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Title: The behavioural function of pheromones in crayfish
Author: Berry, Fiona Catherine
ISNI:       0000 0004 2676 7760
Awarding Body: University of Hull
Current Institution: University of Hull
Date of Award: 2008
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Pacifastacus leniusculus and Procambarus clarkii are highly invasive freshwater crayfish and are having detrimental impacts on native species and habitats throughout Europe. The application of pheromone baits have been proposed as a way of increasing trap efficiency for population control, however the chemical identity of crayfish pheromones is unknown. An incomplete understanding of chemical communication has delayed progress in the development of appropriate bioassays. This thesis therefore focused on researching the natural context of chemical signalling by crayfish, including signal delivery and receiver response. Urine release by male and female crayfish was found to coincide with aggressive behaviours rather than reproductive behaviours. Female urine release was essential for initiating mating, with males detecting female receptivity by spying on hormones and metabolites released with threat signals. Physiological indicators of reception included a brief cardiac and ventilatory arrest followed by an increase in rate. Both behavioural and physiological responses formed the basis of a novel assay design. During courtship male crayfish do not appear to advertise by urine signals. This raised the question of whether chemical signals were important for female assessment of the quality of size-matched males. When given a free choice, females could not distinguish dominant and subordinate males through chemical signals alone. This suggests that females either use other criteria (e.g. size) for mate choice or perform cryptic postcopulatory mate choice. Blocking natural urine release of crayfish, which had previously fought to establish dominance, and artificially introducing urinary signals proved an effective bioassay for investigating the mechanisms of dominance hierarchy formation. Urine from the dominant male was the key factor in establishing dominance relationships. In the absence of dominant urine, subordinate males were less likely to retreat from aggressive bouts and fights were more intense. The mechanisms of signal delivery during agonistic encounters were investigated by measuring ventilatory activity. Increased ventilation rate was associated with highly aggressive behaviours and urinary signalling. This indicated crayfish create gill currents to disperse signals and increase transfer efficiency from sender to receiver. This thesis sheds light into the mechanism of chemical communication in crayfish and provides the basis for future bioassay guided purification of crayfish pheromones.
Supervisor: Breithaupt, Thomas Sponsor: Natural Environment Research Council (Great Britain)
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Biology