Editing Spermatozoon

{{short description|Motile sperm cell}}
{{Infobox cell
| Name        = Spermatozoon
| Latin       = spermatozoon
| Greek      = σπερματοζωάριο
| Image       = Sperm-egg.jpg
| Caption     = Motile sperm cell attempting to penetrate an [[ovum]]'s [[Zona pellucida|coating]] to [[Fertilisation|fertilize]] it.
| Width       = 300
| Image2      = Complete diagram of a human spermatozoa en.svg
| Caption2    = Diagram of a human spermatozoon
| Precursor   =
| System      =
| Artery      =
| Vein        =
| Nerve       =
| Lymph       =
}}

A '''spermatozoon''' ({{IPAc-en|s|p|ər|ˌ|m|æ|t|ə|ˈ|z|oʊ|.|ən|,_|ˌ|s|p|ɜr|m|ə|t|ə|-}};<ref>{{cite Dictionary.com|spermatozoon}}</ref> also spelled '''spermatozoön'''; {{plural form}}: '''spermatozoa'''; {{etymology|grc|''{{wikt-lang|grc|σπέρμα}}'' ({{grc-transl|σπέρμα}})|seed||''{{wikt-lang|grc|ζῷον}}'' ({{grc-transl|ζῷον}})|animal}}) is a [[motile]] [[sperm]] [[cell (biology)|cell]] produced by [[male]] [[animal]]s relying on [[internal fertilization]]. A spermatozoon is a moving form of the [[ploidy|haploid]] [[cell (biology)|cell]] that is the male [[gamete]] that [[Fertilization|joins with]] an [[ovum]] to form a [[zygote]]. (A zygote is a single cell, with a complete set of [[chromosome]]s, that normally develops into an [[embryo]].)

Sperm cells contribute approximately half of the nuclear [[gene|genetic information]] to the [[diploid]] offspring (excluding, in most cases, [[mitochondrial DNA]]). In mammals, the [[sex]] of the offspring is determined by the sperm cell: a spermatozoon bearing an [[X chromosome]] will lead to a [[female]] (XX) offspring, while one bearing a [[Y chromosome]] will lead to a [[male]] (XY) offspring. Sperm cells were first observed in [[Antonie van Leeuwenhoek]]'s laboratory in 1677.<ref>{{cite news|url=http://www.cbc.ca/news2/background/genetics_reproduction/timeline.html|title=Timeline: Assisted reproduction and birth control|access-date=2006-04-06|work=CBC News|archive-date=2016-04-28|archive-url=https://web.archive.org/web/20160428142316/http://www.cbc.ca/news2/background/genetics_reproduction/timeline.html|url-status=live}}</ref>

[[File:Human sperm under microscope.webm|thumb|Human sperm under microscope]]

==Mammalian spermatozoa==

===Humans===
The [[sperm cell]] of ''Homo sapiens'' is the small [[Gamete|reproductive cell]] produced by males, and can only survive in warm environments; upon leaving the body, it starts to degrade, thereby decreasing the total [[sperm quality]]. Sperm cells normally come in two types, "female" and "male", named for the resulting sex of the fertilized zygote each produces after fusing with the ovum. Sperm cells that produce female ([[karyotype]] '''XX''') offspring carry an X-chromosome, while sperm cells that produce male ('''XY''') offspring carry a Y-chromosome.<ref>{{cite book |last1=Scheinfeld |first1=Amram |title=You and Heredity |date=1939 |publisher=Frederick A. Stokes Company |location=New York |pages=39}}</ref> Errors of meiosis may lead to the formation of sperm containing different arrangements of sex chromosomes, either altogether missing (''[[monosomy]]'', designated "'''0'''"), or in multiples (''[[trisomy]]''), such as "'''XX'''", "'''XY'''", etc... some of the conditions known as [[Disorders of sex development|Disorders of Sex Development]] (DSD) are the result of fertilization by such defective sperm.{{cn|date=April 2025}}

