Why can Jellyfish Spread so Easily?

Why Can Jellyfish Spread so Easily?

The answer lies in the fact that jellyfish are nearly indestructible and have survived for millions of years. they are adapted and evolved to do nothing other than survive and breed.

Jellyfish feed on almost every other marine animal that will fit into it's mouth and in some cases, even larger. This simple fact alone, that jellyfish are predators to many, combined with the fact that few other marine animals are predators to the jellyfish, allow them to drift into unknown waters without fear of predators but with the promise of food. These are two essential ingredients when it comes to survival and the Jellyfish has both.

When a jellyfish catches it's prey, it's tentacles inject a poison into the flesh of the victim paralysing it, killing it or annoying it, depending on the size of the creature. not only does this poison only kill prey small enough to eat, but it discourages any predator that fancies a taste of the odd- looking fish drifting by. The toxin injected by the jellyfish that do so can be detected by humans and can even be fatal. The jellyfish's defence mechanism is the same mechanism it uses to catch food and so it does not need a complex set of organs or even a brain to survive, it simply drifts. In fact, it's mechanism is so good, that even humans, land mammals much larger and capable of thinking ways around the problem, still vacate the water when a jellyfish is spotted.

The spread of jellyfish is inevitable as there are little predators and a fear factor associated with them. We have little defence and their rapid spread over the last few years has started to have knock on effects for humans on land... here is a short video giving a visual of a jellyfish and its efficiency when it comes to feeding. ( https://www.youtube.com/watch?v=BF6lNP0Uiss )

The next video shown is an information video describing the spreading of jellyfish and the areas affected. ( https://www.youtube.com/watch?v=kJEYuaMTolo )

Jellyfish Species and Locations

Jellyfish species and Locations

As I live in a European country, I will outline mainly the European species and will show images, whether or not they swarm and relative dangerousness to humans.

The general theme of the following jellyfish is a preference to warmer European countries and the ones I have selected I have done so due to reports of swarms from that species. ( http://www.perseus-net.eu/en/species_of_jellyfish/index.html )

Cotylorhiza Tuberculata:

These large jellyfish are being reported in abundance on the Italian coast and especially in bays, the reports have dies down in the past year but the alert is still high. These jellyfish are harmless to humans and swarm at the end of the summer months. 

 

 Aequorea forskalea:

These are generally quite small jellyfish and are rarely found in large numbers along coastlines in mainland Europe. However, off the coast, enormous swarms have been reported and the swarms contained many larger specimens. Their sting is harmless as their poison is far to weak to have an effect.

 

 

Aurelia aurita:

These jellyfish are about the size of an average male adult's hand and pose no threat when it comes to stinging. This seemingly harmless jellyfish is known to swarm regularly and can cause havoc on almost every European beach there is. the swarms are usually big and this species can be found in abundance all year long.

 

Chrysaora hysoscella:

This is one of the rare species of jellyfish that can thrive and not just survive in both cold and warm waters. Often found in abundance, this swarming jellyfish can be found as far North as the Norwegian Fjords. Their sting is nothing more than a nuisance and can be compared to a nettle sting at most.

 

Rhizostoma pulmo:

Usually found in huge abundance, these jellyfish offer a place of refuge for microorganisms and small fish who hide in the jellyfish's oral arms. The swarms are mostly found in warmer waters and are generally harmless to humans.

The species that I have listed are all found in the main European Sea's such as the Mediterranean, Adriatic and North Seas. They are also among the many other species that contribute to the global increase in swarms of jellyfish. These swarms are occurring all over the world and if it continues, the natural ecosystem won't be able to sustain the number of jellyfish being produced. This is, as I have said, partly due to climate change and the increase of global temperature. If this continues at it's current rate, soon, we will have a serious problem, but is it too late?

The Reproduction of Jellyfish

 The Reproduction of Jellyfish

Jellyfish reproduction involves several different stages of development and growth. As an adult jellyfish (the medusa stage), sexual reproduction is possible. Respectively, there both male and female jellyfish who produce sperm and eggs. For the sexual reproduction to occur, both the sperm and the eggs are released into the water and join to form a Panula. The Planula is the larval form the jellyfish takes, it drifts through the sea until it latches on to a smooth rock or other surface where it remains until it develops into a Polyp. The Polyp stage can last for many months and it is in this stage where asexual reproduction occurs. The Polyp clones itself and produces many other identical 'baby jellyfish'. These clones stick to each other in a fashion that resembles a piece of seaweed or coral. This stack of clones then develops further into Ephyra's, each layer or each clone turns into one Ephyra from which they drift using currents and feed on plankton and other small fish. Over time, the Ephyra develops into the Medusa stage from which the process starts again.

http://themoonjellyfish.weebly.com/life-cycle.html


Jellyfish reproduce for the same reasons all species on Earth reproduce, to ensure the survival of the gene line and the species as a whole. Considering that Jellyfish seem to survive and thrive in warmer waters with high salt and iodine content, it has lead scientists to believe that with increasing temperatures due to Climate Change, and particular heat in these oceanic areas, jellyfish are perceiving this as a constant Spring and so are consistently reproducing time and time again in a single year.

