Hybrid sharks in the south Pacific
By Maggie Koerth-Baker at 1:09 pm Tuesday, Jan 3
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The Australian blacktip shark lives in tropical waters. The common blacktip shark prefers its water subtropical and temperate. Because of the difference in habitat, these two animals have become separate subspecies with distinct physical differences.
However, there are some places where their habitats overlap. And here, along the eastern coast of Australia, there is interspecies nookie. And hybrid baby sharks.
Now, none of that is particularly shocking. Hybrid zones, where the habitats of two genetically compatible species overlap, aren't ridiculously common, but scientists have documented quite a few. What makes this finding interesting is that the two species and their hybrid have been genetically documented. Hybrid zones can be fuzzy places. What happens there calls into question how sure we can be that that what we call species really are all that different from one another.
What makes this study interesting is that researchers actually performed genetic testing on sharks caught in the hybrid zone. They found distinct genetic differences between the blacktip and Australian blacktip sharks, especially in their mitochondrial DNA. And the hybrids were identified based on genetics as well. That's something that's a lot more rare in the study of wild hybrids. The information gathered here could end up having a lot to teach us about how evolution happens and what speciation really means.
Via Mo Costandi
A new study conducted in Florida has given scientists reason to believe that hammerhead sharks may have vision comparable to that of humans. The researchers measured electrical activity in the eyes of half a dozen sharks from three different hammerhead species. They then put electrodes under the sharks' corneas and recorded electrical activity while shining lights in horizontal and vertical arcs around each eye. Compared to normal-headed sharks, the hammerheads had three times the visual overlap — that's what creates stereo vision and depth perception in animals with eyes that face forward. This, of course, helps them be faster and more efficient at hunting prey. But there's a catch: because their eyes are so far apart, hammerheads have these giant blind spots right in the middle of their head. As study leader Michelle McComb put it in an interview with National Geographic: