Density-dependent physiological phase in a non-migratory grasshopperAiolopus thalassinus |
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Authors: | Y Heifetz and S W Applebaum |
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Institution: | (1) Department of Entomology, Faculty of Agriculture, The Hebrew University, P.O. Box 12, 76100 Rehovot, Israel |
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Abstract: | Aiolopus thalassinus thalassinus (Fabricius) (Orthoptera: Acrididae) is a non-migratory grasshopper of widespread geographical distribution, also endemic
in the Tel-Arad region of the Northern Negev of Israel, where it is liable to sporadically damage agricultural crops. Periodic
sampling in uncultivated ‘batha’ and agricultural fields, conducted during 1990/1991, indicate thatA. thalassinus populations exhibit seasonal fluctuations in density. Local spatial and temporal distribution, within this region, are dependent
on food availability. Field observations and laboratory studies suggest that the local population ofA. thalassinus exhibits genetic heterochromy unaffected by density. The duration of nymphal developmental is 34 days for nymphs reared in
isolation, whereas crowded nymphs complete their development within only 21 days. No striking density related changes in gross
morphometric features are evident, but, in adults from isolated culture, an increased abundance ofsensilla coeloconica, presumably involved in olfactory chemoreception, may be functionally related to enhanced (23.6-fold higher) activity of
nymphs reared under crowded conditions. This higher level of activity is correlated to higher levels of energy reserves in
the haemolymph — lipids and carbohydrates — and to increased respiration. Finally, the individual food consumption of nymphs
from crowded culture is almost 5-fold higher than that of isolated nymphs and may increase the potential for crop damage.
These results are similar to those obtained with the migratory locustLocusta migratoria and support the hypothesis that non-migratory grasshoppers exhibit some density-dependent physiological characteristics of
locusts, but do not exhibit overt chromatic or morphometric phase characteristics. |
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Keywords: | Orthoptera Aiolopus thalassinus Locusta migratoria antennal sensilla phase morphometrics behaviour haemolymph lipid haemolymph carbohydrate respiration food consumption |
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