Alberto Francesco Inghilesi

Who’s what? Prompt recognition of social status in crayfish

Crayfish are excellent model organisms to study the proximate mechanisms underlying the maintenance of dominance hierarchies in invertebrates. Our aim here was to investigate whether Procambarus clarkii males use social eavesdropping to discriminate dominant from subordinate crayfish. To this end, we conducted an experiment composed of a “passive” and an “active” phase. In the passive phase, “focal” individuals were allowed (treatment 1) or not (treatment 2) to see and smell two size-matched crayfish fighting while, in the subsequent active phase, they were allowed to freely interact with the fighting dyad. None of the recorded variables showed any significant difference between the two treatments, but, invariably, focal individuals were able to promptly discriminate dominant from subordinate crayfish. This study provides evidence that male crayfish recognize the social status of a conspecific without the need of direct or indirect experience with it and avoid dominants—and thus dangerous opponents—by means of a badge of status. A form of “winner and loser effects” could also contribute to the structuring of dominance/subordinate relationships. The implication of these results in understanding the maintenance of dominance hierarchies in invertebrates are discussed and compared with findings previously achieved in the context of mate choice by P. clarkii females, who do appear to use eavesdropping to identify dominants and subordinates.

A new threat to groundwater ecosystems: first occurrences of the invasive crayfish Procambarus clarkii (Girard, 1852) in European caves

The American red swamp crayfish, Procambarus clarkii, is today the alien species most widespread in European water bodies. This invasive crayfish was found for the first time in some caves of Europe, specifically in Portugal and Italy. The presence of P. clarkii in caves is noteworthy, representing a new threat for the groundwater ecosystems due to the possible negative impacts on the native communities.

Sterile Rhynchophorus ferrugineus males efficiently impair reproduction while maintaining their sexual competitiveness in a social context

The red palm weevil Rhynchophorus ferrugineus, recently spreading from its native range throughout the world, is one of the most dangerous pests for several palm species. The sterile insect technique (SIT) is a promising environmentally friendly approach for the management of this pest. An essential prerequisite of the SIT is that irradiated males released in nature are as sexually competitive as their wild counterparts. Here we evaluated the potential use of the SIT in red palm weevil males by investigating the sexual competitiveness of gamma-irradiated (Cobalt 60 source, dose 80 Gray) males in the laboratory in a natural-like social context with a balanced sex ratio and by testing their efficacy in impairing female reproduction. Our results showed that irradiation did not affect any of the mating behaviour parameters. However, the male reproductive potential was drastically reduced, as fertility was markedly decreased in females mated with irradiated males. Therefore, an 80 Gray irradiation dose is a promising option for the SIT in the control of the red palm weevil, producing sterile but sexually competitive males when tested in a natural-like mating context.

How ecosystems change following invasion by Robinia pseudoacacia : Insights from soil chemical properties and soil microbial, nematode, microarthropod and plant communities

Biological invasions are a global threat to biodiversity. Since the spread of invasive alien plants may have many impacts, an integrated approach, assessing effects across various ecosystem components, is needed for a correct understanding of the invasion process and its consequences. The nitrogen-fixing tree Robinia pseudoacacia (black locust) is a major invasive species worldwide and is used in forestry production. While its effects on plant communities and soils are well known, there have been few studies on soil fauna and microbes. We investigated the impacts of the tree on several ecosystem components, using a multi-trophic approach to combine evidence of soil chemical properties and soil microbial, nematode, microarthropod and plant communities. We sampled soil and vegetation in managed forests, comparing those dominated by black locust with native deciduous oak stands. We found qualitative and quantitative changes in all components analysed, such as the well-known soil nitrification and acidification in stands invaded by black locust. Bacterial richness was the only component favoured by the invasion. On the contrary, abundance and richness of microarthropods, richness of nematodes, and richness and diversity of plant communities decreased significantly in invaded stands. The invasion process caused a compositional shift in all studied biotic communities and in relationships between the different ecosystem components. We obtained clear insights into the effects of invasion of managed native forests by black locust. Our data confirms that the alien species transforms several ecosystem components, modifying the plant-soil community and affecting biodiversity at different levels. Correct management of this aggressive invader in temperate forests is urgently required.

