Temperature effects on the development and metamorphosis of larvae of broadcast spawning coral species from Japan and the Great Barrier Reef

Full description

In August 2004, an experiment was conducted to test the effects of temperature on larval development and metamorphosis for the solitary coral, Fungia repanda, collected from a patch reef slope in northern Okinawa, Japan. Three hours after fertilisation, the embryos from a single male and female colony cross were transferred into triplicate 2 litre plastic beakers, maintained in incubators set at 26, 28 and 30°C (±0.5°C).Larvae were sampled from each beaker on days 3 and 4 post-spawning and transferred to six-well cell culture plates (8-12 larvae per well, n = 3 wells) containing 10 ml of 1 µm filtered sea water (FSW) and a small (<5 mm) chip of unidentified crustose coralline algae (CCA) to initiate metamorphosis. Culture wells containing coral larvae and CCA were maintained at the same temperatures as the larval cultures (±0.3°C). The percentage of larvae undergoing early metamorphosis was assessed at 12 h.In November 2007, a second experiment tested the effects of temperature on larval development and metamorphosis of Acropora millepora, Acropora spathulata and Symphyllia recta from Viper Reef on the Great Barrier Reef. Acropora millepora was sampled from the reef slope, while the other two species were collected from the upper reef flat. Three hours after fertilisation, 400 embryos from at least three colonies were transferred into three separate 1 litre polycarbonate bottles containing 700 ml FSW. The bottles containing the embryos were floated in triplicate computer-controlled flow-through aquaria at 26, 28, 30 and 32°C (±0.3°C) and 80 µmol quanta/m²/s (12:12 h light:dark cycle).Each day larvae were transferred from the floating containers into six-well plates (10-15 per well) containing 10 ml FSW. In total, 9 wells were used for each temperature treatment each day (3 wells of larvae from each water bath x 3 water baths for each temperature). A 5 mm x 5 mm x 3 mm chip of the CCA Neogoniolithon fosliei was added to each well to induce metamorphosis. The larvae were then transferred into incubators set to 26, 28, 30 and 32°C (±0.3°C). Early metamorphosis was assessed after 18 h.Larvae of Acropora millepora, Acropora spathulata and Symphyllia recta were also mass cultured at 28°C in 500 litre indoor flow-through aquaria 80 µmol quanta/m²/s (12:12 h light:dark cycle), to investigate the possible effects of temperature on metamorphosis (not development). Each day larvae were transferred from the cultures into six-well cell culture plates (10-15 larvae per well, n = 3 wells) containing 10 ml FSW. The larvae were then transferred into incubators set to 26, 28, 30 and 32°C (±0.3°C) and early metamorphosis assessed following the addition of small CCA chips.
Laboratory experiments were conducted to determine the effects of temperature on the rate of attaining competence to settle and metamorphosis in azooxanthellate larvae of reef-building coral species.

Lineage

Maintenance and Update Frequency: notPlanned

Statement: Statement: The gametes of each species were fertilised according to the methods described in: Heyward AJ and Negri AP (1999) Natural inducers for coral larval metamorphosis. Coral Reefs 18:273-279.This paper also describes the method used to induce metamorphosis.Metamorphosis was defined as the initiation of deposition of the basal plate, which is clearly visible through the juvenile coral tissue within 12 h of settlement. See: Babcock RC, Baird AH, Piromvaragorn S, Thomson DP and Willis BL (2003) Identification of scleractinian coral recruits from Indo-Pacific reefs. Zool Stud 42:211-226.A temperature gradient was established using a 4-mm thick aluminium sheet set on a lab bench in a room maintained at 24°C, with a thermostatically controlled heating pad underneath one end set at 32°C. Culture wells containing coral larvae and CCA were positioned on the sheet to achieve temperatures within the wells identical to those of the larval cultures (±0.3°C, measured periodically with a precision thermometer).Mass culture of larvae was carried out using methods described in:Negri AP, Heyward AJ (2000) Inhibition of fertilization and larval metamorphosis of the coral Acropora millepora (Ehrenberg, 1834) by petroleum products. Mar Pollut Bull 41:420-427.

Notes

Credit
Heyward, Andrew J, Dr (Principal Investigator)