Editing Chaetognatha (section)

== Infection by giant viruses ==
[[File:Comparison of the size of giant viruses to a common virus (HIV) and bacteria (E. coli).tif|thumb|Comparison of size between various viruses and the bacteria ''E. coli'' ]]
In 2018, reanalysis of electron microscopy photographs from the 1980s allowed scientists to identify a [[giant virus]] (''Meelsvirus'') infecting ''Adhesisagitta hispida''; its site of multiplication is nuclear and the virions (length: 1.25 μm) are enveloped.<ref>{{cite journal | vauthors = Shinn GL, Bullard BL | title = Ultrastructure of Meelsvirus: A nuclear virus of arrow worms (phylum Chaetognatha) producing giant "tailed" virions | journal = PLOS ONE | volume = 13 | issue = 9 | pages = e0203282 | date = 2018-09-19 | pmid = 30231047 | pmc = 6145532 | doi = 10.1371/journal.pone.0203282 | editor-first = Carmen | editor-last = San Martin | bibcode = 2018PLoSO..1303282S | doi-access = free }}</ref> In 2019, reanalysis of other previous studies has shown that structures that were taken in 1967 for bristles present on the surface of the species ''[[Spadella]] cephaloptera'',<ref>{{cite journal| vauthors = Horridge GA, Boulton PS |date=1967-11-14|title=Prey detection by Chaetognatha via a vibration sense|journal= Proceedings of the Royal Society of London. Series B. Biological Sciences|volume=168|issue=1013|pages=413–419|doi=10.1098/rspb.1967.0072|bibcode=1967RSPSB.168..413H|s2cid=86422882}}</ref> and in 2003, for bacteria infecting ''[[Paraspadella]] gotoi'',<ref>{{cite journal | vauthors = Casanova JP, Duvert M, Goto T | title = Ultrastructural study and ontogenesis of the appendages and related musculature of Paraspadella (Chaetognatha) | journal = Tissue & Cell | volume = 35 | issue = 5 | pages = 339–51 | date = October 2003 | pmid = 14517101 | doi = 10.1016/S0040-8166(03)00055-7 }}</ref> were in fact enveloped and spindle-shaped giant viruses with a cytoplasmic site of multiplication.<ref name="Barthélémy2019">Roxane-Marie Barthélémy, Eric Faure, Taichiro Goto: [https://www.semanticscholar.org/paper/Serendipitous-Discovery-in-a-Marine-Invertebrate-of-Barth%C3%A9l%C3%A9my-Faure/84c0a5481ea8fab48329ac6d28e81a091c59164a ''Serendipitous Discovery in a Marine Invertebrate (Phylum Chaetognatha) of the Longest Giant Viruses Reported till Date''.] In: ''Biology'', 2019, [https://www.hilarispublisher.com/abstract/serendipitous-discovery-in-a-marine-invertebrate-phylum-chaetognatha-of-the-longest-giant-viruses-reported-to-date-24968.html Abstract]</ref> The viral species infecting ''P. gotoi'', whose maximum length is 3.1 μm, has been named ''[[Klothovirus casanovai]]'' (''[[Clotho|Klotho]]'' being the Greek name for one of the three Fates whose attribute was a spindle, and ''casanovai'', in tribute to Pr J.-P. Casanova who devoted a large part of his scientific life to the study of chaetognaths). The other species has been named ''[[Megaklothovirus horridgei]]'' (in tribute to [[Adrian Horridge]], the first author of the 1967 article). On a photograph, one of the viruses ''M. horridgei'', although truncated, is 3.9 μm long, corresponding to about twice the length of the bacteria ''[[Escherichia coli]]''. Many [[Ribosome|ribosomes]] are present in virions but their origin remains unknown (cellular, viral or only partly viral). To date, giant viruses known to infect [[metazoans]] are exceptionally rare.