| Sea cucumber ecological seed is a high-quality seed that is produced in naturalenvironment on the basis of ecology principles with high performance facilities,methods and scientific management of culture environment. This paper focuses onthe research of key technical principles and applications of the sea cucumberApostichopus japonicus ecological seed breeding. By discussing the sea cucumberindustry development and seed production status, we found the major problem inseed quality. The ecological seed breeding, compared with traditional seedproduction method, is better in cost and quality, thus has great developing potentials.In this article, the research focused on the related facility parameters and keytechnical principles of ecological seedling breeding, the main research results are asfollows:1. This article uncovered the embryo development and functionalcharacteristics. The body size of A. japonicus experienced two times of shrinking inits life cycle. The smallest projected area of the sea cucumber body in the entire lifecycle is the two-cell stage, the diameter of which is about130~140μm. The nexttime that the larvae shrink to the smallest is during the pentactula stage, when thediameter of the projected area is about200~220μm. The early pentactula larvaewith the ciliary bands still existing can both swim fast(~2.6mm/s) and attach, andthey are thought to be the optimum stage for the larvae to choose substrates. The justsettled juvenile with only one ambulacral podium has difficulties to migrate, andwith more podia developed the locomotion ability get stronger. The specializedskeleton of the ambulacral podia and buccal tentacles are the basis of the differentfunctioned organs. With the function of the ambulacral podia was perfected, the function of the buccal tentacles previously as the main locomotive organdegenerated and turned into specialized feeding organ.2. This article explored the effects of key environmental factors on larval andjuvenile sea cucumber growth and development. The biological zero of enbryodevelopment for A. japonicus is8.87±0.63°C, above which the growth anddevelopment speed increase as the temperature rise, and19~21°C was proved to bethe optimum temperature for larval rearing. When the temperature is higher than25°C, the survival rate decreased significantly, and no larvae survived after rearingat31°C for one week. Below the optimum temperature, the temporal survival ratedid not decrease significantly with the temperature becoming lower, but theproportion of deformed larvae increased.The optimum salinity for larval development and vitality is31ppt, thelocomotory speed at this salinity is0.64±0.06mm/s; the salinity range during whichthe larvae can complete metamorphosis is23~38, which is also the minimum andmaximum levels for the larval locomotion. Long-term low or high salinity levels cancause lethal damage to the larvae, whereas short-term low salinity levels canenhance larval locomotion, with the negative effects of low salinity beingrecoverable to some extent.The turbidity caused by the suspended sediment in the natural sea water(usually <150mg/l) would not cause lethal damage to the sea cucumber larvae, thusit could not be the reason why the larval survival rate is at a low level in the wild.On the contrary, the suspended sediment that is rich in organic detritus and microbesis actually additional diet for the larvae, and is favorable for the growth andsettlement of sea cucumber larvae.The mud substrate, which is rich in organic detritus and microbes, is favorablefor the feeding and growth of sea cucumbers, but unfit for their locomotion andattachment in coastal sea areas. The water current speed is an important factor thatshould draw more attention when choosing a bottom-sowing culture site. Juvenile sea cucumbers would be washed away in a current speed of>5cm/s, thus artificialreefs or shelters are another prerequisite in bottom-sowing culture systems in coastalsea areas with bare mud substrate on the seabed. Such changes to the aquaculture ofsea cucumbers could help the development of a commercially successful industry.3. The behavioral contacts among individuals and environmental heterogeneitylevel resulted by different cultural methods can change individual growthperformance, but have little influence on the individual growth variation. Theindividual growth variation mostly attributes to the genetic factor, and the differenceof FCE determined by genetic factor among individuals is thought to be the origin ofthe variance.4. The research of the mesh parameter for seed breeding indicated that the meshpore size should be <130μm for the purpose of rearing adult sea cucumber in thefacility for spawning. The mesh pore size should be smaller than0.7times the larvalwidth and200μm(the width of the early pentactula) when rearing pelagic larvae.When rearing the juvenile sea cucumbers, the mesh pore size should be determinedby the young juveniles calcareous ring because the sea cucumbers cannot escapefrom a mesh pore with the same size as the calcareous ring diameter.5. In the environment like Yuehu, which has a large tidal fluctuation, shallowwater, high biodiversity and intensive environmental factors fluctuation, the way ofrearing adult sea cucumbers to spawning is not suitable, but bottom-sowing culturewith juveniles sea cucumber>3.25g/ind is a superior method. However, in winterwhen the sea grass degenerated, the substrate that is fit for the sea cucumbers tosettle is not suffice, thus the construction of artificial reef is necessary. However,considering the scenery and the shallow water, the plan of building artificial reefsstill needs assessment.To sum up, the salinity change other than the temperature and turbidity, shouldbe seriously considered when choosing an ecological seed breeding site. It ispossible to estimate the seed quality in advance by the egg size, larval vitality and the coelomic sac development. The main facility parameter, the mesh pore size,should be determined by the different developmental stage of sea cucumber. Theproper size for bottom sowing culture should be determined by the specificenvironment. In addition, the reefs, artificial or natural, are prerequisite whenchoosing a bottom sowing culture site, and it is not suggested to release juvenile seacucumbers in the open sea areas when there is bare mud or sand, because the bottomcurrent is usually big enough to wash away the sea cucumbers. |
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