Preliminary Study On Dividing Facility And Prepared Feeds In The Juvenile Sea Urchins Strongylocentrotus Intermedius Culture

The sea urchin(Strongylocentrotus intermedius)is an important economic species.With the continuous expansion of breeding scale,high-quality seeds are essential for sea urchin aquaculture.Juvenile sea urchins culture is the most important source of sea urchin seedlings,but the seedling lacks suitable facility and artificial feed,the production efficiency of seedlings is thus low.Sea urchins are commonly placed in simple plastic mesh frames,aggregating in small volume of water.This high density and crowding aquaculture mode is not beneficial to the growth and development of sea urchins.The key to solving this problem is designing an exclusive facility to reduce the local crowding interactions.In addition,natural feed of the sea urchins is scarce,and the cost of raising the temperature is larger.Designing low-temperature feeds can greatly improve the production efficiency of seedlings,supply the more effective feed in winter.New aquaculture facility and feed is beneficial to develop the energy-efficient juvenile sea urchin culture mode.This study explores influence of reduce local crowding interactions in the sea urchins in high density culture,and designs an aquaculture facility to growing environment of the sea urchins.This study designs new artificial feeds and supply the more effective feed in winter,and further upgrades the juvenile sea urchins culture.1.Reducing the crowding interactions improves the growth and disease prevention efficiency of sea urchins in the juvenile sea urchins cultureStrongylocentrotus intermedius prefers gathering together,but high crowding interactions of the sea urchins is undesirable.Keeping the high density breeding and reducing effect of the crowding interactions of the sea urchins is the key to solve these problems.Therefore,we conducted an experiment for 5 weeks.The sea urchins with test diameter of 1cm were divided into 3 groups: high crowding group(group H),medium crowding group(group M),and low crowding group(group L).Body size,lantern grown,gut weight,gut weight and histological tissues were evaluated after the experiment for each group.The finding indicated that there was significantly higher body size in the sea urchin in the group L(test diameter: 17.18 ± 1.51 mm;body weight: 2.57 ± 0.59 g)than those in the group H(test diameter: 15.53 ± 1.68 mm;body weight: 2.01 ± 0.56 g).There was significantly higher gut weight in the sea urchins in group L(0.14 ± 0.07 g)than those in group H(0.07 ± 0.03 g),with intestinal ring folds arranged neatly,and the normal cell morphology,almost without tissue cavitation.This can be explained by the greater food digestion and faster growth rate in the sea urchins in low interactions.In addition,the present study indicated this morbidity was significantly reduced in sea urchin in group L(21.25 ± 13.56%)than those in group H(67.14 ± 14.96%).This can be explained by the greater disease resistance in the sea urchin in low local interactions.Reducing the interactions greatly improved the growth and disease prevention efficiency of sea urchin during the juvenile rearing period.There were the greatest growth indices like test diameter and body weight in the sea urchins in low interactions.This is probably because lantern and gut were best developed in digestive organs of sea urchins.In addition,in the toxicity resistance experiment,there were the lowest morbidity in the sea urchin in group L.Therefore,this research raises a new technology by high density and low local interactions in the culture of juvenile sea urchins.2.Design of dividing low-level interaction facility and its effect on ingestion and growth of the sea urchinsTo reduce local crowding interaction in the sea urchins in juvenile sea urchins culture,this study proposed and produced a dividing low-level interactional facility for culture of sea urchins.Cultivation water was divided into horizontal and longitudinal compartments in the facility,this was significantly greater space efficient in cultivation water and easy for operation.We stimulated juvenile sea urchins culture in winter to result verify the validity of this facility,contrastive analysis growth of the sea urchins in new or common facilities and explored the application potential of low-level interactional facility in production.The sea urchins with test diameter of 1cm were divided into 2 groups: the experiment group(new facility)and the control group(common facility).Feeding the sea urchins with artificial formulated feed in 14.05 ±0.5 °C.Test diameter,body weight,lantern length and food consumption of the sea urchins were evaluated after the experiment.This study found that lantern length was significantly higher body size of sea urchins in the experiment group(test diameter: 14.67 ± 1.29 mm;body weight:1.37 ± 0.31 g)than those in the control group(test diameter: 13.11 ± 1.50 mm;body weight: 1.08± 0.33 g).It indicated growth rate of sea urchins was faster in new facility.Development of digestive organ in the sea urchins in the experiment groups is greater than those in control group.Lantern length was significantly longer in sea urchins in the experiment group(5.05 ± 0.12 