Development of a two-current choice flume behavioural bioassay for juvenile Panulirus ornatus response to moulting cues

Abstract

Characterising crustacean behaviour in response to conspecific chemical cues contributes to our evolving knowledge of the drivers of their social behaviour. There is particular interest in understanding the chemical and behavioural mechanisms contributing to cannibalism at ecdysis, as this behaviour substantially limits culture productivity of several commercially important crustaceans. Before investigating the role of chemoreception in cannibalism of moulting crustaceans, we must investigate its role in detecting moulting conspecifics. Here we use a two-current choice flume to observe juvenile tropical rock lobster (Panulirus ornatus) behavioural response to conspecific moulting cues and identifying attracted and avoidant behaviours correlating to moult stage and social relationship. Observed cue preferences show inter-moult juveniles are attracted to the moulting cues of lobsters to which they are socially naïve. In contrast, post-moult and inter-moult juveniles avoid the moulting cues of individuals whom they are socially familiar with. Average speed and total distance travelled by lobsters increases in response to conspecific moulting cues. This study demonstrates the suitability of a two-current choice flume for behavioural assays in P. ornatus and characterises clear behavioural patterns in juveniles exposed to conspecific moulting cues. This provides important framework for understanding the role of chemical communication in eliciting cannibalism.

Tropical rock lobster (Panulirus ornatus) uses chemoreception via the antennular lateral flagellum to identify conspecific ecdysis

“…( c ) Demonstration of laminar flow in choice arena using red and blue dye, flow rate of 2 L min −1 . Figure previously published by Kelly 10 . …”

“…Design of the two-current choice flume was based on recommendations by Jutfelt, 2017 31 and detailed in Kelly 10 (Fig. 1 a,b).…”

“…The experiment followed the procedures of Kelly 10 in which a pre-moult juvenile is placed in a randomly assigned flume header tank and an inter-moult juvenile who is socially naïve to the pre-moult lobster is placed in the choice arena. Time-lapse footage (1 fps) of both the header tank and choice arena is captured overnight to identify the exact time lobsters moult in the header tank.…”

“…Chemical communication is broadly used by crustaceans to interact with each other and their environment 8 , 9 . Chemical cues released by moulting crustaceans are recognised by conspecifics, indicating that chemoreception plays a key role in mediating cannibalism of post-moults 10 , 11 . Identifying the sensory pathways responsible for recognising moulting conspecifics is therefore essential to our understanding of cannibalistic behaviour in juvenile P. ornatus.…”

“…This provides more information than other methods, such as Y-mazes and shuttle box systems, where results are often binary. Previous research has established two-current choice flumes to be a suitable tool to measure behavioural response in P. ornatus juveniles 10 . Kelly 10 identified a preference response to conspecific moulting cues in familiar and naïve pairings, providing an effective behavioural assay, which is used here to assess the role of olfaction in detecting conspecific moulting cues.…”