Editing Foraminifera (section)

== Reproduction ==
The generalized foraminiferal life-cycle involves an alternation between [[Ploidy#Haploid and monoploid|haploid]] and [[Ploidy|diploid]] generations, although they are mostly similar in form.<ref name="Treatise" /><ref name="M,L &F">{{cite book|last1=Moore|first1=R.C.|title=Invertebrate Fossils|last2=Lalicker|first2=A.G.|last3=Fischer|first3=C.G.|publisher=McGraw-Hill|year=1952|chapter=Ch 2 Foraminifera and Radiolaria|oclc=547380}}</ref> The haploid or gamont initially has a single [[cell nucleus|nucleus]], and divides to produce numerous [[gamete]]s, which typically have two [[flagellum|flagella]].  The diploid or agamont is [[multinucleate]], and after [[meiosis]] divides to produce new gamonts.  Multiple rounds of [[asexual reproduction]] between sexual generations are not uncommon in benthic forms.<ref name="Sen_Gupta83" />
[[File:Foraminifera life cycle.png|thumb|379x379px|Diagram of a typical foraminiferan life cycle, showing characteristic alternation of generations.]]
Foraminifera exhibit morphological dimorphism associated with their reproductive cycle. The gamont, or sexually reproducing haploid form, is ''megalospheric''—that is, its ''proloculus'', or first chamber, is proportionally large. The gamont is also known as the ''A'' form. Gamonts, despite having typically larger proloculi, also generally have smaller overall test diameter than do agamonts.

After reaching maturity, the gamont divides via [[mitosis]] to produce thousands of gametes which are also haploid. These gametes all have a full set of [[organelle]]s, and are expelled from the test into the environment leaving the test undamaged. Gametes are not differentiated into [[sperm]] and [[Egg cell|egg]], and any two gametes from a species can generally fertilize each other.
[[File:Megalosphere and Microsphere.png|left|thumb|Morphs present in the foram life cycle—the megalosphere and the microsphere. The name derives from the size of the proloculus, or first chamber, and as such the microsphere has a larger overall size.]]
When two gametes combine, they create a diploid, multi-nucleated cell known as the ''agamont,'' or ''B'' form. In contrast to the gamont, the agamont is ''microspheric'', with a proportionally small first chamber but typically larger overall diameter with more chambers. The agamont is the [[asexual reproduction]] phase of the foraminifera; upon reaching adulthood, the protoplasm entirely vacates the test and divides its [[cytoplasm]] [[Meiosis|meiotically]] via [[multiple fission]] to form a number of haploid offspring. These offspring then begin to form their megalospheric first chamber before dispersing.

In some cases the haploid young may mature into a megalospheric form which then reproduces asexually to produce another megalospheric, haploid offspring. In this case, the first megalospheric form is referred to as the ''schizont'' or ''A<sub>1</sub>'' form, while the second is referred to as the gamont or ''A<sub>2</sub>'' form.

[[File:Nummulitids.jpg|thumb|Fossil [[Nummulite|nummulitid]] foraminiferans showing microspheric (larger) and megalospheric individuals (smaller); [[Eocene]] of the United Arab Emirates; scale in mm|alt=]]

Maturation and reproduction occur more slowly in cooler and deeper water; these conditions also cause forams to grow larger. ''A'' forms always seem to be much more numerous than are ''B'' forms, likely due to the reduced likelihood of two gametes encountering one another and successfully combining.<ref name=Haynes1981 /><ref name=Saraswati2016 />

=== Variations in reproductive mode ===
There is a high degree of diversity in reproductive strategies in different foraminiferal groups.

In [[Monothalamea|unilocular species]], the ''A'' form and ''B'' form are still present. As in the microspheric morph of multilocular forams, the asexually reproducing ''B'' form is larger than the sexually reproducing ''A'' form.

Forams in the family [[Spirillinidae]] have amoeboid gametes rather than flagellated. Other aspects of reproduction in this group are generally similar to that of other groups of forams.

The calcareous [[Spirillinida|spirillinid]] ''[[Patellina|Patellina corrugata]]'' has a slightly different reproductive strategy than most other foraminifera. The asexually reproducing ''B'' form produces a cyst that surrounds the entire cell; it then divides within this cyst and the juvenile cells cannibalise the calcite of the parent's test to form the first chamber of their own test. These ''A'' forms, upon maturity, gather into groups of up to nine individuals; they then form a protective cyst around the whole group. [[Gametogenesis]] occurs within this cyst, producing very low numbers of gametes.  The ''B'' form larvae are produced inside of the cyst; any nuclei that are not bound into cells are consumed as food for the developing larvae. ''Patellina'' in ''A'' form is reportedly [[dioecious]], with sexes referred to as the "plus" and "minus"; these sexes differ in number of nuclei, with the "plus" form having three nuclei and the "minus" form having four nuclei. The ''B'' form is again larger than the ''A'' form.<ref name=Saraswati2016 /><ref name=Haynes1981>{{Cite book|last=Haynes|first=J. R.|url=https://books.google.com/books?id=y5ewCwAAQBAJ&q=foraminifera+john+r+haynes&pg=PP7|title=Foraminifera|date=1981-06-18|publisher=Springer|isbn=978-1-349-05397-1|language=en}}</ref><ref name="Goldstein 2003 37–55" />