fat body
{{short description|Organ for nutrient storage and conversion in arthropods}}
{{Distinguish|text=fat pad (Corpus adiposum), a mass of closely packed fat cells in vertebrates}}
file:Insect fat body (14523466058).jpg cells of an insect fat body]]
Fat body is a highly dynamic insect tissue composed primarily of storage cells. It is distributed throughout the insect's internal body cavity (the haemocoel), in close proximity to the hemolymph as well as organs such as the epidermis, digestive organs and ovaries. Its main functions are nutrient storage and metabolism, for which it is commonly compared to a combination of adipose tissue and liver in mammals. However, it may also serve a variety of other roles, such as: endocrine regulation, systemic immunity, vitellogenesis, and the main site of production of antimicrobial molecules called antimicrobial peptides (or AMPs).{{cite journal |last1=Arrese |first1=Estela L. |last2=Soulages |first2=Jose L. |title=Insect Fat Body: Energy, Metabolism, and Regulation |journal=Annual Review of Entomology |date=1 January 2010 |volume=55 |issue=1 |pages=207–225 |doi=10.1146/annurev-ento-112408-085356|pmid=19725772 |pmc=3075550 }}
Its presence, structure, cellular composition, location, and functions vary widely among insects, even between different species of the same genus or between developmental stages of the same individual, with other specialized organs taking over some or all of its functions.
Functions
The fat body serves different roles including lipid storage and metabolism, endocrine regulation, and immunity. The fat body contains specialized cells called mycetocytes that contain symbiotic prokaryotes living within them.{{cite journal |last1=Skowronek |first1=Patrycja |last2=Wójcik |first2=Łukasz |last3=Strachecka |first3=Aneta |title=Fat Body—Multifunctional Insect Tissue |journal=Insects |date=June 2021 |volume=12 |issue=6 |pages=547 |doi=10.3390/insects12060547 |doi-access=free |pmid=34208190 |language=en |issn=2075-4450|pmc=8230813 }} The fat body regulates insect development and longevity through regulatory molecules known as fat body signals.{{cite journal |last1=Li |first1=Sheng |last2=Yu |first2=Xiaoqiang |last3=Feng |first3=Qili |title=Fat Body Biology in the Last Decade |journal=Annual Review of Entomology |date=7 January 2019 |volume=64 |issue=1 |pages=315–333 |doi=10.1146/annurev-ento-011118-112007 |pmid=30312553 |url=https://www.annualreviews.org/doi/full/10.1146/annurev-ento-011118-112007 |language=en |issn=0066-4170}}
Development
The fat body is of mesodermal origin and is normally composed of a network of thin sheets, ribbons or small nodules suspended in hemocoel by connective tissue and tracheae, so that most of its cells are in direct contact with hemolymph.{{cite book|title=Biology of ticks|last=Coons|first=Lewis B.|date=December 2013|publisher=Oxford University Press|isbn=978-0-19-974405-3|editor-last1=Sonenshine|editor-first1=Daniel E.|pages=287–308|chapter=Fat body and nephrocytes|editor-last2=Roe|editor-first2=R. Michael}}{{cite book|title=The Insects: Structure and Function|author1=Chapman, R.F.|publisher=Cambridge University Press|year=2013|isbn=978-0-521-11389-2|editor-last1=Simpson|editor-first1=Stephen J.|pages=132–145|editor-last2=Douglas|editor-first2=Angela E.}}{{cite book|title=Encyclopedia of Insects|url=https://archive.org/details/encyclopediainse00resh_059|url-access=limited|last=Cohen|first=Ephraim|publisher=Academic Press|year=2009|isbn=978-0-08-092090-0|editor-last1=Resh|editor-first1=Vincent H.|pages=[https://archive.org/details/encyclopediainse00resh_059/page/n392 356]–357|chapter=Fat Body|editor-last2=Cardé|editor-first2=Ring T.}}