The species Chrysaora fuscescens is a jellyfish belonging to the class Scyphozoa. Its name comes from Greek mythology, where Chrysaor was the son of Poseidon and Medusa, whose name means ‘he who has a golden armament‘. On the other hand, the term fuscescens means ‘dark towards the light‘, alluding to the amber color of its bell, which becomes more reddish towards the edge.
Chrysaora fuscescens can be found in the shallow bays and harbors of the eastern Pacific Ocean, from Canada to Mexico. It has a preference for cold, shallow, nutrient-rich waters, and its peak density coincides with the end of summer.
The body of Chrysaora fuscescens, like that of most jellyfishes, has a bell. This species can reach up to 60 cm in diameter. The bell is yellowish or reddish/brownish in color, with the color getting darker as we move towards the outermost part. At the edge of the bell, we will find 24 thin, slightly flattened and elongated (1 meter) dark reddish tentacles. In the central part of the bell, and on the inside, 4 arms decorated with whitish spirals emerge from the center. These buccal arms are longer than the tentacles on the edge of the bell, and can reach lengths of up to 3.5-4.5 meters. Therefore, these are specimens of considerable size, which can even reach up to 25 kg in weight.
If we have the opportunity to see a specimen of Chrysaora fuscescens, taking all possible precautions so that its tentacles do not sting us, it is worth observing the tentacles and especially the beginning of the buccal arms, since it is common to find juvenile specimens of crabs of the genus Cancer. These crabs establish a symbiotic relationship by which they obtain a formidable protection, and in return they deworm the jellyfish.
This is a species with a carnivorous diet, which captures a wide variety of zooplankton, crustaceans, salps, pelagic snails, small fish and their eggs and larvae, and other jellyfishes. It uses specialized cells, called cnidocytes, present in its tentacles to capture and immobilize its prey. Lacking a great capacity for voluntary directional movement, Chrysaora fuscescens depends on extending its tentacles in the water and waiting for prey to make contact with them. Once captured, the tentacles fold to bring the food into the mouth cavity. And in the opposite direction, among the species that feed on Chrysaora fuscescens, we find several species of sea turtles, the sunfish (Mola mola) and the northern fulmar seabird (Fulmarus gaciatis).
The sting of humans by Chrysaora fuscescens, although not necessarily fatal and similar in intensity to the pain caused by a bee sting, can have serious effects in people sensitive to its toxin.
The reproduction of this jellyfish is complex and involves an alternation of generations between a sexual form (jellyfish) and an asexual form (polyp). Adult jellyfish release gametes into the water, where fertilization occurs. The zygote develops into a larva called a planula, which attaches to the substrate and forms a polyp. The polyp reproduces asexually by gemmation or strobilation, giving rise to small jellyfish called ephirae, which grow into adult jellyfish.
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