White Spotted Sea Jelly (Mastigias papua) is one of the most successfully bred species of sea jellies at S.E.A. Aquarium. These vertebrates (animals without a backbone) have a complex life cycle, and exist largely in two physical forms – Polyp and Medusa.
Below, we take you through the hows and whens of this sea jelly’s life cycle.
Credits to aquarists Vivian Cavan, Joshua Gan, Jane Ong and Kenneth Chin for their work on this.
Life cycle: White Spotted Sea Jelly
Stage 1: Gametes
Eggs and sperms (the gametes) are released into the water by sexually mature adult White Spotted Sea Jellies.
Stage 2: Planula
When these eggs are fertilised by sperms, the products are called planula.
Stage 3: Polyp
When the free-swimming planula finds a suitable substrate (a surface that provides it nourishment), it attaches itself and grow into a polyp. The polyp will eventually form colonies through asexual reproduction (also called budding).
Stage 4: Strobilating Polyp
A small disc-shaped ephyra emerges from the polyp after about 1-2 weeks, depending on factors such as light, food intensity and temperature. The leftover polyp will continue grow and multiply (budding).
Stage 5: Ephyra
Two weeks later, the strobilating polyp detaches itself from the polyp. It becomes a free-swimming ephyra.
Its stalk (oral arms) elongates gradually.
Do you know? Unlike White Spotted Sea Jellies which produce one ephyra per polyp (also called monodisk), species like the Atlantic Sea Nettle or Chrysaora quinquecirrha (below) are polydisk and can produce at least 20 ephyras per polyp.
Stage 6: Young Medusa
After about 1-2 months (depending on individual’s rate of growth), the ephyra’s stalk splits into 4-8 tentacles. It is now a young medusa.
Lower tentacles form around the 6th week.
White spots start to appear around the circumference of the bell, indicating that it will reach adulthood soon.
Stage 7: Adult Medusa
In the next 2-3 months, its blue stripes gradually darken as it matures into an adult sea jelly.
It is now a full-grown adult, approximately 4-5 months after its ephyra stage.
Here’s the illustrated version hand-drawn by sea jelly aquarist Kenneth Chin.