Cherax tenuimanus: Difference between revisions

 

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””’Cherax tenuimanus””’, known as the ”’Hairy marron”’ or ”’Margaret River marron”’, is one of two species of [[crayfish]] in [[Southwestern Australia]] known as [[marron]]. It occupies a narrow range within the southwestern biogeographical region of [[Margaret River, Western Australia|Margaret River]]. It is currently listed as [[critically endangered]] on the [[IUCN Red List]], because of the threat from the yabbie, ”[[Cherax albidus]]”, which was introduced to its habitat.<ref name=”iucn status 20 November 2021″ />

””’Cherax tenuimanus””’, known as the ”’Hairy marron”’ or ”’Margaret River marron”’, is one of two species of [[crayfish]] in [[Southwestern Australia]] known as [[marron]]. It occupies a narrow range within the southwestern biogeographical region of [[Margaret River, Western Australia|Margaret River]]. It is currently listed as [[critically endangered]] on the [[IUCN Red List]], because of the threat from the , ”[[Cherax albidus]]”, which was introduced to its habitat.<ref name=”iucn status 20 November 2021″ />

Recent studies have shown that adding mannanoligosaccharide (Bio-Mos) to the diet of ”Cherax tenuimanus” can increase their immunity and rate of survival.<ref name=”:1″>{{cite journal |last1=Sang |first1=Huynh |title=Dietary supplementation of mannan oligosaccharide improves the immune responses and survival of marron, Cherax tenuimanus (Smith, 1912) when challenged with different stressors |journal=Fish and Selfish Immunology |date=August 2009 |volume=27 |issue=2 |pages=341–348 |doi=10.1016/j.fsi.2009.06.003 |pmid=19539033 }}</ref><ref>{{Cite journal|last1=Sang|first1=Huynh Minh|last2=Ky|first2=Le Trung|last3=Fotedar|first3=Ravi|date=2009-08-01|title=Dietary supplementation of mannan oligosaccharide improves the immune responses and survival of marron, Cherax tenuimanus (Smith, 1912) when challenged with different stressors|url=http://www.sciencedirect.com/science/article/pii/S1050464809001995|journal=Fish & Shellfish Immunology|language=en|volume=27|issue=2|pages=341–348|doi=10.1016/j.fsi.2009.06.003|pmid=19539033|issn=1050-4648|url-access=subscription}}</ref>

Recent studies have shown that adding mannanoligosaccharide (Bio-Mos) to the diet of ”Cherax tenuimanus” can increase their immunity and rate of survival.<ref name=”:1″>{{cite journal |last1=Sang |first1=Huynh |title=Dietary supplementation of mannan oligosaccharide improves the immune responses and survival of marron, Cherax tenuimanus (Smith, 1912) when challenged with different stressors |journal=Fish and Selfish Immunology |date=August 2009 |volume=27 |issue=2 |pages=341–348 |doi=10.1016/j.fsi.2009.06.003 |pmid=19539033 }}</ref><ref>{{Cite journal|last1=Sang|first1=Huynh Minh|last2=Ky|first2=Le Trung|last3=Fotedar|first3=Ravi|date=2009-08-01|title=Dietary supplementation of mannan oligosaccharide improves the immune responses and survival of marron, Cherax tenuimanus (Smith, 1912) when challenged with different stressors|url=http://www.sciencedirect.com/science/article/pii/S1050464809001995|journal=Fish & Shellfish Immunology|language=en|volume=27|issue=2|pages=341–348|doi=10.1016/j.fsi.2009.06.003|pmid=19539033|issn=1050-4648|url-access=subscription}}</ref>

== Description ==

== Description ==

The hairy marron ranges in colour from olive green to brown to black, with females sometimes having red or purple patches on their undersides.<ref name=”:0″ /><ref name=”:4″ /><ref name=”:7″>{{Cite web|title=Margaret River Hairy Marron – Arca del Gusto|url=https://www.fondazioneslowfood.com/en/ark-of-taste-slow-food/margaret-river-hairy-marron/|access-date=2020-12-08|website=Slow Food Foundation|language=en-US}}</ref> Adult hairy marrons grow to between 300 and 400&nbsp;mm with a body consisting of a head and thorax that are protected by a carapace.<ref name=”:0″ /><ref name=”:4″ /><ref name=”:7″ /> The body eventually extends into an abdomen that ends in a muscular tail, and the body is bracketed by 5 pairs of legs including two pairs of pinchers; a larger pair for capturing prey and defense and a second, smaller pair for fine manipulation of food.<ref name=”:4″ /><ref name=”:7″ /> The hairy marron can be differentiated from the smooth marron by the hairy bristles that are known to sometimes cover its carapace and other body parts, although these bristles can be difficult to observe in juveniles.<ref name=”:0″ /><ref name=”:4″ /><ref name=”:7″ />

