Vertical Zoning Pattern Of The Sumonie Oyster Crassostrea Ariakensis And The Kumamoto Oyster Crassostrea Sikamea And Its Driving Mechanism

The Suminoe oyster Crassostrea ariakensis and the Kumamoto oyster C.sikamea coexist and are habitat-forming ecosystem engineer in Yangtze River estuary and its adjacent coasts.So far,little quantitative information was available on the intertidal zonation pattern of these 2 oyster species and its driving mechanism by which to generate the spatial pattern.The study firstly carried out a series of field surveys and lab experiments to explore vertical zonation pattern of these 2 oyster species in the intertidal habitats of Hangzhou Bay,assess the role of aerial exposure stress and biotic factors(larvae distribution and settlement,competition)in regulating vertical zonation,and understand possible mechanisms that generated the zonation pattern.The main research results are as follows:1.Vertical distribution pattern of Sumonie oyster Crassostrea ariakensis and the Kumamoto oyster Crassostrea sikamea adultsAt our study site,the oyster C.sikamea dominated the high intertidal zone,while C.ariakensis occupied the following 3 zones(mid,mid-low and low intertidal).The Kumamoto oyster C.sikamea adult appeared only in the tidal zone of 2.3m and3.0m,and the density of the tidal zone in the 3.0m tidal zone was significantly higher than that in the tidal zone of 2.3m.The SH value in the 3.0m tidal zone was slightly higher than the tidal zone of 2.3m;Adults of C.ariakensis distributed in four tidal zones of the pile foundation(0.9m,1.6m,2.3m,3.0m).The maximum density appeared in the 1.6m tidal zone,while the density of the Sumonie oyster C.ariakensis in the 3.0m tidal zone was significantly lower than that of the other three tidal zones(0.9m,1.6m and 2.3m),and the density of the Sumonie oyster C.ariakensis was 2.3m and 1.6m or there was no significant difference between the 1.6m and 0.9m tidal zones.The comparison was found in the 2.3m tidal zone.The density of the the Sumonie oyster C.ariakensis was larger.The average SH of the Oyster oyster adults was as follows:3.0m<2.3m<1.6m<0.9 m.In the highest tidal zone,Kumamoto oysters C.sikamea exposed an average of 56%,with an average of 56%and 42%of aerial exposures representing the optimal growth zone and minimum boundary of Kumamoto oysters C.sikamea.However,a reverse community model was discovered in the middle tidal zone,and the Sumonie oyster C.ariakensis alone occupied two tidal zones below the mid-tidal zone.Therefore,the growth boundaries of the two oysters are 42%in the intertidal height,the maximum density area of the the Sumonie oyster C.ariakensis is about 25%of the exposure time,and the middle and low tide zone represents the best growth area.2.Spatial distribution pattern of larvae of Sumonie oyster Crassostrea ariakensis and the Kumamoto oyster Crassostrea sikameaOur results from Q-PCR found that most of the oyster larvae(most pediveliger larva with eyespot)distributed in surface water.C.sikamea and C.ariakensis dominated in the surface and bottom layer of water,respectively.In Liya mountain,the maximum abundance of larvae of Kumamoto oyster C.sikamea and Sumonie oyster C.ariakensis(represented by gene copy number)is mainly concentrated in early August and mid-August;In Luchaogang harbor,the maximum abundance of the larvae of these two species are concentrated in early August.The best seedling time is in early August.The abundance of the larvae of Kumamoto oyster C.sikamea in the surface layers of Liya shan and Luchaogang harbor are always more significantly than that of Sumonie oyster C.ariakensis(P≤0.001);the abundance of the Sumonie oyster C.ariakensis larvae of the lower oysters are always more than that of the Kumamoto oysters C.sikamea Larvae(P≤0.001).The vertical gradient of the larvae of Kumamoto oysters C.sikamea are consistent with the intertidal zone pattern of adult oyster density,but this model is not applicable to Sumonie oyster C.ariakensis.The distribution of oyster larvae in the intertidal habitat and the density of adult oysters showed a reverse pattern.3.Health status of Sumonie oyster Crassostrea ariakensis and the Kumamoto oyster Crassostrea sikamea under dry dew stressWater lost percentage in the lab 72h exposure experiment at 14.6℃,16.7℃and 19.6℃were significantly greater for C.ariakensis than for C.sikamea after 24h(P<0.01).C.ariakensis had the relatively greater dry meat weight and lower water weight in soft tissue than C.sikamea(P<0.001).Significant relationships were found between the shell height and the dry wet for C.ariakensis and C.sikamea.The slope of the regression is 0.0010(SE:0.0044,P=0.031)for