Halodule uninervis

{{Short description|Species of plant in the manatee-grass family}} {{Speciesbox |image = Seagrass Halodule uninervis (5777808662).jpg |status = LC |status_system = IUCN3.1 |status_ref = <ref name="iucn status 19 November 2021">{{cite iucn |author=Short, F.T. |author2=Carruthers, T.J.R. |author3=Waycott, M. |author4=Kendrick, G.A. |author5=Fourqurean, J.W. |author6=Callabine, A. |author7=Kenworthy, W.J. |author8=Dennison, W.C. |date=2010 |title=''Halodule uninervis'' |volume=2010 |article-number=e.T173328A6991773 |doi=10.2305/IUCN.UK.2010-3.RLTS.T173328A6991773.en |access-date=19 November 2021}}</ref> |genus = Halodule |species = uninervis |authority = (Forssk.) Boiss.<ref name=KewPOWO>{{cite web|url= https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:602956-1|title= Halodule uninervis (Forssk.) Boiss.|author=|date=n.d.|website=Plants of the World Online|publisher=The Trustees of the Royal Botanic Gardens, Kew|access-date= September 16, 2020}}</ref><ref name=WFoL>{{cite web|url= http://www.worldfloraonline.org/taxon/wfo-0000769316|title= Halodule uninervis (Forssk.) Boiss.|author=|date=n.d.|website=World Flora Online|publisher=The World Flora Online Consortium|access-date= September 16, 2020}}</ref> |synonyms = ''Cymodocea australis'' (Miq.) Trimen ''Diplanthera indica'' Steud. ''Diplanthera madagascariensis'' Steud. ''Diplanthera tridentata'' Steinh. ''Diplanthera uninervis'' (Forssk.) F.N.Williams ''Halodule australis'' Miq. ''Halodule tridentata'' (Steinh.) Endl. ex Unger ''Phucagrostis tridentata'' Ehrenb. & Hemprich ex Boiss. ''Zostera tridentata'' Solms ''Zostera uninervis'' Forssk. |synonyms_ref = <ref name=KewPOWO/> }}

'''''Halodule uninervis''''' is a species of seagrass in the family Cymodoceaceae.<ref name=KewPOWO/> It is native to the western Pacific and Indian Oceans. Common names include '''narrowleaf seagrass''' in English and '''''a'shab bahriya''''' in Arabic.<ref name=algae>Guiry, M. D. & G. M. Guiry. 2013. [http://www.algaebase.org/search/species/detail/?species_id=21536 ''Halodule uninervis'' (Forsskål) Ascherson.] AlgaeBase. National University of Ireland, Galway. Accessed 28 June 2013.</ref>

==Distribution and habitat== This is a common plant of the sublittoral zone in its range, growing in depths up to 20 meters in lagoons, on reefs, and in many other types of marine habitat just offshore. It is known from Asian waters along the coasts of Japan, China, Vietnam, Indonesia, and other nations. It occurs on Pacific Islands such as Fiji. It occurs along the Australian Pacific coast, including the Great Barrier Reef. It can be found along Indian Ocean coastal regions from Australia to India to eastern Africa. It is resident in the Red Sea and Persian Gulf.<ref name="iucn status 19 November 2021" />

==Description== This species is a flowering plant spreading via a branching rhizome that roots at the nodes. It produces erect stems and alternately arranged leaves. The narrow, toothed leaf blades are up to {{Convert|15|cm|sp=us}} long and usually roughly a millimeter wide,<ref name=china>[http://www.efloras.org/florataxon.aspx?flora_id=2&taxon_id=242324444 ''Halodule uninervis''.] Flora of China.</ref> though leaf width is variable and can be up to 7 millimeters.<ref name="iucn status 19 November 2021" /> Each leaf has a sturdy sheath up to {{Convert|3.5|cm|sp=us}} long. The tip of the leaf blade has three teeth.<ref name=nsw>[http://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Halodule~uninervis ''Halodule uninervis''.] New South Wales Flora Online. National Herbarium, Royal Botanic Garden, Sydney.</ref> Plants of this family are dioecious. The male flower is borne on a short peduncle and is enclosed in a leaf.<ref name=china/> The tiny anthers are red.<ref name=nsw/> The fruit is about 2 millimeters long.<ref name=china/>

Leaf morphology changes according to habitat type. The leaves are wider in deeper waters. There are apparently two morphs, a narrow leaf and a wide leaf, rather than a continuous range. The narrow leaf type is found closer to shore where it is exposed more often. The wide leaf type is found in deeper areas with cloudier waters. Plants that receive less light may need more leaf blade area to perform enough photosynthesis.<ref name=hedge>Hedge, S., et al. (2009). [http://www.rrrc.org.au/publications/downloads/371-QPIF-Hedge-S-2009-Temporal-and-spatial-seagrass-variability.pdf Temporal and spatial morphological variability of the seagrasses ''Halophila ovalis'' and ''Halodule uninervis'' throughout the Great Barrier Reef region: Preliminary analysis.] {{Webarchive|url=https://web.archive.org/web/20130427064318/http://rrrc.org.au/publications/downloads/371-QPIF-Hedge-S-2009-Temporal-and-spatial-seagrass-variability.pdf |date=2013-04-27 }} Report to the Marine and Tropical Sciences Research Facility, Department of the Environment, Water, Heritage and the Arts. Reef and Rainforest Research Centre Limited, Cairns.</ref>