A human sperm cell consists of a flat, disc shaped '''head''' approximately {{convert|5.1|by|3.1|pitch|mil|abbr=in}}, and a '''tail''', known as a [[Flagellum#Eukaryotic|flagellum]] {{convert|50|pitch|mil|abbr=in}} long.<ref>{{cite journal |last1=Smith |first1=D. J. |last2=Gaffney |first2=E. A. |last3=Blake |first3=J. R. |last4=Kirkman-Brown |first4=J. C. |title=Human sperm accumulation near surfaces: a simulation study |journal=Journal of Fluid Mechanics |date=25 February 2009 |volume=621 |pages=289–320 |doi=10.1017/S0022112008004953 |bibcode=2009JFM...621..289S |s2cid=3942426 |url=http://pure-oai.bham.ac.uk/ws/files/17448418/Smith2009_S0022112008004953a.pdf |access-date=10 September 2021 |archive-date=27 January 2022 |archive-url=https://web.archive.org/web/20220127073249/http://pure-oai.bham.ac.uk/ws/files/17448418/Smith2009_S0022112008004953a.pdf |url-status=live }}</ref> The flagellum propels the sperm cell at about {{convert|1|to|3|mm/min|mil/s|abbr=off}}.<ref>{{cite journal | last1 = Ishijima | first1 = Sumio | last2 = Oshio | first2 = Shigeru | last3 = Mohri | first3 = Hideo | year = 1986 | title = ''Flagellar movement of human spermatozoa'' | journal = Gamete Research | volume = 13 | issue = 3| pages = 185–197 | doi = 10.1002/mrd.1120130302 }}</ref>  Sperm have an olfactory  [[Chemotaxis|guidance mechanism]], and after reaching the [[fallopian tube]]s, must undergo a period of [[capacitation]] before penetration of the ovum.<ref>{{cite journal |last1=Eisenbach |first1=Michael |last2=Giojalas |first2=Laura C. |title=Sperm guidance in mammals — an unpaved road to the egg |journal=Nature Reviews Molecular Cell Biology |date=April 2006 |volume=7 |issue=4 |pages=276–285 |doi=10.1038/nrm1893 |pmid=16607290 |hdl=11336/57585 |s2cid=32567894 |hdl-access=free }}</ref>

'''Head:''' It has a compact nucleus with only chromatic substance and is surrounded by only a thin rim of cytoplasm. Above the nucleus lies a cap-like structure called the [[acrosome]], formed by modification of the [[Golgi apparatus|Golgi body]], which secretes the enzyme '''spermlysin''' (''hyaluronidase, corona-penetrating enzyme, zona lysin,'' or ''acrosin''), that is necessary for fertilization. As the spermatozoon approaches the ovum, it undergoes the [[acrosome reaction]] in which the membrane surrounding the acrosome fuses with the plasma membrane of the sperm's head, exposing the contents of the acrosome.<ref>{{cite journal |last1=del Río |first1=María José |last2=Godoy |first2=Ana |last3=Toro |first3=Alejandra |last4=Orellana |first4=Renán |last5=Cortés |first5=Manuel E. |last6=Moreno |first6=Ricardo D. |last7=Vigil |first7=Pilar |title=La reacción acrosómica del espermatozoide: avances recientes |journal=Revista Internacional de Andrología |date=October 2007 |volume=5 |issue=4 |pages=368–373 |doi=10.1016/S1698-031X(07)74086-4 }}</ref>

'''Neck:''' It is the smallest part, {{convert|0.03|pitch|mil}} long, with a [[Anatomical terms of location|proximal]] [[centriole]] parallel to the base of the nucleus, perpendicular to the distal [[centriole]]. The proximal centriole is retained in the mature spermatozoon; the distal centriole disappears after [[axoneme]] assembly. The proximal centriole enters into the ovum, which has no centriole, and starts the first cleavage division of the zygote thus formed. The distal centriole gives rise to the axial filament which forms the tail and has a (9+2) arrangement. A transitory membrane called the ''Manchette'' lies in the '''midpiece'''.

'''Midpiece:''' It has 10–14 spirals of mitochondria surrounding the axial filament in the cytoplasm. It provides motility, and hence is called the powerhouse of the sperm.  It also has a ring centriole (annulus) that form a diffusion barrier between the midpiece and the principal piece and serve as a stabilizing structure for tail rigidity.<ref>{{Cite web|url=https://www.yeastgenome.org/go/GO:0097227|title=sperm annulus {{!}} SGD|website=www.yeastgenome.org|access-date=2019-02-22|archive-date=2019-02-22|archive-url=https://web.archive.org/web/20190222152105/https://www.yeastgenome.org/go/GO:0097227|url-status=live}}</ref>

'''Tail:''' The flagellum is the longest part at approximately {{convert|50|pitch|mm }}, having an axial filament surrounded by cytoplasm and plasma membrane, but at the posterior end the axial filament is naked. The flagellum gives movement to the cell.{{cn|date=April 2025}}

[[Semen]] has an alkaline nature and the spermatozoa do not reach full motility (hypermotility) until they reach the [[vagina]], where the alkaline pH is neutralized by acidic vaginal fluids.  This gradual process takes 20–30 minutes. During this period, [[fibrinogen]] from the [[seminal vesicle]]s forms a clot, securing and protecting the sperm. Just as they become hypermotile, [[fibrinolysin]] from the [[prostate gland]] dissolves the clot, allowing the sperm to progress optimally.{{cn|date=April 2025}}

The spermatozoon is characterized by a minimum of [[cytoplasm]] and the most densely packed DNA known in [[eukaryote]]s. Compared to [[mitosis|mitotic]] chromosomes in [[somatic cell]]s, sperm DNA is at least sixfold more highly condensed.<ref name="Ward">{{cite journal |vauthors=Ward WS, Coffey DS |title=DNA packaging and organization in mammalian spermatozoa: comparison with somatic cells |journal=Biology of Reproduction |volume=44 |issue=4 |pages=569–74 |year=1991 |pmid=2043729| doi = 10.1095/biolreprod44.4.569|doi-access=free }}</ref>

