Phytosterols as neglected nutrients in grasshoppers (Orthoptera: Acrididae)

Persistent Link:
http://hdl.handle.net/10150/282602
Title:
Phytosterols as neglected nutrients in grasshoppers (Orthoptera: Acrididae)
Author:
Behmer, Spencer Thane, 1967-
Issue Date:
1998
Publisher:
The University of Arizona.
Rights:
Copyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
Abstract:
Grasshoppers, like most other organisms, require sterols for the production of cellular membranes and, like other animals, as precursors to steroid hormones. However, grasshoppers, like other insects, cannot synthesize sterols de novo and must acquire these essential nutrients from their diets. Survival and performance of five grasshopper species, representing three phylogenetic lineages and with different host preferences, were compared on artificial diets that varied in sterol type. Sterols used were: cholesterol (Δ⁵) sitosterol (Δ⁵) stigmasterol (Δ⁵ʼ²²) spinasterol (Δ⁷ʼ²²) and lathosterol (Δ⁷); these are the most common plant sterols. For all species studied, none survived to the adult stage on stigmasterol, spinasterol or lathosterol. Performance on the cholesterol and sitosterol diets were similar for most species. This study suggests that grasshoppers, as a group, are extremely limited with respect to the sterols they can use. Grasshoppers, however, are highly polyphagous insects, often feeding on many different host-plants. Some of these host-plants contain unsuitable sterols. The effect of sterol mixtures on survival and performance was examined by rearing the grasshopper, Schistocerca americana, on artificial diets containing sitosterol (suitable) and spinasterol (unsuitable) presented either alone or in combination. Results indicated that spinasterol, even in the presence of high levels of a sitosterol, could prevent development to the adult stage. Biochemical analysis of grasshopper tissues revealed that dietary sterols with Δ⁷ and/or Δ²²-configurations could not be metabolized to cholesterol. Unmetabolized dietary sterols tended to accumulate in the midgut tissues. Grasshoppers are known to regulate feeding in response to some nutrients in relation to need. To determine if grasshoppers could regulate intake with respect to different sterols, a series of behavioral assays was performed. The grasshopper S. americana was observed feeding on artificial diets with different sterols, in some cases up to seven hours. Results suggest that S. americana developed aversion responses to diets that contained unsuitable dietary sterols (Δ⁷ and/or Δ²²) Additional experiments suggested that the aversion response developed through a combination of post-ingestive feedbacks and associative learning. Taken together, these results suggest that sterol metabolic limitations may partially determine host-plant affiliations in grasshoppers.
Type:
text; Dissertation-Reproduction (electronic)
Keywords:
Biology, Ecology.; Biology, Entomology.; Biology, Animal Physiology.
Degree Name:
Ph.D.
Degree Level:
doctoral
Degree Program:
Graduate College; Entomology
Degree Grantor:
University of Arizona
Advisor:
Bernays, Elizabeth A.

Full metadata record

DC FieldValue Language
dc.language.isoen_USen_US
dc.titlePhytosterols as neglected nutrients in grasshoppers (Orthoptera: Acrididae)en_US
dc.creatorBehmer, Spencer Thane, 1967-en_US
dc.contributor.authorBehmer, Spencer Thane, 1967-en_US
dc.date.issued1998en_US
dc.publisherThe University of Arizona.en_US
dc.rightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.en_US
dc.description.abstractGrasshoppers, like most other organisms, require sterols for the production of cellular membranes and, like other animals, as precursors to steroid hormones. However, grasshoppers, like other insects, cannot synthesize sterols de novo and must acquire these essential nutrients from their diets. Survival and performance of five grasshopper species, representing three phylogenetic lineages and with different host preferences, were compared on artificial diets that varied in sterol type. Sterols used were: cholesterol (Δ⁵) sitosterol (Δ⁵) stigmasterol (Δ⁵ʼ²²) spinasterol (Δ⁷ʼ²²) and lathosterol (Δ⁷); these are the most common plant sterols. For all species studied, none survived to the adult stage on stigmasterol, spinasterol or lathosterol. Performance on the cholesterol and sitosterol diets were similar for most species. This study suggests that grasshoppers, as a group, are extremely limited with respect to the sterols they can use. Grasshoppers, however, are highly polyphagous insects, often feeding on many different host-plants. Some of these host-plants contain unsuitable sterols. The effect of sterol mixtures on survival and performance was examined by rearing the grasshopper, Schistocerca americana, on artificial diets containing sitosterol (suitable) and spinasterol (unsuitable) presented either alone or in combination. Results indicated that spinasterol, even in the presence of high levels of a sitosterol, could prevent development to the adult stage. Biochemical analysis of grasshopper tissues revealed that dietary sterols with Δ⁷ and/or Δ²²-configurations could not be metabolized to cholesterol. Unmetabolized dietary sterols tended to accumulate in the midgut tissues. Grasshoppers are known to regulate feeding in response to some nutrients in relation to need. To determine if grasshoppers could regulate intake with respect to different sterols, a series of behavioral assays was performed. The grasshopper S. americana was observed feeding on artificial diets with different sterols, in some cases up to seven hours. Results suggest that S. americana developed aversion responses to diets that contained unsuitable dietary sterols (Δ⁷ and/or Δ²²) Additional experiments suggested that the aversion response developed through a combination of post-ingestive feedbacks and associative learning. Taken together, these results suggest that sterol metabolic limitations may partially determine host-plant affiliations in grasshoppers.en_US
dc.typetexten_US
dc.typeDissertation-Reproduction (electronic)en_US
dc.subjectBiology, Ecology.en_US
dc.subjectBiology, Entomology.en_US
dc.subjectBiology, Animal Physiology.en_US
thesis.degree.namePh.D.en_US
thesis.degree.leveldoctoralen_US
thesis.degree.disciplineGraduate Collegeen_US
thesis.degree.disciplineEntomologyen_US
thesis.degree.grantorUniversity of Arizonaen_US
dc.contributor.advisorBernays, Elizabeth A.en_US
dc.identifier.proquest9829329en_US
dc.identifier.bibrecord.b38552048en_US
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