Brochosomes are intricately structured microscopic granules secreted by leafhoppers (the family Cicadellidae of the insect order Hemiptera) and typically found on their body surface and, more rarely, eggs. Brochosomes were first described in 1952 with the aid of an

electron microscope An electron microscope is a microscope that uses a beam of accelerated electrons as a source of illumination. As the wavelength of an electron can be up to 100,000 times shorter than that of visible light photons, electron microscopes have a hi ...

. Brochosomes are hydrophobic and help keep the insect cuticle clean. These particles have also been found in samples of air and can easily contaminate foreign objects, which explains erroneous reports of brochosomes on other insects.Rakitov R.A. (2011
Contamination as the cause of erroneous records of brochosomes.
''Psyche: A Journal of Entomology '' 2011, Article ID 767963, .

Structure and composition

The name, derived from the Greek words ''βρóχoς'' ("brochos": mesh of a net) and ''σωμα'' ("soma": body), refers to the characteristic reticulated surface of the granules. Most species of leafhoppers produce hollow spherical brochosomes, 0.2–0.7 micrometres in diameter, with a honeycombed outer wall. They often consist of 20 hexagonal and 12 pentagonal cells, making the outline of each brochosome approximating a

truncated icosahedron In geometry, the truncated icosahedron is an Archimedean solid, one of 13 convex isogonal nonprismatic solids whose 32 faces are two or more types of regular polygons. It is the only one of these shapes that does not contain triangles or squares. ...

– the geometry of a soccer ball and a C₆₀

buckminsterfullerene Buckminsterfullerene is a type of fullerene with the formula C60. It has a cage-like fused-ring structure (truncated icosahedron) made of twenty hexagons and twelve pentagons, and resembles a soccer ball. Each of its 60 carbon atoms is bonded ...

molecule. The chemical composition of brochosomes includes several kinds of proteinsRakitov R., Moysa A. A., Kopylov A. T., Moshkovskii S. A., Peters R. S., Meusemann K., Misof B., Dietrich C. H., Johnson K. P., Podsiadlowski L., Walden K. K. O. (2018) Brochosomins and other novel proteins from brochosomes of leafhoppers (Insecta, Hemiptera, Cicadellidae). ''Insect Biochemistry and Molecular Biology'', 94, 10-17. and, according to some studies,

lipids Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include ...

.Smith D.S. & Littau V.G. (1960) Cellular specialization in the excretory epithelia of an insect, ''Macrosteles fascifrons'' Stål (Homoptera). ''Journal of Cell Biology'' 8: 103-133.Gouranton J. & Maillet P.L. (1967) Origine et structure des brochosomes. ''Journal de Microscopie'' 6: 53-64. The main protein family, called brochosomins, and other kinds of proteins identified in the composition of brochosomes and their corresponding genes show no relationship to proteins and genes of any organisms outside of

Membracoidea The superfamily Membracoidea of sap-sucking true-bugs includes two of the largest families within what used to be called the "Homoptera": the leafhoppers ( Cicadellidae) and the treehoppers ( Membracidae). The other families in this group are qu ...

and thus are considered to be examples of

orphan gene Orphan genes, ORFans, or taxonomically restricted genes (TRGs) are genes that lack a detectable homologue outside of a given species or lineage. Most genes have known homologues. Two genes are homologous when they share an evolutionary history, a ...

Origin

Brochosomes are produced within cells of specialized glandular segments of the

Malpighian tubule The Malpighian tubule system is a type of excretory and osmoregulatory system found in some insects, myriapods, arachnids and tardigrades. The system consists of branching tubules extending from the alimentary canal that absorbs solutes, water, ...

s – the primary excretory organs of insects, which often serve additional functions. Each cell simultaneously manufactures a large number of brochosomes within its Golgi complexes and eventually releases them into the lumen of the tubule.Rakitov R.A. (1999) Secretory products of the Malpighian tubules of Cicadellidae (Hemiptera, Membracoidea): an ultrastructural study. ''International Journal of Insect Morphology and Embryology'' 28: 179-192. Rakitov R.A. (2000) Secretion of brochosomes during the ontogenesis of a leafhopper, ''Oncometopia orbona'' (F.) (Insecta, Homoptera, Cicadellidae). ''Tissue & Cell'' 32: 28-39.