The hairy marron ranges in colour from brown to black, with females sometimes having red or purple patches on their undersides.<ref name=”:0″ /><ref name=”:4″ /><ref name=”:7″>{{Cite web|title=Margaret River Hairy Marron – Arca del Gusto|url=https://www.fondazioneslowfood.com/en/ark-of-taste-slow-food/margaret-river-hairy-marron/|access-date=2020-12-08|website=Slow Food Foundation|language=en-US}}</ref> Adult hairy marrons grow to between 300 and 400&nbsp;mm with a body consisting of a head and thorax that are protected by a carapace.<ref name=”:0″ /><ref name=”:4″ /><ref name=”:7″ /> The body eventually extends into an abdomen that ends in a muscular tail, and the body is bracketed by pairs of legs of .<ref name=”:4″ /><ref name=”:7″ /> The hairy marron can be differentiated from the smooth marron by the bristles that are known to sometimes cover its carapace and other body parts, although these bristles can be difficult to observe in juveniles.<ref name=”:0″ /><ref name=”:4″ /><ref name=”:7″ />

=== Diet ===

=== Diet ===

The hairy marron is an omnivore whose diet mainly consists of small invertebrates, fish eggs and larvae, and algae.<ref name=”:4″ />  It is also a cannibal that will potentially eat its own young.<ref name=”:4″ />

The hairy marron is an whose diet mainly consists of small invertebrates, fish eggs and larvae, and algae.<ref name=”:4″ />  It is also a cannibal that will potentially eat its own young.<ref name=”:4″ />

== Habitat ==

== Habitat ==

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== Invasion by smooth marron ==

== Invasion by smooth marron ==

One of the greatest threats to wild populations of hairy marron is invasion by the closely related smooth marron, which was introduced into the Margaret River in the 1980s, and which progressively replaced the hairy marron in the lower regions of the Margaret River from 1980 to 1992.<ref name=”:3″>{{Cite journal|last1=Vercoe|first1=Phil|last2=Lawrence|first2=Craig|last3=de Graaf|first3=Martin|date=2009|title=Rapid replacement of the critically endangered hairy marron by the introduced smooth marron (Decapoda, Parastacidae) in the Margaret River (Western Australia)|url=https://brill.com/view/journals/cr/82/11/article-p1469_10.xml|journal=Crustaceana|volume=82|issue=11|pages=1469–1476|doi=10.1163/156854009X463937|issn=0011-216X|url-access=subscription}}</ref>  Although the replacement of the hairy marron by the smooth marron in the middle portion of the river is not very well documented, the hairy marron was observed to be completely gone from the middle of the river in 2000.<ref name=”:3″ />  Beginning in the same year, smooth marron have always been observed living alongside all hairy marron populations in the upper portion of the Margaret River.<ref name=”:5″ /><ref name=”:3″ />  Marron populations in the Margaret River follow the general trend of increasing in hairy marron and decreasing in smooth marron for regions further up the river.<ref name=”:3″ />  This trend has led scientists to conclude that smooth marron were most likely introduced in the lower portions of the river and spread to the middle and upper regions over time, replacing hairy marron through several processes including competition and hybridization.<ref name=”:3″ />

One of the greatest threats to wild populations of hairy marron is invasion by the closely related smooth marron, which was introduced into the Margaret River in the 1980s, and which progressively replaced the hairy marron in the lower regions of the Margaret River .<ref name=”:3″>{{Cite journal|last1=Vercoe|first1=Phil|last2=Lawrence|first2=Craig|last3=de Graaf|first3=Martin|date=2009|title=Rapid replacement of the critically endangered hairy marron by the introduced smooth marron (Decapoda, Parastacidae) in the Margaret River (Western Australia)|url=https://brill.com/view/journals/cr/82/11/article-p1469_10.xml|journal=Crustaceana|volume=82|issue=11|pages=1469–1476|doi=10.1163/156854009X463937|issn=0011-216X|url-access=subscription}}</ref>  Although the replacement of the hairy marron by the smooth marron in the middle portion of the river is not very well documented, the hairy marron was observed to be completely gone from the middle of the river in 2000.<ref name=”:3″ />  Beginning in the same year, smooth marron have always been observed living alongside all hairy marron populations in the upper portion of the Margaret River.<ref name=”:5″ /><ref name=”:3″ />  Marron populations in the Margaret River follow the general trend of increasing in hairy marron and decreasing in smooth marron for regions further up the river.<ref name=”:3″ />  This trend has led scientists to conclude that smooth marron were most likely introduced in the lower portions of the river and spread to the middle and upper regions over time, replacing hairy marron through several processes including competition and hybridization.<ref name=”:3″ />

