Black Sea Nettle Liam Koch Nichol


Scientists have created an organization system for all living organisms. These scientists are called "taxonomists" and the system is called "Taxonomy".


Black Sea Nettle is a common name for this species of jellyfish however it is scientifically know under the name of Chrysaora achlyos. This name was created using the organism's Genus and Species classifications. There are five other levels of Taxonomy in the list below that separate the Black Sea Nettle from nearly all other life on Earth.

Level of Taxonomy and Classification

  • Kingdom: Animalia
  • Phylum: Cnidaria
  • Class: Scyphozoa
  • Order: Semaeostomeae
  • Family: Pelagiidae
  • Genus: Chrysaora
  • Species: achlyos
|Top Left: Purple-Striped Jelly (Chrysaora colorata)| |Top Right: Pacific Sea Nettle (Chrysaora fuscescens)| |Bottom Left: Compass Jellyfish (Chrysaora hysoscella)| |Bottom Right: Mauve Stinger (Pelagia noctiluca)|

All of these species of jellyfish can be found in the same family as the Black Sea Nettle which is the third most specific taxonomic level. Since all of these jellyfish are closely related, they have many common characteristics.

These Characteristics Include:

  • These jellyfish do not have a ring canal, which is an anatomical feature near the center of the jellyfish that many other jellyfish have.
  • Their tentacles come from clefts or small indentations between lappets (sensory structure) on the outside edge of the jellyfish.
  • They have long oral arms that are pointed and folded and ruffled.
  • Jellyfish in this family also have a painful poisonous sting.
A phylogenetic tree for the Pelagiidae family.

Black Sea Nettle Diagram

A labelled diagram of the main anatomical features of a Black Sea Nettle jellyfish.


The evolution of jellyfish including the Black Sea Nettle remains mostly a mystery. This is because the soft tissue of jellyfish decomposes so quickly that remains are almost never captured by fossilization.

Extremely rare fossils of jellyfish.

These soft tissue fossils must undergo incredible circumstances to form. These jellyfish would have been compressed by very fine sediment to form fossils. Also, it would take great amounts of pressure and extremely fast compression to fossilize.

The oldest jellyfish fossils were dated to 500 million years ago. These fossils were remarkably similar to jellyfish today.

This implies that jellyfish either evolved rapidly 500 million years ago, or jellyfish developed much earlier than previously thought.

Further Evolution

There are very few pressures on Black Sea Nettle or other jellyfish to adapt. Actually, many problems that are negatively affecting other ocean species are having a positive impact on jellyfish species. This has lead to the potential overpopulation and expansion of jellyfish.

Global warming is slowly warming oceans. This is allowing jellyfish that prefer warmer waters to spread towards both poles away from the equator. Black Sea Nettle prefer moderate temperatures and this allows them to expand farther north along the North American coastline.

Global warming also targets predators of Black Sea Nettle including sharks, sea turtles and some large species of fish.

Fertilizers and nutrients from farms eventually end up in the ocean. Some plankton thrive on these nutrients. Jellyfish then have a constant food source and can also thrive.

Other than contributing to global warming and fertilizers in the ocean, humans also over fish predators. This problem alternates the food chain and puts the Black Sea Nettle on the top of the food chain. This is a problem because this species reproduces very quickly and with few natural predators, more of them would reach maturity. This would overpopulate the oceans with jellyfish.

Although Black Sea Nettle are fairly rare, they can be found off the west coast of North America. Ranging from Mexico to British Columbia. Major sightings were reported near California in 1989 and 1999.


Black Sea Nettle have a very unusual reproductive cycle that is common to nearly all other jellyfish.

First, male jellyfish (XY sex chromosomes) produce sperm in their gonads. Likewise females (XX sex chromosomes) produce eggs in their gonads. The males release the sperm into the water. As the females swim through the water, the eggs attached on the upper oral arms are fertilized.

The eggs undergo embryonic development similar to all animals.After about two weeks, the eggs hatch into tiny larvae called "planulae".

Planulae are oblong and have cilia (hair-like structure) for movement.

A mother can produce thousands of planulae. Most of them will be eaten before they reach maturity. The planulae eventually settle onto a surface.

They attach to the surface and develop into "polyps." One end attaches to the surface and the other end that has tentacles draws food in.

A polyp attached to the ocean floor.

After the polyp becomes more mature, which may take years, polyps can asexually reproduce and split off into more polyps. Polyps will also start to develop horizontal lines around the stalk that eventually will become a stack of saucers.

Each saucer will develop into a baby jellyfish called an "ephyrae". About 5 to 15 ephyrae will come from the polyp. This is another example of asexual reproduction.

