Quantitative aspects of reproduction and larval nutrition in Glossina morsitans morsitans westw. (diptera, glossinidae) fed in vitro

Abstract

A self-supporting colony of Glossina morsitans morsitans Westw. fed through Agar/Parafilm membranes upon haemolysed bovine blood for five days and upon the ears of living rabbits for one day each week (M₅R₁) is reported. This colony produced offspring intermediate in weight between those produced by adults fed exclusively upon living hosts (R₆) and those fed exclusively through membranes (M₆). Life span and fecundity of M₅R₁ adult females was close to that of R₆ females and superior to that of M₆ females whose reproductive performance was inadequate to maintain a colony. The different regimes did not affect feeding frequency, although adult nutrient intake was lower in M₆ than in R₆ females, and M₅R₁ females were intermediate. Larval growth as measured by dry weight increase and total nitrogen content at 24-h intervals throughout the second reproductive cycle showed that growth rates of all three instars were lower with M₆ than with R₆ feeding regimes, while the M₅R₁ regime produced an intermediate effect. There was a linear relationship between dry weight and total nitrogen content for all developmental stages from egg to fully grown third-instar larva, and this was unaltered by the feeding regime, suggesting that gross nutrient composition remained constant and was unaffected by the adult diet. Evidence is presented that a large critical blood-meal ingested on or about the fifth day of a nine-day interlarval period provides the bulk of nutrient for larval growth. Histological examination of the adult uterine glands showed that the greatest secretory activity was coincident with a waning of cell size and that nutrient secretion is a continuous process from the time of hatching of the first-instar larva until parturition. It is concluded that poor reproductive performance of adults maintained on in vitro feeding regimes is due mainly to quantitative aspects of feeding rather than qualitative deficiencies in the diet.