The International Journal of Developmental Biology

Int. J. Dev. Biol. 51: 307 - 313 (2007)

https://doi.org/10.1387/ijdb.062195gz

Vol 51, Issue 4

Serotonin involvement in the metamorphosis of the hydroid Eudendrium racemosum

Original Article | Published: 1 May 2007

Giuliana Zega*, Roberta Pennati, Arianna Fanzago and Fiorenza De Bernardi

Dipartimento di Biologia, Sez. Zoologia S/N, Università Statale di Milano, Milan, Italy

Abstract

Hydroid planulae metamorphose in response to an inducing external stimulus, usually a bacterial cue. There is evidence that neurotransmitters participate in the signal transduction pathway of hydroid metamorphosis. Eudendrium racemosum is a colonial hydroid common in the Mediterranean Sea. It lacks the medusa stage and the planulae develop on female colonies during the fertile season. In this work, serotonin (5-HT) was localized in some planula ectodermal cells. Co-localization of serotonin and beta-tubulin suggested that 5-HT was present in sensory nervous cells and in different ectodermal cells. To investigate the role of neurotransmitters in metamorphosis, E. racemosum planulae were treated with serotonin and dopamine and with agonists and antagonists of the corresponding receptors. Serotonin and a serotonin receptor agonist induced metamorphosis, while a 5-HT receptor antagonist inhibited it. Dopamine and all dopaminergic drugs used did not show any significant effect on the onset of metamorphosis. Results from this work showed that 5-HT could stimulate metamorphosis in E. racemosum planulae in the presence of a natural inducer. A mechanism by which this neurotransmitter could act in this phase is proposed.

Keywords

neurotransmitter, cnidaria, 5-HT, planula, beta-tubulin

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