Dynamic colour change as a signalling tool in bluelined goatfish (Upeneicthtys lineatus)

Abstract

Many animal species can rapidly change their body colouration and patterning, but often the ecological drivers of such changes are unknown. Here, we explored dynamic colour change in the bluelined goatfish, Upeneichthys lineatus, a temperate marine teleost species. Upeneichthus lineatus can change in a matter of seconds, from a uniform white colour to display prominent, vertical, dark red stripes. Initial observations suggested that rapid colour change in U. lineatus was associated with feeding and may act as a signal to both conspecifics and heterospecifics that are frequently observed to follow feeding goatfish. Field observations of the colour and behaviour of individual U. lineatus were collected to (1) document the repertoire of behaviours that U. lineatus displays and categorise associated colour patterns; (2) quantify the speed of dynamic colour change; (3) establish the context in which U. lineatus changes colour and pattern; and (4) test whether the behaviour of follower fishes is influenced by colour patterning or specific behaviours of the focal goatfish. We found that U. lineatus changed colouration from white to the red banded pattern in less than 10 s. The key driver of rapid colour change in U. lineatus was feeding, particularly when the fish fed with its head buried in sediment. Conspecific followers were most likely to be white in colour and adopt searching behaviour, regardless of the focal fish colour or behaviour. Other species of follower fish spent significantly more time following U. lineatus that were displaying dark red stripes when searching or eating, implying the red stripes may be an interspecific signalling mechanism. Our findings indicate that rapid colour change in teleost fish may be used for social communication and may provide U. lineatus with increased protection from predation when feeding via a safety‐in‐numbers approach.

A fish can change its stripes: investigating the role of body colour and pattern in the bluelined goatfish

“…Without stereo-cameras, we were unable to accurately assess fish size although many conspecifics appeared smaller than our model fish. A previous study found that conspecifics will regularly adopt a white colouration when following focal goatfish ( Tosetto, Hart & Williamson, 2023 ), suggesting that red patterning may also be a dominance signal in U. lineatus . These findings are indicative of social learning within U. lineatus populations and further studies that explore the role of colour in this system are warranted.…”

“…The quality of the signal, whether chromatic or achromatic, could be influenced by the intensity of the banding. The rapid colour change of U. lineatus from white to dark red is continuous, shifting from a white to paler red when searching for food and the adoption of the dark red colouration when actively feeding ( Tosetto, Hart & Williamson, 2023 ). It is possible that the intensity or saturation of the dark red bands may indicate the food patch quality.…”

“…Video footage was assessed using two different methods: (1) abundance and behaviour of individual conspecific or heterospecific fishes around the different colour models; and (2) the total time spent by conspecifics and associated heterospecific fish around each colour morph (time-in-view; TiV). Nine fish were identified as key heterospecifics; those species that were previously identified ( Tosetto, Hart & Williamson, 2023 ) and those that had interacted most with our model fish in this study. Heterospecifics were identified using a field guide to fishes in southern Australia ( Hutchins & Swainston, 1986 ).…”

“…The bluelined goatfish ( Upeneichthys lineatus ) occurs along the southeastern coast of New South Wales and has the capacity for rapid colour change. U. lineatus can rapidly modify its colouration and body pattern from plain buff/white to a prominent dark red and white vertically banded pattern in less than ten seconds ( Tosetto, Hart & Williamson, 2023 ). There are anecdotal reports of U. lineatus adopting a red colour when resting at night (personal observation) but during the day they are significantly more likely to shift colour and adopt a dark red pattern when actively feeding ( Tosetto, Hart & Williamson, 2023 ), seemingly making them more conspicuous ( Fig.…”

“…This body position potentially restricts both their field of view and mobility, which may reduce their capacity to detect and escape from predators. When U. lineatus feed and adopt the red banded colouration, they regularly have conspecifics and associated fish following them, and a previous study found that heterospecifics will spend significantly longer interacting with U. lineatus that are displaying the dark red banding while foraging ( Tosetto, Hart & Williamson, 2023 ).…”