A team of researchers has found that female three-spined stickleback fish prefer nests built by males that are best suited for current environmental conditions. Males may change their nest designs as water quality changes and these adaptable males may be more attractive to the females. The details are in a paper that was just published in the journal Evolution.
Three-spined sticklebacks (Gasterosteus aculeatus) are small fish that are popular models for scientific studies due to their complex behaviors and ease of care. Stickleback males, not females, take care of the eggs and young. Fathers build nests and then tend to the eggs, keeping them oxygenated and safe. Once the fry hatch, the fathers continue to care for the babies until they’re old enough to fend for themselves. Proper nest-building is critical since the eggs are sensitive. The research team wanted to investigate how nests were built in low oxygen conditions, not unlike the conditions caused by climate change.
Researchers from Australia exposed the fish to different levels of dissolved oxygen. Proper oxygen flow is necessary to keep eggs healthy. Male sticklebacks fan the eggs with their fins but nest design also plays a role. The team found that in low oxygen concentrations, the males would build looser nests, allowing more oxygen to enter. When levels of dissolved oxygen were high, the males switched to building compact nests. These compact nests were safer for the eggs but could smother them if oxygen dropped too low. This showed that the male fish were making decisions based on the environment. Even more interestingly, the females noticed these design choices and preferred nests that were built properly based on current water quality.
The team’s findings show flexibility and adaptability to changing conditions in three-spined sticklebacks. This may help them survive as water conditions change due to global warming and pollution.
Head ML, Fox RJ, Barber I. Environmental change mediates mate choice for an extended phenotype, but not for mate quality. Evolution (2016).