Exploring the effects of neurotransmitters on the swimming behaviour of crinoid larvae

The doliolaria larvae of most crinoids are lecithotrophic larvae that, before settlement and methamorphosis, disperse in the water column, utilising ciliary bands for swimming. However, the precise modulation of this behaviour remains elusive. Recent studies have identified the expression of various neurotransmitters, including monoamines and neuropeptides, in this larval stage. These molecules hold potential as drivers of swimming behaviour in doliolaria larvae. To investigate this possibility, we established a specific behavioural assay to assess the effects of neurotransmitters/neuropeptides on swimming activity of in the doliolaria of Antedon mediterranea. Larvae were placed in 24-well plates containing filtered artificial sea water, and their baseline behaviour was video recorded under a stereomicroscope for two minutes. Subsequently, a neurotransmitter/neuropeptide was introduced , allowing one minute for dissolution and absorption by the larvae. The larvae were then recorded for an additional two minutes. Ongoing work with video tracking algorithms aims to characterise parameters such as overall distance, speed, and path type (straight or curved) to identify potential differences in larval movement pre- and post- treatment and also among different neuromodulators. Unraveling the modulation of doliolaria swimming by neurotransmitters will enhance our understanding of this crucial stage in crinoids, wherein the larvae must disperse before settling to the substrate and transitioning to the sessile pentacrionid stage. Moreover, these findings will have broader implications for understanding crinoid nervous system development, providing a valuable baseline for comparative studies among echinoderms.