Daddy Darters: Responsible Father or Deceitful Womanizer?

Cornell University

The Tesselated Darter, Etheostoma olmestedi, from Cornell University

Of the 850+ species of freshwater fish in the United States and Canada, over half exist in Southern Appalachia and many of them are unique to this region alone.  One charismatic and colorful group of fish radiated from the Perch, Percidae, into some of the most peculiar characters in creek, the Darters.

 

If I told you that these fish can be compared with the likes of the Seahorse and the Emperor Penguin, what would you think of?  You probably guessed that the males play a major role in caring for the young and ensuring their survival.  You’re right! But even more than that, daddy Darters take care of eggs that AREN”T EVEN THEIRS!  Remarkable right?  Considering that the basic principles of natural selection claim that individuals care only about the survival of their own genetic line.  Well, before we give the daddy Darter too much credit lets take a closer look.

 

When a dominate Tesselated Darter, Etheostoma omstedi, finds a lady that he’s into, he leads her to his flat bottomed rock, turns upside down, and shows off his parenting skills by writhing back-and-forth on the rock.  This is his way of showing his lady-friend that he is the best egg and rock cleaner around.  She then inspects the rock for it’s cleanliness and, if she approves, deposits her eggs on the underside of the rock.  The daddy will then fertilize them, chase away mom (never to be seen again), and start his important job of cleaning and aerating the eggs until they hatch.  When that daddy darter leaves, another darter will actually come and help him clean and aerate the eggs.

 

So, these are remarkable role models father right?  Wait a second, Darwin says that something isn’t adding up.  Are darters so altruistic that they babysit each other’s eggs?  Sadly, not quite.

 

After a few days of dedicated parental care, the daddy decides that he has wanderlust, and just lust, and must answer the call.  He is, after all, the dominant male in the pool which is why he succeeded in mating in the first place.  Sorry ladies but it did sound too good to be true.

 

The eggs have solidified to the rock surface enough to ensure some of their survival after his departure so he’s off to start another family and care for another batch of eggs.  This is where the next “daddy” steps in to help.  A non-dominate Darter, known as a floater, takes over the care of the eggs and proceeds to clean and aerate them.  If a female comes to the rock and sees this dedicated male working tirelessly to care for his young, she concludes that he must be a responsible father and will mate with him under the same rock.  So, by caring for another more dominate daddy’s eggs, the floater shows off his parenting skills and will sometimes get laid.

 

So, it turns out that the “responsible” daddy Darter isn’t truly altruistic but is really doing it just to have more sex.  Ugh….men.  However don’t lose faith.  There is another (more responsible) fish character in the Appalachian stream that will keep your faith in fish manhood.  The male Mottled Scuplin, Cottus bairdii, IS the responsible parent that the Darter isn’t.  His eggs don’t harden after a few days so if he leaves his brood they are much more vulnerable to predation so he has to stick with his eggs until they hatch.  Attaboy Sculpin.

Mottled Sculpin

Mottled Sculpin, Cottus bairdii, photo by Joseph Tomelleri

 

Constanz, G.D. 1979. Social dynamics and parental care in the tesselated darter. Proc. Acad. Nat. Sci. Phila. 131:131-38

Constanz, G.D. 1985.  Allopaternal care in the tesselated darter. Env. Biol. Fish. 14:175-83.

Downhower, J.F. and L. Brown. 1980. Mate preferences of female mottled sculpins, Cottus bairdi. Anim. Behav. 28:728-34

 

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