-42 and F1-84 analysed by PCR, eight (3.65%) were hybrids, 111 were H. contortus and 100 were H. placei. The morphological evaluation of the F1-L3 from the parental group showed a predominance of larvae with H. contortus size (51.5%) in comparison with H. placei (42.8%). In the second generation of L3 (F2-L3) produced by the F1-lambs, larvae with H. contortus morphology predominated, with 81.5% in the F1-42 group and 84.0% in the F1-84 group. In conclusion, an artificial mixed infection by H. contortus and H. placei was established in lambs and resulted in the production of a small number of hybrids among their offspring.

The effect of repeated inoculations of the rust Puccinia cardui-pycnocephali Sydow (Uredinae) on growing rosettes of Mediterranean specimens of slenderflower thistle (Carduus tenuiflorus Curt. ♯3 CRUTE) and Italian thistle (Carduus pycnocephalus L. ♯ CRUPY), and Australian specimens of Italian thistle was investigated, using a Mediterranean strain of the rust collected mainly on Italian thistle. Growth of slenderflower thistle was not affected, but growth of both specimens of Italian thistle was decreased significantly when inoculated with the rust. This decrease was significantly higher on Australian specimens.

We explored the distribution of Cardicola chaetodontis in chaetodontid fishes from the Great Barrier Reef. We found just four infections of adult worms in 238 individuals of 26 chaetodontid species. By contrast, eggs were present in hearts of 75 fishes (31·5%) and 19 of 26 chaetodontid species (all Chaetodon species). In 10 cases eggs contained moving miracidia; all the others were dead and degenerating. Eggs were sought in the gills of 51 individual fish. There were 17 cases of eggs being present in gills while present in the heart, but also 13 cases where eggs were absent from gills but present in the heart, suggesting that eggs remain longer in heart tissue than in gills. ITS2 rDNA sequences from two adult worms and eggs extracted from gills of five fishes (all different species) were identical to previously reported sequences of C. chaetodontis except for a single base-pair difference in two samples. We conclude that aporocotylid eggs trapped in fish heart tissues may inform understanding of the distributions and host ranges of aporocotylids, especially where adult prevalence is low. The low host-specificity of C. chaetodontis contrasts with higher specificity of trematodes of chaetodontids that have trophic transmission.

The evolution of symbiotic relationships involving reef corals has had much impact on tropical marine biodiversity. Because of their endosymbiotic algae (zooxanthellae) corals can grow fast in tropical shallow seas where they form reefs that supply food, substrate and shelter for other organisms. Many coral symbionts are host-specific, depending on particular coral species for their existence. Some of these animals have become popular objects for underwater photographers and aquarists, whereas others are hardly noticed or considered pests. Loss of a single coral host species also leads to the disappearance of some of its associated fauna. In the present study we show which mushroom corals (Scleractinia: Fungiidae) are known to act as hosts for other organisms, such as acoel flatworms, copepods, barnacles, gall crabs, pontoniine shrimps, mytilid bivalves, epitoniid snails, coralliophilid snails, fish and certain types of zooxanthellae. Several of these associated organisms appear to be host-specific whereas other species are generalists and not even necessarily restricted to fungiid hosts. Heliofungia actiniformis is one of the most hospitable coral species known with a recorded associated fauna consisting of at least 23 species. The availability of a phylogeny reconstruction of the Fungiidae enables comparisons of closely related species of mushroom corals regarding their associated fauna. Application of a phylogenetic ecological analysis indicates that the presence or absence of associated organisms is evolutionarily derived or habitat-induced. Some associations appear to be restricted to certain evolutionary lineages within the Fungiidae, whereas the absence of associated species may be determined by ecomorphological traits of the host corals, such as coral dimensions (coral diameter and thickness) and polyp shape (tentacle size).

