Abstract
The uptake of anthropogenic CO2 emissions by oceans has started decreasing pH and carbonate ion concentrations of seawater, a process called ocean acidification (OA). Occurring over centuries and many generations, evolutionary adaptation and epigenetic transfer will change species responses to OA over time. Trans-generational responses, via genetic selection or trans-generational phenotypic plasticity, differ depending on species and exposure time as well as differences between individuals such as gender. Males and females differ in reproductive investment and egg producing females may have less energy available for OA stress responses. By crossing eggs and sperm from the calcareous tubeworm Hydroides elegans (Haswell, 1883) raised in ambient (8.1) and low (7.8) pH environments, we observed that paternal and maternal low pH experience had opposite and additive effects on offspring. For example, when compared to offspring with both parents from ambient pH, growth rates of offspring of fathers or mothers raised in low pH were higher or lower respectively, but there was no difference when both parents were from low pH. Gender differences may result in different selection pressures for each gender. This may result in overestimates of species tolerance and missed opportunities of potentially insightful comparisons between individuals of the same species.
Highlights
Larvae from wild adults were divided among two pH environments and raised to maturity (i.e. F0). (3) Gametes from F0 females and males of both pH environments were collected and fertilized in all possible combinations, creating 4 groups. (4) Each of the groups (F1 generation) were divided among high and low pH environments and larval metamorphosis, juvenile growth and juvenile survival were measured (4 F1 groups × 2 pH environments × 6 replicates = 4 8 total F1 culture tanks)
We tested the effects of and interactions between the pH environment experienced by the parents, parental gender, and the pH experienced by the offspring (F1 generation, experimental design summarized in Fig. 1) on F1 generation performances
We hypothesized that (i) offspring exposed to the same pH condition as that experienced by their parents will perform relatively better than those exposed to a different pH environment and (ii), because females may be more strongly affected by low pH conditions, possibly due to a tighter energy budget, they may experience stronger selection pressure or be less able to pass on positive trans-generational phenotypic changes
Summary
Trans-generational responses (i.e. TPP and/or genetic selection) to OA were examined by exposing both parents and offspring of the biofouling tube worm Hydroides elegans (Haswell, 1883) to two pH environments within their natural range, a high pH (8.1) environment and a low pH (7.8) environment This species is well suited to laboratory experiments due to the ease of culture and relatively short generation times[29] and previous experiments have shown that tube growth and calcification can be affected by low pH conditions[30,31,32]. We hypothesized that (i) offspring exposed to the same pH condition as that experienced by their parents will perform relatively better than those exposed to a different pH environment and (ii), because females may be more strongly affected by low pH conditions, possibly due to a tighter energy budget, they may experience stronger selection pressure or be less able to pass on positive trans-generational phenotypic changes
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