''Phacellophora camtschatica'', commonly known as the fried egg jellyfish or egg-yolk jellyfish, is a very large
jellyfish
Jellyfish and sea jellies are the informal common names given to the medusa-phase of certain gelatinous members of the subphylum Medusozoa, a major part of the phylum Cnidaria. Jellyfish are mainly free-swimming marine animals with umbrella- ...
in the family
Phacellophoridae
''Phacellophora camtschatica'', commonly known as the fried egg jellyfish or egg-yolk jellyfish, is a very large jellyfish in the family Phacellophoridae. This species can be easily identified by the yellow coloration in the center of its body w ...
. This species can be easily identified by the yellow coloration in the center of its body which closely resembles an egg yolk, hence how it got its common name. Some individuals can have a bell close to 60 cm (2 ft) in diameter,
and most individuals have 16 clusters of up to a few dozen tentacles, each up to 6 m (20 ft) long.
A smaller jellyfish, ''
Cotylorhiza tuberculata'', typically found in warmer water, particularly in the Mediterranean Sea, is also popularly called a fried egg jellyfish. Also, ''P. camtschatica'' is sometimes confused with the Lion's mane jellyfish (''
Cyanea capillata
The lion's mane jellyfish (''Cyanea capillata''), also known as the giant jellyfish, arctic red jellyfish, or the hair jelly, is one of the largest known species of jellyfish. Its range is confined to cold, boreal waters of the Arctic, norther ...
'').
It feeds primarily by collecting
medusae
Jellyfish and sea jellies are the informal common names given to the medusa-phase of certain gelatinous members of the subphylum Medusozoa, a major part of the phylum Cnidaria. Jellyfish are mainly free-swimming marine animals with umbrella- ...
and
plankton
Plankton are the diverse collection of organisms found in Hydrosphere, water (or atmosphere, air) that are unable to propel themselves against a Ocean current, current (or wind). The individual organisms constituting plankton are called plankt ...
with its tentacles, and bringing them into its mouth for digestion. It is capable of only limited motion, and mostly drifts with the current, even when swimming. This species and most of its relatives in the Cnidaria phylum often use suspension feeding as their main food gathering strategy.
The body of this jellyfish does not contain any respiratory, circulatory, or excretory systems. Instead, it uses its large surface area to accomplish these things. Also, this species (and all others in the phylum
cnidaria
Cnidaria () is a phylum under kingdom Animalia containing over 11,000 species of aquatic animals found both in freshwater and marine environments, predominantly the latter.
Their distinguishing feature is cnidocytes, specialized cells that th ...
) lack a mesoderm and instead uses mesolgea. Therefore, there are not three true tissue layers, in turn making this species (and all other cnidarians) diploblastic not triploblastic.
The reproduction and life cycle of this jellyfish has been well documented. It mostly follows the same life cycle as other members in the class
Scyphozoa
The Scyphozoa are an exclusively marine class of the phylum Cnidaria, referred to as the true jellyfish (or "true jellies").
The class name Scyphozoa comes from the Greek word ''skyphos'' (), denoting a kind of drinking cup and alluding to the ...
. It alternates between a polyp form that reproduces asexually and a medusa form that reproduces sexually. These jellyfish are a cool water species found in most of the world’s oceans, but most commonly in the Northern Pacific.
Taxonomy and systematics
''P. camtschatica'' is a large jellyfish that has a yellow center, resembling a broken egg yolk, surrounded by opaque, white tissue. This jellyfish is the representative of the family Phacellophoridae in the class of
Scyphozoa
The Scyphozoa are an exclusively marine class of the phylum Cnidaria, referred to as the true jellyfish (or "true jellies").
The class name Scyphozoa comes from the Greek word ''skyphos'' (), denoting a kind of drinking cup and alluding to the ...
.This jellyfish was once believed to be part of the family, Ulmaridae, but the juvenile characteristics did not match the family characteristics of
Ulmaridae
The Ulmaridae are a family of jellyfish.
