Adams Mark B, Hayward Craig J, Nowak Barbara F
Department of Fisheries and Aquaculture, Institute for Marine and Antarctic Studies, University of TasmaniaLaunceston, TAS, Australia.
Front Physiol. 2017 Mar 29;8:187. doi: 10.3389/fphys.2017.00187. eCollection 2017.
Three metazoan parasites, a monogenean and two species of copepods and are known to parasitize the gills of ranched southern bluefin tuna (SBT) and other tuna species. However, there is no detailed information describing the pathological response to infection by these parasites in this species. Wild southern bluefin tuna (approximately 3 years of age), captured and towed to a grow-out site in the waters immediately south of Port Lincoln, South Australia were subsequently sampled ( = 10) monthly from March until August 2004 during commercial harvest operations. Longitudinal sections of gill hemibranchs with attached parasites were excised and fixed for routine histology and immunohistochemistry. Reference samples were also collected from fish displaying no signs of parasitism or other grossly observable anomalies. Two morphologically distinct granulocytes were observed and putatively identified as eosinophils and mast cells. Pathology was localized to filaments upon and immediately adjacent to parasite attachment sites. Branchial cellular responses, adjunct to the attachment of by its opisthaptoral clamps, included hyperplasia and inflammation resulting in structural remodeling of branchial tissues. Inflammatory infiltrates were often dominated by putative eosinophils and lymphocytes when parasitized by and . Gill associated lymphoid tissue infiltrated the lamellar regions particularly in response to helminth infection. A variable response ranging from hemorrhage with minor hyperplasia or fibroplasia and eosinophilic inflammation to a barely discernible change was seen for gill sections harboring and . The magnitude of the host response to attachment by the latter was congruent with attachment proximity and parasite load. On the basis of the host responses reported here and the low intensity of infection observed in other associated studies these gill ectoparasites are currently considered a low risk for wild and ranched adult SBT.
已知三种后生动物寄生虫，一种单殖吸虫和两种桡足类动物寄生于养殖的南方蓝鳍金枪鱼（SBT）及其他金枪鱼品种的鳃上。然而，目前尚无关于该物种对这些寄生虫感染的病理反应的详细信息。2004年3月至8月商业捕捞期间，捕获了野生南方蓝鳍金枪鱼（约3岁），并拖至南澳大利亚林肯港以南水域的养殖场所，随后每月对其进行采样（n = 10）。切除带有附着寄生虫的鳃半鳃纵切片，固定用于常规组织学和免疫组织化学检查。还从未表现出寄生虫感染迹象或其他明显异常的鱼中采集了参考样本。观察到两种形态不同的粒细胞，并初步鉴定为嗜酸性粒细胞和肥大细胞。病理变化局限于寄生虫附着部位及其紧邻的细丝上。由后吸器夹钳附着的[此处原文似乎缺失寄生虫名称]所引发的鳃细胞反应包括增生和炎症，导致鳃组织的结构重塑。当被[此处原文似乎缺失寄生虫名称]和[此处原文似乎缺失寄生虫名称]寄生时，炎症浸润通常以推测的嗜酸性粒细胞和淋巴细胞为主。鳃相关淋巴组织浸润鳃小片区域，尤其是在对蠕虫感染的反应中。对于含有[此处原文似乎缺失寄生虫名称]和[此处原文似乎缺失寄生虫名称]的鳃切片，观察到从伴有轻微增生或纤维增生及嗜酸性炎症的出血到几乎难以察觉的变化等不同的反应。宿主对后者附着反应的程度与附着的接近程度和寄生虫负荷一致。基于此处报道的宿主反应以及其他相关研究中观察到的低感染强度，目前认为这些鳃外寄生虫对野生和养殖的成年南方蓝鳍金枪鱼构成的风险较低。