mm)than those in the control group(4.68 ± 0.27 mm).This can be explained by the faster growth rate and greater food digestion in the sea urchins in new facility.Food consumption was significantly longer in sea urchins in experiment group(0.07 ± 0.01 g.ing-1.day-1)than those in the control group(0.04 ± 0.01 g.ing-1.day-1).The result indicates that the low-level interactional facility led to greatly improve the food consumption,body size and digestive organ of growth in sea urchins.This indicates that the new facility significantly reduce the effect of ingestion and growth of the sea urchins while it keeping the high density breeding.The new facility has some advantages which were simple production,cheap cost,easy maintain and operation.This facility is not lifted with less labor and low irritation to the sea urchins in daily management.In addition,sea urchins enable utilize longitudinal cultivation water in the facility,it can improve the space efficient in cultivation water and has wide application.This research designs and stimulates a new low-level interactional facility,it has advantages including shorter culture period,higher practicality and so on.The facility greatly improve the economic performance in juvenile sea urchins culture,has great application potential.3.Effect of different feeds on behavior growth and disease prevention efficiency of sea urchins at low temperatureThis study proposed feed Ⅰ and feed Ⅱ which were different feed of defined amount protein and fat,high ash content and fiber,then evaluated it is each component contents.Feeding S.intermedius with Laminaria species(group A),feed Ⅰ(group B)and feed Ⅱ(group C)at low temperatures(5.41 ± 0.29 °C)for 6 weeks,test diameter,body weight,lantern length,lantern weight and gut weight were subsequently evaluated,measured Aristole’s lantern reflex of sea urchins and conducted a foraging behavior experiment to evaluate the attraction of deferent feed for sea urchins.We conducted righting behavior and tube feet extension experiment to evaluate the vigor of sea urchins,evaluated disease prevention after disease challenge assays.The present result found that crude protein,crude fat,crude fiber and crude ash of feed Ⅰ and feed Ⅱ was significantly higher than those of Laminaria species.There were significantly higher body size in the sea urchin in groups B(test diameter: 14.33 ± 1.91 mm;body weight: 1.62 ± 0.44 g)and C(test diameter: 14.44 ± 1.54 mm;body weight: 1.69 ± 0.45 g)than those in the group A(test diameter: 13.22 ± 1.47 mm;body weight: 1.25 ± 0.37 g).Development of digestive organ in the sea urchin in the groups B and C is greater than those in group A.Lantern length was significantly reduced in sea urchins in group A(4.65 ± 0.28 mm)than those in groups B(5.20 ±0.30 mm)and C(5.50 ± 0.31 mm).There were significantly less gut weight in sea urchin in group A(0.05 ± 0.02 g)than those in groups B(0.14 ± 0.04 g)and C(0.10 ± 0.04 g).This can be explained by the greater power of ingestion and faster growth rate in the sea urchins witch intaked feed Ⅰ and feed Ⅱ.Foraging behavior of sea urchins in groups B and C showed greater,foraging time was significantly longer in sea urchins in group A(707.37 ± 512.39 s)than those in group B(268.69 ± 116.73 s)and group C(360.19 ± 405.59 s);There were significantly shorter foraging distance in sea urchins in group A(178.18 ± 111.39 mm)than those in group B(339.97± 157.04 mm)and group C(374.15 ± 133.66 mm).The study indicates more attractions of two feed for the sea urchins.In addition,the sea urchin in groups B and C showed greater in the tube feet extension experiment.There were significantly longer righting time in sea urchins in group A(173.51 ± 85.63 s)than those in groups B(68.76 ± 32.29 s)and C(77.51 ± 28.25 s).This morbidity was significantly reduced in sea urchins in groups B(0.02 ± 00.4%)and C(no morbidity)than those in group A(0.39 ± 0.23%)in disease challenge assays.The result indicates that two feeds greatly improved the growth and development efficiency of sea urchins at low temperatures than Laminaria species.The key components of changes greatly improved the production efficiency during juvenile sea urchins culture,including protein,fat and so on.Ingestion,growth and development efficiency of S.intermedius can decrease with reducing water temperatures,but feed is beneficial to solve this problem and can supply the more nature feed.Therefore,this research: 1)raised a new technology by high density and low interactions in the juvenile sea urchins culture,definitude effects of reducing local crowding interactions on behaviors,growth and disease of the sea urchins;2)designed a dividing low-level interactional facility to improve space efficient in cultivation water,to farther reduce local crowding interactions,improve the food consumption and growth in the sea urchins.3)designed two low-temperature feeds to greatly improve ingestion,growth and development efficiency of the sea urchins at low temperature,supply the more effective feed in winter.This research upgrades the juvenile sea urchins culture of sea urchins,provide important experiences for the breeding larvae of other aquatic organisms,including Apostichopus japonicus,Patinopecten yessoencten,Haliotis discus hannai and so on.