Universidad Católica del Norte, Facultad de Ciencias del Mar, Larrondo 1281, Coquimbo, Chile.
J Invertebr Pathol. 2012 Sep 15;111(1):20-6. doi: 10.1016/j.jip.2012.05.005. Epub 2012 May 23.
Withering syndrome (WS) is a serious chronic disease caused by infection with the bacterium Candidatus Xenohaliotis californiensis, a Rickettsiales-like organism (WS-RLO) that affects multiple abalone species in both natural and farmed populations. However, there is no available information regarding the effects of this disease on the physiological performance of infected abalone. We studied the effect of different levels of infection on components of energy balance and physiological indices (rates of absorption and assimilation, O/N ratio, and scope for growth) in the abalone species Haliotis rufescens and Haliotis discus hannai. Juveniles were exposed to C. X. californiensis transmission for 130 days, during which time the presence/absence of WS-RLOs was evaluated by PCR (following DNA sequencing-based confirmation of 100% identity with the sequence of C. X. californiensis from California), and the prevalence and intensity of infection were evaluated via histological analysis. Among H. rufescens juveniles exposed to the bacterium, 92% became infected (positive by histology), and the intensity of infection ranged from low (degree 1) to moderate (degree 2). In contrast, no H. discus hannai juveniles were positive for WS-RLO by histology, although 23% were positive by PCR, possibly indicating incipient WS-RLO infection that did not develop during the experimental period or to mere presence of WS-RLO DNA in the sample. Infection of H. rufescens juveniles by WS-RLOs negatively affected all components of the energy balance and physiological indices, such as scope for growth and the O/N ratio, in direct relation to the degree of infection. The most strongly affected functions were the rate of ingestion, standard metabolism, and production of feces, which were reduced by 60-80% in the most highly infected individuals. The reduced energy intake in the organisms produced a strong energy imbalance such that the energy available for growth was reduced by 49% in infected organisms. In contrast, juveniles of H. discus hannai carrying the bacterium developed no infection and showed no alterations of physiological function. Our results indicate that the level of early infection by WS-RLOs may exert a negative effect on physiological activity in H. rufescens, even when the disease is not evident.
萎缩症（WS）是一种由加利福尼亚拟木贼菌（一种类似立克次体的生物（WS-RLO））感染引起的严重慢性疾病，影响天然和养殖种群中的多种鲍鱼物种。然而，目前尚无关于这种疾病对感染鲍鱼生理性能影响的信息。我们研究了不同感染水平对皱纹盘鲍和杂色鲍生理指标（吸收率和同化率、O/N 比和生长范围）的能量平衡成分的影响。幼体暴露于 C. X. californiensis 传播 130 天，在此期间通过 PCR 评估 WS-RLO 的存在/不存在（在基于 DNA 测序的 100%与加利福尼亚的 C. X. californiensis 序列一致的确认后），并通过组织学分析评估感染的流行率和强度。在暴露于细菌的皱纹盘鲍幼体中，92%感染（组织学阳性），感染强度从低（1 度）到中度（2 度）不等。相比之下，在组织学上没有杂色鲍幼体呈 WS-RLO 阳性，但 23%通过 PCR 呈阳性，可能表明存在初期 WS-RLO 感染，但在实验期间未发展或仅存在 WS-RLO DNA 在样本中。WS-RLO 感染皱纹盘鲍幼体对能量平衡和生理指标的所有成分都产生负面影响，例如生长范围和 O/N 比，与感染程度直接相关。受影响最严重的功能是摄食率、标准代谢和粪便产生，在感染最严重的个体中减少了 60-80%。生物体中能量摄入的减少导致强烈的能量失衡，以至于感染生物体中用于生长的能量减少了 49%。相比之下，携带细菌的杂色鲍幼体没有发展出感染，也没有表现出生理功能的改变。我们的结果表明，WS-RLO 的早期感染水平可能对皱纹盘鲍的生理活动产生负面影响，即使疾病不明显也是如此。
