Abstract
Many prey fishes possess large club cells in their epidermis. The role of these cells has garnered considerable attention from evolutionary ecologists. These cells likely form part of the innate immune system of fishes, however, they also have an alarm function, releasing chemical cues that serve to warn nearby conspecifics of danger. Experiments aimed at understanding the selection pressures leading to the evolution of these cells have been hampered by a surprisingly large intraspecific variation in epidermal club cell (ECC) investment. The goal of our current work was to explore the magnitude and nature of this variation in ECC investment. In a field survey, we documented large differences in ECC investment both within and between several populations of minnows. We then tested whether we could experimentally reduce variation in mean ECC number by raising fish under standard laboratory conditions for 4 weeks. Fish from different populations responded very differently to being held under standard laboratory conditions; some populations showed an increase in ECC investment while others remained unchanged. More importantly, we found some evidence that we could reduce within population variation in ECC investment through time, but could not reduce among-population variation in mean ECC investment. Given the large variation we observed in wild fish and our limited ability to converge mean cell number by holding the fish under standard conditions, we caution that future studies may be hard pressed to find subtle effects of various experimental manipulations; this will make elucidating the selection pressures leading to the evolution of the cells challenging.
Highlights
Many species of prey fishes, those members of the superorder Ostariophysi, possess large epidermal club cells in their skin [1,2]
In our laboratory test we found that all three groups [M-1, Marshy Creek-3 (M-3) and Pike Lake (PL)] of minnows differed in number of epidermal club cell (ECC) per mm of epidermis at the beginning of the experiment (ANCOVA, F2,117 = 65.9, P,0.001, all post hoc tests P,0.001, figure 3A)
Minnows captured from four different populations showed a threefold difference in mean number of ECCs per mm of skin between Oscar Creek and Pike Lake
Summary
Many species of prey fishes, those members of the superorder Ostariophysi, possess large epidermal club cells (hereafter ECCs) in their skin [1,2]. Smith [6] established that, during the breeding season, male minnows lose their ECCs and skin extracts made from breeding minnows do not evoke anti-predator behaviour in conspecifics This finding lead to the conclusion that ECCs are the source of the alarm cues and has been supported by numerous studies [7,8,9,10]. A recent study by Carreau-Green et al [11] suggested that the skin of juveniles of one species of fish may evoke an alarm response in conspecifics even before the cells appear If this finding is supported by additional experiments, it would provide strong evidence against the role of the cells as the source of alarm cues.
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
