Transgenerational Plasticity (TGP) in polar invertebrates as a mechanism of adapting to a warmer more acidic coastal Antarctic
Quantifying the functional responses of Antarctic marine species to future ocean acidification and ocean warming is critical to assess the outcomes of climate change on Antarctica, and the wider effects on Earth eco-systems. How polar species respond to climate change is dictated by their capacity to acclimate (phenotypic plasticity) and adapt (genetic mechanisms). Transgenerational Plasticity (TGP), where offspring phenotype reflects parental experiences and hence fitness to a changing environment, is a particularly important mechanism available for species to immediately respond to environmental change as the physiological history of the parents provides a protective buffer to the resulting offspring, to environmental stressors. This facilitates an effective survival response that ‘buys’ time for species to respond to selection in the longer-term through genetic adaptive evolution. Thus far the importance of TGP in marine species has been shown in only a few species, with only one study on an Antarctic species, Sterechinus neumayeri in response to warming and acidification. Our research question is:
To what degree can TGP in a polar marine species, Odontaster validus promote adaptation to rapid ocean change in response to two co-occurring environmental stressors (temperature, ocean acidification) and in low or high food condition, and what are the key underlying mechanisms of TGP?
The outcomes of our project will indicate whether TGP in polar species may be effective at outpacing the direct effects of climate change in the Antarctic region. TGP can be achieved through two processes (Ross et al., in press): (1) a maternal investment in the eggs to make them more resilient to environmental change (i.e. adding protective proteins such as HsP, nutrients), and 2; by altering the pattern of gene expression in offspring through epigenetics (i.e. DNA methylation). Transgenerational experiments need to be relatively long-term, requiring that the adults be exposed to environmental change for a period long enough to provide the potential for TGP (i.e. across an entire breeding cycle). For Antarctic invertebrates, this requires at least 12 months. We will undertake a long-term experiment (18 mo) to assess TGP in the Antarctic seastar Odontaster validus Koehler 1906. Odontaster is an ideal model species to examine TGP; its reproduction and larval development are known and it has been successfully maintained in captivity in a special facility at the University of Otago with demonstrated success in using brood stock for breeding experiments over a number of years. The facility uses closed circulatory systems (an essential trait for conducting long-term experiments where conditions need to be closely controlled). We will expose adult Odontaster to a future climate change scenario (IPCC 2014, elevated temperature (ambient, +3°C) and reduced pH (ambient, -0.4 pH units)) across two food levels and allow adults to respond, reproduce and for their larval offspring to develop in treatment conditions. This is required to determine if there is an effect of parental history on offspring performance. Adult fitness and the degree of acclimation to environmental conditions will be quantified during the 18 mo exposure (expressed as a dynamic energy budget model incorporating growth, calcification, respiration, excretion, reproductive output). After 18 months, TGP will be quantified through an examination of (1) gamete quality and performance under elevated temperature and reduced pH, (2) fitness of embryos and larval stages to elevated temperature and reduced pH, and (3) epigenetic responses (differential gene expression). The degree of correlation between adult exposure and offspring performance will provide a quantitative measure for potential adaptation through TGP. The underlying epigenetic responses associated with TGP will be investigated through changes in egg quality and gene expression (DNA methylation patterns). Our investigation of the potential for adaptation through TGP meets NZARI white paper (2013) aspirations: (i) an knowledge of TGP will increase our fundamental understanding of how Antarctic ecosystems will respond to change; (ii) know the degree that TGP can keep pace with rates of warming and acidification will help identifying thresholds of response, and contribute to the process of reducing uncertainties around thresholds of response in Antarctic ecosystems. (i.e. the degree that adaptive capacity will overcome change). We hypothesise that our research may conclude:
‘Polar species respond to climate change by producing more robust offspring’
In this audio you can listen to PIs Miles Lamare (University of Otago) and Antonio Agüera (ULB) explaining the aims of this project in a radio interview at RadioNZ: Winners or losers? Antarctic starfish and climate change
Prof. Miles Lamare (University of Otago), Lead Principal Investigator
Dr. Antonio Agüera and Prof. Bruno Danis (ULB), co-PI
Prof. Mary Sewell (University of Auckland), co-PI
Prof. Maria Byrne (University of Sydney), Associate Investigator
Prof. Adam Marsh (University of Delaware), AI
Dr. Victoria Metcalf (National Coordinator of the Participatory Science Platform, New Zealand).