Localization of some neurotransmitters during developments in hydroidomedusae

Area of Science:

• Neurobiology
• Evolutionary Biology
• Marine Biology

Background:

• Cnidarian neurotransmission primarily relies on peptidergic pathways.
• The role of cholinergic neurotransmission in cnidarians remains uncertain, unlike its established roles in other animals.

Purpose of the Study:

• To investigate the presence and distribution of cholinesterase (ChE) activity, acetylcholine receptors, biogenic amines, and peptide-like molecules in hydroidomedusan species.
• To explore the evolutionary origins and potential functional diversification of these neurochemical messengers.

Main Methods:

• Histochemical and immunohistochemical techniques were employed.
• Study included various developmental stages of hydroidomedusan species with diverse reproductive and developmental patterns.
• Detection of ChE activity (AChE, PrChE, BuChE), acetylcholine receptors, biogenic amines, and FMRF amide/VIP-like immunoreactivities.

Main Results:

• Cholinesterase (ChE) activity was predominantly observed in developing or juvenile cnidarian structures.
• Biogenic amines were detected across all studied developmental stages.
• Peptide-like immunoreactivities were mainly localized in differentiated structures.

Conclusions:

• The findings support the early evolutionary emergence of investigated chemical messengers in cnidarians.
• Observed distribution patterns of neurochemical markers correlate more with life cycle similarities than phylogenetic relationships.
• Potential functional divergence of these messengers during cnidarian evolution is suggested.