the C.sikamea,and 0.030(SE:0.0064,P<0.001)for the C.ariakensis,respectively.The further analysis showed the coefficients between the SH and the WD in the C.ariakensis is significantly greater(effect size:-1.105,95%CI:[-1.392,-0.819])than in the C.sikamea.Another major reason is that the lower soft tissue dry weight and higher tissue moisture content are Kumamoto oyster C.sikamea.4.Immune response of Sumonie oyster Crassostrea ariakensis and the Kumamoto oyster Crassostrea sikamea under dry dew stressIn this experiment,two types of oysters were exposured carried out at Winter,spring and autumn.The corresponding tissues were determined to represent respiratory metabolism,antioxidant capacity and immunity.From the 24th,the LD content of Sumonie oyster was significantly higher than that of Kumamoto oyster(P<0.05).The LDH activity of C.ariakensis was always significantly higher than that of C.sikamea(P<0.01).After 18th,the SDH of C.ariakensis Vitality was always significantly lower than that of C.sikamea(P<0.05).The respiratory metabolism of C.sikamea is more stable than that of C.ariakensis.At the beginning of 6th,the CAT activity of C.sikamea was significantly higher than that C.ariakensis(P<0.05).From the 12th hour,the SOD activity of C.sikamea was significantly higher than that C.ariakensis(P<0.05).From the 6th hour,the GST activity of C.ariakensis is always significantly lower than that of C.sikamea,indicating that C.sikamea is strong antioxidant capacity and the ability to scavenge free radicals is stronger than that C.ariakensis.From the 6th hour,the Na~+K~+-ATPase activity of both oysters increased first and then decreased.The Na~+K~+-ATPase activity of C.sikamea was significantly higher than C.ariakensis(P<0.01),indicating that the ability of C.sikamea regulation drives that transport capacity of sugars and amino acids in cells are relatively strong and stable.Under spring and autumn exposure,the acid phosphatase ACP and alkaline phosphatase AKP stress of the two oysters were different,but the ACP and AKP of the C.sikamea were always higher than C.ariakensis(P<0.05).Reactive oxygen free radicals are more damaging to environmentally stressed cells than pluripotent cells.The malondialdehyde MDA content of C.ariakensis always intersects with the MDA content of C.sikamea,indicating that C.sikamea is more sensitive to dry dew during exposure treatment,so the C.ariakensis is more lipid peroxides firstly.As the exposure time continues.The MDA content of mantle of C.sikamea also increased,indicating that the C.ariakensis was more damaged by environmental stress than C.sikamea,and the non-oxidative defense performance of C.sikamea was stronger than C.ariakensis.5.Stress expression of HSC70 and i-type lysozyme genes in two oysters under dry dew stress in summerThe expression of HSC70 and i-type lysozyme genes in the cells changes accordingly.In this study,the expression levels of HSC70 and i-type lysozyme gene both increased first and then decreased sharply.Under the conditions of continuous exposure in summer,the expression of different tissue genes in different species is different.The rules of HSC70 gene m RNA and i-type lysozyme in the occipital muscle,visceral mass,mantle and sputum of two species oysters are similar.The expression of HSC70 gene in C.ariakensis increased first and then decreased to the control level.The C.sikamea decreased to even higher than normal levels,showing a significant time dependence.HSC70 may be involved in the regulation of dry stress.visceral masses are suitable for the tissue-specific expression of C.ariakensis and C.sikamea,respectively,and play an important role in regulating the stability of the protein environment.Two-way-ANOVA showed that species and time had significant effects on the relative expression of i-type lysozyme m RNA in each tissue of both species(P<0.01).After36h,they returned to the original balance or had a plateau balance to exert immunity.By the72 hour,the recovery level of C.ariakensis was significantly higher than that C.ariakensis(P<0.001).Gills and visceral mass are suitable as the indicator organs of the response of oyster to i-type lysozyme gene.In conclusion,HSC70 and i-type lysozyme gene stress dry dew of Kumamoto oyster C.sikamea are more stable to regulate the intracellular environment.Our main conclusion is that the spatial distribution and dry dew ability of larvae are the main mechanism of the vertical zoning of oyster species in the habitats between high tide and medium and low tide.The answers to the above two questions have important theoretical and practical significance for the selection of reef oysters and the restoration of oyster reefs.