Gregarines (Apicomplexa: Eugregarinorida) parasitizing the cave cricket Troglophilus (Orthoptera: Raphidophoridae) in the Slovenian karst

The cave crickets Troglophilus neglectus Krauss, 1879 and T. cavicola (Kollar, 1833) originating from caves in Slovenia were surveyed for gregarines. Two gregarine species were identified. Gregarina troglophili (Golemansky & Lipa, 1991) occurred in both cave cricket species, T. cavicola being reported a new host species. Besides, a new species, Gregarina bernardae sp. n., in­fecting T. neglectus, was identified and described. The two spe­cies often infest the same T. neglectus individuals, but can be well distinguished upon the shape and morphometric indexes of both solitary gregarines and associations. The deutomerite in solitary gamonts of G. troglophili is orbicular to broadly el­liptoid, while in G. bernardae sp. n. it is oblong to dolioform. In associations, the primite deutomerite in G. troglophili is orbicu­lar to broadly elliptoid, while in G. bernardae sp. n. it is shal­lowly oblong to oblong. In contrast to broadly obovoid to finely obdeltoid satellite deutomerite in G. troglophili, it is narrowly dolioform or dolioform to narrowly obdeltoid in G. bernardae sp. n. Both species are new to the faunal list of Slovenia, and to the list of cave-dwelling species in the country. We direct the attention to the parasite diversity of cave-dwelling animals – a promising, but understudied topic that might considerably contribute to the diversity of the subterranean fauna.

Reorganizing parasitic Delesseriaceae: taxonomic revision of Asterocolax

Red algal parasites are highly host specific organisms that are morphologically reduced with decreased pigmentation. Only found within the Florideophyceae, red algal parasites have evolved within eight orders, with the greatest parasite diversity found in the Ceramiales. A quarter of the ceramialian parasites in the family Delesseriaceae are described in the genus Asterocolax. The initial morphological description of Asterocolax led to the creation of an independent genus devoted to these parasitic species, but molecular data have repeatedly demonstrated that Asterocolax species, and likely many other red algal parasites, resolve within the genera of free-living red algae, often within the same genus as their hosts. Here and in previous studies, phylogenetic analysis of the internal transcribed spacer region of the ribosomal DNA has shown at least six instances of independent evolution of Asterocolax species, mainly interspersed among the free-living macroalgal genera of Phycodrys and Polyneura. As most Asterocolax are sister species to their hosts, they are independently derived from a photosynthetic ancestor, and together, do not form a monophyletic parasitic genus. Here we conduct a long overdue taxonomic revision of the red algal parasitic genus Asterocolax, describe a new species within the genus, and propose nomenclatural changes for four other species to reduce the polyphyletic clades encompassing Asterocolax.

Rare inventory of trematode diversity in a protected natural reserve

In the face of ongoing habitat degradation and the biodiversity crisis, natural reserves are important refuges for wildlife. Since most free-living organisms serve as hosts to parasites, the diverse communities in protected areas can be expected to provide suitable habitats for a species-rich parasite fauna. However, to date, assessments of parasite diversity in protected nature reserves are rare. To expand our knowledge of parasite communities in natural habitats, we examined 1994 molluscs belonging to 15 species for trematode infections in a central European natural reserve. The parasitological examination revealed an overall prevalence of 17.3% and a total species richness of 40 trematode species. However, the parasite diversity and prevalence did not differ markedly from trematode communities in non-protected environments, which might be partly explained by a dilution effect caused by a high number of non-host organisms in our study system. The proportion of complex and long life cycles of parasites in the present study is high, indicating complex biotic interactions. We conclude that life cycle complexity, in addition to parasite diversity and trematode species richness, can provide valuable information on ecosystem health and should therefore be considered in future studies.