=== Hybridization ===

== Hybridization ==

The hairy marron and the smooth marron have been classified as two separate species in past studies based on their morphology and genetics.<ref>{{Cite journal|last1=Austin|first1=C. M.|last2=Ryan|first2=S. G.|date=2002|title=Allozyme evidence for a new species of freshwater crayfish of the genus Cherax Erichson (Decapoda : Parastacidae) from the south-west of Western Australia|url=https://www.publish.csiro.au/is/it01010|journal=Invertebrate Systematics|language=en|volume=16|issue=3|pages=357–367|doi=10.1071/it01010|issn=1447-2600|url-access=subscription}}</ref>  However, further research has found that smooth marron and hairy marron are able to interbreed and that interbreeding can produce reproductively viable hybrids.<ref name=”:3″ /> Debate as to whether the hairy marron and the smooth marron are the same or different species is currently ongoing within the scientific community.<ref name=”:3″ /> Even though interbreeding of the two species has been observed, it has been hypothesized that there is some sort of barrier between the two marrons that prevents them from interbreeding easily.<ref name=”:6″ />  This hypothesis is based on some research that suggests interbreeding is less frequent than it would be if the smooth marron and the hairy marron belong to the same species.<ref name=”:6” />

The hairy marron and the smooth marron have been classified as two separate species in past studies based on their morphology and genetics.<ref>{{Cite journal|last1=Austin|first1=C. M.|last2=Ryan|first2=S. G.|date=2002|title=Allozyme evidence for a new species of freshwater crayfish of the genus Cherax Erichson (Decapoda : Parastacidae) from the south-west of Western Australia|url=https://www.publish.csiro.au/is/it01010|journal=Invertebrate Systematics|language=en|volume=16|issue=3|pages=357–367|doi=10.1071/it01010|issn=1447-2600|url-access=subscription}}</ref>  However, further research has found interbreed hybrids. smooth marron the of the two that .<ref name=”:6″ /> This is the <ref name=”:” />

== Aquaculture and conservation ==

== Aquaculture and conservation ==

The [[Western Australia State Government]] has applied knowledge gained from the smooth marron (”Cherax cainii”) aquaculture industry and freshwater research to develop a captive breeding program aimed at conserving the critically endangered Margaret River hairy marron (”Cherax tenuimanus”).<ref>{{Cite journal |last=Duffy et al |first=Rodney1 |date=2025 |year=2025-08-11 |title=Successful artificial incubation and juvenile-rearing of dropped eggs of

The aquaculture of hairy marron is a small-scale industry in Australia, which is also being utilized by [[the Australian]] Government to conduct a [[captive breeding]] program in an attempt to preserve the species.<ref name=”:8″>{{Cite web|title=- Margaret River Hairy Marron|url=https://www.natureconservation.org.au/our-work/threatened-species-protection/margaret-river-hairy-marron/|access-date=2020-12-09|website=Nature Conservation Margaret River Region|language=en-AU}}</ref> Efforts were also undertaken between 2013 and 2017 to regularly remove smooth marron from the few pools inhabited by hairy marron, but it was eventually decided that these fish outs were not having a pronounced enough effect to preserve wild populations.<ref name=”:8″ /> Conservation efforts have now turned toward expanding the captive breeding program and finding other sites where the captive marron could potentially be reintroduced to native water systems.<ref name=”:8″ />

a critically endangered freshwater crayfish (Cherax tenuimanus) |url=https://www.publish.csiro.au/mf/pdf/MF25063 |journal=Marine and Freshwater Research |volume=76 |via=CSIRO}}</ref> Between 2013 and 2017, targeted removal efforts were undertaken to extract smooth marron from the limited pools still inhabited by hairy marron. However, subsequent evaluations indicated that these “fish-out” operations were insufficient to halt the decline of wild populations. <ref name=”:8″ /> As a result, conservation strategies have shifted toward expanding the captive breeding program, including initiatives at [[Perth Zoo]], [[Department of Primary Industries and Regional Development|DPIRD]] and investigating suitable sites for potential reintroduction of genetically verified hairy marron into native aquatic habitats.<ref name=”:8″ />

== References ==

== References ==

Species of crayfish

Cherax tenuimanus, known as the Hairy marron or Margaret River marron, is one of two species of crayfish in Southwestern Australia known as marron. It occupies a narrow range within the southwestern biogeographical region of Margaret River. It is currently listed as critically endangered on the IUCN Red List, because of the threat from the smooth marron, Cherax cainii, which was introduced to its habitat.^[1]

