Posidonia oceanica (Linnaeus) Delile was included in the Texas flora (D. S. Correll and M. C. Johnston 1970; D. S. Correll and H. B. Correll 1972) because of specimens washed ashore along the Gulf of Mexico. The specimens were later determined to be Thalassia testudinum, based upon comparative growth studies and upon flavonoid chemistry profiles (C. McMillan et al. 1975).
Seagrass beds provide food and shelter, both directly and indirectly, to many ecologically and economically important fish and shellfish species. Over 100 species of fishes and over 30 crustacean species are found in Florida Bay, including both permanent residents and temporary residents using seagrass habitat as a nursery ground, such as spotted seatrout, redfish, snook, tarpon, snappers, and grunts. Important shellfish species include pink shrimp from the Tortugas bank, blue crabs, and spiny lobsters. (Robblee 1991)
Kirsch et al. (2002) studied grazing by smaller herbivores (e.g. the bucktooth parrotfish Sparisoma radians) on Thalassia tedudinum in Hawk Channel, in the northern Florida Keys (USA). They found that that seagrass grazing varied greatly both spatially and seasonally but, on average, grazers consumed virtually all of the aboveground production at 2 of the 3 sites studied. When experiments were repeated in the summer of a second year at 6 sites, seagrass grazing again varied greatly among sites, but at 3 of the sites most of the daily production of seagrass shoots was consumed by small herbivorous fishes. These results suggest that while it is undoubtedly true that modern day grazing by manatees, turtles, and waterfowl on seagrass is reduced relative to historical levels due to declines in populations of these large grazers, small vertebrate grazers nevertheless consume a substantial fraction of seagrass production in the northern Florida Keys.
A variety of sea urchins may graze heavily on Thalassia testudinum, sometimes even overgrazing (i.e., grazing at a rate that exceeds the seagrass growth rate), which may dramatically reduce seagrass biomass, leading to a restructuring of the local ecosystem (Eklof et al. 2008 and references therein).
Tussenbroek and Brearley (1998) found a burrowing isopod, Limnoria simulata, in sheaths of Thalassia testudinum in the Puerto Morelos reef lagoon, Mexican Caribbean, and this isopod likely has this habit across the Caribbean (Tussenbroek and Brearley 1998).
Turtle Grass (Thalassia testudinum) is an important seagrass found from Bermuda and southern Florida south to the Gulf of Mexico, the West Indies, Central America, and Venezuela. It can form very extensive beds in protected shallow waters that serve as both habitat and a food source for a tremendous diversity of organisms, among them sea turtles, which graze on T. testudinum and are the source of its common name. (Dineen 2001 and references therein)
in 1987, a mass die-off of Thalassia testudinum began in Florida Bay (Robblee et al. 1991). Robblee et al. estimated that over 4,000 hectares of seagrass beds had been denuded and an additional 23,000 hectares were affected to a lesser degree. About a third of the dense seagrass beds of western Florida were impacted over a period of just a year. Until the 1980s, Florida Bay was widely viewed as a healthy and stable ecosystem, with clear water, lush seagrass beds, and highly productive fish and shrimp populations. By 1992, the ecosystem appeared to have changed from a clear water system, dominated by benthic primary production, to a turbid water system, with algae blooms and resuspended sediments in the water column. (Rudnick et al. 2005 and references therein)
