Cerata
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Cerata (singl. Ceras, old gr. Ἡ κεραία (keraia) = horn, old gr. Κερας (keras) = - horn, antlers) are skin appendages that sea snails or the maritime hind gill snails on their back (dorsal) or on the sides ( lateral).
function
Cerata are skin outgrowths that increase the animal's skin surface. Since the gas exchange (CO 2 for O 2 ) required for cell metabolism depends on the number of specialized cells available on the surface, the Cerata promotes and improves breathing.
In the picture on the right you can see the cerata of a Fiona pinnata . Inside the Cerata there are strongly fanned membranes on the front. These membranes are bundled in small, downwardly running vessels, which lead out of the cerata into a larger central strand.
In some groups of snails within the nudibranch , the cerata are traversed by a fine, central papillary . This connects the Cerata to the digestive tract. In this way, substances can be transported into and out of the cerata, and the cerata can take on secondary functions in addition to their main function (support for breathing) .
In the picture on the left ( Janolus fuscus ) you can clearly see the dark papillary in the center and three sections of the cerata: a light base, a yellow top with nettle capsules, and the cerata tips.
Most thread snails feed on cnidarians ( Cnidaria ) and can safely ingest their nettle capsules ( nematocytes ). But instead of digesting them, they are stored intact in a tense state in special skin sacs (nettle sacs) opening outwards at the tips of the cerata. In dangerous situations or when the cerata tips break, the nettles are then shot through nettle channels. Since the nettle capsules were not produced in-house, these animals are also called nettle thieves ( kleptocnides ).
Other groups such as B. Broad-footed snails of the genus Aplysia , also called sea hares, use the Cerata for glare tactics. The Aplysia cannot actively defend themselves with the help of nettle capsules, but they store unpleasant-smelling secretions in their cerata. When attacked, they (just like lizards their tails) repel one or more of the cerata. These linger and contract heavily for some time. At the same time, the stinking secretion flows out and leaves a white to purple cloud in the water. The calculation of such tactics is that potential attackers are irritated by the contracting cerata or the spreading dyes or are repelled by stinking secretions and thus escape time is gained.
Individual evidence
- ↑ Brusca, RC & Brusca, GJ 2003. Invertebrates , 2nd edition; ISBN 0-87893-097-3 .
- ^ Cleveland P. Hickman et al .: Zoology. Pearson Studium, 2008, ISBN 978-3827372659 , pp. 515-516.
- ^ Forum Sea Slug ( Memento of March 13, 2012 in the Internet Archive ), accessed November 12, 2009
Web links
- Sea Slug Forum ( Memento from February 6, 2012 in the Internet Archive )