Describing factors behind the mortality of juvenile seahorses, Hippocampus kuda (yellow seahorse), in captive condition

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Research Paper 01/07/2019
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Describing factors behind the mortality of juvenile seahorses, Hippocampus kuda (yellow seahorse), in captive condition

Hanifa Jemimah Samsa, Sharon Rose Tabugo
Int. J. Biosci.15( 1), 226-235, July 2019.
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Seahorse aquaculture succumb to a variety of drawbacks such as infections and diseases. Mortality rate and cause of diseases of juveniles remained a dilemma. In this study, cause of mortality of healthy 4-day old juvenile seahorses in captivity, Hippocampus kuda, were investigated. Pregnant male H. kuda donated from fishermen and brought to the laboratory gave birth to juveniles which contacted an infection leading to mass mortality. The infection was characterized by loss of motility and occurrence of thick bacterial sludge around whole bodies of seahorses, amassing in the base of the raising tanks. Dead juvenile seahorses (n=266) were subjected to postmortem examination. Morphological microscopic examination of deceased bodies, characterization and identification of bacterial isolates from water samples in rearing tanks were done. Morphological examination revealed no unusual noticeable signs in the bodies. However, bacterial samples collected, isolated and sub-cultured from water samples of rearing tanks revealed two distinct bacterial isolates and both tested as gram-negative with circular, smooth, and creamy-colored colonies. Moreover, DNA extraction and barcoding based on 16s rDNA gene sequencing identified both isolates as Halomonas sp. and Cobetia sp. respectively, and may be responsible for the infection and high mortality as observed. This study takes precedence in documenting and identifying bacteria aside from the genus Vibrio as stated in literatures, behind the mortality of juvenile seahorses in captivity.


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