中华绒螯蟹幼体的栖息生境选择与行为特征

为探究中华绒螯蟹在早期发育阶段对不同栖息生境的选择偏好及其行为特征，实验以长江口近岸微生境类型为基础，在室内建立了藨草、泥底、铁板沙、砾石等4种模拟生境，选取中华绒螯蟹大眼幼体、Ⅰ、Ⅲ、Ⅴ期仔蟹分别开展了对不同生境选择的行为观察和定量分析。结果显示，中华绒螯蟹大眼幼体、Ⅰ、Ⅲ、Ⅴ期仔蟹在藨草生境中分布比例最高，显著高于其他三种生境。随着仔蟹的生长发育，Ⅲ、Ⅴ期仔蟹在泥底和铁板沙生境中占比增大。在藨草生境中，中华绒螯蟹幼体具有游泳、附着藨草、表栖、埋栖等4种行为，大眼幼体和Ⅰ期仔蟹主要表现为附着藨草行为，Ⅲ期仔蟹的表栖、埋栖行为显著增加。幼体在藨草生境中的蜕壳率显著高于泥生境，而死亡率显著低于泥生境。研究表明，中华绒螯蟹幼体偏好栖息于有利于其生存、发育的藨草等植被生境中，这可能与藨草等植被生境为中华绒螯蟹幼体提供了适宜的庇护场所有关。本研究结果指出了植被生境对中华绒螯蟹幼体阶段的重要性，丰富了早期生活史资料，并为其资源保护和栖息地生态修复提供了基础参考。

Habitat selection and behavior characteristics of Chinese mitten crab (Eriocheir sinensis)

The transition from planktonic larva to benthic juvenile is a critical period for decapod crustaceans. If the habitat was suitable, the post-larval individuals will quickly settle down. In addition, individuals in different development stages may choose different habitats. Chinese mitten crab (Eriocheir sinensis) is an important economic species in China. The juvenile E. sinensis mainly live in the intertidal zone of the Yangtze Estuary, but there is no systematic study on its habitat selection patterns. Therefore, in order to explore the habitat preference of E. sinensis larvae, simulation experiments of four habitats common on Yangtze Estuary, namely Scirpus mariqueter, mud bottom, consolidated silt and gravel, were conducted in the laboratory. In addition, behavior observation and quantitative analysis of the megalopa, juvenile of E. sinensis (at stages Ⅰ, Ⅲ and Ⅴ) were carried out in different habitats. The results showed that there were significant differences in the distributions of the four stages in the four habitats (Kruskal-Wallis test, P < 0.05). The distribution proportions of megalopa (73.7%±6.8%), stage Ⅰ juvenile (78.2%±8.8%), stage Ⅲ juvenile (53.6%±8.0%) and stage Ⅴ juvenile (54.8%±6.8%) in the S. mariqueter habitat were significantly higher than other habitats (P < 0.05). The proportions of stage Ⅲ and Ⅴ juvenile in mud and consolidated silt were significantly higher than other stages (P<0.05). Juveniles had swimming, cling, epibiosis and burying behaviors in S. mariqueter habitat. Megalopa and stage Ⅰ juvenile showed cling behavior, accounting for 82.1%±5.1% and 83.3%±8.7% of the group, respectively. Only megalopa showed swimming behavior (9.0%±3.7%). For stage Ⅲ, epibiosis (44.2%±17.9%) and burying rate (36.5%±16.7%) were significantly increased (P<0.05). In addition, since it is difficult to observe the stage Ⅴ juvenile, the behavior experiment of stage Ⅴ juvenile showed no results. Figure 4 shows the cumulative percentage of molting and mortality rates of juveniles within 5 days. Feeding and habitat had significant effects on the molting rate (feeding: F=166.48, P<0.05, habitat: F=198.09, P<0.05), and the interaction between them was significant (F=21.84, P<0.05). The juveniles were found to show significantly higher molting rate in S. mariqueter habitat (feed: 86.7%±6.9%; not feed: 81.1%±5.1%) compared to the mud and empty basin (P<0.05) regardless of being fed or not. Habitat had significant effect on mortality (F=27.16, P<0.05), while feeding had and interaction didn’t (F=0.22, P>0.05 and F=1.72, P>0.05). By pairwise comparison, in feeding group, the juveniles were found to show significantly higher mortality in mud (24.4%±1.9%) compared to the S. triqueter (13.3%±3.3%) and empty basin (14.4%±1.9%). In the non-feeding group, the juveniles had in significantly higher mortality in mud (26.6%±5.7%) compared to the empty basin (17.7%±1.9%) and S. triqueter (10.0%±3.3%). The results showed that the larvae of E. sinensis showed preference for vegetation habitats such as S. mariqueter, which may be related to the shelter provided by vegetation. The results of this study indicate the importance of vegetation habitat for the larval stage of E. sinensis, enrich the early life history data, and provide basic reference for resource conservation and habitat restoration.