A defining feature of Florida Bay is its shallow depth, which averages just one to two meters. Light sufficient to support photosynthesis can reach the sediment surface in almost all areas of the bay, resulting in dominance of seagrass beds as both a habitat and a source of primary production (i.e., capturing energy from the sun through photosynthesis). In some portions of the bay, salinity can rise rapidly during drought periods due to water loss from evaporation exceeding input from precipitation and freshwater inflow. Following observations of Florida Bay’s dramatic ecological changes in the 1980s, it was commonly assumed that a direct cause of these changes was a longterm increase in salinity, which in turn was caused by the diversion of freshwater away from Florida Bay via South Florida Water Management District canals. However, subsequent research has indicated that these ecological changes may not be attributable to a single cause. While decreased freshwater inflow and resultant increased salinity have been part of the problem, it appears that other human activities, as well as natural forces, may have also played a role. (Rudnick et al. 2005 and references therein) Duarte (2002) notes that the causes of this die-off continue to be debated, and may include, among others, increased anthropogenic (i.e., human-caused) nutrient loading, the effects of climatic changes involving a long time interval without hurricanes affecting the area also causing unusually low freshwater discharge, and the effects of the increased accumulation of detritus derived from loss of large grazers. Difficulties in experimenting at the appropriate scale of entire seagrass meadows to test these hypotheses have made it difficult to assess to what degree the decline was due to human or natural causes, or a combination of both. (Rudnick et al. 2005 and references therein)
Regardless of the cause of the mass-mortality event, once it was initiated, the ecology of Florida Bay changed. Continued seagrass mortality results in increased sediment resuspension and increased nutrient (nitrogen and phosphorus) release from sediments, stimulating phytoplankton growth in the water column. The presence of phytoplankton and suspended sediment results in decreased light penetration to seagrass beds. This decreased light can limit seagrass growth and sustain the feedback loop. Dynamics of this feedback loop are probably not independent of the salinity regime. Seagrass wasting disease, caused by a slime mold (Labyrinthula sp.) infection, is more common at salinities close to or greater than seawater than at low salinities. High salinity may have played a role in the initial seagrass mass mortality event, but more likely has served to promote seagrass re-infection since that event. Incidence of this disease may therefore be directly affected by water management actions. (Rudnick et al. 2005 and references therein)
On a global scale, seagrasses--marine flowering plants that include the widely distributed genera Zostera, Thalassia, and Posidonia--in general appear to be in trouble (Waycott et al. 2009). Seagrasses form some of the most productive ecosystems on earth, rivaling even crops of corn and sugar cane. Seagrass meadows provide ecosystem services such as supporting commercial fisheries worth as much as $3500 per hectare per year, subsistence fisheries that support entire communities, nutrient cycling, sediment stabilization, and globally significant sequestration of carbon. Seagrasses and the services they provide are threatened by the immediate impacts of coastal development and growing human populations as well as by the impacts of climate change and ecological degradation. Seagrass losses also disrupt important linkages between seagrass meadows and other habitats, and their ongoing decline is likely producing much broader and long-lasting impacts than the loss of the meadows themselves. (Waycott et al. 2009 and references therein)
Under favorable conditions, Thalassia testudinum can grow several centimeters per day (Dineen 2001 and references therein).
Thalassia testudinum is restricted to the Gulf of Mexico and the Caribbean and has been recorded from Bermuda (the other species in the genus, T. hemprichii, is widely distributed in the coastal waters of the Indian Ocean and the western Pacific) (Larkum et al. 2006).
