Effects Of Light On The Growth,Respiration And Excretion In Tridacna Crocea

Tridacnidae spp. is a kind of large tropical marine coral reefs benthic shellfish. The necessary nutrients to the growth of Tridacnidae spp. are derived from the photosynthesis of symbiotic zooxanthellae and the filter feeding of gill. With the growth of Tridacnidae spp., the proportion of nutrients from photosynthesis is increased. So, the growth of Tridacnidae spp. is heavily dependent on light. The growth, energy metabolism and other physiological activities of Tridacnidae spp. can be affected by light in direct or indirect way. Tridacna crocea is taken as the research object in this study. The effects of light intensity and size on respiration and excretion of T. crocea were studied, and the effects of light color on growth, respiration and excretion of T. crocea were also studied,.The following experimental conclusions are drawn:1. Effects of Light Intensity and Size on Respiration and Excretion of T. croceaThe effects of light intensity and size on the respiration and excretion of T. crocea were studied in laboratory condition, with the indexes of dissolved oxygen, ammonia nitrogen and active phosphate. The results showed that: (1) The T. crocea could release oxygen, and absorb ammonia nitrogen and active phosphate within a certain range of light intensity. While the metabolism of T. crocea was similar to other bivalve mollusks in the dark; (2) Light intensity had an extremely significant effect on the oxygen-production rate,ammonia nitrogen excretion rate and active phosphate absorption rate of T. crocea (P<0.01). Within a certain range of light intensity, the stronger of the light intensity was, the higher the rate of oxygen production rate, and ammonia nitrogen and active phosphate absorption rates were; (3) The metabolism rate of T. crocea was closely related with its size.Within a certain range of light intensity, the oxygen-production rate, ammonia nitrogen and active phosphate absorption rate were markedly positively correlated with its size(L-group>M-group>S-group).While the metabolic rate of T. crocea(per gram of dry weight) was negatively correlated with the size, showing the bigger in size, the lower of oxygen production rate, ammonia nitrogen and active phosphate absorption rate(S-group>M-group>L-group).2. Effects of Light Color on Growth, Respiration and Excretion of T. croceaThe effects of light color(blue, red and white)on the growth of T. crocea were studied under the indoor circulating water system. Meanwhile, the experiment was conducted to investigate the effects of light color on the respiration and excretion of T. crocea in laboratory condition, with the indexes of dissolved oxygen, ammonia nitrogen and active phosphate. The results showed that: (1) The increments of four characteristic indexes of shell length, shell width, shell height and wet weight was blue>red>white. Light color had an extremely significant effect on the increment of wet weight(P<0.01), and it had a significant effect on the increment of wet weight(0.01 <P<0.05), while it had no significant effect on shell width and shell height( P >0.05). (2) The cultivated T. crocea were all had some death, which were respectively under the condition of three light colors.The mortality was blue>red>white, and two of them were significantly different. Under the condition of blue, the death of T. crocea was lower, and the mortality was 5.56%, while under the condition of white, the death of T. crocea was higher, and the mortality was 22.22%.(3) Under the condition of blue and red, the T. crocea could release oxygen, while under the condition of white, it could hardly release oxygen, even consume oxygen. The T.crocea absorbed active phosphate under the three light colors. Under the condition of blue,the T. crocea could absorb ammonia nitrogen, while under the condition of white and red,it released ammonia nitrogen. (4)Under the three light colors, the oxygen production rate,ammonia nitrogen and active phosphate absorption rate of T. crocea was blue>red>white.The light color had an extremely significant effect on oxygen production rate and active phosphate absorption rate(P <0.01),and it had a significant effect on ammonia excretion rate(0.01<P<0.05).3. In a word, the light had a significant effect on T. crocea. In the process of fish breeding,we should provide suitable light and nutrition in order to its symbiotic zooxanthellae photosynthesizing, and then finally promote the growth of T. crocea.