SREL Reprint #2125
Courtship Behavior and Plasma Levels of Androgens and Corticosterone in Male Marbled Salamanders, Ambystoma opacum (Ambystomatidae)
Lynne D. Houck,1 Mary T. Mendonca,2 Tracy K. Lynch,3 and David E. Scott3
1Department of Ecology and Evolution,
University of Chicago, 940 E. 57th Street, Chicago, Illinois 60637
2Department of Zoology and Wildlife,
Auburn University, Auburn, Alabama 36849
3Savannah River Ecology Laboratory,
Drawer E, Aiken, South Carolina 29802
We measured plasma levels of testosterone, dihydrotes- response (three species
of toads in the genus Bufo) and tosterone (DHT), and corticosterone for male
marbled salamanders (Ambystoma opacum) collected during the breeding
season. Our goal was to ascertain whether steroid levels changed in response to
particular reproductive behaviors or laboratory confinement. Six groups of
salamanders were examined: (a) MIGRATING, males migrating toward the pond
basin during the breeding season; (b) LABORATORY, males kept under
confined conditions in the laboratory for 10 days; (c) LAB-FIELD, laboratory
males that were later released into seminatural enclosures in the field; (d)
COURTING, males from male-female pairs in which the male actively courted the
female (and deposited at least one spermatophore); (e) SOLO, males that were
individually isolated from conspecifics; and (f) MALE-MALE, males that were
placed together in pairs, and in which one male actively courted the other male. In
three groups (COURTING, SOLO, and MALE-MALE), salamanders were
placed in containers for observation and each male was observed for at least 2 hr
prior to a plasma sample being taken. Circulating levels of testosterone, DHT, and
corticosterone did not differ significantly for males in these groups. The similarity
of androgen levels among the three groups indicated a lack of behaviorally evoked
change under experimental conditions designed to reveal a behaviorandrogen
response. Male A. opacum differ taxonomically from other amphibians showing a
behavior-androgen response (three species of toads in the genus Bufo) and also
lack amplexus and male-male combat during competition for mates. The effect of
confinement were indicated by levels of testosterone and DHT in
LABORATORY males that in the following groups: MIGRATING, LAB-FIELD,
and MALE-MALE. We inferred that LABFIELD males, following their release to
seminatural enclosures, were able to regain plasma androgem levels typical of
migrating males. This increase is one of very few demonstrations for amphibians of
an increase in androgen levels upon release from laboratory confinement. Levels
of corticosterone did not differ significantly between males that were active in the
field and males that were kept in the laboratory. The similarity of corticosterone
levels among these groups differs from the typical pattern of elevated
corticosterone and depressed androgen levels in captive amphibians. Maximal
corticosterone levels in breeding male A. opacum may act differently than in other
species in which chronic elevations inhibit the pituitary-gonadal axis.
SREL Reprint #2125
Houck, L.D., M.T. Mendonca, T.K. Lynch, and D.E. Scott. 1996. Courtship behavior and plasma levels of androgens and corticosterone in male marbled salamanders, Ambystoma opacum (Ambystomatidae). General and Comparative Endocrinology 104:243-252.
