Effects of sterols, rat hematin and coproporphyrin on the free-living stages of Nematospiroides dubius and Nippostrongylus brasiliensis

Abstract

Nematospiroides dubius, unlike the closely related nematode Nippostrongylus brasiliensis, lacks a sterol requirement for the completion of its development to the L 3 stage in an aqueous suspension of formalin-killed Escherichia coli. These larvae were justascapable of completing their development to adults in mice as those grown on charcoal-feces cultures. In addition, sterols had a toxic effect on the larvae of N. dubius which was removed by substituting a Krebs-Ringer solution for distilled water. In order to interpret the absence of a sterol requirement for the development of N. dubius larvae, an analysis of the egg lipids for both species was made. N. brasiliensis had about twice the sterol concentration of N. dubius eggs. A comparison of the development for both species showed, however, that N. brasiliensis grows more than twice as much as N. dubius to reach the L 3 larval stage. Therefore, the amount of endogenous sterol is insufficient for N. brasiliensis to develop from the egg to the L 3 stage. N. dubius and N. brasiliensis also differ in their porphyrin requirements. Unlike N. brasiliensis, coproporphyrin did not increase the size of N. dubius larvae so that they were comparable to those grown on charcoal-feces cultures. Coproporphyrin did result in larvae that were more robust in appearance than those grown without a supplement.