The function of the post-pharyngeal glands of the red imported fire ant, Solenopsis invicta buren

Metapleural‐ and Postpharyngeal‐Gland Secretions from Workers of the Ants Solenopsis invicta and S. geminata

“…Much controversy exists about the possible functions of these glands, as they participate in the digestion of fats, the absorption of fatty acids and glycerol esters, the regulation of caste determination [15], and as the Gestalt organ for nestmate recognition [16]. Bagne¡res and Morgan [17] suggested that PPG may serve a −purely mechanical purpose in providing lubrication and a softener for the cuticular wax×, in addition to a possible social function.…”

Lipid Mobilization and Acyl-Coenzyme A Dehydrogenase Abundance in the Postpharyngeal Gland of a Leaf-Cutting Ant

“…These results are in agreement with the transcellular route hypothesis of Delage-Darchen (1976), in which lipids go from the lumen to the gland cells and are then metabolized. Phillips and Vinson (1980) observed in S. invicta that fatty acids and triacylglycerides injected into the hemolymph did not reach the interior of the PPGs. According to Arrese and Soulages (2010), in insects, lipids from food reach the digestive tract and are then transported by lipoproteins to the fat body for storage.…”

“…Delage-Darchen (1976) proposed three hypotheses about the accumulation of lipid in PPGs: 1) transcellular route: lipids would penetrate the gland cells and be metabolized; 2) extraoral route: lipids would be regurgitated directly from the glands to other members of the colony; and 3) digestive route: lipids would flow from the glands to the crop and then to the midgut. Using labeled isotopes, Phillips and Vinson (1980) observed that, in Solenopsis invicta (B. ), fatty acids and triacylglycerides injected into the hemolymph were not transferred to the PPGs, suggesting that lipids in this gland would be derived from food.…”

“…), fatty acids and triacylglycerides injected into the hemolymph were not transferred to the PPGs, suggesting that lipids in this gland would be derived from food. Delage-Darchen (1976) and Forbes and Macfarlane (1961) hypothesized that PPGs would be responsible for the digestion of ingested fats based on the presence of digestive enzymes such as lipases in the gland lumen (Peregrine et al, 1973;Vinson et al, 1980). The digestive route hypothesis proposed by Delage-Darchen (1976) was tested by Bueno (2005), which demonstrated that Atta sexdens rubropilosa workers were capable of separating, in the final portion of the pharynx, lipid from non-lipid compounds present in the ingested food.…”

“…On a lipid-rich diet, these compounds would reach the PPGs and the non-lipid components (e.g., carbohydrates) would move to the crop, which would allow adults to use lipids available in nature (Bueno et al, 2008). Under extreme conditions, in which a large amount of lipid is offered to ants, some of it reaches the crop; however, sometime later, they return through the esophagus and enter the PPG (Phillips & Vinson, 1980;Wheeler, 1994;Jesus, 2006;Bueno et al, 2008). Moreover, using autoradiography, liquid scintillation counting, and tritiated oleic acid, Bueno (2005) showed that lipids are mobilized into the lumen of glands of A. sexdens rubropilosa workers and queens, with subsequent absorption by the gland epithelium.…”