Cryptotermes

Abstract: The phylogeny of microorganisms of the symbiotic community in the gut of a lower termite, Cryptotermes domesticus (order Isoptera, family Kalotermitidae), was investigated without culturing the resident microorganisms. Portions of the small-subunit rRNA genes (16S rRNAs) were directly amplified from the mixed-population DNA of the termite gut by the PCR and were clonally isolated. Analysis of partial sequences of 16S rRNA showed the existence of prokaryotic species related to the genera Methanobrevibacter, Leuconostoc, Bacteroides and Treponema, but most of the sequences were those of yet unknown species. Unique sequences showing very low sequence similarity to known 16S rRNA sequences were also found although they were significantly clustered with the High G+C Gram-positive bacteria. Comparisons of these sequences with those from the symbiotic microorganisms in other termite species revealed the existence of termite-specific groups of organisms.

Abstract: In termites the evolution of reproductive altruism is not based on a particularly high relatedness between nestmates. For the evolution and maintenance of the ancestral sterile soldier caste, the benefits generated by the soldiers’ presence must compensate the loss of the soldiers’ reproductive potential. To study the impact of soldiers on colony's fitness, we manipulated the proportion of soldiers to nonsoldiers in colonies of the dry-wood termite Cryptotermes secundus.‘Soldier-less’ colonies were obtained by removing soldiers and inhibiting their development with an extract of soldier heads. The colonies were set up for 1 year in experimental nests in the field. ‘Soldier-less’ colonies produced fewer soldiers. The reduction of soldiers neither affected colony survival nor helper growth, but fewer dispersing sexuals were produced in ‘soldier-less’ than in control colonies. This confirms what was only supposed so far, that in termites soldiers are maintained for their intrinsic benefit to cost ratio.

Abstract: The molecular mechanisms regulating caste determination and reproductive division of labor, the hallmarks of insect societies, are poorly defined. The identification of key genes involved in these developmentally important processes will be essential to gain a better understanding of the mechanisms controlling one of the most impressive examples of polyphenism, the caste structure of eusocial species. Here, we applied representational difference analysis of cDNAs, to study differential gene expression between queens (female neotenics) and workers in the dry wood termite Cryptotermes cynocephalus and identified 13 genes that were highly expressed in queens. In addition, we partially cloned several homologous genes of the related termite species Cryptotermes secundus and compared the expression profiles of 10 homologous genes. In most cases, the preferential expression in female neotenics was not conserved between species, despite the close phylogenetic relationship of both Cryptotermes species. It is possible that these genes are associated with known species-specific differences in caste development modes. Only three genes (Neofem1, 2, and 3) showed a conserved and highly preferential expression in female neotenics, suggesting that their products may play important roles in female reproductives, in particular in controlling caste determination and reproductive division of labor.