Photo By: Brian Bollig


Form and Function

        The Hawaiian Box Jellyfish (Carybdea alata) is a highly adapted species of jellyfish found in the marine habitat of the Pacific, Indian, and Atlantic Oceans (Nagai et al. 2000). The adult Hawaiian Box Jellyfish has a transparent bell which is about 50 mm wide, 50 mm in depth, and has and average height of 80 mm (Yanagihara et al. 2001). In order to capture their food Hawaiian Box Jellyfish have four thin pinkish tentacles expanding from the corners of their precisely square bells (Nomura et al. 2002) that contain nematocysts found on the exumbrellar surface  (Yanagihara et al. 2001).  An individual Nematocyst contains a rigid venomous capsule and an extremely coiled eversible tubule which is used to capture its prey (Yanagihara et al. 2001). The discharge of the venom from the Nematocyst occurs extremely fast at an average rate of three micro seconds, piercing its preys, causing paralysis.  The venom of Hawaiian Box Jellyfish contains bioactive proteins that cause potent hemolytic activity (the rupturing of red blood cells) in many of its prey (Nagai et al. 2000), which along with the unique structural properties of the nematocyst tubule contributes to this species predatory success (Yanagihara, et al 2001).  Photo by: David Doubilet

            The Hawaiian Box Jellyfish belongs to the class Cubozoa which unlike other jellyfish have image forming eyes that are advantageous in dark waters (Coates 2002). This is because they are known to help  capture and focus light. These eyes are located on the rhopalia, which are small sensory structures. Each rhopalium contains a large complex eye and a small complex eye which make up its camera-type eyes. Each rhopalium also has an identical set of pit eyes and an identical set of slit eyes which are its ocelli. In order to see, each type of eyes contains ciliated photoreceptors. A jellyfish medusa has a total of twenty-four eyes because there are four rhopalia and six eyes per rhopalium (Coates 2002). Hawaiian Box Jellyfish, like most Cubozoans, prefer near shore environments and near the bottom environments during the day. This is due to the low frequency visual information, which is suitable for their light mediated eyes.

            As a Cubozoan, the Hawaiian Box Jellyfish have radial symmetry and a nervous system that is located around the margin of its bell. Both of these characteristics allow the Hawaiian Box Jellyfish to detect information from all around (Coates 2002). This information not only helps the Hawaiian Box Jellyfish detect prey and predators, but also helps execute their locomotion. The rhopalial ganglia contain the swim pace makers which use the nerve ring to communicate with each other. This stimulates the swim musculature producing locomotion. Since Hawaiian Box Jellyfish live in marine environments their locomotion is affected by the flow of the water so their sensory system is important (Coates 2002). Ultimately, without the rhopalia it would be sessile. The Hawaiian Box Jellyfish has a well-adapted form and function in order to sustain life in its tropical marine habitat.

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