The widespread decline of seagrass, in particular Thalassia testudinum, in Florida Bay (Florida, U.S.A.) in 1987 was followed by a cascade of ecological effects. By 1992, frequent phytoplankton blooms began to appear in the central and western bay where none had been recorded previously. Negative impacts extended to higher trophic levels as well, including 100% mortality of some sponge species. Spiny lobster and pink shrimp catches at Tortugas Banks plunged in 1988 to their lowest levels in decades and game fish catch also declined. Algae blooms persist and the bloom ‘‘footprint’’ has expanded to include the eastern bay. (Madden et al. 2009 and references therein)
Thalassia testudinum grows in shallow coastal waters that are protected from strong wave surge. In clearer water it can be found at greater depths than in murky water. (Dineen 2001 and references therein)
Rudnick et al. (2005) emphasize that if the state of the seagrass community is to be used as a criterion to guide and assess the success of environmental restoration efforts, scientists and managers must specify the desirability of alternative states. Based on studies of historic changes of seagrass communities in Florida Bay and anecdotal information. it is likely that the Florida Bay of the 1970s and early 1980s, with lush T. testudinum and clear water, was probably a temporary and atypical condition. From an ecological perspective, restoration should probably strive for a more diverse seagrass community with lower T. testudinum density and biomass than during that anomalous period. (Rudnick et al. 2005 and references therein)
If efforts to restore the Everglades are successful, patterns of freshwater flow toward more natural patterns will drive Florida Bay’s seagrass community and trophic web toward its pre-drainage condition. Decreased salinity caused by increasing freshwater flow would likely have a direct effect on seagrass communities through physiological mechanisms, resulting in greater spatial heterogeneity of seagrass beds, a decrease in the dominance of T. testudinum, and an increase in coverage by other seagrass species. Decreased salinity would also likely decrease the infection of T. testudinum by the slime mold Labyrinthula. Light availability depends on phytoplankton growth and sediment resuspension, which in turn depend on nutrient availability, grazing, and stabilization of sediments by seagrass beds. (Rudnick et al. 2005)
Thalassia testudinum ist eine von zwei Pflanzenarten aus der Gattung Thalassia. Sie kommt im Golf von Mexiko und in der Karibik vor.
Die Rhizome sind verlängert und haben einen Durchmesser von 3 bis 6 Millimetern. Die Blätter messen 10 bis 60 × 0,4 bis 1,2 Zentimeter. Sie sind ganzrandig, nur gegen die Spitze hin ist der Rand gesägt. Blattadern sind 9 bis 15 vorhanden. Der männliche Blütenstand ist ein- bis dreiblütig. Die Blütenstandsachse ist 3 bis 7 Zentimeter lang. Die Ränder der Spathas sind auf einer Seite verwachsen. Der weibliche Blütenstand ist einblütig. Die Blütenstandsachse ist 3 bis 4 Zentimeter lang. Die Spathas sind auf beiden Seiten verwachsen. Die Stiele der männlichen Blüten sind 1,2 bis 2,5 Zentimeter lang. Es sind 9 Staubblätter vorhanden. Die weiblichen Blüten sind fast sitzend. Sie besitzen 7 oder 8 Griffel. Die Früchte sind hellgrün bis gelb-grün oder rot. Sie haben einen Durchmesser von 1,5 bis 2,5 Zentimetern und 5 bis 8 sich öffnende Fruchtklappen. Der Schnabel ist 4 bis 7 Millimeter lang.
Die Blütezeit reicht vom Frühling bis zum Sommer.
Die Chromosomenzahl beträgt 2n = 18.[1]
Thalassia testudinum kommt von den USA (Florida, Alabama, Louisiana und Texas) und Mexiko über Mittelamerika und die Westindischen Inseln bis Südamerika (Kolumbien, Venezuela) vor.[2] Die Art wächst auf Meeresgrund aus organischem Material, felsigem Material, Korallensand oder toten Korallenriffen von Meereshöhe bis in 10 Meter Tiefe in sehr klarem Wasser.
Die Art stellt evtl. eine der wichtigsten marinen Samenpflanzen an den Küsten von Karibik und Golf von Mexiko dar, beispielsweise zur Substratstabilisierung. So geht in Bereichen mit Beständen von Thalassia testudinum während eines Hurrikans nur sehr wenig Substrat verloren, verglichen mit Bereichen ohne die Art. Dies wird durch die Wurzeln und Rhizome erreicht, welche das Substrat festhalten, sowie durch die Blätter, welche die Strömungsgeschwindigkeit des Wassers reduzieren.
Thalassia testudinum wurde 1805 in einem Artikel von Charles König erstbeschrieben[3], der den Namen dem Botaniker Joseph Banks zuschrieb, weil seine Beschreibung auf Herbarmaterial und unveröffentlichte Manuskripte von Banks beruhte.
