Common sea hare
| Common sea hare | ||||||||||||
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Common sea hare ( Aplysia punctata ) |
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Aplysia punctata | ||||||||||||
| G. Cuvier , 1803 |
The common sea hare ( Aplysia punctata ) is one of the most common sea hare species in Europe. Characteristic are the parapodial lobes growing around the atrophied, ingrown shell, a red-red-brown or olive-green-black skin color and dot patterns or grains.
External features
Body shape
The common sea hare has an irregular, longitudinally symmetrical body. It consists of three sections: a head area that seamlessly merges into a longer, widening neck area. The neck area in turn opens into a voluminous abdomen, which is about half the length of the body.
Head
At the front end of the head there are two tentacles near the throat, which have a flat rolled shape. Two rhinophores grow from the back of the skull or the beginning of the neck area . The rhinophores have a notch that is about two thirds of their length. On the inner surface are chemoreceptors and neurons that connect them to the nervous system. With them u. a. Perceived food sources. Few of the rhinophores are two dark, point-shaped eyes with one yellow.
Abdomen
In the back of the body there is a shell. During the evolutionary regression it is only very thin and completely enclosed by skin. It covers the viscera. From about the middle of the body, two parapodial lobes grow laterally on top of the back of the body. They enclose the area of the shell. Above, feather gills grow out between the parapodial lobes on the back. They are covered and thus protected by the parapodial lobes.
Color
The color of younger animals is red to red-brown. Older adults are darker in color, varying from olive green to brown to almost black. The color is due to the ingestion of dyes and thus the color change that comes with age is diet-related.
Surface
pattern Aplysia punctata mostly shows surface patterns . These can consist of white, black, gray, dark brown fine to medium dots, which sometimes also concentrate into spots with satellite dots. Lines that give a grain are also observed.
The points are usually evenly distributed on the body. Sometimes there are also concentrations and areas that seem pointless. The surface pattern gives them the addition of species punctata .
Size
Aplysia punctata is of rather moderate size within the genus Aplysia . Specimens from 2 to 4 cm have been sighted. But they also grow up to 20 cm.
Way of life
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Diet
Sea hares are vegetarian. Younger sea hares prefer softer types of red algae. They move on their leaves, systematically graze them and with them eat the algae that live on them.
Older snails tend to feed on brown seaweed and larger green algae.
Due to the age-related changing preference in the diet, there is less intra-species competition between young and old animals.
Habitat
Aplysia punctata occurs in the Atlantic to the Canary Islands , in the North Sea and in the Mediterranean .
It lives in shallow waters near the coast, as a young animal in deeper areas with red algae growth, as an old snail preferably in shallower areas up to tidal waters with seaweed and green algae growth.
Locomotion
Aplysia punctata glides on the foot, on the ground and on plant leaves. She also climbs aquatic plants. Unlike Aplysia fasciata , however , Aplysia punctata is not known to be a swimmer.
Reproduction
The common sea hare is like all sea hare a hermaphrodite and has a hermaphrodite gland . He is not self-fertilizing, but needs a partner for fertilization. One animal takes on the role of the male, another that of the female. The genital opening is on the back between the parapodial lobes. From there, a sperm notch directs the sperm to the penis of the male animal. With the penis, the sperm is then introduced into the genital opening of the animal acting as a female. The fertilization usually takes place in pairs with changing roles or even in chains.
Shortly after fertilization, the sea hares lay yellowish-brown, coiled spawning lines with up to 135,000 eggs. The spawning lines are attached to more solid objects such as plants or objects and then left to rest. Protected by jelly-like shells, they mature and later hatch as veliger larvae . The larval phase is spent as floating plankton. At the end of this they sink to the ground and, after a metamorphosis, begin the last phase of life as juvenile snails on the ground.
Reproduction often takes place in the last phase of the animal's life. For example, it has been observed on English coasts that the Aplysia punctata appear at certain times near the coast and at river mouths, spawn and then die.
Self-protection
In case of danger or direct contact, Aplysia punctata emits a whitish-purple liquid. They also absorb color pigments from the plant with their food, so that they take on their color. Supported by the surface pattern, they are therefore hardly noticeable in the water between the plants.
Population
Aplysia punctata sometimes occur in large populations, presumably when there is abundant algae growth. But this also makes the population vulnerable. If the increase in food in the biotopes ceases, mass deaths occur. The remains of the animals are then washed ashore in large quantities.
Web links
literature
- Bickmeyer, U .; Drechsler, C .; Kock, M. & Assmann, M .: 07/2004; "Brominated pyrrole alkaloids from marine Agelas sponges reduce depolarization-induced cellular calcium elevation" ; Toxicon 44 : 45-51; doi : 10.1016 / j.toxicon.2004.04.001
- Thompson, TE: Biology of Opisthobranch Molluscs , Vol 1; Ray Society: London 1976
- Wertz, A .; Rössler, W .; Obermayer, M. & Bickmeyer, U .: April 6, 2006; "Functional neuroanatomy of the rhinophore of Aplysia punctata" ; Frontiers in Zoology 3 : 6; doi : 10.1186 / 1742-9994-3-6
Individual evidence
- ↑ Rudman, WB: Aplysia punctata Cuvier, 1803 ; In: Sea Slug Forum; Australian Museum, Sydney; September 29, 1999; http://www.seaslugforum.net/factsheet/aplypunc
- ^ Henry, MS: "Markings on Aplysia punctata" ; In: Sea Slug Forum; Australian Museum, Sydney; August 17, 2006; http://www.seaslugforum.net/find/17444
- ↑ tracks Stein, P .: Aplysia punctata in Germany ; In: Sea Slug Forum; Australian Museum, Sydney; May 31, 2002; http://www.seaslugforum.net/find/7085
- ↑ Rudman, WB: "Comment on Aplysia punctata mating by Jim Anderson" ; In: Sea Slug Forum; Australian Museum, Sydney; August 20, 2007; http://www.seaslugforum.net/find/20472
- ^ Rudman, WB: "Comment on Sea Hares - mating chains by Erwin Koehler" ; In: Sea Slug Forum; Australian Museum, Sydney; June 4, 1998; http://www.seaslugforum.net/find/140
- ↑ Horton, A .: "Observations on Aplysia punctata" ; In: Sea Slug Forum; Australian Museum, Sydney; October 2, 1999; http://www.seaslugforum.net/find/1379