The potential for egg-guarding care in females of the damselfish, Dascyllus reticulatus, in the absence of uniparental male care.

Male damselfish typically demonstrate uniparental egg-guarding care in nature. Potential plasticity in sexual behavior has recently been reported in various teleost fish. To examine behavioral plasticity in parental care, we conducted aquarium experiments to explore the potential for egg-guarding care in the female damselfish, Dascyllus reticulatus. After initial caretaking, males were removed from the mating nests, and cohabiting females frequently exhibited egg predation on the same day. However, we confirmed that females showed significantly decreased egg-predation frequencies on the following day and showed egg-caring behaviors. All experimental females guarded their eggs until they hatched. Females subsequently spawned eggs as females even after performing parental care behaviors, indicating no progression of sex change into males. Molecular analysis of select pituitary gland hormones indicated that egg-caring females and males showed high expression levels of prolactin, suggesting its involvement in the development of parental care behaviors. The cryptic possession of caretaking ability in females may be a tactical response to the need for temporary replacement of the care roles in cases where caretaking males are removed, for example, through predation, in damselfish species living in sexually cohabiting groups.

Stable maintenance of hidden switches as a strategy to increase the gene expression stability.

In response to severe genetic and environmental perturbations, wild-type organisms can express hidden alternative phenotypes adaptive to such adverse conditions. While our theoretical understanding of the population-level fitness advantage and evolution of phenotypic switching under variable environments has grown, the mechanism by which these organisms maintain phenotypic switching capabilities under static environments remains to be elucidated. Here, using computational simulations, we analyzed the evolution of gene circuits under natural selection and found that different strategies evolved to increase the gene expression stability near the optimum level. In a population comprising bistable individuals, a strategy of maintaining bistability and raising the potential barrier separating the bistable regimes was consistently taken. Our results serve as evidence that hidden bistable switches can be stably maintained during environmental stasis-an essential property enabling the timely release of adaptive alternatives with small genetic changes in the event of substantial perturbations.