Recent studies have shown that adding mannanoligosaccharide (Bio-Mos) to the diet of Cherax tenuimanus can increase their immunity and rate of survival.^[2][3]

The hairy marron ranges in colour from brown to black, with females sometimes having red or purple patches on their undersides.^[4][5][6] Adult hairy marrons grow to between 300 and 400 mm with a body consisting of a head and thorax that are protected by a carapace.^[4][5][6] The body eventually extends into an abdomen that ends in a muscular tail, and the body is bracketed by 4 pairs of legs plus one pair of chelipeds or claws.^[5][6] The hairy marron can be differentiated from the smooth marron by the hair-like bristles called setae that are known to sometimes cover its carapace and other body parts, although these bristles can be difficult to observe in juveniles.^[4][5][6]

The hairy marron is an omnivorous detritovore whose diet mainly consists of small invertebrates, fish eggs and larvae, and algae.^[5]  It is also a cannibal that will potentially eat its own young.^[5]

The hairy marron lives in exclusively freshwater habitats, specifically in clear, oxygen-rich water in the Margaret River in Southwestern Australia.^[4] Its range has become limited to 3 major pools in the upper portion of the river due to competition with the smooth marron.^[4] Exact environmental parameters needed for the survival of the hairy marron are unknown due to the low number of individuals in natural settings.^[7] However, studies performed in aquaculture settings have shown that hairy marron survive best in water that is about 25 degrees Celsius and that with a salinity of at least 100 mg/L.^[7] They also prefer habitats with debris or other structures they can use as shelter or as food sources if the material is organic.^[4]

Hairy marrons begin to mate when they reach sexual maturity during the second and third years of their lives, with their mating season occurring between July and October.^[4][5] During reproduction, the females typically incubate 200-400 eggs inside of them for almost 6 months, although larger females have been known to produce up to 800 eggs.^[4][5]  The female then lays the eggs on her swimmerets, and reproduction takes place when a male passes a sperm packet to the female, which the female then uses to fertilize the eggs in a process nearly identical to that used by the smooth marron.^[4][5] The eggs are then held under the female’s tail for several weeks, hatching at or just after the end of the mating season, and the juveniles remain on the mother’s swimmerets until they have finished consuming their yolk sacs and are mature enough to feed on their own, which is usually by November or December.^[4][5] The smooth marron is known to follow a similar reproductive pattern, but there is some evidence that their breeding season occurs earlier in the year than that of the hairy marron.^[4][8]  This difference in timing is theorized to result in the juvenile smooth marron reaching larger sizes before juvenile hairy marron, granting the smooth marron a competitive advantage.^[9]

One of the greatest threats to wild populations of hairy marron is invasion by the closely related smooth marron, which was introduced into the Margaret River in the 1980s, and which progressively replaced the hairy marron in the lower regions of the Margaret River through introgression and back breeding.^[10]  Although the replacement of the hairy marron by the smooth marron in the middle portion of the river is not very well documented, the hairy marron was observed to be completely gone from the middle of the river in 2000.^[10]  Beginning in the same year, smooth marron have always been observed living alongside all hairy marron populations in the upper portion of the Margaret River.^[8][10]  Marron populations in the Margaret River follow the general trend of increasing in hairy marron and decreasing in smooth marron for regions further up the river.^[10]  This trend has led scientists to conclude that smooth marron were most likely introduced in the lower portions of the river and spread to the middle and upper regions over time, replacing hairy marron through several processes including competition and hybridization.^[10]

The hairy marron and the smooth marron have been classified as two separate species in past studies based on their morphology and genetics.^[11]  However, further research has found these two species can interbreed, producing hybrids. Over time, some of these hybrids have bred back with smooth marron, gradually mixing the genes of the two species—a process called introgression. Genetic studies show that most hybrids are genetically closer to smooth marron, and very few carry mostly hairy marron genes. ^[9] This means the unique genetic identity of the hairy marron is slowly being lost, which could lead to its extinction in the wild unless conservation efforts succeed. ^[12]

The Western Australia State Government has applied knowledge gained from the smooth marron (Cherax cainii) aquaculture industry and freshwater research to develop a captive breeding program aimed at conserving the critically endangered Margaret River hairy marron (Cherax tenuimanus).^[13] Between 2013 and 2017, targeted removal efforts were undertaken to extract smooth marron from the limited pools still inhabited by hairy marron. However, subsequent evaluations indicated that these “fish-out” operations were insufficient to halt the decline of wild populations. ^[12] As a result, conservation strategies have shifted toward expanding the captive breeding program, including initiatives at Perth Zoo, DPIRD and investigating suitable sites for potential reintroduction of genetically verified hairy marron into native aquatic habitats.^[12]