Thalassia testudinum ist eine von zwei Pflanzenarten aus der Gattung Thalassia. Sie kommt im Golf von Mexiko und in der Karibik vor.
Thalassia testudinum, commonly known as turtlegrass,[3] is a species of marine seagrass. It forms meadows in shallow sandy or muddy locations in the Caribbean Sea and the Gulf of Mexico.[4] Turtle grass and other seagrasses form meadows which are important habitats and feeding grounds. The grass is eaten by turtles and herbivorous fish, supports many epiphytes, and provides habitat for juvenile fish and many invertebrate taxa.
Thalassia testudinum is a perennial grass growing from a long, jointed rhizome. The rhizome is buried in the substrate 5 to 10 cm (2 to 4 in) deep, exceptionally down to 25 centimetres (9.8 in). Some nodes are leafless but others bear a tuft of several erect, linear leaf blades.[5][6] These are up to 30 centimetres (12 in) long and 2 cm (0.8 in) wide and have rounded tips. The flowers grow on short stalks in the axils of the leaves and are greenish-white, sometimes tinged pink, and are followed by seed pods.[7]
Turtle grass grows in meadows in calm shallow waters throughout the Caribbean Sea and the Gulf of Mexico, and as far north as Cape Canaveral in Florida. Extensive meadows can be formed on muddy sand, and coarse sandy and clayey seabeds, especially those with a calcareous content. This grass favours high-salinity waters with low turbidity, such as calm lagoons. It cannot grow in fresh water but some growth is possible at a salinity of 10 parts per thousand. The plant's preferred salinity range is 25 to 38.5 parts per thousand with a temperature range of 20 to 30 °C (68 to 86 °F). It is found from the low-tide mark down to depths of 30 metres (98 ft), depending on water clarity. It often grows in meadows with other seagrasses where it is the climax species.[6]
Its temporal range spans from the Middle Eocene to present.[8]
Turtle grass can reproduce both through vegetative and sexual reproduction. The main propagation method is by extension of the underground rhizome, or stem. This increase in rhizome length results in asexual ramets, or clonal colonies which are genetic replicates of the parent plant. Although asexual propagation results in an increase in the size of the turtle grass bed, extensive asexual reproduction limits genetic diversity and can put the meadow at severe risk if there is a disease outbreak.[6] It has been found that where plants have been damaged mechanically, such as by the propellers of boats, the cut ends of rhizomes are unable to grow and holes may develop in the turtle grass meadow.[5]
Turtle grass can also sexually reproduce through the production of underwater flowers and hydrophily. Turtle grass is dioecious, which means that there are separate male and female plants, each which produce an imperfect flower containing only one sex. Sexual reproduction takes place from April to July depending on location, though flowering has been observed during warm winters in Tampa Bay, Florida.[9][10][11] The small flowers are each borne by a peduncle. Female plants typically grow one green flower, while males often produce three to five pink or white flowers.[12][13][14] At night when male flowers are fully mature, they release mucilaginous pollen into the water column.[15][16][17] The following morning, female flowers open.
There are two methods of pollination: hydrophily and biotic pollination. In hydrophilic pollination, the pollen grains are carried through the water column by tides or currents and deposited upon an open pistillate flower. Underwater video cameras have more recently revealed crustaceans, polychaetes, and amphipods swimming towards open male flowers.[17][15][16][18] These creatures were attracted to the seagrass's nutritious mucilage—a carbohydrate-rich substance that houses pollen. As the invertebrates feed on the mucilage, excess pollen grains stick to their bodies. They move from flower to flower, feeding and spreading the pollen from male to female.
