Effects of the daily light/dark cycle on photosynthetic performance, oxidative stress and illumination-related genes in boring giant clam Tridacna crocea

In this work we studied the effect of salinity (ranging from 50 to 500 mM NaCl) on the physiological and the antioxidant responses of the local halophyte Limonium delicatulum Kuntze. We based our analysis on 12 biochemical assays that are commonly used to measure the antioxidant responses under stress such as oxidative stress markers, enzymes activities and polyphenolic compounds. Our aim was to study parameters that are strongly correlated with the growth response to salinity. Results showed two different growth responses depending on the concentration of NaCl in the medium. Under 50 to 200 mM, the growth was stimulated before it decreased significantly at 300–500 mM. L. delicatulum revealed a good aptitude to maintain photosynthetic machinery by increasing the concentrations of photosynthetic pigments, which is essential for the stabilisation of photosystems and the photosynthesis process under optimal NaCl concentration. Their breakdown at higher salinity decreased the photosynthetic performance of plants resulting in growth inhibition. Moreover, to reduce the damaging effect of oxidative stress and to tolerate the accumulation of salt ions, L. delicatulum induced the activities of their antioxidant enzymes more than their contents in polyphenolic compounds.

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Parasitism by a Protozoan in the Hemolymph of the Giant Clam,Tridacna crocea

Journal of Invertebrate Pathology ◽

10.1006/jipa.1997.4747 ◽

1998 ◽

Vol 71 (3) ◽

pp. 193-198 ◽

Cited By ~ 7

Author(s):

Koji Nakayama ◽

Miyuki Nishijima ◽

Tadashi Maruyama

Keyword(s):

Giant Clam ◽

Tridacna Crocea

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Isolation and characterization of 9 polymorphic microsatellite markers for the endangered boring giant clam (Tridacna crocea) and cross-priming testing in three other Tridacnid species

Conservation Genetics Resources ◽

10.1007/s12686-010-9249-7 ◽

2010 ◽

Vol 2 (S1) ◽

pp. 353-356 ◽

Cited By ~ 4

Author(s):

Timery S. DeBoer ◽

Paul H. Barber

Keyword(s):

Microsatellite Markers ◽

Giant Clam ◽

Isolation And Characterization ◽

Polymorphic Microsatellite ◽

Tridacna Crocea

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Distribution and abundance of the giant clams (Cardiidae: Bivalvia) on Kei Islands, Maluku, Indonesia

Biodiversitas Journal of Biological Diversity ◽

10.13057/biodiv/d200337 ◽

2019 ◽

Vol 20 (3) ◽

pp. 884-892 ◽

Cited By ~ 1

Author(s):

TEDDY TRIANDIZA ◽

NEVIATY P ZAMANI ◽

HAWIS MADDUPPA ◽

UDHI E HERNAWAN

Keyword(s):

Giant Clam ◽

Population Status ◽

Anthropogenic Pressures ◽

Composition Distribution ◽

Dead Coral ◽

Transect Line ◽

Giant Clams ◽

Kei Islands ◽

Tridacna Crocea ◽

Clam Population

Abstract. Triandiza T, Zamani NP, Madduppa H, Hernawan UE. 2019. Distribution and abundance of the giant clams (Cardiidae: Bivalvia) on Kei Islands, Maluku, Indonesia. Biodiversitas 20: 884-892. Giant clams, ecologically important bivalves in coral reefs, are under anthropogenic pressures in most parts of their range, necessitating the study of population status for conservation management. Here, we assessed species composition, distribution, size density, and habitat condition of giant clams in Kei Islands. A total of 9 reefs around the islands (Dar 1, Dar 2, Pulau Kur, Pulau Tanimbar Kei, Pulau Adranan, Pulau Dullah Laut, Difur, Labetawi, dan Ohoidertoom), were surveyed using quadrat-transect line in September-December 2017. We found five species of giant clams, i.e., Tridacna crocea, T. maxima, T. squamosa, T. noae, and Hippopus hippopus. Of these species, we report a new record for T. noae which was previously not known to be present in the region. The overall density was recorded at 0.0428 individual/m2. Juveniles clams were fewer than the adults clam, this may indicate that the survival rate of recruit is low. Most individuals were found living on dead coral algae substrate (75 %). Based on the findings, this study suggests that giant clam population in Kei Islands are imperiled, indicated by low population density and local extinction for species T. gigas and T. derasa. It is recommended to establish a protected area and restocking of giant clams by through implementing sasi laut (traditional law) with a minimum period of 5 years.

