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editMolgula, or sea grapes, are very common, globular, individual marine tunicates roughly the size of grapes.[1] Molgula are a genus of the class ascidians, having many species sized from 20-50 mm and that has a life cycle with a tailed tadpole stage or without a tailed tadpole stage.[2] Molgula are sessile invertebrates that grows on substrates and are always found existing alone.[3] There are over one hundred species of molgulids with a vast majority of them in the Northern and Southern parts of the world with a few along the equator.[4][3] All species of Molgula are suspension feeders and will have the highest population in areas with high amounts of small particles to feed on.[4]
Distribution and Habitats
In the western Atlantic Ocean, they range from the Arctic to North Carolina, to the center of the United States Eastern Seaboard.[5] The genus Molgula has a wide distribution with Molgula kolaensis being found in the Arctic and the majority being found in pacific or Atlantic waters.[6] Molgula that do not have a tadpole stage and have indirect development are located mostly in northern parts of bodies of water.[6] Molgula can inhabit sandy environments to which they are unattached or attached; they also attach to hard rock surfaces.[6] The depth at where they are found varies as the Molgua pugetiensis is found at 15 - 30 meters and Molgula pacifica can be found at 4 meters deep.[6] [7]The species Molgula manhattensis and Molgula ampulloides can be found along shallow water and shorelines where tides can change the water levels.[2]
Morphology and Development
They are translucent with two protruding siphons. They are found subtidally, attached to slow-moving submerged objects or organisms. All species of Molgula have a fluid-filled structure called the renal sac.[8] The renal sac contains nitrogenous wastes, solid concretions composed of weddellite and calcite,[9] and an apicomplexan symbiont called Nephromyces.[10] To further expand on the animals structures, they contain a layer of tunic giving rise to structures called papillae whose function will be discussed in the Feeding Behavior section.[11] Additionally with the exception of the slight variations existing within the species in terms of forms and structures, majority of them exist in shades in between green and yellow. For instance Molgula griffithsii consists of the structures with blue coloration while Molgula provisionales is of a light yellow coloration.[11]
Furthermore, to delve into the development of the genus Molgula has a wide range of variations among in different species.[2] Many of them are hermaphroditic and can self-fertilize such as Molgula pacifica which are brooded.[3][7] They can be viviparous like Molgula citrina, from which a larva will pop out, or can have an oviparous egg like Molgula oculata.[2] The way they hatch from the egg can vary such as digestion of the egg membrane or breaking out of it.[2] Molgula are unique ascidians as they can have a tailed tadpoles larvae like most ascidians or an anural larvae.[3] The tailless larvae have reduced characteristics like notochord and tail muscle cells.[4] Molgula have holoblastic cleavage which is present In the species M. pacifica.[4]
Molgula pacifica lacks the tadpole stage in its life cycle meaning it has anural development. ( 6 ) Most ascidians undergo urodele development meaning that they have a tailed larval stage. The oocytes and fertilized eggs lack a perivitelline space and test cells that differentiate them with those of the urodele species. Embryos are also similar to urodele ascidians in that they have a similar cleavage pattern and also begin gastrulation at the vegetal pole. There is more modification in cell shape and movement during gastrulation. The muscle cells were absent in the posterior region which is the reason for the lack of the larval tail. The M. pacifica don't have acetylcholinesterase activity on the other hand the urodele species show a high level of acetylcholinesterase activity in the tail muscles. The developmental changes such as modifying the gastrulation and muscle development lead to the elimination of tadpole stage.
Evolutionary Changes
In Molgula occulata there is an evolutionary loss of sensory organ associated melanocytes known as melanogenesis.(7) Melanocytes are cells that produce pigments. The Tyrosinase family genes are crucial for melanogenesis. Members of Molgula occulta have unpigmented and tailless larvae on the other hand members of Molgula oculata have tails that are pigmented. It is found that the ability for melanogenesis comes down to the ability of the Tyrosinase genes to encode for functional proteins. There is a strong correlation between the pseudogenization of the Tyrosinase genes and the absence of pigmentation in the Molgula. Independent mutations in two of the Tyrosinase family genes which causes them to make inactive enzymes. These inactive enzymes are the reason for the loss of pigmentation even though it has the precursors required. The tail loss has been present in 20 tunicate species of the family Mogulidae and has occurred independently.
Evolutionary Changes
In Molgula occulata there is an evolutionary loss of sensory organ associated melanocytes known as melanogenesis. [12] Melanocytes are cells that produce pigments. The Tyrosinase family genes are crucial for melanogenesis. Members of Molgula occulta have unpigmented and tailless larvae on the other hand members of Molgula oculata have tails that are pigmented. It is found that the ability for melanogenesis comes down to the ability of the Tyrosinase genes to encode for functional proteins. There is a strong correlation between the pseudogenization of the Tyrosinase genes and the absence of pigmentation in the Molgula. Independent mutations in two of the Tyrosinase family genes which causes them to make inactive enzymes. These inactive enzymes are the reason for the loss of pigmentation even though it has the precursors required. The tail loss has been present in 20 tunicate species of the family Mogulidae and has occurred independently.
[14] Lower case sentences are from original article.
Article body
editThey are translucent with two protruding siphons. They are found subtidally, attached to slow-moving submerged objects or organisms. All species of Molgula have a fluid-filled structure called the renal sac.[16] The renal sac contains nitrogenous wastes, solid concretions composed of weddellite and calcite,[17] and an apicomplexan symbiont called Nephromyces.[18]
References
edit- ↑ "WoRMS - World Register of Marine Species - Molgula Forbes, 1848". www.marinespecies.org. Retrieved 2025-02-24.
