Retorts such as ‘My Dad's (insert adjective here) than your Dad!’ have haunted schoolyards for generations, but recent work published in the Proceedings of the Royal Society B suggests that there might be some biological relevance to these chants. Adequate parental care is, of course, essential to offspring well being and denying this care can permanently alter how offspring respond to stressful situations. Maternal care is well known to affect the behavioral phenotype of offspring, but we know very little about the influence of paternal care. Moreover, the adaptive significance of such non-genetic parental effects on offspring behavior is so far only speculative. Katie McGhee from the University of Illinois, USA and Alison Bell from the University of Cambridge, UK wanted to know how paternal care contributes to the behavioral phenotype of offspring, and whether or not this translates to a fitness benefit.

In an attempt to answer these questions, McGhee and Bell designed a set of experiments using three-spined sticklebacks. Stickleback dads are the sole caregivers for the clutch of eggs that they fertilize, providing essential life-supporting care to their wee ones by guarding the nest against hungry predators and fanning their eggs to help circulate oxygen. In the first set of experiments, the researchers removed half of a father's clutch of eggs and raised them separately as orphans, then monitored the father's behavior with the remaining eggs in order to assess the quality of care offered by a particular father. For example, while some fathers spent most of their time at the nest and frequently fanned their young (direct care), others spent more time inspecting a fake predator placed in their tank at the expense of nest guarding and fanning (defensive care). Then, when the offspring were a little older and no longer under Dad's watchful eye, McGhee and Bell tested the father-raised offspring and their orphaned siblings for anxiety-like behavior. As one might expect, orphaned fish tended to be more anxious than those that had received paternal care, but the quality of that paternal care had an even bigger effect on behavior. Orphans that missed out on the affections of a father giving direct care were considerably more anxious than their father-reared siblings, but this disparity was less pronounced when orphaned and reared siblings from defensive care fathers were compared. So, paternal care does affect offspring behavioral phenotype, but are these changes biologically relevant?

In a second experiment, McGhee and Bell used a new group of juvenile sticklebacks that were raised as orphans, without any paternal care. First, they assessed each juvenile for anxiety-like behavior as in the previous experiment, and then 2 h later they placed it in a tank with a big and scary live Northern pike fish. The fish were permitted to freely interact…for a little while at least. The researchers measured how long it took for the pike to launch its first attack on the stickleback and how long it took for the little fish to become the pike's dinner. Their results were clear: the higher an orphaned stickleback scored on its anxiety test, the sooner it became pike food, underscoring that non-genetic paternal effects on stickleback behavior are directly linked to fitness. So, in sticklebacks, there is no substitute for a father's love.

K. E.
A. M.
Paternal care in a fish: epigenetics and fitness enhancing effects on offspring anxiety
Proc. R. Soc. B