Several species of harmful algae form blooms that are detrimental to aquatic organisms worldwide with severe economic loss to several industries. The cosmopolitan ichthyotoxic dinoflagellates and raphidophytes Karenia spp., Chattonella spp., Heterosigma spp., and Margalefidinium (Cochlodinium) polykrikoides are known to cause mass mortalities of fish and invertebrates, and the dinoflagellates Heterocapsa spp. are known to cause mass mortalities of shellfish, notably bivalve molluscs. The species K. mikimotoi, K. papilionacea, H. circularisquama, H. akashiwo, M. polykrikoides, and C. marina form recurrent harmful algal blooms (HAB) in coastal aquaculture areas of shellfish, coinciding with the reproduction seasons of natural and farmed bivalve molluscs. In the present study, their effects on eggs, fertilization, embryos, and three larval stages (D-shaped, umbo and pre-settling larvae) of a model bivalve species, the Japanese pearl oyster, Pinctada fucata martensii, are reported. The harmful algae had differential negative effects on each developmental stage, and had differential effects on larvae depending on their growth stage. Eggs were more affected by M. polykrikoides, K. mikimotoi and H. circularisquama than H. akashiwo and K. papilionacea. Fertilized eggs and developing embryos were more affected by M. polykrikoides and H. circularisquama than K. mikimotoi, K. papilionacea and H. akashiwo. Mortalities as well as abnormalities were not observed in any larval stage; however, motility of d-larvae and umbo larvae was more reduced by H. circularisquama and C. marina, than M. polykrikoides. In elder, 16 day-old larvae, all harmful algae induced a significant decrease in motility with the most severe effect observed during exposures to H. circularisquama, C. marina, H. akashiwo and M. polykrikoides. The superoxidase dismutase activity in larvae was not affected by exposure to any harmful alga; however, 6- and 16-day old larvae experienced a significant increase in GST activity following 48 h of exposures, with higher sensitivity of the elder larvae to C. marina, K. mikimotoi and M. polykrikoides. These results indicate that all tested harmful algae are differentially detrimental to the early-life development of the Japanese pearl oyster, with involvement of oxidative stress. Both M. polykrikoides and H. circularisquama were the most toxic followed by C. marina, K. mikimotoi, H. akashiwo and K. papilionacea. In addition, more developed larvae were most sensitive to these harmful algae in terms of motility-avoidance behavior and oxidative stress response, suggesting that ingestion of the harmful algae might enhance the toxicity of contact-dependent effects and dissolved extracellular compounds. The results also showed that superoxide anions were not associated with effects observed in larvae. Instead cellular detoxification was induced. The differential, stage-specific and growth-specific sublethal effects on bivalve development and recruitment also warrant further investigations of the oxidative stress and antioxidant enzyme activities in larvae of bivalves, to better address the toxicity mechanisms of ichthyotoxic HAB and their impacts on the reproduction, recruitment, and fitness of bivalve molluscs.

Summary: The harmful algae Heterocapsa circularisquama, Chattonella marina, Hetrosigma akashiwo, Karenia mikimotoi, K. papilionacea, Margalefidinium (Cochlodinium) polykrikoides differentially affect early life stages of Japanese pearl oyster and activate detoxification enzymes in feeding larvae.

几种有害藻类形成水华，这些水藻有害于全世界的水生生物，给数个行业造成严重的经济损失。大都会ichthyotoxic甲藻和raphidophytes米氏属，卡盾藻属，异属，和Margalefidinium（Cochlodinium）polykrikoides已知鱼类和无脊椎动物的原因大量死亡，和甲藻Heterocapsa属。已知会导致贝类大量死亡，尤其是双壳贝类软体动物。物种K. mikimotoi，K。papilionacea，H。circleisquama，H。akashiwo，M。polykrikoides和C. marina在贝类的沿海水产养殖区域形成有害的藻类经常性繁殖（HAB），与天然和养殖的双壳贝类软体动物的繁殖季节相吻合。在本研究中，报道了它们对典型的双壳类日本牡蛎珍珠贝Pinctada fucata martensii的卵，受精，胚胎和三个幼体阶段（D形，超薄和沉降前幼体）的影响。有害藻类在每个发育阶段均具有不同的负面影响，并且根据幼虫的生长阶段而对幼虫具有不同的影响。卵更受M. polykrikoides，K.藻和H. circularisquama比H.弯藻和K. papilionacea。受精卵和发育中胚珠受受精卵和圆纹鳞茎的影响要比三本结球菌，乳头钩端螺旋体和akashiwo受到的影响更大。在任何幼虫阶段均未观察到死亡率和异常情况。然而，运动d -larvae和鼓膜凸幼虫被更多地减少H. circularisquama和C.码头，比M. polykrikoides。在年长的16日龄幼虫中，所有有害藻类均引起运动力的显着降低，在暴露于圆形等鳞茎，滨海假丝酵母，akashiwo和多角形支原体的过程中，观察到最严重的影响。。幼虫中的过氧化物酶歧化酶活性不受暴露于任何有害藻类的影响。然而，在暴露48小时后，6天和16天大的幼虫经历了GST活性的显着增加，而大龄幼虫对C. marina，K。mikimotoi和M. polykrikoides的敏感性更高。这些结果表明，所有测试的有害藻类都对日本珍珠牡蛎的早期发育有不同的有害作用，并伴有氧化应激。既M. polykrikoides和H. circularisquama是毒性最强的，随后C.码头，K.藻，H.弯藻和K. papilionacea。此外，就运动力回避行为和氧化应激反应而言，更发达的幼虫对这些有害藻类最敏感，这表明摄入有害藻类可能会增强接触依赖性效应和溶解的细胞外化合物的毒性。结果还表明，超氧阴离子与在幼虫中观察到的作用无关。相反，诱导了细胞排毒。对双壳动物发育和募集的不同，阶段特定和生长特定的亚致死效应也值得进一步研究双壳幼虫的氧化应激和抗氧化酶活性，以更好地解决鱼鳞毒素HAB的毒性机制及其对生殖的影响，双壳软体动物的募集和适应。

简介：有害藻类异翅藻，沙门氏菌码头，赤角芥，三叶卡雷尼亚菌，乳杆菌K，乳头孢菌属（Cochlodinium）多角形藻类对日本珍珠贝的早期生命周期有不同的影响，并会激活饲喂幼虫中的排毒酶。