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The hepatopancreas of crustaceans species has been recognized as an essential target organ to assess trace elements' effects. Due to its dynamic and capability of detoxifying trace metal, this organ often indicates distinct pathological disturbances. In the present work, we intend to evaluate the bioaccumulation of trace metal in three Orchestia species (Orchestia montagui, Orchestia gammarellus, and Orchestia mediterranea) living in symmetry in the banks of Bizerte lagoon (37°13'8″N 09°55'1″E) after their exposure during 14 days to a mixture of copper and zinc, and to highlight the effect of these metals on their hepatopancreas ultrastructure using transmission electron microscopy. At the end of the experiment, results showed that the mortality and the body mass varied according to the used nominal concentrations. Significant alterations were noted in all the treatment groups. The degree of these alterations depends on the used concentration, and they are represented especially by the cells remoteness and the border lyses, the reduction of the nuclear volume, the increase in the cytoplasm density with the presence of trace metal in the nucleus as well as in the vacuole, the disorganization and the destruction of microvilli, the condensation of the majority of cellular organelles and mitochondria swelling. Through this study, Orchestia genus could be an attractive candidate for the biochemical study of trace metal toxicity in Tunisian wetlands.

This study was conducted to compare metals bioaccumulation in the terrestrial isopod Armadillidium granulatum collected from Ghar El Melh lagoon. We focused on recognizing the effects of trace elements on hepatopancreas functional role. To this end, isopod specimens were exposed for 3 weeks to sediments contaminated with cadmium, copper, zinc, mercury, and nickel. Three concentrations were used in duplicate for each experimental condition. At the end of the experiment, metal body burdens were determined using flame atomic absorption spectrometry. Results of the bioaccumulation factor (BAF) showed that the species A. granulatum was classified as a Cu macroconcentrator (BAF > 2) and a Zn deconcentrator (BAF < 2). Dose dependent morphological and histological changes were observed in the hepatopancreas cells using transmission electron microscopy. The predominant features were: microvillus border disruption, condensation of the cytoplasm with increasing endoplasmic reticulum, mitochondria, lysosomes and granules that accumulated metals in B and S cells. The number of lipid droplets decreased especially after Cd, Zn, Hg, and Ni treatments. This study demonstrated that the terrestrial isopod A. gramulatum could be a good indicator of soil metal contamination.

The ultrastructural changes on the hepatopancreas of Porcellio laevis individuals were investigated after their exposure to a mixture of cadmium (Cd) and zinc (Zn) during four weeks. At the end of the experiment, trace element (TE) concentrations were determined using atomic absorption spectrometry (AAS). The growth of individuals was calculated and compared among the treatments. From the first week until the end of the experiment, a weight gain was observed in P. laevis individuals. Additionally, the TE concentrations in the hepatopancreas and in the rest of the body were considerable and seem to be dose dependent. Moreover, our results confirmed the role of the hepatopancreas as the main storage organ. Thus, the conducted transmission electron microscopy highlighted remarkable alterations on the hepatopancreas cells resulting from the Cd and Zn bioaccumulation. The displayed alterations are principally the disorganization of the S- and B-cells leading to a destruction of the microvilli border, an increase of the lipid droplets and mitochondria as well as the appearance of trace elements in the form of B-type granules. Based on the obtained results herein, we can conclude that Porcellio laevis might be a good candidate in the prevention of TE pollution in the terrestrial ecosystems.

