View source for Instar

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==Definition==
*''according to Hottinger (2006):''
'''INSTAR''' - a single step in the discontinuous growth process of most foraminifera. It is reflected by the formation of one chamber of the shell (or of a cycle of chamberlets).


''Remarks'': The use of this term in foraminiferology is contested, mainly by biologists. The Cambridge Dictionary of Biology (Walker P.M.B., ed., 1990) defines instar as "the form assumed by an insect during a particular (ontogenic) stadium" (such as pupa, imago etc.). Others have used the term for the period of existence of marine arthropods between moults (ecdysis). Transferred to foraminifera, the formal definition would mean the stages of growth commonly designated as embryonic, nepionic or ephebic, each characterized by the addition of several or numerous chambers. However, because in foraminifera each growth-step modifyes the form of the shell and can be individually identified in every specimen by counting the number of chambers, I see no reason to reject the already traditional and most convenient use of this term as substitute for growth-step. Thus, an instar of a lamellar foraminifer includes whatever the shell produces by the same growth-step, i.e. the walls of the a chamber or of a chamberlet cycle and the respective outer lamella that covers all the exposed surfaces of the previous shell and participates in the construction of surficial ornements including piles, umbilical plugs and umbos. See also: [[supplemental skeleton]], where the distinction of successive growth-steps is difficult.

==See also==
*[[chamber]]
*[[chamberlet cycles]]
*[[lamellation]] 
*[[supplemental skeleton]]

==References==
Hottinger (2006), [http://paleopolis.rediris.es/cg/CG2006_M02/index.html Illustrated glossary of terms used in foraminiferal research]. [http://paleopolis.rediris.es/cg/uk-index.html Carnets de Géologie], [http://paleopolis.rediris.es/cg/CG2006_M02/index.html Memoir 2], ISSN 1634-0744                                                              
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