Acianthus

{{Short description|Genus of flowering plants}} {{Use dmy dates|date=December 2023}} {{automatic taxobox | image = Acianthus exsertus (24997834335).jpg | image_caption = ''[[Acianthus exsertus]]'' | display_parents = 3 | taxon = Acianthus | authority = [[R.Br.]]<ref name="APC">{{cite web |title=''Acianthus'' |url=https://biodiversity.org.au/nsl/services/apc-format/display/73143 |website=Australian Plant Census |accessdate= 11 November 2022}}</ref> | synonyms_ref = <ref name="APC" /> | synonyms = {{collapsible list| * ''Acianthella'' [[David L. Jones (botanist)|D.L.Jones]] & [[M.A.Clem.]] * ''Acianthopsis'' M.A.Clem. & D.L.Jones * ''Acianthopsis'' [[Szlach.]] [[nom. illeg.]] * ''Acianthus'' R.Br. sect. ''Acianthus'' * ''Acianthus'' sect. ''Macropetalus'' [[Paul Joseph Kores|Kores]] * ''Acianthus'' R.Br. subg. ''Acianthus'' * ''Acianthus'' subg. ''Univiscidiati'' Kores * ''Acianthus'' subg. ''Univiscidiatus'' Kores [[orth. var.]] * ''Nemacianthus'' D.L.Jones & M.A.Clem. * ''Univiscidiatus'' Szlach. nom. inval. * ''Univiscidiatus'' D.L.Jones, M.A.Clem., [[I.K.Sharma]], [[A.M.Mack.]] & [[Brian Peter John Molloy|Molloy]] nom. inval. * ''Univiscidiatus'' sect. ''Macropetalus'' Szlach. nom. inval. | subdivision_ranks = Species | subdivision = See text | range_map = Acianthus distribution map.png | range_map_caption = ''Acianthus'' range map }} }}

'''''Acianthus''''', commonly known as '''mosquito orchids''', is a [[genus]] of about twelve [[species]] of [[plant]]s in the orchid [[Family (taxonomy)|family]], [[Orchidaceae]]. Mosquito orchids are [[Terrestrial plant|terrestrial]] [[Herbaceous plant|herbs]] with a single, heart-shaped, usually ground-hugging leaf and one to many small, green, pinkish or purplish flowers on a fleshy stalk. They are found in [[New Caledonia]], [[Australia]] and [[New Zealand]].

==Description== Orchids in the genus ''Acianthus'' are [[Terrestrial plant|terrestrial]], [[Perennial plant|perennial]], [[deciduous]], [[sympodial]] herbs with a single egg-shaped, heart-shaped or lobed leaf at the base. They have small, roughly spherical, underground [[tuber]]s from which the flower stems arise. Lacking true roots, they have root-like [[stolon]]s which develop "daughter" tubers at their ends. These orchids spend the dry, summer months dormant until, following late-summer or autumn rains, the leaf appears. The leaf is [[wikt:glabrous|glabrous]], sometimes ground-hugging, more usually held above the ground and is often purplish-red on the lower surface. Sometimes the leaves of plants with flowers are different from those lacking them. The leaves of all Australian species are very similar, making them hard to identify to species level in the absence of flowers.<ref name="Jones">{{cite book|last1=Jones|first1=David L.|title=A complete guide to native orchids of Australia including the island territories|date=2006|publisher=New Holland|location=Frenchs Forest, N.S.W.|isbn=1-877069-12-4|page=161}}</ref><ref name="Hoffman">{{cite book|last1=Hoffman|first1=Noel|last2=Brown|first2=Andrew|title=Orchids of south-west Australia|date=1984|publisher=University of Western Australia Press|location=Nedlands, W.A.|isbn=0855642262|page=189|edition=2}}</ref><ref name="Bishop">{{cite book|last1=Bishop|first1=Anthony|title=Field guide to the orchids of New South Wales and Victoria|date=1996|publisher=UNSW Press|location=Sydney|isbn=086840375X|page=172}}</ref><ref name="Backhouse">{{cite book|last1=Backhouse|first1=Gary|last2=Jeanes|first2=Jeffrey|title=The orchids of Victoria|date=1995|publisher=Miegunyah Press|location=Carlton, Vic.|isbn=052284393X|edition=1st}}</ref><ref name="Pridgeon">{{cite book|editor-last1=Pridgeon|editor-first1=Alec M.|editor-last2=Cribb|editor-first2=Phillip J.|editor-last3=Chase |editor-first3=Mark W.|editor-last4=Rasmussen |editor-first4=Finn|title=Genera Orchidacearum (Volume 2), Orchidoideae (part 1)|date=2001|publisher=Oxford University Press|location=Oxford, England|isbn=0198507100|pages=68–70}}</ref><ref name="RBGS">{{cite web|title=''Acianthus''|url=http://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&search=yes&namesearch=Acianthus&dist=|publisher=Royal Botanic Gardens Sydney: plantnet|accessdate=9 June 2016}}</ref><ref name="efloraSA">{{cite web|title=''Acianthus''|url=http://www.flora.sa.gov.au/cgi-bin/speciesfacts_display.cgi?form=speciesfacts&family=&genus=Acianthus&species=&iname=&submit=Display|publisher=Government of South Australia: efloraSA|accessdate=9 June 2016}}</ref><ref name="ANBG">{{cite web|title=''Acianthus''|url=https://www.anbg.gov.au/cpbr/cd-keys/orchidkey/html/genera/Acianthus.htm|publisher=Australian National Botanic Gardens|accessdate=12 June 2016}}</ref>

