Filial cannibalism improves survival and development of beaugregory damselfish embryos

Abstract

Cannibalism of small numbers of offspring by a parent has been proposed as an adaptive parental strategy, by providing energy to support parental care. However, there are few empirical studies to support this hypothesis. We conducted field and laboratory experiments to investigate partial filial cannibalism in Stegastes leucostictus, a coral reef fish with paternal care. Partial cannibalism was shown to be common, and males were found to remove developing embryos from throughout a clutch in a random pattern, rather than in the more aggregated pattern seen during embryo predation. Males that received a diet supplement grew faster than control males, but did not engage in less cannibalism. Also, males did not concentrate cannibalism on early embryonic stages with the highest energetic value. Experimental reduction of embryo densities was found to significantly increase embryo development rate and survival from egg deposition to hatching, and experimental reduction of oxygen levels significantly increased rates of partial filial cannibalism by males. Artificial spawning sites with low oxygen levels were avoided by spawning females, and cannibalism rates by males were higher. We propose that partial filial cannibalism serves as an adaptive parental strategy to low oxygen levels in S. leucostictus by increasing the hatching success of embryos.

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

“…One study suggested that energy from partial clutch cannibalism could potentially offset costs related to care (Apogon lineatus; Kume et al 2000), while another claimed that energy from eggs would be insufficient (G. aculeatus;Smith 1992). Also inconsistent with the energy-based hypothesis, Payne et al (2002) found that filial cannibalism increases in the later stages of egg development, when egg energetic value is much lower. Thus, there is a lack of general support for the energy-based explanation of filial cannibalism (Rohwer 1978;Sargent 1992), and at best current theory can only explain cannibalism in some cases.…”

Hurry-up and hatch: selective filial cannibalism of slower developing eggs

“…Indeed, previous work suggests that a range of factors are likely to affect and favour the evolution of filial cannibalism (Manica 2002;Payne et al 2002;Neff 2003;Klug & Bonsall 2007). For example, both parental condition and density-dependent egg survival affect filial cannibalism in the sand goby (Klug et al 2006).…”

“…Because energy is such an obvious benefit of filial cannibalism, much of the work aimed at understanding the adaptive significance of filial cannibalism has focused on energetic benefits (reviewed in Manica 2002). However, some have suggested that energetic benefits alone are unlikely to explain the prevalence of filial cannibalism in natural systems (Smith 1992;Payne et al 2002;Klug et al 2006).…”

The evolutionary puzzle of egg size, oxygenation and parental care in aquatic environments

“…Concurrently, parental care is more common in the former than in the latter group [27] and a variety of parental care strategies directly improve the access of O 2 to the embryos. For example, parents may choose nest sites according to O 2 availability [28,29], fan their eggs to improve suboptimal O 2 conditions [30,31], increase nest opening size [32,33] or cannibalize some of the eggs to improve the oxygenation of the remaining embryos [34,35]. In fact, parental care in aquatic species may have evolved, at least partially, to protect developing embryos from low O 2 availability, which in turn could have favoured the evolution of larger egg sizes [6,36].…”