Sessile


Sessile

Sessile is a term in biology with two distinct meanings:

In botany and medicine

In botany, sessile means "without a stalk", as in flowers (pedicel) or leaves (petiole) that grow directly from the stem or peduncle; however, in limnology, sessile vegetation are any organisms anchored to the benthic environment. The term is also used in medicine to describe tumors and polyps that lack a stalk, as opposed to those that are pedunculated.

In zoology

In zoology sessile animals are those which are not able to move about. They are usually permanently attached to a solid of some kind, such as a rock, or the hull of a ship in the case of barnacles. Corals lay down their own substrate.

Sessile animals typically have a motile phase in their development. Sponges have a motile larval stage, which becomes sessile at maturity. In contrast, many jellyfish develop as sessile polyps early in their life cycle. Many sessile animals, including sponges, corals, and hydra, are capable of asexual reproduction "in situ" by a process of budding.

Sessile animals

Sponges

Most of the 10,000 species of sponges are marine animals; only about 100 species live in fresh water. Sponges are sessile animals that come in a wide variety of sizes and shapes and are adapted to different movement patterns of water.Sponges reproduce both sexually and asexually. In most species, a single individual produces both egg and sperm, but individuals do not self-fertilize. Water currents carry sperm from one individual to another. Asexual reproduction is by budding and fragmentation.

Clumping is a behavior in an animal, usually sessile, in which individuals of a particular species group close to one another for beneficial purposes.

ee also

* Sessile oak


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  • sessile — [ sesil ] adj. • 1611; lat. sessilis ♦ Organe sessile, attaché directement, dépourvu de tige, pédoncule ou pétiole. Bot. Les feuilles sessiles de l œillet. Méd. Tumeur sessile, sans pédicule. ⊗ CONTR. Pédonculé. ● sessile adjectif (latin sessilis …   Encyclopédie Universelle

  • Sessile — Ses sile, a. [L. sessilis low, dwarf, from sedere, sessum, to sit: cf. F. sessile.] 1. Attached without any sensible projecting support. [1913 Webster] 2. (Bot.) Resting directly upon the main stem or branch, without a petiole or footstalk; as, a …   The Collaborative International Dictionary of English

  • sessile — 1725, adhering close to the surface, from L. sessilis pertaining to sitting, from sessum, pp. of sedere to sit (see SEDENTARY (Cf. sedentary)). Meaning sedentary first recorded 1860 …   Etymology dictionary

  • sessile — [ses′il, ses′īl΄] adj. [L sessilis < sessus, pp. of sedere, to SIT] 1. Biol. a) attached directly by its base b) permanently fixed; immobile 2. Bot. having no pedicel or peduncle; attached directly to the main stem, as the flower and leaves of …   English World dictionary

  • sessile — adjective Etymology: Latin sessilis of or fit for sitting, low, dwarf (of plants), from sessus, past participle of sedēre Date: circa 1753 1. attached directly by the base ; not raised upon a stalk or peduncle < a sessile leaf > < sessile bubbles …   New Collegiate Dictionary

  • Sessile — Cette page d’homonymie répertorie les différents sujets et articles partageant un même nom. Des animaux marins sessiles : ici, une éponge (Clathrina Clathrus). L adjectif « sessi …   Wikipédia en Français

  • sessile — Having a broad base of attachment; not pedunculated. [L. sessilis, low growing, fr. sedeo, pp. sessus, to sit] * * * ses·sile ses īl, əl adj 1) attached directly by a broad base: not pedunculated <a sessile tumor> 2) firmly attached (as to… …   Medical dictionary

  • sessile — (sè ssi l ) adj. 1°   Terme de botanique. Il se dit d une partie quelconque qui n a pas de support particulier, qui repose immédiatement sur une autre. Fleurs sessiles. Feuilles sessiles.    Laitues sessiles, celles qui ne s élèvent pas. 2°   En… …   Dictionnaire de la Langue Française d'Émile Littré

  • sessile — sès·si·le agg., s.m. 1. agg. TS bot. di organo vegetale, che si inserisce direttamente in un altro organo o in un ramo, senza il sostegno di un peduncolo o di un picciolo: fiore, foglia sessile Contrari: 2peduncolato. 2. agg. TS zool. di organo,… …   Dizionario italiano

  • SESSILE — adj. des deux genres T. de Botan. Il se dit Des parties qui sont immédiatement fixées et comme assises sur celles d où elles naissent, qui ne sont point portées par un pédicule, par un pétiole, etc. Feuilles sessiles. Fleurs sessiles. Anthères… …   Dictionnaire de l'Academie Francaise, 7eme edition (1835)


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