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Coral Bleaching Resistance vs Susceptibility: The Role of Antioxidant Activity in Symbiotic Dinoflagellates

10.26686/wgtn.17000842 ◽

2021 ◽

Author(s):

◽

Anne Wietheger

Keyword(s):

Oxidative Stress ◽

Antioxidant Activity ◽

Thermal Stress ◽

Coral Bleaching ◽

Stress Responses ◽

Antioxidant Activities ◽

Photosynthetic Performance ◽

Gulf Of Aqaba ◽

Different Types ◽

And Oxidative Stress

<p>Coral bleaching, the loss of symbiotic dinoflagellate algae (genus Symbiodinium) and/or photosynthetic algal pigments from their coral host has become a regular occurrence in the last few decades due to increasing seawater temperatures. A key consideration in bleaching susceptibility is the symbiotic alga‘s physiology and its capacity to deal with abiotic stress; oxidative stress is of particular interest given that this can arise from thermally induced photosynthetic dysfunction. The aim of this study was to compare the effects of thermal and oxidative stress on the photosynthetic performance of a range of Symbiodinium clades and types (i.e. sub-clades) in different states of symbiosis (in hospite, freshly isolated and in culture). Whether the responses to these two stressors are related was investigated; in particular, it was hypothesised that more thermally sensitive types would be more sensitive to oxidative stress. Furthermore, the study aimed to elucidate the role of antioxidants in the observed stress responses. The specific objectives were 1) to establish whether different types of cultured Symbiodinium have dissimilar sensitivities to oxidative stress, induced by hydrogen peroxide (H₂O₂), and whether these are related to their thermal sensitivities; 2) measure the activity and relative amounts of specific reactive oxygen species (ROS) in different types of cultured Symbiodinium in response to thermal and oxidative stress induced by H₂O₂; 3) measure total antioxidant activity in different cultured Symbiodinium types when under oxidative stress; and 4) compare and contrast the responses of different Symbiodinium types to thermal and oxidative stress when in hospite (i.e. in corals) and freshly isolated. In this study, I showed that different Symbiodinium clades and types can differ widely in their responses to both thermal and oxidative stress. This was indicated by photosynthetic performance measured by chlorophyll fluorescence, and differences in the quantity of specific ROS measured via fluorescent probes and flow cytometry. For instance, when adding H₂O₂ to Symbiodinium F1, originally from Hawaii, a decrease of > 99% in maximum quantum yield (Fv/Fm) was displayed, while there was no change in Fv/Fm in the temperate Symbiodinium A1, freshly isolated from the anemone Anthopleura aureoradiata from New Zealand. When comparing the difference in ROS production between the control (26 °C) and a thermal stress treatment (35 °C), type E1 from Okinawa showed no difference in any of the measured ROS. In contrast, a different A1 type from the Gulf of Aqaba displayed an increase in the overall production of ROS, and more specifically in the production of superoxide. Symbiodinium types also displayed differential oxidative stress resistance, which was apparent from their antioxidant activities; in particular, total antioxidant capacity was measured by the ferric reducing antioxidant potential (FRAP) and cellular antioxidant activity (CAA) assays. For example, the aforementioned Symbiodinium types, A1 from the Gulf of Aqaba and F1, increased their antioxidant activities with increasing H₂O₂ concentrations. Meanwhile, type E1 displayed higher baseline levels of antioxidants in comparison to the other two types (A1, F1), which then decreased with increasing H₂O₂. Specific activities of superoxide dismutase and ascorbate peroxidase were also measured. Stress susceptibility appears to be related both to Symbiodinium type and geographic origin, but greater sensitivity to thermal stress did not necessarily correlate with greater susceptibility to oxidative stress. The exact relationship between thermal and oxidative sensitivities in Symbiodinium spp. remains elusive, but it is suggested that different types might follow different strategies for dealing with stress. I propose that some Symbiodinium types rely more on photo-protection when exposed to thermal stress (and hence cope less with oxidative stress), while other types depend more on antioxidants and oxidative stress resistance. The latter might be the better strategy for types from more variable environments, such as higher latitude reefs or intertidal regions, where potentially stressful conditions may be encountered more frequently. This study gives new insights into the variability of stress responses in the genus Symbiodinium, and the complex relationship between thermal and oxidative stress. The implications of these findings for coral bleaching susceptibility and the biogeographic distribution of different Symbiodinium types are discussed.</p>

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