Involvement of the Salivary Glands in the Suicidal Defensive Behavior of Workers in Neocapritermes opacus (Blattaria, Isoptera, Termitidae)

Suicidal behavior in termite workers is an extreme defensive strategy, probably a consequence of having a low number of soldiers available in the colony and there being high predation from enemies. We investigated the suicidal mechanism in workers of the Neotropical termite Neocapritermes opacus, wh...

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Bibliographic Details
Published in:Microscopy and microanalysis 2020-08, Vol.26 (4), p.846-854
Main Authors: Costa-Leonardo, Ana Maria, Janei, Vanelize, Santos, Amanda Marcelino Ribeiro dos, Silva, Iago Bueno da
Format: Article
Language:English
Subjects:
Animals
Behavior, Animal - physiology
Bromophenol blue
Cytoplasm
Defensive behavior
Foraging behavior
Foregut
Isoptera - physiology
Micrographia
Microscopy
Mitochondria
Morphology
New species
Parietal cells
Parietal Cells, Gastric - physiology
Predation
Salivary gland
Salivary glands
Salivary Glands - physiology
Secretory vesicles
Self destructive behavior
Soldiers (insect caste)
Suicides & suicide attempts
Termites
Vesicles
Workers (insect caste)
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Summary:Suicidal behavior in termite workers is an extreme defensive strategy, probably a consequence of having a low number of soldiers available in the colony and there being high predation from enemies. We investigated the suicidal mechanism in workers of the Neotropical termite Neocapritermes opacus, which involves salivary gland autothysis followed by body cuticle rupture and the release of a defensive secretion. Autothysis was triggered by a physical stimulus such as a soldier bite that causes the protrusion of the salivary acini, burst reservoirs, and foregut. Histochemical and ultrastructural analyses showed salivary acini composed of peripheral parietal cells and two types of central cells, types I and II. Type I cells are filled with large electron-lucent secretory vesicles, which reacted positively to bromophenol blue and xylidine-Ponceau tests, indicating the occurrence of proteins. Type II cells are elongated and display smaller apical secretory vesicles. Parietal cells present an intracellular canaliculus with dense microvilli and cytoplasm rich in mitochondria and large electron-dense vesicles, which may participate in the self-destructive mechanism. Worker suicidal behavior was previously reported for N. taracua and N. braziliensis. N. opacus is a new species in which a salivary weapon has been developed and factors contributing to this altruistic response are discussed.
ISSN:1431-9276
1435-8115
DOI:10.1017/S1431927620001646