Seeds begin to develop in about 2–4 weeks if fertilization occurred.[6] Female turtle grass fruits develop into green capsule about 20–25 mm in diameter and can include 1-6 small seeds.[16][12] After about 8 weeks of growth, the fruit undergoes dehiscence (botany), which releases neutrally buoyant seeds into the water column.[14][12][10][6] If an event occurs producing significant water turbulence, an immature fruit may break off from the peduncle. This buoyant fruit acts as a transportation vessel as it continues to develop. The fruit will moved around by wind, currents, and tides until it eventually splits open to release the negatively buoyant seedlings into a new area. If the new location has favorable environmental conditions, the seedling will begin to grow. This is one way viviparous seedlings can start new patches of seagrass.[1]
Turtle grass and other seagrasses form meadows which are important habitats and feeding grounds. Associated seagrass species include Halophila engelmannii and Syringodium filiforme. Many epiphytes grow on the grasses, and algae, diatoms and bacterial films cover the surface of the leaf blades. The grass is eaten by turtles, herbivorous parrotfish, surgeonfish, and sea urchins, while the leaf surface films are a food source for many small invertebrates.[6] Decaying turtle grass leaves are responsible for the majority of detritus in meadow areas. This grass is subject to periodic dieback episodes in the Florida Bay area. One such episode in 1987 killed off a large proportion of the plants and the resulting increased sedimentation and greater growth of epiphytes on the remaining plants caused a secondary dieback event. The areas affected have since been reseeded and planted with rhizomes and have recovered. In general, the population of this grass is stable.[1]
Rhizomatous green algae in the genus Caulerpa often live among the grasses and many animal make seagrass meadows their home. These include bivalves and other molluscs, polychaete worms, amphipods, juvenile fish (which hide among the leaf blades), sea urchin, crabs, and caridean shrimps.[6]
Along with Thalassia hemprichii (which shares its common name with Thalassia testudinum), turtle grass makes its way into the aquarium trade and it may be cropped at 12 in/30 cm.[19]
Thalassia testudinum, commonly known as turtlegrass, is a species of marine seagrass. It forms meadows in shallow sandy or muddy locations in the Caribbean Sea and the Gulf of Mexico. Turtle grass and other seagrasses form meadows which are important habitats and feeding grounds. The grass is eaten by turtles and herbivorous fish, supports many epiphytes, and provides habitat for juvenile fish and many invertebrate taxa.
Thalassia testudinum, conocido comúnmente como hierba de tortuga [¿comúnmente dónde?], es una especie de planta que habita en el Caribe. Es un habitante del litoral y se caracteriza por formar praderas en lugares arenosos o fangosos poco profundos y con iluminación intensa.[3][4][5][6][7] Las praderas de Thalassia testudinum constituyen el hábitat de una gran diversidad de invertebrados tales como moluscos y crustáceos,[8] además de constituir parte fundamental de la dieta de la tortuga verde (Chelonia mydas) y del manatí (Trichechus manatus).[9]
Thalassia testudinum está conformada por un largo rizoma de crecimiento el cual pueden estar enterrado hasta a unos 25 centímetros de profundidad en el sustrato, pero habitualmente se encuentra a unos 5 a 10 cm por debajo de la superficie de hierba perenne. En algunos puntos del rizoma se producen nodos de donde salen las hojas, de dichos nodos puede salir una sola hoja presentar un racimo de varias hojas, las cuales son lineales y rectas como cintas.[10][11] Dichas hojas puedean alcanzar los 30 centímetros de largo y 2 cm de ancho y tienen puntas redondeadas. Las flores crecen en tallos cortos en las axilas de las hojas y son de color blanco verdoso, en ocasiones teñidas de rosa, y son seguidas por las vainas de semillas.[12]
La hierba tortuga presenta una amplia área de distribución por todo el Mar Caribe habiéndosele señalado para México el Golfo de México,[13] hacia el norte del estado de la Florida – Estados Unidos[14][15][16] y las islas Bermudas[14] En centro América se tiene reporte para Belice[17][18][16] para las islas del Caribe se ha señalado en las Bahamas[19]a las costas caribeñas de sur América se le ha señalado para Colombia[16][20] y Venezuela[21][8][14]