Procambarus clarkii is a widespread invasive species and its biological traits have often been used to explain its successful colonization of new areas. However, studies on the genetic features of invasive populations are still scarce, and the use of molecular markers could bring new insights about biological invasions. After being introduced in Spain in 1973, P. clarkii was introduced in France (≈1976) and nowadays is widespread in its territory (61 departments) in wetlands which provide good conditions for a successful colonization. Here we ask whether the genetic diversity of invasive populations could help to understand the evolutionary history of its invasion. To investigate this issue, 227 individuals of P. clarkii from 27 French populations and 10 departments were collected, and a 553 bp COI fragment was amplified and sequenced using universal primers. For the analysis of genetic parameters, nucleotide diversity (π), and haplotype diversity (Hd), the populations were organized into four major groups. The nucleotide diversities (π) were 0.000154, 0.00119, 0.00118, and 0.00123 for group 1, 2, 3, and 4, respectively. The genetic diversity of French populations (Hd = 0.350; π = 0.00123) was lower than the native populations (Hd = 0.982; π = 0.00736). Nine haplotypes were found (H1–H9) in 230 sequences. Haplotype diversity (Hd) was 0.444, 0.239, 0.330, and 0.350 for groups 1, 2, 3, and 4, respectively. The haplotype network showed very similar haplotypes, differing by few mutational steps and showing some complex relationships. Three haplotypes related to the species’ native region were found (H1, H2, and H3). Each of these haplotypes was also related to biogeographical regions. The most frequent haplotype (H2) was widespread throughout 10 departments. The other six haplotypes (H4, H5, H6, H7, H8, and H9) were not found in the native region but, in some cases, shared some French populations. Translocation by humans is the most plausible explanation of the observed haplotype relationships. We suggest that genetic information should play a larger role in the development of policies to manage invasive species.

Made available in DSpace on 2019-10-04T12:33:33Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-01-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) IBAMA The characterisation of intraspecific genetic diversity in representatives of the South American crayfish genus Parastacus Huxley, 1879 is here carried out for the first time by comparing populations of Parastacus brasiliensis (von Martens, 1869) as currently defined. Phylogenetic reconstructions based on mitochondrial and nuclear markers indicate the existence of multiple lineages, of which only one can be considered as P. brasiliensis sensu stricto. In addition, there are seven other lineages, one of which is the subspecies Parastacus brasiliensis promatensis Fontoura & Conter, 2008, which is here elevated to species level. We thereby increase to 14 the number of recognised species within Parastacus in South America. Genetic distances among P. brasiliensis sensu stricto and the lineages A', B' and C' increase with geographical distances, suggesting isolation by distance as an important driver of diversification, and eventually speciation, in these burrowing crayfishes. Parastacus brasiliensis occurs mainly in the Guaiba Lake basin and studied populations show limited connectivity and gene flow, probably due to habitat fragmentation. On the basis of genetic and distribution data, the conservation status of P. brasiliensis sensu stricto is confirmed as Near Threatened (NT). These findings lead us to encourage the establishment of preservation areas for isolated populations. The importance of preserving the newly recognised distinct gene pools in order to maintain overall genetic diversity is emphasised. Univ Estadual Paulista, Invertebrate Morphol Lab, Aquaculture Ctr, Dept Biol Aplicada, Jaboticabal, SP, Brazil Univ Fed Rio Grande do Sul, Dept Zool, Programa Posgrad Biol Anim, Porto Alegre, RS, Brazil Univ Poitiers, Lab Ecol & Biol Interact, Equipe Ecol Evolut Symbiose, CNRS,UMR 7267, Poitiers, France Univ Regensburg, Zool & Evolutionary Biol, Regensburg, Germany Univ Estadual Paulista, Invertebrate Morphol Lab, Aquaculture Ctr, Dept Biol Aplicada, Jaboticabal, SP, Brazil CNPq: 201512/2012-2 CNPq: PQ 305900/2014-5 CAPES: 1989/2014 CAPES: 737/12 IBAMA: 34299-2

