3/28/2023 0 Comments Box jellyfishRegardless of the jellyfish's position, the lens of the upper eyes is always pointed upward for orientation and navigation. These more complex eyes, which can see images, are known as the upper-lens and lower-lens eyes. In each rhopalia, two eyes are pigmented light-sensitive pits, two others are light-sensitive slit eyes, and the other two are the most sophisticated. They also contain pacemakers that regulate the expansion and contraction of the bell, which controls the jellyfish's movement. These rhopalia are sensitive to light, odour, and orientation. There is one rhopalium for each of the four sides of the box jellyfish. Each cluster is referred to as a rhopalium (plural is rhopalia). They are grouped into four clusters of six eyes each. The box jellyfish has 24 eyes located in a circular band around the bottom edge of its bell. Once digested, waste product is ejected through its mouth. Once prey is presented to it through its velarium, the mouth expands downwards to reach and engulf the prey, pulling it back into the animal's stomach. The jellyfish's mouth and stomach are formed from the top of the inside of the bell. This membrane is called a velarium (In ancient Rome, a velarium covered the top of the Coliseum and was opened and closed to control the weather). The lower part of the bell rolls inward and joins a membrane with a central opening that can open and close - like the iris of an eye. In addition to these two cellular layers, their bodies have a contractile ring composed of cells that provide the contracting force that propels the jellyfish through water. Sandwiched between these two layers is a non-living mesoglea layer that gives shape and structure to the jellyfish's body. This bell-shaped body consists of two layers of tissue - the external ectoderm and the internal endoderm. The adult box jellyfish is composed of 96% water, around 20cm across, weighs 2 kilos, and has an almost transparent, pale blue, jelly-like, cube-shaped body called a bell.
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