This explains the Large Blooms in the Chinese area but we still do not know where certain species are, and so in my next post, this is what I will be outlining.

Why are Jellyfish spreading?

Why are Jellyfish Spreading

Unusually, Jellyfish are found all over the globe. Although their numbers vary in different seas and oceans, the fact is that gelatinous creatures have survived in every environment all over the world for as many as 600 million years. The graph shown below displays the spread of jellyfish life in the global oceans and continents. So why are there more jellyfish in China than there are in Indonesia?

Epipelagic

The real problem lies actually off the coast of Japan, the graph has the area down as China as it is the largest commonly known country in the region. In Japan, the jellyfish have swarmed and produced hundreds of thousands of young in what seems to be either a long dormant cycle or a freak swarm which has taken over the ocean. So what causes these blooms?

Well, jellyfish, although able to self-propel using their bell shaped top, they are almost always reliant on ocean winds and currents to move. 'Blooms' can occur when ocean winds collide driving large numbers of jellyfish on to one single coastline, making it appear that there are many more being born than usual.

A true bloom however is when jellyfish mate and produce an abnormally large number of young in one season, temperature plays a bug part in the mating and breeding of jellyfish. For instance jellyfish tend do live longer in warmer waters and the hotter the day, the more water is evaporated leaving salt behind, this in turn increases the salt content in water and so the extra iodine present helps polyps (young jellyfish) develop into adults. This temperature is rising with continuous relation to climate change and so jellyfish will continue to produce at the current rate.

So why China?

Well it is purely geographic. To begin with, the oceanic area around Chins is prone to jellyfish blooms even before all of this climate change acceleration. This is due to the relative warmth of the Southern China and Japanese ocean area. These warm waters result in high jellyfish population.

https://opentextbc.ca/geology/wp-content/uploads/sites/110/2015/08/global-distribution-of-average-annual-sea-surface-temperatures.png

The image shown is an example of a relatively small sized jellyfish paired with thousands more in a large bloom
In this post I have briefly described the growth of jellyfish and the reasons for large numbers of blooms in recent years, in the next post I will outline the reproduction of jellyfish.

What Exactly is a Jellyfish?

What exactly is a jellyfish?

A jellyfish is a 'free-swimming marine coelenterate that is the sexually reproducing form of a hydrozoan or scyphozoan and has a nearly transparent saucer-shaped body and extensible marginal tentacles studded with stinging cells' (http://www.merriam-webster.com/dictionary/jellyfish). This definition is very complicated and has many unusual words in it, a shorter definition by the same site is 'a sea animal that has a very soft body and that can sting'. Of course, put anything in such simple terms and it loses a lot of its value so in this post I will explain what a jellyfish is.

So what is a jellyfish REALLY?

Well, jellyfish are a complicated structure of organs just like other multi-cellular organisms. I have provided a cross-section to demonstrate its complexity and will briefly describe their evolution and dip slightly into their anatomy

http://www.pic2fly.com/Jellyfish+Body+Parts+Diagram.html

Evolution and Anatomy

It is estimated that jellyfish have been on the earth for more than 500 million years. This figure comes from an exiting discovery made in 2007.

In 2007, scientists discovered a 500 million year old jellyfish fossil and were able to use it to compare our modern day jellyfish to their ancient ancestors. Upon comparison, the fossil showed a typical bell shape and tentacles much like the species swimming around today. However upon closer inspection a shocking discovery was made. It turned out that either the complexity of modern jellyfish developed rapidly about 500 million years ago, or that jellyfish are even older and developed long before that time. This suggests that jellyfish could be close to even 600 million years old. That is quite a feat and they achieved it using their simple anatomic structure. (source: http://www.livescience.com/1971-oldest-jellyfish-fossils.html)

Anatomy

As shown in the diagram above, jellyfish have simple but effective cellular structures. I will explain the terms used in the cross section to further better your knowledge of the anatomy.

Mesenchyma

Now although it's name suggests something quite important and complicated, the mesenchyma is nothing more than a cellular structure that is transparent in most cases but sometimes has pigment to cause colour. This cellular structure is like a firm gel that formats the main body of the jellyfish's bell (body)

Gastrovascular Cavity/Gastrodermis/Gastric Filaments

The Gastrevascular Cavity is a large chamber in which food is digested. It can split into many canals and is commonly known as a 'blind gut' as food enters through the same place that the waste leaves.

 

the Gastrodermis is quite simply the layer of cells that act as the lining of the Gastrovascular Cavity.

 

Gastric Filaments are used to stun and kill living animals that are taken into the Gastrovascular cavity as food.

Gonads

To put it briefly, Gonads are a jellyfish's sex organs.

 

Next post:

Where to find jellyfish and why they found there...

Introduction

The Geography of Jellyfish

Introduction

Hi, my name is Matthew and this is my blog on the geography of jellyfish. In the eyes of most people, jellyfish are nothing more than cool-looking gelatinous blobs in the water that cause nothing but pain. In this blog I aim to prove and inform you all that while still causing pain, jellyfish are among the most perfectly evolved creatures on our planet. they can survive almost anywhere and can eat almost any living thing making the indestructible, fast multiplying, prehistoric organisms that are still feared by even the top of the food chain, us.