Issus
Issus coleoptratus
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Hemiptera
Suborder: Auchenorrhyncha
Infraorder: Fulgoromorpha
Superfamily: Fulgoroidea
Family: Issidae
Subfamily: Issinae
Genus: Issus
Fabricius, 1803

Issus is a genus of planthoppers belonging to the family Issidae of infraorder Fulgoromorpha of suborder Auchenorrhyncha of order Hemiptera. Like most members of the order Hemiptera (popularly known as the "bug" or "true bugs" order) they live on phloem sap that they extract with their piercing, sucking mouth parts.

Planthoppers are the only animals known to possess a gear mechanism,[1] and Issus coleoptratus is the first type of planthopper to have the mechanism formally described.[2][3][4] The mesh sector gears do not transform velocity or torque, and they do not convey much of the power; they only synchronize the jumping motion of the hind legs, preventing yaw (rotation).

Description

The genus Issus includes small insects generally flightless with a stocky, brown body and forewings with strong pronounced ribs. They feed on phloem. Species of this genus are present in most of Europe, in the Near East, and in North Africa.

Gear mechanism

Planthoppers (of which there are over 12,000 known species) are the first animals found to possess a biological form of a mechanical gear, used in locomotion (crocodiles possess a heart valve with cog-like projections, but they have no cog-like function.[5]) The first formal description of this mechanism was in the species Issus coleoptratus. The gears keep the hind legs in synchronization, allowing the bugs to jump accurately in a straight line, at an acceleration of nearly 400 g in two milliseconds.[2] Each leg has a 400-micrometer strip of tapered teeth, pitch radius 200 micrometers, with 10 to 12 fully interlocking spur-type gear teeth, including filleted curves at the base of each tooth, which reduces wear and the risk of shearing.[1][6][7][8] The gears aren't connected all the time. One is located on each of the juvenile insect's hind legs, and when it prepares to jump, the two sets of teeth lock together. As a result, the legs move in almost perfect unison for a straight jump, giving the insect more connected power as the gears rotate together to their stopping point and then unlock.[6]

The existence of the gears in planthoppers had been known for decades,[9] but zoologist Gregory Sutton and his co-authors only recently characterized their functional significance by doing high-speed photography of Issus coleoptratus at Cambridge University.[2][10] The gears are found only in the nymph forms of all planthoppers, and are lost during the final molt to the adult stage.[3] The juveniles repeatedly molt and grow new gears before adulthood.[1] Entomologist Malcolm Burrows has posited that the advantage of losing the gears after the last molt is that, if the gears were to be broken on an adult insect, this would be irreparable.[3] The legs of an adult planthopper are synchronized by a different mechanism, a series of protrusions that extend from both hind legs, and push the other leg into action.[1]

Before the planthopper nymph's hind leg mesh gears were discovered, it was assumed that only humans made and used gears.[4]

List of species

This genus include the following 29 species:

  • Issus analis Brullé, 1832
  • Issus bellardi Melichar, 1906
  • Issus bimaculatus Melichar, 1906
  • Issus cagola Remane, 1985
  • Issus cagracala Remane, 1985
  • Issus cahipi Remane, 1985
  • Issus canalaurisi Sergel, 1986
  • Issus canariensis Melichar, 1906
  • Issus capala Remane 1985
  • Issus capapi Remane1985
  • Issus cinereus (Olivier, 1791)
  • Issus climacus Fieber, 1876
  • Issus coleoptratus (Fabricius, 1781)
  • Issus distinguendus Lindberg, 1954
  • Issus fieberi Melichar 1906
  • Issus fissala Fieber 1876
  • Issus gracalama Remane, 1985
  • Issus gratehigo Remane, 1985
  • Issus hipidus Remane, 1985
  • Issus lauri Ahrens, 1818
  • Issus maderensis Lindberg, 1956
  • Issus muscaeformis (Schrank, 1781)
  • Issus padipus Remane, 1985
  • Issus paladitus Remane, 1985
  • Issus palama Remane, 1985
  • Issus pallipes Lucas, 1853
  • Issus pospisili Dlabola, 1958
  • Issus rarus Lindberg, 1954
  • Issus truncatus Fieber, 1876

See also

References

  1. 1 2 3 4 Stromberg, Joseph (2013-09-12), "This Insect Has The Only Mechanical Gears Ever Found in Nature", Smithsonian Magazine, retrieved 2020-11-18
  2. 1 2 3 Burrows, Malcolm; Sutton, Gregory (2013-09-13), "Interacting gears synchronize propulsive leg movements in a jumping insect" (PDF), Science, 341 (6151): 1254–1256, Bibcode:2013Sci...341.1254B, doi:10.1126/science.1240284, hdl:1983/69cf1502-217a-4dca-a0d3-f8b247794e92, PMID 24031019, S2CID 24640726
  3. 1 2 3 Lee, Jane J. (2013-09-12), "Insects Use Gears in Hind Legs to Jump", National Geographic
  4. 1 2 "Gears evolved in nature long before humans 'invented' them", theguardian.com, 2013-09-13, archived from the original on 2014-10-08
  5. ↑ Axelsson, Michael; Franklin, Craig E.; Löfman, Carl O.; Nilsson, Stefan; Grigg, Gordon C. (1996), "Dynamic anatomical study of cardiac shunting in crocodiles using high-resolution angioscopy" (PDF), The Journal of Experimental Biology, 199 (Pt 2): 359–65, doi:10.1242/jeb.199.2.359, PMID 9317958
  6. 1 2 Robertson, Adi (September 12, 2013). "The first-ever naturally occurring gears are found on an insect's legs". The Verge. Retrieved November 18, 2020.
  7. ↑ Functioning 'mechanical gears' seen in nature for the first time, Cambridge University, 2013.
  8. ↑ Functioning 'mechanical gears' seen in nature for the first time, PHYS.ORG, Cambridge University, 2013-09-12
  9. ↑ Sander, K. (1957), "Bau und Funktion des Sprungapparates von Pyrilla perpusilla WALKER (Homoptera - Fulgoridae)", Zool. Jb. Jena (Anat.) (in German), 75: 383–388
  10. ↑ Herkewitz, William (2013-09-12), "The First Gear Discovered in Nature", Popular Mechanics
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