Invasive Species Compendium

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Abstract

Effects of Schistocephalus solidus infection on brain monoaminergic activity in female three-spined sticklebacks Gasterosteus aculeatus.

Abstract

The three-spined stickleback Gasterosteus aculeatus is an intermediate host of the tapeworm Schistocephalus solidus. Changes in predator avoidance, foraging and shoaling behaviour have been reported in sticklebacks infected with S. solidus plerocercoids, but the mechanisms underlying parasite-induced behavioural changes are not understood. Monoamine neurotransmitters are involved in the control of behaviour and central monoaminergic systems are sensitive to various stressors. Thus, the behavioural effects of S. solidus infection might be a reflection of changes in brain monoaminergic activity in the stickleback host. The three-spined sticklebacks were caught on 18 and 19 November 1999 in Öresund, Sweden. The concentrations of 5-hydroxytryptamine (5-HT), dopamine (DA), norepinephrine (NE) and their metabolites 5-hydroxyindoleacetic acid (5-HIAA), homovanilic acid (HVA) and 3-methoxy-4-hydroxyphenylglycol (MHPG) were measured in the telencephalons, hypothalami and brainstems of parasitized and non-parasitized female sticklebacks held in the laboratory. The ratios of 5-HIAA:5-HT were significantly elevated in both the hypothalami and brainstems of infected sticklebacks. The concentrations of 5-HT and NE were significantly reduced in the telencephalons of infected fish compared with controls, but there was no elevation of metabolite concentrations. The results are consistent with chronic stress in infected fish, but may also reflect other alterations of neuroendocrine status resulting from parasite infection.