| 1Effects of diatom concentration in prepared feeds on growth and energybudget of the sea cucumber Apostichopus japonicus (Selenka)Eight test diets were used in the experiment: seven fresh diatom (Cylindrothecafusiformis) diets in which diatom occupied100%,83.3%,50%,33.3%,20%,14.3%and11.1%in dry matter ofthe feeds (marked as D100, D83, D50, D33, D20, D14andD11), and a formulated diet (70%Sargassum thunbergii powder,20%sea mud and10%fishmeal, based on dry weight, marked as ST). The results showed that the specificgrowth rates (SGRs) of the animals fed diets D33, D20, D14and D11were notsignificantly different from the SGR of those fed diet ST. However, the energyallocated to growth for the animals fed with diet D14was twice that of diet ST. Forsea cucumbers fed diet D14the largest expenditure part was allocated to respiration(55.4%), but for those fed diet ST, the largest part was allocated to faeces (62.7%).Theorganic content of diet D14was also muchlower than that of diet ST. Frozen diatomdiets containing14%(dry matter weight) fresh diatom could be an environmentallyfriendly feed as an alternative option for macroalgae powder.2Effects of four fresh microalgae in diet on growth and energy budget ofjuvenile sea cucumber Apostichopus japonicus (Selenka)A60d feeding experiment was conducted to evaluate the growth performance andenergy budget of the sea cucumber Apostichopus japonicus fed on four freshmicroalgae (Cylindrotheca fusiformis, Dicrateria inornata, Nitzschia closterium,Spirulina platensis) and one granulated macroalga (Sargassum thunbergii) mixedwith sea mud or yellow soil as diets. The results showed that there was no significant difference between the specific growth rates (SGR) of the sea cucumbers fed dietscontaining sea mud and yellow soil. Though the nutrient contents of C. fusiformiswere low, it is large in size with weakly silicified cell wall, which can be easilybroken by A. japonicus. The sea cucumbers fed C. fusiformis diet had significantlyhigher SGR and energy proportion deposited to growth than those fed other four diets.S. platensis possesses a complete cellulose cell wall which can hardly be broken bythe sea cucumbers. Therefore, the test animals fed S. platensis had the lowest growthrate and the highest energy proportion lost in feces among all treatments, even thoughS. platensis had the highest protein contents among the test algae. The SGR of theanimals fed N. closterium and D. inornata were in between of C. fusiformis and S.platensis, partly because N. closterium and D. inornata were small in cell sizes. Theresults indicate that the effects of fresh microalgae in diet on the growth of the seacucumber A. japonicus are influenced not only by nutrient contents of the algalspecies but also by the availability of these nutrients, which is partially determined bythe structure and size of their cell wall.3Effects of ration and attachments on growth, digestive tract indexes anddigestive enzyme activities of sea cucumber (Apostichopus japonicus)Eight treatments were used in this experiment: the sea cucumbers were fed withSargassum thunbergii0,1,3,5%of their body weight respectively (marked as ST0,ST1, ST3and ST5), treatment AST0, AST1, AST3and AST5was fed withattachments on basis of ST0, ST1, ST3and ST5. A positive correlation was foundbetween growth, digestive tract indexes and digestive enzyme activities of the seacucumber and ration. Ration, attachment and their interactions had significant impacton specific growth rates (SGR) of the sea cucumber (P<0.01). Attachmentsignificantly affected the digestive indexes and trypsin activities of the test animal.Digestive enzyme activities of the sea cucumber decreased significantly in case ofchronic hunger, while the variation of different kinds of digestive enzymes wasdifferent. Those results indicated that the attachments not only provided food for thesea cucumbers, but also acted on digestive physiology and affected the absorption of other food sources. When qualities or quantities of the food changed, sea cucumberswould adjust digestive strategy.4. Impact of partial sizes on growth and energy allocation of the sea cucumber(Apostichopus japonicus)A60day feeding experiment was conducted to evaluate the effects of sea mudand sands of two sizes with fresh microalgae Cylindrotheca fusiformis andmacroalgae Sargassum polycystum on sea cucumber Apostichopus japonicus.According to previous studies, the optimum sea mud proportion in C. fusiformis and S.polycystum was86%and20%respectively. Therefore, there were10treatments inthis experiment:86%sea mud (<0.008mm),43%sea mud and43%fine sand(0.074-0.25mm),43%sea mud and43%medium sand (0.25-0.5mm),86%fine sand,86%medium sand mixed with fresh C. fusiformis respectively (marked as CS, CSF,CSM, CF and CM);20%sea mud,10%sea mud and10%fine sand,10%sea mudand10%medium sand,20%fine sand,20%medium sand mixed with S. polycystumrespectively (marked as SS, SSF, SSM, SF and SM). The results showed that Algae,sand and their interactions all affected the specific growth rates (SGR) and ingestionrates (IR) of the sea cucumber significantly (P<0.01). The values of SGR, IR andenergy intake of the sea cucumbers fed fresh microalgae C. fusiformis decreased,while the energy lost in feces increased for those fed diet C. fusiformis (P<0.05) withthe increasing size and proportion of sand in feed (P<0.05). Sand particles alsoaffected the defecation rate of the sea cucumbers significantly (P<0.01). In the first3h after ingestion, the defecation rate increased with the increasing size and proportionof sand in feed. Those results suggested that the main function of sand and sea mud infeed of the sea cucumber is to regulate the time of feed passing the digestive tract anddilute nutrient contents. Different sand proportions should be applied when mixedwith different food ingredients in diets of sea cucumber. Sea mud smaller than0.008mm has better feeding effect on sea cucumber A. japonicus. 5Influence of concentration methods and light densities on breeding effects ofbenthic diatom on sea cucumber (Apostichopus japonicus)Benthic diatom (Cylindrotheca fusiformis) was condensed by centrifugation andsedimentation respectively, after which method of black and white bottle wasconducted to evaluate the primary productivities of benthic diatom under two lightdensities (1500Lx and500Lx). The effects of the two kinds of condensed diatom ongrowth of the sea cucumber (Apostichopus japonicus), water and sediment qualitywere evaluated by a six week feeding experiment, in which Sargassum polycystumand blank group (without feed) was used as control group. The result showed:1. lightdensity, concentration method and their interactions significantly affected the primaryproductivities of the diatom (P<0.01). The primary productivities of sedimenteddiatom were about4times that of centrifuged diatom.2. Light density, feed and theirinteractions significantly affected the growth of the sea cucumber (P<0.01), thesequence of growth rate of sea cucumber was:1500Lx>500Lx; sedimenteddiatom>centrifuged diatom> S.polycystum>blank.3. The C, N and P levels in waterand sediment increased with the proceeding of the experiment, the final sequence isS.polycystum>centrifuged diatom> sedimented diatom>blank. Those results indicatedthat concentrated method significantly influenced the bioactivity of Cylindrothecafusiformis, which affected the feeding effect of diatom. Fresh diatom could be used asan environmentally friendly feed for the sea cucumber, which would perform betterwhen light is given. |
PDF Full Text Request