Parents Benefit From Eating Offspring: Density-Dependent Egg Survivorship Compensates for Filial Cannibalism

Abstract

Abstract. Why should animals knowingly consume their own young? It is difficult to imagine many circumstances in which eating one's own young (i.e., filial cannibalism) actually increases an individual's fitness; however, filial cannibalism commonly co-occurs with parental care in fishes. The evolutionary significance of filial cannibalism remains unclear. The most commonly accepted explanation is that filial cannibalism is a mechanism by which caring males gain energy or nutrients that they reinvest into future reproduction, thereby increasing net reproductive success. There is mixed support for this hypothesis and, at best, it can only explain filial cannibalism in some species. A recent alternative hypothesis suggests that filial cannibalism improves the survivorship of remaining eggs by increasing oxygen availability, and thus increases current reproductive success. This theory has received little attention as of yet. We evaluated the hypothesis of oxygen-mediated filial cannibalism in the sand goby by examining the effect of oxygen and egg density on the occurrence of filial cannibalism, evaluating the effects of partial clutch cannibalism on the survivorship of remaining eggs, and comparing potential costs and benefits of filial cannibalism related to the net number of eggs surviving. Indeed, we found that oxygen level and egg density affected the occurrence of cannibalism and that simulated partial clutch cannibalism improved survivorship of the remaining eggs. Additionally, because increased egg survivorship, stemming from partial egg removal, compensated for the cost of cannibalism (i.e., number of eggs removed) at a range of cannibalism levels, filial cannibalism potentially results in no net losses in reproductive success. However, oxygen did not affect egg survivorship. Thus, we suggest a more general hypothesis of filial cannibalism mediated by density-dependent egg survivorship.

Maternal Size and Age Shape Offspring Size in a Live-Bearing Fish, Xiphophorus birchmanni

“…As larger females are more fecund, density-dependent competition or survival is expected to be most important for offspring of larger females [29]. Although density-dependent egg mortality has been shown to occur in nests of sand gobies [43], little is known about possibility of density-dependent survival or competition for space among siblings in livebearers, as density-dependent processes are very difficult to study prior to birth. Again, more research is needed to determine the contribution of within-brood density-dependence to observed variation in swordtail offspring sizes.…”

Paternal care behaviors of Japanese giant salamander Andrias japonicus in natural populations

“…Klug et al (2006) found that simulated partial-clutch cannibalism increased survivorship of the remaining sand goby eggs, presumably because of densitydependent egg survival. Furthermore, a mathematical model suggests that the evolution of filial cannibalism can be facilitated by selective consumption of lower-quality eggs (Klug and Bonsall 2007).…”

You eat what you are: personality‐dependent filial cannibalism in a fish with paternal care

“…; Manica ), but this pattern is clearly not universal (e.g., Lindström and Sargent ; Klug and St Mary ; Klug et al. ). Other ideas such as selective cannibalism of inferior eggs (Klug and Lindström ) or a reduction of egg density to enhance oxygen availability to the remaining eggs (Payne et al.…”