ABSTRACT
The effects of temperature change on phospholipid content in metacercariae of Posthodiplostomum minimum and their second intermediate hosts, Lepomis macrochirus, were examined to gauge similarities in the homeoviscous adaptation of host and parasite membranes to environmental thermal change. Heart, liver, and muscle tissues from individual L. macrochirus responded to environmental temperature declines with a decrease in the ratio of phosphatidylethanolamine (PE) to phosphatidylcholine (PC). Increases in membrane PE concentration increase membrane fluidity, maintaining fish membrane function as environmental temperature declines. However, the metacercariae of P. minimum exhibit changes in cholesterol levels, total lipid levels, and lipid composition (PE/PC) that contrast the normal changes for homeoviscous membrane adaptation exhibited by their fish intermediate hosts. The parasites seem to rely on their hosts for homeoviscous adaptation within normal developmental temperature ranges, pooling both cholesterol and PE as energetic stores for development and ontological transitions signaled by elevated temperatures.
Subject(s)
Membrane Lipids/metabolism , Perciformes/metabolism , Perciformes/parasitology , Phospholipids/metabolism , Temperature , Trematoda/metabolism , Acclimatization/physiology , Animals , Cholesterol/chemistry , Cholesterol/metabolism , Fish Diseases/parasitology , Lipid Bilayers/chemistry , Lipid Bilayers/metabolism , Liver/chemistry , Liver/metabolism , Membrane Fluidity/physiology , Membrane Lipids/chemistry , Muscles/chemistry , Muscles/metabolism , Myocardium/chemistry , Myocardium/metabolism , Phosphatidylcholines/chemistry , Phosphatidylcholines/metabolism , Phosphatidylethanolamines/chemistry , Phosphatidylethanolamines/metabolism , Phospholipids/chemistry , Random Allocation , Trematoda/chemistry , Trematode Infections/parasitology , Trematode Infections/veterinaryABSTRACT
Perceptual error in the Müller-Lyer and the Horizontal-Vertical illusions was quantified using nonparametric signal-detection measures of sensitivity and response bias. Sensitivity scores were positively related to signal strength with the greatest values observed for the strongest signals. Sensitivity at each signal strength did not differ between the two illusions. Response-bias scores were inversely related to signal strength, with the most conservative biases observed for the strongest signals. Response biases for each signal strength were significantly more conservative for the Horizontal-Vertical than for the Müller-Lyer illusion.