Among the many alien crustacean species so far recorded in the Mediterranean basin are numerous decapods—crayfish, crabs and prawns—that have in common the reputation of being both aggressive and adaptable to various environments. Their entrance to the Mediterranean basin has often been fostered by human actions, such as the transfer of new species for commercial purposes or accidentally, as bycatch or because they were present in discarded ships’ ballast water. Marine alien species enter the Mediterranean basin from two main directions: from the Atlantic and beyond, and from the Indian Ocean via the Suez Canal. For freshwaters, the extensive European canal network is an important aid to migration, but human discards are also significant. Protection of native fauna and ecosystems is at best partial. Freshwater ecosystems particularly at risk include lagoons, river estuaries, ponds and marshes, while comparable marine systems are shallow muddy coastal regions, rocky reefs, estuaries/bays and salt marshes. Local communities, principally anglers and people working with aquatic resources, usually are curious at the appearance of a new species and the possibility of establishing a new business is often the first thought. However, freshwater decapod alien species cause major damage to agriculture production, infrastructures, riverbanks, irrigation systems and fish production, leading to consistent economic losses. In particular, they are known to be injurious to plant production, causing increasing losses to agriculture, consuming young seedlings and seeds and causing substantial water losses from field areas. Less information is available for seawater species to date, but their increasing number and growing size of populations requires the attention of the scientific community to evaluate and predict their influence on the marine environment and/or on local fish and bivalve production. Both freshwater and marine alien decapods thus represent a serious threat to native European species and have a negative impact on species richness and habitats. The economic losses caused by these species require reliable and cost-effective options for managing their abundance and if possible for their eradication.

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International audience; Procambarus clarkii is currently recorded from 16 European territories. On top of being a vector of crayfish plague, which is responsible for large-scale disappearance of native crayfish species, it causes severe impacts on diverse aquatic ecosystems, due to its rapid life cycle, dispersal capacities, burrowing activities and high population densities. The species has even been recently discovered in caves. This invasive crayfish is a polytrophic keystone species that can exert multiple pressures on ecosystems. Most studies deal with the decline of macrophytes and predation on several species (amphibians, molluscs, and macroinvertebrates), highlighting how this biodiversity loss leads to unbalanced food chains. At a management level, the species is considered as (a) a devastating digger of the water drainage systems in southern and central Europe, (b) an agricultural pest in Mediterranean territories, consuming, for example, young rice plants, and (c) a threat to the restoration of water bodies in north-western Europe. Indeed, among the high-risk species, P. clarkii consistently attained the highest risk rating. Its negative impacts on ecosystem services were evaluated. These may include the loss of provisioning services such as reductions in valued edible native species of regulatory and supporting services, inducing wide changes in ecological communities and increased costs to agriculture and water management. Finally, cultural services may be lost. The species fulfils the criteria of the Article 4(3) of Regulation (EU) No 1143/2014 of the European Parliament (species widely spread in Europe and impossible to eradicate in a cost-effective manner) and has been included in the “Union List”. Particularly, awareness of the ornamental trade through the internet must be reinforced within the European Community and import and trade regulations should be imposed to reduce the availability of this high-risk species.

International audience; The crustacean cuticle is a hierarchically organised material which provides protection and sites for muscle attachment. The physical properties of this exoskeleton envelope are adapted to the function and the eco-physiological requirements of the species. This paper aimed to study, using the TEM, the structure of the tubercle and the tergite cuticle of the arid species Hemilepistus reaumurii in a comparison with a subhumid isopod in order to relate some peculiar features to an adaptive process to environmental constraints. Results showed that wild H. reaumurii cuticles were twice as thick in comparison with Porcellio variabilis which is a subhumid zone isopod. It is suggested therefore that the thick cuticle of wild H. reaumurii can be an adaptation to terrestrial life and a protection against osmotic stress and water loss in an arid environment. In addition the inside of the tubercle showed a high number of lipid droplets stacked into an adipose tissue which suggest that tubercles were used for storage for nutritive material in wild H. reaumurii.

Wolbachia bacteria are obligate intracellular alpha-Proteobacteria of arthropods and nematodes. Although widespread among isopod crustaceans, they have seldom been found in non-isopod crustacean species. Here, we report Wolbachia infection in fourteen new crustacean species. Our results extend the range of Wolbachia infections in terrestrial isopods and amphipods (class Malacostraca). We report the occurrence of two different Wolbachia strains in two host species (a terrestrial isopod and an amphipod). Moreover, the discovery of Wolbachia in the goose barnacle Lepas anatifera (subclass Thecostraca) establishes Wolbachia infection in class Maxillopoda. The new bacterial strains are closely related to B-supergroup Wolbachia strains previously reported from crustacean hosts. Our results suggest that Wolbachia infection may be much more widespread in crustaceans than previously thought. The presence of related Wolbachia strains in highly divergent crustacean hosts suggests that Wolbachia endosymbionts can naturally adapt to a wide range of crustacean hosts. Given the ability of isopod Wolbachia strains to induce feminization of genetic males or cytoplasmic incompatibility, we speculate that manipulation of crustacean-borne Wolbachia bacteria might represent potential tools for controlling crustacean species of commercial interest and crustacean or insect disease vectors.

