Quinone Tanning in the Cocoon-Shell of Dendroœlum lacteum

Abstract

DR. C. H. BROWN, in her letter in Nature of February 17, suggests that the ‘winter egg case’ (cocoon-shell) of planarians may be a tanned protein. Vialli1,2 has shown that the vitelline cells of Distomum hepaticum and Dendroœlum lacteum contain a substance in which there is a di-or poly-phenol. Later, Stevenson3 showed that the egg-shell of Distomum hepaticum is composed of a quinone-tanned protein, similar to the sclerotin of the cockroach ootheca4, and derived from the granules or globules in the vitelline cells. During my investigation of cocoon formation in Dendroœlum locteum, I have found that the cocoon-shell, as in Trematodes, has the phenolic precursor in the globules of the vitelline cells. Evidence for this arises from histochemical tests carried out on sections of whole animals and of both tanned and untanned cocoon-shells. Both the globules in the vitelline cells and the untanned shell of a forming cocoon show a positive reaction to the argentafine test5, and also show definite green coloration when tested with ferric chloride; this changes to pink on the addition of sodium carbonate, indicating the presence of an o-dihydroxyphenol. Standard protein tests carried out on the cocoon-shell were also positive. The origin of the protein present in the cocoon-shell and of the oxidase necessary to produce quinone from phenol is now being investigated.

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References

  1. 1

    Vialli, M., Boll. Zool. (Naples), 4, 135 (1933).

  2. 2

    Vialli, M., Boll. Zool. (Turin), 5, 21 (1934).

  3. 3

    Stevenson, W., Parasit., 38, 128 (1947–48).

  4. 4

    Pryor, M. C. M., Proc. Roy. Soc., B, 128, 378 (1940).

  5. 5

    Lison, L., “Histochimie Animale” (Paris, 1936).

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NURSE, F. Quinone Tanning in the Cocoon-Shell of Dendroœlum lacteum. Nature 165, 570 (1950) doi:10.1038/165570a0

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