Chromosomes, and their short arms, were measured either
on-screen or with a ruler laid over the photographs. Two calculations were used. Relative chromosome length (RCL) is the length of each chromosome expressed as a percentage of the total haploid autosome length in the nucleus. This is the procedure adopted for human chromosomes (Paris conference, 1971). Its main function is to compensate for the different degrees of contraction or condensation shown by chromosomes in different preparations; even chromosomes in different nuclei in the same preparation may exhibit different degrees of condensation which is why relative and not absolute chromosome lengths are used for comparisons.
Centromere index (CI) is the length of the short arm of a chromo-
some expressed as a percentage of the total length of the chro-
mosome. Accurate measurement of the CI is difficult because of
problems in deciding the exact centre of the centromere and the
small size of the segments involved. The CI may be expressed
conveniently using the standard terms for centromere position.
Based on Sumner (2003) the categories are: metacentric e CI
46e50; submetacentric e CI 26e45; subacrocentric e CI 16e25;
acrocentric e CI 3e15. All the Callosobruchus chromosomes are
either metacentric or submetacentric. Use of the CI, the relative
lengths of chromosomes in the same nucleus and the C-banding
are sufficient, in combination, to enable chromosomes to be
distinguished from each other. For statistical analysis, one-sample
t-tests were performed using the SPSS statistical package. The
results used are the mean and 95% confidence intervals. (N) is the
number of replicates of each chromosome; normally two per
nucleus were measured as the species are all diploid. For analysis
the mean and 95% confidence interval of each sample were.