Fluorescence in situ hybridization: a new method for determining primary sex ratio in ants

The ant genomes have been invaded by several types of mariner transposable elements

To date, only three types of full-length mariner elements have been described in ants, each one in a different genus of the Myrmicinae subfamily: Sinvmar was isolated from various Solenopsis species, Myrmar from Myrmica ruginodis, and Mboumar from Messor bouvieri. In this study, we report the coexistence of three mariner elements (Tnigmar-Si, Tnigmar-Mr, and Tnigmar-Mb) in the genome of a single species, Tapinoma nigerrimum (subfamily Dolichoderinae). Molecular evolutionary analyses of the nucleotide sequence data revealed a general agreement between the evolutionary history of most the elements and the ant species that harbour them, and suggest that they are at the vertical inactivation stage of the so-called Mariner Life Cycle. In contrast, significantly reduced levels of synonymous divergence between Mboumar and Tnigmar-Mb and between Myrmar and Botmar (a mariner element isolated from Bombus terrestris), relative to those observed between their hosts, suggest that these elements arrived to the species that host them by horizontal transfer, long after the species' split. The horizontal transfer events for the two pairs of elements could be roughly dated within the last 2 million years and about 14 million years, respectively. As would be expected under this scenario, the coding sequences of the youngest elements, Tnigmar-Mb and Mboumar, are intact and, thus, potentially functional. Each mariner element has a different chromosomal distribution pattern according to their stage within the Mariner Life Cycle. Finally, a new defective transposable element (Azteca) has also been found inserted into the Tnigmar-Mr sequences showing that the ant genomes have been invaded by at least four different types of mariner elements.

Expression of abdominal-A homeotic gene in ants with different abdominal morphologies

In most insect groups, the Hox gene abdominal-A specifies the development of consecutive monotonous anterior abdominal segments. In contrast, the ant family shows pronounced differentiation of the anterior abdominal segments: the first is fused to the thoracic segments, the second, the petiole, is a specialised segment in all ants and the third, the post-petiole, can either take the appearance of a gastric segment (as in the Dolichoderinae) or of a petiole-like segment, (as in the Myrmicinae). Changes in the regulation of the abdominal-A gene are suspected to be instrumental in this morphological differentiation. Previous work has shown that the genomic coding sequences of the abdominal-A gene is nearly identical between all ant subfamilies. Therefore any evolutionary change within the ant family in the developmental activity of abdominal-A is most likely due to a change in gene expression than to a change in the activity of the Abdominal-A protein. Here I present the embryonic expression of the abdominal-A gene in two ant species with different abdominal morphologies. I find that by the late-germ band stage, abdominal-A transcripts are detected in a similar pattern in both species whereas the early patterning of abdominal-A is distinctly different between the two species.