海洋生态与环境科学重点实验室知识库

脉红螺（Rapana venosa），是我国重要的经济贝类，但在黑海、亚得里亚海和爱琴海等地却是生物入侵种，并且严重破坏当地的双壳贝类。在脉红螺生活史中，浮游幼虫需要经过附着变态形成稚螺，稚螺经过生长发育后形成成螺。但是，在浮游幼虫附着变态过程中，幼虫表现出高死亡率和低变态率等问题，稚螺生长过程中同样具有高死亡率的问题，这些问题直接关系到贝类种群的资源变动，严重限制了脉红螺人工育苗进程。脉红螺在幼虫附着变态和稚螺早期发育阶段表现出多种行为，与其附着变态成功与否和稚螺的高死亡率密切相关。脉红螺行为是指脉红螺在个体水平上对外界环境或者自身生理状况的变化而做出的适应性反应，多数行为是动态的，对脉红螺的生存具有重要意义，其研究的对象是脉红螺在生存中所展现的不同行为及其背后的规律。

本研究以脉红螺浮游幼虫的附着变态行为、残食行为、稚螺对食物的感知行为和潜沙行为以及与附着变态行为、残食行为和感知行为相关的齿舌为研究对象。研究了光照、牡蛎多糖和不同贝类等对脉红螺附着变态的影响，研究了脉红螺齿舌的产生时期及形态特征，解决了脉红螺苗种繁育过程中变态率低的难题；研究了稚螺的残食方式，行为特征以及饵料、稚螺的规格和密度等因素对其残食行为的影响，找到了解决残食的方法；研究了稚螺在静水和不同水流环境下对食物的感知能力；研究了温度、溶解氧、底质粒径和稚螺规格等因素对稚螺潜沙行为的影响，显著提高了稚螺中间培育成活率。对脉红螺早期发育阶段的研究，对阐明脉红螺种群变化和资源恢复以及提高育苗效率具有重要的理论和现实意义。主要研究结果如下：

1. 脉红螺浮游幼虫附着变态行为

观察了脉红螺浮游幼虫附着变态的行为特征，研究了附着基、光照、饵料和牡蛎多糖等因素对幼虫附着变态的影响，研究了脉红螺齿舌发育及形态结构。结果表明：在四螺层中后期投放附有牡蛎稚贝的扇贝片可以显著提高幼虫附着变态率；黑暗环境有利于幼虫变态；贝类及其分泌物可显著诱导幼虫附着变态，适宜浓度的牡蛎多糖可诱导幼虫附着变态。脉红螺的齿舌产生于变态之前的四螺层时期，为幼虫附着变态时钻孔摄食贝类做准备。齿舌带上每一横排有3枚齿舌片：中央齿1枚，有3个小齿；侧齿1对，镰刀状；无缘齿；齿式为1：1：1。

2. 脉红螺稚螺残食行为

研究了稚螺的残食行为特征、影响因素以及找到了解决稚螺残食的方法。发现稚螺两种残食方式：一是1.5-5mm稚螺通过钻孔残食，二是大小5-10mm稚螺之间通过钻孔（86.4%）和包裹壳口（13.6%）残食，查明残食方式与猎物和捕食者壳高的关系。发现了稚螺存在四处不同的钻孔位置，捕食者和猎物的壳高之比影响了钻孔位置的选择，发现了完全钻孔、不完全钻孔和多个钻孔等不同钻孔模式。查明了稚螺规格、饵料和密度对残食行为的影响，结果为小规格的稚螺、饥饿和高密度会显著增加稚螺的残食率。根据残食行为的影响因素，找到解决稚螺残食的有效方法：及时投喂饵料和控制培育密度是降低脉红螺稚螺残食的重要方法，菲律宾蛤仔稚贝和寻氏肌蛤等壳薄，适用于饵料，小规格稚螺易残食，应在变态后及时投喂饵料。

3. 脉红螺稚螺感知行为

研究了脉红螺稚螺在静水和流水环境中对猎物的感知能力，发现在静水环境中，距离会显著减弱稚螺对猎物的感知能力，在猎物位于上游的实验中，发现水流会显著增强其感知能力，且水流的作用消除了距离的影响，在猎物位于下游的实验中，发现稚螺很难感知并摄食食物，表明了稚螺利用猎物释放的化学因子感知并定位猎物的行为。同时，稚螺搜寻猎物的时间同样受到水流的影响，搜寻时间长短关系为：猎物位于上游的实验<静水实验<猎物位于下游的实验。研究了水流速度和稚螺规格对稚螺感知行为的影响，结果发现不同水流速度不会显著影响稚螺的感知行为，但是小规格的稚螺具有更高的感知率和更短的感知时间。

4. 脉红螺稚螺潜沙行为

稚螺通过潜沙来捕获食物和躲避敌害。研究了温度、溶解氧、底质粒径和稚螺规格等因素对稚螺潜沙行为的影响，结果发现随着温度降低，稚螺的潜沙率显著提高；溶解氧显著影响稚螺的潜沙行为，溶解氧较高时（≥6mg/L），稚螺具有明显潜沙行为，溶解氧降低，稚螺会减少潜沙行为；底质粒径同样影响稚螺的潜沙行为，稚螺在小粒径沙中的潜沙时间最短；不同规格的稚螺潜沙行为存在差异，大规格的稚螺潜沙能力更强。实验发现小规格稚螺（壳高<2cm）在水温低于15℃时具有明显的脱壳行为，小规格稚螺可以通过潜入沙中来降低脱壳率。

