Kudoa thyrsites
1885553
224112316
2008-07-07T10:53:37Z
Geronimo20
332930
wikilink
{{Taxobox
| image = No image available.svg
| name = ''Kudoa thrysites''
| regnum = [[Animal]]ia
| phylum = [[Myxozoa]]
| classis = [[Myxosporea]]
| ordo = [[Multivalvulida]]
| familia = Kudoidae
| genus = ''Kudoa''
| species = '''''K. thrysites'''''
| binomial = ''Kudoa thrysites''
| binomial_authority = (Gilchrist, 1924)
}}
'''''Kudoa thrysites''''' is a [[myxosporea]]n [[parasite]] of [[ocean|marine]] [[fish]]es. It has a worldwide distribution, and infects a wide range of host species. This parasite is responsible for causing economic losses to the fisheries sector, by causing [[post-mortem]] "myoliquefaction", a softening of the flesh to such an extent that the fish becomes unmarketable. It is not infective to humans.
==Taxonomy==
The spores of ''K. thyrsites'' are [[stella]]te in shape, with 4 valves and 4 [[polar capsule]]s. Upon infection by the [[actinosporea]]n stage the [[sporoplasm]] migrates to a [[muscle fibre]] where it forms a [[pseudocyst]]. Within these pseudocysts are the developing spore stages.
Comparison of [[18S rDNA]] sequences of ''Kudoa'' species and other myxozoan species to determine their relationships. They show that ''Kudoa'' species are distinct from other myxozoans analyzed (''[[Myxidium]]'' sp., ''[[Myxobolus]]'' sp., and ''[[Henneguya zschokkei]]''){{Ref|Hervio}}.
''Kudoa thyrsites'' is an interesting member of this group in that apparently has very broad host specificity, infecting many fish species around the world (Table 1).
==Pathology==
Members of the [[genus]] Kudoa primarily infect [[muscle]] tissue of marine fishes, where they form nodules or pseudocysts containing a great number of individual spores. In lighter infections these pseudocysts are isolated from the fish's [[immune system]] within the muscle fibre. More intense infections can result in severe [[inflammation]] surrounding infected muscle fibres{{Ref|Kent&Poppe}}. Although apparently asymptomatic in all but heavy infections, they are associated with post-mortem degeneration of the tissue. This softening of flesh is most likely a result the release of [[proteolytic enzyme]]s by the parasite{{Ref|Tsyuku}}.
This causes losses to both [[aquaculture]] operations, for instance, where [[salmon]] are being reared in "sea-pens", and to [[Wild fisheries of the world|capture fisheries]]. Losses are both direct, through the degradation of fish products, and indirectly, through the perception of the [[consumer]] that fish from a particular area are of a lower quality.
The intensity of ''K. thyrsites'' infection is [[positive correlation|positively correlated]] with the severity of flesh softening in Atlantic salmon fillets{{Ref|Hilaire}}. Softening of flesh always occurred with heavily infected fillets, while lightly infected fillets showed no softening.
Prevention and/or control of ''K. thyrsites'' infections is problematic especially in open water netpens. Currently there are no available treatments. One approach to control may be to disrupt the life cycle in some way thereby minimizing the likelihood of infection.
{| border="1"|cellpadding="2"; cellspacing="0"; style="border-collapse:collapse; font-size:85%; float: right; margin: 10px 12px 12px 10px;""
|+'''Table 1. Distribution and species infected by ''Kudoa thrysites'''''
|-bgcolor="#efefef"
!width="100"|Location
!width="150"|Species
!width="120"|Common name
|-
|North America
|''Merluccius productus''
|[[Hake|Pacific hake]]
|-
|
|''Oncorhynchus'' spp.
|[[Salmon|Pacific salmon]]
|-
|
|''Icelinus filamentosus''
|[[Sculpin|Threadfin sculpin]]
|-
|
|''Ophiodon elongatus''
|[[Lingcod]]
|-
|
|''Aulorhychus flavidus''
|[[Tube-snout]]
|-
|
|''Salmo salar''
|[[Atlantic Salmon]]
|-
|
|''Reinhardtius stomias''
|[[Flounder|Arrowtooth Flounder]]
|-
|
|''Eopsetta jordani''
|[[Sole|Petrale sole]]
|-
|
|''Hippoglossus stenolepis''
|[[Halibut|Pacific halibut]]
|-
|
|''Microstomus pacificus''
|[[Sole|Dover sole]]
|-
|
|''Lepidopsetta bilineatus''
|[[Sole|Rock sole]]
|-
|
|''Platichthys stellatus''
|[[Flounder|Starry flounder]]
|-
|
|''Parophrys vetula''
|[[Sole|English sole]]
|-
|
|''Theragra chalcogramma''
|[[Pollock|Alaskan pollock]]
|-
|
|''Merluccius capensis''
|[[Hake|Cape hake]]
|-
|Australia
|''Engraulis australis''
|[[Anchovy|Australian anchovy]]
|-
|
|''Engraulis japonicus''
|[[Anchovy|Japanese anchovy]]
|-
|
|''Sardinella lemuru''
|[[Sardine|Bali sardinella]]
|-
|
|''Sardinops neopilchardus''
|[[Sardine|Australian pilchard]]
|-
|
|''Spratelloides delicatulus''
|[[Sprat|Blue sprat]]
|-
|
|''Coryphaena hippurus''
|[[Mahi Mahi]]
|-
|South Africa
|''Sardinops ocellatus''
|[[Sardine|South African pilchard]]
|-
|
|''Thyrsites atun''
|[[Centropomus|Snook]]
|-
|Chile
|''Paralichthys adspersus''
|[[Flounder|Fine flounder]]
|-
|Japan
|''Cypselurus'' sp.
