Physiology of nutrient uptake by the entomophilic nematode Mermis nigrescens (Mermithidae)

Abstract

The physiology of glucose and amino acid uptake by the parasitic larval stages of the entomophilic nematode Mermis nigrescens was investigated in vitro using radioisotope-labelled substrates. Both glucose and amino acid uptake are transcuticular processes that are saturable with increasing substrate concentration but are not coupled to co-transport of sodium ions and are not energy requiring. Amino acid transport is a stereospecific membrane transport system probably located in the cuticle of the nematode. The sites for glucose transport, however, are believed to be beneath the cuticle as glucose transport is only saturable in the thin-cuticled 14-day-old larvae whereas it is not in the thick-cuticled 21-day-old larvae. Glucose transported by M. nigrescens is not converted to trehalose, a common pathway in other invertebrates, nor is trehalose found within the nematode's tissues or body fluids.