Thalassia testudinum

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Thalassia testudinum
Temporal range: Middle Eocene–Present
Thalassia testudinum (turtle grass) (South Pigeon Creek estuary, San Salvador Island, Bahamas) 3 (15859724719).jpg
Turtle grass meadow in San Salvador Island
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Monocots
Order: Alismatales
Family: Hydrocharitaceae
Genus: Thalassia
Species:
T. testudinum
Binomial name
Thalassia testudinum

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.

Contents

Description

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]

Distribution and habitat

Thalassia testudinum up close Thalassia testudinum (turtle grass) (South Pigeon Creek estuary, San Salvador Island, Bahamas) 2 (16043820341).jpg
Thalassia testudinum up close
Seagrass bed with dense Thalassia testudinum and immature queen conch) Strombus gigas Rice Bay.jpg
Seagrass bed with dense Thalassia testudinum and immature queen conch)
Thalassia testudinum with sponge and anemone GOPR8848.jpg
Thalassia testudinum with sponge and anemone
Thalassia testudinum nearby Archer Key, FL

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]

Reproduction

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 be 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]

Ecology

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]

Relationship to humans

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]

Related Research Articles

<span class="mw-page-title-main">Seagrass</span> Plants that grow in marine environments

Seagrasses are the only flowering plants which grow in marine environments. There are about 60 species of fully marine seagrasses which belong to four families, all in the order Alismatales. Seagrasses evolved from terrestrial plants which recolonised the ocean 70 to 100 million years ago.

<span class="mw-page-title-main">Hydrocharitaceae</span> Family of aquatic plants

Hydrocharitaceae is a flowering plant family including 16 known genera with a total of ca 135 known species, that including a number of species of aquatic plant, for instance the tape-grasses, the well known Canadian waterweed, and frogbit.

<span class="mw-page-title-main">Seagrass meadow</span> Underwater ecosystem

A seagrass meadow or seagrass bed is an underwater ecosystem formed by seagrasses. Seagrasses are marine (saltwater) plants found in shallow coastal waters and in the brackish waters of estuaries. Seagrasses are flowering plants with stems and long green, grass-like leaves. They produce seeds and pollen and have roots and rhizomes which anchor them in seafloor sand.

<span class="mw-page-title-main">Cymodoceaceae</span> Family of aquatic plants

Cymodoceaceae is a family of flowering plants, sometimes known as the "manatee-grass family", which includes only marine species.

<i>Phyllospadix scouleri</i> Species of aquatic plant

Phyllospadix scouleri, or Scouler's surfgrass, is a flowering marine plant in the family Zosteraceae. It is native to the coastline of western North America from the Alaskan panhandle to Baja California.

<i>Halophila johnsonii</i> Species of aquatic plant

Halophila johnsonii, or Johnson's seagrass, is a small, asexual seagrass in the family Hydrocharitaceae. It occurs only on the southeastern coast of Florida, and was the first marine plant listed on the United States endangered species list, though it was removed from listing in April 2022. Female flowers have been observed, but even with decade long observational studies, neither male flowers nor seed have ever been observed.

The Seagrasses of Western Australia are submerged flowering plants found along the coast, around islands, and in Estuaries of Western Australia. The region contains some of the largest seagrass meadows in the world, and is the most diverse in the number of species. The variety of habitats along its western and southern coasts is often soft sands in shallow subtropical waters, ideal for these plants.

<i>Enhalus</i> Genus of aquatic plants

Enhalus is a monotypic genus of marine flowering plants. The sole species is Enhalus acoroides. Enhalus is a large seagrass native to coastal waters of the tropical Indian and Western Pacific Oceans. It is the only species of seagrass that does aerial surface pollination in which the pollen and the styles remain dry. Enhalus is surface pollinated with male flowers that detach from the plant to float on the surface until they reach a female flower where pollination can occur. Enhalus acoroides is considered a slow-growing, "climax" species.

<i>Thalassia</i> (plant) Genus of aquatic plants

Thalassia is a marine seagrass genus comprising two known species.