First Report for Europe of Ataenius picinus (Coleoptera: Scarabaeidae: Aphodiinae)

The Aphodiinae subfamily (Coleoptera: Scarabaeidae: Aphodiinae) is mainly coprophagous, except a number of species with saprophagous, phytosa pro phag ous and polyphagous feeding habits. Some of them severely damage the roots of several cultivations (e.g. Eupariini) (Stebnicka, 2004; Dellacasa and Dellacasa, 2006), as in the case of larvae of Aphodius pardalis Le Conte, 1857 which reportedly reach densities of 1000 m-2 in pastures in Oregon (USA) (Ritcher and Mor ri son, 1955). Euparinii show a great ability to spread their distribution as contaminants of many commodities, in particular soil samples. Many species are acclimated in Europe, such as Ataenius brevicollis Wollaston, 1854 and Para taenius simulator Harold, 1868, introduced in Portugal (Lobl and Smetana, 2006). In the Southeast of United Kingdom, the Australian species Saprosites mendax Black burn, 1892 has been established since 1930 (Tottenham, 1930). Ataenius picinus is a widely distributed species across the world. It has been described under several names (Cartwright, 1945, 1948, 1964, 1970; Watt, 1948; Chalumeau, 1992). Its elevated ability to tolerate a wide range of ecological conditions is the reason for its potential to be carried around the world with ships and airplanes, as a stowaway or as a contaminant of commodities. It is regarded as a minor pest: its larvae may damage seedlings, whereas adults may damage strawberries, potatoes, and beans (Stebnicka, 2004). Ataenius picinus can be easily collected at light (Watt, 1984) and found in pitfall traps, in cow (Cartwright, 1964) and sheep dung, in leaf litter samples, soil and compost heaps, under carrion and stones, and in decaying fruits (Watt, 1984) and mushrooms (Stebnicka, 2004). Its native distribution includes South and Central America (Argentina, Bolivia, Brazil, Chile, Costa Rica, Honduras, Mexico, Paraguay, Uruguay, West Indies) and the Southern United States (Stebnicka, 2004). Its present distribution comprises Australia (Stebnicka and Howden, 1997), New Zealand (Stebnicka, 2001), New Caledonia, Fiji, and Vanuatu (Stebnicka, 2004). In 2009, a specimen of Ataenius picinus Harold, 1867 was found on July 17 in the handling area of empty containers. This is the first record for Europe and the Volume 122, Number 1, January and February 2011 97

The effects of two different preservation methods on morphological characteristics of the alien channel catfish Ictalurus punctatus (Rafinesque, 1818) in European freshwater

Abstract Different methods used to store specimens, even for short periods, can notably affect morphometric characteristics such as colour, length and shape. As a consequence, in the case of samples that have to be analysed morphometrically, the right preservation method is crucial. In this study, two comparably easy applicable methods, the effects of freezing and moderate cool storage on morphological traits, were studied on specimens of the scaleless North American channel catfish Ictalurus punctatus, an alien species to European freshwaters of increasing concern. Results revealed that freezing, like preservation with alcohol or formalin, affected the generally considered characteristics (colour, standard length, fork length, total length, shape), while cool storage was shown to preserve most traits without notable alteration, an important difference when studying potentially adapting alien species. Implications are discussed.

Native crab and crayfish co-occurrence: First evidence in Europe

Abstract Cases of co-occurrence among freshwater decapods are few. In their European range, the crab Potamon fluviatile and the white-clawed crayfish Austropotamobius pallipes complex do not usually share the same stream section or pond even if they live in sympatry, suggesting a strong segregation of the two species. The coexistence was hypothesized during the Pleistocene era, but without evidence of recent contact between them. The co-occurrence of these two species (i.e., occupying a common area) is reported in a stream of the Central Italy, being the first case in Italy and in Europe. To assess this co-occurrence, in 2015 we investigated three transects (only crabs, only crayfish and both species), collecting biotic and abiotic data. The three transects were similar for canopy cover, substrate composition and density of potential shelters (but not for the abiotic parameters), and characterized by a good water quality and abundance of preys, being suitable for the two species. No agonistic behavioural patterns have been observed, leading to hypothesize that co-occurrence may be favoured by the slightly smaller size of crayfish and crabs in the shared area than the size of animals in the other transects or by the different microhabitats chosen by crayfish and crabs when sharing the same stream section. Other possible explanations are discussed here, but further studies are necessary to better understand the co-occurrence of these two native crustaceans. Moreover, urgent measures are demanded to guarantee the survival of these protected species hampered by several threats.