Soldier caste-specific gene expression in the mandibular glands of Hodotermopsis japonica (Isoptera: Termopsidae)

Although “polymorphic castes” in social insects are well known as one of the most important phenomena of polyphenism, few studies of caste-specific gene expressions have been performed in social insects. To identify genes specifically expressed in the soldier caste of the Japanese damp-wood termite Hodotermopsis japonica, we employed the differential-display method using oligo(dT) and arbitrary primers, compared mRNA from the heads of mature soldiers and pseudergates (worker caste), and identified a clone (PCR product) 329 bp in length termed SOL1. Northern blot analysis showed that the SOL1 mRNA is about 1.0 kb in length and is expressed specifically in mature soldiers, but not in pseudergates, even in the presoldier induction by juvenile hormone analogue, suggesting that the product is specific for terminally differentiated soldiers. By using the method of 5′- and 3′-rapid amplification of cDNA ends, we isolated the full length of SOL1 cDNA, which contained an ORF with a putative signal peptide at the N terminus. The sequence showed no significant homology with any other known protein sequences. In situ hybridization analysis showed that SOL1 is expressed specifically in the mandibular glands. These results strongly suggest that the SOL1 gene encodes a secretory protein specifically synthesized in the mandibular glands of the soldiers. Histological observations revealed that the gland actually develops during the differentiation into the soldier caste.

Correlates of the desired family size among Indian communities.

The People of India database of the Anthropological Survey of India documents 631 cultural, ecological, and economic traits of the 4635 communities to which the entire Indian population is assigned. Focusing on 1342 communities of South India, we looked for correlates of low (1 or 2 children) and high (4 or more children) desired family size (DFS) reported as the norm for any given community by key informants. We found 10 cultural and 18 economic traits to be significantly correlated to high DFS and 21 cultural and 9 economic traits to low DFS. The economic traits so identified are compatible with high family size being desired by parents who have little capability of investing in quality of offspring, but whose children contribute economically from an early age. In contrast, communities desiring low family size are part of the modern intensive agriculture/organized industry/services sector and invest heavily in educating their children. A composite index based on 27 economic traits (CEI) has a high predictive value with respect to the DFS for the entire set of 4635 Indian communities. The 31 cultural traits highly correlated to high or low DFS constitute 5 clusters that can be identified as characterizing scheduled tribes, scheduled castes, rural and landless lower castes, urban upper castes, and Moslems. Whereas economic traits have similar influence on DFS within each of these ethnic categories, Moslems demonstrate a significantly higher DFS for lower values of CEI.

Reproductive cooperation between queens and their mated workers: the complex life history of an ant with a valuable nest.

The life history of Harpegnathos saltator is exceptional among ants because both queens and workers reproduce sexually. Recently mated queens start new colonies alone, but later some of the offspring workers also become inseminated and take over the egg-laying role. This alternation seems associated with the existence of very complex underground nests, which are designed to survive floods. Longevity of ponerine queens is low (a consequence of limited caste dimorphism in this "primitive" subfamily), and upon the death of an H. saltator foundress, the nest represents a substantial investment. The queen's progeny should thus be strongly selected to retain the valuable nests. Unlike the flying queens, the workers copulate with males from their own colonies, and, thus, their offspring are expected to be highly related to the foundress. Colony fission appears not to occur because a daughter fragment would lack an adequate nest for protection. Thus, the annual production of queens in colonies with reproductive workers remains essential for the establishment of new colonies. This contrasts with various other ponerine species in which the queens no longer exist.