Virginia Institute of Marine Science, P.O. Box 1346, 1375 Greate Road, Gloucester Point, VA 23062-1346, USA.
Virginia Institute of Marine Science, P.O. Box 1346, 1375 Greate Road, Gloucester Point, VA 23062-1346, USA.
J Invertebr Pathol. 2018 Feb;152:8-16. doi: 10.1016/j.jip.2018.01.003. Epub 2018 Jan 30.
The parasitic dinoflagellate Hematodinium perezi is highly prevalent in juvenile blue crabs, Callinectes sapidus, along the eastern seaboard of the USA. Although the parasite is known to kill adult crabs, the mortality rate of naturally infected juvenile crabs remains unknown. We analyzed the influence of temperature and salinity on the mortality of recently recruited blue crabs that were naturally infected with H. perezi. Over 492 juvenile crabs (infected, n = 282; uninfected controls, n = 210) were held individually in six-well plates and held at six temperatures (4, 10, 15, 20, 25, and 30 °C) or three salinities (5, 15, and 30 psu) for a maximum of 90 days. Mortality of infected crabs was 10 times higher at elevated temperatures (25 and 30 °C) and salinity (30 psu) compared to uninfected control treatments. By contrast, infected crabs exposed to mild temperatures (10, 15, and 20 °C) showed a high survival (>80%), no different than uninfected control treatments. Infected crabs at the lowest temperature (4 °C) exhibited a high mortality, but the intensity of infection was lower than in the other temperature treatments. In addition, this study revealed the optimal temperature (25 °C) and salinity (30 psu) for H. perezi to progress in its life cycle leading to sporulation in juvenile crabs; 31.6% (19/60) of crabs held under these conditions released dinospores of H. perezi after 10 days. Crabs held at other temperatures did not release dinospores over the time course of the experiment. Infected crabs were capable of molting and in most cases molted at the same frequency as uninfected crabs serving as controls. The mortality observed in this study indicates that early benthic juveniles will experience significant mortality due to H. perezi with increasing ocean temperatures and that this mortality may be a significant factor in the recruitment of blue crabs to high salinity regions.
寄生性甲藻 Hematodinium perezi 在沿美国东海岸的幼年蓝蟹 Callinectes sapidus 中高度流行。虽然已知该寄生虫会杀死成年蟹，但自然感染的幼年蟹的死亡率仍不清楚。我们分析了温度和盐度对自然感染 H. perezi 的新近招募的蓝蟹死亡率的影响。将超过 492 只幼年蟹（感染组，n=282；未感染对照组，n=210）单独放置在六孔板中，并在六个温度（4、10、15、20、25 和 30°C）或三个盐度（5、15 和 30 ppt）下保持 90 天。与未感染对照组处理相比，感染蟹在高温（25 和 30°C）和高盐度（30 ppt）下的死亡率高 10 倍。相比之下，暴露于温和温度（10、15 和 20°C）的感染蟹表现出高存活率（>80%），与未感染对照组处理无差异。在最低温度（4°C）下的感染蟹死亡率较高，但感染强度低于其他温度处理。此外，本研究揭示了 H. perezi 完成生命周期并在幼年蟹中产生孢子的最佳温度（25°C）和盐度（30 ppt）；在这些条件下饲养的 60 只蟹中有 31.6%（19/60）在 10 天后释放了 H. perezi 的游动孢子。在实验过程中，在其他温度下饲养的蟹没有释放游动孢子。感染蟹能够蜕皮，并且在大多数情况下，蜕皮频率与作为对照的未感染蟹相同。本研究中观察到的死亡率表明，随着海洋温度的升高，早期底栖幼体会因 H. perezi 而经历大量死亡，并且这种死亡率可能是蓝蟹向高盐度区域繁殖的重要因素。
