{{Short description|Species of fly}} {{about|the insect|the Belgica Antarctic Expedition|Belgian Antarctic Expedition}} {{Speciesbox | image = Belgica antarctica mating.jpg | image_caption = Two ''Belgica antarctica'' adults | taxon = Belgica antarctica | authority = Jacobs, 1900<ref name="Jacobs, 1900" /> | range_map = BelgicaAntarcticaDist.png | range_map_caption = Distribution in Antarctica (red) }}
'''''Belgica antarctica''''', the '''Antarctic midge''', is a species of flightless midge, endemic to the continent of Antarctica. At a length of {{cvt|2|-|6|mm|sigfig=1}}, it is the largest purely terrestrial animal native to the continent.<ref name="UsherEdwards1984">{{cite journal |last=Usher |first=Michael B. |author2=Edwards, Marion |year=1984 |title=A dipteran from south of the Antarctic Circle: Belgica antarctica (Chironomidae) with a description of its larva |journal=Biological Journal of the Linnean Society |volume=23 |issue=1 |pages=19–31 |doi=10.1111/j.1095-8312.1984.tb00803.x}}</ref><ref name="MU">{{cite web |author=Luke Sandro & Juanita Constible |title=Antarctic Bestiary — Terrestrial Animals |url=http://www.units.muohio.edu/cryolab/education/antarcticbestiary_terrestrial.htm#Belgica |url-status=live |archive-url=https://web.archive.org/web/20081223183815/http://www.units.muohio.edu/cryolab/education/antarcticbestiary_terrestrial.htm |archive-date=23 December 2008 |access-date=December 9, 2008 |publisher=Laboratory for Ecophysiological Cryobiology, Miami University}}</ref><ref name=":0" /> It also has the smallest known insect genome as of 2014, with only 99 million base pairs (Mbp) of nucleotides and about 13,500 genes. It is the only insect that can survive year-round in Antarctica.
==Taxonomy and etymology== The first specimens of ''Belgica antarctica'' were collected on the Belgian Antarctic Expedition (1897–1899).<ref name=":0">{{Cite journal |author1=Iryna Kozeretska |author2=Svitlana Serga |author3=Pavlo Kovalenko |author4=Volodymyr Gorobchyshyn |author5=Peter Convey |doi=10.1111/1744-7917.12925 |issn=1672-9609 |issue=1 |journal=Insect Science |language=en |pages=2-20 |date=28 April 2021 |title=''Belgica antarctica'' (Diptera: Chironomidae): A natural model organism for extreme environments |volume=29}}</ref> During this expedition organized by the Belgian Government, Romanian biologist Emil Racoviță collected, among other specimens, a flightless midge and its larvae.<ref name=":0" /> Based on these specimens, the Belgian doctor and entomologist, Jean-Charles Jacobs, described ''Belgica antarctica'' Jacobs, 1900.<ref name=":1">{{Cite journal |author1=J.C. Jacobs |issn=0774-5915 |journal=Annales de la Société entomologique de Belgique |language=fr |page=107– 108 |date=1900 |title=Diagnoses d'insectes recueillis par l'expedition antarctique Beige (parte Chironomidae) |url=https://www.biodiversitylibrary.org/page/35620474 |volume=44}}</ref> Jacobs named the new genus and species of insect after the location where it was collected off the Antarctic Peninsula, "''canal de la Belgica antarctica''" (Belgian Strait)<ref name=":1" /> (now called Gerlache Strait), which in turn was named after the expedition's steam-yacht, ''SY Belgica.''<ref>{{Cite journal |author1=Patrick De Deckker |doi=10.1080/17518369.2018.1474695 |issn=0800-0395 |issue=1 |journal=Polar Research |language=en |article-number=1474695 |date=January 2018 |title=On the long-ignored scientific achievements of the Belgica expedition 1897–1899 |url=https://polarresearch.net/index.php/polar/article/view/2680/6111 |volume=37|hdl=1885/157188 |hdl-access=free }}</ref>
==Tolerance to extreme conditions== ===Freezing temperatures===
