Density‐dependent physiological phase in a non‐migratory grasshopper Aiolopus thalassinus

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 that A. 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 of A. 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 of sensilla 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 locust Locusta 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.

Development of phenotypic differences in sensillum populations on the antennae of a grasshopper, Schistocerca americana

“…Insects reared in crowds have fewer antennal sensilla, although not necessarily of all types, in the final larval instar and adult than those reared in isolation. This has been shown in the locusts Locusta migratoria (Greenwood and Chapman, 1984;Heifetz et al, 1994) and Schistocerca gregaria (Ochieng et al, 1998) and in the grasshoppers Aiolopus thalassinus (Heifetz and Applebaum, 1995) and Schistocerca americana (Chapman and Lee, 1991). In addition, L. migratoria (Rogers and Simpson, 1997) and S. americana (Bernays and Chapman, 1998) reared on artificial diet have many fewer antennal sensilla than those reared on plants and Chapman and Lee (1991) showed that the complexity of odors experienced during development, even when eating the same food, resulted in different numbers of sensilla on the antennae of final instar larvae of S. americana.…”

Nymphal density, behavioral development, and life history in a field cricket

“…The few existing studies focus in separate behavioral traits and show that, typically, individuals developed in crowded conditions behave more actively or are more explorative than individuals from less dense developmental conditions (Heifetz and Applebaum 1995;Lihoreau et al 2009). For example, in the study by Lihoreau et al (2009), cockroaches (Blattella germanica) grown in isolation showed decreased exploration and foraging activity compared to individuals grown in a crowded environment.…”

“…Only a small fraction of animal personality literature has addressed the effect of population density in changing insect behavior (Heifetz and Applebaum 1995;Javois et al 2005;Lihoreau et al 2009). The few existing studies focus in separate behavioral traits and show that, typically, individuals developed in crowded conditions behave more actively or are more explorative than individuals from less dense developmental conditions (Heifetz and Applebaum 1995;Lihoreau et al 2009).…”

Juvenile hormone and locust phase

“…We have recently documented, in laboratory studies, density-dependent behavioral plasticity of S. gregaria (Heifetz et al, 1996), of a local population of L. migratoria endemic to semi-arid regions of Israel (Heifetz et al, 1994), and of a non-migratory grasshopper, Aiolopus thalassinus (Heifetz and Applebaum, 1995). The Israeli population of L. migratoria appears to be "permanently solitary" by chromatic and morphometric criteria, but gregarious behavior can be induced by the crowding of nymphs.…”

“…The titers of total lipids and carbohydrates in an aliquot equivalent to 1 µl hemolymph were determined in control-and methoprene-treated female nymphs 24 and 72 hours after application. Total lipids were determined using the vanillin reagent as previously described (Heifetz and Applebaum, 1995), in a procedure modified from Goldsworthy and colleagues (1972). Total carbohydrates were determined with the anthrone reagent (Troy et al, 1953).…”