Unfortunately there are diseases that have evolved to thrive in these conditions that pose risks to freshwater fish.
Ichthyophthirius multifiliis (Freshwater White Spot) is a parasite that exists on the outside of a fish that can cause 100% of mortalities in an aquarium or aquaculture setting (Jiravanichpaisal et al 2004). It gets its name from the 1mm long white cysts that typically grow on the gills and body of the fish (Wu et al 2002), and each spot is a cyst comparable to grains of sugar that encloses a parasite (Nigrelli et al 1976).
I. multifiliis can become introduced into an aquarium usually by introducing contaminated fish, exchanging untreated and contaminated water into the system or using contaminated instruments in the same water body as the fish (Dickerson 2006).
As the cysts grow on the individuals gills and body, respiration becomes increasingly difficult as the cysts block water flow through the gills and because fish excrete excess mucous due to irritation from the cysts (Dickerson 2006). Wounds left by parasites also affect the fishes swimming ability making it harder to feed (Dickerson 2006).
A visual diagnosis of the fish is the fastest way to detect an I. multifiliis infection, with the stand out symptoms being the presence of white cysts, rapid operculum movements as the fish struggles to breath and anorexia due to a lack of feeding (Dickerson 2006).
Treatment is the quarantine of infected individuals into clean water until the symptoms subside-or the individual dies and/or the addition of salt into the system to a maximum of 4 parts per thousand, as freshwater fish can tolerate higher salinity than the parasite (Dickerson 2006).
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| I. multifiliis targets the gills and body |
References:
Dickerson, H 2006, 'Ichthyophthirius multifiliis and Cryptocaryon irritans (Phylum Ciliophora)', 'Fish Diseases and Disorders' pp. 116-118
Jiravanichpaisal, P. Soderhall, K. Soderhall, I 2004, 'Effect of Water Temperature on the Immune Response and Infectivity Pattern of White Spot Syndrome Virus (WSSV) in Freshwater Crayfish', 'Fish and Shellfish Immunology' vo. 17, pp. 265-275
Nigrelli, R. Pokorny, K. Ruggieri, G 1976, 'Notes on Ichthyophthirius multifiliis, a Ciliate Parasitic on Fresh-Water Fishes, with Some Remarks on Possible Physiological Races and Species', 'Transactions of the American Microscopical Society', vol. 95, pp. 607-613
Wu, J. Nishioka, T. Mori, K. Nishizawa, T. Muroga, K 2002, '
Amazingly enough (for a mouse person :) ) I am familiar with this disease. I was not aware that there were so many ways fish could get infected! 4 parts per trillion seems absolutely tiny. Approximately what salinity would this be in water (if say sea water is about 3% salt)?
ReplyDeleteHi Tasmin,
ReplyDeleteWow that is amazing!
yeah that came out wrong, i should have written 4 parts per thousand, not parts per trillion. Its great these blogs have edit buttons.
so with the average ocean salinity being about 35 grams of salt in every kilogram of seawater, this salinity would equate to 4 grams per kilogram of water or 0.4% salinity.