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Aplysia \A*plys"i*a\, n. [Gr. ? a dirty sponge, fr. ? unwashed; 'a priv. + ? to wash.] (Zo["o]l.) A genus of marine mollusks of the order Tectibranchiata; the sea hare. Some of the species when disturbed throw out a deep purple liquor, which colors the water to some distance. See Illust. in Appendix.


n. Any sea slug of the genus (taxlink Aplysia genus noshow=1).


Aplysia is a genus of medium-sized to extremely large sea slugs, specifically sea hares, which are one clade of large sea slugs, marine gastropod mollusks. The general description of sea hares can be found in the article on the superfamily Aplysioidea.

These benthic herbivorous creatures can become rather large compared with most other mollusks. They graze in tidal and subtidal zones of tropical waters, mostly in the Indo-Pacific Ocean (23 species); but they can also be found in the Atlantic Ocean (12 species), with a few species occurring in the Mediterranean.

Aplysia species, when threatened, frequently release clouds of ink, it is believed in order to blind the attacker (though they are in fact considered edible by relatively few species). Following the lead of Eric R. Kandel, the genus has been studied as a model organism by neurobiologists, because its siphon-withdrawal response, as studied in Aplysia californica, is mediated by electrical synapses, which allow several neurons to fire synchronously (Kandel et al., 2000). (See : Aplysia gill and siphon withdrawal reflex) This quick neural response is necessary for a speedy reaction to danger by the animal. Aplysia has only about 20,000 neurons, making it a favorite subject for investigation by neuroscientists. Also, the 'tongue' on the underside is controlled by only two neurons, which allowed complete mapping of the innervation network to be carried out.

Usage examples of "aplysia".

Kupfermann, I, Castellucci, V, Pinsker, H, and Kandel, E R Neuronal correlates of habituation and dishabituation of the gill-withdrawal reflex in Aplysia.

Nonetheless certain important general neurobiological principles have emerged from the last decades of experimentation, on chicks, on the hippocampus, on Aplysia, and on many other experimental models which I have not found space to mention here.

An alternative molluscan species, Hermissenda, has been championed as a rival to Aplysia by the Woods Hole-based neurophysiologist Dan Alkon.

Aplysia motor neurons following sensory stimulation shows that they are responding both directly, monosynaptically, and polysynaptically, by way of interneurons.

Aplysia may be a special case because it is easy to study, but it would be straining credulity to believe that it organized its learning behaviour along fundamentally different principles from those of other invertebrates, or indeed vertebrates with reasonably sized nervous systems.

The capacity to show habituation, he observed, occurs relatively early on in the development of the baby Aplysia, while sensitization does not appear until a relatively late stage.

Aplysia with Ladislav Tauc in Paris in the 1960s, saw the potential of the organism, initially for the study of short-term processes such as habituation, and over the subsequent quarter-century in New York he has made its study peculiarly his own and that of the generations of researchers who have cut their teeth in his Columbia laboratory.

Aplysia a strategic choice for researching the neurobiology of certain basic forms of memory formation.

Despite the remarkable analogy between habituation and sensitization in the intact Aplysia and the responses of its isolated sensory-motor synapse, which certainly fulfill some of my criteria, there is a conspicuous gap in the logic.

Can habituation, sensitization, or associative learning of the gill and siphon withdrawal reflex occur in Aplysia if the key sensory-motor synapses are lesioned (Criterion Five)?

Personal relations among researchers working on Aplysia, and between the Aplysia group in general and those working with other molluscans, such as Dan Alkon and his Woods Hole colleagues studying Hermissenda (Chapter 7), have not always been easy and were sometimes abrasive, to the extent that they attracted science writer Susan Allport to devote an entire book to them.