Drivers of parasite β-diversity among anuran hosts depend on scale, realm and parasite group

A robust understanding of what drives parasite β-diversity is an essential step towards explaining what limits pathogens' geographical spread. We used a novel global dataset (latitude −39.8 to 61.05 and longitude −117.84 to 151.49) on helminths of anurans to investigate how the relative roles of climate, host composition and spatial distance to parasite β-diversity vary with spatial scale (global, Nearctic and Neotropical), parasite group (nematodes and trematodes) and host taxonomic subset (family). We found that spatial distance is the most important driver of parasite β-diversity at the global scale. Additionally, we showed that the relative effects of climate concerning distance increase at the regional scale when compared with the global scale and that trematodes are generally more responsive to climate than nematodes. Unlike previous studies done at the regional scale, we did not find an effect of host composition on parasite β-diversity. Our study presents a new contribution to parasite macroecological theory, evidencing spatial and taxonomic contingencies of parasite β-diversity patterns, which are related to the zoogeographical realm and host taxonomic subset, respectively. This article is part of the theme issue ‘Infectious disease macroecology: parasite diversity and dynamics across the globe’.

The future of zoonotic risk prediction

In the light of the urgency raised by the COVID-19 pandemic, global investment in wildlife virology is likely to increase, and new surveillance programmes will identify hundreds of novel viruses that might someday pose a threat to humans. To support the extensive task of laboratory characterization, scientists may increasingly rely on data-driven rubrics or machine learning models that learn from known zoonoses to identify which animal pathogens could someday pose a threat to global health. We synthesize the findings of an interdisciplinary workshop on zoonotic risk technologies to answer the following questions. What are the prerequisites, in terms of open data, equity and interdisciplinary collaboration, to the development and application of those tools? What effect could the technology have on global health? Who would control that technology, who would have access to it and who would benefit from it? Would it improve pandemic prevention? Could it create new challenges? This article is part of the theme issue ‘Infectious disease macroecology: parasite diversity and dynamics across the globe’.

Predictions of primate–parasite coextinction

Future biodiversity loss threatens the integrity of complex ecological associations, including among hosts and parasites. Almost half of primate species are threatened with extinction, and the loss of threatened hosts could negatively impact parasite associations and ecosystem functions. If endangered hosts are highly connected in host–parasite networks, then future host extinctions will also drive parasite extinctions, destabilizing ecological networks. If threatened hosts are not highly connected, however, then network structure should not be greatly affected by the loss of threatened hosts. Networks with high connectance, modularity, nestedness and robustness are more resilient to perturbations such as the loss of interactions than sparse, nonmodular and non-nested networks. We analysed the interaction network involving 213 primates and 763 parasites and removed threatened primates (114 species) to simulate the effects of extinction. Our analyses revealed that connections to 23% of primate parasites (176 species) may be lost if threatened primates go extinct. In addition, measures of network structure were affected, but in varying ways because threatened hosts have fewer parasite interactions than non-threatened hosts. These results reveal that host extinctions will perturb the host–parasite network and potentially lead to secondary extinctions of parasites. The ecological consequences of these extinctions remain unclear. This article is part of the theme issue ‘Infectious disease macroecology: parasite diversity and dynamics across the globe’.

Phanerozoic parasitism and marine metazoan diversity: dilution versus amplification

Growing evidence suggests that biodiversity mediates parasite prevalence. We have compiled the first global database on occurrences and prevalence of marine parasitism throughout the Phanerozoic and assess the relationship with biodiversity to test if there is support for amplification or dilution of parasitism at the macroevolutionary scale. Median prevalence values by era are 5% for the Paleozoic, 4% for the Mesozoic, and a significant increase to 10% for the Cenozoic. We calculated period-level shareholder quorum sub-sampled (SQS) estimates of mean sampled diversity, three-timer (3T) origination rates, and 3T extinction rates for the most abundant host clades in the Paleobiology Database to compare to both occurrences of parasitism and the more informative parasite prevalence values. Generalized linear models (GLMs) of parasite occurrences and SQS diversity measures support both the amplification (all taxa pooled, crinoids and blastoids, and molluscs) and dilution hypotheses (arthropods, cnidarians, and bivalves). GLMs of prevalence and SQS diversity measures support the amplification hypothesis (all taxa pooled and molluscs). Though likely scale-dependent, parasitism has increased through the Phanerozoic and clear patterns primarily support the amplification of parasitism with biodiversity in the history of life. This article is part of the theme issue ‘Infectious disease macroecology: parasite diversity and dynamics across the globe’.