White necrotic tail tips in estuary seahorses, Hippocampus kuda, Bleeker

Isolation, identification, and biological control in vitro of tail rot pathogen strain from Hippocampus kuda

Tail rot disease is associated with major economic losses in the seahorse aquaculture in China. This study aimed to isolate and identify the pathogen causing tail rot disease in seahorses. Three culturable intestinal bacteria strains were isolated from Hippocampus kuda specimens with tail rot disease. Strain HL11, HL12, and HL13 were identified as Pseudoalteromonas spongiae, Bacillus subtilis and Photobacterium ganghwense based on its morphological characteristics, physiological and biochemical properties, through 16S rRNA and gyrB sequencing, respectively. Challenge experiments using these strains on healthy H. kuda and bacterial re-isolation from challenged diseased seahorses showed that the bacteria strain named HL11 induced identical pathological symptoms, indicating that it is the causative pathogen of the disease. Antibiotic-resistance tests against of 32 antibiotics revealed that HL11 was highly sensitive to 13 kinds, while exhibited intermediate susceptibility to 6, and resistance to 13 kinds. Antibacterial tests of the bioactive agents showed that HL11 was susceptible to five kinds, including tea polyphenols, lactic acid, gallic acid, allicin, and polylysine; however, it was not susceptible to the other 13 kinds of bioactive agents. The results demonstrate the potential of using bioactive agents to replace antibiotics to generate an environmentally friendly mode of culturing seahorses.

Primary Isolation and Characterization of Tenacibaculum maritimum from Chilean Atlantic Salmon Mortalities Associated with a Pseudochattonella spp. Algal Bloom

This study presents the first isolation of Tenacibaculum maritimum from farmed Atlantic Salmon Salmo salar in Chile. The isolate, designated T. maritimum Ch-2402, was isolated from gills of Atlantic Salmon at a farm located in region X, Los Lagos, Chile, during the harmful algal bloom caused by Pseudochattonella spp. in February 2016. The algal bloom is reported to have caused 40,000 metric tons of mortality in this salmon farming area. The bacterium T. maritimum, which causes tenacibaculosis, is recognized as an important pathogen of marine fish worldwide. Genetic, phylogenetic, and phenotypic characterizations were used to describe the T. maritimum Ch-2402 isolate. The isolate was similar to the type strain of T. maritimum but was genetically unique. Tenacibaculum dicentrarchi isolates were also recovered during sampling from the same farm. Based on the fact that T. maritimum has been shown to cause disease in Atlantic Salmon in other regions, the presence of this bacterium poses a potential risk of disease to fish in the Chilean aquaculture industry. Received November 6, 2016; accepted May 29, 2017.

First report of scuticociliatosis caused by Uronema sp. in ornamental reef fish imported into Brazil

Abstract Scuticociliatosis, which is caused by an opportunistic ciliate protozoan, is responsible for significant economic losses in marine ornamental fish. This study reports the occurrence of Uronema sp., which was found to be parasitizing three species of marine reef fish imported into Brazil and maintained in quarantine: Vanderbilt’s Chromis (Chromis vanderbilti), blue-green damselfish (Chromis viridis), and sea goldie (Pseudanthias squamipinnis). During the quarantine period, some fish presented with behavioral disorders and hemorrhages and ulcerative lesions on the body surface. Histopathological analysis showed hemorrhages, inflammation comprising mononuclear and granular cells in the skeletal muscle, and necrosis of the skin and the secondary lamellae of the gills, and parasites were also observed in the renal capsule. The absence of transboundary measures available to prevent the occurrence of ornamental fish diseases is also discussed.

New data on flatfish scuticociliatosis reveal that Miamiensis avidus and Philasterides dicentrarchi are different species

Scuticociliatosis is a severe disease in farmed flatfish. However, the causative agent is not always accurately identified. In this study, we identified two isolates of scuticociliates from an outbreak in cultured fine flounder Paralichthys adspersus. Scuticociliate identification was based on morphological data, examination of life stages and the use of molecular approaches. The isolates were compared with a strain of Philasterides dicentrachi from turbot Scophthalmus maximus and with a strain deposited in the American Type Culture Collection as Miamiensis avidus ATCC® 50180™. The use of morphological, biological and molecular methods enabled us to identify the isolates from the fine flouder as P. dicentrarchi. Comparison of P. dicentrachi isolates and M. avidus revealed some differences in the buccal apparatus. Unlike P. dicentrarchi, M. avidus has a life cycle with three forms: macrostomes (capable of feeding on P. dicentrarchi), microstomes and tomites. Additionally, we found differences in the 18S rRNA and α- and β-tubulin gene sequences, indicating that P. dicentrarchi and M. avidus are different species. We therefore reject the synonymy/conspecificity of the two taxa previously suggested. Finally, we suggest that a combination of morphological, biological, molecular (by multigene analysis) and serological techniques could improve the identification of scuticociliates parasites in fish.