The flightlessness of ''B. antarctica'' may be an adaptation to prevent wind from blowing it into inhospitable areas.<ref name="MU" /> It can survive freezing, but although local air temperatures may reach as low as −40 °C, this insect cannot survive temperatures below −15 °C. This is comparatively milder than other cold-adapted insects. The reason for this relatively low freezing tolerance is due to thermal buffering: just burrowing at a depth of 1 cm, temperature is stable between 0 and −2 °C for 10 months out of 12, and it seldom goes lower than −7 °C all year round. Ice and snow cover also helps keep the temperature stable.<ref name="LeeJr2006">{{Cite journal | last1 = Lee | first1 = R. E. | last2 = Elnitsky | first2 = M. A. | last3 = Rinehart | first3 = J. P. | last4 = Hayward | first4 = S. A. | last5 = Sandro | first5 = L. H. | last6 = Denlinger | first6 = D. L. | title = Rapid cold-hardening increases the freezing tolerance of the Antarctic midge ''Belgica antarctica''| doi = 10.1242/jeb.02001 | journal = Journal of Experimental Biology | volume = 209 | issue = 3 | pages = 399–406 | year = 2006 | pmid = 16424090 | doi-access = free}}</ref> Freezing tolerance is enhanced by cold hardening.<ref name="LeeJr2006" />
To adapt to the cold temperatures, ''B. antarctica'' accumulates trehalose, glucose, and erythritol. These compounds help the insect survive freezing by reducing the amount of ice that forms within the body. They also stabilize proteins and membranes, binding to them by means of hydrogen bonds. Heat shock proteins also help the tolerance to both high and low temperatures.<ref name="Michaud2008">{{Cite journal | last1 = Robert Michaud | first1 = M. | last2 = Benoit | first2 = J. B. | last3 = Lopez-Martinez | first3 = G. | last4 = Elnitsky | first4 = M. A. | last5 = Lee | first5 = R. E. | last6 = Denlinger | first6 = D. L. | doi = 10.1016/j.jinsphys.2008.01.003 | title = Metabolomics reveals unique and shared metabolic changes in response to heat shock, freezing and desiccation in the Antarctic midge, Belgica antarctica | journal = Journal of Insect Physiology | volume = 54 | issue = 4 | pages = 645–655 | year = 2008 | pmid = 18313070}}</ref>
''Belgica antarctica'' not only tolerates, but also requires a freezing climate to survive: exposure of larvae to such mild temperatures as 10 °C is enough to kill them within a week.<ref name="LeeJr2006"/> Exposure to temperatures of 30 °C kills individuals in a few hours.<ref name="Michaud2008"/> It can, however, resist partial desiccation, surviving the loss of up to 70% of body water.<ref name="Michaud2008"/> In examples of first instar larvae evolving into fourth instar larvae, the conditions were incredibly limited, only occurring at 4 °C.<ref>{{Cite journal |last=Yoshida |first=Mizuki |date=June 19, 2024 |title=Thermal responses of the embryos and early instar larvae of the Antarctic midge Belgica antarctica (Insect: Diptera) |url=https://link.springer.com/article/10.1007/s00300-023-03142-8 |journal=Osaka Metropolitan University |via=Springer Nature Link}}</ref>
===Dehydration===
Not only can this insect survive in freezing temperatures, but their larvae are incredibly adapted to dehydration in the west coast of Antarctica.<ref>{{Cite journal |last=Benoit |first=Joshua B. |date=January 26, 2007 |title=Mechanisms to reduce dehydration stress in larvae of the Antarctic midge, Belgica antarctica |url=https://www.sciencedirect.com/science/article/abs/pii/S0022191007001102?fr=RR-2&ref=pdf_download&rr=91fbbc6f5f100f75 |journal=Journal of Insect Physiology |volume=53 |issue=2007 |pages=656-667 |via=Elsevier Science Direct}}</ref> Living without water through the duration of their larval cycle, ''B. antarctica'' have been recorded to slow the dehydration process by doubling their concentration of glycerol, which assists in the cold-hardening process as well. Like other insects, ''B. antarctica'' larvae have been shown to cluster to preserve water in their populations.
