Let's start our acquaintance with the smallest representative in the sea hare family (Aplysiidae) - the dwarf sea hare (Aplysia parvula). It lives at depths from 5 to 24 meters. Its size does not exceed 70 mm. This small gastropod with rabbit-like ears (actually sensory appendages) is brown, maroon or olive green, and can also be spotted. Dark colors are widespread in the Red Sea and western Indian Ocean, and are also found in the western Pacific, although not frequently. Pale specimens have a cream-colored body with black edges on the oral tentacles, legs, and parapodia.
Both color forms are small. Although, pale individuals of the dwarf sea hare grow up to 120 mm. There is also a black form: the body is dark brown or black, sometimes with white speckles, and with a pale pink or purple edge on the parapodia and tentacles. The pale form is found in shallow intertidal areas with seagrass, while the dark form is found on coral reefs in more exposed areas. Aplysia feeds on various types of algae. Dwarf sea hare eggs are masses of tangled, sticky strings of orange, green or brown that can be found in rocks or among seaweed.
Aplysia californica or California sea hare is one of the largest opisthobranch gastropods in this family. This species lives in the Pacific coast of North America (in California) and Northern Mexico, but can also be found near Florida. These sea slugs prefer to inhabit light areas where algae grows vigorously, at depths of up to 20 meters. The maximum size documented for the California sea hare was 75 cm, although most individuals are typically half that length. Adult animals can weigh up to 7 kg. Only a closely related species, the black sea hare (Aplysia vaccaria), can grow even larger. There are not so many people who want to eat a sea hare. These include the giant green anemone (Anthopleura xanthogrammica), starfish and lobsters. For protection, the sea hare acts almost the same as the cuttlefish, using reddish-purple ink, which it releases from the mantle cavity.
Like all sea hares, Aplysia Californian is a hermaphrodite, and for mating it forms chains, in which there are sometimes up to 20 animals, so each animal can act as a female or a male. Fertilized and laid eggs are yellow-green in color, and after 8-9 days they turn brown. Mating occurs in the summer months as soon as the water temperature rises to 17 degrees Celsius. The clam reaches reproductive maturity 85 days after hatching (or 133 days after laying fertilized eggs, the planktonic stage). Development of the nervous system lasts a total of 140 days. The full life cycle is about a year, but can be extended due to low temperatures.
And a few more words about the California black sea hare (Aplysia vaccaria), an incredibly large sea slug. This gastropod is not only the largest in the family Aplysiidae, but also the largest of all known sea slug species. The maximum size that was officially recorded for the black sea hare was 99 cm and weighed almost 14 kg. So far, today it remains the world's largest mollusk among living gastropods. Unlike other members of this family, the black hare is not capable of producing ink. It feeds on brown algae, which, apparently, is what gives it its dark color.
Aplysia(lat. Aplysia) - one of the largest representatives of opisthobranch mollusks, also called sea hare.
Aplysia is characterized by the position of the gills on the right side of the body under the fold of the mantle (in the mantle cavity). The sea hare has a pair of sensitive appendages on its head. On the sides, the Aplysia's body is covered with a pair of massive blades, which straighten out and, contracting in waves, allow the Aplysia to swim for quite a long time. The coloring of aplysias is very beautiful and varied: it can be dark purple with white spots scattered over it, then these spots are scattered over an ocher-yellow background, or dirty gray and yellowish tones without sharply defined spots predominate. The genus Aplysia is widely distributed throughout the warm seas of the globe; it includes a fairly large number of species.
Sea hares are hermaphrodites and usually mate in a chain. So the individuals in the middle of the chain perform alternately male and female functions with those in front or behind.
Aplysia as model organisms
The nervous system of the sea hare consists of only 20,000 nerve cells. They are so large (can reach up to 1 mm in diameter) that they are visible to the naked eye. Aplysia nerve cells are clearly distinguishable visually: they are painted in different colors. It was these advantages that the Nobel laureate used
In the picture on the first cover is a brown hare that lives in Europe, Asia, and was also brought to America and took root there. And in our country it was specially resettled even before the war as a valuable hunting object, including fur.
It’s hard to say why, but the names of some animals that are little or even completely unrelated to hares include the word “hare.”
The sea hare is the furthest away from real hares. In fact, it is a mollusk, something like a slug that lives in warm seas. Its scientific name is Aplysia. Some species of sea hares are close in size to land animals, reaching a length of 75 cm and a weight of about two kilograms. Sea hares are a favorite experimental subject of neurobiologists: the entire nervous system of these mollusks consists of 20 thousand cells, and the cells are so large, up to a millimeter in diameter, that they are visible to the naked eye. It is convenient for biologists to inject various compounds into these neurons, connect electrodes to them and record the reaction of the nervous system.
Somewhat closer to our land hares is the sea hare - fish. Still a vertebrate animal. But why she was called that is unclear. The mollusk's head part with two thick tentacles at least slightly resembles a hare's face with ears, but the fish has nothing in common with hares in appearance. Rather, her scientific name suits her - monstrous chimera. It is edible, but has no significant commercial value.
