| The aim of this study was to investigate the importance of relationship on the growth and survival of juvenile red swamp crayfish, Procambarus clarkii. A laboratory experiment was performed to determine growth and survival of juvenile crayfish which were from1,2,3or4female crayfishes. Relationship clearly affected growth of crayfish. On the whole, survival rate of juvenile crayfish was reduced as the sources of crayfish became more. Meanwhile, the disability rate, coefficient of variation of body length and the growth rate of body length were all increased by more sources of juvenile crayfish.The effects of parental care behavior of female Procambarus clarkii on hatching rate of eggs was studied by keeping one group of eggs attached to the female crayfishes’ pleopods while the other group was attached to test-tube brushes. The effects of infanticide behavior of female Procambarus clarkii on juveniles’ growth were studied by maintaining them with female Procambarus clarkii or without female Procambarus clarkii. The results showed that parental care behavior could increase the hatching rate significantly (P<0.05), the infanticide behavior could decrease the survival rate significantly (P<0.05) however, it had no significant effects on body length or coefficient of variation of body length (P>0.05).Crayfish show both shelter-seeking behavior and agonistic behavior. Agonistic interactions among crayfish combatants can be triggered and released by the access of shelter, which are a necessary resource for crayfish. The shadow was rarely considered as a real shelter for crayfish. In this study, we provided the Red Swamp Crayfish (Procambarus clarkii Girard) with different shadow size and shadow partition in order to test if shadow can work as a concrete shelter. Eleven different treatments designed with different shadow area and partition and2640juvenile crayfish were used. The experiments showed that the shadow effected significantly on the survival rate of juvenile crayfish. The shadow effected significantly on the survival rate of juvenile red swamp crayfish. Compared with controls, the survival rate increased with the increase of shadow area which reached more than60%(included). But the survival rate changed less when the shadow area ratio equaled to or larger than60%. The shadow area contributed less to the body weight gain and the SLC rate of the survivals. However, the growth variance of the juveniles under shadow conditions, although was not showed among different treatments of40%～100%shadow conditions, was significantly lower than those maintained without providing shadow. Under the recent experimental settings, generally, more partitioned shadow resulted in lower mortality. When40%～60%shadow area was provided, more partitioned shadow, in comparison to only one shadow, led to higher body weight gain. When the shadow area reached80%, the body weight gain decreased with thefragmentation/partition degree of the shadow. The more fragmentation/partition was provided, the less losing-chela events and the lower body weight variance occurred. Our experiments indicated that both size and partition of the shadow influenced the growth of juvenile red swamp crayfish. And this work strongly suggested that to crayfish P. clarkiii, shadow played the identical role as the concrete shelter did.This study was designed to investigate the influence of reflective environment to Procambarus clarkii on social hierarchies. In experimental groups, we put a mirror tri-prism into a pair of crayfish with established social hierarchies and in control groups we put a non-mirror tri-prism. The reflective environment has significant influence on reversible social hierarchies, dominance index in both experimental groups.The said that, the reflective environment could make the dominant weaker and the subdominant stronger. |
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