An example of a polyp with ephyrae ready to separate.

These ephyrae quickly develop into the popular form of jellyfish, the "medusa". The medusa is sexually mature after a few months and only lives for about 6 months to a year.


The Black Sea Nettle may have anywhere from 44 to 216 chromosomes (the actual number was not found). These chromosomes are comprised of DNA and are diploid. This means that every chromosome is paired with another that contains identical data.

An electron microscopy image of chromosomes.

There are no know genetic disorders that affect jellyfish.

Dihybrid Cross

*Note that these alleles were created and may not reflect scientific evidence*

Black Sea Nettle that are dark red have the dominant trait for coloration (C). Black Sea Nettle that are dark purple have the recessive trait for coloration (c).

Large Black Sea Nettle are homozygous with the (Sᶫ) allele. Small Black Sea Nettle are homozygous with the (Sˢ) allele. Medium sized jellyfish are heterozygous with both the (Sᶫ) and (Sˢ) allele.

A heterozygous dark red and large sized male mates with a heterozygous dark red and small female. What are the possible phenotypes and genotypes of their children?

The male is (CcSᶫSᶫ) with a possibility of CSᶫ or cSᶫ.

The female is (CcSˢSˢ) with a possibility of CSˢ or cSˢ.

A punnet square showing the possible genotypes of the offspring.

This shows that 100% of the offspring will be medium sized. Also, the offspring will have a 75% chance of being dark red while having a 25% chance of being dark purple. The genotypes of the offspring can be described as a 1:2:1 ratio

  • 1: homozygous dark red, heterozygous medium size
  • 2: heterozygous dark red, heterozygous medium size
  • 1: homozygous dark purple, heterozygous medium size

dIGESTIve System

All jellyfish, including the Black Sea Nettle have a simple digestive system. This means that nutrients are obtained and excreted in the same opening.

A labelled diagram of the digestive system of both the polyp and medusa stages.

The mouth and anus opening can be found in the center at the bottom of the medusa. This opening leads to the gastrovascular cavity in the very center of the jellyfish. It is lined with the gastrodermis which is only one or two cells thick. Some enzymes help break down the food while the gastrodermis absorbs nutrients. Waste is expelled quickly out of the mouth and anus opening so the jellyfish is not weighed down.

Food Source

Black Sea Nettle eat zooplankton, other jellyfish, fish and crustaceans like krill.

Jellyfish are all carnivores and often attempt to eat anything that crosses their paths. They are 95% water and require very little energy. They do not have a brain or any other major energy requiring organs. Also, their movements are incredibly efficient even though they usually flow with ocean currents anyways.

The Black Sea Nettle requires some protein as well as lipids and carbohydrates. It is unknown if jellyfish are using vitamins and minerals from the food they consume.

There are few limitations to the Black Sea Nettle's food source. Zooplankton are extremely common and the jellyfish are able and willing to consume nearly any prey that it comes in contact with. However, if the jellyfish are not consuming enough nutrients, it can stop moving and flow with the ocean currents if necessary.

Catching Prey

Jellyfish have a unique and effective way to capturing prey. They use their tentacles and water currents to catch their prey.

The stinging tentacles of the Black Sea Nettle.

Their tentacles are covered in nematocysts which are tiny stinging barbs that shoot out and inject a neurotoxin that paralyzes it's prey. The oral arms then direct the prey through the mouth.

When jellyfish open and contract their bell, they create water currents that direct prey towards their tentacles and plankton towards their mouth. So, the Black Sea Nettle passively collects zooplankton.

This is an effective and efficient system. The jellyfish does not have to spend any energy chasing prey. With the water currents, prey comes directly to the jellyfish. Also, because of the tentacles, the jellyfish does not need to spend energy fighting with it's prey. Jellyfish do not need to see, hear, smell or taste their prey and only need to feel their prey.

Circulatory System

Jellyfish actually do not have a circulatory system or any blood. Instead nutrients and oxygen diffuse into the jellyfish. Diffusion occurs when an area of higher concentration spreads into an area of lower concentration. In this case, the oxygen and nutrients travel from the water and through cells into the jellyfish.

Sea Nettle lies on sand out of water.

The skin of jellyfish, including the gastrovascular cavity, is only a few cells thick. This contributes to the transparency of most species. So, this allows simple diffusion of the nutrients and oxygen into the jellyfish. From there, the oxygen and nutrients continue to diffuse into the neighboring cells.

Osmosis is a process that moves a solvent (water) through cells. The water in the jellyfish have the same concentration of solute (dissolved substance) as the water around them.

