An investigation into the physiology of urate pellet excretion by Parcoblatta fulvescens (Saussure and Zehntner) (Dictyoptera: Blattellidae)

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Virginia Polytechnic Institute and State University

Physiological parameters involved in formed urate pellet excretion by the wood cockroach, Parcoblatta fulvescens were investigated.

Uric acid excretion by last instar juvenile P. fulvescens was studied first. Food consumption, urate and non-urate pellet excretion patterns show a skewed distribution with peak feeding occurring on day six and peak voiding of both pellet types on day seven of a 17.0 ± 2.0 (SD) day ecdysial cycle. The amount of urates excreted is determined by the level of dietary protein (p<0.0001) and is linearly related to protein consumption.

Selective feeding on protein, carbohydrate and cellulose diets by reproductive female P. fulvescens was investigated. Separate consumption patterns exist for each diet. These females did not excrete uric acid.

Urate pellet consumption by reproductive female P. fulvescens was examined in relation to dietary protein and carbohydrate. Urate pellet consumption increases with decreasing protein and increasing carbohydrate levels. Females that consume urate pellets do not excrete uric acid. These results suggest that urate-containing pellets serve to transfer nitrogen reserves among individuals.

Urate spherules were enzymatically and histochemically identified in the middle and proximal regions of the Malpighian tubules of P. fulvescens, Shawella couloniana and Symploce hospes. These spherules are discharged into the hindgut in sufficient quantities to obscure the presence of food residues.

The significance of formed urate pellet excretion is discussed in relation to the nitrogen economy of Parcoblatta fulvescens.