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The red swamp crayfish, Procambarus clarkii, is a paradigmatic invader of freshwater systems. Several attempts have been made to mitigate its multiple impacts but none was successful. Among the different methods proposed, the use of the European eel (Anguilla anguilla) as an indigenous predator is promising but the available information about its predatory ability on crayfish is to date scanty. To fill this gap in knowledge, we ran three experiments in wetlands and irrigation ditches in Italy. The first experiment, in the laboratory, was aimed at quantifying the extent of predation by eels on crayfish, the second, in enclosures, the size classes of crayfish mainly preyed and the possible effect of the eels on P. clarkii behaviour, and the third, in the field, its ability to effectively reduce crayfish populations. Results showed that eels prey on small-sized or soft crayfish, attacking them from the back; an indirect effect was to reduce crayfish trophic activity, which in turn might increases crayfish mortality due to starvation and decreases impact on the community. However, as shown in the field, the use of eels should be appropriately calibrated to the context of application. Taken together, our results show that eels might be used as a complement to the traditional trapping method. However, additional studies are necessary to understand the adequate number of eels to be introduced and to develop appropriate methods for quantifying such effects.

Gastropod shells are vital for the majority of hermit crab species, being essential for their survival, growth, protection, and reproduction. Given their importance, shells are acquired and transferred between crabs through several modalities. We conducted observations and experiments at the Asinara Island (Sardinia, Italy) to investigate the efficacy of the different behavioral tactics adopted by the hermit crab Clibanarius erythropus to acquire shells, such as: (1) locomotion and activity at different tidal phases; (2) attendance at shell-supplying sites (simulated predation sites with five different odors: live and dead gastropods, live and dead crabs, predator); and (3) interactions with conspecifics in aggregations on simulated gastropod predation sites. In each tidal phase, locomotion was slow (0.7 cm min − 1 ) and, as a consequence, the probability of encountering empty shells and conspecifics was low. Simulated gastropod predation sites quickly attracted a larger number of hermit crabs than the other sites tested. Aggregations seemed to function as shell exchange markets, as previously suggested for other species: the first attendant took the experimental shell and a chain of shell exchanges among conspecifics followed. Our results show that, in C. erythropus , aggregation is the most efficient tactic for the acquisition of new shells, whereas in other species, such as Pagurus longicarpus , it is associated with exploitation ability due to the intense locomotion. The interspecific plasticity in hermit crabs' behavior is confirmed.

In the latest years, blooms of toxic Cyanobacteria have intensified worldwide, causing serious problems to human health. The edible crayfish Procambarus clarkii is known to accumulate the toxins (microcystins) produced by Microcystis aeruginosa. Our aims here were to (1) quantify microcystin-LR in P. clarkii's organs/tissues; (2) analyse differences in its content between size classes and between sexes; (3) develop protocols for the depuration of the toxin from crayfish; and (4) assess the quality of the crayfish abdominal muscle during depuration. The study was composed of two phases. In the first, the concentration of microcystin-LR in the hepatopancreas, stomach, intestine, and abdominal muscle of 102 crayfish was measured by the means of ELISA and was compared between small and large individuals and between sexes. In the second phase, 136 crayfish (64 males and 64 females) were subject to depuration for a maximum period of 21 days under two feeding regimes (ad libitum, i.e. fed every day or restricted, i.e. once every third day). Sixteen crayfish were sacrificed at different times from the start of the treatment (3, 6, 9, 14, 17, and 21 days). Microcystin-LR was measured in the intestines and in the abdominal muscles of the treated crayfish and was compared to the values obtained from individuals sacrificed immediately upon capture. The abdominal muscle was also analysed for its quality by quantifying colour, water holding capacity, and composition (qualitative and quantitative) of the total lipids and fatty acids. The results showed that (1) P. clarkii accumulates more toxin in the intestine and less in the abdominal muscle (the edible part); (2) microcystin-LR is less abundant in large (the marketable size) than in small individuals; and (3) its content differs between sexes in the hepatopancreas only. Besides, (4) microcystin-LR content decreased in the abdominal muscle, but not in the intestine, after a short period of depuration in the two feeding regimes and (5) depuration did not reduce the overall quality of crayfish meat.

International audience; As part of the Austropotamobius pallipes species complex, the crayfish Austropotamobius italicus is a species of community interest whose preservation requires the designation of Special Areas of Conservation (SACs) (Annex II, EU Habitats Directive). This study aimed at (1) assessing the conservation status of this threatened indigenous species by stock assessment in central Italy and (2) identifying some aspects of its elective habitat.

Genetic studies have shown that the threatened crayfish Austropotamobius pallipes species complex is composed of two lineages (A. italicus and A. pallipes), both occurring in Italy. However, the issue surrounding their taxonomic status has not yet been solved even though the confused taxonomy may hamper attempts to conserve indigenous crayfish. The aim of this study was to develop methods for the morphometrical characterization of the A. pallipes species complex. Having analysed 18 morphometric variables on a total of 44 specimens of each lineage, we showed that the tip of the rostrum could be used to discriminate A. italicus and A. pallipes. Such discrimination was also obtained by analysing the size and shape of both the female spermatophoric plate and the male gonopods. These results confirm the potential to adopt morphometric studies to complement the genetic characterization of cryptic species.

The white-clawed crayfish Austropotamobius pallipes complex is native to Europe, being present in 18 European countries, Italy included. However, the number and abundance of its populations are today restricted and it has been recently classified as “endangered” by IUCN (International Union for Conservation of Nature). Here, we report the first record of this freshwater crayfish in Sardinia Island (Italy). Using a fragment of the mitochondrial DNA 16S rRNA gene, we identified three haplotypes that correspond to the A. italicus meridionalis subclade. We provide information about the sampling area, population density and finally discuss hypotheses about the occurrence of this population in Sardinia, comparing it with other Mediterranean populations. Our results improve the existing knowledge about the phylogeography of the taxon across Italy, confirming its complex pattern of distribution. In addition to the non-native status of the Sardinian A. i. meridionalis crayfish, we showed that the most proximal Mediterranean population of white-clawed crayfish existing in Corsica belongs to A. pallipes from Southern France.

Any initiative aimed at the management of a threatened species needs a good knowledge of its environmental requirements. Aims of this study were to individuate suitable areas for the reintroduction of crayfish species belonging to the Austropotamobius pallipes complex and to evaluate the causes of the local extinction in Tuscany (Italy) of some populations. Between May 2003 and September 2004, we collected ecological data from 19 streams of 4 catchments, 9 watercourses where crayfish were present (WI) and 10 where they were present in the recent past and absent now (WO), and we compared them. Multivariate analyses were performed using chemico-physical and biotic parameters to examine the relationships between their values and the presence of crayfish. The results did not allow us to find significant differences between the two categories of streams, suggesting their suitability for crayfish reintroduction.

International audience; We studied the genetic variability of the indeigenous crayfish Austropotamobius italicus in 14 populations inhabiting five basins in Tuscany (Italy). This species is subject to a drastic decline in abundance across its entire range. Using a fragment of the mitochondrial DNA 16S rRNA gene, we identified eight haplotypes, six corresponding to A.i. italicus and two to A.i. meridionalis; the two clades were found in syntopy in one stream. Eight populations of A. i. italicus analyzed for their microsatellite loci, showed a low intra-population genetic variability and a high inter-population genetic divergence. Populations sampled in the Sieve basin showed no heterozygotes and a high level of inbreeding. The knowledge on the genetic structure of the studied populations, combined with information on their ethology, ecology, and demography, is an essential prerequisite for any action aimed at reintroducing or restocking this threatened species.