Coral Larvae Every Day: Leptastrea purpurea, a Brooding Species That Could Accelerate Coral Research

Abstract

Sexually produced larvae are used in various fields of coral research. Because the vast majority of scleractinians reproduces only on one or few occasions per year through simultaneous release of gametes, and because an ex situ spawning induction is still very hard to achieve, great efforts are required to obtain planula larvae. Brooding corals have been used to harvest planulae although their larvae often differ in various traits from most spawning corals, e.g., in settlement behavior. Other cnidarians, such as Aiptasia spp., have been substituting for scleractinians in many aspects of coral research. However, organisms such as Aiptasia differ strongly from scleractinians, thus limiting the transferability of obtained results. This study examines the potential of Leptastrea purpurea as a reliable source of larvae for coral research. Larval output as well as settlement behavior of planulae was investigated. Our results show that colonies of L. purpurea released a daily average of 3.7 (±0.2) larvae during a period of 65 days, thus allowing continual access to planula larvae. We collected a total of 58127 larvae from our broodstock of 243 colonies. Larval settlement is induced by the same and/or similar cues as in many spawning species which increases the transferability of conclusions. We discuss the utility of L. purpurea for research on scleractinian physiology, ecology and larval settlement and conclude that L. purpurea is a well-suited organism to accelerate progress in many fields of coral research.

Neuroactive compounds induce larval settlement in the scleractinian coral Leptastrea purpurea

“…88 and Nietzer et al . 89 . In short: The corals were placed in 30 L plastic containers (30 colonies per container) with aeration but no flow-through overnight.…”

Sexual production of corals for reef restoration in the Anthropocene

“…However, multiple gametogenic cycles per year have been described in some coral populations (e.g. Stobart et al 1992, Penland et al 2004, Mangubhai & Harrison 2008a, and many brooding species have several overlapping gametogenic cycles each year (Kojis 1986, Szmant 1986, Harrison & Wallace 1990, Foster & Gilmour 2018, with some releasing larvae on a daily basis (Nietzer et al 2018).…”

“…Within seasons, spawning is correlated with the lunar cycle and is likely cued directly by moonlight detected through photoreceptors (possibly cryptochromes or opsins, see Hoadley et al 2016) that sense moonlight intensity (Levy et al 2007, Kaniewska et al 2015, but see Linden et al 2018. Some brooding species may use similar processes to coordinate planulae release, whereas other brooders do not exhibit lunar periodicity in planulation (Jokiel et al 1985, Vermeij et al 2003, Zakai et al 2006, Linden et al 2018, Nietzer et al 2018. No data are available on photosensitivity of cnidarian cryptochromes; however, they may form part of the circadian clock rather than serve as photosensors (Hoadley et al 2016).…”

Photosensitivity of the Bacterial Pigment Cycloprodigiosin Enables Settlement in Coral Larvae—Light as an Understudied Environmental Factor

“…Since larvae of L. purpurea range up to 1 mm in length, no magnification was needed for collection. As stated in Nietzer et al (2018), L. purpurea planulae produce a green fluorescent protein (GFP), which enables convenient collection of larvae by using fluorescent blue light (460-480 nm wavelengths) and a yellow barrier filter. Thus, the coral larvae appear in a greenish color and can be better differentiated from other abiotic and biotic matter.…”

“…In this study, larval attachment and metamorphosis were investigated in response to a combination of different bacteria-derived compounds and light regimes (i.e., light, darkness and its combinations). In continuation of our research interest into the settlement process of stony corals (Kitamura et al, 2009;Maru et al, 2013;Nietzer et al, 2018;Moeller et al, 2019;Petersen et al, 2021), we used the brooding scleractinian coral L. purpurea that is known to release larvae on a daily basis (Nietzer et al, 2018). Among 56 isolated bacterial strains [derived from the tropical CCA Hydrolithon reinboldii; (Petersen et al, 2021)] only the ethanol crude extract of the highly pigmented Pseudoalteromonas rubra strain #1783 showed promising results with settlement of L. purpurea larvae.…”