Genetic and Diurnal Variation in the Juvenile Hormone Titer in a Wing-Polymorphic Cricket: Implications for the Evolution of Life Histories and Dispersal

Authors

Anthony J. Zera, University of Nebraska - LincolnFollow
Gretchen Cisper, University of Nebraska - Lincoln

Date of this Version

March 2001

Comments

Published in Physiological and Biochemical Zoology 74(2):293-306. 2001. Copyright 2001 by The University of Chicago Press. Used by permission. DOI 1522-215U2001n402-0083S03.00

Abstract

The wing-polymorphic cricket, Gryllus firmus, contains (1) a flight-capable morph (LW_f) with long wings and functional flight muscles, (2) a flightless morph with reduced wings and underdeveloped flight muscles (SW), and (3) a flightless morph with histolyzed flight muscles but with fully developed wings (LW_h). The LW_f morph differed genetically from the SW morph and phenotypically from the LW_h morph in the size of flight muscles, ovarian growth during the first week of adulthood, and the hemolymph titer of juvenile hormone (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 LW_f morph but did not change significantly during this time in either flightless morph. Prolonged elevation of the in vivo JH titer 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 morph may be a mechanism that allows JH to positively regulate nocturnal flight behavior, while not causing maladaptive histolysis of flight muscles and ovarian growth. This is the first demonstration of naturally occurring, genetically based variation for diurnal change in a hormone titer in any organism.