Dietz T H, Lessard D, Silverman H, Lynn J W
Biol Bull. 1994 Aug;187(1):76-83. doi: 10.2307/1542167.
Zebra mussels (Dreissena polymorpha) are unusual in that they cannot survive in Mg-deficient water. Analysis of blood samples from mussels obtained in the field indicated a Mg concentration of 1.5-2.0 mM immediately after animal collection. However, Mg concentration in the blood decreased rapidly when the mussels were transferred to Mg-free artificial pondwater (PW); the t1/2 was 24 h. Blood Mg decreased to the limits of detection within 2 weeks, and the time to 50% mortality was about 17 days in Mg-free PW. When Mg-depleted specimens of D. polymorpha were returned to PW containing Mg, the net flux was 3 μmol Mg (g dry tissue.h)-1, and blood Mg concentration was restored within a day to 0.4-0.6 mM. Mussels depleted of Mg did not survive beyond 51 days. When mussels were acclimated to K-free pondwater (containing Mg), their osmoregulatory ability was impaired, and the total solute of the blood dropped from 30-36 to 21-24 mosm, with blood Na and Cl concentrations declining 30-50%. This ion-depleted condition was reversed within 45 h upon return of K to the pondwater bathing medium. D. polymorpha individuals were unable to survive beyond 5 days in deionized water and required minimal concentrations of Na, Cl, K, and Mg for prolonged storage (>51 days) under laboratory conditions. Mussels survived Ca-deficient solutions for more than 51 days, presumably because they were able to mobilize Ca from internal stores (shell) to maintain blood calcium at 1 mM.
斑马贻贝（多形饰贝）与众不同之处在于它们无法在缺镁的水中存活。对野外采集的贻贝血液样本进行分析表明，采集后动物体内镁浓度立即为1.5 - 2.0 mM。然而，当贻贝转移到无镁的人工池塘水（PW）中时，血液中的镁浓度迅速下降；半衰期为24小时。血液中的镁在2周内降至检测限，在无镁的PW中，50%死亡率的时间约为17天。当缺镁的多形饰贝样本回到含镁的PW中时，净通量为3 μmol镁/（克干组织·小时），血液镁浓度在一天内恢复到0.4 - 0.6 mM。缺镁的贻贝存活不超过51天。当贻贝适应无钾的池塘水（含镁）时，它们的渗透调节能力受损，血液中的总溶质从30 - 36 mosm降至21 - 24 mosm，血液中的钠和氯浓度下降30 - 50%。当向沐浴介质的池塘水中重新添加钾后，这种离子缺乏状态在45小时内得到逆转。多形饰贝个体在去离子水中存活不超过5天，在实验室条件下长期保存（>51天）需要最低浓度的钠、氯、钾和镁。贻贝在缺钙溶液中存活超过51天，大概是因为它们能够从内部储存（贝壳）中调动钙，以将血钙维持在1 mM。
