Within the family Anablepidae, there is a genus Anableps which are known as four-eyed fish. They are found in Central and South America in fresh or brackish waters. These fish are live bearers and interestingly they exhibit a “sidedness”. Males that are left-handed may only mate with females that are right-handed.
Now the fish do not have four eyes exactly, but in both eyes they can see above and below water simultaneously. This is a good super power to have when you spend most of your time on the surface foraging insects.
Photo Credit: Paul Zahl/National Geographic
The retina is specialized so that half receives light from the aquatic environment and the other from the aerial environment. Recent research found that the dorsal and ventral retina have differential gene expression. Click here for a link to the article to learn more.
The salamanderfish (Lepidogalaxias salamandroides) is in the family Lepidogalaxiidae all by itself. These unique fish are found in the acidic waters of western Australia. Remarkably, like the lungfish these tiny creatures can survive drought by burrowing in the sand and aestivating.
Watch the video below to see a salamanderfish and hear more about them.
Building on the post from Wednesday, a paper recently came out from Behavioral Ecology (A. Bahr et al., 2012 click here for a link to the paper) investigating the potbellied seahorse mating system. Although the seahorse mating system is based on female competition and male mate choice, this work suggests that both sexes actually exert a preference for mate choice. The authors investigated olfactory cues in the form of major histocompatibility class II beta chains (MHIIb) and also visual cues of body size. Results suggest that males prefer and mate with larger females, but disregard MHIIb cues. Conversely, females show a preference for males that are dissimilar in regards to MHIIb, but have no preference for body size. In conclusion, the authors posit this system is actually mutual mate choice and not simply male mate choice.
If you missed the video of the potbellied seahorse courtship you can find it below.
Sexual dimorphism comes in many forms and the three-spined stickleback represents one of the most interesting examples. A recent PLoS ONE paper (link here) reports that male three-spined sticklebacks have 23% heavier brains when compared to females! While there is no difference in body size there are massive behavioral differences that may account for the neural size disparity. Male sticklebacks court the females, create fancy nests and are the sole care providers for the kids.
Left: female Right: male
There is also an older paper showing a correlation in male bower bird brain size and the complexity of the nest. Check it out here- Sex, bowers and brains: J. Madden