Behavioral differences in an over‐invasion scenario: marbled vs. spiny‐cheek crayfish

New species often invade ecosystems already dominated by previous invaders. Ornamental freshwater crayfish, particularly parthenogenetic marbled crayfish (Procambarus virginalis), increasingly establish in European water bodies where they interact with resident native and non‐native species. Behavioral traits and behavioral syndromes can influence the outcome of these species interactions. The behavior of non‐native crayfish is often studied in notorious invaders but rarely in new and emerging species, although those provide the best opportunity for management. Activity, aggressiveness, and boldness have repeatedly been associated with invasion success and species displacement. Further, crayfish can adapt their behavior after they have established in the new range. We investigated whether marbled crayfish can displace the widely established spiny‐cheek crayfish (Orconectes limosus). Specifically, we compared their behavioral traits and evaluated whether these traits differ, using marbled crayfish populations from aquaria and the field and spiny‐cheek crayfish from the field. We staged agonistic encounters, measured activity levels, and recorded the response to a simulated threat of both species and both origins (field and aquarium) in laboratory trials. We found that in agonistic encounters, marbled crayfish were on average more aggressive than spiny‐cheek crayfish, even against larger opponents. Aggressiveness and activity were positively correlated, which is indicative for an aggression syndrome. Marbled crayfish from the field were less active than those from aquaria, but there was no difference in aggressiveness. Marbled crayfish often froze in response to a simulated threat, whereas spiny‐cheek crayfish reacted either offensively or defensively. These results from the laboratory illustrate potentially important behavioral mechanisms behind crayfish over‐invasions and show behavioral plasticity in a species where all known individuals are genetically identical. To better understand the invasion process in nature, the species’ reproductive biology and interactions with other members of the community should be considered. We conclude that the recent success of marbled crayfish in establishing new populations could be influenced by their behavioral flexibility and their potential to competitively persist in the presence of established invasive crayfish

Habitat use by the endangered white-clawed crayfish Austropotamobius species complex: a systematic review

Understanding habitat requirements is a key part of conserving declining species, particularly when reintroductions are planned as part of the recovery strategy. The white-clawed crayfish (Austropotamobius pallipes) has undergone severe declines across its range and is now classified by the International Union for Conservation of Nature (IUCN) as ‘endangered’. Translocation of threatened A. pallipes populations to isolated ‘Ark sites’ where threats are minimised is an increasingly used conservation tool. A full feasibility assessment of potential Ark sites, including an assessment of habitat suitability, is recommended within translocation guidelines developed by the IUCN. This literature review employed a systematic search and ‘vote counting’ approach to identify and assess the relative importance of physical habitat requirements of A. pallipes. Many habitat features were positively associated with crayfish presence, in particular: boulder substrate, trees/shading, woody debris, exposed roots, and undercut banks; and habitat use patterns varied among crayfish sexes and size classes. Ark sites should incorporate heterogeneous habitat, with as many of these features as possible, to provide both ample refugia and rich foraging areas

Interdisciplinarity to reconstruct historical introductions: solving the status of cryptogenic crayfish

Anciently introduced species can be confounded with native species because introduction pre-dates the first species inventories or because of the loss of the collective memory of the introductions. The term ‘cryptogenic species’ denotes species of unknown or unclear status (native versus non-native) in a given territory, and disciplinary approaches are often insufficient for solving their true status. Here, we follow an integrative, multidisciplinary approach to solve the status of a cryptogenic species, proposing that building on evidence from multiple disciplines can produce robust and clarifying insights. We undertook an exhaustive review of information on a putatively native crayfish (Austropotamobius italicus) in Spain. The reviewed information included taxonomy, genetics and phylogeography, history, archaeology, linguistics, biogeography, ecology, symbiotic organisms and even gastronomy and pharmacy. The knowledge produced by different scientific disciplines converges to indicate that A. italicus is a non-native species in Spain. Historical documents even identify the first introduction event: crayfish were shipped from Italy to Spain in 1588 as a diplomatic gift from Francesco I de' Medici to King Philip II of Spain. Previous discussions on the status of A. italicus focussed on inconclusive and often confusing genetic results and excluded the rich and clarifying evidence available from other approaches and disciplines. Interdisciplinarity is an often-invoked but rarely implemented practice in an academic environment that increasingly promotes narrow-focussed specialization. Our review shows that the integration of disciplines can surpass disciplinary approaches in solving scientific controversies. Our results have straightforward implications for strategies to conserve biological diversity in Spain and Europe, urging a debate on the appropriateness of devoting conservation efforts to non-native species.Peer Reviewe

Slovak section of the Danube has its well-established breeding ground of marbled crayfish Procambarus fallax