Even closer to land hares is also a mammal, the sea hare, also known as the bearded seal - the largest seal in the fauna of Russia. Length up to 2.5 m, weight up to 300 kg. Distributed in all circumpolar seas of the Northern Hemisphere, these seals were even found in the area of the North Pole. Previously, northern peoples hunted bearded seals; the skin was used for kayaks, the meat and fat were used for food. But now hunting is prohibited, the species is close to extinction.
And finally, the closest relative of the hare is the earthen hare, a large jerboa from the order of rodents adjacent to the order of lagomorphs. The ground hare lives in the steppes in southern Russia, Turkmenistan, Kazakhstan, Uzbekistan and Ukraine, and northern China. Like many rodents, it can harm agriculture. Long legs allow this small animal (weight up to 300 g) to jump three meters in length.
Even those living creatures that seem completely defenseless actually know how to defend themselves from predators. And here the defense methods of the Aplysia mollusk are very interesting - it can release various substances into the water that either deprive the predator of the sense of smell or create an “odor phantom” that distracts the hunter from the prey itself. But that's not all...
Life of the nudibranch mollusk Aplysia ( Aplysia californica), which is also called the sea hare, is very, very difficult. The fact is that it has many enemies, but there is absolutely no place to hide from them - after all, Aplysia, unlike its relatives, is completely devoid of a shell. At the same time, it is hunted by almost all marine predators - fish, large crayfish, octopuses, and cuttlefish. Looking at this, it becomes surprising why this cute and defenseless mollusk still exists on our planet!
However, the sea hare still has some protective devices. For example, it can, like cephalopods, throw an ink stain into the water. Scientists knew about this for a long time, but did not understand what the point of such protection was. Indeed, an octopus or cuttlefish, which can swim quickly, always manages to escape before their “smoke screen” clears. But the sea hare is a slow-moving creature, and even while the spot “hangs” in the water, it still does not have time to go far.
However, as observations show, even in this case the mollusk most often remains alive. But why? Scientists from the University of Georgia (USA) decided to solve this mystery. They analyzed the chemical composition of the Aplysia ink cloud and found that it contained a substance such as opaline. It was known that it could suppress the sense of smell of some marine inhabitants. So maybe it is he who makes the mollusk invisible to his pursuers?
The researchers decided to test their hypothesis. They took opaline from the glands of the sea hare (it should be noted that it is produced separately from the coloring pigments) and applied it to the lobster's antennae, which in this arthropod play the role of an olfactory organ. After that, an extract from shrimp was added to the aquarium with this lobster, which the predator feeds on in the wild and, therefore, knows their smell by heart.
As a result, it turned out that the lobster did not react at all to the delicious smell that was quite familiar to it. Most likely because I just didn't feel it. As scientists write in an article published in Journal of Experimental Biology, according to their research, those neurons that are responsible for chemoreception, as well as the motor nerve cells associated with them, remained completely inactive all this time. And this is very strange - usually they are immediately excited by the smell of food and excite the hunting reflexes of the crayfish.
It turns out that opaline is indeed capable of completely suppressing the sense of smell. As Professor Charles Derby, who led the study, said, this substance isolated from the glands of the sea hare literally clogs the “nose” of the predator. And opaline does this in the following way - it sticks to the receptors on the lobster’s antennae and simply physically prevents odor molecules from reaching them.
It is quite obvious that as a result of such an opaline attack, the predator completely loses its sense of smell for some time. And, what is most interesting, the appetite disappears along with it - after all, if there is no smell, then hunting behavior is not aroused. Well, while he is cleaning the antennas from the scorch sticking to them, even such a slow-moving and bumpkin as the sea hare always manages to climb into some crevice between the stones and hide.
However, as it turned out, that's not all. Further research showed that Aplysias also have a second level of protection. It turns out that the same ink mixture of this mollusk contains many different amino acids, which, when they reach the olfactory receptors of predators, create a very attractive smell of prey. As a result, the predator begins to hunt precisely this “scent phantom”, and not the real sea hare. Apparently, this defense works if the predator is not affected by opaline.
Sea hare (genus of gastropods) sea hare(Aplysia), a genus of marine gastropods of the opisthobranch subclass. Body length up to 40 cm. There are 2 pairs of head tentacles, of which the rear one is shaped like a hare’s ears (hence the name). The thin lamellar shell is covered with a mantle. In the mantle cavity there are glands that secrete a toxic colored liquid. The leg has lateral blades used for swimming. About 35 species. Herbivorous; They live mainly in tropical seas. Large nerve cells M. z. - object of neurophysiological research. Rice. see Art. Gastropods.
Great Soviet Encyclopedia. - M.: Soviet Encyclopedia. 1969-1978 .
See what “Sea hare (genus of gastropod mollusks)” is in other dictionaries:
Aplysia (Aplysia) is a genus of gastropod mollusks from the order Opisthobranchiata, suborder Tectibranchata, belonging to the family M. hares (Aplysiidae). Features of the family: the internal shell is underdeveloped, or its... ... Encyclopedic Dictionary F.A. Brockhaus and I.A. Ephron
I The bearded seal (Erignathus barbatus), a pinniped of the true seal family. Length 2.2 2.6 m, weighs 225,360 kg. The hair is grey-brown, sometimes with several light spots on the back. The fur of a newborn is dark... Great Soviet Encyclopedia