This review deals with the problems faced by those monogenean (platyhelminth) parasites that attach themselves to fish skin. The structure of the skin and the ways in which the posterior hook-bearing haptor achieves virtually permanent attachment to the skin are considered. Small marginal hooklets are specialized for attachment to superficial host epidermal cells, finding anchorage in the terminal web of keratinous tonofilaments, while large hooks (hamuli) may penetrate into and lodge in the collagenous dermis. The complementary roles of suction and sticky secretions in haptor attachment and the role of the pharynx in temporary attachment during feeding are also considered. During leech-like locomotion the haptor is briefly detached and, at this critical time, the anterior end is strongly fixed to the wet, current-swept and possibly slimy skin by a sticky secretion. This secretion is deployed on paired pads or discs, the latter sometimes backed up by suction. After attachment by the haptor is re-established, the special tegument covering the anterior adhesive areas may be instrumental in their instant release. The role of fish skin in the phenomenon of host specificity and in the generation of a defensive response against monogeneans is considered and site-specificity of parasites on the host's body is discussed. Possible selection pressures exerted by predatory ‘cleaner’ organisms are briefly evaluated.

Little is known regarding the diversity, distribution or host-parasite associations of Trypanosoma spp. in Australian wildlife. Here we report on an investigation based on divergence of the 18S rRNA gene of trypanosomes isolated from a range of hosts and varied geographical locations. A total of 371 individuals representing 19 species of native animals from 14 different locations were screened. In total, 32 individuals from 9 different species tested positive for the parasite. Phylogenetic analysis revealed considerable parasite diversity with no clear geographical distribution and no evidence of host specificity. In general, it appears that Australian Trypanosoma spp. are widespread, with several genotypes appearing in multiple host species and in varied locations including both mainland areas and offshore islands. Some host species were found to be susceptible to multiple genotypes, but no individuals were infected with more than a single isolate.

We report 21 thelastomatoid species parasitizing 31 described and 5 undescribed geoscapheine and panesthiine cockroaches, representing all but 1 of the known species of these subfamilies in Australia. The nematodes have 3 distinct patterns of host distribution: dominant, moderate and rare. The 4 dominant species, Cordonicola gibsoni, Leidynemella fusiformis, Travassosinema jaidenae and Aoruroides queenslandensis, are highly prevalent, found in nearly all host species examined, and broadly distributed. The 8 moderate species have lower prevalences but are still widely distributed. Many of these species are more common in one host subfamily than the other. The remaining 9 rare species have highly restricted host and geographical distributions. Six of the 21 species are exclusive to geoscapheines, 5 to panesthiines and 10 are shared. These patterns suggest that most of the reported thelastomatoid species are generalists rather than specialists, that host-specificity within this group is low and that co-evolutionary speciation has had little, if any, impact on structuring the thelastomatoid fauna of Australian burrowing cockroaches. In a broader context, this study provides the first comprehensive examination of the role of coevolutionary speciation and host specificity in regulating the distribution of pinworms in arthropods.

Species of Protopolystoma are monogenean flukes that only infect allopolyploid hosts in the anuran genus Xenopus. Multivariate analyses of morphometric sclerite characters in the nominal species Protopolystoma simplicis suggest that morphologically distinguishable populations occur in the tetraploid host, Xenopus laevis victorianus, and in each of the octoploid hosts, X. vestitus and X. wittei. The species-level divergence of a lineage specific to X. laevis is supported by sequence variation in the mitochondrial cytochrome c oxidase subunit 1 (cox1) gene. Protopolystoma simplicis from X. laevis is redesignated P. microsclera n. sp., with P. simplicis being retained for populations in octoploid hosts. This division is consistent with large differences in egg hatching schedule, fixed differences at the mannose-6-phosphate isomerase and fumarate hydratase loci, and host-specificity in experimental analyses. Although the respective P. simplicis populations in X. vestitus and X. wittei also show significant diversity in allozyme expression, morphometrics and egg hatching schedule, they are retained in the same species because their level of mitochondrial DNA divergence is similar to that found within other Protopolystoma species. The consequences of splitting P. simplicis for a recent interpretation of the origin of Protopolystoma faunas in octoploid Xenopus spp. is discussed.

In order to ascertain the extent of possible host-specialization in the Nesolechia oxyspora complex, as a pilot study ascospores from 20 collections from different parmelioid hosts representing seven genera were drawn, measured, and had length:breadth ratios calculated. The data were then subjected to multiple regression analysis using Huber-White sandwich estimators of standard errors (apparently not previously used in mycology) which take account of spores not necessarily being independent variables as they might come from the same ascus, and a statistical analysis. Significant differences between collections from seven genera were found. While the sample size was too small to reach definite conclusions, it is clear that there is a finer degree of host-relatedness than hitherto expected, which may be geno- or phenotypic. A more extensive study including species from a wider range of hosts and complemented by molecular methods will be necessary to further elucidate degrees of specificity and cryptic co-speciation in the complex. A list of the 63 reported lichen hosts is included; these are distributed though 19 genera.

