Moon Jellyfish

By: Hannah Wilz

Kingdom: Animalia

Phylum: Cnidaria

Class: Scyphozoa

Order: Semaeostomeae

Family: Ulmaridae

Genus: Aurelia

Species: A. Aurita

Morphology:

Commonly known as the Moon Jelly or A. Aurita. They are one of the most common jellyfish species and they display radical symmetry. Moon Jellyfish have transparent bells with a diameter that ranges from 10 to 35 cm. Their gonads are horseshoe shaped and are typically a bright blue or pink. The small tentacles, usually 1 to 5 cm, radiate from the bell. Four oral arms radiate from below the bell. These arms contain stinging cells, called nematocysts, that aid the jellyfish with capturing prey and in the feeding process.

Swimming and Toxicity:

Swimming is dependent on thrust generating in the bell of the medusa. Their tentacles are extended while swimming in order to capture prey more efficiently. The continuous swimming motions are divided into two essential phases, the power strokes and the recovery strokes. The durations of the strokes were proven to be different, the power strokes are shorter than the recovery strokes.

In the power strokes, the contractions of the circular muscles reduced the diameter of the bell cavity. Then when the pressure is built up, the contractions force water out of the bell cavity posteriorly. This motion causes the Moon Jelly to thrust forward at the maximum velocity.

The recovery stroke begins once the circular muscles have relaxed, causing the bell diameter to increase. The bell cavity regains the same volume that was previously expelled.

The nematocysts have a high toxicity, are harmful, and can be lethal to other marine species. Their toxicity to humans is considered as relatively harmless.

Diet:

Aurelia Aurita are carnivorous. Their prey must be small enough to get entangled in their tentacles, so they primarily feed on zooplankton, mollusk larvae, and fish larvae. They have no clear pattern of prey selection and feed unselectively on a wide range of zooplankton. The Moon Jelly captures their prey by stinging them through the nematocysts found at the ends of their tentacles. Once captured, they move their prey towards their stomachs using the oral arms. Their stomachs are located under their bells. Few prey are captured during the initial power stroke, but the majority of observed prey capture occurred during the recovery stroke.

Habitat:

Found predominately in costal bays or estuaries, partially enclosed costal bodies of water where saltwater and freshwater is combined. A. Aurita are found globally and tend to prefer warm environments near the coasts of the Atlantic, Pacific, and Indian ocean. The moon jelly in the medusa stage is generally found in shallow, partially enclosed systems with limited tidal exchange. Water that ranges from 8 to 19 degrees celsius is the most preferred temperature for Moon Jellyfish.

Life Cycle:

The moon Jelly reproduces sexually in the medusa stage and asexually in the polyp stage. During embryogenesis the Planula (larvae) emerges then metamorphosing into a mature sessile polyp. The polyp is the most stable form in the life cycle. It reproduces asexually through budding in order to produce large polyps that will eventually develop into medusa. This development occurs through strobilation, where the polyp is divided from the oral to the abdominal end in segmented discs. Each segmented disc develops into an Ephyra, which is an independent, motile, complete young medusa. The free swimming ephyra then grows into a mature medusa that is able to reproduce sexually.

References:

Brekhman, Vera, Assaf Malik, Brian Haas, Noa Sher, and Tamar Lotan. "Transcriptome Profiling of the Dynamic Life Cycle of the Scypohozoan Jellyfish Aurelia Aurita." BMC Genomics 16.1 (2015): 74. Web.

Costello, J. H, and S. P Colin. "Morphology, Fluid Motion and Predation by the Scyphomedusa Aurelia Aurita." Marine Biology 121.2 (1994): 327-34. Web.

Goldstein, Josephine, Ulrich K Steiner, and Anna Kuparinen. "Ecological Drivers of Jellyfish Blooms – The Complex Life History of a ‘well‐known’ Medusa (Aurelia Aurita)." The Journal of Animal Ecology 89.3 (2020): 910-20. Web.

Helmholz, Heike, Blair D Johnston, Christiane Ruhnau, and Andreas Prange. "Gill Cell Toxicity of Northern Boreal Scyphomedusae Cyanea capillata and Aurelia aurita Measured by an in Vitro Cell Assay." Hydrobiologia 645.1 (2010): 223-34. Web.

Lucas, Cathy H. "Reproduction and Life History Strategies of the Common Jellyfish, Aurelia Aurita, in Relation to Its Ambient Environment." Hydrobiologia 451.1 (2001): 229-46. Web.

Tombs, R. (n.d.). Aurelia Aurita (moon jellyfish). Animal Diversity Web. https://animaldiversity.org/accounts/Aurelia_aurita/#food_habits.

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