This system is beneficial to the Black Sea Nettle because oxygen and nutrients can move around it's entire body without wasting energy or needing another circulation system. It's important to note that this is only possible due to thin body tissues and lack of muscle mass and other tissues, as these tissues would require higher levels of oxygen and nutrients.

Little is known about the immune system of jellyfish.

Close up images of stranded Black Sea Nettle express the deep purple coloration they were named after.

The End


Black sea nettle. (n.d.). Retrieved January 13, 2017, from

Boltovskoy, D. (n.d.). Marine Species Identification Portal : Family Pelagiidae. Retrieved October 02, 2016, from

Cnidaria. (n.d.). Retrieved January 5, 2017, from

Cripps, K. (2013, November 6). Jellyfish taking over oceans, experts warn. Retrieved November 24, 2016, from

G, S. (n.d.). Virtual Zoo - Chrysaora achlyos. Retrieved September 20, 2016, from

How Do Jellyfish & Sea Anemones Digest Their Food? (n.d.). Retrieved January 5, 2017, from

Jellyfish. (2008, August 29). Retrieved January 5, 2017, from

Jellyfish. (2016, December 25). Retrieved January 05, 2017, from

Jellyfish Anatomy - Diagram Of A Jellyfish Physiology. (n.d.). Retrieved September 02, 2016, from

Jellyfish Energy Consumption. (2013, October 17). Retrieved January 5, 2017, from

Jellyfish, dried, salted Nutrition Facts & Calories. (n.d.). Retrieved January 05, 2017, from

Ocana-Luna, A., & Sanchez-Remirez, M. (2009). Marine Biology Research. Retrieved January 05, 2017, from

Osmosis. (n.d.). Retrieved January 5, 2017, from

PACIFIC SEA NETTLE JELLYFISH. (n.d.). Retrieved January 4, 2017, from

Pelagiidae - Details. (n.d.). Retrieved September 20, 2016, from

Starr, B. (2014, February 28). Understanding Genetics. Retrieved January 04, 2017, from

Strauss Animals & Wildlife Expert, B. (n.d.). How Jellyfish Grow, From Eggs to Polyps to Medusas. Retrieved December 1, 2016, from

Thompson, A. (2007, October 30). Oldest Known Jellyfish Fossils Found. Retrieved October 28, 2016, from


Black Sea Nettle ("Chrysaora Achlyos") [Photograph found in Montery Bay Aquarium]. (n.d.). Retrieved January 07, 2017, from,_Black_Sea_Nettle_(%22Chrysaora_Achlyos%22),_Monterey_Bay_Aquarium,_Monterey,_California,_USA_(5513375649).jpg (Originally photographed 2009, January 19)

Draginda, J. (2012, February 20). Chrysaora fuscescens. Retrieved January 07, 2017, from

Fleetham, D. (2012, July 29). Compass Jellyfish. Retrieved January 07, 2017, from

Large Solnhofen Medusites Jellyfish Fossil with Tentacles. (n.d.). Retrieved January 07, 2017, from

Martin, B. (2012, July 20). Ocean Oil Rig [Photograph found in Oil Rig Photographs, Fine Art America]. Retrieved January 07, 2017, from,d.amc&psig=AFQjCNE1FOAgD8sIcJBg35oMQDrNz-hmbA&ust=1484153153240176

Pelagia noctiluca [Photograph found in Most Beautiful Things]. (n.d.). Retrieved January 07, 2017, from

Purple-striped jelly. (n.d.). Retrieved January 07, 2017, from

Triple Cambrian Jellyfish Fossil from Krukowski Quarry. (n.d.). Retrieved January 07, 2017, from

Photos not referenced were found from the Adobe Spark browser.

Created By
LIam Koch Nichol


Created with images by jimg944 - "DSC26402, Black Sea Nettle ("Chrysaora Achlyos"), Monterey Bay Aquarium, Monterey, California, USA" • TravelingShapy - "underwater" • Pexels - "ocean sea submerged" • Pexels - "birds cold frozen" • jeffk - "Jellyfish Swarm" • Unsplash - "freight tanker vessel" • Michio Morimoto - "DSC_0043_001" • Michio Morimoto - "new_0003" • EvanHahn - "Sea thinger" • Barta IV - "Jellyfish-5218" • Lawrie83 - "fish" • NOAA Photo Library - "fish9052" • lyng883 - "DSC00271-Black Sea Nettles" • lyng883 - "DSC26398-Black Sea Nettles" • lyng883 - "DSC26401-Black Sea Nettles" • jimg944 - "DSC26397, Black Sea Nettle ("Chrysaora Achlyos"), Monterey Bay Aquarium, Monterey, California, USA" • Jan-Mallander - "jellyfish beach sea" • Port of San Diego - "Black Sea Nettles in San Diego Bay"

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