Abundance and nutritional compositions of ruspolia differens polymorphs from Masaka District: Uganda

Abstract

This study was conducted to determine the abundance and nutritional compositions of Ruspolia differens polymorphs. The objectives of the study were: 1) to compare relative abundance of different polymorphs and males and females during the first and second swarming season and; 2) to compare the nutritional values among different polymorphs and sexes. A generalized linear model of negative binomial distribution was used to test whether abundance in the different polymorphs and insect sexes were significantly different in each of the swarming seasons. One way ANOVA in SPSS was used to test whether significant differences exist in the nutritional values of (i) different polymorphs; and (ii) between sexes. Eight polymorphs were encountered in the study. Four of which were reported 46 years ago while the other four polymorphs had never been reported in Uganda. A significant difference in the relative abundance of R. differens polymorphs (P<0.05) was observed in each swarming season and not between the two swarming seasons (P>0.05). A non-significant difference in relative abundance between males and females was observed between the two swarming seasons (P>0.05). Proximate analysis showed significant differences in protein and ash (P<0.05), but not in fat, fiber, and moisture content (P>0.05) among polymorphs. Between sexes, fiber content differed significantly (P<0.05), while protein, fat, ash, and moisture content (P>0.05) did not. Ruspolia differens color and sex did not significantly influence the fatty acids detected: myristic, palmitic, palmitoleic, stearic, oleic, linoleic, and linolenic. Calcium, zinc and iron did not significantly differ among polymorphs, while sodium, potassium and phosphorous differed significantly. Between sexes, no significant difference existed among the minerals studied: calcium, zinc, iron, sodium, potassium and phosphorus. The occurrence of polymorphs detected 46 years ago demonstrates the aspect of polymorphism maintenance, while the existence of new polymorphs suggests that this insect species is undergoing the process of evolution. The non significant difference in the relative abundance of R. differens polymorphs and insect sexes between the two swarming seasons can be attributed to the permanent adaptation of this insect species to specific environmental conditions. The nutritional composition of polymorphs most likely reflects the food sources, while that of the insect sexes is possibly influenced by the morphological and physiological differences that always occur between sexes.