HAMMERHEAD SHARKS
The scalloped hammerhead shark is an awesome predator. In lectures, I have likened the hammerhead to an advanced spy plane. First, the eyes set out at the end of the wide "snout" (called a cephalofoil), gives it an ultra wide field of view, especially in the vertical plane. Second, they gain a significant increase in smell reception, although not as much as they are sometimes credited for, as in the accounts that boast of their ability to "detect a drop of blood across the ocean". They do have a tremendous electrical sensitivity, due to the increase in numbers and distribution of sensory pores across the "snout", called Ampullae of Lorenzini. In addition to detecting bioelectrical signals from their prey, the hammerheads also can detect changes in the electromagnetic fields, using this sensitivity to assist in navigation.
Often, in the waters off the northern Galapagos islands of Darwin and Wolf, one encounters swarms of hammerheads; some say this behavior is related to courtship; in any case, it's an incredible experience to behold.
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Hammerheads are amazing creatures - we're just beginning to really learn about them. They are also critical to the environmental balance of the ocean, culling out the weak. Unfortunately, they currently endangered, due to
illegal fishing of sharks for their fins.
illegal fishing of sharks for their fins.
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MANTA RAYS
With a wingspan of up to 20 ft or more, the manta ray is an awesome creature to share the water with. So powerful, yet so graceful.
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The cephalic horns in front are used to herd the baitfish and krill-like invertebrates into its open mouth. Here we see both a dorsal (L) and ventral (R) view, with the gill slits on the ventral side.
This manta has a stowaway - a remora fish (2 of them actually), clinging on with it's dorsal fin acting as a suction device. See close-up below (l). If we want to be anthropomorphic, we could say that if you look at them from front-on, they appear to be smiling (below R).
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Manta rays are threatened the world over, mostly due to overfishing (some scallops aren't really scallops!) and bycatch in nets. While they actually approach divers at times, they will flee when a diver suddenly swims up and touches it. Not good.
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WHALE SHARKS
Looks like a whale. It's as big as a whale (40 ft+ adults weighing about 30 tons). Feeds like a baleen whale (filter feeding/ sifting plankton). But it's a shark, the largest of the sharks and therefore the largest fish. And harmless to divers, unless you do something foolish, and the tail fin takes a swipe.
Even the mouth is 5 ft wide.
Even the mouth is 5 ft wide.
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Always use your dive buddy for scale to show the true size of a creature!
