In case you have not figured it out yet, today's post will be talking about jellyfishes! I have always been curious about jellyfishes, where they come from and how they multiply. In this posts, hopefully you will learn something new about jellyfishes!
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| Jellyfishes housed at the South East Asian Aquarium |
Jellyfishes have two different forms in life, the polyps and the medusa. The medusa are more commonly recognized as jellyfishes, an umbrella like head with many tentacles streaming along after it as it bobs through the water. The polyps are a hidden side of the jellyfish life cycle many are oblivious about. In fact, how a jellyfish begins its life is as a polyp!
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| Life Cycle of a Jellyfish |
Polyps, also known as scyphistomas, are small structures that fix themselves onto hard surfaces. Scyphistomas are usually found on the ocean floor, meaning they are benthic, and have tentacles to help it trap food and feed. These polyps then start to feed and mature and even multiply. Polyps were able to multiply through the formation of podocyst, these are able to bud off from one another developing into new polyps. This means that they reproduce asexually and the two polyps are genetically similar. Once matured, polyps can then start producing ephyras, which will mature into medusas, adult jellyfishes, within a matter of weeks. The process at which the polyp constricts itself to release the ephyras is known as strobilation. A single polyp can stobilate multiple times and is estimated to produce up to 15 ephyras per month. After strobilation, polyps will resume their daily business of eating and growing.
Adult jellyfishes then go through the familiar process of sexual reproduction via external fertilization of the eggs. These eggs develop into larva and attach themselves onto hard surfaces, eventually, growing into polyps!
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| Jellyfish Bloom off the Coasts of New Zealand |
In recent years, there have been reports of various increase in populations of jellyfishes. Cause of this phenomenon come from a variety of possible factors, all of which seemingly leading back to human interference with the ecosystem.
From introduction of an invasive species of jellyfish into a ecosystem, to less competition for food due to over-fishing, and even eutrophication of the water, leading to conditions that favor the growth of jellyfishes. These high populations of jellyfishes adversely affect the ecosystem through uncontrolled predation of the lower trophic levels. This also means that less fish will be present in the waters and thus destroy fishing grounds, affecting the supply of fish to the market. Beaches that the blooms occur at will also have to be closed down for the safety of the swimmers, affecting the economy of the area.
For a surprisingly transparent entity, it still holds many mysteries regarding its growth. This is especially true for the polyp phase of the life cycle. Thus, to understand how to prevent such blooms from getting out of hand, is essential to that scientist continue to study the jellyfish.
From introduction of an invasive species of jellyfish into a ecosystem, to less competition for food due to over-fishing, and even eutrophication of the water, leading to conditions that favor the growth of jellyfishes. These high populations of jellyfishes adversely affect the ecosystem through uncontrolled predation of the lower trophic levels. This also means that less fish will be present in the waters and thus destroy fishing grounds, affecting the supply of fish to the market. Beaches that the blooms occur at will also have to be closed down for the safety of the swimmers, affecting the economy of the area.
For a surprisingly transparent entity, it still holds many mysteries regarding its growth. This is especially true for the polyp phase of the life cycle. Thus, to understand how to prevent such blooms from getting out of hand, is essential to that scientist continue to study the jellyfish.
References
Deretsky, Z. (2010). Life cycle of a jellyfish. [diagram]
Retrieved from:
Last accessed 5 Sept 2015
[Digital photograph of jellyfish bloom]
Retrieved from: http://phys.org/news/2014-05-jellyfish-blooms-calm.html
Last accessed 5 Sept 2015
Mills, C. (2001). Jellyfish blooms: are populations increasing globally in response to changing ocean conditions?. Hydrobiologia, 451, pp.55-68.
Last accessed 5 Sept 2015
Schiariti, A., Kawahara, M., Uye, S. and Mianzan, H. (2008). Life
cycle of the jellyfish Lychnorhiza lucerna (Scyphozoa: Rhizostomeae).
Marine Biology, 156(1), pp.1-12.
Retrieved from:
Last accessed 5 Sept 2015
Last accessed 5 Sept 2015
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