Alien species have been transported and traded by humans for many centuries. However, with the era of globalization, biological invasions have reached notable magnitudes. Currently, introduction of alien species is one of the major threats to biodiversity and ecosystem functioning. The North American crayfish Procambarus clarkii is one of the most widely introduced freshwater species in the world, especially due to its high economic importance. It is responsible for great modifications in invaded environments causing irreparable ecological and economic damages. Its impressive ability to successfully colonize a wide range of environments is a consequence of its behavioural and biological characteristics that can adapt to features of the invaded location, conferring to this species a notable ecological plasticity. This review summarizes the available information regarding P. clarkii's biology and invasive dynamics around the world in order to contribute to the understanding of the threats posed by its establishment, as well as to support management and impact mitigation efforts.

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.

An essential tool in molecular ecology studies, the microsatellite markers allow the investigation of the genetic structure of populations. Here, we developed a panel of 12 polymorphic microsatellite markers isolated from a combination of two approaches: 454 pyrosequencing of a repeat-enriched genomic library and cross-species amplification. These microsatellite markers were isolated from Armadillidium nasatum for which they represent a promising tool regarding genetic studies. Moreover, this study increases the available number of microsatellite markers for A. vulgare and A. depressum for which some of these markers have also been amplified. A. nasatum is a terrestrial isopod (Crustacea, Oniscidea) belonging to the family Armadillidiidae (Vandel 1962). Terrestrial isopods are sensitive to environmental disturbances (Paoletti and Cantarino 2002) and pollutions (Sastrodihardjo and Van Straalen 1993). Thus, they provide information on the environmental quality of agroecosystems and are indeed considered as bioindicators (Souty-Grosset et al. 2005a). For example, grassland habitats in western France are managed in relation to woodlouse biodiversity (Souty-Grosset et al. 2005b). Terrestrial isopods are members of the detritivore guild promoting decomposition processes and nutrient cycling (Paoletti and Hassall 1999), consequently playing a key role in ecosystem services (Berg et al. 2010; David and Handa 2010). They constitute an interesting model because they are indispensable for biochemical ecosystem balance (Paoletti and Hassall 1999) and because of their suitability for measuring the direct effects of human activities on their habitats. Human practices such as soil tillage, pesticide application, chemical pollution, along with soil acidification adversely affect the soil macrofauna abundance

The red swamp crayfish, Procambarus clarkii, was discovered in 2007 in the “Parc naturel régional (PNR) de la Brenne” (France). Ten colonized sites have been identified in the park to date, including two new sites discovered in 2011. The present study aims at establishing a protocol suitable for estimating the population size of P. clarkii by the use of a Capture-Mark-Recapture (CMR) technique in a chain of five connected fish-ponds. Results show different cohorts of individuals among seasons and fish-ponds. However, trapping effort was not efficient enough to obtain an accurate estimate of the population size of this species in a fish-pond larger than 2 − 3 ha. On the other hand, the adopted protocol appeared useful to assess, in smaller fish-ponds, the effect of intensive trapping and other control methods on P. clarkii populations.

Currently, the distribution of the European native white-clawed crayfish (Austropotamobius pallipes) is restricted, fragmented and mainly located in headwater streams. Many European countries have active programmes for its conservation and some also have reintroduction programmes. Here, we used the ephemeropteran communities as a bioindicator of A. pallipes presence. Results from 36 brooks showed that the ephemeropteran richness is statistically higher in sites with crayfish compared to sites without crayfish. We propose using two Leptophlebiidae species (Habrophlebia lauta and Paraleptophlebia submarginata) as bioindicators of crayfish presence.