Thalassia testudinum habita en praderas en aguas tranquilas de arena gruesa fangosa, grueso y fondos marinos arcillosos, especialmente aquellos con un contenido calcáreo. Esta hierba la favorece aguas de alta salinidad con baja turbidez como las lagunas tranquilas. No puede crecer en agua dulce, pero puede tolerar aguas con una salinidad de 10 partes por mil. El intervalo preferido de la planta es de 25 a 38,5 partes por mil con un rango de temperatura de 20 a 30 ° C. Se encuentra desde línea de baja mar a profundidades de 30 metros, dependiendo de la claridad del agua. Con frecuencia crece en los praderas de pastos marinos con otras especies en los que es ella es la especie dominate.[3][4][7][11]
La Hierba tortuga presenta reproducción asexual y sexual. El principal método de propagación asexual es por aumento de la longitud de los rizomas. Esto tiene lugar principalmente en primavera y principios de verano, pero puede ocurrir en cualquier momento del año y los resultados en un aumento en el tamaño del área de la comunidad.[11] Se ha descubierto que donde las plantas han sido dañados mecánicamente, como puede ser mediante la hélices de los barcos, los extremos cortados de los rizomas son incapaces de crecer lo que ocasiona espacios vacíos en el área superficial de la comunidad.[10]
Inusualmente para el medio marino, la hierba de tortuga es una planta con flores. En la primavera y principios del verano, muchas plantas de la hierba de tortuga producen pequeñas flores en la base de las hojas. Las flores masculinas y femeninas crecen en plantas separadas. Las frutas se desarrollan en un período dos a cuatro semanas, y se desprenden alejándose por acción del oleaje y corrientes esta pueden flotar cerca de ocho semanas.[11] Las semillas son vivíparos[22] y puede iniciar nuevos parches de pastos marinos aunque se cree que el principal método de reproducción de esta planta es asexual.[11]
Thalassia testudinum y otros pastos marinos forman praderas que son hábitats importantes de alimentación. Especies marinas asociadas incluyen Halophila engelmannii y Syringodium filiforme. Muchos epifitas crecen en los pastos, y algas, diatomeas así como películas bacterianas cubren la superficie de las láminas de las hojas. La hierba es comida para las tortugas, peces loro herbívoro, pez cirujano y erizos de mar, mientras que las capas de la superficie de las hojas son una fuente de alimento para muchos invertebrados pequeños.[11] La descomposición hojas de hierba de tortuga es la responsable de la mayor parte del detritus en zonas de las pradera. Esta hierba está sujeto a episodios periódicos de muerte regresiva, como ocurrió en el área de Florida Bay. Uno de tales episodio en 1987 mató a una gran proporción de las plantas y el aumento de la sedimentación resultante y un mayor crecimiento de epifitas en las plantas restantes causó un evento de muerte regresiva secundaria. Las áreas afectadas ya han sido resembrado y plantadas con rizomas y se han recuperado. En general, la población de esta hierba es estable.[22]
El Rhizomatous de la alga verde del género Caulerpa suelen vivir entre las hierbas y muchos animales hacen de la praderas de esta fanerógama su casa. Estos incluyen los bivalvos y otros moluscos, gusanos poliquetos, anfípodos y peces juveniles que se esconden entre las láminas foliares, erizos de mar, cangrejos y camarones carideos.[8][11]
Thalassia testudinum suele formar una compleja comunidad donde se suelen distinguir diferentes tipos de asociaciones[4][23][24] destacando las siguientes:
Se ha observado que cuando ocurren huracanes las áreas oceánicas donde no existen praderas de Thalassia testudinum se pierde fácilmente el sustrato, mientras que por el contrario donde existen las hojas actúan reduciendo la velocidad de la corriente y rizomas situado en sedimentos permitir la estabilización del sustrato y limita severamente la erosión. Adicionalmente los restos de plantas muertas se acumulan en la zona tranquila formado entre las hojas de vida, una capa de sedimento más gruesa de sustrato o Suelo.[4][7][8][25]
Thalassia testudinum fue descrita científicamente en 1805 por el naturalista británico Joseph Banks en Annals of Botany, Volumen 2, publicado por el naturalista alemán Karl Dietrich Eberhard König.[26] Esta es la especie tipo del género Thalassia.[27]
Pradera de Thalassia testudinum con erizos de mar Tripneustes ventricosus en Grahams Harbour, Isla San Salvador, Bahamas.