Groupers (Epinephelinae) are prominent marine fishes distributed in the warmer waters of the world. Review of the literature suggests that trematodes are known from only 62 of the 159 species and only 9 of 15 genera; nearly 90% of host–parasite combinations have been reported only once or twice. All 20 families and all but 7 of 76 genera of trematodes found in epinephelines also occur in non-epinephelines. Only 12 genera of trematodes are reported from both the Atlantic–Eastern Pacific and the Indo–West Pacific. Few (perhaps no) species are credibly cosmopolitan but some have wide distributions across the Indo–West Pacific. The hierarchical ‘relatedness’ of epinephelines as suggested by how they share trematode taxa (families, genera, species) shows little congruence with what is known of their phylogeny. The major determinant of relatedness appears to be geographical proximity. Together these attributes suggest that host-parasite co-evolution has contributed little to the evolution of trematode communities of epinephelines. Instead, they appear to have arisen through localized episodes of host-switching, presumably both into and out of the epinephelines. The Epinephelinae may well be typical of most groups of marine fishes both in the extent to which their trematode parasites are known and in that, apparently, co-evolution has contributed little to the evolution of their communities of trematodes.

The taxonomy and distribution of cephalochlamydid cestodes are reviewed. This group is primarily specific to pipid anurans and occurs naturally across sub-Saharan Africa. Paracephalochlamys gen. nov. has two large lateral testes (sometimes doubled or absent on one side) on the anterior margin of each segment, while Cephalochlamys Blanchard, 1908 has three to 23 small testes scattered in lateral fields. Paracephalochlamys papilionis sp. nov. infects Pseudhymenochirus merlini in Sierra Leone. The distribution of Cephalochlamys species is inferred from the previous literature and numerous new records. Cephalochlamys namaquensis (Cohn, 1906) occurs in Xenopus laevis laevis in Namibia, South Africa, Lesotho and Zimbabwe, X. l. poweri (new host record) in Zambia and the Democratic Republic of Congo (D.R.C.), X. l. victorianus in Kenya, Uganda, Rwanda and D.R.C., X. l. sudanensis (new host record) in Cameroon and Sudan, and the ranid anuran, Rana angolensis, in Zimbabwe. Anthropogenic dispersal of C. namaquensis, together with X. l. laevis, has occurred to localities in the south-western United States and Isle of Wight, U.K. Cephalochlamys compactus sp. nov., differentiated from C. namaquensis by a less well developed median ovarian cavity and more compact vitellarium, occurs in Xenopus muelleri in Togo, Ghana, Nigeria, Cameroon, D.R.C., Zimbabwe and South Africa, X. borealis in Kenya, X. clivii in Ethiopia, R. angolensis in Ethiopia and R. occipitalis in Nigeria. Cephalochlamys representatives of uncertain specific status have been recorded in X. gilli (new host record) in South Africa, X. pygmaeus and X. fraseri-like hosts (new host records) in the D.R.C., X. tropicalis (new host record) in Nigeria and R. occipitalis in Gabon. Despite the ability of some species to infect distantly related amphibians, the distribution of cephalochlamydid taxa amongst their principal hosts, pipids, can be related to the allopolyploid evolution of this anuran family.

Factors constraining the evolution of host-specificity were investigated using a gastrointestinal parasitic nematode, Strongyloides ratti. S. ratti is a natural parasite of rats which can also reproduce, with decreased success, in laboratory mice. Observed host-specificity arose from lower establishment, reduced per capita fecundity and more rapid expulsion of parasites from mice relative to rats. Variation in the efficacy of thymus-dependent immunity between host species (rats and mice) was insufficient to explain the majority of the observed differences in parasite establishment and reproductive success. The role of natural selection in determining host-specificity was addressed using experimental selection followed by reciprocal fitness assays in both host species. Experimental selection failed to modify the host-specificity of S. ratti to any measurable degree, suggesting either a lack of genetic variation for this trait or the involvement of as yet unidentified factors underlying the differences in S. ratti fitness in rats and mice respectively. These results are discussed in relation to competing theoretical models of ecological specialization, host immunology and previous attempts to experimentally alter the host-specificity of parasitic nematodes