Genera
Formerly, the genus '' Phacellophora'' was also included in this family, but is now placed in the family Phacellophoridae.Straehler-Pohl, I., C. L. Widmer, and A. C. Morandini (2011). ''Characteri ...
or
Cyaneidae
The Cyaneidae are a family of true jellyfish. About 20 species are in this family, including the well-known lion's-mane jellyfish.
Species
The following species are recognized within the family Cyaneidae. Formerly, this family also included th ...
. Due to these findings, the family Phacellophoridae was created specifically for this species, serving as an intermediate between Cyaneidae and Ulmaridae.
Key distinguishing features are a gastric cavity with radial canals joining a marginal ring canal, as well as broad curtain-like oral arms; and subumbrellar tentacles in 16 linear clusters. Currently, ''P. camtschatica'' is the sole member of the family Phacellophoridae. However, the latest phylogenetic analyses actually suggest the genus Phacellophora is a member of the family Ulmaridae.
Furthermore, cryptic diversity is evident within the genus ''Phacellophora'', with at least three or four distinct species.
[
]
Ecology
Feeding
''Phacellophora camtschatica'' mainly feeds on gelatinous zooplankton and smaller jellyfish, which become ensnared within the tentacles. Tentacles contain nematocysts
A cnidocyte (also known as a cnidoblast or nematocyte) is an explosive cell containing one large secretory organelle called a cnidocyst (also known as a cnida () or nematocyst) that can deliver a sting to other organisms. The presence of this c ...
, which help in prey capture. These structures also provide defense against predation. Food that is caught in the tentacles is then covered in mucous, then these tentacles are brought to the mouth by oral lobes. Food is then digested by digestive enzymes in the gastrovascular cavity. Broken down food is then distributed throughout the jellyfish by ciliary action.
''Phacellophora camtschatica'' feeds on a great variety of taxa, including euphausiids, cladocerans, and decapod zoea, fish (including fish larvae), and especially other jellyfish such as Aurelia spp., ctenophores and Pelagia noctiluca.[ The fried egg jellyfish have been known to host symbionts that will transfer onto ''P. camtschatica'' when the host is consumed. This is possible because the sting of this jellyfish is weak therefore allowing many symbionts/parasites including small crustaceans like larval crabs ('' Cancer gracilis'') and some ]Amphipoda
Amphipoda is an order of malacostracan crustaceans with no carapace and generally with laterally compressed bodies. Amphipods range in size from and are mostly detritivores or scavengers. There are more than 9,900 amphipod species so far desc ...
(''Hyperia medusarum)'' to regularly ride on its bell and even steal food from its oral arms and tentacles.
Symbiotic Relationships
''Phacellophora camtschatica'' has symbiotic relationships with larval crabs (''Cancer gracilis),'' in which the crabs feed on the parasitoid Amphipoda (''Hyperia medusarum)'' that also resides on the bell of the jellyfish. Larval crabs benefit from this relationship by riding on the bell of the medusa or within the tentacles to gain food and develop faster due to locomotion through warmer surface waters without expending extra energy. When the juvenile crabs first associate with the jellyfish, the crab feeds on the tentacles and preys on small plankton from the water and the hosts’ surface. As the crab develops into an instar, it begins to feed on the parasitoid Amphipoda (''Hyperia medusarum)'', which aids the jellyfish in keeping the parasitic impact low''.'' Although a symbiotic relationship exists between juvenile ''Cancer gracilis'' and the jellyfish, when the ''C. gracilis'' matures it begins to feed more substantially on the jellyfish itself; other predators include crabs (''Cancer productus
''Cancer productus'', one of several species known as red rock crabs, is a crab of the genus ''Cancer'' found on the western coast of North America. This species is commonly nicknamed the Pearl of the Pacific Northwest.
Description
''Cancer p ...
'' and ''Pugettia producta
''Pugettia producta'', known as the northern kelp crab or shield-backed kelp crab, is a species of crab in the family (biology), family Epialtidae.
Distribution
Found along the Pacific Coast of North America from southern Alaska to northern Mex ...
)'' and the giant deep-sea octopus, ''Haliphron atlanticus
The seven-arm octopus (''Haliphron atlanticus'') is one of the two largest known species of octopus; based on scientific records, it has a maximum estimated total length of and mass of . The only other similarly large extant species is the gian ...
