When many people think of animals that care for their offspring, they are likely to think more of mammals or birds than fish. Yet, even in this world not all species leave their offspring to fend for themselves, caring for them in the early moments of life.
And, when it comes to parental care, it is not only mothers who are the protagonists. The film “Finding Nemo” shows the clownfish Marlin, a single father, crossing oceans and facing numerous dangers to find his lost son, Nemo. Although it is only a film, a pair of scientists says it may reflect much more the true behavior of father fish than previously thought.
A study published in the journal ‘Philosophical Transactions B’ comes to show that “dads matter too” and that offspring that receive care from male parents end up becoming bolder and more sociable adults.
The work focused on a freshwater fish species known as the three-spined stickleback (Gasterosteus aculeatus), which occurs in North America, Asia and Europe, including Portugal, in the basins of the Minho, Ancora, Lima, Cávado, Vouga, Mondego, Lis, Tagus, Sado and Mira rivers. According to the “Red Book of Freshwater and Diadromous Fishes of Mainland Portugal,” 2023, it is “in danger” of extinction primarily due to the destruction and fragmentation of its habitats, such as dam construction, and also to pollution and excessive water withdrawal from the rivers where it lives.
In this species, only the males provide care to the offspring, as the females, after laying eggs in the parent’s nest, leave immediately.
Through laboratory experiments, the researchers Jason Keagy (Pennsylvania State University) and Alison Bell (University of Illinois at Urbana-Champaign) discovered that the boldness and sociability of the offspring that received care from male parents are behavioral traits associated with the expression of specific genes in their brains.
“The presence of the father during the first 10 days of life seems to influence the behavior of the fish later in their lives,” says Keagy, who notes that most of the research conducted in the field of parental care has used rats as model organisms, where maternal care stands out.
“Three-spined sticklebacks are one of the rare species in which the fathers exclusively care for the offspring,” he adds, saying that, therefore, they are a good example to try to understand what changes occur in the offspring when the parents are the main, or the sole, caregiver.
The experiments allowed the researchers to perceive that the offspring that received paternal care during the first ten days tended to explore more unfamiliar environments and stay active even in the face of threats more than those that did not have such paternal attention. In addition, they were also the offspring that interacted more with other group members.
In cerebral terms, the fish that received parental care during the first ten days of life showed differences in the genes that were active, compared with other fish that did not receive the same care. Since the presence of the father was the only thing that differed between groups of offspring, the researchers conclude that parental care also affects the development of the brains of the young fish.
“These results suggest that paternal care is associated with differences in brain gene regulation that affect brain development and function, which translates into differences in behavior in adulthood,” explains Keagy.
