A Sea of Frost Flowers

8 March 2016

Recently, Pixar released the exclusive trailer for the long-awaited movie sequel to Finding Nemo, Finding Dory, which has stirred much excitement and anticipation in the general public. Dory, the friendly-but-forgetful blue tang surgeonfish has played a significant part in the sequel. However, in the midst of all the fiction, imagination, and enjoyment of the movie that Dory illustrates, it is important to realize the meaning and significance behind the character’s portrayal. In order to gain a more comprehensive understanding of the intent that Dory’s character portrays, the science of the blue tang surgeonfish can be analyzed in terms of its behaviour, communication and perception, predation, and ecosystem importance.

The blue tang surgeonfish, also known as the Paracanthurus hepatus, is a member of the Acanthuridae family that lives on rocky coral reefs at depths ranging from two to forty meters, specifically in the Western Atlantic Ocean and the Caribbean Sea as shown in Figure 1 (Foster, 1985). They are diurnal omnivores that feed on both plankton and algae, yet they incidentally ingest a fair amount of inorganic material. Inorganic material, such as sand and seafloor mud, can occupy approximately 40% of their stomach volume (Morgan and Kramer, 2004).

Figure 1: Distribution of blue tang surgeon fish in the Western Atlantic Ocean and the Caribean Se highlighted in red (Hogan and McGinley, 2012).

Just like in the movie, Dory’s yellow and blue colour is a prominent feature that immediately captures the eye. Blue tang surgeonfish are able to communicate by changing their colouration (Anon, 2011). This colour change depends on the conditions of their surrounding environment and how they perceive it. Under stress or predation, their blue colouration deepens and other fish in the community can detect this colour change and infer potential problems.

This is also an adaptation that shows the maturity of a blue tang surgeonfish, as their colour changes as the fish matures. Young fish tend to be bright yellow with blue spots surrounding their eyes. As the fish matures, the majority of their body becomes blue with a bright yellow tail as shown in Figure 2 (Hogan and McGinley, 2012). To the full extent, adult blue tangs are covered with a rich blue colour from head to tail, with narrow dark lines running through the length of the body. This deeper blue colouration usually occurs in males to show dominance during breeding season (Hogan and McGinley, 2012).

In contrast with Dory, the fictional and friendly blue tang surgeonfish, the name “surgeonfish” originates from a particular physiology that all blue tangs possess – venomous razor sharp caudal spines and poisonous skin. These ‘swords’ are located at the base of their bodies just in front of their tail fin making them skilled to utilise this advantage in the face of a predator. With a quick twist of their tail these sharp razors become formidable weapons, which is the complete opposite behaviour and personality that Pixar’s Dory is portrayed as. Common predators of blue tangs include tuna, bar jacks, and tiger groupers (Morgan and Kramer, 2004). Along with this effective physical defense mechanism, blue tangs tend to congregate in schools. If a predator were to attack a school of surgeonfish, other surgeonfish would surround it, leaving the predator helpless (Foster, 1985). Strength does indeed come in numbers.

Figure 2: A juvenile blue tang surgeonfish that is bright yellow in colour as well as an adult blue tang with a deepened blue colour showing the change in colour as the species mature (Broy, 2009).

Intuitively, the habitat locations of blue tang surgeonfish is a direct connection to the movie, Finding Dory. Dory hopes to find her parents and family, yet she has been living in the southern part of the Indian Ocean where clownfish, like her friend Nemo, are the most prevalent species. Therefore, in order for Dory to find her family, she must journey and keep swimming across the oceans and continents towards the western part of the Atlantic Ocean where most of her species can be found. With the movie’s great suspense, it is important to keep in mind the significance and the reason for it all in order to gain the best experience possible. “Just keep swimming, Dory!”

References:

Anon, 2011. Paracanthurus hepatus. [online] Animal Diversity. Available at: <http://animaldiversity.org/accounts/Paracanthurus_hepatus/habitat> [Accessed 5 Mar. 2016].
Foster, S., 1985. Group foraging by a coral reef fish: a mechanism for gaining access to defended resources. Animal Behaviour, 33(3), pp.782-792.
Hogan, and McGinley, 2012. Blue Tang. [online] Eoearth.org. Available at: <http://www.eoearth.org/view/article/150704/> [Accessed 5 Mar. 2016].
Morgan, I. and Kramer, D., 2004. The social organization of adult blue tangs, Acanthurus coeruleus, on a fringing reef, Barbados, West Indies. Environmental Biology of Fishes, 71(3)

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