==Biology== This grass forms dense carpets or meadows on the substrate, sometimes mixing with other seagrasses and algaes.<ref name="iucn status 19 November 2021" />

It occupies the lower intertidal zone, and it is less tolerant of exposure to air than are plants of the upper intertidal zone such as ''Thalassia hemprichii''. It desiccates quickly. It is also sensitive to ultraviolet radiation. These factors restrict it to deeper intertidal waters than some other plants.<ref name=lan>Lan, C. Y., et al. (2005). [http://fishdb.sinica.edu.tw/pdf/166.pdf Measurement of chlorophyll fluorescence reveals mechanisms for habitat niche separation of the intertidal seagrasses ''Thalassia hemprichii'' and ''Halodule uninervis''.] ''Marine Biology'' 148(1) 25-34.</ref>

It is a euryhaline species, tolerating a wide salinity range.<ref name="iucn status 19 November 2021" /><ref name=ben>Bensam, P. and T. R. Udhayashankar. [http://eprints.cmfri.org.in/6975/1/095-2ND_INDIAN_FISHERIES_FORUM_PROCEEDINGS_1993.pdf Colonisation and growth of the sea grasses, ''Halodule uninervis'' (Forskal) Ascherson and ''Halophila ovalis'' (R. Brown) Hooker f. in marine culture ponds at Mandapam.] The Second Indian Fisheries Forum Proceedings. Mangalore, India. May 27–31, 1990. 51-53.</ref>

==Ecology== This species is an important food for the dugong.<ref name="iucn status 19 November 2021" /><ref name=lip>Lipkin, Y. (1975). [http://www.tandfonline.com/doi/abs/10.1080/00212210.1975.10688415#.Uc3wXZzLjrc Food of the Red Sea dugong (Mammalia: Sirenia) from Sinai.] ''Israel Journal of Zoology'' 24(3-4) 81-98.</ref> The grass grows in the Masirah Channel, a waterway between Masirah Island and mainland Oman, where it is an important food for the green sea turtle.<ref name=jupp>Jupp, B. P., et al. (1996). [http://www.seaturtle.org/PDF/JuppBP_1996_AquatBot.pdf Distribution, abundance, and species composition of seagrasses at several sites in Oman.] ''Aquatic Botany'' 53(3) 199-213.</ref>

This is a pioneer species. It has been observed on high-sediment, rapidly evolving substrates in Australia and Indonesia.<ref name="iucn status 19 November 2021" />

This species is known to be hybridized to ''Halodule'' ''pinifolia'' in Okinawa, Japan.<ref>Ito, Y., and Nr. Tanaka (2011) [http://www.rbgsyd.nsw.gov.au/science/Scientific_publications/telopea/contents_by_volume/volume_13 Hybridisation in a tropical seagrass genus, Halodule (Cymodoceaceae), inferred from plastid and nuclear DNA phylogenies] {{Webarchive|url=https://archive.today/20130825034821/http://www.rbgsyd.nsw.gov.au/science/Scientific_publications/telopea/contents_by_volume/volume_13 |date=2013-08-25 }}. Telopea 13: 219-231.</ref>

==Conservation== This plant is widely distributed and it is common throughout its range. In general its populations are stable, though it may be decreasing in localized areas, such as the coast of Bangladesh, and it fluctuates in some Australian waters. It is affected by some degradation of habitat by forces such as coastal development, siltation, sedimentation, weather events and tidal action, predation, parasites, disease, trawling and other fishing practices, dredging, pollution, eutrophication, and climate change.<ref name="iucn status 19 November 2021" />

Conservation plans are in effect in various regions. Populations are monitored in the United Arab Emirates. It grows within the bounds of several marine parks and reserves in Africa. Populations can be disturbed only with permits in parts of Australia. Large beds are protected in Hat Chao Mai National Park in Thailand.<ref name="iucn status 19 November 2021" />

==References== {{Reflist}}

==External links== *WoRMS. (2013). [http://www.marinespecies.org/aphia.php?p=taxdetails&id=208924 ''Halodule uninervis'' (Forsskål) Ascherson, 1882.] In: Guiry, M. D. & G. M. Guiry. AlgaeBase. National University of Ireland, Galway. World Register of Marine Species. Accessed 28 June 2013.

Category:Cymodoceaceae Category:Biota of the Indian Ocean Category:Flora of the Pacific Category:Taxa named by Pierre Edmond Boissier Category:Taxa named by Peter Forsskål