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Home › Sea Life › Marine › Invertebrates › Mollusks › Sea Hare

Interesting Facts about Sea Hares

[Sea Hare Phylum: Mollusca] [Class: Gastropoda] [Subclass: Heterobranchia] [Order: Aplysiida]

Worldwide, there are thought to be around fifty (50) validated species of large marine gastropods falling under the genus Aplysia.

This section contains fun facts and information about sea hares, including where they live, what they eat, and how they reproduce.

Sea Hare Habitat and Distribution (Aplysia)

These gooey bottom-dwellers are one of the largest marine gastropod mollusks that resemble many of the sea slug family.

They inhabit many of the world's shallow sea beds in temperate and tropical oceans, in areas like:

• Intertidal rocky shorelines with healthy supplies of algae.
• Kelp forests and seagrass meadows.
• Shallow coastal waters, especially tidal pools and lagoons.
• Rocky reef structures that combine sand and muddy bottoms.

Sea hares are a benthic species that live in various depths of intertidal zones. As a consequence of that, most of these aquatic invertebrates spend the majority of their lives (about one year) crawling around the seafloor and rocky outcrops.

In general, sea hare populations are widespread and thriving in most regions of the world. As a result, they are a common sighting at many of the scuba diving sites in the United Kingdom, the Mediterranean Sea, and along the North and South America coastlines.

Pro Tip: Most of the sea hare and nudibranch phylum live in salt water environments. Even so, a few of the sea slug species can survive in brackish water.

Sea Hare Characteristics and Behaviour

Another section contains a list of "inappropriate fish names" - such as the dumb gulper shark. But, the common name "sea hare" comes from the upper rhinophores (a pair of head tentacles that resemble the ears of a hare or rabbit) used to detect chemical cues.

The body structure of sea hares (especially of the Order Aplysiida) is soft and elongated. The head tends to be the distinctive feature - along with their parapodia (wing-like flaps) that lack any notable protective shell.

Respiration takes place through gills located inside the mantle cavity. They also have a soft, somewhat transparent internal shell made of protein that measures about four (4) centimetres long.

Here's the thing:

The mottled reddish maroon and green camouflage of the sea hare species corresponds well with the colouration of the seaweed that they eat. For example, red coloured sea hares feed on red seaweed.

Some species of sea hares are able to use a kind of jet propulsion as a form of locomotion (e.g. for swimming and gliding).

Whereas, others use a muscular foot to move around the sea bed or "undulate" in a similar way that stingrays do.

Fun Fact: The California black sea hare (Aplysia vaccaria) is the largest of all sea hares. Adults can reach a total length of seventy five (75) centimetres (30 inches) and weigh around 14 kilograms (31 pounds). Still, the average length of most sea hares ranges between seven and twenty centimetres.

What Do Sea Hares Eat?

Sea hares are typical herbivores that use a rasping radula to feed on the different types of plant life that live in the ocean, such as:

• Algae (photosynthetic eukaryotes), including other macroalgae material such as:
  • Brown algae (Phaeophyta)
  • Green algae (Chlorophyta)
  • Red algae (Rhodophyta)
• Cyanobacteria
• Kelp (Laminariales)
• Seagrasses
• Seaweed
• Sea lettuce (Ulva lactuca)

Pro Tip: It's true to say these large opisthobranch gastropod molluscs have an incredible sense of smell. They can detect the faintest of scents using their rhinophores (sensitive chemoreceptors).

Types of Sea Hares

How Do Sea Hares Reproduce?

By and large, the reproductive process of the sea hare begins with the formation of a mating chain (a cluster of individuals simultaneously acting as males and females).

Nonetheless, the first sea hare of the chain will only act as a female, and the last will only act as a male. But, the members in the middle will act as both genders.

Because the mating chain usually involves multiple individuals, it tends to maximise successful reproduction and thriving populations.

And the outcome...:

Following copulation, usually in late summer, sea hares lay a long spaghetti-like mass of yellow or pink coloured tiny eggs - often resulting in thousands of eggs attached to rocky substrates.

The tiny eggs develop and hatch into veligers (planktonic larvae). The larvae feed on microscopic algae as they drift in the water column.

Several weeks later, the larvae find an appropriate place to settle to the ocean floor and begin further development into juvenile sea hares.

Depending on the species, the life cycle of a sea hare is relatively short, ranging from as little as a few months up to one (1) year. Furthermore, the single reproductive event known as semelparity means the parents will die soon after laying the eggs.

Interesting Fact: Sea slugs have become extremely important to the development of some medications. As part of future research projects, scientists are actively studying how sea hare and nudibranch anatomy functions.

Sea Hare Predators and Threats

So, what eats sea hares? In fact, sea hare Aplysiida have a chemical defense system that enables them to secrete purple ink as a "smoke screen" when they feel threatened.

Sea hare lifespan rarely lasts longer than one (1) year and they will perish and die soon after reproduction. Some of the common marine animals that prey upon sea hares include:

• Cephalopods (especially octopuses)
• Crustaceans (e.g. crabs, lobsters)
• Humphead wrasse (Cheilinus undulatus)
• Porcupine fish (Diodontidae)
• Pufferfishes (Tetraodontidae)
• Sea stars (starfish)
• Shorebirds and gulls
• Triggerfish (Balistidae)

Pro Tip: After properly preparing sea hares to avoid the toxic compounds accumulated in their diet, some humans choose to consume them - especially in China, the Philippines, and Hawaii.

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