Osmeterium

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Osmeterium of Papilio xuthus Larva.
Upper: Osmeterium partly everted. Lower: undisturbed Papilio xuthus Larva 2011-07-01.jpg
Osmeterium of Papilio xuthus Larva.
Upper: Osmeterium partly everted. Lower: undisturbed

The osmeterium is a defensive organ found in all papilionid larvae, in all stages. [1] The organ is situated in the prothoracic segment and can be everted when the larva feels threatened. The everted organ resembles a fleshy forked tongue (not unlike a snake tongue), and this along with the large eye-like spots on the body might be used to startle birds and small reptiles. The osmeterial organ remains inside the body in the thoracic region in an inverted position and is everted when the larva is disturbed in any way emitting a foul, disagreeable odor which serves to repel ants, [2] small spiders [3] and mantids. [4] To humans, this odour is rather strong but not unpleasant, usually smelling like a concentrated scent of the caterpillar's food plant and pineapple.

Contents

The constitution of the osmeterial secretion varies from species to species and contains monoterpene hydrocarbons, sesquiterpenic compounds or a mixture of aliphatic acids and esters.

The fine structure of the osmeterium of Papilio demoleus libanius Fruhstorfer has been studied and found to contain 3 types of specialised cells for synthesis, acid secretion, [5] and storage [6] of the osmeterial secretion.

Structure

Papilio demodocus larva everting its osmeterium fully, and with one horn applying the repugnatorial secretion to the finger that irritated it Papilio demodocus larva IMG 8543s.jpg
Papilio demodocus larva everting its osmeterium fully, and with one horn applying the repugnatorial secretion to the finger that irritated it
A European paper wasp interacts with a anise swallowtail caterpillar which uses its osmeterium in defense. Most scenes are repeated in closeup at one-fourth speed.

The fine structure of the osmeterium gland of Papilio larvae consists of the following cell types.

Specific study of Papilio demoleus libanius Fruhstorfer shows the possible existence of a third type of cell

Osmeterial secretion

The osmetrial secretion consists of a mixture of volatile organic acids, such as isobutyric acid and 2-methylbutyric acid. [4]

The secretion of Papilio demodocus pre-final larval instar contains methyl 3-hydroxybutanoate, 3-hydroxybutanoic acid, α-pinene, myrcene, limonene, β-phellandrene, (Z)-ocimene, (E)-ocimene, β-caryophyllene, (E)-β-farnesene, and germacrene A, as well as a number of unidentified sesquiterpenoids. [7] and that of its final instar contains 2-methylpropanoic acid, 2-methylbutanoic acid, and their methyl and ethyl esters as major constituents. [8]

Volatile components of the secretion of Parnassius glacialis (Parnassiinae, Parnassiini) consisted of isobutyric acid, 2-methylbutyric acid, and their methyl esters. That of Sericinus montela (Parnassiinae, Zerynthiini) was characterized as monoterpene hydrocarbons comprising β-myrcene (major), α-pinene, sabinene, limonene, and β-phellandrene, and of Pachliopta aristolochiae (Papilioninae, Troidini) was composed of numerous sesquiterpene hydrocarbons, including α-himachalene, α-amorphene, and germacrene A, and a few oxygenated sesquiterpenoids. [9]

Studies on osmeterial secretion makes it possible to classify the Papilionid species into two large categories on the basis of the chemical property of osmeterial secretion. [10]

Function

Eversion of the osmeterial gland is demonstrably effective in reducing predation by ants and small spiders, [3] and its chemical constituents have been shown to repel or kill ants, [2] [11] and mantids. [1] [4]

References

  1. 1 2 Chattopadhyay, Jagannath (2011). "The structure and defensive efficacy of glandular secretion of the larval osmeterium in Graphium agamemnon agamemnon Linnaeus, 1758 (Lepidoptera: Papilionidae)". Turkish Journal of Zoology. doi:10.3906/zoo-0901-24.
  2. 1 2 Eisner, Thomas; Meinwald, Yvonne C. (1965). "Defensive Secretion of a Caterpillar (Papilio)". Science. 150 (3704): 1733–1735. Bibcode:1965Sci...150.1733E. doi:10.1126/science.150.3704.1733. JSTOR   1717449. PMID   17768875.
  3. 1 2 Damman, Hans (August 1986). "The osmaterial glands of the swallowtail butterfly Eurytides marcellus as a defence against natural enemies". Ecological Entomology. 11 (3): 261–265. Bibcode:1986EcoEn..11..261D. doi:10.1111/j.1365-2311.1986.tb00302.x.
  4. 1 2 3 Chow, Y. S.; Tsai, R. S. (April 1989). "Protective chemicals in caterpillar survival". Experientia. 45 (4): 390–392. doi:10.1007/BF01957490.
  5. 1 2 Crossley, A.C.; Waterhouse, D.F. (January 1969). "The ultrastructure of the osmeterium and the nature of its secretion in Papilio larvae (lepidoptera)". Tissue and Cell. 1 (3): 525–554. doi:10.1016/s0040-8166(69)80020-0. PMID   18631483.
  6. 1 2 Lu, Chow-Chin; Chow, Yien Shing (May 1991). "Fine Structure of the Larval Osmeterium of Papilio demoleus libanius (Lepidoptera: Papilionidae)". Annals of the Entomological Society of America. 84 (3): 294–302. doi:10.1093/aesa/84.3.294.
  7. Burger, B. V.; Munro, Zenda; Röth, Marina; Spies, H. S. C.; Truter, Verona; Geertsema, H.; Habich, A. (August 1985). "Constituents of osmeterial secretion of pre-final instar larvae of citrus swallowtail,Papilio demodocus (Esper) (Lepidoptera: Papilionidae)". Journal of Chemical Ecology. 11 (8): 1093–1113. Bibcode:1985JCEco..11.1093B. doi:10.1007/BF01020678. PMID   24310333.
  8. 1 2 Burger, B.V.; Röth, Marina; Roux, Maritha le; Spies, H.S.C.; Truter, Verona; Geertsema, H. (January 1978). "The chemical nature of the defensive larval secretion of the citrus swallowtail, Papilio demodocus". Journal of Insect Physiology. 24 (12): 803–805. Bibcode:1978JInsP..24..803B. doi:10.1016/0022-1910(78)90099-9.
  9. Honda, Keiichi; Hayashi, Nanao (June 1995). "Chemical nature of larval osmeterial secretions of papilionid butterflies in the genera Parnassius, Sericinus and Pachliopta". Journal of Chemical Ecology. 21 (6): 859–867. Bibcode:1995JCEco..21..859H. doi:10.1007/BF02033466. PMID   24234323.
  10. 1 2 Honda, Keiichi (January 1980). "Osmeterial secretions of papilionid larvae in the genera Luehdorfia, Graphium and Atrophaneura (lepidoptera)". Insect Biochemistry. 10 (5): 583–588. doi:10.1016/0020-1790(80)90095-5.
  11. Honda, Keiichi (June 1983). "Defensive potential of components of the larval osmeterial secretion of papilionid butterflies against ants". Physiological Entomology. 8 (2): 173–179. doi:10.1111/j.1365-3032.1983.tb00346.x.