Early filial cannibalism revisited from an endocrinological perspective

Offspring desertion by parents generally occurs at an early stage of parental care, which is considered to minimize the time and energy costs of parental care prior to desertion and ensure an opportunity and time for future reproduction. In addition to these conventional reasons, we investigated the effects of endocrinological constraint on early total filial cannibalism in fish in which care-giving males eat all eggs and restart reproduction when tending a small number of eggs. The occurrence of total filial cannibalism in male Rhabdoblennius nitidus, a paternal brooding blennid fish with androgen-dependent brood cycling, was strongly associated with decreased plasma 11-ketotestosterone levels, suggesting that males in which it was difficult to exhibit courtship behavior began to cannibalize eggs. Moreover, the additional mating probability at the beginning of parental care may delay the timing of total filial cannibalism; at the same time, the costs of parental care may shift the timing earlier than expected based on androgen decline. These results suggest the potential importance of considering endocrinological constraints with respect to the adaptivity of behavioral traits.

亲本弃养子代通常发生于育幼行为的早期阶段，此举被认为可降低弃养前育幼所耗费的时间与精力成本，并为后续繁殖预留机会与时间。除上述常规动因外，本研究针对护卵雄鱼在照料少量鱼卵时会吞食全部鱼卵并重启繁殖的鱼类类群，探究了内分泌约束（endocrinological constraint）对早期全部食卵行为（total filial cannibalism）的影响。对于依赖雄激素（androgen）调控护卵周期的雄亲代护卵鳚科鱼类——细纹鳚（Rhabdoblennius nitidus）而言，其全部食卵行为的发生与血浆11-酮睾酮（11-ketotestosterone）水平下降显著相关，这表明难以展现求偶行为的雄鱼会转而吞食鱼卵。此外，育幼初期额外的交配概率可能会延迟全部食卵行为的发生时间；与此同时，育幼成本可能会使该行为的发生时间早于基于雄激素水平下降所预测的时间节点。上述研究结果表明，在探究行为性状的适应性时，考虑内分泌约束因素具有潜在的重要意义。