The specimen contributes with [[DNA]]/[[chromatin]], a [[centriole]], and perhaps also an [[oocyte]]-activating factor (OAF).<ref name=barroso>{{cite journal |last1=Barroso |first1=Gerardo |last2=Valdespin |first2=Carlos |last3=Vega |first3=Eva |last4=Kershenovich |first4=Ruben |last5=Avila |first5=Rosaura |last6=Avendaño |first6=Conrado |last7=Oehninger |first7=Sergio |title=Developmental sperm contributions: fertilization and beyond |journal=Fertility and Sterility |date=September 2009 |volume=92 |issue=3 |pages=835–848 |doi=10.1016/j.fertnstert.2009.06.030 |pmid=19631936 |doi-access=free }}</ref> It may also contribute with paternal [[messenger RNA]] (mRNA), also contributing to embryonic development.<ref name=barroso/>
<gallery>
File:Spermatozoa-human-3140x.jpg|Electron [[micrograph]] of human spermatozoa magnified 3140 times.
File:Sperms (urine) - Spermler (idrar) - 01.png|Sperm cells in the urine sample of a 45-year-old male patient who is being followed with the diagnosis of [[benign prostate hyperplasia]].
File:Sperm Head Dimensions.png|Dimensions of the human sperm head measured from a 39-year-old healthy subject.

</gallery> The human spermatozoon contains at least 7500 different [[protein]]s.<ref>{{cite journal |last1=Amaral |first1=Alexandra |last2=Castillo |first2=Judit |last3=Ramalho-Santos |first3=João |last4=Oliva |first4=Rafael |title=The combined human sperm proteome: cellular pathways and implications for basic and clinical science |journal=Human Reproduction Update |date=1 January 2014 |volume=20 |issue=1 |pages=40–62 |doi=10.1093/humupd/dmt046 |pmid=24082039 |doi-access=free }}</ref>

Human sperm genetics has been associated with [[human evolution]], per a 2020 study.<ref>{{cite journal |last1=Xia |first1=Bo |last2=Yan |first2=Yun |last3=Baron |first3=Maayan |last4=Wagner |first4=Florian |last5=Barkley |first5=Dalia |last6=Chiodin |first6=Marta |last7=Kim |first7=Sang Y. |last8=Keefe |first8=David L. |last9=Alukal |first9=Joseph P. |last10=Boeke |first10=Jef D. |last11=Yanai |first11=Itai |title=Widespread Transcriptional Scanning in the Testis Modulates Gene Evolution Rates |journal=Cell |date=January 2020 |volume=180 |issue=2 |pages=248–262.e21 |doi=10.1016/j.cell.2019.12.015 |pmid=31978344 |pmc=7891839 }}</ref><ref>{{Cite web|url=https://phys.org/news/2020-01-scanning-sperm-human-evolution.html|title=Scanning system in sperm may control rate of human evolution|access-date=2020-01-24|archive-date=2020-01-28|archive-url=https://web.archive.org/web/20200128111658/https://phys.org/news/2020-01-scanning-sperm-human-evolution.html|url-status=live}}</ref><ref>{{Cite web|url=https://markets.businessinsider.com/news/stocks/genetic-scanning-system-in-sperm-may-control-rate-of-human-evolution-1028840950|title=Genetic Scanning System in Sperm May Control Rate of Human Evolution|access-date=2020-01-24|archive-date=2020-08-11|archive-url=https://web.archive.org/web/20200811163131/https://markets.businessinsider.com/news/stocks/genetic-scanning-system-in-sperm-may-control-rate-of-human-evolution-1028840950|url-status=live}}</ref>

In humans, recombination rates differ between maternal and paternal DNA:
* '''Maternal DNA:''' Recombines approximately '''42 times''' on average.
* '''Paternal DNA:''' Recombines approximately '''27 times''' on average.

===DNA damage and repair===
DNA damages present in spermatozoa in the period after [[meiosis]] but before [[Human fertilization|fertilization]] may be repaired in the fertilized egg, but if not repaired, can have serious deleterious effects on fertility and the developing embryo.  Human spermatozoa are particularly vulnerable to free radical attack and the generation of oxidative DNA damage.<ref name="pmid26178844">{{cite book |doi=10.1007/978-3-319-18881-2_2 |pmid=26178844 |chapter=Damage to Sperm DNA Mediated by Reactive Oxygen Species: Its Impact on Human Reproduction and the Health Trajectory of Offspring |title=The Male Role in Pregnancy Loss and Embryo Implantation Failure |volume=868 |pages=23–47 |series=Advances in Experimental Medicine and Biology |year=2015 |last1=Gavriliouk |first1=Dan |last2=Aitken |first2=Robert John |isbn=978-3-319-18880-5 }}</ref><ref>{{cite journal | last1 = Lozano | first1 = G.M. | last2 = Bejarano | first2 = I. | last3 = Espino | first3 = J. | last4 = González | first4 = D. | last5 = Ortiz | first5 = A. | last6 = García | first6 = J.F. | last7 = Rodríguez | first7 = A.B. | last8 = Pariente | first8 = J.A. | year = 2009 | title = Density gradient capacitation is the most suitable method to improve fertilization and to reduce DNA fragmentation positive spermatozoa of infertile men | url = https://www.researchgate.net/publication/259983025 | journal = Anatolian Journal of Obstetrics & Gynecology | volume = 3 | issue = 1 | pages = 1–7 | access-date = 2016-03-08 | archive-date = 2022-04-30 | archive-url = https://web.archive.org/web/20220430005522/https://www.researchgate.net/publication/259983025_Density_gradient_capacitation_is_the_most_suitable_method_to_improve_fertilization_and_to_reduce_DNA_fragmentation_positive_spermatozoa_of_infertile_men | url-status = live }}</ref> (see e.g. [[8-Oxo-2'-deoxyguanosine]])