==Lifecycle== left|thumb|''Belgica antarctica'' on a moss in Antarctica. ''B. antarctica'' spends most of its two-year lifecycle in four larval stages. Research finds that it uses a unique dual dormancy strategy during its development.<ref>{{Cite journal |last=Yoshida |first=Mizuki |last2=Convey |first2=Peter |last3=Hayward |first3=Scott A. L. |last4=Lee |first4=Richard E. |last5=Denlinger |first5=David L. |last6=Teets |first6=Nicholas M. |last7=Goto |first7=Shin G. |date=2025 |title=Obligate diapause and its termination shape the life-cycle seasonality of an Antarctic insect |url=https://www.nature.com/articles/s41598-025-86617-4 |journal=Scientific Reports |language=en |volume=15 |issue=1 |doi=10.1038/s41598-025-86617-4 |issn=2045-2322|pmc=11822100 }}</ref> In the first winter, larvae typically reach their second instar and undergo quiescence - a form of dormancy that allows them to quickly resume development when conditions improve. As they approach their second winter in the fourth (final) instar, the larvae enter obligate diapause, a programmed dormant period that ensures synchronized adult emergence during summer.
Overwintering may occur in any instar. Terrestrial algae (particularly ''Prasiola crispa''), fungi, decaying vegetation, organic detritus, and microorganisms provide the food for the larval stage. The adults, which are aphagous (non-feeding), emerge in the spring and summer and live no more than 10 days; females mate in their first day of life and a few days later release their only batch of eggs (semelparity), as the process damages their abdomens. Males on the other hand, are able to mate more than once. The female secretes a jelly on the eggs that acts as a blanket of antifreeze, stops them from dehydrating, and acts as a food source once they hatch. Mating occurs in large groups of males, analogous to swarms of winged midges.<ref name=":0" /><ref name="LeeJr2006" />
==Genome== As of 2014, ''B. antarctica'' has the smallest insect genome known, at 99 Mbp of nucleotides and 13 500 genes.<ref>{{cite news |date=2014-08-12 |title=Antarctic midge has smallest insect genome |work=BBC |url=https://www.bbc.co.uk/nature/28525963 |access-date=2014-08-12 |archive-url=https://web.archive.org/web/20140812223520/https://www.bbc.co.uk/nature/28525963 |archive-date=2014-08-12}}</ref> Although the total amount of coding DNA is similar to that of other Diptera (19 Mbp), its fraction is much higher due to the extreme reduction in some types of non-coding DNA. Intron size has been reduced, while transposable elements are almost absent.<ref name="KelleyPeyton2014">{{cite journal |last1=Kelley |first1=Joanna L. |last2=Peyton |first2=Justin T. |last3=Fiston-Lavier |first3=Anna-Sophie |last4=Teets |first4=Nicholas M. |last5=Yee |first5=Muh-Ching |last6=Johnston |first6=J. Spencer |last7=Bustamante |first7=Carlos D. |last8=Lee |first8=Richard E. |last9=Denlinger |first9=David L. |year=2014 |title=Compact genome of the Antarctic midge is likely an adaptation to an extreme environment |journal=Nature Communications |volume=5 |page=4611 |bibcode=2014NatCo...5.4611K |doi=10.1038/ncomms5611 |issn=2041-1723 |pmc=4164542 |pmid=25118180}}</ref>
{| class="wikitable" |+ Comparison of insect genomes |- ! Species !! Genome size !! Coding DNA (genome percentage) !! Transposable element percentage |- | ''Belgica antarctica'' ||style=text-align:right| 99 Mbp ||style=text-align:right| 19 Mbp (19.4%) ||style=text-align:right| 0.12% |- | ''Aedes aegypti''||style=text-align:right| 1380 Mbp||style=text-align:right| 22 Mbp (1.6%) ||style=text-align:right| 47% |- | ''Drosophila melanogaster'' ||style=text-align:right| 180 Mbp||style=text-align:right| 22.8 Mbp (13.6%) ||style=text-align:right| 20% |}
