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First published online November 30, 2007
Journal of Experimental Biology 210, 4351-4358 (2007)
Published by The Company of Biologists 2007
doi: 10.1242/jeb.009399

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Phenotypic plasticity in female naked mole-rats after removal from reproductive suppression

Christine M. Dengler-Crish^1,* and Kenneth C. Catania²

¹ Neuroscience Graduate Program, Vanderbilt University, Nashville, TN 37235, USA
² Department of Biological Sciences, Vanderbilt University, Nashville, TN 37235, USA

View larger version (15K): [in this window] [in a new window]   Fig. 1. Measurements (twice weekly) of L4 length in cohort CC6. The paired female in this cohort (CC6-587) became pregnant during the 10th week of the study and produced a litter during week 19. The dotted line indicates when the paired female and male were separated from the home colony. Note the increase in L4 length that occurs after colony separation but before pregnancy onset in the paired female.

View larger version (9K): [in this window] [in a new window]   Fig. 2. Standardized measurements of L4 length over the course of the 20-week study. Means (± s.e.m.) for each of the 5-week blocks of the study are plotted on the x-axis. Baseline corresponds to the 5-week period prior to colony separation, and these data have been standardized to zero to show relative gains in L4 between the groups. The dotted line indicates the time of colony separation, and the remaining data blocks correspond to 1–15 weeks after removal from reproductive suppression. Significant differences between the paired females (N=6) and males (N=6) or controls (N=6) are noted with an asterisk (P<0.05). Data from cohorts CC1, CC2, CC9, CC10, CC11 and CC12 are included.

View larger version (9K): [in this window] [in a new window]   Fig. 3. Standardized measurements of total lumbar spine length over the course of the 20-week study. Means (± s.e.m.) for each of the 5-week blocks of the study are plotted on the x-axis. Baseline corresponds to the 5-week period prior to colony separation and these data have been standardized to zero to show relative gains in lumbar spine length between the groups. The dotted line indicates the time of colony separation, and the remaining data blocks correspond to 1–15 weeks after removal from reproductive suppression. Significant differences between the paired females (N=6) and males (N=6) or controls (N=6) are noted with an asterisk (P<0.05). Data from cohorts CC1, CC2, CC9, CC10, CC11 and CC12 are included.

View larger version (8K): [in this window] [in a new window]   Fig. 4. Standardized measurements of body mass over the course of the 20-week study. Means (± s.e.m.) for each of the 5-week blocks of the study are plotted on the x-axis. Baseline corresponds to the 5-week period prior to colony separation and these data have been standardized to zero to show relative gains in weight between the groups. The dotted line indicates the time of colony separation, and the remaining data blocks correspond to 1–15 weeks after removal from reproductive suppression. Significant differences between the paired females (N=6) and males (N=6) or controls (N=6) are noted with an asterisk (P<0.05). Data from cohorts CC1, CC2, CC9, CC10, CC11 and CC12 are included.

View larger version (12K): [in this window] [in a new window]   Fig. 5. L4/ZA index as a control for general growth of the skeleton over time not related to reproduction. Means (± s.e.m.) for each of the 5-week blocks of the 50-week study are plotted on the x-axis. Baseline corresponds to the 5-week period prior to colony separation; the dotted line indicates the time of colony separation, and the remaining data blocks correspond to 1–45 weeks after removal from reproductive suppression. Paired females (N=2) exhibited greater L4/ZA indices over the course of the study than paired males (N=2) or controls (N=2), P<0.01 (as noted by asterisks). Data from cohorts CC1 and CC2 are included.

View larger version (20K): [in this window] [in a new window]   Fig. 6. (A) Measurements of total lumbar length over the course of the 50-week study. Means (± s.e.m.) for each of the 5-week blocks of the study are plotted on the x-axis. Baseline corresponds to the 5-week period prior to colony separation; the dotted line indicates the time of colony separation, and the remaining data blocks correspond to 1-45 weeks after removal from reproductive suppression. Significant differences between the paired females (N=2) and males (N=2) or controls (N=2) are noted with an asterisk (P<0.05). (B) Percent mean gain in total lumbar spine length over the course of the 50-week study. Inset numbers on bars indicate the exact percent gained in lumbar spine from baseline to 45 weeks after colony separation for each of the experimental conditions. Data from cohorts CC1 and CC2 are included.

View larger version (13K): [in this window] [in a new window]   Fig. 7. Growth rate of L4. Mean weekly growth rate for each of the 5-week blocks of the study is plotted on the x-axis. Baseline corresponds to the period prior to colony separation; the dotted line indicates the time of colony separation, and the remaining data blocks correspond to 1–45 weeks after colony separation (N=2 per group).

View larger version (22K): [in this window] [in a new window]   Fig. 8. (A) Measurements of body mass over the course of the 50-week study. Means (± s.e.m.) for each of the 5-week blocks of the study are plotted on the x-axis. Baseline corresponds to the 5-week period prior to colony separation; the dotted line indicates the time of colony separation, and the remaining data blocks correspond to 1–45 weeks after removal from reproductive suppression. Significant differences between the paired females (N=2) and males (N=2) or controls (N=2) are noted with an asterisk (P<0.05). (B) Percent mean weight gain over the course of the 50-week study. Inset numbers on bars indicate the exact percent weight gain from baseline to 45 weeks after colony separation for each of the experimental conditions. Data from CC1 and CC2 are included.

View larger version (13K): [in this window] [in a new window]   Fig. 9. Rate of weight gain. Mean weekly weight gain for each of the 5-week blocks of the study are plotted on the x-axis. Baseline corresponds to the period prior to colony separation; the dotted line indicates the time of colony separation, and the remaining data blocks correspond to 1–45 weeks after colony separation (N=2 per group).

View larger version (25K): [in this window] [in a new window]   Fig. 10. Summary figure of polarized radiographs focused on the spine from one cohort (CC1) of experimental animals. (A) Paired female CC1-633; (B) paired male CC1-893; (C) colony control CC1-3581. In each panel, the first radiograph was taken during the baseline period; the second radiograph was taken at the end of the study (45 weeks after removal from reproductive suppression). The horizontal line in the center of each radiograph is aligned with the top of the vertebral body of L1. The diagram illustrates contrasts in lumbar lengthening from the beginning to the end of the study across experimental groups. The number on the center of the horizontal line indicates the percent of length gained in the lumbar spine by that animal over the duration of the 50-week study. The radiopaque cylindrical objects seen near the cervical spine are identification microchip implants.