Exposure of males to certain lifestyle, environmental or occupational hazards may increase the risk of [[Aneuploidy|aneuploid]] spermatozoa.<ref>{{cite journal |vauthors=Templado C, Uroz L, Estop A |title=New insights on the origin and relevance of aneuploidy in human spermatozoa |journal=Molecular Human Reproduction|volume=19 |issue=10 |pages=634–43 |year=2013 |pmid=23720770 |doi=10.1093/molehr/gat039 |doi-access= }}</ref>  In particular, risk of aneuploidy is increased by tobacco smoking,<ref name="pmid11468778">{{cite journal |vauthors=Shi Q, Ko E, Barclay L, Hoang T, Rademaker A, Martin R |title=Cigarette smoking and aneuploidy in human sperm |journal=Molecular Reproduction and Development |volume=59 |issue=4 |pages=417–21 |year=2001 |pmid=11468778 |doi=10.1002/mrd.1048 |s2cid=35230655 }}</ref><ref name="pmid9797104">{{cite journal |vauthors=Rubes J, Lowe X, Moore D, Perreault S, Slott V, Evenson D, Selevan SG, Wyrobek AJ |title=Smoking cigarettes is associated with increased sperm disomy in teenage men |journal=Fertility and Sterility |volume=70 |issue=4 |pages=715–23 |year=1998 |pmid=9797104 |doi= 10.1016/S0015-0282(98)00261-1|doi-access=free }}</ref> and occupational exposure to benzene,<ref name="pmid20418200">{{cite journal |vauthors=Xing C, Marchetti F, Li G, Weldon RH, Kurtovich E, Young S, Schmid TE, Zhang L, Rappaport S, Waidyanatha S, Wyrobek AJ, Eskenazi B |title=Benzene exposure near the U.S. permissible limit is associated with sperm aneuploidy |journal=Environmental Health Perspectives |volume=118 |issue=6 |pages=833–9 |year=2010 |pmid=20418200 |pmc=2898861 |doi=10.1289/ehp.0901531 }}</ref> insecticides,<ref name="pmid15363581">{{cite journal |vauthors=Xia Y, Bian Q, Xu L, Cheng S, Song L, Liu J, Wu W, Wang S, Wang X |title=Genotoxic effects on human spermatozoa among pesticide factory workers exposed to fenvalerate |journal=Toxicology |volume=203 |issue=1–3 |pages=49–60 |year=2004 |pmid=15363581 |doi=10.1016/j.tox.2004.05.018 |bibcode=2004Toxgy.203...49X |s2cid=36073841 }}</ref><ref name="pmid15615886">{{cite journal |vauthors=Xia Y, Cheng S, Bian Q, Xu L, Collins MD, Chang HC, Song L, Liu J, Wang S, Wang X |title=Genotoxic effects on spermatozoa of carbaryl-exposed workers |journal=Toxicological Sciences |volume=85 |issue=1 |pages=615–23 |year=2005 |pmid=15615886 |doi=10.1093/toxsci/kfi066 |doi-access=free }}</ref> and perfluorinated compounds.<ref name="pmid25382683">{{cite journal |vauthors=Governini L, Guerranti C, De Leo V, Boschi L, Luddi A, Gori M, Orvieto R, Piomboni P |title=Chromosomal aneuploidies and DNA fragmentation of human spermatozoa from patients exposed to perfluorinated compounds |journal=Andrologia |volume= 47|issue= 9|pages= 1012–9|year=2014 |pmid=25382683 |doi=10.1111/and.12371 |hdl=11365/982323 |s2cid=13484513 |doi-access=free }}</ref>  Increased aneuploidy of spermatozoa often occurs in association with increased DNA damage. [[DNA fragmentation]] and increased in situ DNA susceptibility to denaturation, the features similar to these seen during [[apoptosis]] of somatic cells, characterize abnormal spermatozoa in cases of [[male infertility]].<ref>{{cite journal | last1 = Gorczyca | first1 = W | last2 = Traganos | first2 = F | last3 = Jesionowska | first3 = H | last4 = Darzynkiewicz | first4 = Z | year = 1993 | title = Presence of DNA strand breaks and increased sensitivity of DNA in situ to denaturation in abnormal human sperm cells. Analogy to apoptosis of somatic cells | journal = Exp Cell Res | volume = 207 | issue = 1| pages = 202–205 | doi = 10.1006/excr.1993.1182 | pmid = 8391465 }}</ref><ref>{{cite journal | last1 = Evenson | first1 = DP | last2 = Darzynkiewicz | first2 = Z | last3 = Melamed | first3 = MR | year = 1980 | title = Relation of mammalian sperm chromatin heterogeneity to fertility | journal = Science | volume = 210 | issue = 4474| pages = 1131–1133 | pmid = 7444440 | doi=10.1126/science.7444440| bibcode = 1980Sci...210.1131E }}</ref>

