Cardiorespiratory ontogeny and response to environmental hypoxia of larval spiny lobster, Sagmariasus verreauxi

Abstract

Cardiorespiratory function is vital to an organism's ability to respond to environmental stress and analysis of cardiorespiratory capacity of species or life stages can elucidate vulnerability to climate change. Spiny lobsters have one of the most complex pelagic larval life cycles of any invertebrate and recently there has been an unexplained decline in post-larval recruitment for a number of species. We conducted the first analysis of the larval ontogeny of oxygen consumption, heart rate, maxilla 2 ventilation rate and oxyregulatory capacity of the spiny lobster, Sagmariasus verreauxi, to gain insight into their vulnerability to ocean change and to investigate life stage specific sensitivity to temperature-dependent oxygen limitation. In normoxia, heart and maxilla 2 ventilation rates increased in early larval development before declining, which we hypothesise is related to the transition from myogenic to neurogenic cardiac control. Maxilla 2 ventilation rate was sensitive to hypoxia at all larval stages, while heart rate was only sensitive to hypoxia in the late phyllosoma stages. Oxygen consumption conformed to environmental hypoxia at all larval stages. Spiny lobster larvae have limited respiratory control due to immature gas exchange physiology, compounded by their exceptionally large size. The lack of oxyregulatory ability suggests that all development stages are vulnerable to changes in sea temperature and oxygen availability. The synergetic stressors of increased temperature and reduced dissolved oxygen in the marine environment will diminish spiny lobster larval performance, increasing the challenge to achieve their extended larval life cycle, which may contribute to declines in post-larval recruitment.