Serotonin, octopamine, and the clinging behavior induced by the parasite Polymorphus paradoxus (Acanthocephala) in Gammarus lacustris (Crustacea)

Abstract

Gammarus lacustris infected with cystacanths of Polymorphus paradoxus display an abnormal behavior. They respond to disturbance by swimming to the surface and clinging to a solid object (W. M. Bethel and J. C. Holmes. 1973. J. Parasitol. 59: 945–956). Uninfected gammarids injected with serotonin (1–20 μg/50 mg) but not other neurotransmitters also responded to mechanical stimulation by clinging, but the response lasted for a shorter time than in infected gammarids. Octopamine suppressed the clinging response in infected gammarids for several hours. The results suggest that cystacanths of P. paradoxus modulate the behavior of gammarids through the alteration of neural activity in some serotonin-sensitive or serotonergic central pathway, probably one involved in precopulatory clinging in male amphipods.

Conflict between parasites with different transmission strategies infecting an amphipod host

“…To test geotaxis, animals were individually placed in a graduated 500 ml measuring cylinder. The top of the water was covered with a small net that animals could cling onto (increased clinging is a component of the parasitic-induced behavioural changes) (Bauer et al 2005;Helluy & Holmes 1990). To avoid an effect of direct light, the measuring cylinder was placed on a black plastic sheet and covered by a similar sheet.…”

Ecophysiological studies of Corophium volutator (Amphipoda) infested by microphallid trematodes

“…Further studies will be needed to broaden our knowledge regarding this problem. Parasitism is often accompanied by various changes of behaviour (Holmes & Bethel 1972, Helluy & Holmes 1990, Poulin 1995. Mouritsen & Jensen (1997) found increased surface activity of infested Corophium volutator.…”

Parasite-induced alterations of sensorimotor pathways in gammarids: collateral damage of neuroinflammation?

“…The similarity between the flexed posture induced by P. paradoxus in G. lacustris (Fig.1A) and the flexed abdominal posture induced by serotonin in lobsters (Livingstone et al, 1980) prompted a study in which serotonin was administered to uninfected G. lacustris to assess the effects of the monoamine in gammarids (Helluy and Holmes, 1990). Serotonin injected into the hemocoel of uninfected G. lacustris elicited the photopositive, clinging and skimming responses to disturbance characteristic of P. paradoxus-infected individuals (Helluy, 1988;Helluy and Holmes, 1990).…”

“…Serotonin injected into the hemocoel of uninfected G. lacustris elicited the photopositive, clinging and skimming responses to disturbance characteristic of P. paradoxus-infected individuals (Helluy, 1988;Helluy and Holmes, 1990). The behavioral effects induced by the most effective hemolymph concentration (10µg per individual weighing about 100mg) culminated about 1h after injection.…”

“…The behavioral effects induced by the most effective hemolymph concentration (10µg per individual weighing about 100mg) culminated about 1h after injection. Other neurotransmitters were tested in an attempt to reproduce the clinging behavior in uninfected gammarids but only serotonin had an effect; GABA, noradrenaline, dopamine and octopamine, at similar concentrations, failed to induce the clinging behavior in uninfected gammarids (Helluy and Holmes, 1990). In lobsters, the biogenic amine octopamine produces an extended posture (Livingstone et al, 1980).…”