Pradera de Thalassia testudinum en El Manglillo, Isla de Margarita estado Nueva Esparta - Venezuela.
Pradera de Thalassia testudinum en El Manglillo, Isla de Margarita estado Nueva Esparta - Venezuela.
Pradera de Thalassia testudinum en costa, del estado Florida - Estados Unidos.
Lobatus gigas fauna asociada a pradera de Thalassia testudinum
Triplofusus giganteus fauna asociada a pradera de Thalassia testudinum
Fasciolaria tulipa fauna asociada a pradera de Thalassia testudinum
Oreaster reticulatus fauna asociada a pradera de Thalassia testudinum
Thalassia testudinum, conocido comúnmente como hierba de tortuga [¿comúnmente dónde?], es una especie de planta que habita en el Caribe. Es un habitante del litoral y se caracteriza por formar praderas en lugares arenosos o fangosos poco profundos y con iluminación intensa. Las praderas de Thalassia testudinum constituyen el hábitat de una gran diversidad de invertebrados tales como moluscos y crustáceos, además de constituir parte fundamental de la dieta de la tortuga verde (Chelonia mydas) y del manatí (Trichechus manatus).
Thalassia testudinum également appelée « herbe à tortue », est une plante qui pousse sur les fonds marins tropicaux et forme des herbiers qui constituent des zones de frai pour les poissons. Elle est consommée par les tortues, d'où son nom vernaculaire. Cette plante est originaire de l'Atlantique ouest et vit dans les mers tropicales.
Cette espèce n'est pas une algue mais une plante à fleurs dont tous les organes sont normalement entièrement immergés. Elle possède un rhizome horizontal profondément enfoui sous les sédiments marins (jusqu'à 25 cm), de 3 à 6 mm de diamètre[1],[2]. Les feuilles vertes linéaires, dressées dans l'eau, poussent groupées autour d’une tige très courte. Elles mesurent 30 cm de longueur en moyenne (en fait entre 10 et 60 cm) pour 0,4 à 1,8 cm de largeur[1],[2]. Les bordures sont entières, les 9 à 15 nervures sont fines[2]. L'extrémité de la feuille est arrondie et présente des dentelures microscopiques[3].
La floraison a lieu en mai-juin, alors que les journées sont longues en jours longs (mai-juin), la fructification entre juin et juillet, et les fruits mûrs se détachent de la plante-mère au cours du mois d'août[4].
Comme les autres espèces du genre Thalassia, Thalassia testudinum est monoïque stricte, c'est-à-dire que les organes mâles et femelles sont situés dans des fleurs différentes d'un même individu. Ces fleurs sont bien visibles, blanc tirant sur le vert ou le rose jusqu'à rose pâle et sont dépourvues de pétales. Les fleurs staminées (mâles) se forment par inflorescence de 1 à 3 fleurs[2]. Chaque fleur porte 9 étamines libres dans lesquelles le pollen est englué dans une matrice gélatineuse ; la propagation de ce dernier se fera dans l'eau[2],[4]. Il n'y a qu'une seule fleur pistilée par inflorescence femelle. L'ovaire ne présente qu'une seule loge ; il est surmonté de 7 ou 8 styles[2].
