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Mass spawning in the Faviidae on the Ningaloo Reef Tract

Smith, Rochelle (1993) Mass spawning in the Faviidae on the Ningaloo Reef Tract. Honours thesis, Murdoch University.

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The proportion of colonies of four species of Faviidae, Platygyra daedalea, Goniastria retiformis, Merulina ampliata and Echinopora lamellosa, which spawned over February to May 1993 was determined by repeatedly sampling tagged colonies before and after the predicted full- and new-moon spawning periods at Coral Bay, northwest Australia. Spawning was inferred by the disappearance of gametes in sequential samples.

The major spawning· period in 1993 occurred 7-10 nights after the April fullmoon, with 76.3% of colonies spawning over this period Minor spawning also occurred over the full-moons in February (1.1%), March (10.6%) and May (2.2% ). Minor spawning was also associated with the new-moons in March (2.2%) and April ( 4.4% ). The period of major spawning in April 1993 rather than in March, may be due to the lower than average water temperature that occurred during March 1993, though is more likely due to the early occurrence of the March full-moon.

One solitary colony of G. retiformis contained gametes is early October, 1993. Gametes were not fully mature, suggesting that this colony will spawn in spring 1993. Polyps of P. daedalea, M ampliata, G. retiformis and E. lamellosa contained large numbers of small oocytes. Average mature oocyte volume ranged from 0.013 to 0.035 mm3 and average number of oocytes per polyp ranged from 31.03 to 118.5. Each of the four faviid species contained -significantly different numbers of oocytes per polyp, and also contained oocytes of sigllificantly different volume. Mean oocyte, volume per polyp, which combines number of oocytes per polyp with mean oocyte volume, was used as a measure of reproductive effort. The different faviid species examined in this study' contained significantly different volumes of oocytes per polyp. P. daedalea had the largest oocyte volume per polyp, with a mean volume of 2.0 ± 0.0033 mm3 per polyp. E. lamellosa had a mean oocyte volume per polyp of 1. 7 ± 0.0045 mm3, M. ampliata 1.0 ± 0.0023 mm3 and G. retiformis 0.40 ± 0.0025 mm3 per polyp. Within species of P. daedalea, M ampliata, G. retiformis and E. lamellosa, different polyps, taken from different colonies, contained relatively consistent volumes of oocytes. This consistency between different colonies of the same species suggests that reproduct!ve .effort may be valuable as an indicator of sub lethal stress in corals.

Item Type: Thesis (Honours)
Murdoch Affiliation(s): School of Biological and Environmental Sciences
Notes: Note to the author: If you would like to make your thesis openly available on Murdoch University Library's Research Repository, please contact: Thank you.
Supervisor(s): Borowitzka, Michael and Simpson, Chris
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