Serotonergic modulation of social status-dependent behavioural plasticity of the crayfish avoidance reaction

Abstract

Small crayfish usually showed escape-like dart responses to mechanical stimulation of the tailfan. Following agonistic bouts with conspecifics, dominant crayfish showed a defensive-like turn response to the same sensory stimulus. During the dart response, both uropods closed and animals walked forwards with the abdomen extended, while during the turn response the uropod on the stimulated side opened and animals turned towards the stimulus source with the abdomen frequently flexed. Using an isolated nerve cord preparation, we found that the spike activities of both the abdominal postural and uropod motor neurones in response to sensory stimulation of the exopodite reversed in dominant animals. In naive and subordinate animals, extensor motor neurones were excited and antagonistic flexor motor neurones inhibited in response to sensory stimulation. Furthermore, the spike frequency of uropod closer motor neurones increased while that of the antagonistic opener motor neurones decreased. By contrast, in more than half of the dominant animals, flexor and opener motor neurones showed excitatory responses while extensor and closer motor neurones showed inhibitory responses to the same sensory stimulation. This reverse of activity of the abdominal postural and uropod motor neurones was also observed when serotonin of more than 12.5 μM in concentration was applied.

The effects of quality of shelters and prior residence on Marmorkrebs (marbled crayfish)

“…This result is similar to a winner effect that winning small animals in previous fights tend to win against large animals in the subsequent fights (Momohara et al, 2013). A decrease in cAMP level in the brain mediated by serotonin induces the winner effect (Momohara et al, 2015(Momohara et al, , 2016. At the moment, the neurochemical and physiological bases underlying the residence effect are unclear, but certain biogenic amines like serotonin could underlie this effect.…”

Cyclic AMP‐regulated opposing and parallel effects of serotonin and dopamine on phototaxis in the Marmorkrebs (marbled crayfish)

“…Biogenic amines are known to modulate animals’ physiological conditions and affect feeding, sexual, postural and aggressive behaviours in a wide range of arthropods, as well as vertebrate animals (Livingstone et al ., ; Weiger, ; Kravitz, ; Lesch & Merschdorf, ; Kravitz & Huber, ; Momohara et al ., , ). They also affect neural activity underlying learning and memory (Hammer & Menzel, ; Kandel, ; Schwaerzel et al ., ; Araki et al ., ; Menses & Liy‐Salmeron, ).…”

Role of cAMP signalling in winner and loser effects in crayfish agonistic encounters

“…Kravitz () first showed that postures resembling aggressive or submissive stance are induced by injection of serotonin or octopamine. Subsequent work has shown that winner and loser effects are also mimicked by administration of serotonin and octopamine (Momohara et al ., , ). As serotonin and octopamine receptors mostly belong to a superfamily of G‐protein coupled metabolic receptors (Hoyer et al ., ; Gerhardt et al ., ; Roeder, ; Spitzer et al ., ), their downstream second messengers could mediate winner and loser effects.…”