scholarly journals Effects of Symbiodiniaceae Phylotypes in Clades A–E on Progeny Performance of Two Giant Clams (Tridacna squamosa and T. crocea) During Early History Life Stages in the South China Sea

2021 ◽  
Vol 8 ◽  
Author(s):  
Chao Long ◽  
Yuehuan Zhang ◽  
Yunqing Li ◽  
Jun Li ◽  
Zihua Zhou ◽  
...  
Keyword(s):  
South China Sea ◽  
South China ◽  
The South China Sea ◽  
Giant Clam ◽  
Larval Metamorphosis ◽  
The South ◽  
China Sea ◽  
Giant Clams ◽  
Tridacna Squamosa ◽  
Progeny Performance

Unlike most bivalves, giant clams (tridacnids) harbor symbiotic microalgae (zooxanthellae) in their other fleshy bodies. The effects of mixed populations of zooxanthellae on larval metamorphosis has been reported in several papers, but there have been very few studies on the effects of single zooxanthella species on the establishment of symbiosis in giant clams. In this study, we obtained five pure zooxanthella species (clades A3, B1, C1, D1, E1) from antler coral by molecular identification, and analyzed their effects on the larval metamorphosis and progeny performance of two giant clams, Tridacna squamosa and T. crocea, in the South China Sea. Clam larvae with all five zooxanthella species underwent larval settlement and metamorphosis, and formed the zooxanthellal tubular system. There was some variation in metamorphic rate and time to metamorphosis between clams with different zooxanthella species, but no significant differences in size at metamorphosis. After metamorphosis, larvae with all zooxanthella types continued to develop normally. Mantle color was consistent within clam species and zooxanthella species had no effect on mantle color. However, clam progeny with clade E1 zooxanthellae were smaller than progeny with the other four zooxanthella clades (A3, B1, C1, and D1). Survival rate was over 90% for all progeny and there were no significant differences in survival between progeny with Symbiodinium clades A–E during the entire culture process. Two-way ANOVA analysis revealed that giant clam species was the main factor influencing progeny growth, with some variation in growth attributable to zooxanthella type. Our results provide new information on both the symbiotic relationship between giant clams and zooxanthellae and the mantle coloration of giant clams, and will be useful in giant clam seed production and aquaculture.

scholarly journals Diversity of Three Small Type’s Giant Clams and Their Associated Endosymbiotic Symbiodiniaceae at Hainan and Xisha Islands, South China Sea

2021 ◽  
Vol 8 ◽  
Author(s):  
Qiqi Chao ◽  
Zhifeng Gu ◽  
Aimin Wang ◽  
Chunsheng Liu ◽  
Yi Yang
Keyword(s):  
South China Sea ◽  
South China ◽  
The South China Sea ◽  
Giant Clam ◽  
The South ◽  
Xisha Islands ◽  
China Sea ◽  
Giant Clams ◽  
Clade C ◽  
Gene Coi

Giant clams are found in a mutualistic association with Symbiodiniaceae dinoflagellates, however, the diversity of the giant clams, as well as the diversity and distribution of Symbiodiniaceae in different Tridacnine species remain relatively poorly studied in the South China Sea. In this study, a total of 100 giant clams belonging to small type’s giant clams, Tridacna maxima, T. crocea, and T. noae, were collected from Hainan and Xisha Islands. Based on mtDNA cytochrome c oxidase subunit 1 gene (COI) and 16S rRNA fragments, T. maxima and T. crocea showed a closer phylogenetic relationship than T. noae. All the three species of giant clams hosted Symbiodiniaceae including genera Symbiodinium (formerly Clade A) and Cladocopium (formerly Clade C). Geographically, symbionts in Cladocopium are restricted to Xisha Islands, probably because Cladocopium prefers to inhabit in waters with higher mean temperatures. The endosymbiont specificity among the three giant clam species was also detected. T. noae and T. crocea are found to harbor Symbiodinium preferentially, compared with Cladocopium. These results could provide important information to understand various endosymbionts occurring in giant clams in the South China Sea.

Phenotypic traits of two boring giant clam (Tridacna crocea) populations and their reciprocal hybrids in the South China Sea

Aquaculture ◽  
2020 ◽  
Vol 519 ◽  
pp. 734890 ◽  
Author(s):  
Yuehuan Zhang ◽  
Zihua Zhou ◽  
Yanping Qin ◽  
Xingyou Li ◽  
Haitao Ma ◽  
...  
Keyword(s):  
South China Sea ◽  
South China ◽  
The South China Sea ◽  
Phenotypic Traits ◽  
Giant Clam ◽  
The South ◽  
China Sea ◽  
Reciprocal Hybrids ◽  
Tridacna Crocea

Offshore Coral Reef Damage, Overfishing, and Paths to Peace in the South China Sea

2017 ◽  
Vol 32 (2) ◽  
pp. 199-237 ◽  
Author(s):  
John W. McManus
Keyword(s):  
Coral Reef ◽  
South China Sea ◽  
South China ◽  
Building Materials ◽  
The South China Sea ◽  
Collaborative Management ◽  
Giant Clam ◽  
The South ◽  
China Sea ◽  
Decadal Scale

Offshore coral reefs of the South China Sea are subject to complex overlapping sovereignty claims by up to six regional nations. Escalating tensions have led to widespread structural reinforcement of military outposts on many reefs via dredging and filling. Satellite images indicated at least 160 km2 of coral reef damage, including 17 km2 of essentially permanent damage from filling and channel/harbour dredging, and 143 km2 of decadal-scale damage from dredging for building materials and giant clam harvesting. This damage will exacerbate the growing regional overfishing problem. Options to lessen tensions include (1) the establishment of a Greater Spratly Islands Peace Park, and (2) the collaborative management of fisheries, the environment and mineral resources across the entire Sea. Both options require freezes on extant claims and activities in support of claims. No matter how it is achieved, regional peace would greatly enhance fisheries stability and economic growth among all claimant nations.

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