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The impact of invasive crayfish on aquatic ecosystems

James, Joanna 2015. The impact of invasive crayfish on aquatic ecosystems. PhD Thesis, Cardiff University.
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Crayfish are keystone species and ecosystem engineers that affect the structure and function of aquatic ecosystems. Whilst ecological impacts are caused by crayfish in their native range, non - native crayfish species typically have a greater ef fect on some other aquatic organisms and ecosystem processes (Chapter 2). Crayfish are extremely successful invaders that often cause declines in native cra yfish (Chapter 3). Of the 7 non - native crayfish species in the UK, the signal crayfish ( Pacifastacus leniusculus ) is currently the most widespread (Chapter 3). Field and laboratory data, however, suggest that in parts of the UK signal crayfish are being outcompeted by more recently introduced virile crayfish ( Orconectes cf. virilis ) (Chapter 4). Non - native crayfish also threaten native crayfish through disease, notably crayfish plague ( Aphanomyces astaci ), transmission. Whilst non - native North American crayfish are largely resistant to A. astaci , infection in susceptible native European species is usually lethal. Within this study 23 signal crayfish populations were screened for A. astaci and 13 were infected (Chapter 5). Virile crayf ish from the UK were also infected with A. astaci , and therefore should also be considered as a transmission pathway for this pathogen in the UK (Chapter 6). Whilst the majority of studies on crayfish symbionts are focused on A. astaci , crayfish host a wid e range of micro and macro - parasites. One group of particular interest are branchiobdellidans (Annelida: Clitellata). Two species of these ectosymbionts, Xironogiton victoriensis and Cambarincola aff. okadai , were recently discovered on invasive signal cra yfish in the UK (Chapter 7). Owing to their abilities to survive for extended periods off the host and reproduce rapidly both species have a high invasion potential in the UK (Chapter 8). Laboratory experiments show that signal crayfish infested with X. victoriensis were less aggressive and poorer foragers than uninfested c rayfish , therefore these symbionts may influence signal crayfish invasion dynamics (Chapter 9)

Item Type: Thesis (PhD)
Date Type: Publication
Status: Unpublished
Schools: Biosciences
Subjects: Q Science > QL Zoology
Funders: Natural Resources Wales, Cardiff University
Date of First Compliant Deposit: 10 April 2016
Last Modified: 14 Dec 2020 02:31

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