Morphology and cardiac physiology are differentially affected by temperature in developing larvae of the marine fish mahi-mahi (Coryphaena hippurus)

Abstract

Cardiovascular performance is altered by temperature in larval fishes, but how acute versus chronic temperature exposures independently affect cardiac morphology and physiology in the growing larva is poorly understood. Consequently, we investigated the influence of water temperature on cardiac plasticity in developing mahi-mahi. Morphological (e.g. standard length, heart angle) and physiological cardiac variables (e.g. heart rate fH, stroke volume, cardiac output) were recorded under two conditions by imaging: (i) under acute temperature exposure where embryos were reared at 25°C up to 128 h post-fertilization (hpf) and then acutely exposed to 25 (rearing temperature), 27 and 30°C; and (ii) at two rearing (chronic) temperatures of 26 and 30°C and performed at 32 and 56 hpf. Chronic elevated temperature improved developmental time in mahi-mahi. Heart rates were 1.2–1.4-fold higher under exposure of elevated acute temperatures across development (Q10≥2.0). Q10 for heart rate in acute exposure was 1.8-fold higher compared to chronic exposure at 56 hpf. At same stage, stroke volume was temperature independent (Q10∼1.0). However, larvae displayed higher stroke volume later in stage. Cardiac output in developing mahi-mahi is mainly dictated by chronotropic rather than inotropic modulation, is differentially affected by temperature during development and is not linked to metabolic changes.

Mahi‐mahi (Coryphaena hippurus) life development: morphological, physiological, behavioral and molecular phenotypes

“…Regular heart rate (120‐130 beats/minute −1 ) is established by 26 hpf in mahi, whereas heart chambers are discernable but not yet delineated. Heart rate frequency then increases with further development . Urea transporter gene expression peaks around 36 hpf .…”

“…Heart rate frequency then increases with further development. 11,12 Urea transporter gene expression peaks around 36 hpf. 42 Erythropoiesis is initiated from transparent circulating blood cells, and circulation in the central vasculature appears as a modest flow during hatching (43 hpf) (SL = 3.9-4.0 mm).…”

“…Aside from the interest in this species from a food‐fish perspective, mahi has been identified as a promising candidate for research investigations. Indeed, during the last few decades, mahi has become an emergent model for examining population genetics, developmental physiology, metabolic responses, nutritional physiology, egg and larval performance over time, and climate change effects . Mahi have also been studied extensively regarding the impact of environmental toxicants .…”

Developmental changes in oxygen consumption and hypoxia tolerance in the heat and hypoxia‐adapted tabasco line of the Nile tilapia Oreochromis niloticus, with a survey of the metabolic literature for the genus Oreochromis

“…1.5 to 2.1. These values fall in the range of Q 10 s of 1.5–3, typical for both freshwater and marine larval, juvenile and adult teleost fishes (Aboagye & Allen, ; Aguilar et al, ; Chen et al, ; Peck & Moyano, ; Perrichon et al, ; Tirsgaard et al, ). These data suggest no extraordinary temperature sensitivity in juvenile and adult O. niloticus…”

Developmental phenotypic plasticity helps bridge stochastic weather events associated with climate change

“…However, an informal PubMed search revealed that studies of climate change and phenotypic plasticity ( presumably in mature forms for lack of mention otherwise) outnumber similar papers that specifically mention 'embryos', 'larvae' or 'seedlings' by approximately 10 to 1. Yet, we know that developing organisms can be as, or more, susceptible than adult animals and plants to predictable or unpredictable changes in the environment (Burggren et al, 2017;Byrne et al, 2013;Croteau et al, 2008;Esbaugh et al, 2016;Kingsolver et al, 2011;Mueller et al, 2015;Müller and Rieu, 2016;Perrichon et al, 2017;Przeslawski et al, 2015;Radchuk et al, 2013;Reyna and Burggren, 2017).…”