The Endocrine-Genetic Basis of Life-History Variation: The Relationship Between The Ecdysteroid Titer and Morph-Specific Reproduction in the Wing-Polymorphic Cricket <i>Gryllus Firmus</i>
نویسندگان
چکیده
The hormonal basis of variation in life-history traits is a poorly studied topic in life-history evolution. An important step in identifying the endocrine-genetic causes of life-history variation is documenting statistical and functional associations between hormone titers and genotypes/phenotypes that vary in life-history traits. To this end, we compared the blood ecdysteroid titer and the mass of the ovaries during the fi rst week of adulthood among a fl ight-capable morph and two fl ightless morphs of the wing-polymorphic cricket Gryllus fi rmus. Ecdysteroids are a group of structurally related hormones that regulate many important aspects of reproduction in insects. Both the ecdysteroid titer and ovarian mass were signifi cantly higher in each of two fl ightless morphs compared with the fl ight-capable morph throughout the fi rst week of adulthood. Genetically based differences in the ecdysteroid titer and ovarian mass between morphs from different selected lines were similar to phenotypically based differences among morphs from the same control (unselected) lines. By day 7 of adulthood, ovaries were typically 200– 400% larger and the ecdysteroid titer was 60–300% higher in fl ightless versus the fl ight-capable morph. In addition, highly signifi cant, positive, phenotypic correlations were observed between the ecdysteroid titer and ovarian mass in pooled samples of the two fl ightless and fl ight-capable crickets from control lines or from selected lines. The ecdysteroid titer was suffi ciently elevated in the fl ightless morphs to account for their elevated ovarian growth. This is the fi rst direct documentation that naturally occurring phenotypes/genotypes that differ in early fecundity, a key life-history trait, also differ phenotypically and genetically in the titer of a key reproductive hormone that potentially regulates that trait.
منابع مشابه
The endocrine-genetic basis of life-history variation: the relationship between the ecdysteroid titer and morph-specific reproduction in the wing-polymorphic cricket Gryllus firmus.
The hormonal basis of variation in life-history traits is a poorly studied topic in life-history evolution. An important step in identifying the endocrine-genetic causes of life-history variation is documenting statistical and functional associations between hormone titers and genotypes/phenotypes that vary in life-history traits. To this end, we compared the blood ecdysteroid titer and the mas...
متن کاملHormones in the field: evolutionary endocrinology of juvenile hormone and ecdysteroids in field populations of the wing-dimorphic cricket Gryllus firmus.
Virtually no published information exists on insect endocrine traits in natural populations, which limits our understanding of endocrine microevolution. We characterized the hemolymph titers of juvenile hormone (JH) and ecdysteroids (ECDs), two key insect hormones, in field-collected short-winged, flightless (SW) and long-winged, flight-capable (LW(f)) morphs of the cricket Gryllus firmus. The ...
متن کاملJuvenile hormone titer and morph-specific reproduction in the wing-polymorphic cricket, Gryllus firmus.
Juvenile hormone titers and reproductive characteristics were measured in adult wing and flight-muscle morphs of the wing-polymorphic cricket, Gryllus firmus, during the first week of adulthood. This species has three morphs: one flight capable morph with fully-developed wings and fully-developed flight muscles [LW(F)], one flightless morph with fully-developed wings and histolyzed (non-functio...
متن کاملIntermediary Metabolism and Life History Trade-offs: Lipid Metabolism in Lines of the Wing-polymorphic Cricket, Gryllus firmus, Selected for Flight Capability vs. Early Age Reproduction.
The extent to which modifications in intermediary metabolism contribute to life history variation and trade-offs is an important but poorly understood aspect of life history evolution. Artificial selection was used to produce replicate genetic stocks of the wing-polymorphic cricket, Gryllus firmus, that were nearly pure-breeding for either the flight-capable (LW[f]) morph, which delays ovarian ...
متن کاملMorph-associated JH titer diel rhythm in Gryllus firmus: Experimental verification of its circadian basis and cycle characterization in artificially selected lines raised in the field.
Previous studies demonstrated a high-amplitude, diel cycle for the hemolymph JH titer in the wing-polymorphic cricket, Gryllus firmus. The JH titer rose and fell in the flight-capable morph (long-winged, LW(f)) above and below the relatively temporally invariant JH titer in the flightless (short-winged, SW) morph. The morph-specific JH titer cycle appeared to be primarily driven by a morph-spec...
متن کامل