Rapana venosa is an important economic shellfish in China, but it is an invasive species in the Black Sea, Adriatic Sea and Aegean Sea, and seriously destroys the local bivalve shellfish. In the life cycle, zooplankton larvae need to undergo settlement and metamorphosis into juvenile snails, and juvenile snails become adult snails after growth and development. However, in the process of settlement and metamorphosis of zooplankton larvae, the larvae show high mortality rate and low rate of metamorphosis, as well as the high mortality rate in the growth process of juvenile snails. These problems are directly related to the resource change of shellfish population. The artificial breeding process of R. venosa was seriously restricted. There are many behaviors in larval settlement and metamorphosis and early development of juvenile snail, which is closely related to the success of settlement and metamorphosis and the high mortality rate of juvenile snail. The behavior of the snail refers to the adaptive response of the snail to the changes of the external environment or its own physiological condition at the individual level. Most of the behaviors are dynamic, and it is of great significance to the survival of the snail. The object of the study is the different behaviors and the laws behind the survival of the snail.

In this study, the settlement and metamorphosis behavior, cannibalistic behavior, perceptual behavior and burrowing behavior of juvenile snails, as well as the radula related to these behaviors, were studied. The effects of light, oyster polysaccharide and different shellfish on the settlement and metamorphosis of the snail were studied in this paper and the generation period and morphological characteristics of the radula were studied. The problem of low rate of metamorphosis in the breeding process was solved; the effects of cannibalistic mode, behavior characteristics, feed, size and density of juvenile snail on its cannibalistic behavior were studied, and the methods to solve the cannibalism were found; the perceptual ability of juvenile snail to food in static water and different water flow environment was studied; the effects of temperature, dissolved oxygen, particle size of substrate and size of juvenile snail on the burrowing behavior of juvenile snail were studied, and the survival rate of juvenile snail was significantly increased. The study on the early development stages of R. venosa has important theoretical and practical significance for elucidating the population change and the recovery of resources and improving the efficiency of seedling raising. The main findings are as follows:

1. The settlement and metamorphosis behavior

The behavior characteristics of a settlement and metamorphosis of zooplankton larvae of R. venosa were observed, and the effects of attachment bases, light, food and oyster polysaccharide on the settlement and metamorphosis of larvae were studied. The development and morphological structure of radula were studied. The results showed that scallop shells with oyster juveniles could significantly increase the rate of larval settlement and metamorphosis in the middle and late stage of the middle and late 4 spiral whorls, and the dark environment was beneficial to larval metamorphosis. Shellfish and their exudates can significantly induce larval settlement and metamorphosis, and suitable concentration of oyster polysaccharide can induce larval settlement and metamorphosis. Radula originated in the stage of 4 spiral whorls, in preparation for drilling holes to feed shellfish when larvae settlement and metamorphosis. Each transverse row of the radula band has three pieces of tongue, including one central tooth （tridentate, central tip protruding）; one pair of lateral teeth （sickle-shaped）; no marginal tooth, teeth type is 1:1:1.

2. Cannibalistic behavior

The characteristics of cannibalistic behavior, the influencing factors and the methods to solve cannibalistic behavior of juvenile snail were studied.Two ways of cannibalism of juvenile snails were found: 1.5-5mm through hole-drilling, and 2.5-10mm through hole-drilling （86.4%） and enveloping （13.6%）. Finded out the relationship between cannibalistic methods and the shell length ratio of prey to predator. It was found that there were four different drilling locations in juvenile snails. The ratio of shell length between predator and prey affected the selection of drilling locations. Different drilling patterns, such as complete hole-drilling, incomplete hole-drilling and multiple hole-drilling, were found. Small size, starvation and high density of juvenile snails significantly increased the cannibalism rate of juvenile snails. We found effective ways to solve the cannibalism: timely feeding of bait and controlling the cultivation density are important ways to reduce cannibalism. The shell of juvenile clams such as Ruditapes philippinarum and Meretrix vulgaris are thin and suitable for bait. The small size of juvenile snails are prone to cannibalism, so they should be fed timely after metamorphosis.

3. Perceptual behavior

The perception of prey of the juvenile snail in static water and flowing water was studied. It was found that in still water environment, distance significantly reduced the perception ability of juveniles to prey. In upstream prey experiment, it was found that flow could significantly enhance the perception ability of juveniles, and the effect of water flow eliminated the influence of distance. In downstream prey experiment, it was found that juveniles were difficult to perceive prey. Results indicate that juveniles use chemical cues released by prey to perceive and locate their prey. At the same time, the time of hunting for prey by juveniles is also affected by water flow. The relationship between the time of hunting is as follows: upstream prey experiment < still water < downstream prey experiment. Different water velocity did not significantly affect the perception behavior of juveniles, but the smaller size of juveniles had higher perception rate and shorter perception time.

4. Burrowing behavior

Juvenile snails capture food and avoid enemies through burrowing sand. The effects of temperature, dissolved oxygen, sediment size and size of juvenile snails on burrowing behavior were studied. The results showed that burrowing rate of juvenile snails increased significantly with the decrease of temperature; dissolved oxygen significantly affected burrowing behavior of juveniles. When dissolved oxygen was higher （>6mg/L）, the juveniles had obvious burrowing behavior, the dissolved oxygen decreased, the juveniles would reduce burrowing behavior. Substrate size also affects the burrowing behavior of juveniles, and the shortest burrowing time of juveniles is in the small size sediment. The burrowing behavior of juvenile snails with different sizes is different, and large-size juveniles have strong burrowing capacity. It was found that small-sized snails （shell height < 2cm） exhibited obvious shelling behavior when water temperature was below 15 C. Small-sized snails could reduce shelling rate by submerging in sand.