View source for Egg-holder

[[File:Fig 30.jpg|thumb|<font size="2">'''Fig. 1.''' Chloroplasts of foraminiferal symbionts. Gulf of Aqaba. TEM graphs courtesy S. Reber-Leutenegger. 
'''A:''' Bacillarian (diatom) symbionts below lateral chamber wall, housed in eggholders, below pore mouths, of ''Amphistegina lobifera'' Larsen. x 5,000. '''B:''' dinophycean (dinoflagellate) symbiont of ''Amphisorus hemprichii'' Ehrenberg. Note sections of short flagellae (arrows) permitting active movement of the symbiont within the lacunar system of the host, to regulate its access to light. The nucleus with its (polyploid) chromosomes visible during the interphase unusual among eucaryotes but characteristic for dinophyceans. x 10,000. '''C:''' rhodophycean (red algal) symbiont of ''Peneroplis planatus'' (Fichtel et Moll). x 12,000. '''D:''' Bacillarian symbiont of ''Assilina ammonoides'' (Gronovius), ultrathin section oblique-tangential to the lateral surface of achamber. Note the loose stacking of the thylacoids in the chloroplast, a characteristic of symbionts of ''Assilina''. X 8,000. '''E:''' ''Elphidium craticulatum'' (Fichtel et Moll), ultrathin section through a protoplast of a chamber including one of its [[retral processes]] (double arrow), showing free chloroplasts in the host chamberplasm, a characteristic of [[symbiont husbandry]]. x 4,000. '''F:''' Rhodophycean symbionts of ''Peneroplis planatus'' (Fichtel et Moll) from Elba in the Mediterranean. Note starch grains covering the [[pyrenoid]] and filling most of the symbiont's mass. The starch grains may also appear as free grains in the host chamber plasm and represent seasonal food storage for the host. x 4,000.
'''bD:''' basal pore disc; '''cpl:''' chloroplast; '''flag:''' flagellum with its base; '''ilD:''' interlamellar disc of pore; '''m:''' mitochondrium; '''n:''' nucleus; '''OL:''' organic lining; '''p:''' pore; '''Pl:''' plasmalemma; '''ppl:''' pore plug; '''pyr:''' pyrenoid; '''spl:''' (mineralized) sieve plate; '''tyl:''' thylacoid; '''v:''' vacuoles; (Hottinger, 2006; fig. 30 [http://paleopolis.rediris.es/cg/CG2006_M02/index.html] '''CC'''/BY-NC-SA)]]

[[Image:Fig 40.jpg|thumb|right|300px| <font size="2">'''Fig. 2.''' Eggholders harbouring the symbionts in Heterostegina depressa d'Orbigny. Gulf of Aqaba. Recent. '''A:''' TEM micrograph of section perpendicular to lateral chamber wall; biomineralized wall dissolved, organic cell walls distinctly separated by the techniques of preparation. Courtesy S. Reber-Leutenegger. x 10,200. B-C: dried shell, split open in the equatorial plane. The internal surface of the lateral chamber wall bears eggholders. SEM graphs, x 5,000 and x 500. Drying strechted the organic cell walls.
'''Cl:''' chloroplast of bacillariophycean symbiont; '''clat:''' lateral intraseptal canal; '''egh:''' eggholder; '''M:''' [[mitochondria]]; '''OL:''' [[organic lining]] of host; '''Pl:''' plasmalemma of host; '''Plp:''' [[pore plug]] (see pore); '''Pls:''' plasmalemma of symbiont; '''Py:''' pyrenoid; '''s:''' [[septum]]; '''sl:''' [[septulum]]; '''st:''' [[stolon]] (Y-shaped); '''V:''' vacuole housing symbiont; '''Vm:''' vacuolar membrane; (Hottinger, 2006; fig. 40 [http://paleopolis.rediris.es/cg/CG2006_M02/index.html] '''CC'''/BY-NC-SA)]]
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==Definition==
*''according to Hottinger (2006):''
'''EGG-HOLDER''' -  internal pore mouth, enlarged to a cup with polygonal rims, with or without spinose projections at the junction with adjacent pores. Harbours symbionts in order to enhance the gas exchange of the symbiont with the ambient environment of the host.










==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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