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Belgica antarctica

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Belgica antarctica
Two Belgica antarctica adults
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Diptera
Family: Chironomidae
Genus: Belgica
Species:
B. antarctica
Binomial name
Belgica antarctica
Jacobs, 1900[1]
Distribution in Antarctica (red)

Belgica antarctica, the Antarctic midge, is a species of flightless midge, endemic to the continent of Antarctica. At 2–6 mm (0.08–0.2 in) long, it is the largest purely terrestrial animal native to the continent. It also has the smallest known insect genome as of 2014, with only 99 million base pairs of nucleotides and about 13500 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).[2] During this expedition organized by the Belgian Government, Romanian biologist Emil Racoviță collected, among other specimens, a flightless midge and its larvae.[2] Based on these specimens, the Belgian doctor and entomologist, Jean-Charles Jacobs, described Belgica antarctica Jacobs, 1900.[3] 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)[3] (now called Gerlache Strait), which in turn was named after the expedition's stead-yacht, SY Belgica.[4]

Belgica antarctica is the largest purely terrestrial animal native to the continent.[5][6][2]

Tolerance to extreme conditions

The flightlessness of B. antarctica may be an adaptation to prevent wind from blowing it into inhospitable areas.[6] It can survive freezing, but though 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.[7] Freezing tolerance is enhanced by cold hardening.[7]

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.[8]

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.[7] Exposure to temperatures of 30 °C kills individuals in a few hours.[8] It can, however, resist partial desiccation, surviving the loss of up to 70% of body water.[8]

Lifecycle

Belgica antarctica on a moss in Antarctica.

B. antarctica spends most of its two-year lifecycle in four larval stages. Overwintering may occur in any instar. Terrestrial algae (particularly Prasiola crispa), moss, organic detritus, and microorganisms provide the food for the larval stage. The adults 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 eggs. 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.[7]

Genome

As of 2014, B. antarctica has the smallest insect genome known, at 99 Mbp and 13 500 genes.[9] 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.[10]

Comparison of insect genomes
Species Genome size Coding DNA (genome percentage) Transposable element percentage
Belgica antarctica 99 Mbp 19 Mbp (19.4%) 0.12%
Aedes aegypti 1380 Mbp 22 Mbp (1.6%) 47%
Drosophila melanogaster 180 Mbp 22.8 Mbp (13.6%) 20%

See also

References

  1. ^ Jacobs, [J.-Ch.] (1900). "Diagnoses d'insectes recueillis par l'expédition antarctique Belge: Diptères". Annales de la Société entomologique de Belgique. 44: 106–107.
  2. ^ a b c Iryna Kozeretska; Svitlana Serga; Pavlo Kovalenko; Volodymyr Gorobchyshyn; Peter Convey (28 April 2021). "Belgica antarctica (Diptera: Chironomidae): A natural model organism for extreme environments". Insect Science. 29 (1): 2–20. doi:10.1111/1744-7917.12925. ISSN 1672-9609. Wikidata Q119841816.
  3. ^ a b J.C. Jacobs (1900). "Diagnoses d'insectes recueillis par l'expedition antarctique Beige (parte Chironomidae)". Annales de la Société entomologique de Belgique (in French). 44: 107– 108. ISSN 0774-5915. Wikidata Q119841481.
  4. ^ Patrick De Deckker (January 2018). "On the long-ignored scientific achievements of the Belgica expedition 1897–1899". Polar Research. 37 (1): 1474695. doi:10.1080/17518369.2018.1474695. ISSN 0800-0395. Wikidata Q119842165.
  5. ^ Usher, Michael B.; Edwards, Marion (1984). "A dipteran from south of the Antarctic Circle: Belgica antarctica (Chironomidae) with a description of its larva". Biological Journal of the Linnean Society. 23 (1): 19–31. doi:10.1111/j.1095-8312.1984.tb00803.x.
  6. ^ a b Luke Sandro & Juanita Constible. "Antarctic Bestiary — Terrestrial Animals". Laboratory for Ecophysiological Cryobiology, Miami University. Archived from the original on 23 December 2008. Retrieved December 9, 2008.
  7. ^ a b c d Lee, R. E.; Elnitsky, M. A.; Rinehart, J. P.; Hayward, S. A.; Sandro, L. H.; Denlinger, D. L. (2006). "Rapid cold-hardening increases the freezing tolerance of the Antarctic midge Belgica antarctica". Journal of Experimental Biology. 209 (3): 399–406. doi:10.1242/jeb.02001. PMID 16424090.
  8. ^ a b c Robert Michaud, M.; Benoit, J. B.; Lopez-Martinez, G.; Elnitsky, M. A.; Lee, R. E.; Denlinger, D. L. (2008). "Metabolomics reveals unique and shared metabolic changes in response to heat shock, freezing and desiccation in the Antarctic midge, Belgica antarctica". Journal of Insect Physiology. 54 (4): 645–655. doi:10.1016/j.jinsphys.2008.01.003. PMID 18313070.
  9. ^ "Antarctic midge has smallest insect genome". BBC. 2014-08-12. Archived from the original on 2014-08-12. Retrieved 2014-08-12.
  10. ^ Kelley, Joanna L.; Peyton, Justin T.; Fiston-Lavier, Anna-Sophie; Teets, Nicholas M.; Yee, Muh-Ching; Johnston, J. Spencer; Bustamante, Carlos D.; Lee, Richard E.; Denlinger, David L. (2014). "Compact genome of the Antarctic midge is likely an adaptation to an extreme environment". Nature Communications. 5: 4611. Bibcode:2014NatCo...5.4611K. doi:10.1038/ncomms5611. ISSN 2041-1723. PMC 4164542. PMID 25118180.

Further reading

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