The evaluation of culture performance and mantle coloration of two boring giant clam (Tridacna crocea) strains

The boring giant clam (Tridacna crocea) is the smallest species of the Tridacna genus, but they strongly express mantle color polymorphism. These color morphs represent potential genetic resources for aquaculture to supply the aquarium market, and the evaluation of their genetic and production characteristics is important. Wild yellow-green clams were consistently larger than blue clams in both the Huangyan Island and Zhaoshu Island populations in the Southern China Sea. To determine the relationship between mantle color and phenotypic traits, blue, yellow-green and control strains (various colors) were constructed and cultured for 1.5 years at an experimental station in Sanya, Hainan Island Province. All three strains had a high fertilization rate, but the survival to D larvae of the blue strain was significantly lower than the other two strains. Larval survival rate was over 85 % for all three strains, but the metamorphosis rate of the control strain was significantly lower than that of the other two strains. During the grow-out stage, the survival rate of the control strain from day 120 to day 480 was highest and that of the blue strain was lowest of the three groups. After metamorphosis, growth divergence of the three strains varied until day 120. Consistent growth trends appeared from day 120 to day 180, with the yellow-green strain largest, followed by the control strain. The process of mantle coloration was divided into three stages: the non-coloring period (day 0–60), the coloring period (day 60–180), and the stable expression period (day 180 onward). The yellow-green and blue mantle colors are genetically stable. This study provides a base for analysis of mantle color heredity and the genetic breeding of giant clams, and has great potential applications in the aquaculture industry, aquarium market and the coral reef tourism.