Photoadaptation in juvenile Tridacna gigas

Mingoa, S. Suzanne M. (1988) Photoadaptation in juvenile Tridacna gigas. In: Copland, J.W., and Lucas, J.S., (eds.) Giant Clams in Asia and the Pacific. ACIAR Monograph Series, 9 . Australian Centre for International Agricultural Research, Canberra, ACT, Australia, pp. 145-150.

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Photoadaptation was demonstrated in the algal symbiosis of juveniles of the giant clam Tridacna gigas. Juveniles that were grown in unshaded ambient light required higher light intensities (about 200 μE/m²/sec, 95% confidence interval: 194-218 μE/m²/sec), for saturation of oxygen production, while those that were reared in approximately 9OClJo shaded ambient light reached saturation at lower light intensities (ISO μE/m²/sec, 95% confidence interval: 126-175 μE/m²/sec). Shade-reared clams had a higher chlorophyll a concentration per cell, and based on chlorophyll a had lower alpha, or photosynthetic, rates at subsaturating irradiance, and lower Pm, or maximum photosynthetic rates, at saturating irradiance.

P:R, specifically the ratio of net zooxallthellae photosynthesis to total respiration over 24 hours, of unshaded clams was significantly higher (p < 0.05) than values for shaded clams. All P:R ratios were higher than 1.0 indicating net primary production. CZAR values, the contribution of photosynthetically fixed carbon to host respiration, were higher in unshaded clams. Greater P:R and CZAR may account for the higher condition index. (wet flesh weight/shell length) in unshaded clams.

Kept in darkness, juvenile clams lost condition within a few days and showed heavy mortality after 6 days. This may support the P:R results in showing the dependence of juvenile clams on their algal symbionts for a major part of their nutrition.

Item ID: 33910
Item Type: Book Chapter (Research - B1)
ISBN: 978-0-949511-70-6
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Funders: AIDAB-ACIAR Grant
Date Deposited: 13 Jan 2015 05:06
FoR Codes: 06 BIOLOGICAL SCIENCES > 0602 Ecology > 060205 Marine and Estuarine Ecology (incl Marine Ichthyology) @ 50%
06 BIOLOGICAL SCIENCES > 0608 Zoology > 060806 Animal Physiological Ecology @ 50%
SEO Codes: 96 ENVIRONMENT > 9608 Flora, Fauna and Biodiversity > 960808 Marine Flora, Fauna and Biodiversity @ 100%
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