Some like it cold: the glossiphoniid parasites of the Sicilian endemic pond turtle Emys trinacris (Testudines,Emydidae), an example of ‘parasite inertia’?

The freshwater turtles of the genus Emys and some leech species of the family Glossiphoniidae are the only Palaearctic representatives of primarily Nearctic taxa, which jointly colonized Eurasia and the Maghreb during the Miocene. The strict trophic relationships occurring between the glossiphoniid parasite leech Placobdella costata and its host, the emydid Emys orbicularis, make them a prime example of host–parasite cophylogenetic evolution. In the light of the discovery of the Sicilian cryptic endemic species Emys trinacris, which is the sister species to the widespread Palaearctic E. orbicularis, the possible cophylogenetic divergence of the turtle hosts and their leech parasites was investigated. In spite of the deep divergence scored between the two pond turtle species and of their allopatric distribution, their leech parasites proved to be conspecific and indistinguishable based on the implemented molecular marker. This unexpected decoupling might likely be ascribed to the different dispersal abilities of the two taxa and/or to the recent, human‐mediated introduction of the leech parasites in Sicily. If this last scenario is confirmed, the long‐term effects of the introduced leech parasite on the endemic Sicilian pond turtle Emys trinacris should be carefully monitored. In the frame of this study, representatives of the widely spread predatory leech Helobdella stagnalis were observed on E. trinacris. Molecular analyses of their stomach content allowed to rule out the possibility of the existence of a trophic relationships between these two taxa, in contrast to what was previously suspected, and suggest that H. stagnalis specimens were rather attached to the turtles for non‐nutritional reasons.     

Microsporidia Can Acquire Lamin‐like Intermediate Filaments and Cell Adhesion Catenin‐cadherin Complexes from the Host (?)

On their spore surfaces, Microsporidia often develop a canopy of filaments with characteristics of intermediate filaments (IF), as we demonstrated in previous studies on Thelohania sp., Ameson michaelis, and Spraguea lophii. Genomic studies indicate that among invertebrates, lamins that may localize in the cytoplasm or nucleus, are the only known IF type. These IFs can bind to the substrate containing cell adhesion molecules (CAMs) cadherins, associated with β and γ catenins. The objects of this study were to determine whether microsporidia have CAMs with the attached IFs on their envelopes and to find out if these proteins are provided by the host. An examination was made for localization of lamins and CAMs on the spores of the mentioned above species and Anncaliia algerae, plus in the host animals. Then, we determined whether the spores of A. michaelis and A. algerae could bind vertebrate nuclear lamin onto the spore surface. We also tested transgenic Drosophila melanogaster stocks bearing cadherin‐GFP to see whether developing A. algerae parasites in these hosts could acquire host CAMs. The tests were positive for all these experiments. We hypothesize that microsporidia are able to acquire host lamin IFs and cell adhesion catenin–cadherin complexes from the host.     

Effectively vertical transmission of a Drosophila‐parasitic nematode: mechanism and consequences

1. Long‐term control of insects by parasites is possible only if the parasite populations persist. Because parasite transmission rate depends on host density, parasite populations may go extinct during periods of low host density. Vertical transmission of parasites, however, is independent of host density and may therefore provide a demographic bridge through times when their insect hosts are rare. 2. The nematode Howardula aoronymphium, which parasitises mycophagous species of Drosophila, can experience both horizontal and effectively vertical transmission, relative rates of which depend, in theory at least, on the density of hosts at breeding sites. 3. A nine‐generation experiment was carried out in which nematodes were transmitted either exclusively vertically or primarily horizontally. This experiment revealed that these parasites can persist and exhibit positive population growth even when there is only vertical transmission. 4. Assays at the end of the experiment revealed that the vertically transmitted nematodes had suffered no inbreeding depression and that they were similar to the horizontally transmitted nematodes in terms of virulence, infectivity, within‐host growth rate, and fecundity. Thus, vertical transmission of H. aoronymphium did not appear to compromise the ability of these parasites to control Drosophila populations.