Functions

After each molt, most leafhopper species release droplets of the brochosome-containing fluid through the anus and actively spread them over the newly formed

integument In biology, an integument is the tissue surrounding an organism's body or an organ within, such as skin, a husk, shell, germ or rind. Etymology The term is derived from ''integumentum'', which is Latin for "a covering". In a transferred, or ...

.Navone P. (1987) Origine, struttura e funzioni di escreti e secreti entomatici di aspetto ceroso distribuiti sul corpo mediante zampe. ''Annali della Facolta‘ di Scienze Agrarie della Universita‘ degli Studi di Torino'' 14: 237-294.Rakitov R.A. (1996
''Post-moulting behaviour associated with Malpighian tubule secretions in leafhoppers and treehoppers (Auchenorrhyncha: Membracoidea)''.
''European Journal of Entomology'' 93: 167-184.Rakitov R.A. (2009) Brochosomal coatings of the integument of leafhoppers (Hemiptera, Cicadellidae). In: S.N. Gorb (ed.)
''Functional Surfaces in Biology''
Vol. 1, 113-137. . This behavior is called anointing. Dry brochosomes are further distributed across the body and appendages in repeated bouts of grooming, in which leafhoppers scrub themselves with their legs. The transport of brochosomes is facilitated by groups and rows of strong

setae In biology, setae (singular seta ; from the Latin word for " bristle") are any of a number of different bristle- or hair-like structures on living organisms. Animal setae Protostomes Annelid setae are stiff bristles present on the body. ...

on the legs. The resulting coat makes the integument highly repellent to water (

superhydrophobic Ultrahydrophobic (or superhydrophobic) surfaces are highly hydrophobic, i.e., extremely difficult to wet. The contact angles of a water droplet on an ultrahydrophobic material exceed 150°. This is also referred to as the lotus effect, after the ...

) and to the leafhopper’s own liquid excreta,Rakitov R. & Gorb S.N. (2013
Brochosomes protect leafhoppers (Insecta, Hemiptera, Cicadellidae) from sticky exudates.
''Journal of the Royal Society Interface'' 10 (87). . the latter often being sugary and sticky, and thus potentially dangerous for the insect. Additional protective functions of the brochosomal coating have been hypothesized. For example, there is evidence that the anti reflective property of brochosome make surfaces coated by it appear similar to a leaf in the eyes of insects thus it can be used as camouflage for the eggs. In several New World genera of the leafhopper subfamily Cicadellinae (including the glassy-winged sharpshooter and related species) brochosomes are also used as a coating on egg masses.Hix R.L. (2001
''Egg-laying and brochosome production observed in glassy-winged sharpshooter.''
''California Agriculture'' 50 (4): 19-22.Rakitov R.A. (2004) Powdering of egg nests with brochosomes and related sexual dimorphism in leafhoppers (Insecta, Hemiptera, Cicadellidae). ''Zoological Journal of the Linnean Society'' 140: 353-381. In gravid females from these genera, the Malpighian tubules switch over from production of regular brochosomes, described above, to production of larger, typically elongate particles, up to 20 micrometres in length. Prior to laying eggs, the female places masses of such brochosomes onto its forewings, and later scrapes them off onto the freshly laid eggs with its hindlegs. The resulting powdery coat may serve various protective functions, including protection against egg-parasitoids from the order Hymenoptera ( Chalcidoidea).Velema H.P., Hemerik L., Hoddle M.S. & Luck R.F. (2005) Brochosome influence on parasitisation efficiency of ''Homalodisca coagulata'' (Say) (Hemiptera: Cicadellidae) egg masses by ''Gonatocerus ashmeadi'' Girault (Hymenoptera: Mymaridae). ''Ecological Entomology'' 30: 485-496. The shape and sculpture of such "egg" brochosomes can vary significantly among species, providing additional characteristics for species identification.

References

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External links

Brochosomes
by R. A. Rakitov, Illinois Natural History Survey
Leafhopper Egg Brochosomes Image Database
by R. A. Rakitov, Illinois Natural History Survey Cicadellidae Auchenorrhyncha Insect anatomy