Gill function & vertebrate evolution

The gills play many important roles in vertebrate evolution by serving as the primary site for breathing and ion regulation. These two gill functions have long been hypothesized to first originate in stem vertebrates, facilitating the transition from small, worm-like creatures to larger, active fishes. However, this hypothesis lacks functional support. My PhD addressed this knowledge gap by characterizing gill function in vertebrates, cephalochordates and hemichordates. We found support for a vertebrate origin of breathing at gills that is associated with increasing body size and activity, but an unexpected and earlier deuterostome origin for ion regulation at gills. These findings are an essential functional complement to existing views on the origin of breathing at gills, but they challenge our understanding of how ion regulation evolved.

relevant publications

• Sackville MA, Cameron CB, Gillis JA and Brauner CJ. Ion regulation at gills precedes gas exchange and the origin of vertebrates. Nature (2022).

press

• BBC Radio's Science in Action - Episode 20/10/2022

• Nature News & Views

• Journal of Experimental Biology

• UBC Science

Wild salmon & sea lice

My MSc work was part of a collaborative effort between academia, industry and government to promote the sustainable coexistence of wild and farmed salmon in the coastal waters of British Columbia. Our team’s goal was to quantify the sublethal impacts of sea louse parasitism on the performance of out-migrating wild juvenile pink salmon. Juvenile pink salmon were thought to be especially vulnerable to parasitism because they enter seawater immediately following embryonic development at very small body sizes (~25 mm). By measuring fish growth, swim performance and ionoregulatory status, this work significantly advanced our understanding of how pink salmon accomplish their remarkably early ocean migration, and identified a critical window in which they are especially vulnerable to sea lice. Our findings directly influenced industry practices, resulting in the movement of active fish farms away from the pink salmon migratory route during this critical window.

relevant publications

• Sackville MA, Wilson JM, Farrell AP and Brauner CJ. Water balance trumps ion balance for early marine survival of juvenile pink salmon. Journal of Comparative Physiology B (2012).

• Brauner CJ, Sackville MA, Gallagher Z, Tang S, Nendick L and Farrell AP. Physiological consequences of the salmon louse on juvenile pink salmon: implications for wild salmon ecology and management, and for salmon aquaculture. Philosophical Transactions of the Royal Society B (2012).

• Tang S, Lewis AG, Sackville MA, Nendick L, DiBacco C, Brauner CJ and Farrell AP. Diel vertical distribution of early marine phase juvenile pink salmon and behaviour when exposed to salmon louse. Canadian Journal of Zoology (2011).

• Sackville MA, Tang S, Nendick L, Farrell AP and Brauner CJ. Pink salmon osmoregulatory development plays a key role in sea louse tolerance. Canadian Journal of Fisheries and Aquatic Sciences (2011).

• Nendick L, Sackville MA, Tang S, Brauner CJ and Farrell AP. Sea lice infection of juvenile pink salmon: effects on swimming performance and postexercise ion balance. Canadian Journal of Fisheries and Aquatic Sciences (2011).

• Nendick L, Grant A, Gardner M, Sackville MA, Brauner CJ and Farrell AP. Swimming performance and associated ionic disturbance of juvenile pink salmon determined using different acceleration profiles. Journal of Fish Biology (2009).

• Grant A, Gardner M, Nendick L, Sackville MA, Farrell AP and Brauner CJ. Growth and ionoregulatory ontogeny of wild and hatchery-raised juvenile pink salmon. Canadian Journal of Zoology (2009).