Editing Chaetognatha (section)

==Reproduction and life cycle==
All species are [[hermaphroditic]], carrying both [[ovum|eggs]] and [[spermatozoon|sperm]].<ref name="Bone" /> Each animal possesses a pair of [[testis|testes]] within the tail, and a pair of [[ovary|ovaries]] in the posterior region of the main body cavity. Immature sperm are released from the testes to mature inside the cavity of the tail, and then swim through a short duct to a [[seminal vesicle]] where they are packaged into a [[spermatophore]].<ref name=IZ/>

During mating, each individual places a spermatophore onto the neck of its partner after rupture of the seminal vesicle. The sperm rapidly escape from the spermatophore and swim along the midline of the animal until they reach a pair of small pores just in front of the tail. These pores connect to the [[oviduct]]s, into which the developed eggs have already passed from the ovaries, and it is here that fertilisation takes place.<ref name=IZ/> The seminal receptacles and oviducts accumulate and store spermatozoa, to perform multiple fertilisation cycles.<ref name="Perez2021"/> Some [[benthic]] members of [[Spadellidae]] are known to have elaborate [[courtship ritual]]s before copulation,<ref name="Perez2021"/> for example ''[[Paraspadella gotoi]]''.<ref name="Ball2006"/>

The eggs are mostly planktonic, except in a few species such as ''[[Ferosagitta hispida]]'' that attaches eggs to the substrate.<ref name="Perez2021"/> In ''[[Eukrohnia]]'', eggs develop in marsupial sacs or attached to [[alga]]e.<ref>{{Cite journal|last1=Terazaki|first1=M.|last2=Miller|first2=C. B.|date=1982-11-01|title=Reproduction of meso- and bathypelagic chaetognaths in the genus Eukrohnia|journal=Marine Biology|language=en|volume=71|issue=2|pages=193–196|doi=10.1007/BF00394629|bibcode=1982MarBi..71..193T |s2cid=84519862|issn=1432-1793}}</ref> Eggs usually hatch after 1–3 days. Chaetognaths do not undergo [[metamorphosis]] nor they possess a well-defined [[larva]]l stage,<ref name=IZ/><ref name="Perez2021"/> an unusual trait among marine invertebrates;<ref name="Ball2006"/> however there are significant morphological differences between the newborn and the adult, with respect to proportions, chitinous structures and fin development.<ref name="Perez2021"/><ref name="Daponte2004"/> 

The life spans of chaetognaths are variable but short; the longest recorded was 15 months in ''[[Sagitta friderici]]''.<ref name="Daponte2004">{{cite journal |doi=10.1016/j.icesjms.2004.03.006 |title=Sagitta friderici Ritter-Záhony (Chaetognatha) from South Atlantic waters: Abundance, population structure, and life cycle |date=2004 |last1=Daponte |first1=M.C |last2=Capitanio |first2=F.L |last3=Nahabedian |first3=D.E |last4=Viñas |first4=M.D |last5=Negri |first5=R.M |journal=ICES Journal of Marine Science |volume=61 |issue=4 |pages=680–686 |doi-access=free |bibcode=2004ICJMS..61..680D }}</ref>