Abstract
Parasites display a wide range of behaviours that are frequently overlooked in favour of host responses. Understanding these behaviours can improve parasite control through a more precise application or development of new behaviour-based strategies. In aquaculture fish lice are an ongoing problem, infections reduce fishery production and control options are limited. Fish lice are distinct in their ability to survive and swim off hosts, allowing the transmission to multiple fish hosts across their lifespan. Here we assessed the off-host behaviour of Argulus foliaceus (a freshwater fish louse) and observed a diurnal rhythmical pattern in their behaviour. This pattern was lost when lice were exposed to constant darkness, indicating that the behaviour is not endogenously driven. Males were consistently active in light with reduced activity in darkness. In contrast, females were active during light and dark phases with peak activity at the start of dark periods. A. foliaceus was also strongly attracted to a light stimulus, preferring white- and blue-coloured lights over green- or red-coloured lights. Light is a strong driver of fish louse activity and could be used to trap parasites. Aquaculture light regimes could also be altered to reduce parasite attraction and activity.
Highlights
Parasites are a fundamental component of ecosystems; practically all known species carry parasites and food webs can be dominated by their presence (Marcogliese and Cone 1997; Poulin and Morand 2000; Lafferty et al 2006; Dobson et al 2008)
Argulus foliaceus when maintained under 12:12 LD conditions (RAIN P =
Under 12:12 LD, overall average swimming speed of A. foliaceus did not differ among sexes (0.77 and 0.83 cm/s for males and females respectively, general linear mixed model (GLMM) P = 0.591), when directly comparing ZT timepoints females had a significantly higher swim speed at ZT12 (7pm when the lights turn off; GLMM P = 0.008; Fig. 2)
Summary
Parasites are a fundamental component of ecosystems; practically all known species carry parasites and food webs can be dominated by their presence (Marcogliese and Cone 1997; Poulin and Morand 2000; Lafferty et al 2006; Dobson et al 2008). In addition to their ecological importance, parasitic infections play a critical role in the global health of humans and both domesticated and wild species. Parasites utilise a range of stimuli (such as chemical, thermal, mechanical and visual), often in combination to locate hosts and assess their suitability (Van Leerdam et al 1985; Ashton et al 1999; Bailey et al 2006; Mordue (Luntz) and Birkett 2009)
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