Comparative Morphology and Histochemistry of the Colleterial Glands in Different-Aged Females of Coptotermes gestroi (Blattaria, Isoptera, Rhinotermitidae)

Colleterial glands are female accessory glands occurring in several insect lineages and may display different functions. Within Dictyoptera, they synthesize compounds present in the ootheca of cockroaches and mantises. However, their morphology and secretory activity in Isoptera have been poorly investigated hitherto. Here, we conducted a morphological and histochemical analysis on these structures in different-aged females of Coptotermes gestroi. Thus, isolated abdomens from female alates (non-egg-laying) and 4-yr-old queens (egg-laying) were processed for routine histology. Moreover, xilydine-Ponceau and PAS histochemical tests were applied for identification of total proteins and glycoproteins, respectively. Additionally, the colleterial glands were isolated from 2-d-old (non-egg-laying) and 80-d-old (egg-laying) queens, and measured using the software ImageJ. Colleterial glands are composed of anterior and posterior glands, which are distally ramified but discharge in a common basal trunk. The anterior glands are always longer than the posterior ones, although the epithelium of the latter structures was thicker. The epithelium of both glands increases significantly in width in egg-laying-queens (P<0.01, t-test). Histological sections show colleterial glands poorly developed in female alates, while they are well-developed and extended deeply into the abdomen in 4-yr-old queens. Histochemical analysis evidenced proteinaceous secretion in the lumen of both glands in female alates. However, glycoproteinaceous granules occurred only in the lumen of the posterior glands in 4-yr-old queens, while they were absent in the lumen of anterior glands. The results suggest modification in the chemical nature of the secretion of the colleterial glands during the queen life, especially associated to the oviposition process.