Red‐eared slider hatchlings (Trachemys scripta) show a seasonal shift in behavioral types

• Published in: Journal of experimental zoology. Part A, Ecological and integrative physiology Ecological and integrative physiology, 2019-11, Vol.331 (9), p.485-493
• Main Authors: Nichols, Haley, Carter, Amanda W., Paitz, Ryan T., Bowden, Rachel M.
• Format: Article
• Language: English
• Subjects: behavioral types; estrogen; maternal effects; season; Trachemys scripta; yolk
• ISSN: 2471-5638; 2471-5646
• DOI: 10.1002/jez.2315

Correlated and repeatable patterns of behavior, termed behavioral types, can affect individual fitness. The most advantageous behavioral type may differ across predictable environments (e.g., seasonally), and maternally mediated effects may match hatchling behavior to the environment. We measured righting response, an indicator of behavioral type, of juvenile red‐eared slider turtles (Trachemys scripta) emerging from early and late season clutches to understand if the production of behavioral types differs across the nesting season. There was a significant effect of season, with early season hatchlings righting more quickly than late season hatchlings, and we explored two potential underlying mechanisms, maternal estrogens and maternal investment (e.g., yolk allocation). We dosed early season eggs with an estrogen mixture to mimic late season eggs and assayed hatchling righting response, but found no significant effect of this maternal effect. We assessed maternal investment by measuring egg, hatchling, and residual yolk masses. We found a seasonal pattern in yolk allocation, where early season eggs have more yolk than late season eggs. Early season hatchlings used more yolk for growth rather than maintenance of existing tissues, resulting in larger hatchlings. Interestingly, across both seasons, hatchlings that received less maternal yolk appeared to be more efficient at converting yolk to tissue, but we found no direct correlation with righting behavior. We demonstrate that the prevalence of behavioral types varies across the nesting season, creating correlated suites of seasonal phenotypes in turtle hatchlings, but it appears that neither maternal estrogens or investment in yolk directly underlie this shift in behavior. Cumulative (2014–2016) average righting response times (in seconds) significantly differ between early (dark grey bar) and late (light grey bar) season hatchlings. Plotted are least squared means ± 1 SE. RESEARCH HIGHLIGHTS Behavioral types vary between Trachemys scripta hatchlings from early or late season clutches. Early season hatchlings receive more yolk and utilize yolk differently than late season hatchlings. Though seasonal shifts in behavioral type are not mediated by maternal estrogens or yolk allocation, clear seasonal differences in suites of phenotypic traits continue to emerge.