|[[Flying fish]]
|-
|Ireland
|''Salmo salar''
|[[Atlantic Salmon]]
|-
|
|''Clupea harengus''
|[[Herring]]
|-
|Spain
|''Salmo salar''
|[[Atlantic Salmon]]
|-
|United Kingdom
|''Scomber scomber''
|[[Mackerel]]
|-
|
|''Salmo trutta''
|[[Brown trout|Sea trout]]
|-
|}
==Life cycle==
The myxosporeans have been shown to have complex life cycles using more than one host. Usually a fish and an [[oligochaete]] or [[polychaete]] worm, and in one case a [[bryozoa]]n.
The life cycle of ''K. thrysites'' is poorly understood. It has been hypothesized that ''K. thyrsites'' has an indirect life cycle involving some marine invertebrate. Experiments have shown direct transmission of the marine myxosporean ''Myxidium leei'' in [[bream|sea bream]]{{Ref|Diamant}}. However, direct transmission of K. thyrsites failed when naive fish were fed fresh myxospores{{Ref|Moran}}. If K. thyrsites does have an indirect life cycle, the intermediate host has yet to be identified.
==References ==
# {{Note|Hervio}} {{cite journal|author=Hervio, D.M.L., Kent, M.L., Khattra, J., Sakanari, J., Yokoyama, H., Devlin, R.H.| year=1997| title=Taxonomy of <u>Kudoa</u> species (Myxosporea), using a small-subunit ribosomal DNA | journal=Canadian Journal of Zoology| volume=75 | pages=2112–2119| doi=10.1139/z97-846}}
# {{Note|Kent&Poppe}} {{cite journal |author=Kent, M.L. & T.T. Poppe| year=1988| title=Diseases of netpen-reared salmonid fishes| journal=Pacific Biological Station, Nanaimo, BC.| pages=293pp.}}
# {{Note|Tsyuku}} {{cite journal| author=Tsuyuki, H., Williscroft, S.N., Kabata, Z., Whitaker, D.J.| year=1982| title=The relationship between acid and neutral protease activities and the incidence of soft cooked texture in the muscle tissue of Pacific hake (<u>Merluccius productus</u>) infected with <u>Kudoa paniformis</u> and/or <u>K. thyrsitis</u>, held for varying times under different prefreeze chilled storage conditions| journal=Canadian Technical Report on Fisheries and Aquatic Sciences |volume=1130| pages=39 pp.}}
# {{Note|Hilaire}} {{cite journal | author=St-Hilaire, S., Hill, M., Kent, M.L., Whitaker, D.J., Ribble, C. | year=1997|title=A comparative study of muscle texture and intensity of <u>Kudoa thyrsites</u> infection in farm-reared Atlantic salmon <u>Salmo salar</u> on the Pacific coast of Canada. |journal=Diseases of Aquatic Organisms|volume=31|pages=221–225|doi=10.3354/dao031221}}
# {{Note|Diamant}} {{cite journal| author=Diamant, A.|year=1997|title=Fish-to-fish transmission of a marine myxosporean|journal=Diseases of Aquatic Organisms|volume=30|pages=99–105|doi=10.3354/dao030099}}
# {{Note|Moran}} {{cite journal|author=Moran, J.D.W., Whitaker, D.J., Kent, M.L. | year=1999| title=Natural and laboratory transmission of the marine myxosporean parasite <u>Kudoa thyrsites</u> (Gilchrist, 1924) to Atlantic salmon (<u>Salmo salar</u>)| journal=Journal of Aquatic Animal Health| volume=11|pages=110–115| doi=10.1577/1548-8667(1999)011<0110:NALTOT>2.0.CO;2}}
[[Category:Myxozoa]]
[[Category:Fish diseases]]
[[Category:Veterinary parasitology]]