Flowers appear in the cooler months, usually in autumn, winter or spring, There are one to many [[Resupination|resupinate]] small, green, pinkish or purplish flowers {{convert|4 to 5|mm|in|sigfig=2|abbr=on}} in diameter. The flowers are held on an upright, narrow but fleshy stalk, blend in with their surrounding and often resemble mosquitoes. The [[sepal]]s are longer than the [[petal]]s and usually have a long, thin extension on their end. The [[wikt:dorsal|dorsal]] sepal is broader than the [[wikt:lateral|lateral]] ones and sometimes forms a hood over the [[Column (botany)|column]]. The [[wikt:lateral|lateral]] sepals project forward beneath the [[labellum (botany)|labellum]] and the petals spread widely or curve backwards against the ovary. The labellum is heart-shaped and has a prominent [[Labellum (botany)|callus]]. The fruit is a thin-walled, glabrous [[Capsule (botany)|capsule]], containing a large number of winged seeds.<ref name="Jones" /><ref name="Bishop" /><ref name="efloraSA" /><ref name="ANBG" />

==Taxonomy and naming== The genus was first formally described by [[Robert Brown (Scottish botanist from Montrose)|Robert Brown]] in 1810 in ''[[Prodromus Florae Novae Hollandiae]]''. He described three species (''[[Acianthus fornicatus|A. fornicatus]]'', ''[[Acianthus exsertus|A. exsertus]]'' and ''[[Acianthus caudatus|A. caudatus]]'') but did not nominate a [[type species]].<ref name=APNI>{{cite web|title=''Acianthus''|url=https://id.biodiversity.org.au/instance/apni/485113|publisher=APNI|accessdate=16 September 2019}}</ref><ref name="Brown">{{cite book|last1=Brown|first1=Robert|title=Prodromus Florae Novae Hollandiae|date=1810|location=London|pages=321–322|url=https://www.biodiversitylibrary.org/item/21771#page/191/mode/1up|accessdate=9 June 2016}}</ref> Orchids in this genus are closely related to those in the genus ''[[Caladenia]]''.<ref name="Hoffman" />

The genus name (''Acianthus'') is derived from the Greek ''ake'' or ''akis'', "a point, needle" and ''anthos'' "flower" referring to the pointed [[wikt:perianth|perianth]] and the [[wikt:acuminate|acuminate]] floral segments.<ref name="Quattrocchi">{{cite book |last1=Quattrocchi |first1=Umberto |title=CRC world dictionary of plant names : common names, scientific names, eponyms, synonyms, and etymology (Volume 1) |date=2000 |publisher=CRC Press |isbn=0849326737 |page=30}}</ref><ref name="NZPCN">{{cite web |title=''Acianthus sinclairii'' |url=https://www.nzpcn.org.nz/flora/species/acianthus-sinclairii/ |publisher=New Zealand Plant Conservation Network |access-date=12 March 2022}}</ref>

