Marescalchi et al. 1990

Marescalchi O, Scali V, Zuccotti M. 1990. Genome size in parental and hybrid species of Bacillus (Insecta, Phasmatodea) from southeastern Sicily: a flow cytometric analysis. Genome 33: 789-793.

These authors present the first flow cytometry analysis of genome size in the insect order Phasmatodea (stick insects); an earlier paper by other authors reported the genome size of the leaf-insect Extatosoma tiaratum.

Two of the five species studied are diploid bisexuals; one is a double allotriploid (three parental species), one is a diploid thelytokous parthenogenetic species, and one is a diploid thelytokous parthenogenetic hybrid between the two diploid bisexual species. In the two bisexual diploids, male genome sizes were significantly smaller than female, by about 15% in both cases; this difference exceeds that attributable to the absent X chromosome in these XO males, the X chromosome accounts for about 4% of the total haploid C-value. The authors suggest that male midgut cells (the measured tissue in all cases) may have higher DNA packing densities, a suggestion indirectly supported by their report that male karyotypes appear somewhat more compact than female.

The genome size data collected were used to support the hypotheses regarding the origins of the hybrid diploid and triploid species; non-significances in Student’s t-tests are argued to support intermediate genome size values.

The methods used here appear similar to the ‘best practices’ suggested by DeSalle et al. (2005): 50ug/mL of Propidium Iodide, incubated with the sample and co-prepared standard for at least 20 minutes. Interestingly, their narcotizing agent of choice was chloroform, as we use in our lab.