'', which clings to the jellyfish and consumes its oral arms and stomach.
Body systems
''Phacellophora camtschatica'' does not have respiratory
The respiratory system (also respiratory apparatus, ventilatory system) is a biological system consisting of specific organs and structures used for gas exchange in animals and plants. The anatomy and physiology that make this happen varies grea ...
organs such as gill
A gill () is a respiratory organ that many aquatic organisms use to extract dissolved oxygen from water and to excrete carbon dioxide. The gills of some species, such as hermit crabs, have adapted to allow respiration on land provided they are ...
s, lung
The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of t ...
s or trachea
The trachea, also known as the windpipe, is a Cartilage, cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all air-breathing animals with lungs. The trachea extends ...
. Instead, it respires by diffusing
Molecular diffusion, often simply called diffusion, is the thermal motion of all (liquid or gas) particles at temperatures above absolute zero. The rate of this movement is a function of temperature, viscosity of the fluid and the size (mass) of ...
oxygen from water through the thin membrane covering its body. Within the gastrovascular cavity, low oxygenated water can be expelled through the mouth and high oxygenated water can be distributed by ciliated
The cilium, plural cilia (), is a membrane-bound organelle found on most types of eukaryotic cell, and certain microorganisms known as ciliates. Cilia are absent in bacteria and archaea. The cilium has the shape of a slender threadlike projecti ...
action, thus increasing the diffusion of oxygen into the cells. The large surface area to volume ratio helps to diffuse more oxygen and nutrients into the cells. Similarly, this animal lacks dedicated respiratory, excretory
Excretion is a process in which metabolic waste
is eliminated from an organism. In vertebrates this is primarily carried out by the lungs, kidneys, and skin. This is in contrast with secretion, where the substance may have specific tasks aft ...
, and circulatory system
The blood circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate. It includes the cardiovascular system, or vascular system, tha ...
s because of the high surface area to volume ratio.
The basic body plan consists of several parts. Food travels through the muscular manubrium
The sternum or breastbone is a long flat bone located in the central part of the chest. It connects to the ribs via cartilage and forms the front of the rib cage, thus helping to protect the heart, lungs, and major blood vessels from injury. Sha ...
while the radial canals help disperse the food. The fried egg jelly and all other members of the phylum Cnidaria are diploblastic. This is due to a lack of a mesoderm
The mesoderm is the middle layer of the three germ layers that develops during gastrulation in the very early development of the embryo of most animals. The outer layer is the ectoderm, and the inner layer is the endoderm.Langman's Medical E ...
, which in this phylum is replaced with mesoglea
Mesoglea refers to the extracellular matrix found in cnidarians like coral or jellyfish that functions as a hydrostatic skeleton. It is related to but distinct from mesohyl, which generally refers to extracellular material found in sponges.
Descr ...
. The tissue layers of this species is a middle layer of mesoglea
Mesoglea refers to the extracellular matrix found in cnidarians like coral or jellyfish that functions as a hydrostatic skeleton. It is related to but distinct from mesohyl, which generally refers to extracellular material found in sponges.
Descr ...
, a gastrodervascular cavity with a gastrodermis The gastrodermis is the inner layer of cells that serves as a lining membrane of the gastrovascular cavity of Cnidarians. The term is also used for the analogous inner epithelial layer of Ctenophore
Ctenophora (; ctenophore ; ) comprise a ph ...
, and an epidermis
The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and hypodermis. The epidermis layer provides a barrier to infection from environmental pathogens and regulates the amount of water rele ...
. Additionally, there is a nerve
A nerve is an enclosed, cable-like bundle of nerve fibers (called axons) in the peripheral nervous system.
A nerve transmits electrical impulses. It is the basic unit of the peripheral nervous system. A nerve provides a common pathway for the e ...
net that is responsible for contractions in swimming muscles and responses while feeding.
Cnidaria
Cnidaria () is a phylum under kingdom Animalia containing over 11,000 species of aquatic animals found both in freshwater and marine environments, predominantly the latter.
