Transgenerational plasticity in marine sticklebacks: maternal thermal environment matters most

Transgenerational plasticity is a potentially powerful mechanism for species to cope with rapid environmental change. A few recent studies have shown that these non-genetic parental effects can facilitate acclimation to environmental stressors such as increased temperature and ocean acidification across generations. Yet, the relative contribution of maternal vs. paternal effects is not well understood. In this study, we crossed adult marine sticklebacks held for 2 months at two experimental temperatures (17°C and 21°C) to produce egg clutches in 4 crossing groups: 17mx17f, 17mx21f, 21fx17m, and 21mx21m. Egg clutches were then split and reared at either 17°C or 21°C. In addition to egg number and hatching success, offspring growth rate was measured when fish were 30 and 60 days old. We found that growth rates were highest in offspring reared at the same experimental temperature their mother experienced, and that paternal thermal environment contributed little to offspring growth performance. After 30 days, mean growth rates did not significantly differ between experimental temperatures. However, after 60 days, we saw a marked relative increase in growth for fish reared at 17°C, indicating that the optimal thermal growth threshold for marine sticklebacks lies below 21°C. This pattern also was reflected in hatching success but not in egg number, suggesting that detrimental effects of higher temperatures begin in early developmental stages and persist into later stages, as 21°C offspring showed a lower overall growth trajectory