Abstract
Marine heatwaves (MHWs) are projected to increase in intensity and frequency over the coming decades, and it is imperative to assess the adaptive capacity of marine organisms to these extreme temperature events. Given the nature of MHWs to last days to weeks in a region, these events may have overarching impacts on phenological events like reproduction and development. Here, the role of adult thermal history and transgenerational plasticity may be an important pathway by which MHWs are transduced to impact community structure. In this study, we sought to explore the effects of paternal thermal history in the purple urchin, Strongylocentrotus purpuratus, on a crucial aspect of reproduction, fertilization. Using ecologically relevant temperatures representative of both MHW events that occurred in 2014–2020 and non-MHW temperatures in our region of the California Large Marine Ecosystem, we conditioned male S. purpuratus for 28 days to either a high, MHW or a low, non-MHW temperature. Following the temperature acclimation of adults, sperm performance was tested for individual males by conducting fertilization success trials at varying temperatures and sperm concentrations. While sperm appeared robust to elevated temperature during fertilization, sperm produced by high-temperature-acclimated males had overall diminished performance as compared to those acclimated to non-MHW temperatures. These results suggest MHW events will have a negative impact on fertilization in situ for S. purpuratus populations. Furthermore, these results highlight the importance of considering both male and female environmental history in projections of reproduction under climate change scenarios.
Highlights
Understanding the adaptive capacity of species in response to climate change is a major research and conservation goal (Ofori et al 2017; Thurman et al 2020)
We examined the fertilization success of the purple sea urchin, Strongylocentrotus purpuratus, under the elevated temperatures associated with marine heatwave (MHW) scenarios
In examining the role of paternal thermal history on fertilization dynamics under these temperatures, we discovered two central findings: (1) the temperature at which fertilization occurred had no significant effect on fertilization itself, and (2) paternal exposure to a MHW-like temperature had a negative impact on fertilization success as compared to the non-MHW treatment
Summary
Understanding the adaptive capacity of species in response to climate change is a major research and conservation goal (Ofori et al 2017; Thurman et al 2020). For organisms not as reliant on migration and dispersal in response to unfavorable climatic conditions, adaptive capacity can be thought of as having two elements: micro-evolutionary processes (where genetic changes occur in response to selection in the environment) and phenotypic plasticity Since phenotypic plasticity may act more rapidly, and on ecological time scales, this class of mechanisms might allow species to cope with environmental change in situ (Fox et al 2019). We explore gamete plasticity and its effects on the fertilization process in the context of extreme heat stress that occurs during episodic marine heatwaves (MHWs), asking if paternal experience contributes to the generation of gametes more resistant to the thermal conditions of MHWs
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