Study On The Commensal Behavior Of Nereids Cheilonereis Cyclurus And Hermit Crabs Pagurus Ochotensis

Cheilonereis cyclurus buries into the shell and commingles with Pagurus ochotensis for food resources and effective protection,but how Pagurus ochotensis profit from Cheilonereis cyclurus has not been reported.As Marine benthic organisms,they play an important role in the process of Marine material circulation and energy flow.The study on symbiosis behavior of Cheilonereis cyclurus and Pagurus ochotensis can deeply understand the respective ecological strategies of bombyx cyclolepis and large hermit crab,as well as the formation mechanism and influencing factors of these strategies.To explore how to carry out interspecific cooperation and benefit distribution as symbionts.It is of great ecological significance to further establish the symbiotic relationship between Cheilonereis cyclurus and Pagurus ochotensis.Through biological observation,biological character determination,artificial breeding,larval culture and behavioral experiments,this study carried out the behavioral research of Cheilonereis cyclurus and Pagurus ochotensis.Specific results are as follows:1.When the shell mouth area is large,the volume and weight of Npatunede cumingi are greater than that of Neverita didym and Cryptonatica andoi.Pagurus ochotensis shows a linear relationship between the length of the right and left sharks,while the length of the right and left sharks has a power function relationship with the weight of the crab,and the length of the head breastplate has a power function relationship with the weight of the crab.The length of the right claw,the length of the left pincer,the length of the head breastplate,the weight of the crab and the area and volume of the shell mouth all had an s-curve relationship.There was a linear relationship between body length and body width(R =0.459),and a linear relationship between weight and volume(R =0.890).Cheilonereis cyclurus is positively correlated with snail shell,but the correlation degree is not high,which is weak correlation or moderate correlation.The results show that Pagurus ochotensis has a higher selectivity for snail shells,but Cheilonereis cyclurus has a lower selectivity for snail shells.As long as the inner space is sufficient,Cheilonereis cyclurus enters the shell more for symbiosis with Pagurus ochotensis so as to obtain more food and protection.2.Pagurus ochotensis larvae can be divided into zoea?,zoea?,zoea?,zoea?,megalopa,crabs ? and crab? period.The morphology of Pagurus ochotensis larva is quite different from that of crab larva: in daphnia larva,the cichlothorax is nearly cylindrical,the cichlothorax spine extends straight and forward,and there is no spine on the dorsal side,while in daphnia larva,there are dorsal spine and frontal spine on the dorsal and ventral sides of cichlothorax.In largeminal stage,the largeminal hermitage crab had a long second tentacle whip,while the second tentacle whip of the crab was shorter.During the juvenile period,the Pagurus ochotensis abdominal segments disappear,the abdomen is asymmetically left to right and twisted to the right,while the crab segments still exist,bent and attached to the head,chest and abdomen.3.Cheilonereis cyclurus has no significant selectivity for the four types of snail shells,and its entry into the shell is an instinctive behavioral strategy by which it waits for Pagurus ochotensis to use the shell and symbiosis with Pagurus ochotensis.Cheilonereis cyclurus is sensitive to vibration and has no significant difference from the hermitage crab group,but has no obvious reaction to the signal molecules feeding Pagurus ochotensis,which is similar to the sensing mechanism of Nereis fucata.When feeling the movement around the hermit crab,the Cheilonereis cyclurus in the substrate will go out of the surface and actively look for Pagurus ochotensis and enter into the shell.Cheilonereis cyclurus in empty snail shells are rarely went out.This indicates that Cheilonereis cyclurus in the substrate has a stronger motivation to actively seek Pagurus ochotensis,while Cheilonereis cyclurus in the empty shell chooses to wait for Pagurus ochotensis to use the shell,and going out of the shell to search for Pagurus ochotensis may require a greater risk.4.There was no significant difference in the selectivity of Pagurus ochotensis in the three weight groups with Cheilonereis cyclurus to the shells with Cheilonereis cyclurus(P > 0.05).The selection probability of the shells with Cheilonereis cyclurus and without Cheilonereis cyclurus was about 50%.Pagurus ochotensis has no obvious selectivity to the shell with or without Cheilonereis cyclurus,which indicates that its selectivity to the shell is more important.It may also be that Pagurus ochotensis,in its exposed state,first needs a shell that provides protection,without considering whether Cheilonereis cyclurus is in the shell,or is unable to make a final choice within 24 hours.