Jellyfish…. When we think of heritage, it is very unlikely that we would think of jellyfish, but guess what? Just like the leopard, the protea and the African penguin forms part of South Africa’s natural heritage, so do our endemic and unique jellyfish. So much so, that we have something called SA Jelly Lab were researchers and scientists spend their time investigating, researching and recording the jellyfish of South Africa.
Who is SA Jelly Lab?
The University of the Western Cape has been conducting jellyfish research for over 15 years. The SA Jelly Lab consists of a group of scientists from the University who specialise in all things jellyfish, has expertise in a range of fields and who conducts research across the oceans of the world.
What interesting research is happening?
One of the many projects this group is involved with is investigating the occurrences of jellyfish blooms within several estuaries along the south and east coast of South Africa. There have been sightings of jellyfish within estuaries stretching from the Breede River all the way to Kosi Bay. The presence of a few new species of jellyfish, belonging to the genus Crambione, is currently under investigation. These jellyfish inhabit the waters far up the estuaries where the salinity is low. So far, Crambione has been collected in the Breede -, Keurbooms -, Kromme -, Mgwalana - and Kwellera Rivers, but could possibly occur in even more.
It was originally thought that the jellies within these estuaries belonged to one species and consisted of different populations, but genetic results suggest that each is a new species. At the moment, SA Jelly Lab is paying special attention to describing each species, looking into their distributions, as well as the variations between the different species - from a morphological to a genetic level.
About these jellies
Crambione is a barrel-shaped jellyfish that is mostly reddish-brown in colour. That said, its colour may vary depending on its environment. These jellies lack tentacles but have large “frilly” oral arms used for feeding and deterring predators. Their sting isn’t painful, and at worst might just leave an itching sensation. Jellies of this genus are edible. Crambione mastigophora is known to be of socio-economic value and is fished for human consumption in certain parts of the world. One of the new species Crambione azanii sp. nov. is exhibited at the Two Oceans Aquarium (although we still refer to is as Catostylus azanii here as the evidence supporting its new classification is very recent).
Significance of different populations/species in different estuaries
Estuaries differ in their biochemical properties (temperature, salinity, pH, chlorophyll-a, etc.) as well as the types of zooplankton (on which jellies mostly feed) found in them. This, in turn, promotes the occurrence of different jelly species, or enable species to evolve and adapt to that specific environment. It is understood that the Crambione species are secluded within their respective estuaries. They do not inhabit the adjacent bays and aren’t able to migrate between estuaries. In the past, these jellies must have entered each estuary and adapted to survive in that specific environment, with being cut off from the other populations resulting in speciation.
An interesting survival strategy of these organisms is its ability to develop specific types of stinging cells, which allows them to adapt to the food web of the environment. They use their stinging cells for feeding as well as deterring predators. Each population of a jellyfish's stinging cell complement is unique, and research suggests that the different species amongst the different estuaries can be distinguished by using their stinging cell complement alone. This is almost like a species-specific fingerprint.
These jellyfish do not occur year-round and only bloom when environmental conditions are favourable. These conditions and their ecological importance are still under investigation. When these blooms do occur, researchers immediately set out to collect specimens for analysis. These species are easily accessible by boat.
Collection is very simple: the boat approaches a specimen which is then caught using a relatively large net attached to a long pole (dip-net or swimming pool net). The jellies have evolved to survive - releasing thousands of eggs and sperm when they feel threatened which creates a thick, sticky jelly-like goo in the water. For an organism which lacks a brain, these jellies are quite intelligent, sensing activity in the water and diving deeper into the water column when they feel threatened. This makes collecting these jellies tricky and forces researchers to sneak up on them. The most effective methods have proven to be building up speed, then lifting the boat engines to reduce the noise and water displacement, allowing the boat to silently float over the jellyfish, or to remain stationary with the engines off and wait for the jellies to pass under the boat. One still needs to be quick, otherwise, they dive down. The elusiveness of the jellies has a way of turning collection trips into a bit of a competition between the scientists, seeing who can collect the most.
Collected individuals are numbered and corresponding genetic samples are taken from the oral arms and gonads of each individual. Thereafter, whole specimens are fixed in formaldehyde. The location of the collection is recorded, as well as the environmental parameters of the sampling location. If live specimens are needed for ecological research, they are either transported in a fibreglass aquarium on a trailer, or in buckets, with water changes every few hours.
Back in the lab
Once back in the lab, a set number of individual jellies is selected for study. Researchers assess their morphology by measuring various distinguishing structures which helps with the classification of the jellyfish. Genetic samples are also analysed and assessed to determine whether there are any genetic differences between the various populations along the coastline as well as to described species within the genus. This is a tedious process which takes some time.
When is it is a new species of jellyfish?
In the last 100 years, purely anatomical features were used to distinguish and identify different types of jellyfish. With the advent of DNA technology, more attention has recently been given to their genetic structure. This allows scientists to be more accurate when describing species. Very recently, another important characteristic which came to light, is the description and comparison of a jellyfish’s specific compliment of stinging cells, paying particular attention to the size, types and relative abundances thereof.
When researchers encounter an unknown jellyfish, it is important to first determine whether it perhaps fits the description of an already described species. This entails describing the genetic and morphological properties of the jelly and comparing it to what has already been published. Essentially, through a process of elimination, these jellyfish are classified either as an already described species or a new one.
Follow SA Jelly Lab
Want to stay up to date with the latest in South African jellyfish research? Feel free to follow SA Jelly Lab on Instagram @jellylab_sa or get in touch via email for any queries, reports on jellyfish activity or wanting to collaborate if you are interested in contributing to our research.