Submitted to: International Society of Chemical Ecology Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 12/18/2004
Publication Date: 1/28/2005
Citation: Raina, A.K., Y.I. Park, B.F. Ingber and C. Murphy. 2005. Structure and developmental changes in the tergal glands of adult females of Coptotermes formosanus. Arthropod Structure and Development. 34:117-124.
Technical Abstract: The Formosan subterranean termite Coptotermes formosanus is a major urban pest attacking wooden structures and live trees in several southern states and Hawaii. Each mature colony can have several million individuals. Every year from April-June, these colonies produce swarms of winged adults. After a brief flight, the adults land, drop their wings and form tandem pairs with female in the lead and male maintaining contact with the posterior end of the female. Initial contact between sexes may be accidental and does not involve a long range sex attractant. Once a suitable place is found, these primary reproductives build a nuptial chamber, mate and lay eggs. The adult females have a pair of tergal glands below the 9th and 10th tergites. The larger gland is 1.1 mm long and 0.18 mm at its widest and both have a segmented appearance. Situated just below the cuticle, the glands have two distinct regions. The outer layer consists of type I cells with a characteristic layer of microvilli. These cells possibly open to the outside through narrow cuticle lined ducts. The lower layer consists of glandular cells, packed with electron dense granules measuring an average of 0.9 µm in diameter. Comparison of HPLC-APCI-MS of extracts of 9th-10th abdominal segments of both female and male showed a peak present only in the female extracts. APCI-MS of the peak showed ions for the triacylglycerol, trilinolein. Males have no tergal glands and no trilinolein. Newly molted, pre-flight females contain negligible amounts of trilinolein, which gradually increases to about 800 ng in post-flight females. Trilinolein titer in both virgin and mated females decreases gradually reaching about 20 ng in 42 days. Structurally, the glands of newly molted females have electron lucent granules in place of electron dense granules. These may represent a precursor of trilinolein. On the other hand females, seven days after mating, show breakdown of type I cells and appearance of large number of vacuoles. The electron dense granules coalesce to form large granules that appear to move towards the intersegmental membrane for possible release. The males which have originally no trilinolein, acquire increasing amounts of it, apparently from the female as a nuptial/companionship gift. The trichoid sensilla near the tip of the maxillary palps of males did show significant increase in the electrical activity in response to trilinolein. However, the exact role of trilinolein in sexual behavior is not fully understood. There is also the possibility for the presence of a close range sex pheromone emitting from the fine openings in the cuticle above the tergal glands. This needs further investigation. Acknowledgments: We would like to thank Christopher Florane for outstanding technical assistance, Eric Erbe for scanning electron-microscopy and J. C. Dickens for electrical recordings.