A round table discussion involving 25 researchers from 11 European countries was organized during the congress “European Crayfish: food, flagships and ecosystem services” (held in Poitiers, France, 26–29th October 2010) to consider current activities dealing with management of indigenous crayfish species (ICS) with special regards to their culture, restocking and conservation strategy. In the following opinion paper, we attempt to summarize best practice of current conservation strategy as well as advantages and disadvantages of applied tools and approaches for listed species or species complexes. The development of conceptual models for the protection of ICS in Europe seems to be necessary; however, currently recommended approaches of conservation strategy of ICS differ according to countries and species. The different approaches to conservation of Astacus astacus and species in the genus Austropotamobius, such as genetic diversity, captive breeding, origin and characteristics of stocking material and establishment, as well as long-term objectives of sanctuary or “ark” sites, were highlighted during the round table discussion.

International audience; A study on the genetic variability of the white-clawed crayfish was carried out based on mitochondrial cytochrome oxidase subunit I gene sequences. The sequences applied were more informative regarding white-clawed crayfish genetic variability than others previously used. Two haplotypes were found to exist in the Iberian Peninsula. The haplotypes exhibit a strong geographic subdivision (ST=0.83). One of the Iberian haplotypes was similar to north Italian haplotypes and the second differed in only one mutation. This pattern of genetic variability contrasts with those found in glacial refugial areas of France, Italy and the Balkan Peninsula. Two hypotheses on the origin of the white-clawed crayfish in the Iberian Peninsula are discussed: (i) one based on an anthropogenic origin, and (ii) a second based on a successive number of postglacial ancient and recent bottlenecks, i.e. the disjunction between Iberian and Italian populations of white-clawed crayfish species is due to competition between A. italicus and A. pallipes, in addition to the impact of crayfish plague and human translocations. New references for the white-clawed crayfish in the Iberian Peninsula were found in medieval and Arabic texts. The results show that this species has been thriving in this peninsula since ancient periods and that its indigenous status should not be questioned. Conservation action and plans should consider the low genetic diversity as a limitation for farm-raising specimens more adapted and resistant to changing environments and diseases.

Due to essentially maternal inheritance and a bottleneck effect during early oogenesis, newly arising mitochondrial DNA (mtDNA) mutations segregate rapidly in metazoan female germlines. Consequently, heteroplasmy (i.e. the mixture of mtDNA genotypes within an organism) is generally resolved to homoplasmy within a few generations. Here, we report an exceptional transpecific heteroplasmy (predicting an alanine/valine alloacceptor tRNA change) that has been stably inherited in oniscid crustaceans for at least thirty million years. Our results suggest that this heteroplasmy is stably transmitted across generations because it occurs within mitochondria and therefore escapes the mtDNA bottleneck that usually erases heteroplasmy. Consistently, at least two oniscid species possess an atypical trimeric mitochondrial genome, which provides an adequate substrate for the emergence of a constitutive intra-mitochondrial heteroplasmy. Persistence of a mitochondrial polymorphism on such a deep evolutionary timescale suggests that balancing selection may be shaping mitochondrial sequence evolution in oniscid crustaceans.

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.

1. In France, the distribution of the native white-clawed crayfish (Austropotamobius pallipes) is restricted, fragmented and mainly located in headwater streams. To conserve this indigenous species, it is necessary to characterize its habitat preferences. 2. Seven brooks in the Deux-Sevres Departement (western France) containing wild populations of A. pallipes were studied to determine its ranges of tolerance to 19 physical and chemical water parameters. On two brooks, the Sevre Nantaise and the Verdonniere, sites with and without A. pallipes were compared. Each site was sampled twice monthly from November 2002 to November 2004. 3. It was found that the white-clawed crayfish was able to tolerate wide ranges of values of some of the measured parameters. The Magot site harboured the largest A. pallipes population (17.5 crayfish m−2) and had dissolved oxygen concentrations as low as 4.93 mg L−1, while water temperature rose above 20°C for several consecutive days during summer and nitrate concentrations were always found to be above 30 mg L−1. These unusual findings could call into question the status of A. pallipes as a bioindicator of good water quality. 4. Principal component analyses (PCA) suggested that an increase of organic matter was a discriminant factor for the presence or absence of A. pallipes. In addition, sites with and without crayfish on the Sevre Nantaise brook showed showed significant differences (p