Although [[DNA repair]] has long been considered impossible in human spermatozoa due to the high level of DNA compaction in these cells, human spermatozoa possess a truncated [[base excision repair]] pathway that is mediated by [[oxoguanine glycosylase|8-oxoguanine DNA glycosylase 1 (OGG1)]].<ref name = Smith2013>{{cite journal |vauthors=Smith TB, Dun MD, Smith ND, Curry BJ, Connaughton HS, Aitken RJ |title=The presence of a truncated base excision repair pathway in human spermatozoa that is mediated by OGG1 |journal=J Cell Sci |volume=126 |issue=Pt 6 |pages=1488–97 |date=March 2013 |pmid=23378024 |doi=10.1242/jcs.121657 |url=}}</ref> Thus mature spermatozoa appear to have a limited capacity to mount a DNA repair response to [[oxidative stress]].<ref name = Smith2013/>

===Avoidance of immune system response===

[[Glycoprotein]] molecules on the surface of ejaculated sperm cells are recognized by all human female immune systems, and interpreted as a signal that the cell should not be rejected. The female immune system might otherwise attack sperm in the [[reproductive tract]]. The specific glycoproteins coating sperm cells are also utilized by some cancerous and bacterial cells, some parasitic worms, and HIV-infected white blood cells, thereby avoiding an immune response from the [[Host (biology)|host organism]].<ref>{{cite news|work=BBC News|url=http://news.bbc.co.uk/2/hi/health/7143889.stm|title=Sperm clue to 'disease immunity'|date=2007-12-17|access-date=2013-11-03|archive-date=2013-11-04|archive-url=https://web.archive.org/web/20131104200212/http://news.bbc.co.uk/2/hi/health/7143889.stm|url-status=live}}</ref>

The [[blood-testis barrier]], maintained by the tight junctions between the [[Sertoli cell]]s of the seminiferous tubules, prevents communication between the forming spermatozoa in the testis and the blood vessels (and immune cells circulating within them) within the [[Interstitial fluid|interstitial space]]. This prevents them from eliciting an immune response. The blood-testis barrier is also important in preventing toxic substances from disrupting spermatogenesis.{{citation needed|date=August 2023}}

==Spermatozoa in other organisms==
[[Image:Plant sperm.png|thumb|Motile sperm cells of algae and seedless plants.]]
{{see also|Sperm|Female sperm storage}}

===Animals===
Fertilization relies on spermatozoa for most sexually reproductive animals.

Some species of [[Drosophilidae|fruit fly]] produce the largest known spermatozoon found in nature.<ref name="Pitnick1995">{{cite journal|last1=Pitnick|first1=S|last2=Spicer|first2=GS|last3=Markow|first3=TA|author-link3=Therese Ann Markow|title=How long is a giant sperm?|journal=Nature|date=11 May 1995|volume=375|issue=6527|pages=109|doi=10.1038/375109a0|pmid=7753164|bibcode=1995Natur.375Q.109P|s2cid=4368953|doi-access=free}}</ref><ref>{{cite journal|last1=Pitnick|first1=S|last2=Markow|first2=TA|title=Large-male advantages associated with costs of sperm production in Drosophila hydei, a species with giant sperm.|journal=Proceedings of the National Academy of Sciences of the United States of America|date=27 September 1994|volume=91|issue=20|pages=9277–81|pmid=7937755|doi=10.1073/pnas.91.20.9277|pmc=44795|bibcode=1994PNAS...91.9277P|doi-access=free}}</ref>  ''[[Drosophila melanogaster]]'' produces sperm that can be up to 1.8&nbsp;mm,<ref>{{cite book|last1=Cooper|first1=K.W.|editor1-last=Demerec|editor1-first=M.|title=Biology of Drosophila|date=1950|publisher=Wiley|location=New York|pages=1–61}}</ref> while its relative ''[[Drosophila bifurca]]'' produces the largest known spermatozoon, measuring over 58&nbsp;mm in length.<ref name=Pitnick1995 /> In ''Drosophila melanogaster'', the entire sperm, tail included, gets incorporated into the [[oocyte]] [[cytoplasm]], however, for ''Drosophila bifurca'' only a small portion of the tail enters the oocyte.<ref>{{cite journal | last1 = Pitnick | first1 = S. | last2 = Spicer | first2 = G. S. | last3 = Markow | first3 = T. A. | year = 1995 | title = How long is a giant sperm | journal = Nature | volume = 375 | issue = 6527| page = 109 | doi = 10.1038/375109a0 | pmid=7753164| bibcode = 1995Natur.375Q.109P | s2cid = 4368953 | doi-access = free }}</ref>