===Species=== The following is a list of ''Acianthus'' species accepted by [[Australian Plant Census]] as at March 2025, apart from ''A. sinclairii'' that is accepted by the [[New Zealand Plant Conservation Network]]:<ref name="APClist">{{cite web |title=''Acianthus'' R.Br. |url=https://biodiversity.org.au/nsl/services/search/taxonomy?product=APC&tree.id=51209179&name=Acianthus&inc._scientific=&inc.scientific=on&inc._cultivar=&max=100&display=apc&search=true |publisher=Australian Plants Census |access-date=12 March 2022}}</ref><ref name="NZPCN" /> {{div col|colwidth=35em}} *''[[Acianthus apprimus]]'' [[D.L.Jones]] – early mosquito orchid (New South Wales) *''[[Acianthus borealis]]'' [[D.L.Jones]] – northern mosquito orchid (Queensland) *''[[Acianthus caudatus]]'' [[R.Br.]] – mayfly orchid (Queensland, New South Wales, Victoria, South Australia and Tasmania) *''[[Acianthus collinus]]'' D.L.Jones – hooded mosquito orchid (New South Wales, the Australian Capital Territory, Victoria) *''[[Acianthus cuneatus]]'' D.L.Jones & [[L.M.Copel.]] (New South Wales) *''[[Acianthus exiguus]]'' D.L.Jones – tiny mosquito orchid (New South Wales) *''[[Acianthus exsertus]]'' R.Br. – gnat orchid, large mosquito orchid (Queensland, New South Wales, ACT, Victoria ) *''[[Acianthus fornicatus]]'' R.Br. – pixie-caps (Queensland, New South Wales, Victoria) *''[[Acianthus ledwardii]]'' [[Montague Rupp|Rupp]] – Ledward's mosquito orchid (Queensland) *''[[Acianthus pusillus]]'' D.L.Jones – small mosquito orchid (Queensland, New South Wales, Victoria, South Australia, Tasmania) *''[[Acianthus saxatilis]]'' D.L.Jones & [[M.A.Clem.]] (Queensland) *''[[Acianthus scopulus]]'' D.L.Jones (New South Wales) *''[[Acianthus sinclairii]]'' [[Hook.f.]] – heart-leaved orchid, pixie cap ([[New Zealand]]) {{div col end}}

[[Plants of the World Online]] considers ''[[Acianthus apprimus|A. apprimus]]'', ''[[Acianthus borealis|A. borealis]]'', ''[[Acianthus collinus|A. collinus]]'', ''[[Acianthus exiguus|A. exiguus]]'' to be [[Synonym (taxonomy)|synonyms]] of ''[[Acianthus fornicatus|A. fornicatus]]''.<ref name="powo1">{{cite web |title=''Acianthus fornicatus'' |url=https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:614677-1 |publisher=Plants of the World Online |access-date=3 April 2025}}</ref>

==Distribution and habitat== Of the Australian species of ''Acianthus'', 9 are found in [[New South Wales]], 6 in [[Queensland]], 3 in [[Victoria (Australia)|Victoria]] and 2 in [[South Australia]]. The sole New Zealand example, ''[[Acianthus sinclairii|A. sinclairii]]'' occurs on both [[North Island|North]] and [[South Island|South]] Islands, as well as on [[Raoul Island|Raoul]], [[Stewart Island|Stewart]], [[Chatham Island|Chatham]] and [[Three Kings Islands|Three Kings]] Islands.<ref name="Pridgeon" /><ref name="NZPCN" />

Mosquito orchids species grow in small groups in forests on decaying litter, occasionally on partially decayed logs. They sometimes form dense [[Vegetative reproduction|vegetative]] colonies, in sheltered forest or heathland, and are often found underneath shrubs and bracken.<ref name="Hoffman" />

==Ecology== The labellum of ''Acianthus'' species produces a sweet nectar which is contained in a sunken area at the base of the labellum. The flowers of Australian species open in sequence up the flowering spike, each flower open for a few days, and are [[wikt:pollinate|pollinate]]d by [[fungus gnat]]s from the families [[Anisopodidae]], [[Sciaridae]] and [[Mycetophilidae]]. Usually only a small percentage of the plants in a colony have flowers. Flies on ''[[Acianthus caudatus]]'' have been observed to move up the labellum, probing with their [[Proboscis#Invertebrates|proboscis]] until they reach the nectar, where the up and down "pumping" action of their bodies brings them into contact with the [[Pollinium|viscidium]] and pollinia which then adhere to the insect's body. When these are carried to another flower, a similar action causes the pollinia to attach to the receptive [[Stigma (botany)|stigma]].<ref name="Jones" /><ref name="Bishop" /><ref name="Pridgeon" /><ref name="ANBG" />

==Use in horticulture== Mosquito orchids are easy to grow in plastic or ceramic pots. They need to be watered regularly except when dormant over summer and to be repotted every one or two years.<ref name="Pridgeon" /><ref name="Jones(2)">{{cite book|last1=Jones|first1=David L.|title=A complete guide to native orchids of Australia including the island territories|date=2006|publisher=New Holland|location=Frenchs Forest, N.S.W.|isbn=1-877069-12-4|page=301}}</ref>

== References == {{Reflist}}

== External links == *{{Commons-inline|italic=1}}

[[Category:Acianthus| ]] [[Category:Diurideae genera]]