Le fruit, de couleur verte à vert-jaune ou rouge, est sphérique et a une peau rugueuse, couverte de petites pointes. Il mesure de 1,5 à 2,5 cm de diamètre et s'ouvre en 5 à 8 valves irrégulières[2]. Les graines sont en forme de poire.
L'extension d'un banc de cette herbe se fait grâce à un marcottage naturel par le développement de l'extrémité des rhizomes.
Pour la reproduction sexuée, il a été récemment démontré que de petits invertébrés marins tels que les amphipodes et les polychètes participent à la pollinisation de cette espèce sous-marine[5].
L'Halodule beaudetti, qui vit dans les mêmes zones, a des feuilles d'un longueur moyenne plus courte, à l'extrémité moins arrondie et plus déchiquetée[4].
Thalassia hemprichii, autre espèce du même genre et elle aussi appelée "herbe à tortue", lui ressemble énormément mais vit en mer Rouge et dans le bassin Indo-Pacifique[4].
Cette espèce vit dans les mers bordant les Caraïbes et dans le golfe du Mexique ; elle pousse donc sur les côtes atlantiques des États-Unis (du Texas à la Floride), du Mexique, de l'Amérique centrale, des îles des Caraïbes et des Antilles, ainsi que de la Colombie et du Venezuela, en Amérique du Sud. Elle n'a pas été observée plus au nord que Cape Canaveral, en Floride[1].
Elle exige une salinité élevée et ne pousse pas dans les zones trop souvent battues par les vagues, bien qu'elle supporte une exondation et une exposition occasionnelle à l'air durant les marées basses de fort coefficient. Lorsque les eaux sont claires, elle peut se développer jusqu'à 20 m de profondeur[1], même si on la trouve plus fréquemment à moins de 10 m de profondeur[2]. Elle exige une épaisseur de sédiments suffisante pour permettre le développement de ses rhizomes[1] mais autrement, elle se développe sur des fonds marins variés (récifs morts, sable corallien, roches sédimentaires, vases, etc.)[2].
Les bancs de Thalassia testudinum sont souvent associés avec une autre herbe marine, Syringodium filiforme[4].
De nombreuses espèces marines se nourrissent de cette plante, s'abritent ou se reproduisent dans la zone de calme créée entre ses feuilles. En effet, plusieurs espèces marines herbivores se nourrissent de ses feuilles, notamment la tortue verte (Chelonia mydas)[1].
Les feuilles ralentissant le courant et les rhizomes implantés dans les sédiments permettent une stabilisation du substrat et limitent fortement son érosion. Les débris de végétaux morts s'accumulent dans la zone de calme ménagée par les feuilles vivantes, contribuant à l'épaississement de la couche de sédiments[2].
Thalassia testudinum a été décrite scientifiquement pour la première fois en 1805 par le naturaliste britannique Joseph Banks dans Annals of Botany, Volume 2, édité par le naturaliste allemand Karl Dietrich Eberhard König[6].
Il s'agit de l'espèce type du genre Thalassia[7].
Thalassia testudinum également appelée « herbe à tortue », est une plante qui pousse sur les fonds marins tropicaux et forme des herbiers qui constituent des zones de frai pour les poissons. Elle est consommée par les tortues, d'où son nom vernaculaire. Cette plante est originaire de l'Atlantique ouest et vit dans les mers tropicales.
Thalassia testudinum là một loài thực vật có hoa trong họ Hydrocharitaceae. Loài này được Banks & Sol. ex K.D.Koenig miêu tả khoa học đầu tiên năm 1805.[3] Nó mọc thành bãi trên các đáy cát hoặc bùn nông tại Biển Caribbe và Vịnh Mexico.[4]
Thalassia testudinum là một loài thực vật có hoa trong họ Hydrocharitaceae. Loài này được Banks & Sol. ex K.D.Koenig miêu tả khoa học đầu tiên năm 1805. Nó mọc thành bãi trên các đáy cát hoặc bùn nông tại Biển Caribbe và Vịnh Mexico.
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