Introduction
Kingdom: Animalia
Phylum: Cnidaria Class: Scyphozoa Order: Semaeostomeae Family: Pelagiidae Genus: Chrysaora Species: C. achlyos |
C. achylos is a rare jellyfish found off the eastern Pacific coastline. When they do appear along the coast, they bloom in huge numbers, which has been the case in 1989, 1999, and 2010[4]. They eat zooplankton and other jellyfish, and exploding populations of plankton may be the cause of the blooms[4]. While the venom from their nematocysts is fatal to mice, in humans stings are relatively mild, with hundreds of cases of stings happening during past bloomings. Symptoms disappear in less than an hour[3]. They are particularly found around northwest Mexico and southwest California[2][3], but there have been sightings are far north as British Colombia.
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Anatomy
Jellyfish lack respiratory structures, and breathe by diffusion. They have a single orifice for feeding and excretion, the gastrovascular cavity[1]. Hanging down from the center is a thick, stiff stalk called the manubrium, which features a mouth at the tip and small projections that end in the jellyfish's four gonads[2].
C. achlyos have a distinct black-dark purple color pattern on the bell, which is hemispherical, smooth and fleshy, and up to 1 meter in diameter in live creatures (smaller in preserved specimens). Around the margins of the bell are 8 sensory lumps, which can detect light and gravity (each made of 2 rhopaliar cones)[2]. The nematocysts are present on the massive frillous spiraling oral arms (4), which may reach 6 meters long, and the long, delicate tentacles (24, white to light pink), which range from 1/2 to 1/4 the length of the arms[2]. |
Above: photograph clearly showing the color plan and the distinction between oral arms and tentacles
Left: jellyfish life cycle Reproduction
Like other jellyfish, C. achylos alternates body forms between generations, between a polyp and a medusa. The polyp asexually produces a jellyfish, which then sexually produce more polyps[4].
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References
[1]Campbell & Reece, Biology 8th Edition
[2]Martin, J. W., & Gershwin, L. (1997). Chrysaora achlyos, a remarkable new species of scyphozoan from the Eastern Pacific. Biological Bulletin, 193(1), 8.
[3]Radwan, F., Gershwin, L., & Burnett, J. (2000). Toxinological studies on the nematocyst venom of Chrysaora achlyos. Toxicon: Official Journal Of The International Society On Toxinology, 38(11), 1581-1591.
[4]http://interactive.sheddaquarium.org/2012/07/rare-black-sea-nettles.html
[2]Martin, J. W., & Gershwin, L. (1997). Chrysaora achlyos, a remarkable new species of scyphozoan from the Eastern Pacific. Biological Bulletin, 193(1), 8.
[3]Radwan, F., Gershwin, L., & Burnett, J. (2000). Toxinological studies on the nematocyst venom of Chrysaora achlyos. Toxicon: Official Journal Of The International Society On Toxinology, 38(11), 1581-1591.
[4]http://interactive.sheddaquarium.org/2012/07/rare-black-sea-nettles.html