Harmful algal blooms (HABs) have had harmful effects on the health of a wide range of organisms and are becoming a noteworthy risk to fisheries, human health and wildlife around the globe. Although the lethal influences of dinoflagellate Margalefidinium / Cochlodinium polykrikoides have been well-documented for finfish, the impacts on decapod crustacean species, especially, Litopenaeus vannamei are poorly understood. Here, we examined the exposure of L. vannamei juveniles with different M. polykrikoides densities (T1: 1 × 10³, T2: 2 × 10³, T3: 3 × 10³, T4: 9 × 10³ and T5: 30 × 10³ cells ml⁻¹), in order to observe possible histological alterations in gills and hepatopancreas. After 96 h exposure, shrimp exhibited increased mortality and survival rate of juveniles in control group were meaningfully (P < 0.05) higher than treatments exposed to 9 × 10³ and 30 × 10³ cells ml⁻¹ of M. polykrikoides. The lowest survival observed in treatments T4 (95.56%) and T5 (82.20 %), respectively. The juveniles exposed to high densities of M. polykrikoides had flaccid bodies and gills were yellow in color with some black spots (melanization) in pereiopods. At the end of the experiment, shrimps’ hepatopancreas and gills exhibited various histological alterations. The irregular appearance of the tubular structure of the hepatopancreas, R- and B-cells reduction, separation of epithelium and myoepithelial layer, ruptured epithelial cells and degeneration of tubules were detected in the hepatopancreas of shrimps exposed to 30 × 10³ cells ml⁻¹. In gills of shrimp exposed to 30 × 10³ cells ml⁻¹, alterations in epithelial structure, increases in the number of intercellular hemocytes, and changes in tissue structure were observed. Finally, findings suggest that M. polykrikoides blooms can lead to significant impacts on survival and major histological alterations in gills and hepatopancreas organs when the density of M. polykrikoides was over 9 × 10³ cells ml⁻¹.

有害藻华（HABs）对多种生物的健康具有有害影响，正成为全球渔业，人类健康和野生动植物的重要风险。虽然甲藻的致命影响Margalefidinium / Cochlodinium polykrikoides已经充分证明了鱼类，虾蟹上的甲壳类动物的影响，特别是南美白对虾却知之甚少。在这里，我们检查了不同密度的多核克氏杆菌（M. polykrikoides）密度的南美白对虾（T1：1×10 ³，T2：2×10 ³，T3：3×10 ³，T4：9×10 ³和T5：30× 10 ³细胞ml ^-1），以观察possible和肝胰腺可能的组织学改变。暴露96 h后，对照组虾的死亡率和存活率均显着高于对照组（P <0.05）（P <0.05），高于暴露于9×10 ³和30×10 ³细胞ml ^-1的多核分支杆菌的处理。分别在处理T4（95.56％）和T5（82.20％）中观察到最低的存活率。暴露于高密度多核克雷伯氏菌的幼鱼有脆弱的身体，g的颜色是黄色的，在脚足类动物中有一些黑点（黑色化）。实验结束时，虾的肝胰脏和腮表现出各种组织学改变。在暴露于30×10 ³细胞ml ^-1的虾肝胰腺中，检测到肝胰脏的管状结构不规则外观，R和B细胞减少，上皮和肌上皮层分离，上皮细胞破裂以及肾小管变性。。在暴露于30×10 ³细胞ml ^-1的虾g中，观察到上皮结构的改变，细胞间血细胞的数量增加以及组织结构的变化。最后，发现表明多核克氏杆菌当多核分支杆菌的密度超过9×10 ³细胞ml ^-1时，水华可对can和肝胰腺器官的存活和主要组织学改变产生重大影响。