Rabbits in the ocean

The Year of the Rabbit is here, and the streets and alleys are filled with various images of rabbits. In the ocean world, there is a little cutie whose name also contains the word "rabbit".

It is today’s protagonist - the sea hare.

- Aplysia -

Image source:

https://www.sohu.com/a/210836437_219830

Sea hares are a general term for organisms in the order Anaspidea of ​​the subclass Opisthobranchia of the class Gastropoda, and are a member of the sea slug family. When they drag their soft bodies across the seafloor, the tentacles on their heads extend outward in an eight-shaped pattern, like snails on land. When they stop moving and rest, their tentacles stand upright like rabbit ears, hence the name sea hares.

Sea slugs come in a variety of shapes, with the smallest being only about 2mm in size and the largest, the California sea slug, growing up to 75cm in length.

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The California sea hare feeds mostly on red algae, and its body color is also red and pink. They are also excellent materials for neurobiology research, and they made great contributions to Eric Richard Kandel's Nobel Prize in Physiology and Medicine.

As a mollusk, the sea hare has a soft and fragile body, which makes it not very aggressive. In addition, its poor elasticity and slow movement speed give it a natural disadvantage in resisting natural enemies. So how does the sea hare protect itself in the complex habitat of the seabed?

Superb camouflage

Bursatella leachii Blainville, 1817

Sea hares mostly feed on seaweed, which contains chlorophyll. Their bodies will change to the color of the seaweed they eat. So whenever sea hares arrive at a place, they will eat a lot of local seaweed. When the color changes to match that of the seaweed, they will hide in the seaweed to camouflage themselves, thus achieving the purpose of hiding.

However, the camouflage of the sea hare is not as simple as imitating the appearance. The green sea hare living in the salt marshes of New England and Canada can photosynthesize and is the first animal discovered by humans to produce the plant pigment chlorophyll. The sea hare not only simulates the color of seaweed, but also "borrows" the identity of the seaweed producer.

Chemical Warfare Master

In addition to disguising themselves as seaweed or algae, sea slugs also have a very strong active defense mechanism - chemical defense.

Aplysia has two glands: ink gland and opaline gland, which release different secretions. The ink gland secretes purple juice, while the opaline gland releases highly viscous white chemical components. These two substances mix in the mantle cavity of the sea slug, and through the contraction of the mantle muscles, purple viscous secretions are ejected. This is the first mechanism of chemical defense of the sea slug - smoke screen war affects vision.

Image source:

https://www.163.com/dy/article/D3PJREH50511LCGO.html

If the sea slug is caught by a predator, the smoke screen can still work. The smoke screen contains a mixture of intermediates of lysine synthesis and hydrogen peroxide, which can suppress the senses of its predator and make the predator mistakenly think that the "smoke screen" is the real food. The irritation of the smoke itself will make the predator lose interest in hunting the sea slug, giving the sea slug a chance to escape.

Unique mating method

Sea hares are very special creatures. Due to the scarcity of individuals of the same size and their slow movements, mating is difficult, so sea hares are hermaphrodites, that is, a sea hare has two complete sets of male and female sexual organs. Except for a small number of sea hares who like to mate in pairs, most sea hares generally adopt two unique mating methods: mating chain

Image credit: Aplysia dactylomela mating chain. PHOTO: Alison Miller.

The vagina of the sea slug is located in the back center, and the external genitalia are on the right side of the head and body. When two sea slugs mate, they form a body position with one in front and one behind, connected head to tail. Therefore, more sea slugs can join in, forming a very long chain structure. If the "locomotive" meets the "tail", then a closed circle can even be formed.

Sea fans

After sea hares lay eggs, there is a jelly-like substance secreted by the albumen glands between the eggs, which sticks together into a ribbon-like egg cord, which contains tens of thousands of eggs, some of which can reach hundreds of meters. The beach can produce quite a lot of eggs, but because of the large loss (all eaten), only a small part can be hatched in the end. Sea hares are called "sea mealworms" in Fujian and Guangdong, and their egg cords are called "sea vermicelli", which is a very interesting local niche delicacy.

Image source:

https://www.163.com/dy/article/D3PJREH50511LCGO.html

If we encounter sea slugs in the intertidal zone, remember to observe and interact with them in an appropriate and non-interfering manner.

Image source: mt.sohu.com/20180531/n539348386.shtml

Author: Fish Ball Expert Reviewer: Zhang Xiaofeng