- 1 2 3 4 5 Berrill, N. J. (1928-02). "The Identification and Validity of Certain Species of Ascidians". Journal of the Marine Biological Association of the United Kingdom. 15 (1): 159–175. doi:10.1017/S0025315400055600. ISSN 1469-7769.
{{cite journal}}: Check date values in:|date=(help) - 1 2 3 4 Huber, Jennifer L.; da Silva, Karen Burke; Bates, William R; Swalla, Billie J. (2000-12). "The evolution of anural larvae in molgulid ascidians". Seminars in Cell & Developmental Biology. 11 (6): 419–426. doi:10.1006/scdb.2000.0195.
{{cite journal}}: Check date values in:|date=(help) - 1 2 3 4 Sawada, Hitoshi; Yokosawa, H.; Lambert, C. C., eds. (2001). The biology of ascidians. Tokyo, [Japan]: Springer. ISBN 978-4-431-66982-1.
- ↑ Andrew J. Martinez (2003). Marine Life of the North Atlantic: Canada to New England. Aqua Quest Publications. ISBN 9781881652328. Retrieved 2007-02-17.
- 1 2 3 4 Maliska, Max E.; Swalla, Billie J. (2010-12). "Molgula pugetiensis is a Pacific Tailless Ascidian Within the Roscovita Clade of Molgulids". The Biological Bulletin. 219 (3): 277–282. doi:10.1086/BBLv219n3p277. ISSN 0006-3185.
{{cite journal}}: Check date values in:|date=(help) - 1 2 Young, Craig M.; Gowan, Richard F.; Dalby, James; Pennachetti, Catherine A.; Gagliardi, David (1988-02). "Distributional Consequences of Adhesive Eggs and Anural Development in the Ascidian Molgula pacifica (Huntsman, 1912)". The Biological Bulletin. 174 (1): 39–46. doi:10.2307/1541757. ISSN 0006-3185.
{{cite journal}}: Check date values in:|date=(help) - ↑ Van Name, Willard Gibbs (1945). "The North and South American ascidians". Bulletin of the American Museum of Natural History. 84. hdl:2246/1186.
- ↑ Saffo, Mary Beth; Lowenstam, Heinz A. (1978-06-09). "Calcareous Deposits in the Renal Sac of a Molgulid Tunicate". Science. 200 (4346): 1166–1168. doi:10.1126/science.200.4346.1166. ISSN 0036-8075. PMID 17745108. S2CID 33253067.
- ↑ "Malaria, Sea Grapes, and Kidney Stones: A Tale of Parasites Lost - The Loom". The Loom. 2010-08-24. Retrieved 2017-08-02.
- 1 2 "https://invasions.si.edu/nemesis/species_summary/159557#:~:text=Molgula%20manhattensis,%20also%20known%20as,West%20Coast%20of%20North%20America". invasions.si.edu. Retrieved 2025-03-24.
{{cite web}}: External link in|title= - 1 2 Racioppi, Claudia; Valoroso, Maria Carmen; Coppola, Ugo; Lowe, Elijah K.; Brown, C. Titus; Swalla, Billie J.; Christiaen, Lionel; Stolfi, Alberto; Ristoratore, Filomena (2017-07-18). "Evolutionary loss of melanogenesis in the tunicate Molgula occulta". EvoDevo. 8 (1). doi:10.1186/s13227-017-0074-x. ISSN 2041-9139.
{{cite journal}}: CS1 maint: unflagged free DOI (link) - ↑ Chen, Yiyong; Gao, Yangchun; Huang, Xuena; Li, Shiguo; Zhan, Aibin (2021). "Local environment-driven adaptive evolution in a marine invasive ascidian (Molgula manhattensis)". Ecology and Evolution. 11 (9): 4252–4266. doi:10.1002/ece3.7322. ISSN 2045-7758. PMC 8093682. PMID 33976808.
{{cite journal}}: CS1 maint: PMC format (link) - ↑ Saffo, Mary Beth; Davis, Wendy L. (1982-02). "Modes of infection of the ascidian molgula manhattensis by its endosymbiont nephromyces giard". The Biological Bulletin. 162 (1): 105–112. doi:10.2307/1540974. ISSN 0006-3185.
{{cite journal}}: Check date values in:|date=(help) - ↑ Bates, William R.; Mallett, Joan E. (1991-09-01). "Ultrastructural and histochemical study of anural development in the ascidian Molgula pacifica (Huntsman)". Roux's archives of developmental biology. 200 (4): 193–201. doi:10.1007/BF00361337. ISSN 1432-041X.
- ↑ Van Name, Willard Gibbs (1945). "The North and South American ascidians". Bulletin of the American Museum of Natural History. 84. hdl:2246/1186.
- ↑ Saffo, Mary Beth; Lowenstam, Heinz A. (1978-06-09). "Calcareous Deposits in the Renal Sac of a Molgulid Tunicate". Science. 200 (4346): 1166–1168. doi:10.1126/science.200.4346.1166. ISSN 0036-8075. PMID 17745108. S2CID 33253067.
- ↑ "Malaria, Sea Grapes, and Kidney Stones: A Tale of Parasites Lost - The Loom". The Loom. 2010-08-24. Retrieved 2017-08-02.