The sarcastic fringehead is a small but fascinating fish that lives off the coast of California and Baja California in the northeast Pacific Ocean. This species is known for the incredible display behaviors in which combating males engage when defending adjacent territories. The sarcastic fringehead is a tube blenny, so called because they live in burrows or tube-like structures created by other animals. In the case of this species, the shelters are those created by burrowing clams or by empty snail shells. Some individuals have even been observed living inside soda bottles or other manmade materials.
Female sarcastic fringeheads, like all tube blennies, lay their eggs in a males’ shelter, and the males protect them from potential predators and other threats until they hatch. This sexual selection by females drives a system of intense male competition and territoriality. Male sarcastic fringeheads display to each other by opening their very large mouths in the direction of their rivals. The mouth’s intimidating coloration, combined with the extreme nature of it size (which may be as much as four times its closed size) allow the larger male to establish dominance over the smaller. Oftentimes, the rivals’ mouths are thrust very near to each other, sometimes touching. The smaller individual typically surrenders and leaves the area, without the pair actually fighting.
Little is known about the feeding habits of the sarcastic fringehead, but scientists expect that the grossly oversized mouths of the males may negatively affect their ability to feed. Most tube blennies feed on very small planktonic prey, but this species is unable to suction feed. They likely eat a variety of prey. During squid spawning season, sarcastic fringeheads can be observed eating large numbers of squid eggs, a valuable food source for many species.
The sarcastic fringehead is not targeted by fisheries and is not accidentally captured in fisheries targeting other species. Scientists believe this species to be one of least concern – it is not currently at risk of extinction.