The wood mouse ''[[Apodemus sylvaticus]]'' possesses spermatozoa with falciform morphology. Another characteristics which makes these gametocytes unique is the presence of an apical hook on the sperm head. This hook is used to attach to the hooks or to the flagella of other spermatozoa. Aggregation is caused by these attachments and mobile trains result. These trains provide improved motility in the female reproductive tract and are a means by which fertilization is promoted.<ref>{{cite journal | last1 = Moore | first1 = H | last2 = Dvoráková| first2 = K | last3 = Jenkins| first3 = N| last4 = Breed| first4 = W| year = 2002 | title = Exceptional sperm cooperation in Wood Mouse | url = http://eprints.whiterose.ac.uk/114/1/moorhd1.pdf| journal = Nature | volume = 418 | issue = 6894| pages = 174–177 | doi=10.1038/nature00832 | pmid=12110888| bibcode = 2002Natur.418..174M | s2cid = 4413444 }}</ref>

The postmeiotic phase of mouse spermatogenesis is very sensitive to environmental [[Genotoxicity|genotoxic]] agents, because as male germ cells form mature spermatozoa they progressively lose the ability to repair DNA damage.<ref name="pmid18282746">{{cite journal |vauthors=Marchetti F, Wyrobek AJ |title=DNA repair decline during mouse spermiogenesis results in the accumulation of heritable DNA damage |journal=DNA Repair |volume=7 |issue=4 |pages=572–81 |year=2008 |pmid=18282746 |doi=10.1016/j.dnarep.2007.12.011 |s2cid=1316244 |url=https://cloudfront.escholarship.org/dist/prd/content/qt7k61j39x/qt7k61j39x.pdf |access-date=2024-05-12 |archive-date=2018-07-25 |archive-url=https://web.archive.org/web/20180725012336/https://cloudfront.escholarship.org/dist/prd/content/qt7k61j39x/qt7k61j39x.pdf |url-status=live }}</ref>  Irradiation of male mice during late spermatogenesis can induce damage that persists for at least 7 days in the fertilizing spermatozoa, and disruption of maternal DNA double-strand break repair pathways increases spermatozoa-derived chromosomal aberrations.<ref name="pmid17978187">{{cite journal |vauthors=Marchetti F, Essers J, Kanaar R, Wyrobek AJ |title=Disruption of maternal DNA repair increases sperm-derived chromosomal aberrations |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=104 |issue=45 |pages=17725–9 |year=2007 |pmid=17978187 |pmc=2077046 |doi=10.1073/pnas.0705257104 |bibcode=2007PNAS..10417725M |doi-access=free }}</ref>  Treatment of male mice with [[melphalan]], a bifunctional [[alkylation|alkylating agent]] frequently employed in chemotherapy, induces DNA lesions during meiosis that may persist in an unrepaired state as germ cells progress through DNA repair-competent phases of spermatogenic development.<ref name="pmid25567288">{{cite journal |vauthors=Marchetti F, Bishop J, Gingerich J, Wyrobek AJ |title=Meiotic interstrand DNA damage escapes paternal repair and causes chromosomal aberrations in the zygote by maternal misrepair |journal=Scientific Reports |volume=5 |pages=7689 |year=2015 |pmid=25567288 |pmc=4286742 |doi=10.1038/srep07689 |bibcode=2015NatSR...5.7689M }}</ref>  Such unrepaired DNA damages in spermatozoa, after fertilization, can lead to offspring with various abnormalities.

[[Sea urchin]]s such as ''[[Arbacia punctulata]]'' are ideal organisms to use in sperm research, they spawn large numbers of sperm into the sea, making them well-suited as [[model organism]]s for experiments.<ref>{{cite journal |last1=Vacquier |first1=Victor D. |title=Laboratory on sea urchin fertilization |journal=Molecular Reproduction and Development |date=August 2011 |volume=78 |issue=8 |pages=553–564 |doi=10.1002/mrd.21360 |pmid=21805525 |doi-access= |s2cid=13452188 }}</ref>

The spermatozoa of [[marsupial]]s are usually longer than those of [[placental mammal]]s.<ref name="VogelnestPortas2019">{{cite book|author1=Larry Vogelnest|author2=Timothy Portas|title=Current Therapy in Medicine of Australian Mammals|url=https://books.google.com/books?id=4d6VDwAAQBAJ|date=1 May 2019|publisher=Csiro Publishing|isbn=978-1-4863-0752-4}}</ref>

