By Ashley Ball On the ocean floor there is a marine animal that greatly resembles a writing utensil. However this animal doesn't have any ink in it but it does a have a name, it is called sea pen and for obvious reason. Do not let its small size and its lack of defenses fool you there is a lot more to this animal then meets the eye. To begin sea pen belongs to the order Pennatulacea in the class Anthozoa in the phylum Cnidaria (The Editors, 1). An important characteristic of the class Anthozoa is that it's the only class within the phylum Cnidaria that does not have a medusa stage in their development (Anthozoa,1). In addition Anthozoa of the four classes of phylum Cnidaria has by far the most species in it topping out at about six thousand (Anthozoa,1). The word Anthozoa means “flower animals” which is very accurate in the way they look (Anthozoa,1). While the sea pen looks more like a pen it still could easily just pass as a flower even though it is actually an invertebrate. Other invertebrates in this category are sea anemones, corals and sea pansies among many others (Anthozoa, 1). Sea pen is found on muddy or sandy seafloors (Sea Pen, 1). They range anywhere from the Gulf of Alaska to southern California at depths of forty five feet to two hundred and twenty five feet (Sea Pen, 1). Sea pen consists of a lower part or the peduncle which holds it in the mud or the sand and an upper part of the rachis which has many branches bearing a very wide range of polyps (The Editors ,1). Polyps are hollow stalks with a mouth and tentacles sticking out on the open end (The Editors, 1). Polyps typically have mouths which are surrounded by tentacles (The Editors Polyps,1). These tentacles capture prey around them and pull them into their mouth to eat (The Editors Polyps,1). They feed on small organisms that are around them using this process mentioned in the previous sentence (The Editor, 1). The central stalk of the sea pen is known as the primary or axial polyp (The Editor, 1). A sea pen can contain anywhere from a few polyps or up to thirty five thousand of them (Editor,1). Sea pen come in a variety of colors including yellow, orange, red, brown (The Editor, 1). Sea pens have an amazing characteristic in that they can deflate or inflate by getting rid of or taking in water around them by the connected hollow canals of the polyps (The Editor, 1). Another unique characteristic of the sea pen is when they are stimulated in any way or touched by anything or anyone they glow (The Editor, 1). This process is called bioluminescence. This results from a chemical reaction in which the conversion of chemical energy to radiant energy is almost one hundred efficient (The Editor Bioluminescence, 1). This reaction causes it not to give off that much heat so it is known as cold heat or bioluminescence (The Editor Bioluminescence, 1). Sea pens use this chemical reaction to protect themselves and deter predators which is an effective method since they can not move around or fight back in the typical sense. Their primary predators are nudibranchs and sea stars (Retrieved, 1). Sea pens also bury themselves in the sand during the daytime and during the night time they come out at night time to acquire food typically plankton (Retrieved , 1). Sea pen populations in some places are declining one of these places being in the Puget Sound in Washington (Sea Pen, 1). Scientist are not entirely for sure why they are disappearing but they think that their lack of presence indicates an ecosystem in trouble (Sea Pen, 1). The fact that they are disappearing can wreck havoc on the food chain definitely at the top of the food chain (Sea Pen, 1). In conclusion sea pen are a marine animal that has a lot going for it. Between the bioluminescence and how it buries itself and feeds and protects itself. Makes this animal a lot more than meets the eye. It is however in danger and even though scientists do not exactly know why it is disappearing but as always we need to protect our oceans and not dump thing into the oceans. We must protect our oceans. Works Cited The Editors of Encyclopædia Britannica. (2010, July 26). Sea pen. Retrieved October 30, 2017, from https://www.britannica.com/animal/sea-pen Anthozoa. (n.d.). Retrieved October 30, 2017, from http://www.newworldencyclopedia.org/entry/Anthozoa The Editors of Encyclopædia Britannica. (2014, October 22). Polyp. Retrieved October 30, 2017, from https://www.britannica.com/science/polyp-zoology The Editors of Encyclopædia Britannica. (2016, April 15). Bioluminescence. Retrieved October 30, 2017, from https://www.britannica.com/science/bioluminescence Sea pen. (n.d.). Retrieved October 30, 2017, from https://www.montereybayaquarium.org/animal-guide/invertebrates/sea-pen (n.d.). Retrieved October 30, 2017, from http://www.mesa.edu.au/cnidaria/cnidaria01a.asp
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Biology of the Sea
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