Since Charles Elton, ecologists have struggled to account for the distribution and spread of non-indigenous species (NIS). They now realize that the key factor is ‘‘opportunity’’. The more frequently and persistently a foreign plant or animal is exposed to a new environment, the better its odds of invading. Ecologists call this ‘‘propagule pressure’’ (also termed introduction effort), a composite measure expressing the number of individuals released into a region to which they are non-native. It incorporates estimates of the absolute number of individuals involved in any one release event (propagule size) and the number of discrete release events (propagule number) (Lockwood et al. 2005). Propagule pressure has rarely been documented for freshwater organisms except in fish. Duggan et al. (2006), for example, using data on aquaria in stores and historical records of fish introduced into Canadian and US waters, showed a clear relationship between their occurrence in shops and the likelihood of their introduction and eventual establishment.

Summary 1. One important goal in conservation biology is to characterise evolutionary lineages within endangered species before management decisions are taken. Here, we assess population differentiation in the freshwater crayfish Austropotamobius pallipes, an endangered species endemic to western Europe and provide valuable information for the conservation of French populations. 2. Analysis of five microsatellite loci in 44 populations revealed very different within population levels of genetic diversity (0.000

The distribution of the prawn species belonging to the genus Palaemonetes is not well defined in the Mediterranean, especially in the south of France where controversy exists concerning taxonomic identification at the species level. A molecular diagnostic technique allowed us to determine without any doubt the presence of Palaemonetes varians in the Camargue. These basic results allowed us to undertake the ecological study of the species, which took place in the context of a massive 100-year flood during the winter 1993/94, leading to a rapid and major fall in salinity that remained low until 1997, before increasing. The impacts of low salinity on the catch and life history traits of Palaemonetes varians in the lagoon were investigated from 1993 to 1999. There was a positive correlation between catches and salinity. Although we observed a major decline in recruitment between the years 1993 and 1994, reproduction parameters and growth did not seem to be affected by low salinity. A comparative study of various life history traits between Mediterranean and northern environments populations was also conducted.

Species that can act as indicators of ecosystem health offer a valuable tool in the management of natural resources. Crayfish have been suggested as bioindicators of water quality in Europe and at least one species (Austropotamobius pallipes) has been studied to determine its tolerance to pollution and its potential as a bioindicator. The genus Austropotamobius includes three crayfish species native to western Europe: A. pallipes, A. italicus and A. torrentium. It was hypothesised that because of their geographical and habitat distribution, the three Austropotamobius species might vary in their value as a bioindicator of water quality. Crayfish of species A. pallipes and A. italicus were subjected to three different treatments: hypoxia (treatment 3, approx 3 mg 1(-1) O-2), light hypoxia (treatment 2, approx 5.5 mg 1(-1) O-2) and normoxia (treatment 1, control, approx 8.5 mg 1(-1) O-2). A. torrentium crayfish were only subjected to treatment 1 (control) and 3. Variations in haemolymph sodium, calcium and chloride were used as a biomarker and concentrations were measured before and after treatment to evaluate hypoxia-induced stress. Significant differences in the concentrations of sodium between the control groups (treatment 1, normoxia) and the experimental groups (treatment 3, 3 mg 1(-1) O-2) were found in the species A. pallipes and A. torrentium. Groups of A. italicus did not show any significant difference between treatments in sodium concentrations but in chloride concentrations. Crayfish of all three species demonstrated a disruption in the ion exchange process in hypoxia, but all tolerated very low oxygen concentration for an extended period of time.