===Plants, algae and fungi===
The [[gametophyte]]s of [[bryophyte]]s, [[fern]]s and some [[gymnosperm]]s produce motile [[sperm]] cells, contrary to [[pollen]] grains employed in most gymnosperms and all [[angiosperm]]s. This renders sexual reproduction in the absence of [[water]] impossible, since water is a necessary medium for sperm and egg to meet. Algae and lower plant sperm cells are often multi-flagellated (see image) and thus morphologically different from animal spermatozoa.<ref>{{Cite journal |last1=White-Cooper |first1=Helen |last2=Bausek |first2=Nina |date=2010-05-27 |title=Evolution and spermatogenesis |journal=Philosophical Transactions of the Royal Society B: Biological Sciences |language=en |volume=365 |issue=1546 |pages=1465–1480 |doi=10.1098/rstb.2009.0323 |issn=0962-8436 |pmc=2871925 |pmid=20403864}}</ref>

Some algae and fungi produce non-motile sperm cells, called spermatia. In higher plants and some algae and fungi, fertilization involves the migration of the sperm nucleus through a fertilization tube (e.g. [[pollen tube]] in higher plants) to reach the egg cell.{{citation needed|date=August 2023}}

==Spermatozoa production in mammals==
{{Unreferenced section|date=August 2022}}
{{Main|Spermatogenesis}}
Spermatozoa are produced in the [[seminiferous tubule]]s of the [[testicle]]s in a process called [[spermatogenesis]]. Round cells called [[spermatogonia]] divide and differentiate eventually to become spermatozoa. During [[copulation (zoology)|copulation]], the [[cloaca]] or [[vagina]] gets [[insemination|inseminated]], and then the spermatozoa move through [[chemotaxis]] to the ovum inside an [[oviduct]].

In [[assisted reproductive technology]], normozoospermia is referred to a total amount of >39 mill [[Ejaculation|ejaculated]], >32% with progressive motility and >4% normal morphology. Also, a normal ejaculation in humans must have a volume over 1.5 ml, being an excessive volume 6 ml per ejaculation ([[hyperspermia]]). An insufficient volume is called [[hypospermia]]. These problems are related to several complications in spermatozoa production, for example:
* Hyperspermia: usually provoked because of [[prostate]] inflammation.
* Hypospermia: an incomplete ejaculation, usually referred to an androgen deficit ([[Androgen deficiency|hypoandrogenism]]) or obstruction in some part of the [[ejaculatory duct]]. In laboratory conditions, is also due to a partial loss of the sample.
* [[Aspermia]]: there is no ejaculation. It could happen due to [[retrograde ejaculation]], anatomical or neurological diseases or anti-hypertensive drugs.

==Spermatozoa activation==
{{Unreferenced section|date=August 2022}}
{{main|Acrosome reaction}}
[[Image:Acrosome reaction diagram en.svg|thumb|440px|left|Acrosome reaction on a [[sea urchin]] cell]]
Approaching the egg cell is a rather complex, multistep process of [[chemotaxis]] guided by different chemical substances/stimuli on individual levels of phylogeny. One of the most significant, common signaling characters of the event is that a prototype of professional chemotaxis receptors, [[formyl peptide receptor]] (60,000 receptor/cell) as well as the activator ability of its ligand formyl Met-Leu-Phe have been demonstrated in the surface membrane even in the case of human sperms.<ref name=Gnessi1986>{{Cite journal |vauthors=Gnessi L, Fabbri A, Silvestroni L, Moretti C, Fraioli F, Pert CB, Isidori A | year = 1986 | title = Evidence for the presence of specific receptors for N-formyl chemotactic peptides on human spermatozoa.| journal = Journal of Clinical Endocrinology and Metabolism| volume = 63| pages = 841–6| pmid =3018025 |doi = 10.1210/jcem-63-4-841| issue = 4 }}</ref>
Mammalian sperm cells become even more active when they approach an egg cell in a process called '''sperm activation'''. Sperm activation has been shown to be caused by [[calcium]] [[ionophores]] ''[[in vitro]]'', [[progesterone]] released by nearby [[cumulus cell]]s and binding to [[ZP3]] of the [[zona pellucida]].  The cumulus cells are embedded in a gel-like substance made primarily of [[hyaluronic acid]], and developed in the ovary with the egg and support it as it grows.

The initial change is called "hyperactivation", which causes a change in spermatozoa motility. They swim faster and their tail movements become more forceful and erratic.

A recent discovery links hyperactivation to a sudden influx of calcium ion into the tails.  The whip-like tail (flagellum) of the sperm is studded with [[ion channel]]s formed by proteins called [[CatSper]].  These channels are selective, allowing only calcium ions to pass.  The opening of CatSper channels is responsible for the influx of calcium.  The sudden rise in calcium levels causes the flagellum to form deeper bends, propelling the sperm more forcefully through the viscous environment. Sperm hyperactivity is necessary for breaking through two physical barriers that protect the egg from fertilization.

The second process in sperm activation is the [[acrosome reaction]]. This involves releasing the contents of the acrosome, which disperse, and the exposure of enzymes attached to the inner acrosomal membrane of the sperm.  This occurs after the sperm first meets the egg.  This lock-and-key type mechanism is species-specific and prevents the sperm and egg of different species from fusing.  There is some evidence that this binding is what triggers the [[acrosome]] to release the enzymes that allow the sperm to fuse with the egg.

