K^(+)、Cr^(6+)对网纹藤壶幼虫发育和存活的影响

Effects of K^(+) and Cr^(6+) on larval development and survival rate of the acorn barnacle Balanus reticulatus

以华南沿海污损生物群落优势种网纹藤壶(Balanus reticulatus)的幼虫为研究对象,探讨钾、铬2种金属离子对其幼虫存活及发育的影响。实验所用金属离子溶液是将K+和Cr6+母液添加到过滤消毒海水中配制。将活泼健壮的网纹藤壶无节幼虫置于上述溶液中,以亚心形扁藻(Platymonas subcordiformis)为饵料于30℃左右的黑暗环境中培养5d,镜检观察记录幼虫发育状况并进行统计分析。结果表明,K+对网纹藤壶幼虫发育和存活的影响均不明显;而Cr6+对幼虫发育具有一定的毒杀和抑制作用,不仅幼虫存活率低于对照组,而且金星幼虫所占百分率也低于对照组。

The acorn barnacle Balanus reticulatus plays an important role in certain marine ecological systems and is one of the most dominant fouling species in tropical and subtropical waters. Its larval development proceeds through six naupliar stages and a single cyprid stage. To understand the effects of K＋ and Cr6＋ on the larvae of the barnacle B. reticulatus, the following study on different stage larvae and their survival rate to such free ions was conducted. Adult B. reticulatus were collected from the aquaculture facilities in Dapengao of Daya Bay, Shenzen, China and egg lamellae containing late stage embryos were removed from the mantle cavities by dissection. When such lamellae were placed in a 500mL glass beaker with filtered seawater, nauplii were released within a few minutes. The nauplii were collected and transferred to 100mL beakers with 50mL filtered seawater. Larval culture was conducted over five days at the initial density of 1 larvae/mL in complete darkness at 30＋C with the green algae Platymonas subcordiformis （2.5× 105--3.0× 105 cells/ mL） added. Stock metal solutions were made up from analytical grade potassium chloride （KC1） and chromium VI oxide （ CrO3 ） in distilled water （ concentrations of stocks were lOg/L for K＋and lg/L for Cr6＋, respectively）. Five test concentrations of each metal were prepared by diluting the stock solutions in filtered seawater. The concentrations of the K＋ solutions for testing were 0.1, 1, 10, 100 and 1000mg/L. For Cr6＋ they were 0.01, 0.05, 0.1, 1 and lOmg/L, respectively. Five replicates were run for each concentration. In the tests of K＋ treatments the survival rates of larvae were 57.4% in the Control, 62.6% in the group treated by K＋at a concentration of 0.1mg/L, 58.9% at lmg/L, 58.0% at 10rag/L, 58.4% at 100mg/L and 59.9% at 1000mg/L, respectively. There was no significant difference in the larval survival rates between the Control and treatment groups （P〉 0. 05）. In the Control group, Nauplii V accounted for 52.2% and Nauplii VI 5.2%. In the group treated by K＋ at a concentration of 0.1mg/L, Nauplii V was 58.6% and Nauplii VI 4.0%; at ling/L, Nauplii V 55.0% and Nauplii VI 3.9%; at 10rag/L, Nauplii V 54.8% and Nanplii VI 3.2%; at 100rag/L, Nanplii V 56.1% and Nauplii V[ 2.3%; at 1000rag/L, Nauplii V 56.3% and Nauplii VI 3.6%. There was no significant difference in the larval survival percentages of Nanplii V and VI between the Control and treatment groups （P〉0.05）. Concerning the tests using Cr6＋ treatments the larval survival rates were 55.4% in Control, 49.0% treated by Cr6＋ at a concentration of 0.01mg/L, 45.9% at 0.05mg/L, 44.2% at 0.ling/L, 42.4% at lmg/L and 0% at 10rag/L, respectively. There was a significant difference between the Control and treatment groups （P〈0.05）. Of them, the survival percentage of naupliar V was 8.3%, naupliar VI 11.2%, and eyprid 35.9% in the Control. Treated by Cr6＋ at 0.01mg/L, the survival percentage of nanpliar V was 8.2%, naupliar VI 9.0%, and eyprid 31.8%; at 0.05mg/L, the survival percentage of nanpliar V was 13.4%, naupliar VI 15.0%, and eyprid 17.4%; at 0.1mg/L, nanpliar V was 13.4%, naupliar VI 15.0%, and eyprid 15.7%; at lmg/L, nanpliar V was 14.0%, naupliar Vl 14.0%, and eyprid 14.4%, respectively. No larvae survived the lOmg/L Cr6＋ treatment. The eyprid percentages in the groups treated by Cr6＋ were significantly less than the Control （P〈0.05）. However, compared with the Control, more larvae at the stage of the naupliar VI occurred in the treatment groups under the influence of Cr6＋ in the range from 0.05mg/L to lmg/L （P〈0.05）. According to the results gained it ean be concluded that the effect of K＋ on B. reticulatus nauplii survival rate and development was neutral, whereas there was a marked negative effect with the Cr6＋ treatments, which presented a marked inhibitory effect on larval development of the acorn barnacle B. reticulatus.