Loss of hard chorion: An evolutionary dead-end for parental egg-care fish

Parental egg-care in fish traps them in an evolutionary dead-end through the loss of the chorion-hardening system, according to scientists from the Institute of Science Tokyo. Fish have diverse egg-caring strategies that have independently emerged multiple times across lineages. Comparative whole genome analyses of 240 fish species revealed a strong correlation between loss of the chorion-hardening system and parental egg-care, revealing the mechanisms behind the evolutionary bias that restricts egg-caring fish from becoming non-egg-carers.