Search USGS⌕ Search

Geology topics

P.W. Johnson

Publications and source records attributed to P.W. Johnson.

4 recordsLinked to original sources
USGS1997

Pathogenicity of entomopathogenic fungus Metarhizium anisopliae (Deuteromycetes) to Ixodes scapularis (Acari: Ixodidae)

The entomopathogenic fungus Metarhizium anisopliae is highly pathogenic to the black-legged tick, Ixodes scapularis. Spore concentrations of 108/ml for engorged larvae and 107/ml for engorged females resulted in 100% tick mortality, 2 wk post-infection. The LC50 value for engorged larvae (concentration to kill 50% of ticks) was 107 spores/ml. Metarhizium anisopliae shows considerable potential as a microbial control agent for the management of Ixodes scapularis.

Journal of Parasitology↗
USGS1996

Ultrastructure of the haemocytes of Ixodes scapularis (Acari: Ixodidae)

Haemocytes of Ixodes scapularis were characterized on the basis of their ultrastructure by transmission electron microscopy of thin sections. Three types of haemocytes were identified: prohaemocytes, plasmatocytes, and granulocytes. Prohaemocytes are undifferentiated cells containing very little cytoplasm (high nucelo-cytoplasmic ratio). Plasmatocytes are rich in free ribosomes, mitochondria, rough endoplasmic reticulum, and have numerous peripheral vacuoles. Granulocytes are polymorphic cells containing granular inclusions and filopodia on the surface. Granulocytes are divided into two morphological types, type I and II, based on the structure of the granules.

Acarologia↗