The following series of slides demonstrate the life
cycle of Aurelia from the formation of a free swimming planula larva to
a free swimming adult. The adult produces eggs and sperm which unite
to give rise to the following life cycle: Zygote -->Planula-->scyphistoma-->Strobila-->Ephyra-->Medusa
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1. Planula
After the adult releases gametes into the seawater, development leads to a swimming stage known as the planula. The planula larva is a stereo-gastrula with a ciliated ectoderm. After swimming about for a short time as a merolankton, it will attach to a suitable subtrate. it develops into a polypoid larva, the scyphistoma. |
| 2. Scyphistoma
The first sessile stage in the life cycle of Aurelia is the polyp-like
form called the scyphistoma. This stage is attached to a hard substrate,
often in low light. After feeding, it will undergo budding at the
oral end and develop into a strobila.
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3. Strobila
This is a modified scyphistoma in that the budding will occur a the oral end. Each bud becomes an ephyra. After budding is complete, it is possible for the strobila to revert to the scyphistoma stage. |
| 4. Ephyra
Within a short time, the young ephyra is feeding in other micro-planktonic
crustacea and larvae. It captures the prey on the lappets and moves
the food towards the mouth. This stage has begun to differentiate
oral arms and marginal tentacles.
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5. Aurelia Medusa
It is extremely common in the ocean from NJ north. They may get as large as 12'' across; fortunately they do not sting (except for a mild irritation). The gastric pouches have become modified into a system of canals. Aurelia actually feeds on suspended mater which sticks to the lower surface of the bell. The oral arms then carry this material to the mouth See Brusca p. 229 (fig. 14) |
| A. Mouth,B. Gonad, C. Manubrium (oral arm), D gastric pouch, E. Radial canals, F. Rhopalium |
