血卵涡鞭虫感染三疣梭子蟹的病原形态学及组织病理学变化

血卵涡鞭虫是一类主要感染海产甲壳类的致病性寄生性甲藻。近年来,该寄生性病原在我国沿海主要经济蟹类养殖区域流行性发病,给当地蟹类养殖业造成了严重经济损失。为厘清血卵涡鞭虫的生活史形态,了解宿主的病理损伤机制,本文通过血涂片法和HE染色法系统研究了感染过程中该寄生虫的形态变化和宿主的组织病理变化。结果表明,血卵涡鞭虫在感染过程中经历丝状滋养体、单核/双核/多核滋养体、团聚体、蛛网状滋养体、孢子前细胞及孢子等不同生活史阶段。感染导致三疣梭子蟹发生系统性病理变化,肝胰腺、心脏、鳃、肌肉等器官和组织在不同感染阶段均发生相应程度的组织病理变化,主要表现为体细胞破损或坏死、细胞间隙模糊、疏松结缔组织充斥大量寄生虫细胞。最终由于寄生虫在宿主主要器官组织间隙内大量增殖,导致重度感染的梭子蟹器官或组织功能破坏、丧失而死亡。

MORPHOLOGY AND HISTOPATHOLOGY OF PARASITIC DINOFLAGELLATE HEMATODINIUM SP. INFECTING PORTUNUS TRITUBERCULATUS

Parasitic dinoflagellates in the genus Hematodinium are serious infectious pathogens causing epidemic disease in marine crustacean worldwide.In 2004, Hematodinium sp.infections were observed firstly in cultured swimming crabs Portunus trituberculatus in Zhejiang, China.Hematodinium sp.was identified to be the major causative pathogen of the "milky disease" periodically occurred along the coastal areas of China, and had caused heavyt economic losses to commercial aquaculture.To clarify the life stages of Hematodinium sp.and its consequent effect to hosts, we investigated the morphology of the parasite and histopathology of swimming crabs at different stages of parasitic infections using a blood smear and pathological assay.Different forms of Hematodinium sp.were identified in both hemolymph and major tissues of infected crabs, including single-nucleate, bi-nucleate and multi-nucleate trophonts, clump colony, arachnoid trophonts, prespores, and spores.Histopathology indicated that Hematodinium sp.caused systemic infections to its hosts, resulting in overt pathological alterations in hepatopancreas, heart, gills, and muscles.Cellular damage, necrosis, blurred boundary of epidermal cells, changing in tissue structure were frequently observed in early, middle, and late infection stages, together with infiltration of large amounts of parasite cells in hemolymph or hemocoels of major tissues.The systemic infections of Hematodinium sp.in P.trituberculatus result in malfunction or dysfunction of major organs, and eventually death of affected hosts.