Oxygen consumption of a single embryo/planula in the reef-building coral Acropora intermedia

Abstract

O 2 consumption of a single embryo/planula at each developmental stage was monitored in the reef-building coral Acropora intermedia using an optical O 2 -sensing system with our original micro-chamber system (6.28 µl). The lowest rate of O 2 consumption was observed in unfertilized eggs. After fertilization, O 2 consumption increased and remained constant until the prawn chip blastula stage. However, O 2 consumption began to increase again during the bowl-shaped blastula stage, which involves the formation of 2 germ layers and corresponds to the beginning of gastrulation. The rate of O 2 consumption peaked during the teardrop-shaped planula stage. During this stage planulae are able to swim actively, especially in the vertical plane, so an increase in energy consumption during this stage is to be expected. O 2 consumption began to decrease gradually 5 d after spawning. At this stage, the larvae frequently touched the substrate with their concave aboral end, which features numerous spirocysts required for substrate attachment. When the planulae began to settle, 7 d after spawning, the rate of O 2 consumption dropped to that of unfertilized eggs, suggesting that the planulae slowly use stored energy for crawling/settlement behavior and/or post-settlement growth and survivorship.KEY WORDS: Development · Dispersal · Energy · Larva · Lecithotrophic · Metabolism · Recruitment · Settlement-competency period Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 366: [305][306][307][308][309] 2008 developmental stage is an important index for understanding larval dispersal and recruitment; such data indicate when the larvae use energy and how they allocate the maternally derived energy for dispersal potential, larval fitness, and post-settlement growth and survival (Richmond 1987, Hoegh-Guldberg & Manahan 1995.A number of studies have examined the energetics of the development of planktotrophic and lecithotrophic species of sea urchin and abalone (Crisp et al. 1985, Marsh et al. 1999, Bryan 2004. However, the most common method of measuring O 2 consumption (i.e. an electrode) is unsuitable for small chamber volumes because the sensor itself consumes dissolved O 2 to measure the density of O 2 (Clark 1956). In addition, because numerous embryos or planulae compete with each other to consume excess energy in the chamber, the O 2 consumption rate per embryo or planula derived from this method is not reliable for analyzing the transitions between developmental stages. Here, we present data for O 2 consumption of a single coral embryo/planula at each developmental stage using an optical O 2 -sensing system. This system has several advantages: no O 2 consumption, no membrane or electrolytes required (i.e. easy maintenance), high sensitivity and stability, and an adequate chamber volume (Nakaya et al. 2003(Nakaya et al. , 2005. No previous data are available for O 2 consumption in coral embryos or planulae using the technique described here. MATERIALS AND METHODSWe collecte...

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