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English

Abstract Many freshwater ecosystems are at risk due to the detrimental impacts of increasing salinity. This is particularly true for coastal freshwater wetlands where increasing tropical cyclone intensity and sea level rise are threatening these habitats. Little is known, however, about salinity tolerances of many coastal freshwater species. The hammock crayfish, Procambarus lunzi (Hobbs), for example, inhabits coastal hammock islands and maritime forested wetlands in South Carolina, USA. Procambarus lunzi and other native crayfish are also at risk due to invasion by the red swamp crayfish, Procambarus clarkii (Girard), a species with a high salinity tolerance. The objective of this study was to document P. lunzi’s response to chronic salinization under field conditions and to test acute salinity tolerances of two native and one invasive crayfish species under experimental conditions. Under field conditions, monthly sampling of a mesohaline wetland (range: 0.5-6.1 psu) revealed the presence of P. lunzi throughout the year. Seven-day experimental trials on acute tolerance revealed high survival probabilities (>50%) of all three species at 30 psu. These results show high acute salinity tolerance for multiple crayfish species, but some indications that chronic salinization may be detrimental, demonstrating that salinization and non-native species may threaten coastal biodiversity.

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Abstract Freshwater Astacidea evolved from marine Astacidea, giving rise to four families with remarkable diversity. The Red Swamp Crayfish, Procambarus clarkii (Astacoidea: Cambaridae), is the most economically utilized and invasive species. The morphology of the postembryonic development of this species is described and illustrated for comparison with other Astacidea members. The evolutionary history of the rudimentary vestigial line and filaments on the epipodal plate was examined. Abbreviation of postembryonic stages and the development of telson segmentation of members of the freshwater Astacidea were compared with marine Astacidea. The abbreviation of the larval stage may be related to the phylogenetic relationships among Astacidea members in marine and freshwater environments. The body size of each postembryonic stage was compared among species from each of the four families. Largersized Astacidae and Cambaroididae become independent at Stage II, while smaller-sized Cambaridae and Parastacidae leave maternal care at Stage III. The smallest juveniles belong to Cambaridae in North and Middle America, contributing to the highest species diversity among the four families. Smaller size led to a larger number of juveniles and an extended maternal care period that was related to the higher survival of juveniles. It is proposed that the higher fertility contributed to the evolutionary success of the Cambaridae.

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Abstract The Big Water Crayfish, Cambarus robustus, is native to several eastern U.S. states and Ontario, Canada. Cambarus robustus possesses several traits that make it a potential surrogate for federally listed species, such as the Big Sandy Crayfish, Cambarus callainus, and the Guyandotte River Crayfish, Cambarus veteranus. Basic husbandry information, like optimal temperature, and shelter requirements, have yet to be investigated for most Cambarus species. Therefore, to create a protocol for shelter requirements and preferences for federally listed Cambarus species, we conducted a shelter preference study with C. robustus. Thirty-one crayfish were placed in two treatments where opportunities to burrow underneath natural shelters, clear acrylic shelters, or tinted acrylic shelters were presented. Clear and tinted acrylic shelters are beneficial for investigators as they allow for monitoring of behavior and health without disrupting the crayfish. Each of the two trials lasted 24 hours and were video recorded to monitor behavior and shelter use. Our results suggest that C. robustus will use all shelter types, although natural shelters were occupied more frequently than acrylic shelters. Sex and size had minimal or no influence on shelter use. Future studies should continue to investigate husbandry and rearing techniques for Cambarus spp. and other species where propagation and head-starting efforts will commence.

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Abstract Crayfishes in the Genera Procambarus, Pacifastacus, Faxonius, Cherax, and Cambarellus were evaluated for their potential impacts and overall invasion risk in Ontario. Of the ten species evaluated, six have been found to have potential high impact. Crayfishes in the genus Procambarus pose the greatest risk as they have the greatest potential for negative impacts on native species and habitats. Three of the species have already recently been detected in Ontario. A single population of P. virginalis in the city of Burlington is the first of this species in Canada and North America. Procambarus acutus appears to be well-established in both the Lake Erie and Lake Huron watersheds while P. clarkii has also been most recently reported in Southern Ontario. The invasive Faxonius rusticus is well established and still expanding in Ontario and has displaced native crayfishes in large parts of the province while F. limosus appears poised to expand into Ontario. It is recommended that a different set of regulations be drafted and applied to all introduced species in Ontario, including the already present species (F. rusticus, F. obscurus, P. acutus, and P. virginalis) as well as any future introduced species of crayfish. Education and outreach for anglers, naturalists, and the general public is recommended as an effective way of preventing the introduction and spread of invasive crayfishes. For crayfish which are already well established or recently detected in Ontario, management efforts should focus on containment of any further spread. Citizen science contributions to on-line databases, such as iNaturalist and EDDMapS, are also crucial in tracking introduced species in the province. Priority should be given to safeguarding remnant populations of native crayfishes, especially in areas dominated by introduced species. Headwaters of streams and rivers, as well as isolated lakes and small wetlands, are well suited for this type of conservation management.

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