Anatomical, enzymatic, and microbiological studies on the digestive system of Prostephanus truncatus (Horn)

• Main Author: Vazquez-Arista, Manuel
• Published: University of Leicester 1997
• Subjects: 571.6
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.696249

Prostephanus truncatus (Horn) is a pest of stored maize that has caused major problems since appearing in Africa, though it is regarded as a minor pest in Mexico and Central America. The ability of P. truncatus to feed and breed on a great variety of environments, raises the questions to whether this beetle can break down starch and cellulose. The digestive system of P. truncatus may explain its host range. The digestive systems of adults and larvae of three P. truncatus strains from different geographic regions (Mexico, Togo, and Tanzania) were the subjects of the present work. The anatomical study of the digestive system of P. truncatus shows that the guts of adults and larvae were externally different and that these differences reflect different life spans and their different feeding habits. The internal anatomy, is similar, with the exception of the presence of peritrophic membrane and glycogen-like granules in the midgut of the adult stage. There is a cryptonephric system present in both adult and larval guts, but in different anatomical structures. The enzymatic study shows that the adult stage has more amylolytic and proteolytic activity that that of the larval stage. The same isoenzyme bands of amylolytic activity were found in the adult and larval guts, but the slowest band was less dense in the larval instar. There were differences in the isoenzyme pattern of the proteolytic activity in the three strains studied and among both stages, which suggest that the insect strains from the different geographic regions may be of different origin. The microbiological study shows the presence of cellulolytic bacteria in the digestive system of the strain from Tanzania. A microbial biofilm was detected in the hindgut (ileum) of P. truncatus, which may protect the gut bacteria. There are also methanogens which play an important role during the anaerobic hydrolysis of cellulose in some wood-boring insects. The differences among the bacteria found in the digestive system of the three strains also suggest they came from different geographic conditions. The results are consistent with evidence from other work, which suggests that the infestations in East and West Africa may be independent and have different origins.