Genetic and diurnal variation in the juvenile hormone titer in a wing-polymorphic cricket: Implications for the evolution of life histories and dispersal
Aj. Zera et G. Cisper, Genetic and diurnal variation in the juvenile hormone titer in a wing-polymorphic cricket: Implications for the evolution of life histories and dispersal, PHYSIOL B Z, 74(2), 2001, pp. 293-306
The wing-polymorphic cricket, Gryllus firmus, contains (1) a flight-capable
morph (LWf) with long wings and functional flight muscles, (2) a flightles
s morph with reduced wings and underdeveloped flight muscles (SW), and (3)
a flightless morph with histolyzed flight muscles but with fully developed
wings (LWh). The LWf morph differed genetically from the SW morph and pheno
typically from the LWh morph in the size of flight muscles, ovarian growth
during the first week of adulthood, and the hemolymph titer of juvenile hor
mone (JH). This is the first study to document that phenotypes that differ
genetically in morphological aspects of dispersal capability and in ovarian
growth also differ genetically in the titer of a hormone that potentially
regulates those traits. The JH titer rose 9-100-fold during the photophase
in the flight-capable LWf morph but did not change significantly during thi
s time in either flightless morph. Prolonged elevation of the in vivo JH ti
ter in flight-capable females, by topical application of a hormone analogue
, caused a substantial increase in ovarian growth and histolysis of flight
muscles. The short-term, diurnal rise in the JH titer in the dispersing mor
ph may be a mechanism that allows JH to positively regulate nocturnal fligh
t behavior, while not causing maladaptive histolysis of flight muscles and
ovarian growth. This is the first demonstration of naturally occurring, gen
etically based variation for diurnal change in a hormone titer in any organ
ism.