<span class="mw-page-title-main">Colombier, Saint Barthélemy</span> Quartier in Saint Barthélemy, France

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<i>Cymodocea nodosa</i> Species of plant in the family Cymodoceaceae

Cymodocea nodosa is a species of seagrass in the family Cymodoceaceae and is sometimes known as little Neptune grass. As a seagrass, it is restricted to growing underwater and is found in shallow parts of the Mediterranean Sea and certain adjoining areas of the Atlantic Ocean.

<i>Halophila engelmannii</i> Species of plant in the family Hydrocharitaceae

Halophila engelmannii is a species of seagrass in the Hydrocharitaceae family. It is referred to by the common names star grass and Engelmann's seagrass and grows underwater on shallow sandy or muddy sea floors. It is native to the Bahamas, the Cayman Islands, Costa Rica, Cuba, the Gulf Coast of the United States, the Gulf Coast of Mexico, Puerto Rico, and Trinidad and Tobago.

<i>Halophila decipiens</i> Species of aquatic plant

Halophila decipiens, commonly known as Caribbean seagrass or paddle grass, is a seagrass in the family Hydrocharitaceae. It grows underwater on sandy or muddy sea floors in shallow parts of tropical seas.

<i>Halodule wrightii</i> Species of plant in the family Cymodoceaceae

Halodule wrightii is an aquatic plant in the Cymodoceaceae family. It is referred to by the common names shoal grass or shoalweed, and is a plant species native to seacoasts of some of the warmer oceans of the world.

<i>Zostera noltii</i> Species of plant

Zostera noltii is a species of seagrass known by the common name dwarf eelgrass. It is found in shallow coastal waters in north western Europe, the Mediterranean Sea, Black Sea, Caspian Sea and Aral Sea and on islands in the Atlantic off the coast of northwest Africa. It is an important part of the intertidal and shallow subtidal ecosystems of estuaries, bays and lagoons.

<i>Halodule uninervis</i> Species of plant in the family Cymodoceaceae

Halodule uninervis is a species of seagrass in the family Cymodoceaceae. It is native to the western Pacific and Indian Oceans. Common names include narrowleaf seagrass in English and a'shab bahriya in Arabic.

Lobophora variegata is a species of small thalloid brown alga which grows intertidally or in shallow water in tropical and warm temperate seas. It has three basic forms, being sometimes ruffled, sometimes reclining and sometimes encrusting, and each form is typically found in a different habitat. This seaweed occurs worldwide. It is the type species of the genus Lobophora, the type locality being the Antilles in the West Indies.

Zostera novazelandica Setchell is a species of seagrass in the family Zosteraceae found on the shores of New Zealand. It is regarded as a distinct species by some authors but considered as a synonym of Zostera muelleri Irmisch ex Ascherson by others. The Maori names for Zostera novazelandica are karepō, nana, rehia, and rimurehia.

<i>Zostera muelleri</i> Species of plant in the family Zosteraceae

Zostera muelleri is a southern hemisphere temperate species of seagrass native to the seacoasts of South Australia, Victoria and Tasmania. and New Zealand. Today, Zostera muelleri can be found in regions of Australia, New Zealand, and Papua New Guinea, as well as areas of the eastern Indian Ocean, and the southwest and western central Pacific Ocean. Zostera muelleri is a marine angiosperm, and is commonly referred to as eelgrass or garweed. It is a fast growing and readily colonizing species that serves as a feeding ground for wading birds and aquatic animals, and a breeding ground for juvenile fish and shrimp species.

Halophila baillonis is a species of aquatic plant in the family Hydrocharitaceae. It is referred to by the common name clover grass. It is native to Brazil, Cayman Islands, Colombia, Costa Rica, Jamaica, Leeward Islands, Netherlands Antilles, Panama, Puerto Rico, Trinidad and Tobago, and Venezuela. It is listed on the IUCN Red List as "vulnerable" due to its naturally rare occurrence and fragmented populations.

