Krish Lewis, from Paarl, is the new “jelly guy” at the Two Oceans Aquarium. He is in charge of the upcoming Jellies Exhibit. Not only is Krish ensuring the smooth running of the displays themselves, but he also uses his specialist knowledge to grow a variety of species from polyps to jellies-as-we-know-them.
Two Oceans Aquarium: How did you get to this place in time – and being the Aquarium’s jelly guy?
Krish Lewis: I’ve always loved animals! Growing up, I bred various types of birds and fish as a hobby. I eventually looked around for places where I could study and learn more about animals and the University of the Western Cape was it for me. There, I studied Marine Biology under Professor Mark Gibbons.
I researched a possible bio-control mechanism for malaria during my Honours year and, looking around for what to do next, I learned about the “jelly problem” that the Northern Benguela Current is facing. Following the collapse in fisheries due to overfishing in the late 1970s, the northern Benguela Current, which flows northward along the western coast of South Africa, has seen an exponential increase in jellies, especially of the Benguela compass jelly (Chrysaora fulgida) – my favourite.
Currently it is estimated that for every 1.8 million tons of finned fish, there are 12.8 million tons of jellies within that ecosystem! It's an ongoing problem.
Many other places around the world had or have the same problems with large, unexplained jelly swarms.
Back then, the group of people studying jellies globally was quite small, and even smaller in South Africa. Most people were trying to clear up the genetic confusion among the jellies along our coast. It was finally decided there are three species of compass jelly on the South African coast: Chrysaora fulgida, Chrysaora agullensis sp. nov. and Chrysaora africana.
But I was a bit more ambitious, and wanted to work with the polyps and the animals themselves. I started learning how to grow jellies from polyps (the sessile – or non-moving – stage of a jelly’s lifecycle) and getting them to reproduce new jellies.
We wanted to understand which environmental parameters allowed these animals to so efficiently fill the niche that the absence of the fish created.
TOA: Why was this important to understand?
KL: This was important because jelly swarms negatively affect many industries along our coast, such as mines, the Koeberg power station and aquaculture facilities. The jellies get stuck in cooling intake systems, or swarms kill off animals in fish-farming cages and taint the fish that are harvested along with the jellies, just to name a few problems.
To find out more, we studied the growth rates of the jellies, their polyps and what the potential triggers were for the polyps to bud off into jellies. We tried to understand how to grow polyps, and how long it takes for poylps to grow into adult jellies.
Working with the polyps and jellies I also had to learn a lot about water-quality parameters, because jellies require excellent water quality to thrive.
Many experiments, trial, and lots of error yielded results, and when this recipe for growing these jellies could be repeated we finally found success. Being able to finally grow such difficult animals into mini-jellies is overwhelmingly rewarding.
The Two Oceans Aquarium’s plans to open a new jelly exhibit and the job opportunity that came with that allowed all my experience to tie in really well!
TOA: How is jelly husbandry different from that for other animals?
KL: Every jelly species has its own set of husbandry techniques. And it’s great if someone has already pioneered the husbandry for a particular species, but there are always variations that come up in real-life scenarios.
What’s really rewarding, however, is figuring out the specific conditions for jellies to grow, especially if you are the first to work with that species … Although it can be a bit of a nightmare.
Some jellies prefer warm water, others cold water. Certain species need strong light as they have symbiotic algae. Others want a specific amount of salts in the water. Some are cannibals and need other jellies as a major part of their diet, just to name a few things. When some jellies are unhappy they invert, like an umbrella in the wind, which you sometimes cannot correct. Jellies are very delicate, but you must always be mindful of the tentacles of certain species as being stung is not the highlight of anyone’s day!
TOA: What’s the most gratifying part of your job?
KL: Seeing the animals grow from polyps to jellies, of course. Then seeing people become mesmerized by watching the jellies pulse and swim.
I love telling people that polyps are technically immortal because of their ability to clone themselves, and that they can go into a state of dormancy when they are not happy … And that jellies could potentially take over the ocean.
TOA: What does it take to run a jelly exhibit?
KL: Running the exhibit takes a lot of planning and preparation. Animals need to be grown out months in advance if they are going to be a decent size and look like a jelly!
Our jellies are housed and grown in cylinders or kriesels. A kriesel is a jelly tank shaped like a tumble dryer. It allows the jellies to float in the tank with a gentle current, and not left to lie pulsing on the floor. The flow of water must be just right, keeping animals suspended instead of being knocked around, sucked in or damaged by pumps and overflow screens.
The life support for the cylinders and the kriesels are broad to allow us to be prepared to keep many kinds of jellies. We have chillers to keep water temperatures cool and exact, heaters to heat water up, and pumps, filters and protein skimmers to remove excess uneaten food - especially after our jellies have eaten “krill shakes”.
The systems have to be bubble-free, as bubbles can get trapped in the jellies’ bells, which would keep them afloat and could be detrimental to the animals.
Light sources also have to be strong for animals that need light for their symbiotic algae to photosynthesise, which in turn generates energy for their host jelly.
TOA: What’s so special about the jellies found on the South African coast?
KL: Because our coastline is bathed by both cold and warm currents, it supports a very high diversity of plants and animals. When it comes jellies, it’s no different. Around 20 different morpho-species of scyphozoan jellies (true jellies) have been recorded along our coastline. This translates to about 10% of the global diversity for this group of jellies.
Comparatively, of the 1 000 currently known hydrozoan jellies (both mero- and holo-plantonic), 280 are known to be found in and around our waters!