Reproduction Biology And Large-scale-cultivation Technology Of Two Sponge Species

Sponges(phylum Porifera)are the most primitive multicellular animals which play an important role in evolutinary history.Meanwhile,they are the key groups that help to improve our knowledge of the phylogeny of metazoa.Moreover,rich/diverse bioactive compounds in sponges make them potentially pharmaceutical organisms.The unique spicules and skeletons can also be used as important biological materials in pharmaceutical industry.However,drug researches and developments of biomaterials from sponges are facing "supply problem".In order to provide sufficient sponge biomass for subsequent research and production,it is imperative to carry out sponge culture research and build a large-scale and sustainable sponge culture system.At present,the prominent sponge farming method is asexual reproduction.Unfortunately,degradation of germplasm as well as uncontrollable germplasm sources external factors makes it difficult to maintain the sustainable reproduction mode for future sponge industry.This thesis focused on two types of sponges,Spongia officinalis and Haliclona simulans,as experimental subjects to study asexual reproduction,juvenile cultivation and controllable ecological breeding,aiming to make progresses in large-scale sponge aquaculture technology,sexual breeding technology and indoor culture technology so as to establish the prototype solutions for sustainable development of sponge industry in the future.The research was divided into three parts:(1)large-scale asexual culture of the two types of sponges;(2)juvenile cultivation of the two types of sponges;(3)controlled ecological cultivation of H.simulans.The specific results were as follows:(1)Studies on large-scale asexual aquaculture of sponge S.officinalis and H.simulans were carried out in Danzhou intertidal zone of Hainan province and Zhaoan Bay of Dongshan,Fujian province respectively.Firstly,in Danzhou intertidal zone of Hainan Province,we compared the effects of three culture methods on S.officinalis,named tile method,spring method and rope method in small scale experiments that lasted for 18 months.The results showed that the effects differed drastically among methods.Tile method showed better results no matter in survival rates or growth rates.Then we used tile method to expand the scale cultivation of sponge S.officinalis.We placed15000 pieces of sponge explants in intertidal area with the area of about 300 m2.Twelve months later,the results showed that the survival rate of large-scale culture was 41.4%,which significantly lower than that of small-scale experiments(86.67%).In terms of growth rate,the initial wet weight of sponge increased by about 157.09%,which was in line with the 12 months’ relative volume growth(157%)under smallscale culture experiment.The bath sponge officinalis grew slowly,the average of the sponge wet weight was 198.63±76.53 g during 12 months,with an increase rate of 157.09%compared with the initial wet weight of the sponge.While only 16%of the individual sponge biomass range from 300 g to 400 g after 12 months’ cultivation,meeting the harvest requirements.As a result,the cultured bath sponge in this experiment could not achieve a better expectation,we need to reconsider the culture strategy.In addition,we analyzed the correlation between the survival and growth rates of S.officinalis and sea water temperature.The results showed that the survival and growth rates of the sponges were not significantly correlated with sea water temperature which indicated that this kind of sponge could endure a certain degree of low temperature.Thus,it was feasible to transplant the sponge to northern seas such as Fujian province.Eighteen months of large-scale sponge H.simulans culture was carried out with 1792 net frames.The results showed that the survival rate of sponge was close to 100%in the end with growth rate of about 2427.91%.Apparently,this method could attain great breeding effects and could be applied to large-scale breeding of sponge H.simulans.Based on the commonality and individuality of the above experiments,we deducted that the growth of sponge explants varied in different species of sponges,culture environments and culture methods.Moreover,methods and management guidelines suitable for large-scale asexual sponge breeding were discussed and summarized in this thesis.(2)Studied on the developmental biology of larvae and juveniles of sponges S.officinalis and H.simulans,including the release pattern of sponge larvae,the settlement and metamorphosis pattern of larvae and appropriate breeding methods of the sponge juveniles.The results showed that the adult sponge began to release larvae from May to June.The sponge almost released larvae everyday and the daily larvae released peak of S.officinalis was between 06:00 and 09:00.The sponge larvae preferred substrates with rough surface and biofilm for settlement and metamorphosis in dark environment.The ideal breeding mode for sponge S.officinalis juveniles should be under external circulating water flow for indoor breeding,while with hanging net(250 μm in diameter)protection for sea water breeding.On the basis of the results,we also explored the juveniles culture of H.simulans and found that the plastic plates were suitable substrate for the juveniles and the settlement rate could reach 50.00±5.00%in 24 h.The suitable breeding mode was that the juveniles should be breeding indoor with the petri dishes upside-down for 15 days before transferred to the sea under the condition of 180 μm net protection,at last removed the protecting net after 60 days.By applying this method for H.simulans juveniles culture after 120 days,the maximum length reached 33.4 mm as volume increased more than 20000 times,which hit the sponge juvenile growth rate record high.In this study,we optimized the balance between survival rates and growth rates of sponge juveniles by changing culture methods in time,thereby established a feasible and low-cost breeding scheme for sponge juveniles.(3)Studied on the sponge growth under controllable ecological conditions.Firstly,the cultivation devices with sustainable water circulation function was set on the sea floating rafts.We put a few transplants of H.simulans in every cultivation device and pumped continuously with different rate of water flow into the devices.All of the pumped water were previously filtered by 250 μm mesh.We carried out a 120 daysexperiment to figure out how the flow rates of natural sea water influenced on sponge growing.The results reflected that when the natural seawater flow rates were 10± 1.66 mL/s,27.77±2.54 mL/s,60.27± 1.73 mL/s and 80± 1.66 mL/s,the sponge explants volume growth rates would be-100%,111.59±24.67%,108.79±35.69%and 174.45±33.39%,respectively after 120 days.Therefore,minimum rate of water changing was required to maintain positive growth.When water flow rates were above the minimum,the sponge growth rate would increase with the increasing of water flow rates.Although it was theoretically speculated that there must be a maximum water exchange rate,over which the growth rate of sponges would be reduced due to excessive current,but this experiment failed to detect the maximum water exchange rate due to the limitation of experimental equipment.This study also monitored the parameters of aquaculture water for a long time and found that the physicochemical parameters such as nutrients and water temperature had no significant effect on the growth of H.simulans.This study confirmed that the reported that the sponge growth not only required a very high level of nutrient input,but also released a large number of cell shedding.Local seawater with rich POM and high water exchange rate could provide sponges with high-quality natural feed and discharge cell shedding in time.In the absence of sponge feeding or shedding devices,the controllable indoor culture of sponges could be achieved through continuous high-throughput replacement of natural seawater.