Jobs at S.E.A. Aquarium: Sea jelly aquarist

With more than 13,000 employees, Resorts World Sentosa sports a range of jobs that are almost as diverse as the fishes you’ll find at its S.E.A. Aquarium.

To help unravel the mystery of what goes into running a holiday destination that has (almost) everything you’d want while on a holiday, here’s the Career Spotlight series.

This month, we’re highlighting the Aquarists at S.E.A. Aquarium, specifically the team that is in charge of taking care of the sea jellies.

Imagine having hundreds of offspring that you need to care for every day. For our sea jelly aquarists, that’s all part of an ordinary day at work.

Sea jelly aquarists Henry (left) and Joshua (right)
Sea jelly aquarists Henry (left) and Joshua (right)

Led by curator Aaron Brett, the sea jelly team currently consists of Henry Siluvai Dhason, Joshua Huang and Kok Khew Wai who are in charge of the sea jelly exhibits and breeding programme at S.E.A. Aquarium.

Breeding sea jellies at S.E.A. Aquarium

Before we dive into the duties of the team, take a look at the life cycle of sea jellies:

Life stage of sea jelly

Like humans, most species of sea jelly are either male or female. When sea jellies reach maturity, they start to reproduce sexually and release sperm and eggs into the water. Once the eggs are fertilised, a small larva develops, which eventually settles on a hard surface and grows to form a small polyp.

By placing an acrylic plate in the habitat for these polyps to settle, the aquarists can easily move these plates to the hatchery and begin the next part of the process.

Acrylic plates where sea jelly polyps settle.
Acrylic plates where sea jelly polyps settle.

This is where their fascinating life cycle gets more complex as the polyps can multiply by reproducing asexually. Resembling a stack of dinner plates, the polyps can release tiny sea jellies (ephyrae) in a process known as strobilation. To encourage the strobilation process, in moon sea jellies for example, the aquarists will reduce the water temperature.

The sea jelly aquarists collect the euphyrae and move them into a separate tank. As they grow, the sea jellies are moved into large round tanks called kreisels, where the water flow keeps them from settling on the bottom.

Juvenile Japanese sea nettles (Chrysaora pacifica) in their kriesel tanks.
Juvenile Japanese sea nettles (Chrysaora pacifica) in their kriesel tanks.

Since the start of the sea jellies breeding programme at S.E.A. Aquarium in early 2013, the team has successfully bred several species so far:

  • Moon sea jellies (Aurelia aurita)
  • Upside-down sea jellies (Cassiopea andromeda)the ca
  • Japanese sea nettles (Chrysaora pacifica)
  • White spotted sea jellies (Mastigias papua)

A day in the life of a sea jelly aquarist: Harvesting food

Henry harvests brine shrimps which are used as sea jellies feed.
Henry harvests brine shrimps which are used as sea jellies feed.

So we know about the life of the sea jellies, but what about that of the aquarists?

In a typical day, the sea jelly aquarists start by harvesting brine shrimps (also known as artemia or sea monkies) to use as live feed for the sea jellies. The S.E.A. Aquarium produces large quantities of brine shrimp every day in specialised hatching cones which are filled with water and pumped with air.

To collect the brine shrimps the aquarists need them to settle towards the bottom of the hatching cones. Brine shrimp usually swim at the top of the cone towards the light. When the aquarists cover the bucket and switch off the water flow, the brine shrimps stop swimming and settle at the bottom.

Next, they will then open a tap at the base of the hatching cones and collect the brine shrimp which are used to feed sea jellies in the aquarium’s exhibits as well as those growing in the hatchery.

A day in the life of a sea jelly aquarist: Cleaning the exhibits

The aquarists then spend time siphoning out leftover food and waste at the sea jellies exhibits (the ones guests see), to keep the water clean and in good quality.

It’s then back to the hatchery, where they clean the tanks which require them to carefully remove the polyps and ephryae and temporarily relocate them into a separate tank. The polyps attached to the acrylic plates can simply be lifted out of the water.

Relocating the polyps attached to acrylic plates so the tank can be cleaned.
Relocating the polyps attached to acrylic plates so the tank can be cleaned.

Removing any remaining polpys that haven’t settled on the plates and the tiny floating ephryae is more time consuming. The aquarists have to carefully scoop out the water into a container and extract the tiny animals using a pipette.

Only when all the polyps and euphyrae have been moved, can the aquarists start cleaning the original tank.

Polyps and ephyrae being carefully relocated using a pipette.
Polyps and ephyrae being carefully relocated using a pipette.

A day in the life of a sea jelly aquarist: Feeding sea jellies

After cleaning the tanks the sea jellies are then fed using different methods depending on the species.

Broadcast feeding

Broadcast feeding involves pouring food into the water which allows it to disperse.
Joshua demonstrates broadcast feeding involves pouring food into the water which allows it to disperse.

Sea jellies such as the Moon sea jellies and White spotted sea jellies are fed by broadcast feeding. The food is carefully poured into the water and gets distributed to the sea jellies inhabiting it due to the water flow.

The moon sea jelly is translucent and can appear to change colour when feeding.
The moon sea jelly is translucent and can appear to change colour when feeding.

Moon sea jellies catch food using stinging cells on their tentacles. These tentacles have rows of cilia which beat to create currents that flow towards the mouth.

As Moon sea jellies are translucent, they often change colour depending on their diet. An orange tint suggests that the sea jellies have been fed on brine shrimp.

Target feeding

Japanese sea nettle being fed using the target feeding technique.
Japanese sea nettle being fed using the target feeding technique.

Japanese sea nettles, on the other hand, require target feeding.

The aquarist will feed each individual sea nettle by drawing in a mixture of seafood using a pipette (sometimes a large turkey baster) and squeezing the food directly into the bell of the sea jellies. Once fed, the sea nettles will retract its tentacles towards its mouth.

A Japanese sea nettle retracting its tentacles after being fed.
A Japanese sea nettle retracting its tentacles after being fed.

Understanding the various life cycles and feeding preferences of the sea jellies allows the aquarists to vary their methods and take the best care of these animals. Joshua Huang said that being a sea jelly aquarist is a rewarding role as they are able to see the full life cycle of the sea jellies from polyp to ephyra to adult (medusa) phase.

All four successfully bred species of sea jellies can be seen at S.E.A. Aquarium: the Moon sea jellies, Upside-down jellies, Japanese sea nettles and White spotted lagoon sea jellies.

From now until 31 May, the aquarists have relocated parts of the hatchery into the S.E.A. Aquarium’s front of house. Come on down to see the sea jelly in their polyps and ephyrae phases.

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