References

  1. 1 2 3 Short, F.T.; Carruthers, T.J.R.; van Tussenbroek, B.; Zieman, J. (2010). "Thalassia testudinum". IUCN Red List of Threatened Species . 2010: e.T173346A6995927. doi: 10.2305/IUCN.UK.2010-3.RLTS.T173346A6995927.en . Retrieved 30 June 2021.
  2. ↑ Guiry, Michael D. (2012). Guiry MD, Guiry GM (eds.). "Thalassia testudinum Banks ex König, 1805". AlgaeBase. National University of Ireland, Galway . World Register of Marine Species . Retrieved 2012-11-07.
  3. ↑ USDA, NRCS (n.d.). "Thalassia testudinum". The PLANTS Database (plants.usda.gov). Greensboro, North Carolina: National Plant Data Team. Retrieved 9 December 2015.
  4. ↑ Guiry, M. D.; Guiry, G. M. (2012). "Thalassia testudinum Banks ex König". AlgaeBase. Retrieved 2012-11-08.
  5. 1 2 Colin, Patrick L. (1978). Marine Invertebrates and Plants of the Living Reef . T.F.H. Publications. pp.  474–475. ISBN   0-86622-875-6.
  6. 1 2 3 4 5 6 7 Dineen, J. (2001-07-25). "Thalassia testudinum (Turtle grass)". Smithsonian Marine Station at Fort Pierce. Retrieved 2012-11-07.
  7. ↑ "Turtle-grass (Thalassia testudinum)". Interactive Guide to Caribbean Diving. Marine Species Identification Portal. Retrieved 2012-11-08.
  8. ↑ den Hartog, C. (2005). "Taxonomy and biogeorgraphy of seagrasses". In Larkum, Anthony W.D.; Duarte, Carlos; Orth, Robert J. (eds.). Seagrasses: Biology, Ecology and Conservation. Springer-Verlag New York, LLC. ISBN   978-1-4020-2942-4.
  9. ↑ Zieman JC. 1975. Seasonal variation of turtle grass, Thalassia testudinum Konig, with reference to temperature and salinity effects. Aquatic Botany. 1: 107-123.
  10. 1 2 Moffler MD, Durako MJ and Grey WF. 1981. Observations on the reproductive ecology of Thalassia testudinum (Hydrocharitaceae). Aquatic Botany. 10: 183-187.
  11. ↑ Phillips RC, McMillan C, Bridges KW. 1981. Phenology and reproductive physiology of Thalassia testudinum from the western tropical Atlantic. Aquatic Botany. 11: 263-277.
  12. 1 2 3 Orpurt PA and Boral, LL. 1964. The flowers, fruits and seeds of Thalassia testudinum Konig. Bulletin of Marine Science. 14: 296-302.
  13. ↑ Tomlinson P.B. 1969. On the morphology and anatomy of turtle grass, Thalassia testudinum (Hydrocharitaceae). III. Floral morphology and anatomy. Bulletin of Marine Science. 19: 286-305.
  14. 1 2 Darnell and Dunton (2016). "Reproductive phenology of the subtropical Thalassia testudinum (turtle grass) and Halodule wrightii (shoal grass) in the northwest Gulf of Mexico". Botanica Marina. 59 (6): 473–483.
  15. 1 2 van Tussenbroek, Brigitta I.; Wong, J. G. Ricardo; Márquez-Guzman, Judith (2008-02-07). "Synchronized anthesis and predation on pollen in the marine angiosperm Thalassia testudinum (Hydrocharitaceae)". Marine Ecology Progress Series. 354: 119–124. doi: 10.3354/meps07212 .
  16. 1 2 3 van Tussenbroek, Brigitta I.; Villamil, Nora; Márquez-Guzmán, Judith; Wong, Ricardo; Monroy-Velázquez, L. Verónica; Solis-Weiss, Vivianne (2016). "Experimental evidence of pollination in marine flowers by invertebrate fauna". Nature Communications. 7 (1): 12980. doi:10.1038/ncomms12980. PMC   5056424 .
  17. 1 2 van Tussenbroek, Brigitta I.; Monroy-Velazquez, L. Verónica; Solis-Weiss, Vivianne (2012-11-26). "Meso-fauna foraging on seagrass pollen may serve in marine zoophilous pollination". Marine Ecology Progress Series. 469: 1–6. doi: 10.3354/meps10072 .
  18. ↑ "Scientists Discover an Underwater Pollinator | Hakai Magazine". Hakai Magazine. Retrieved 2017-02-01.
  19. ↑ (2012): Beautiful Seagrasses – Keeping True Flowering Plants in Your Marine Aquarium|Reefland.com. . In: Reefland.com.
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