| In this paper,Octopus ocellatus were used to study the early growth and development,the histology of the digestive system,the utilization of biological diet and the influence of environmental stress on them.Results of the study were as follows:Experiment 1 In order to define the different phases characterizing this species' post-hatching development,ten larvae were sampled at different periods from post-hatching to when larvae were 50 days-old,and then their body weight,total length,arm length,and mantle length were measured to further analyed the growth characteristics of O.ocellatus.The larval stages of O.ocellatus were divided into a planktonic stage and a benthic stage,with benthic life beginning at the age of 11 d.At water temperatures of 22?~24?,the cultured larvae could grow from an average total length of 10.03 mm on the first day post-hatching to a benthic octopus with an average length of 16.21 mm by the 11 th day post-hatching.The results showed that the body weight of planktonic O.ocellatus increased with time according to a cubic function,the equation of which was y = 0.0001x3 – 0.0019x2 + 0.0098 x + 0.0409.Benthic O.ocellatus body weight increased according to an exponential function,the equation of which was y =0.0284e0.092 x.The total length of O.ocellatus larvae exhibited a cubic relationship with body weight,the equation of which was y = –8e–07x3 + 0.001x2 – 0.011 x + 0.099.Total length was linearly related with arm length,as represented by the equationwhich was y = 1.314 x + 4.952.Body weight,total length,and arm length exhibited cubic growth functions over time,as represented by the equations which was y = 6e–05x3 – 0.003x2 +0.036 x – 0.03,y = 0.0004x3 + 0.002x2 + 0.307 x + 10.604 and y = 0.0004x3 – 0.007x2 + 0.364 x + 4.205,respectively.By studying the growth and development characteristics of larvae,the understanding of larval growth is deepened,and the reference for the study of artificial breeding of short carp is provided.Experiment 2 For a better understanding of nutrition biology of this species,we investigated the microanatomy of the digestive tract of O.ocellatus.The “descending branch” has a dorsal position and is formed by the oesophagus and crop.Ventrally,the “ascending branch” is formed by the intestine and the anus.In the curve of the U-shaped digestive tract,a gastric caecum and the stomach can be found.The stomach of O.ocellatus is more developed than the esophageal muscle layer,and the crop muscle layers are thinner.Gastric cecum and intestinal wall protruding many folds,dense distribution of cilia,thin muscle layer.A large number of mucus cells and goblet cells are distributed in the rectal mucosa.The digestive system was described from the histological angle,and the basis for the study of the digestive physiology of O.ocellatus was established.Experiment 3 Four natural diets of Penaeus vannamei,Hemigrapsus sanguineus,Ruditapes philippinarum and Ammodytes personatus were fed with Octopus octopus with initial body weight of(58.2 ±1.49)g for 30 days.Each diet was fed with 3 repeats and 10 O.ocellatus per diet.The results showed that: 1)the weight gain rate of O.ocellatus in the Hemigrapsus sanguineus group was significantly higher than that in other groups(P<0.05),and the viscerosomatic index in the Penaeus vannamei group was significantly higher than that in the Ammodytes personatus group(P<0.05),and there was no significant difference in heaptosomatic index among the feed groups;2)the crude protein of O.ocellatus muscle in Penaeus vannamei group and Hemigrapsus sanguineus group was significantly higher than that in Ruditapes philippinarum group and Ammodytes personatus group(P<0.05),and the crude lipid of O.ocellatus muscle in Hemigrapsus sanguineus group was significantly higher than that in other groups(P<0.05);3)the activities of glutamic-pyruvictransaminase in the hepatopancreas of Penaeus vannamei were significantly higher than those in the other groups(P<0.05).The activity of hepatopancreas glutamic-oxaloacetic transaminase in the Hemigrapsus sanguineus group was significantly higher than that in the other groups(P<0.05).The activity of glutamate dehydrogenase in the hepatopancreas of Penaeus vannamei group,Hemigrapsus sanguineus group and Ruditapes philippinarum group was not significantly different(P>0.05),but significantly higher than that of Ammodytes personatus group(P<0.05).The activity of acid phosphatase in Ruditapes philippinarum group was significantly higher than that in other groups(P<0.05).The pepsin activity in the Hemigrapsus sanguineus group were significantly lower than those in the other groups(P<0.05).To sum up,Hemigrapsus sanguineus can significantly increase the weight gain rate of O.ocellatus.Different diets had significant effects on protein,lipid and ash content of octopus ocellatus muscle,also on hepatopancreas function and pepsin activity.Experiment 4 The effects of dry dew stress time(2,5,8,11 h)on the antioxidant capacity and stress response were analyzed in two wa ys of oxygen-exposure(G1-group)and air-exposure(G2-group)stress.The changes of water absorption of O.ocellatus under short-term(2,6,12,24hours)stress were determined with salinity gradient(22,24,26,28,30 salinity)and the variations of superoxide dismutase(SOD),catalase activity(CAT),Na+/K+-ATP enzyme activity and muscle lactic acid content in gill under different stress time(24,36,48h)were measured with salinity gradient(22,24,26,28 salinity groups).The results showed that the activities of SOD,CAT and total antioxidant capacity(T-AOC)in G1-group and G2-group increased significantly(P<0.05)and reached the peak value at the beginning of dry dew.After that,the SOD activity in G2-group and the T-AOC activity in G1-group and G2-group were decreased.At the same time,the activity of CAT in G1-group and G2-group increased.Lactic acid content in G1-group decreased firstly and then increased,while that in G2-group increased first and then decreased.The water absorption rate of O.ocellatus decreases with salinity.With the extension of time,it first increases and then decreases,reaching the peak at 12 h.The activity of Na+/K+-ATP enzyme increased firstly and then decreased and then increased with the increase of salinity under 24 h and 36 h stress,increased firstly and then decreased under 48 h stress.In the early period of salinity stress,the activity of SOD and CAT had a synergistic effect and all showed a tendency to increase.With the prolongation of stress time,lactic acid content in 22 and 26 salinity groups increased firstly and then decreased,24 salinity group decreased firstly and then increased,and 28 salinity group did not change significantly(P>0.05).In summary,both dry dew and salinity stress have a significant effect on the physiological state of O.ocellatus,and the antioxidant level of the body significantly increased at the early stage of stress. |
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