Predator-prey encounters:deciphering the robbery relationship between highwayman flies and their ant victims

Examples of predator–prey interactions in which flies rob ants are uncommon.To date,this behavior has only been recorded in the genus Bengalia Robineau-Desvoidy(Bengaliinae,Diptera,Calliphoridae).These predatory flies ambush ants,and rob them of the food or offspring that they are carrying.However,because of the rarity of this behavior,the reasons and consequences(evolutionary advantages)are unknown,and indeed,the behavior has been sometimes considered anecdotal.In this study,we employed field investigations and behavioral analyses to investigate whether the sex of the fly Bengalia varicolor,or the weight and quality of the food carried by Pheidole nodus ants influenced fly–ant interactions in their natural habitats.We show that food weight and quality influenced the behavior of B.varicolor independent of the fly’s sex.Robbing behavior by the flies was more successful when the food robbed was of high-quality and light in weight.Furthermore,the weight of the food robbed modulated the escape distance the flies could carry it.This then may affect the food quality and weight transported by the ants.This is a novel example of deciphering the relationship between highwayman flies and their ant victims.Given the widespread distribution of Bengalia flies,we suggest that such interspecific predator–prey encounters may shape the robbery interactions and the carrying behavior of further ant species in nature.

Isotopic niche provides an insight into the ecology of a symbiont during its geographic expansion

The study of the recent colonization of a symbiont and its interaction with host communities in new locations is an opportunity to understand how they interact.The use of isotopic ratios in trophic ecology can provide measurements of a species'isotopic niche,as well as knowledge about how the isotopic niches between symbiont and host species overlap.Stable isotope measurements were used to assess the sources of carbon assimilated by the host species(the bivalves Mytilus galloprovincialis and Scrobicularia plana)and their associated symbiont pea crab Afropinnotheres monodi,which occurs within these bivalves'mantle cavities.The mixing model estimates suggest that all of them assimilate carbon from similar sources,particularly from pseudofaeces and particulate organic matter in this symbiotic system based on filter feeding.The symbiotic species occupy comparable trophic levels and its association seems to be commensal or parasitic depending on the duration of such association.The pea crab A.monodi reflects a sex-specific diet,where males are more generalist than the soft females because the latter's habitat is restricted to the host bivalve.The high isotopic overlap between soft females and M.galloprovincialis may reflect a good commensal relationship with the host.

Ontogenetic niche specialization of the spider crab Libinia ferreirae associated with the medusa Lychnorhiza lucerna

Symbiotic relationships in marine environments are not fixed and can change throughout the animal’s life.This study investigated the ontogeny of symbiosis of the spider crab Libinia ferreirae with the host medusa Lychnorhiza lucerna.We described the type of relationship,the temporal correlation among species,and food habits.More than 50%of the sampled crabs were symbionts,most in early life stages.The highest number of crabs found in a single medusa was 11.Symbiosis was observed throughout most of the year but was more evident in warm periods.The crab has many benefits in this relationship with a medusa.One is the use of food resources captured by the medusa,primarily copepods.Because the crab steals the medusa’s food,it is a kleptoparasitic relationship.There is a niche partition between symbiont and the free-living crabs as they occupy different habitats and use nonoverlapping food resources.Previous research reported that symbiosis first developed during the crab’s last larval phase(megalopa)when crab and medusa are in the same habitat.Observation of the crab’s behavior shows that symbiosis occurs when the crab can grab to the medusa when the host touches the sea bottom.The crab also took advantage of water currents,releasing itself from the substrate and then drifting toward the medusa.The symbiotic relationship that crabs have with the medusa provides then with a nursery,food resources,shelter,dispersion,and decreased competition with free-living adult crabs,all essential for the crab’s survival.

Owner-Intruder contests with correlated resource values

We study a conflict of two individuals over a valuable resource.We construct a sequential game where the first individual,the Owner,decides whether to defend the resource and the other individual,the Intruder,decides whether to attack and try to steal the resource.Individuals know the value of the resource to themselves.This provides the individuals an estimate of the value of the resource to the opponent.We build a mathematical model that allows us to quantify and vary the accuracy of this estimate.We study how the outcomes of the game depend on the accuracy.We show that,in our setting,the accuracy does not matter to the Intruder but it does to the Owner.For resources of a large value,the Owner benefits from a smaller accuracy.However,for resources of a small value,the Owner benefits from a bigger accuracy.