Subsequent surveys carried out from 1978 to 2003 demonstrated a high disappearance of Austropotamobius pallipes populations from the region and the alarming spread of non-indigenous species like Procambarus clarkii and Pacifastacus leniusculus. Represented by 137 populations in 1978, A. pallipes is now almost completely restricted to only one department, with 45 populations recorded, representing a decrease of 68% of the population number in 25 years, with a loss of 40% of populations in the last 6 years. Most of the disappearances of crayfish are unexplained. For the 22 others, the main reasons of the disappearance of indigenous crayfish populations were due to (1) habitat destruction by channelisation, (2) decrease of water quality by use of agricultural chemicals, (3) the construction of ponds or lakes changing the physical and chemical parameters of brooks inhabited by indigenous crayfish, (4) the introduction of non-indigenous species, mainly P. leniusculus and recently (5) crayfish plague implicated and characterized in the disappearance of two populations, two additional ones being suspected. Introduced in 1978 in Vienne department, P. leniusculus has now been found in 28 locations. First record of P. clarkii was in 1988 in Charente-Maritime department; since it has spread in most of the hydrographic basin of this department.

International audience; The loss or diminution of European crayfish populations because of both habitat deterioration and competition with alien crayfish - also responsible for the dissemination of the crayfish plague - would reduce the biodiversity at the species level. The topic "What is meant by biodiversity?" in the context of native freshwater crayfish in Europe was discussed during the Kilkenny CRAYNET meeting in order to make the point about the varied meanings of biodiversity from genes and individuals to population levels.

The photoperiodic control of sexual rest in Armadillidium vulgare was investigated using various experimental protocols. When reared in conditions of a Nanda-Hamner (i.e. resonance) protocol from their first parturial moult to their post experimental moult, females showed a weak resonance effect in sexual rest incidence. The transfer from a long day cycle to a symmetrical skeleton photoperiod--consisting of two equal light pulses per 24 h of continuous darkness--revealed the involvement of a circadian oscillatory system in the photoperiodic clock of this species. The data, obtained in the whole experiments, suggested that both oscillator and hourglass features are involved in the photoperiodic response controlling the sexual rest in Armadillidium vulgare. Moreover, when non-24-h light-dark cycles (with a long photophase) were applied, a mechanism responsible of arrest of reproduction also implied a photoperiodic counter which accumulated and added up the photoperiodic information within a sensitive period during post parturial intermoult.

Random amplified polymorphic DNA (RAPD) analysis was performed to characterize the genetic diversity of Austropotamobius pallipes, a threatened freshwater crayfish native to Europe. Four decamer primers which generated six unambiguous polymorphic bands were used to analyse crayfish from 21 populations sampled in the major part of its range. Genetic diversity within populations of A. pallipes, estimated by Shannon's diversity index, ranged from 0 to 0.446 with a mean of 0.159. A UPGMA dendrogram constructed from pairwise PhiST values between populations, revealed three clusters corresponding to populations sampled in the southern, northwestern and eastern part of its range. AMOVA analysis revealed a high genetic structure of A. pallipes populations PhiST=0.814, with 73.11% of the genetic variation distributed between these clusters. It suggests a historical geographical separation of these groups into three refugial areas, probably in the Rhine, Mediterranean and Atlantic basins during recent glaciations. The close genetic relationships between English and western French populations are in accordance with a natural postglacial origin of English populations from individuals having survived in an Atlantic refugium. However, the present results suggest that the Irish stock originated from a human translocation of individuals from an Atlantic refugium.

Variation in mitochondrial DNA (mtDNA) was surveyed, using restriction endonucleases, in the white-clawed crayfish, Austropotamobius pallipes lusitanicus, from 14 populations sampled in Spain. Four additional samples from France (1), Slovenia (1) and Italy (2) were also analysed. Among the 11 haplotypes listed, only one was detected from the 154 animals sampled from Spanish populations. This haplotype was also recorded in the Fosso di Ferfereta population (Italy). Estimates of nucleotide sequence divergence among haplotypes ranged from 0.45% to 17.4%. Interpopulational genetic relationships showed that Spanish populations were closely related to those of Fosso di Ferfereta with a small genetic distance (0.0003) found between them. AMOVA revealed that most of the genetic variance (71.97%) was attributed to variation between European regions. These results are in accordance with a drastic bottleneck event during the history of the Spanish populations. Four suggestions, based on human introduction, selection and recent or ancient historical events are discussed in relation to the lack of genetic variation in the Spanish crayfish stock.

International audience