Uric Acid and Soluble Protein Content of Feces from Three Species of Subterranean Termites (Isoptera: Rhinotermitidae)

Like all animals, termites must dispose of excess nitrogen from protein and purine digestion and metabolism. Nitrogenous wastes in insect feces are primarily ammonia or uric acid (Cochran 1985, Chapman 1998). Ammonia is often the primary nitrogenous waste product of insects that live in aquatic or very moist environments. For insects that live in dry habitats, or need to conserve body weight for flight, or have a dry diet, uric acid is typically their main nitrogenous waste product (Chapman 1998, Cochran 1985). Although termites are uricotelic, feces of a subterranean termite, Reticulitermes flavipes Kollar, were reported to have only trace amounts of uric acid (Potrikus & Breznak 1980a). Termites are coprophagous (Waller & LaFage 1987), but experimental data is lacking regarding the nutritional benefit termites receive from ingestion of their feces. Nitrogen in the feces would be of nutritional value to the xylophagous subterranean termite since wood is very low in nitrogen. Fecal protein has been suggested as a source of dietary nitrogen for termites (Nation 2002), but amounts of fecal protein have not been measured. The current study aimed to determine levels of uric acid and soluble proteins in the feces of 3 subterranean termite species, and in turn consider how these biomolecules are involved in termite digestion and nutrition. Reticulitermes virginicus Banks and R. flavipes were collected from forested areas of Pearl River County, Mississippi, and either stored in the laboratory in original nest sapwood, or separated from wood for assay within 24 h after field collection. Coptotermes formosanus Shiraki were collected in Pearl River County from a bucket trap. Soluble protein levels of whole termite workers and fecal samples were determined using Bradford reagent with a bovine serum albumin standard (Sigma-Aldrich, St. Louis, Missouri). For whole termite samples, 3 groups of 10 live workers were weighed, added to separate 1.5 ml centrifuge tubes, and ground with a micropestle. After 1 mL deionized water was added, tubes were vortexed and centrifuged 5 min at 20,600 g. Soluble protein levels in adult termites were determined spectrophotometrically at 595 nm following the standard Bradford assay procedure provided with the reagent. For determination of soluble protein levels in feces, the micro Bradford assay procedure was used. Small piles of fecal material were collected as described in Arquette & Rodriguez (2011) from laboratory arenas without food. After determination of fresh weight, feces were prepared for protein assay as for whole termite samples. Uric acid levels from feces and 3 groups of 10 whole termites were determined using a procedure detailed in Arquette & Forschler (2006). Data for uric acid and soluble protein levels are presented using the same units reported in earlier papers (Potrikus & Breznak 1980a; Arquette & Forschler 2006; Arquette et al. 2006). Uric acid was not detected in feces of 7 of 9 populations assayed (Table 1). The 2 populations measuring trace amounts of uric acid in the feces had been kept in laboratory culture for approximately 1 year, whereas other groups were assayed soon after field collection. Fecal soluble protein levels ranged from about 1 to 5 percent fresh weight (Table 2).