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

Abstract

White discoloration of the tail is a not seldom occurring phenomenon among seahorses kept in ornamental aquaria. In this study, three sea horses (Hippocampus kuda) presenting white patches on the distal part of the trunk and greyish-white necrotic tail tips were examined. Wet mount preparations of these lesions revealed ovoid to elongated ciliated protozoan structures. These ciliates could not be identified to species level but resembled species of the genus Uronema (Scuticociliatida). Samples of the affected skin were inoculated onto Marine agar (Difco) and Flexibacter maritimus medium (FMM, according to Pazos et al., 1996). After 36h of incubation at 25°C, pale orange, convex colonies with a smooth surface appeared on both Marine agar and FMM in all sea horse tails. Gram-staining of these colonies showed Gram-negative, long (up to 8µm in length), slender bacterial cells. Biochemical tests designated these motile bacteria as non-fermenting, oxidase and catalase positive and resistant to the vibriostatic agent 0/129. Sequence analysis of the 16SrRNA gene is on-going. Histological examination of the tail of two animals showed an ulcerative dermatitis consisting of desquamation/disappearance of the epidermis covered with necrotic debris. The latter contained numerous clusters of long (up to 8µm in length) slender bacteria, which were also invading the subcutaneous tissue. At these sites, an increase of proteoglycans, mild proliferation of blood vessels, limited to absent inflammation and invasion was noted. In areas where the epidermis was still intact, neutrophilic pustular lesions without bacterial infiltration were visible. In the third seahorse tail a granulomatous dermatitis was present. Bacteria (including acid-fast bacteria in Ziehl-Neelsen stained histological sections) were not observed. Scuticociliatosis caused by ciliates belonging to the order Scuticociliatida, is recognized as an emerging problem inflicting significant economic losses in aquaculture industry worldwide, for example, in the olive flounder farms in South Korea (Harikrishnan et al., 2010). Heavy infections in Atlantic and Pacific marine fishes kept in aquaria were also reported. The significance of the isolated bacterial strain in the pathology described above remains to be elucidated and will largely depend on its ultimate identification.

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

“…Scuticociliatosis is frequently accompanied by bacterial infection, as previously reported in the seahorse Hippocampus kuda (DECLERCQ et al, 2014). Mortality in Japanese flounder can reach 70-80%, as reported by Moustafa et al (2010a).…”

“…Pathogenicity caused by this parasite is more severe in environments with high levels of bacteria, nutrients, and organic matter (URRUTXURTU et al, 2003). It can be found parasitizing both farmed and ornamental marine fish (AZAD et al, 2007;DECLERCQ et al, 2014).…”

TLR2 gene in seahorse brood pouch plays key functional roles in LPS‐induced antibacterial responses

“…Paternal transgenerational immune priming in the brood pouch is vital for the proper development of embryos (Cristina, K., Wong, B.B.M., & Lieschke, G.J., ; Roth, Klein, Beemelmanns, Scharsack, & Reusch, ). Disease, especially during reproductive periods, is a bottleneck in seahorse aquaculture (Declercq et al, ; Qin, Zhang, Zhang, et al, ; Wang, Zhang, Qin, Luo, & Lin, ). During male pregnancy, the embryos in the brood pouch are frequently infected by pathogenic bacteria (LePage, ; Sanaye et al, ).…”

Disseminated nocardiosis associated with the isolation of Nocardia nova in a longsnout seahorse Hippocampus reidi (Ginsburg)

“…; Declercq et al . ). This report details histologic findings associated with a case of nocardiosis in a longsnout seahorse caused by Nocardia nova , a previously unreported agent in fish.…”