Rl. Tellam et C. Eisemann, Chitin is only a minor component of the peritrophic matrix from larvae of Lucilia cuprina, INSEC BIO M, 30(12), 2000, pp. 1189-1201
The gut of most insects is lined with a peritrophic matrix that facilitates
the digestive process and protects insects from invasion by micro-organism
s and parasites. It is widely accepted that the matrix is composed of chiti
n, proteins and proteoglycans. Here we critically re-examine the chitin con
tent of the typical type 2 peritrophic matrix from the larvae of the fly Lu
cilia cuprina using a range of techniques. Many of the histochemical and bi
ochemical techniques indicate the presence of chitin, although they are oft
en adversely influenced by the presence of highly glycosylated proteins, a
principal component of the matrix. The alkali-stable fraction, which is use
d as an indicator of the maximum chitin content in a biological sample, is
only 7.2% of the weight of the matrix. Larvae fed on the potent chitin synt
hase inhibitor polyoxin D or the chitin-binding agent Calcofluor White, sho
wed strong concentration-dependent inhibition of larval weight and survival
but no discernible effects on the matrix structure. A bacterial endochitin
ase fed to larvae had no effect on larval growth and no observable effect i
n vitro on the structure of isolated peritrophic matrix. RT-PCR did not det
ect a chitin synthase mRNA in cardia, the tissue from which PM originates.
It is concluded that chitin is a minor structural component of the type 2 p
eritrophic matrix of this insect. (C) 2000 Elsevier Science Ltd. All rights
reserved.