Abstract
The effects of antidepressants in the environment are starting to generate considerable interest due to the fact that neurotransmitters influence a range of biological processes. Crypsis is an important behavioural and physiological response in many crustaceans modulated by monoamine and pigment dispersing/concentrating hormones. This study aimed to develop a test methodology and investigate the effects of the selective serotonin reuptake inhibitor (SSRI), fluoxetine, on a chromatophore index and overall carapace ‘darkness’ in the common sand shrimp Crangon crangon. Adult shrimp were exposed for either 1 h, 1 day or 1 week across a range of nominal fluoxetine concentrations (10 ng/L, 100 ng/L and 1000 ng/L) and the chromatophore index or carapace percentage ‘darkness’ was recorded following 30 min on white and black substrates. These experiments were repeated three times using different specimens. Animals became significantly darker (~20%) on darker background and lighter on light backgrounds as one might expect. However, time periods over which the animals were recorded had a significant impact on the colouration suggesting habituation to laboratory conditions. Fluoxetine exposure came up as a significant factor in two of the three trials for the chromatophore index but the results was inconsistent between trials. There was a high degree of correlation between the chromatophore index and the percentage darkness analyses however, there was no significant effects for fluoxetine exposure with the percentage darkness data. We conclude that the effects on antidepressants on colour change remain inconclusive from these experiments and we discuss potential areas to improve the repeatability of the experiments.
Highlights
The effects of some pharmaceuticals on the environment have received considerable attention over past years due to effects on wildlife observed at the individual and population level (Halling-Sørensen et al 1998; Fent et al 2006; Brausch et al 2012; Arnold et al 2014; Saaristo et al 2018)
ImageJ was used to calculate the percentage area of the 2nd abdominal segment covered by chromatophore cells for trials 2 and 3 (Table 1)
The ability to change colour is very important in terms of survival from predation and signalling to fellow conspecifics aggression or mate status (Stevens and Merilaita 2008)
Summary
The effects of some pharmaceuticals on the environment have received considerable attention over past years due to effects on wildlife observed at the individual and population level (Halling-Sørensen et al 1998; Fent et al 2006; Brausch et al 2012; Arnold et al 2014; Saaristo et al 2018). Environment has grown steadily over the past decade due to the fact that neurotransmitters, with which the drugs are designed to interact, control a large variety of biological processes (Guler and Ford 2010; Fong and Ford 2014). Recent studies have highlighted effects at very low and environmentally relevant concentrations (Di Poi et al 2013; De Lange et al 2006; Bossus et al 2014; Fong and Hoy 2012; Fong and Molnar 2013). Standard environmental toxicology testing focuses upon mortality, growth and reproductive based endpoints and whilst these have some links with behaviour, these tests would not pick up non-standard endpoints such as disrupted colour change. The ability of an organism to change colour and adapt to its background is critical to its survival, it is important to develop test methods that can determine if pollutants can impact these novel endpoints.
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