==See also== * ''Gynaephora groenlandica'', a species of Arctic moth whose larvae can survive temperatures below −60 °C * Belgian Antarctic Expedition
==References== {{Reflist|refs=
<ref name="Jacobs, 1900">{{cite journal|last1=Jacobs|first1=[J.-Ch.]|title=Diagnoses d'insectes recueillis par l'expédition antarctique Belge: Diptères|journal=Annales de la Société entomologique de Belgique|date=1900|volume=44|pages=106–107|url=https://www.biodiversitylibrary.org/page/35620473}}</ref>
}}
==Further reading==
* {{cite book|last1=Rübsaamen|first1=Ew. H.|title=Zoologie: Insectes|date=1906|publisher=J.-E. Buschmann|location=Anvers |url=https://www.biodiversitylibrary.org/page/2115037|chapter=Chironomidæ|at=pp. 77–83; [https://www.biodiversitylibrary.org/page/2115007 Pl. 4], Figs. 2, 4–7; [https://www.biodiversitylibrary.org/page/2115003 Pl. V], Figs. 9–19|series=Résultats du voyage du S.Y. Belgica en 1897-1898-1899}} * {{cite journal|last1=Keilin|first1=D.|title=Sur l'anatomie et le développement de ''Belgica antarctica'' Jacobs, Chironomide antarctique à ailes réduites|journal=Comptes rendus hebdomadaires des séances de l'Académie des Sciences|date=1912|volume=154|url=http://gallica.bnf.fr/ark:/12148/bpt6k31070/f765.image|id={{BHL page|7167537}}}} * {{cite journal|last1=Convey|first1=Peter|last2=Block|first2=William|title=Antarctic Diptera: Ecology, physiology and distribution|journal=European Journal of Entomology|date=1996|volume=93|pages=1–13|url=https://www.eje.cz/artkey/eje-199601-0001_Antarctic_diptera_Ecology_physiology_and_distribution.php}} * {{cite journal|last1=Elnitsky|first1=M. A.|last2=Hayward|first2=S. A. L.|last3=Rinehart|first3=J. P.|last4=Denlinger|first4=D. L.|last5=Lee|first5=R. E.|title=Cryoprotective dehydration and the resistance to inoculative freezing in the Antarctic midge, ''Belgica antarctica''|journal=Journal of Experimental Biology|date=2008|volume=211|issue=4|pages=524–530|doi=10.1242/jeb.011874|pmid=18245628|doi-access=free}} * {{cite journal|last1=Lopez-Martinez|first1=Giancarlo|last2=Benoit|first2=Joshua B.|last3=Rinehart|first3=Joseph P.|last4=Elnitsky|first4=Michael A.|last5=Lee|first5=Richard E.|last6=Denlinger|first6=David L.|title=Dehydration, rehydration, and overhydration alter patterns of gene expression in the Antarctic midge, ''Belgica antarctica''|journal=Journal of Comparative Physiology B|date=2009|volume=179|issue=4|pages=481–491|doi=10.1007/s00360-008-0334-0|pmid=19125254|s2cid=1732347|url=https://www.researchgate.net/publication/225731972}}
==External links== * ''Belgica antarctica'' discussed on RNZ ''Critter of the Week'', [https://www.rnz.co.nz/national/programmes/afternoons/collections/critter-of-the-week/audio/2018895630/critter-of-the-week-antarctic-midge 23 June 2023] * {{cite web|url=https://www.units.miamioh.edu/cryolab/education/antarcticbestiary_terrestrial.htm|title=Antarctic Bestiary|website=Miami University|archive-url=https://web.archive.org/web/20211213010038/https://www.units.miamioh.edu/cryolab/education/antarcticbestiary_terrestrial.htm|archive-date=13 December 2021|url-status=unfit}}
{{Taxonbar|from=Q136577}} {{Authority control}}
Category:Fauna of Antarctica Category:Insects described in 1900 A Category:Insects of Antarctica Category:Wingless flies Category:Taxa named by Jean-Charles Jacobs