All are carnivorous, capturing prey with specialized stinging cells, called nematocysts. There are perhaps 1000 species of hydro- and scyphomedusae, probably with more to be discovered, especially in deep or polar waters. Since the morphology and life history of all three groups is broadly similar, it is practical to treat them together here. What are commonly called jellyfish are medusae belonging to three Classes of the Cnidaria - the Hydrozoa, the Scyphozoa, and the Cubozoa. The phylum Cnidaria has many gelatinous representatives, comprising various groups of medusae and the strictly oceanic siphonophores (see below). Harbison, in Encyclopedia of Ocean Sciences, 2001 Medusae This bacterium is common to farmed fish and has also been found on parasitic sea lice ( Barker et al., 2009) however, importantly it may have the potential to exacerbate jellyfish-induced gill damage ( Rodger, 2007) as it has been shown to be a secondary opportunistic pathogen ( Handlinger et al., 1997). quadrata and on the gills of salmon from a Scottish salmon farm ( Ferguson et al., 2010). These filamentous bacteria were found on both the manubrium of P. quadrata as a potential vector for the bacterial pathogen Tenacibaculum maritimum. quadrata in their stomach contents ( Bruno and Ellis, 1985). Histopathological examination revealed severe epithelial stripping and necrosis of the lamellae amongst other damage and some of the fish were reported to have up to 40 P. In the 1980s 1500 salmon died at farms on the Shetland Isles, Scotland. The neritic medusae of Phialella quadrata have been implicated in fish kill events and as a vector of bacterial gill disease. This species has also been recently linked to more chronic mortalities and severe gill damage at a salmon farm in Ireland ( Baxter et al., 2011a). corona (~ 0.5–20 mm) medusae was implicated as the causative agent in the mortality of ~ 900 000 salmon at Scottish aquaculture sites in August/September 1997 ( Båmstedt et al., 1998) and again in 2002 when there were around 650 000 mortalities in two days ( Rodger et al., 2011a). (courtesy of Jana Guenther)Ī bloom of holoplanktonic S. Ectopleura larynx hydroids fouling aquaculture netting.
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