Climate Change effects on the developmental physiology of the small-spotted catshark (Scyliorhinus canicula)

Elasmobranchs (sharks and rays) are important components of marine ecosystems worldwide but are poorly studied compared to many teleost species. Effects of climate change on elasmobranchs are still poorly understand, but their low fecundity and relatively long embryonic development stage could make elasmobranchs particularly vulnerable to some climate change effects. Ocean acidification (OA) has been shown to increase mortality and induce developmental defects in early juvenile teleosts, e.g. (Stiasny et al., 2019), but comparative data on elasmobranchs are lacking as laboratory experiments are relatively difficult. Elasmobranch physiology, reproductive style, blood chemistry and respiratory anatomy all differ markedly from teleosts, so that experimental results from teleosts cannot be assumed to apply. Limited studies to date give contrasting views on the sensitivity of shark developmental physiology to OA, e.g. (Green and Jutfelt, 2014), but very little work has been done, and we have essentially no experimental basis to predict how resilient early development of elasmobranchs is to climate change effects. This project therefore aims to explore the long-term effects of OA and potentially other climate drivers on the early development of sharks, in particular the development of gills and the skeletal structures, which Stiasny et al. (2019) showed to be affected in cod.
The small-spotted catshark (Scyliorhinus canicula) is an ideal study organism to explore OA effects on developmental physiology, as it is a small-bodied species and oviparous, i.e. it lays eggs, which can easily be studied in a laboratory setting, resulting in a high chance of successful experiments.
This project will be based on experiments in which small-spotted catshark eggs and juveniles will be exposed to ocean acidification and a control as well as different temperatures throughout their development. S. canicula is abundant both in aquaria and in local waters. We will sample egg cases from both aquarium and wild settings.
Response variables will include fundamental fitness proxies such as survival, somatic growth rate and energy metabolism. In addition, we will measure blood chemistry, especially blood carbonate chemistry including stable isotope approaches, size of the gills and condition of skeletal structures. Specimens will be cleared and double stained (Schnell, Konstantinidis and Johnson, 2016) in order to investigate their skeletal development and detect retardation or acceleration in the ossification process of e.g. the vertebral column or the gill arches as well as deformations. Depending on the interests of the student, the project may include studies of the effects of OA and developmental temperature on gene expression, biomineralisation and/or behaviour.