Established populations of the non-indigenous parthenogenetically reproducing marbled crayfish Procambarus fallax f. virginalis have been recently reported from various European countries. The colonised sites are usually lentic and relatively isolated from major watercourses and in such cases the immediate threat of the spread of this taxon is limited. Here we report on a marbled crayfish population that is likely to become a seed for colonisation of the Danube in Slovakia. It is located in a channel within the Slovak capital Bratislava in the immediate vicinity of a pumping station that occasionally releases significant amounts of water into the side arm of the Danube. The population is well established with a high growth potential: numerous adult marbled crayfish individuals were observed at the site in September and October 2016 and the progeny (eggs or first two developmental stages) of 27 berried females exceeded 11 000 individuals. The maximum observed fecundity per female reached 647 juveniles in the second developmental stage. The Danube side arm downstream of the pumping station harbours a population of spiny-cheek crayfish Orconectes limosus infected with the crayfish plague pathogen Aphanomyces astaci. We presume that marbled crayfish is already present below the pumping station and it is just a matter of effort and time until it is discovered. The investigated specimens of marbled crayfish were found free of A. astaci, but horizontal transmission from infected spiny-cheek crayfish may be expected, as well as further spread of marbled crayfish in the Danube

Annelid symbiont assemblage and European stone crayfish − a deterministic relationship with implications for conservation management

The protected European stone crayfish, Austropotamobius torrentium, is a host to epibionts inhabiting its exoskeleton. Despite evidence of the close association of these epibionts to the crayfish and the beneficial services provided for the crayfish, the main factors influencing their occurrence, distribution and abundance are still poorly understood. In order to investigate the stone crayfish epibiont community, the ecological requirements of individual species, and aspects of the host-epibiont relationship we collected data at several crayfish populations in Austria, Switzerland and Germany. At each location, we recorded the epibiont position on the crayfish host along with a number of biotic and abiotic parameters. Apart from recording the Branchiobdella species B. parasita, B. hexadonta, B. pentadonta and B. balcanica, we detected for the first time the polychaete Hystricosoma chappuisi in the European Alps. Species-specific biogeographical and habitat factors such as river catchment borders, crayfish length, water temperature and nutrients concentration were identified to be important for the occurrence and abundance of epibionts. Branchiobdella species were strongly linked to certain host body areas, providing evidence for the existence of different functional traits within the annelid assemblage. With this study we demonstrate that the crayfish–epibionts relationship includes structural and functional complexities that can be important for defining management units in future conservation policies. Due to benefits for the mutualistic relationship, restocking and reintroduction actions are likely to be more successful, if ecological requirements of both the host and the epibiont species are considered

World of Crayfish™: a web platform towards real-time global mapping of freshwater crayfish and their pathogens

Freshwater crayfish are amongst the largest macroinvertebrates and play a keystone role in the ecosystems they occupy. Understanding the global distribution of these animals is often hindered due to a paucity of distributional data. Additionally, nonnative crayfish introductions are becoming more frequent, which can cause severe environmental and economic impacts. Management decisions related to crayfish and their habitats require accurate, up-to-date distribution data and mapping tools. Such data are currently patchily distributed with limited accessibility and are rarely up-to-date. To address these challenges, we developed a versatile e-portal to host distributional data of freshwater crayfish and their pathogens (using Aphanomyces astaci, the causative agent of the crayfish plague, as the most prominent example). Populated with expert data and operating in near real-time, World of Crayfish™ is a living, publicly available database providing worldwide distributional data sourced by experts in the field. The database offers open access to the data through specialized standard geospatial services (Web Map Service, Web Feature Service) enabling users to view, embed, and download customizable outputs for various applications. The platform is designed to support technical enhancements in the future, with the potential to eventually incorporate various additional features. This tool serves as a step forward towards a modern era of conservation planning and management of freshwater biodiversity

World of Crayfish™: a web platform towards real-time global mapping of freshwater crayfish and their pathogens

Freshwater crayfish are amongst the largest macroinvertebrates and play a keystone role in the ecosystems they occupy. Understanding the global distribution of these animals is often hindered due to a paucity of distributional data. Additionally, non-native crayfish introductions are becoming more frequent, which can cause severe environmental and economic impacts. Management decisions related to crayfish and their habitats require accurate, up-to-date distribution data and mapping tools. Such data are currently patchily distributed with limited accessibility and are rarely up-to-date. To address these challenges, we developed a versatile e-portal to host distributional data of freshwater crayfish and their pathogens (using Aphanomyces astaci, the causative agent of the crayfish plague, as the most prominent example). Populated with expert data and operating in near real-time, World of Crayfish™ is a living, publicly available database providing worldwide distributional data sourced by experts in the field. The database offers open access to the data through specialized standard geospatial services (Web Map Service, Web Feature Service) enabling users to view, embed, and download customizable outputs for various applications. The platform is designed to support technical enhancements in the future, with the potential to eventually incorporate various additional features. This tool serves as a step forward towards a modern era of conservation planning and management of freshwater biodiversity