Thiamethoxam is a neonicotinoid that has been used to control insect pests. The literature reports a few behavioral studies evaluating the toxic effect of thiamethoxam in ants; however, there are scarce studies at the cellular level. The present research evaluated the effects of thiamethoxam in labial (LG) and mandibular glands (MG), fat bodies (FB), and Malpighian tubules (MT) of workers of Atta sexdens, using transmission electron microscopy. The duct and secretory cells of LG were profoundly affected, then the production of saliva can be compromised, as well as its quality and subsequent use. In MG, reservoir and canaliculi cells presented slight alterations; however, MG secretory cells presented vacuoles containing lamellar structures, increased lipid production, and a large amount of mitochondria, which may lead to organ's malfunctioning. The FB cell alterations do not seem enough to cause significant changes that lead to cell death. Prominent changes in MT, such as loss of the electron-dense concentric ring, increased smooth endoplasmic reticulum, loss of basal infolds, vacuoles containing mineralized granules, and lamellar structures associated with mitochondria, suggest that their excretory function is compromised. In conclusion, thiamethoxam acts not only in the nervous system but also contributes to systemic toxicity on the target organism.

The structure of hitherto-unknown exocrine glands in the caudal rami of the pelagic copepods of the genus Calanus was investigated, together with the vertical, diel and seasonal variations in the occurrence of granules secreted from the glands. Zooplankton samples were collected in Sagami Bay by vertical tows of a net from 4 discrete layers at 250-m intervals in the upper 1000 m both day and night, with an additional seasonal sampling in the upper 200 m. The samples contained copepodids of Calanus sinicus (stages IV–VI), C. jashnovi (stages IV–V), and unidentified Calanus (stages I–III), which possessed the glands regardless of the developmental stage and sex. Each caudal ramus has an inner- and an outer gland each of which opens in a pore at the ventral base of a caudal seta. According to light microscopy the cavities of only the inner glands contained many transparent granules, some of which appeared to have been discharged to the environment. The granules were present regardless of day/night, depth, and season, with the maximum number of 52/copepod. The cells surrounding the inner cavity contained well-developed rough endoplasmic reticulum, mitochondria, Golgi-bodies, and secretory granules; the outer cavity contained granules of much lower density than those in the inner cavity. These observations rule out the possible functions of the glands for egg and sex pheromone production, and suggest most likely function is predator avoidance. However, neither has mechanical disturbance excited luminescence, nor has ultraviolet emission excited fluorescence, suggesting the secretion is non-luminescent. Alternative possible functions include secretion of defensive substances or substances that might enhance swarm formation. A survey of preserved copepod collections indicated presence of similar glands in Calanus helgolandicus, C. pacificus, Cosmocalanus darwinii, Mesocalanus tenuicornis, and Nannocalanus minor, suggesting evolution of the glands in the common ancestor of these species that comprise a monophyletic group within the Calanidae.