Nom taxonomique: Acanthophora spicifera (Vahl) Borgesen
Synonymes: Acanthophora antillarum Montagne ex Kützing 1865, Acanthophora intermedia Crouan, Acanthophora orientalis J. Agardh 1863, Acanthophora orientalis var. wightii (J. Agardh) Sonder 1879, Acanthophora spicifera f. orientalis (J.Agardh) Weber-van Bosse 1923, Acanthophora spicifera f. wightii (J. Agardh) Weber-van Bosse 1923, Acanthophora spicifera var. orientalis (J. Agardh) Zaneveld 1956, Acanthophora thierryi f. gracilis P.L. Crouan & H.M. Crouan 1878, Acanthophora thierryi J.V. Lamouroux 1813, Acanthophora wightii J. Agardh 1863, Chondria acanthophorara C. Agardh 1822, Fucus acanthophorus J.V. Lamouroux 1805, Fucus spicifer M. Vahl 1802
Noms communs: bulung tombong bideng (Malay), culot (Ilocano), red alga (English), spiny alga (English-Hawaii), spiny seaweed (English)
Type d'organisme: algue
Acanthophora spicifera est une algue rouge qui se rencontre dans la plupart des mers tropicales ou subtropicales du monde. Sa morphologie plastique lui permet de s'adapter à une variété de conditions et elle peut ainsi envahir divers types d'habitats. Elle est devenue envahissante à Hawaii. Elle est considérée comme l'espèce exotique d'algue la plus envahissante dans cette région où elle peut modifier les peuplements indigènes et rentrer en compétition avec des algues indigènes.
Acanthophora spicifera is an erect macroalgae which grows up to 40cm tall. It has solid cylindrical branches, 2-3mm wide, branched either sparingly or repeatedly. The main branches have short, determinate branches, irregularly shaped and spinose, with spines numerous and radially arranged. There are no spines on main axes. The plant grows from a large, irregularly shaped holdfast. In intertidal high-motion water areas, A. spicifera has short (4 - 10cm), compact and very dense thalli. In moderate or low water motion areas, the thalli are tall (10 - 25cm), more openly branched and occur in scattered clumps. Apices are pyramidal, with incurved trichoblasts. Pericentral cells are corticated densely, with central axial cells usually evident. In older axes, central axial filaments may be surrounded by small-celled adventitious filaments. A. spicifera is highly variable in colour: it can be shades of red, purple, yellow, orange, or brown. Thalli are often very dark in colour in intertidal, high motion areas, and are usually lighter colour in shallow areas with low water motion and reflective sandy or silty bottoms (University of Hawaii, 2001).
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Description de l'habitat
Acanthophora spicifera is commonly found on calm, shallow reef flats, tidepools, and on rocky intertidal benches. It usually attaches to hard substrates, such as rocks, basalt ledges, or dead coral heads, but may also occur as an epiphyte on other algae, or as relatively stable unattached populations. It has been reported at depths of up to 22m in the Virgin Islands, although it more typically occurs at 1-8m depths (University of Hawaii, 2001; Kilar and McLachlan, 1986; Hill, 2001). A. spicifera cannot withstand prolonged exposure to air, and as such its survival on reefs is increased when it co-occurs with dense aggregates of other algal species which are more tolerant of wave exposure, and are able to retain water when exposed to air (Hill, 2001).
Acanthophora spicifera has a plastic morphology, which allows it to adapt to different conditions and invade a diversity of habitats. The brittle nature of its branches often results in fragmentation, which contributes to frequent, large free-floating populations, and its widespread distribution (University of Hawaii, 2001). It is now one of the most widespread and successful alien algae in Hawaii, and may modify native communities by smothering and outcompeting native algal species (Preskitt, 2002; Eldredge, 2003).
Blooms of native A. spicifera covered by cyanobacterial epiphytes have been observed on several reefs in the Eastern Tropical Pacific, since widespread coral mortality opened substrate for colonisation during the 1997-98 El Nino Southern Oscillation. The bloom coincided with La Nina conditions, with thermocline shoaling and mixing upwards of nutrient-rich bottom water, but it persisted for several years after this (Fong et al. 2006).
Acanthophora spicifera is consumed in Tahiti, and also features in the diet of native Fijians (Payri et al. 2000; in Guiry, M.D. & Guiry, G.M. 2007; South, 1993). It is also used in vegetable salads, as soup flavouring and as a thickening agent in the Philippines, and is reported to contain carragenaans, used as an emulsifying agent (Trono, 1999).
In Panama, it has been reported that fish can exclude A. spicifera from some habitats by including it in their diet. A. spicifera is also grazed by sea urchins and crabs (Kilar and McLachlan, 1986).
Acanthophora spicifera is native to Florida and the Caribbean. Today it has a nearly continuous distribution in all tropical and subtropical seas of the world. It is reported from the USA (Hawaii), Bermuda, Bahamas, Turks and Caicos Islands, Cayman Islands, Cuba, Hispaniola, Jamaica, Netherland Antilles, Puerto Rico, Trinidad and Tobago, Virgin Islands Mexico, Belize, Costa Rica, Guatemala, Panama, Venezuela, Brazil, Colombia, Angola, Equatorial Guinea, Cameroon, Gabon, Guinea-Bissau, Kenya, Madagascar, Mauritius, Mauritania, Mozambique, Sao Tome and Principe, Senegal, Sierra Leone, South Africa, Tanzania, Seychelles, La Réunion, India, Maldives, Bahrain, Bangladesh, Iran, Kuwait, Oman, Pakistan, Philippines, Saudi Arabia, Sri Lanka, Yemen, China, Japan, Taiwan, Burma, Indonesia, Malaysia, Singapore, Vietnam, Australia, Federated States of Micronesia, Fiji, French Polynesia, New Caledonia, Samoa, Solomon Islands (Guiry, M.D. & Guiry, G.M. 2007).
Informations pour la gestion de l'espèce
No specific management action plans have been reported for this species
Sexual: Tetrasporophytes were the most common reproductive phase occurring on reef flats in Panama, with over 80% of plants tetrasporic throughout much of the year. This percentage was reduced to only 5% during periods of prolonged tidal immersion (Kilar and McLachlan, 1986; Hill, 2001).
Asexual: Fragmentation accounts for much of the distribution and standing crop of A. spicifera. On reef flats, as much as 26% of the standing crop can be lost to drift fragments each month (Hill, 2001) especially if the fragments either (a) do not release viable spores or (b) are unable to reattache to the substratum by production of secondary rhizoids (Mads Thomsen., pers.comm., June 2008).
A. spicifera appears to be able to release sexual propagules at all times of the year in Hawaii, and therefore may have greater potential for dispersal than macroalgae that reproduce only by fragmentation (Smith et al. 2002).
Stades du cycle de vie
Acanthophora spicifera has been reported to have a triphasic alternation of generations. Tetrasporophytic and gametophytic generations are isomorphic, and the gametophyte dioecious (Kilar and McLachlan, 1986).
Révisé par: Mads Solgaard Thomsen, Post doc, Benthic Section, Marine Department, National Environmental Research Institute University of Aarhus, Roskilde, Denmark.
Compilé par: IUCN/SSC Invasive Species Specialist Group (ISSG) with support from La Fondation d'entreprise Total
Dernière mise à jour: Tuesday, 9 January 2007