Lycett K A, Pitula J S
University of Maryland Eastern Shore, 1 Backbone Road, 2107 Carver Hall, Princess Anne, Maryland 21853, USA.
Dis Aquat Organ. 2017 May 11;124(3):169-179. doi: 10.3354/dao03112.
The blue crab Callinectes sapidus has seen a general decline in population levels. One factor influencing mortality is infections by Hematodinium perezi, a dinoflagellate parasite. A 2 yr study was conducted in 2014 and 2015 to monitor H. perezi DNA within the Maryland (USA) coastal bays, comparing seasonal cycles in the abundance of parasite DNA in environmental samples to parasite presence in host blue crabs. A late summer to early fall peak in H. perezi infections in blue crabs was observed, consistent with previous work. Infection intensities matched this trend, showing a slow progression of low intensity infections early in the year, with a peak in moderate and heavy infections occurring between July and September, for both years. It was hypothesized that the peak in water column occurrence would coincide with those months when infection intensities were highest in blue crabs. As the peaks in water column occurrence were in July 2014 and August-September 2015, this is consistent with sporulation being the primary contributor to environmental detection in summer months. An additional peak in environmental detection occurred in both years during the early spring months, the cause of which is currently unknown but may be related to infections in overwintering crabs or alternate hosts. Several new crustacean hosts were identified within this estuary, including grass shrimp Palaemonetes spp. and the sand shrimp Crangon septemspinosa, as well as the mud crab Dyspanopeus sayi. Improved knowledge of this disease system will allow for better management of this important fishery.
美味优游蟹（Callinectes sapidus）的种群数量总体呈下降趋势。影响其死亡率的一个因素是受到派琴虫（Hematodinium perezi）的感染，派琴虫是一种甲藻寄生虫。2014年和2015年开展了一项为期两年的研究，以监测美国马里兰州沿海海湾内的派琴虫DNA，将环境样本中寄生虫DNA丰度的季节性周期与宿主美味优游蟹体内的寄生虫存在情况进行比较。观察到美味优游蟹感染派琴虫的情况在夏末至秋初出现高峰，这与之前的研究结果一致。感染强度也符合这一趋势，显示出年初低强度感染的缓慢发展，在这两年的7月至9月间，中度和重度感染出现高峰。据推测，水柱中派琴虫出现的高峰将与美味优游蟹感染强度最高的月份相吻合。由于水柱中派琴虫出现的高峰分别在2014年7月以及2015年8月至9月，这与孢子形成是夏季环境检测的主要因素这一情况相符。在这两年的早春月份，环境检测中均出现了另一个高峰，其原因目前尚不清楚，但可能与越冬螃蟹或替代宿主的感染有关。在这个河口内还发现了几种新的甲壳类宿主，包括草虾（Palaemonetes spp.）、沙虾（Crangon septemspinosa）以及泥蟹（Dyspanopeus sayi）。对这种疾病系统的深入了解将有助于更好地管理这一重要渔业。
