| Saprolegnia |
| Scientific classification |
| Phylum: |
Heterokontophyta |
| Class: |
Oomycota |
| Order: |
Saprolegniales |
| Family: |
Saprolegniaceae |
| Genus: |
Saprolegnia |
| Species |
|
S. australis
S. ferax
S. declina
S. longicaulis
S. mixta
S. parasitica
S. sporangium
S. variabilis
|
Saprolegnia is a genus of protozoans often called "cotton moulds" because of the characteristic white or grey fibrous patches they form. Current taxonomy puts Saprolegnia as a genus of the heterokonts in the order Saprolegniales.
Contents
- 1 Habits
- 2 Reproduction
- 3 Characteristics of infection
- 4 References
- 5 Other sites
Habits
Saprolegnia, like most oomycetes, is both a saprotroph and necrotroph. Typically feeding on waste from fish or other dead cells, they will also take advantage of creatures that have been injured. An infection is known as oomycosis
Saprolegnia is tolerant to a wide range of temperature, 3°C to 33°C, but is more prevalent in lower temperatures. While it is found most frequently in freshwater, it will also tolerate brackish water and even moist soil.
Saprolegnia filaments (hyphae) are long with rounded ends, containing the zoospores. Saprolegnia generally travels in colonies consisting of one or more species. They first form a mass of individual hyphae. When the mass of hyphae grows large enough in size to be seen without use of a microscope, it can be called a mycelium. Colonies are generally white in color, though they may turn grey under the precesence of bacteria or other debris which has become caught in the fibrous mass.
Reproduction
It has a diploid life cycle which includes both sexual and asexual reproduction. In the asexual phase, a spore of Saprolegnia releases zoospores. Within a few minutes, this zoospore will encyst, germinate and release another zoospore. This second zoospore has a longer cycle during which most dispersal happens; it will continue to encyst and release a new spore in a process called polyplanetism until it finds a suitable substrate. When a suitable medium is located, the hairs surrounding the spore will lock onto the substrate so that the sexual reproduction phase can start. It is also during this stage of polyplanetism that the Saprolegnia are capable of causing infection; the most pathogenic species have tiny hooks at the end of their hairs to enhance their infectious ability.
Once firmly attached, sexual reproduction begins with the production of male and female gametangium, antheridia and oogonium respectively. These unite and fuse together via fertilization tubes. The zygote produced is named an oospore.
Characteristics of infection
Saprolegnia is generally a secondary pathogen, though in the right circumstances, it can act as primary. It most frequently targets fish, both in the wild and in tank environments. Through necrosis of the skin, Saprolegnia will spread across the surface of its host as a cotton-like film. Though it often stays in the epidermal layers, the mould does not appear to be tissue specific. A Saprolegnia infection is usually fatal, eventually causing hemodilution, though the time to death varies depending on the initial site of the infection, rate of growth and the ability of the organism to withstand the stress of the infection.
The extensive mortalities of salmon and migratory trout in the rivers of western Europe in the 1970s and 1980s in the UDN outbreak were probably almost all ultimately caused by the secondary Saprolegnia infections.
Historial evidence suggest the Saprolegnia species affecting Australian freshwater fish may be an introduced strain, imported in the 1800s with exotic fish species.
References
- Bruno, D.W., and Wood, B.P. (1994). Saprolegnia and other Oomycetes. CABI Publishing
- Meyer, F.P. (1991). Aquaculture disease and health management.
Other sites
- Saprolegnia mixta - video
- Genetic breakdown - Saprolegnia ferax
- Saprolegnia - The Scottish Government: Marine and Fisheries
|
Fish diseases and parasites
|
|
| Pathogens |
- Aeromonas salmonicida
- Columnaris
- Enteric redmouth
- Fin rot
- Fish dropsy
- Flavobacterium
- Hematopoietic necrosis
- Heterosigma akashiwo
- Hole in the head
- Hypodermal and hematopoietic necrosis
- Infectious pancreatic necrosis
- Koi herpes virus
- Mycobacterium marinum
- Novirhabdovirus
- Pfiesteria piscicida
- Photobacterium damselae ssp piscicida
- Salmon anemia
- Streptococcus iniae
- Spring viraemia of carp
- Taura syndrome
- UDN
- VHS
- White spot
- Yellowhead
|
|
|
| Parasites |
- Abergasilus
- Amoebic gill disease
- Anisakis
- Carp lice
- Ceratomyxa shasta
- Clinostomum marginatum
- Dactylogyrus vastator
- Diphyllobothrium
- Cymothoa exigua
- Eustrongylidosis
- Epizootic ulcerative syndrome
- Flukes
- Glugea
- Gyrodactylus salaris
- Henneguya zschokkei
- Ich (freshwater)
- Ich (marine)
- Kudoa thyrsites
- Lernaeocera branchialis
- Microsporidia
- Monogenea
- Myxobolus cerebralis
- Myxosporea
- Nanophyetus salmincola
- Pseudorhabdosynochus spp.
- Salmon lice
- Saprolegnia
- Schistocephalus solidus
- Sea louse
- Sphaerothecum destruens
- Swim bladder disease
- Tetracapsuloides bryosalmonae
- Velvet
- Xenoma
|
|
| Fish groups |
- Diseases and parasites in cod
- Diseases and parasites in salmon
- Disease in ornamental fish
- List of aquarium diseases
|
|
| Related topics |
- Amnesic shellfish poisoning
- Brevetoxin
- Ciguatera
- Diarrheal shellfish poisoning
- Fish kill
- Neurotoxic shellfish poisoning
- Paralytic shellfish poisoning
- Saxitoxin
|
|
