Sanitary behaviours induced by fungal infection in Myrmica scabrinodis

Ants are frequently targeted by parasites, and in some cases parasites induce changes in life history, physiology and behaviour of the hosts. The social life of ants implies high frequency of contacts among nestmates, that increases the risk of spreading any pathogen among colony members. Rickia wasmannii is an ectoparasitic fungus of the order Laboulbeniales (Ascomycetes), that obligatorily exploits ant species of the genus Myrmica. Little is known about its exact interactions with its hosts. In the frame of laboratory studies we investigated the changes that the parasite could induce in the behavior of the host. We performed two different experiments: (1) we recorded the time elapsed to the discovery of infected corpses (uninfected corpses were used as control), and the ants’ reactions to them, e.g. the number of aggressive behavioural acts; (2) we recorded the frequency and the time of auto- and allo-grooming behaviour of infected and uninfected ant individuals. Our results suggest that infection with R. wasmannii seems to modify, although to lesser extent, the behaviour of infected individuals

Could fungal infection make ant societies more open?

Ant colonies are a highly rewarding target for many pathogens and parasites and they also host various species of social parasites that exploit their social system. Myrmica ants seem to be particularly susceptible to exploitation by social parasites and by ecto- and endoparasites. Also many Myrmica colonies frequently adopt unrelated gynes, which can be interpreted as temporary social parasites. Myrmica scabrinodis is a common host of the ectoparasitic fungus Rickia wasmannii and its colonies are used by socially parasitic butterfly larvae of Maculinea genus. In some M. scabrinodis populations both R. wasmannii and Maculinea butterflies occur together using the same host colonies. In our study we used such population to check whether fungal infection change the threshold of acceptance of social parasites and unrelated queens by ants and make colonies more open for strangers. For this purpose we performed experiments during which we tested how infection by R. wasmannii affects frequency and time of Maculinea larva adoption and adoption of unrelated ant queens. We also carried out aggression tests where we used M. scabrinodis workers originating from infected and uninfected colonies to check if fungal infection influences the amount of adverse reactions. Our preliminary results indicate that ants infected by the fungus are more readily adopting social parasites, while being less aggressive towards foreign queens. Thus, infected colonies could be more prone for social parasitism

Distribution of the myrmecoparasitic fungus Rickia wasmannii (Ascomycota: Laboulbeniales) across colonies, individuals, and body parts of Myrmica scabrinodis

The ant species Myrmica scabrinodis plays a markedly important ecological role through much of the humid grasslands of Eurasia. It hosts a species-rich community of pathogens and parasites, including Rickia wasmannii, an enigmatic member of entomoparasitic laboulbenialean fungi. This study provides a descriptive ecology of R. wasmannii by characterizing its prevalence and distribution across several hierarchical levels: colonies, individuals, and anatomic body parts. Infections were restricted to a single ant species, Myrmica scabrinodis, and infected colonies occurred predominantly in wet habitats. Infections tended to be highly prevalent within infected colonies, often reaching 100% sample prevalence among workers. Individual infections exhibited an aggregated distribution typical to host-parasite systems. Workers from the aboveground part of nests (presumably older ones acting as foragers) were more infected than those from the belowground part. Fungal thalli could be found all over the body of the hosts, the head and the abdomen being the most infected parts of the body. The fungi’s distribution among host body parts statistically differed between low versus high-intensity infections: the initial dominance of the head decreased with advancing infection. These findings may provide baseline data for future comparative or monitoring studies

Does fungal infection produce cheaper workers?

Cuticle quality is of vital importance in insects. Amongst others, it prevents desiccation, and protects against pathogens. Therefore the development of thicker cuticle would be advantageous. The within-species variation of cuticle structure is affected by many factors, both physiological and ecological. Parasites can also affect the exoskeleton structure either to facilitate intrusion or to aid transmission to the next host. In the frame of our study we investigated the effect of an ectoparasitic fungus, Rickia wasmannii on the cuticle of its host. We measured the thickness of the exoskeleton in infected and uninfected ants originating from three European populations. Infected ants had thinner cuticle than uninfected ones, while there were also differences among populations. It is unclear though, whether this is the host’s response investing less into cuticle formation, or the fungus infects colonies with thin cuticle. Either way, within-species variation is linked to response to parasitic pressure

