TY - JOUR
T1 - Growth and behavior of thyroid-deficient lizards (Sceloporus undulatus)
AU - Gerwien, Robert W.
AU - John-Alder, Henry B.
N1 - Funding Information:
We thank A. O’Connell, D. Sheely, and P. Sullivarr for help in constructing the enclosure. J. Brmrad, A. Finneti, S. McMann, and P. Sullivan aided,in ‘the sap- ture of lizards. S. McMann and V. Pierce provided useful criticisms of earlier drafts of the manuscript. We also thank Ray Huey and an anonymous reviewer for helpful comments. This work was supported by grants from NSF (DCB 87-02490), from the Busch Memorial Fund (administered by the Bureau of Biological Research), and the Carl N. Steinetz Memorial Fund, both of Rutgers University.
PY - 1992/8
Y1 - 1992/8
N2 - This study investigates thyroid control of growth and energy metabolism plus growth-dependent and growth-independent behavioral effects of thyroid manipulation in lizards. Experiments were done on surgically thyroidectomized (Tx) and sham-operated (Sh) year-ling Sceloporus undulatus enclosed in their natural habitat. Lizards were placed in an outdoor enclosure in early August. Growth rate was measured and behavior was observed until mid-October. Subsequently, lizards were returned to the lab for measurements of plasma thyroxine (T4), standard metabolic rate (SMR), and running endurance. Thyroidectomy reduced plasma T4 from 4.3±0.56 ng/ml to undetectable levels (P = 0.006) and SMR by 44% (P < 0.0001). Thyroid deficiency produced a threefold reduction in growth rate (Tx: 0.04±0.010 mm/day, n = 12 vs Sh: 0.11 ± 0.006 mm/day, n = 11, P <0.0001). Growth rate was correlated with SMR among individuals (length-specific: r = 0.55, P = 0.027, n = 16), even after statistical removal of mass and treatment effects. The total volume of oxygen consumed for standard metabolism during the growth period, as estimated from allometric equations, was correlated with cumulative growth (R2 = 0.94, P = 0.013) and was significantly lower for thyroid-deficient lizards than for controls (P < 0.0001). Distance moved in the field and running endurance on a treadmill both scaled on body mass (M0.98 ± 0.418, P = 0.030 and M1.72 ± 0.763, P = 0.040, respectively), indicating that larger lizards moved farther and had greater stamina than their smaller counterparts. Neither of these behavioral factors was affected directly by thyroid status. Thyroid-deficient lizards were active for a smaller percentage of the day than controls (Tx: 42.6 ± 5.7%, n = 11 vs Sh: 57.4 ± 3.2%, n = 12, P = 0.040), independent of differences in body size. On an interindividual basis, the frequency of activity was significantly correlated with SMR (r = 0.57, P = 0.020, n = 16) and growth rate (mass-specific: r = 0.47, P = 0.025, n = 23).
AB - This study investigates thyroid control of growth and energy metabolism plus growth-dependent and growth-independent behavioral effects of thyroid manipulation in lizards. Experiments were done on surgically thyroidectomized (Tx) and sham-operated (Sh) year-ling Sceloporus undulatus enclosed in their natural habitat. Lizards were placed in an outdoor enclosure in early August. Growth rate was measured and behavior was observed until mid-October. Subsequently, lizards were returned to the lab for measurements of plasma thyroxine (T4), standard metabolic rate (SMR), and running endurance. Thyroidectomy reduced plasma T4 from 4.3±0.56 ng/ml to undetectable levels (P = 0.006) and SMR by 44% (P < 0.0001). Thyroid deficiency produced a threefold reduction in growth rate (Tx: 0.04±0.010 mm/day, n = 12 vs Sh: 0.11 ± 0.006 mm/day, n = 11, P <0.0001). Growth rate was correlated with SMR among individuals (length-specific: r = 0.55, P = 0.027, n = 16), even after statistical removal of mass and treatment effects. The total volume of oxygen consumed for standard metabolism during the growth period, as estimated from allometric equations, was correlated with cumulative growth (R2 = 0.94, P = 0.013) and was significantly lower for thyroid-deficient lizards than for controls (P < 0.0001). Distance moved in the field and running endurance on a treadmill both scaled on body mass (M0.98 ± 0.418, P = 0.030 and M1.72 ± 0.763, P = 0.040, respectively), indicating that larger lizards moved farther and had greater stamina than their smaller counterparts. Neither of these behavioral factors was affected directly by thyroid status. Thyroid-deficient lizards were active for a smaller percentage of the day than controls (Tx: 42.6 ± 5.7%, n = 11 vs Sh: 57.4 ± 3.2%, n = 12, P = 0.040), independent of differences in body size. On an interindividual basis, the frequency of activity was significantly correlated with SMR (r = 0.57, P = 0.020, n = 16) and growth rate (mass-specific: r = 0.47, P = 0.025, n = 23).
UR - http://www.scopus.com/inward/record.url?scp=0026667254&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0026667254&partnerID=8YFLogxK
U2 - 10.1016/0016-6480(92)90036-J
DO - 10.1016/0016-6480(92)90036-J
M3 - Article
C2 - 1398024
AN - SCOPUS:0026667254
SN - 0016-6480
VL - 87
SP - 312
EP - 324
JO - General and Comparative Endocrinology
JF - General and Comparative Endocrinology
IS - 2
ER -