Sea hares are sea slugs that get their name from looking somewhat like a crouching rabbit in profile. Their head sports two pairs of tentacles, the fleshy oral tentacles that surround the mouth, and the vertical enrolled head tentacles, or rhinophores. Both of these sets of tentacles can be seen in today’s photo.
Today’s subject is a California sea hare (Aplysia californica), which is also called the brown sea hare, to distinguish it from its larger cousin, the black sea hare (Aplysia vaccaria). These animals cruise the ocean floor in search of algae snacks, and like many snails and slugs, are strict vegetarians.
There is another part of sea hare anatomy that can also be seen in this photo – a small bluish eyespot located just below and very slightly in front of the base of the rhinophore. While I have observed and photographed sea hares for over 40 years, I have never until examining this photo noticed an eyespot. I have found that some species of sea hares do possess eyespots, though I haven’t confirmed that for this particular species. If it is an eyespot, it most likely only detects brightness, and doesn’t form an image like our eyes. It would be useful for helping the sea hare to avoid crawling into dark crevices where very little algae is likely to be found.
And this particular sea hare, with its oral tentacles extended straight ahead seems to be especially interested in getting to its next meal.
This photo was taken with a Canon EF100 mm f/2.8 Macro USM lens on a Canon EOS 5D Mk III in an Ikelite underwater housing. Lighting was provided by an Ikelite DS161 strobe set to eTTL exposure mode. The exposure was set to 1/45 sec at f/9.5 and ISO 400.