| Cymodoceaceae | |
|---|---|
 | |
Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Monocots |
| Order: | Alismatales |
| Family: | Cymodoceaceae Vines[1] |
| Genera[2] | |
| |
Cymodoceaceae is afamily offlowering plants, sometimes known as the "manatee-grass family", which includes only marine species.[3]
The 2016APG IV does recognize Cymodoceaceae and places it in the orderAlismatales, in the clademonocots. The family includes five genera, totaling 17 species[4] occurring in tropical seas and oceans (so-calledseagrasses). According to theAP-Website it is doubtful if the familyRuppiaceae is distinct enough to be kept apart. The inclusion of the sole genusRuppia in Ruppiaceae in Cymodoceaceae is being considered. The plants in the three families Cymodoceaceae,Posidoniaceae andRuppiaceae form a monophyletic group.
Its fossil record shows that Cymodoceaceae was established in its current Indo-West Pacific distribution by the early Eocene and perhaps even during the late Paleocene.[5] Fossils ofThalassodendron auriculalopris den Hartog andCymodocea floridana den Hartog (both extant) were also found in west-central Florida and date back to the late middle Eucene.[6] Their age and lack of diversity speaks to an extremely slow rate of evolution within the Cymodoceaceae.[7]
Marine grasses families:Zosteraceae, Cymodoceaceae,Ruppiaceae andPosidoniaceae. Related families:Potamogetonaceae,Zannichelliaceae (not consistently).[citation needed]
Cymodoceaceae is one of four families to have developed filamentouspollen, along with Ruppiaceae, Zosteraceae, and Posidonaceae.[8] The pollen is assembled as long and thin grains rather than spheres, which increases its surface area when floating on the water. In addition, the pollen can more easily form pollen rafts, enabling distribution over a large surface area of water. The pollen isepihydrophilous (pollen distributed on the surface of the water) or hypohydrophilous (pollen distributed below the surface of the water) depending on the genera. There are three different methods used. Species inHalodule andCymodocea release pollen at low tide, where it floats and assembles into snowflake-like pollen rafts which then hopefully make contact with the stigmas when the tide starts coming back in.[9]Amphibolis andThalassodendron have pollen that is carried up to and then released upon the surface of the water byabscisent male flowers.Syringodium has pollen grains that are approximately the same density as seawater and form small clumps which move beneath the surface by submarine currents to the stigmas of female flowers.[9] This return to hypohydrophily is interpreted as a reversal to the ancestral state.
All species in Cymodoceaceae aredioecious. Although this occurs in about 75% of the seagrasses, it is a feature found in less than 5% of all angiosperms.[10] There are two leading theories regarding the prevalence of dioecy in Cymodoceaceae. The construction and reception of pollen rafts are bulky operations. To have either perfect flowers or bear both male and female flowers on one plant could interfere with successful fertilization. The other theory is it would ensure cross-pollination in an environment that would make self-pollination much more likely, a process that would limit the gene pool and make plants more susceptible to variable conditions or disease.[citation needed]
Two genera haveviviparous seedlings. The seeds ofAmphibolis andThalassodendron lack seed coats and do not store starch or other important nutrients. They instead latch onto the parent plant immediately after germination.[11] The seedling develops a footing tissue from the hypocotyl, which attaches to the parents through transfer cells. The seedlings develop leafy shoots over the course of 7–12 months before being released.Amphibolis seedlings develop a grappling apparatus which serves to anchor the seedling to a substrate once released whereas the seedlings ofThalassodendron are released from an enveloping bract. As the external wall of the footing tissue in the seeds is apoplastic, the seedlings can be considered parasitic on and also cytoplasmically isolated from the maternal tissue.[12]
| Kubitzki (ed. 1998[13]) | Watson & Dallwitz (delta-intkey)[14] | data.kew[15] | APWeb (mobot.org)[16] |
|---|---|---|---|
| Zosteraceae | |||
| 1.Zostera L. | Zostera | Zostera L. | Zostera L. (includingHeterozostera den Hartog,Macrozostera Tomlinson & Posluzny,Nanozostera Tomlinson & Posluzny,Zosterella J. K. Small) |
| 2.Heterozostera den Hartog | Heterozostera | Heterozostera (Setch.) Hartog | (inZostera) |
| 3.Phyllospadix Hook. | Phyllospadix | Phyllospadix Hook. | Phyllospadix J. D. Hooker |
| Cymodoceaceae | |||
| 1.SyringodiumKütz | Syringodium | Syringodium Kutz. (includingPhycoschoenus (Asch.) Nakai ) | (inCymodocea) |
| 2.Halodule Endl. | Halodule | Halodule Endl. | Halodule Endlicher |
| 3.Cymodocea König | Cymodocea | Cymodocea K.Koenig | Cymodocea König (includingAmphibolis Agardh ?,Syringodium Kütz. ?,Thalassodendron den Hartog ?) |
| 4.Amphibolis Agardh | Amphibolis | Amphibolis C.Agardh (includingPectinella J.M.Black) | (inCymodocea) |
| 5.Thalassodendron de Hartog | (name not found) | Thalassodendron Hartog | (inCymodocea) |
| Ruppiaceae | |||
| Ruppia L. | Ruppia | (inRuppia L. inPotamogetonaceae) | Ruppia L. |
| Posidoniaceae | |||
| Posidonia König | Posidonia | Posidonia K.Koenig | Posidonia König |
| Species | Distribution |
|---|---|
| Cymodocea angustata | Northwestern Australia |
| Cymodocea nodosa | Mediterranean, Canary Islands, NW Africa |
| Cymodocea rotundata | Shores of Indian Ocean, Red Sea, South China Sea, Pacific Ocean |
| Halodule bermudensis | Bermuda |
| Halodule ciliata | Panama |
| Halodule emarginata | Southeastern Brazil |
| Halodule pinifolia | Southeast Asia, Ryukyu Islands, Fiji, Caroline Islands |
| Halodule uninervis | Indian and Pacific Oceans, Red Sea, Persian Gulf, Bay of Bengal |
| Halodule wrightii | Atlantic Ocean, Caribbean, Gulf of Mexico, Africa, West Indies |
| Oceana serrulata | Shores of Indian Ocean, Red Sea, South China Sea, Pacific Ocean |
| Syringodium filiforme | Gulf of Mexico, Caribbean |
| Syringodium isoetifolium | Indian and Pacific shores |
| Amphibolis antarctica | South and Western Australia |
| Amphibolis griffithii | South and Western Australia |
| Thalasodendron leptocaule | Mozambique, KwaZulu-Natal |
| Thalassodendron ciliatum | Indian Ocean, shores of Africa, Asia, Australia, Micronesia |
| Thalassodendron pachyrhizum | Western Australia |
| National | |
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| Other | |
