Life cycle of the white spotted sea jelly

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.

gamete

Stage 2: Planula

When these eggs are fertilised by sperms, the products are called planula.

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).
polyp

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).
strobilating polyp

Stage 5: Ephyra

Two weeks later, the strobilating polyp detaches itself from the polyp. It becomes a free-swimming ephyra.
Ephyra

Its stalk (oral arms) elongates gradually.
Ephyra

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.
young medusa

Lower tentacles form around the 6th week.
Medusa

White spots start to appear around the circumference of the bell, indicating that it will reach adulthood soon.
Medusa

Stage 7: Adult Medusa

In the next 2-3 months, its blue stripes gradually darken as it matures into an adult sea jelly.
white spotted 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.

white spotted sea jellies life cycle
White Spotted Sea Jellies, from gamete to adult.

If you wish to get behind the scenes of our sea jelly habitats, view sea jellies in their various life stages, and watch how sea jelly aquarists take care of these beautiful creatures, sign up for our VIP guided tour.

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