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What in the World is This? The mottled sea hare

Today, I’m launching a new blog series: What in the World is This? Through this series, I’ll help people identify some of the strange and wonderful creatures they encounter in our marine environments, from our magnificent bays to Gulf of Mexico beyond.

As an Extension marine and coastal agent, a lot of people send me pictures of marine creatures and plants that they encounter so I can help identify them. I love that part of my job, since I enjoy sharing cool facts about amazing organisms. And, I even enjoy the challenges these requests sometimes represent. As a marine biologist and resident of the Gulf of Mexico for 15 years, I feel quite confident in my knowledge of many species; however, I do not know them all, and I am OK with that. In fact, scientists have calculated that about 91 percent of the species that live in the ocean still await description(*).

So, requests to identify organisms help me learn more and allow me to share with others incredible facts about our marine world. And that leads me to the “What in the World is This” series, through which I’ll write a short blog post about each animal or plant that people ask me to identify, and maybe even increase the requests to identify more creatures.

The first organism we’ll look at? The mottled sea hare (Aplysia fasciata), also known as the sooty sea hare.

A mottled sea hare is shown in Sarasota Bay. [CREDIT: Judith Kendall]

A mottled sea hare is shown in Sarasota Bay. [CREDIT: Judith Kendall]

During a paddleboarding trip in the intracoastal waterway in South Venice, a local resident came across this very cool marine gastropod, noting: “I have never seen this animal before, … please let me know if you know what species it is? It looks like a squid/turtle?” And, she sent me the picture featured in this post.

This time, I knew what it was.

The mottled sea hare belongs to the class Gastropoda, the largest group of organisms in the phylum Mollusca. There are more than 65,000 species that belong to this class. This class includes snails such as conch, which have a shell, and slugs like nudibranchs and sea hares that have no external shell.

Sea hares are herbivores, which means that they eat plants. Sea hares typically crawl along the bottom of the sea to feed on algae, though some swim quite well. The mottled sea hare swims so gracefully that it seems like it is flying, and they are known for swimming along the surface of the water.

Sea hares have chemosensory organs on the upper surface of their heads, and use them for smell and taste. Known as rhinophores, the organs look like bunny ears, which is where the sea hare gets its name.

Another cool fact about sea hares is that they are all hermaphrodites, with both male and female reproductive organs, but they still need a mate to reproduce. One benefit for a hermaphrodite is the boost to reproductive success for species with lower population densities or/and those species with limited mobility.

There are many more species of marine gastropods in Florida, but the mottled sea hare is one of the coolest.

If you have more questions about sea hares, please do not hesitate to contact me, and if you have a picture of an organism that you would like to learn more about, please follow the link to fill out my “What in the World is This?” form.

Let’s keep learning about our wonderful marine biodiversity, and discovering more cool facts about the inhabitants of the oceans.

* Mora C, Tittensor DP, Adl S, Simpson AGB, Worm B (2011) How Many Species Are There on Earth and in the Ocean? PLoS Biol 9(8): e1001127.

15 Comments on “What in the World is This? The mottled sea hare

  1. Is this one? Oh…I can’t seem to add picture. Don’t have a video picture of it swimming in water, but it did “flap” and was graceful. It did ink purple fluid. Charter guys that took us fishing in St. Petersburg said they didn’t know what it was, but call them “Sea Underwear” because they look like a pair of underwear when flapped open.

  2. Thank you for your posting. We saw two yesterday in Sarasota Bay and spent hours on Google trying to figure out what they were. Fortunately we found your blog.

    • Hi Richard,

      I am glad that you saw two and that the blog helped you. In the future, please feel free to fill out the form (see link in the blog), and I might be able to help identify an organism or two. Email will work too. Cheers, Armando

  3. Hello Armando! I saw a cluster of about 100 sooty sea hares off of a sea wall near Fort DeSoto in Pinellas County last month. They were just swimming and swirling around, but didn’t seem to be making physical contact with one another. Any idea what they were doing or why so many were clustered together?

    • Hi Sarah,

      I am not sure, probably mating, perhaps you did not catch them on the right time :). Do you have any pictures of that event?

  4. Armando, this is my favorite sea creature, not around like they used to be….see them sailing..playing in deep tidal pools…with children squealing for joy….wonderful article
    Karen Pariser
    Master Gardener

    • Thank you Karen. I also love how they move and swim.

  5. Thank you for sharing some new and amazing! Have a beautiful day! Be safe!

  6. Please correct the error… INTRACOASTAL Waterway ..not INTERCOASTAL

  7. I found a huge one once near Anna Maria City Pier (then Fast Eddy’s). It was at least 15″ across. Lovely animals. Also on Anna Maria I’ve seen hundreds at a time of the small purple ones near the shore. I like the series!!

    • Thank you Shelly, and indeed, they are lovely animals. Do you have a picture of the small purple one?

  8. Amazing creature . . . Interestingly I’ve never come across one myself in all my times on FL waters . . . never too old to be amazed though . . . Found a great video of one swimming at

    • Thank you Dr. K. The mottled sea hare is indeed an amazing creature. I am getting a lot of reports of sightings right now in Sarasota Bay and the Gulf. I hope you get to see one soon.

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