Aplysia
California sea hare ( Aplysia californica ) with ink cloud
Aplysia ( sea hare German, not to be confused with the eponymous fish family Cyclopteridae ) is a genus of sea snails of the order opisthobranch ( Opisthobranchia ). They are known primarily because they produce with the largest known worm: Copies of Aplysia vaccaria reach a length of up to 75 cm and weigh around 2 kg ( 4.4 lb). However, there are species that are only about 2-6 cm centimeters tall. Within the Breitfußschnecken is with them the evolutionary regression of the shell in the middle stage, ie they still have a shell that no longer is but externally, but internally. It is located in the abdomen above the visceral sac and is fully embedded in tissue.
The particularly large neurons and not overly complicated, manageable nervous system they make, particularly Aplysia californica, an outstanding object of research in neurology. So the Nobel Laureate Eric R. Kandel explored at their synapses among others learning at the cellular level.
The German name lumpfish (English Sea hare, double lièvres de mer ) probably comes from his head shape, because in the water resemble the front part with the flat throat tentacles and the Rhinpheren with eyes underneath with a little imagination a rabbit's head, especially when the animal with the massive acting rump cranes his head forward -up.
Way of life
The mantle lobes have different functions. First, it provides state width is increased. Other types they use to swim with regular, wavy contractions so. The Parapodiallappen have more of a sideways emanating from the body airfoil shape.
Sea hares live according to the larval stage, which is often spent as a driving plankton, mostly on the seabed. They colonize areas with denser vegetation, which provides them with food such protection. Thus they belong to the benthos. However, some species such as Aplysia brasiliana can swim freely and even put larger distances.
Lumpfish are vegetarian. They eat different algae, seaweed and seagrass species. Here are rasped plant parts with the rasping tongue ( radula ), which then pass through the digestive tract. With the plant parts is also food such as nursery smaller species of algae ingested.
A characteristic of many types is the ability to produce an intensely purple -colored ink cloud defense. This dye is obtained according to present knowledge of eaten red algae and is discharged through special glands on their backs in the area.
For protection from predators, there are species that additionally save the toxin aplysiatoxin. This toxin is a product of blue-green algae ( cyanobacteria ), which grow in certain places and seaweed are absorbed by the worm in food intake with. As for the blue-green algae eaten, so the main way Lyngbya majuscula is cited as a source of food for snails. In addition to the Lyngbya majuscula but more blue-green algae of the genera Schizothrix and Planktothrix are known, from which snails can win aplysiatoxin and thus come as a poison source in question.
Inside systematics
In the course of time, many species of the genus Aplysia found and described. However, do not seem to be new any kind, but there are many synonyms suspected. The reason for this is that some species are present but far global than suspected that the discoveries and sightings occur locally and networking took place only in recent years, and that there has been only one revision of Aplysia by NB Eales (1960 ) gave. This yielded 36 species. Since then, however, there were more species descriptions.
A selection of Apylsia species is:
- Aplysia brasiliana ( spotted sea hare ) - S. Rank, 1828 (possibly Aplysia fasciata = ) Distribution: Western Atlantic from New Jersey to Brazil; Eastern Atlantic ( to Ghana)
- Length: up to 27 cm
- Colour: variable
- Distribution: worldwide in tropical and temperate seas
- Color: from light gray to green to dark brown
- Large black rings on the surface; not floatable
- Distribution: Eastern Atlantic, Mediterranean
- Thin, yellow inner shell; swims relatively happy
- Distribution: North America, Western Atlantic
- Distribution: Western Australia, New Zealand
- Length: about 40 cm
- Distribution: Eastern Atlantic, West Africa
- Length: 40 cm
- Color: dark brown to black
- Sometimes bordering a red stripe the parapodia and oral tentacles from
- Distribution: Western Australia
- Length: 60 cm
- Color: dark brown to black
- Skin secretions are very disgusting; stranded specimens are to be responsible for the deaths of dogs
- Distribution: Worldwide in all warm seas.
- Color: various, from gray to light brown.
- No purple gland, so no ink delivery; rear end of the foot can be used as suction
- Distribution: NW- Pacific
- Length: 30 cm
- Color: dark brown to purple - black, dotted with white spots.
- Distribution: Eastern Atlantic
- Length: 40 cm
- Color: black to dark brown; not stain
- Distribution: Indian Ocean, Western Pacific
- Little brown eye patch
- Distribution: Worldwide in warm to temperate seas
- Length: 6 cm
- Color: brown to green spots
- Distribution: Mediterranean and in parts of the North-East Atlantic
- Length: usually 15, max. 20 cm
- Color: bright spots and dots, basic color very variable
- Floats rarely
- Distribution: Eastern Australia, Japan
- Distribution: Australia
- Length: 15 cm
- Not clearly described
- Distribution: California Pacific Coast
- Length: very large (up to 75 cm)
- Color: black
- Purple ink; large inner shell
Outer systematics
The taxonomy of the worm is subject to revision and change. Therefore, there are different classifications. On J.Thiele (1929-1935) is usually considered going back as classical. She was recognized until the 1990s. A more modern and the last established on purely morphological approaches to systematics is that of Ponder & Lindberg (1997). A recent phylogenetic systematics oriented Bouchet & Rocroi goes back to ( 2005).
Taxonomy of Bouchet & Rocroi (2005)
According to the taxonomy of Bouchet & Rocroi (2005) Aplysia are a genus within the clade of Mixed - Kiemer ( Heterobranchia ):
- Class Gastropoda Cuvier, 1797 Clade Heterobranchia Gray, 1840 informal group Opisthobranchia Milne Edwards, 1848 Clade Aplysiomorpha P. Fischer, 1883 Superfamily Aplysioidea Lamarck, 1809 Family Aplysiidae Rafinesque, 1815 Genus Aplysia Linnaeus, 1767
Taxonomy of Ponder & Lindberg (1997)
According to the taxonomy of Ponder & Lindberg (1997) the Aplysidea are an order within the superorder of Mixed - Kiemer ( Heterobranchia ):
- Class Gastropoda Cuvier, 1797 Subclass Orthogastropoda W. F. Ponder & D. R. Lindberg, 1996 Subclass Apogastropoda Salvini - Plawen & Haszprunar, 1987 Superorder Heterobranchia Gray, 1840 Order Opisthobranchia Milne Edwards, 1848 Subordination Anaspidea P. Fischer, 1883 Superfamily Aplysioidea Lamarck, 1809 Family Aplysiidae Rafinesque, 1815 Genus Aplysia Linnaeus, 1767