Enzymatic differences in the digestive system of the adult and larva of Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae)

Abstract

Prostephanus truncatus (Horn) is a pest of stored maize that has caused major problems since appearing in Africa in the 1970s, although it is regarded as a minor pest in Mexico and Central America. The study of the digestive system of P. truncatus adults and larvae from Mexico, Togo and Tanzania is the subject of the present work. Adults and larval guts have two pH values of 6.2 in the midgut and fore-hindgut (ileum) and 4.2–4.6 in the mid-, and hind-hindgut. In these two pH regions and for the two stages, the passage time of the food bolus was different, being faster in the larval stage, mainly in the 6.2 pH portion. The enzymatic study shows higher amylolytic and proteolytic activity in the adult stage. In the three insect colonies studied and both adult and larval guts, the same isoenzyme pattern of amylolytic activity in electrophoretic zymograms was found, although, the slowest band was present in smaller quantities in the larvae instars. In the case of the proteolytic activity, the isoenzyme pattern showed differences among the three insect colonies studied but no differences between stages were found. These results suggest that the two insect colonies from Africa have different geographic origins.