ZP3, one of the proteins that make up the zona pellucida, then binds to a partner molecule on the sperm.  Enzymes on the inner acrosomal membrane digest the zona pellucida.  After the sperm penetrates the zona pellucida, part of the sperm's cell membrane then [[fertilization|fuses]] with the egg cell's membrane, and the contents of the head diffuse into the egg.

Upon penetration, the oocyte is said to have become [[Ovum activation|activated]]. It undergoes its secondary meiotic division, and the two haploid nuclei (paternal and maternal) fuse to form a [[zygote]]. In order to prevent [[polyspermy]] and minimise the possibility of producing a [[Triploidy|triploid]] zygote, several changes to the egg's zona pellucida renders them impenetrable shortly after the first sperm enters the egg.

==Artificial storage==
Spermatozoa can be stored in diluents such as the ''Illini Variable Temperature'' (IVT) diluent, which have been reported to be able to preserve high fertility of spermatozoa for over seven days.<ref name=Watson1993>{{Cite journal | last1 = Watson | first1 = P. F. | title = The potential impact of sperm encapsulation technology on the importance of timing of artificial insemination: A perspective in the light of published work | journal = Reproduction, Fertility and Development | volume = 5 | issue = 6 | pages = 691–9 | year = 1993 | doi = 10.1071/RD9930691 | pmid=9627729}}</ref> The IVT diluent is composed of several salts, sugars and antibacterial agents and gassed with [[carbon dioxide|CO<sub>2</sub>]].<ref name=Watson1993/>

[[Semen cryopreservation]] can be used for far longer storage durations. For human spermatozoa, the longest reported successful storage with this method is 21 years.<ref>[http://www.planer.com/company/news/older-news-stories/335-child-born-after-21-year-semen-storage-using-planer-controlled-rate-freezer-.html Planer NEWS and Press Releases > Child born after 21 year semen storage using Planer controlled rate freezer] {{Webarchive|url=https://web.archive.org/web/20180303050335/https://www.planer.com/company/news/older-news-stories/335-child-born-after-21-year-semen-storage-using-planer-controlled-rate-freezer-.html |date=2018-03-03 }} 14/10/2004</ref>

== MMP and capacitation ==
{{Unreferenced section|date=June 2021}}
The [[capacitation]] is the final phase of spermatozoa development, when they acquire the capability to fertilize the oocyte. In vivo, it happens during ejaculation, when spermatozoa leave the vagina and come in the superior female reproductive tract. In vitro, it happens when the spermatozoa is washed and purified. Almost 30-40% of [[infertility]] is due to male factor, so several strategies have been created in order to recover the functional spermatozoa. The MMP (Million Motile Progressive cells per milliliter) measure is synonymous with [[capacitation]], and is very useful parameter to decide, along with a [[semen analysis|spermiogram]], the kind of treatment needed. it represents the ratio between the % of progressive motile sperm obtained in capacitated and the % of progressive motile sperm obtained in ejaculated. It is based on the recovery percentage. Depending on the percentage, we will decide the quality of the motile spermatozoa recovery: 15 to 25 million sperm/ml is considered optimal, between 5 and 15 million is considered enough and less than 5 million is considered sub-optimal or not sufficient. Regarding the values that we have obtained, along with the spermiogram results, different techniques will be displayed.

For example, if more than 1.0×10<sup>6</sup> progressive motile sperm per milliliter are found, it will be recommended to have sexual intercourse, and if that fails, the next step will be [[intrauterine insemination]] and later conventional [[in vitro fertilisation|in vitro fertilization]].

With less than 1.0×10<sup>6</sup> progressive motile sperm per milliliter, we will perform [[intracytoplasmic sperm injection]]. In case of azoospermia (no spermatozoa in the ejaculate), we will do a testicular biopsy in order to check if there are spermatozoa in the testes or if no spermatozoa are being produced.

== History ==
* In 1677 microbiologist [[Antonie van Leeuwenhoek]] discovered spermatozoa.{{cn|date=April 2025}}
* In 1841 the Swiss anatomist [[Albert von Kölliker]] wrote about spermatozoon in his work ''Untersuchungen über die Bedeutung der Samenfäden (Studies on the importance of spermatozoa).''{{cn|date=April 2025}}

==See also==
* [[Aneuploidy]]
* [[Non-disjunction]]

==References==
{{reflist}}

==External links==
{{commons category|Spermatozoa}}
* [http://news.bbc.co.uk/2/hi/health/4529152.stm Slower conception 'leads to boys']
* [https://www.youtube.com/watch?v=vvnEsOaKxuw&NR=1 Human Sperm Under a Microscope]

{{Sex (biology)}}
{{Male reproductive system}}

{{Authority control}}

[[Category:Germ cells]]
[[Category:Semen]]
[[Category:Human cells]]
[[Category:Fertility]]
[[Category:Men's health]]