Do not eat your kids: embryonic kin recognition in an amphibious fish
Adult animals of many species often behave in a cannibalistic manner when encountering conspecific offspring. Kin discrimination is critical for avoiding the consumption of one’s own offspring or filial cannibalism. Some fishes cannibalize embryos when other nutritional sources are unavailable. We tested the hypotheses that (1) adult mangrove rivulus, Kryptolebias marmoratus, cannibalize conspecific offspring; (2) cannibalism of unrelated conspecifics is more prevalent than filial cannibalism and (3) the drive to cannibalize embryos is associated with nutritional status (‘energy-based hypothesis’). We examined cannibalistic behaviours of the self-fertilizing amphibious K. marmoratus in the laboratory using two isogenic strains. Adults recognized kinship of single embryos, cannibalizing unrelated embryos (28% of the time) but not their own. The ability to recognize kin differed between isogenic strains. Thus, genetic differences significantly influenced behaviour. Fasting had no significant effect on cannibalistic behaviours and thus nutritional state is not an important factor driving cannibalism in this species under these conditions. This is the first documented evidence that a fish species can recognize the kinship of an individual embryo.
Across the animal world, there are many examples of animals that eat their own offspring (filial cannibalism), but the outcome of such behaviour may be reproductively costly. Other animals may consume offspring belonging to other parents (non-kin cannibalism). The trick is to recognize the difference between your own versus someone else’s offspring to optimize reproductive success. Previous studies on fish have shown that parents can assess the relative ratio of kin to non-kin embryos in an entire nest, but the ability to recognize single embryos has not been demonstrated. We have shown that when a self-fertilizing mangrove fish was presented with a single embryo, it never ate its own but consumed unrelated embryos, suggesting that they have the ability to recognize solo relatives at very early stages of development.
KeywordsFilial cannibalism Energy-based hypothesis Mangrove rivulus Kryptolebias marmoratus
The authors wish to thank anonymous reviewers for excellent suggestions. Thanks also to Drs. F. Laberge and A. Heyland for the advice on experimental design; D. Eisner for the help with data collection; Drs. A. Gibb, B. Robinson, D.S. Taylor and R. Earley for the discussions and a special thanks to Drs. A. McAdam and B. Allen for sound statistical advice. A. Turko provided very useful advice on several aspects of this project. Thanks to K. Levesque and H. Ferguson for providing the typographical help. Thank you to B. Frank, M. Cornish, M. Davies and several volunteers for their help with fish maintenance. Funding was by NSERC Discovery grants program to PAW and an OGS grant to MWW.
MWW and PAW conceived and designed the project. MWW executed the experiments and analysed the data. MWW wrote the draft manuscript. PAW and MWW revised the manuscript.
Compliance with ethical standards
Our experiments were conducted in Canada and comply with the current laws of the country in which they were performed. All experiments were carried out under the Animal Utilization Protocol 10R068 at the University of Guelph.
Conflict of interest
The authors declare that they have no conflict of interest.
The datasets analysed during the current study are available from the corresponding author on reasonable request.
- Courtenay SC, Quinn TP, Dupuis HMC, Groot C, Larkin PA (2001) Discrimination of family-specific odours by juvenile coho salmon: roles of learning and odour concentration. J Fish Biol 58:107–125Google Scholar
- Elwood RW (1994) Temporal-based kinship recognition: a switch in time saves mine. Behav Process 33:15–24Google Scholar
- Huber JH (1992) Review of Rivulus: ecobiogeography, relationships. Société Française D'ichtyologie, ParisGoogle Scholar
- Kristensen I (1970) Competition in three cyprinodont fish species in the Netherlands Antilles. Stud Fauna Curaçao Caribbean Isl 32:82–101Google Scholar
- Li SK, Owings DH (1978) Sexual selection in the three-spined stickleback: II. Nest raiding during the courtship phase Behaviour 64:298–304Google Scholar
- Taylor DS (1988) Observations of the ecology of the killifish Rivulus marmoratus (Cyprinodontidae) in an infrequently flooded mangrove swamp. NE Gulf Sci 10:63–68Google Scholar
- Turko AJ, Earley RL, Wright PA (2011) Behaviour drives morphology: voluntary emersion patterns shape gill structure in genetically identical mangrove rivulus. Anim Behav 82:39–47Google Scholar
- Zar JH (1999) Biostatistical analysis. Prentice Hall, Upper Saddle River, NJGoogle Scholar