Morphometric characteristics and COI haplotype diversity of Arctodiaptomus spinosus (Copedoda) populations in soda pans in Hungary

Arctodiaptomus spinosus (Daday, 1891) is a characteristic species of the soda pan zooplankton in the Great Hungarian Plain. The biogeographical distribution of the species is interesting, since its range expands from the Pannonian Biogeographic region to the other side of the Carpathians, occurring in saline lakes in Eastern Anatolia, Armenia, Iran and in temporary waters in Ukraine. Our investigations focused on the morphometric characteristics and the COI haplotype diversity of four Hungarian populations in the Kiskunság area. We detected substantial morphological differences between the Böddi-szék population and the rest of the sampling sites, however considerable differences were not observable in the COI haplotypes in the populations. The 20 animals investigated for COI haplotypes belonged to the same haplotype network. Tajima?s D indicated departures from the neutral Wright ? Fisher population model and suggested population expansion. The genetic composition of Arctodiaptomus spinosus populations in the Kiskunság area is rather uniform

Nutrient regulation in ants (Hymenoptera: Formicidae): a review

International audienceAs for all living organisms, the nutritional needs of ants change over time in response to varying environmental conditions and demands for growth, health, and reproduction. Solitary individuals regulate their nutritional intake to maintain an appropriate balance of nutrients by selectively choosing the quality and quantity of food that meet their nutritional requirements. For social organisms, such as ants, food collection for the entire colony relies on a few individuals whose nutritional requirements may be very different from those of other members of their colony. Recent studies have used an integrative framework, the “geometric framework”, to better understand how living organisms regulate macronutrient intake to defend a specific nutrient “intake target”. In this review, we first reveal how the geometric framework has been used to deepen our understanding of ant communal nutrition. Second, we describe how this framework might be used to also understand the nutritional strategies used by ants facing infection challenges. Lastly, we conclude with a brief discussion of the promising techniques that could be used in the future to improve our understanding of communal nutrition in ants

Rickia wasmannii increases the need for water in Myrmica scabrinodis (Ascomycota: Laboulbeniales; Hymenoptera: Formicidae)

The order Laboulbeniales (Fungi, Ascomycota) is a little-studied group of microscopic ectoparasites of invertebrates, mostly insects. The effects of Laboulbeniales species on their hosts are mostly unknown. Rickia wasmannii Cavara, 1899 is a common Laboulbeniales fungus occurring in Europe and is currently known to be a parasite of at least eight Myrmica ant species. R.wasmannii serves as a good model organism for Laboulbeniales–host interactions, as this species covers the host in a very high density, and infected host individuals can be easily collected in high numbers. The effect of R. wasmannii on the survival rate of its most common host species, Myrmica scabrinodis Nylander 1846, was therefore investigated in a laboratory experiment on an individual level. To enhance the results, environmental stresses were simulated by depriving infected and uninfected workers of water and food. The survival of individuals was recorded hourly until the death of the last individual. Infected specimens were significantly more sensitive to the withdrawal of food and water than uninfected specimens. When we tested for water consumption, we found that infected ants spent more time consuming water than uninfected ants. Therefore, it is possible that infected ants must replace the loss of water. Based on these results, R. wasmannii substantially decreases the chances and time of survival of infected individuals, at least in resource-limited environments, which suggest that R. wasmannii has a negative effect on its host

Variability in activity differs between castes in the ant Linepithema humile

1. The study of behavioural variability has a long research tradition in social insects. Because of their contribution to division of labour, between-individual variations have been mostly studied within the worker caste. In contrast, the level of behavioural variation between queens has been much less studied. 2. In ants, a high level of behavioural variability could contribute to the ecological success of invasive species by favouring the colonisation of new environments. 3. In the invasive ant species Linepithema humile (Mayr), we used a standardised test to assess plasticity and predictability in activity level between workers and queens. 4. We found that only queens, not workers, displayed between-individual variability in plasticity. 5. We propose that the behavioural variability of queens could be an asset favouring the adaptation of invasive ant species to changing environments