Their distinguishing feature is cnidocytes, specialized cells that th ...
ns have radial symmetry, in which tentacles are radially symmetric about the mouth, and have two main body surfaces, an oral surface and an aboral surface. During polyp stage, the oral surface is oriented upwards, but during medusa stage the oral surface is oriented downwards for more efficient mobility.
Life Cycle
The life cycle of this jellyfish is well known, because it is kept in culture at the Monterey Bay Aquarium
Monterey Bay Aquarium is a nonprofit public aquarium in Monterey, California. Known for its regional focus on the marine habitats of Monterey Bay, it was the first to exhibit a living kelp forest when it opened in October 1984. Its biologists ...
. During its life cycle, it alternates between an asexual benthic
The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from ancient Greek, βένθος (bénthos), meaning "t ...
polyp stage attached to rocks and piers and a sexual planktonic medusa stage that reproduces in the water column; both males and females occur in the plankton form.
The life cycle begins by eggs being fertilized, then developing into planula
A planula is the free-swimming, flattened, ciliated, bilaterally symmetric larval form of various cnidarian species and also in some species of Ctenophores. Some groups of Nemerteans also produce larvae that are very similar to the planula, which ...
e that are covered in cilia. These planulae swim for roughly 3–5 days before settling by attaching to the bottom and transforming, or metamorphosing, into the polyp (scyphistomae) stage. Once in the polyp stage, the scyphistomae undergoes a series of 2-,4-,8-,and 16- tentacled stages of development, each representing a difference in the overall shape of the calyx and symmetry amongst tentacles. When the polyp is mature, with 30-44 tentacles present, asexual proliferation occurs via side budding, one bud per polyp, and strobilating. During strobilation, the polyp is lengthened and thinned while tentacles are shortened and thickened, and mature ephraye are released.
When ephyrae are released, a cruciform mouth is present with nematocyst
A cnidocyte (also known as a cnidoblast or nematocyte) is an explosive cell containing one large secretory organelle called a cnidocyst (also known as a cnida () or nematocyst) that can deliver a sting to other organisms. The presence of this ce ...
batteries scattered throughout. As ephraye mature, the tentacles elongate and become filiform. Medusae reach larger bell diameters, additional tentacles form and oral arms elongate. Gastric system develops in a centrifugal direction. After roughly 9 months (under laboratory conditions), sexual maturity is achieved and reproduction can be achieved within the water column. The cycle then repeats all over again.
Distribution
This cool-water species are found in many parts of the world's oceans even though the abundance of this species in open marine waters is relatively low. Though, it can be rather abundant in some parts of the Sea of Japan and the Sea of Okhotsk, especially near the shore where it was found to dominate in the southern part of this area. However, most individuals are found in isolation. It was also found in the western and eastern Bering Sea. Additionally, it constituted a noticeable proportion of jellyfish biomass in waters of the northern California Current.
In a study conducted in 2011'','' the egg-yolk jelly was found to aggregate mostly over deep basins, whereas in shallow areas a significant quantity of this species was found only off West Kamchatka, This is in stark contrast to the other members of the family Ulmaridae (since it is no longer a member) which prefer shallow water. This preference could be related to the bell size of the individual which ranges from 5–59 cm. This bell size likely allows the jellyfish to swim in deeper waters by resisting stronger water currents and pressure.
Also, jellyfish populations (including the egg-yolk jelly) are on the rise in degraded areas as a result of increased tolerance to detrimental factors. Additionally, jellyfish play a large role in the food web and can serve as indicators of ecosystem structure and function; The larger the jellyfish population, the greater the negative impact on ecosystem services.
The fried egg jellyfish typically moves faster during the day and swims fastest during flood tides. This jellyfish undergoes vertical migrations that span the water column throughout short and long time frames. These vertical migrations allow them to enter the low depth of the hypoxia zone.
This species typically resides below the pycnocline
A pycnocline is the Cline (hydrology), cline or layer where the density gradient () is greatest within a body of water. An ocean current is generated by the forces such as breaking waves, temperature and salinity differences, wind, Coriolis effec ...
and avoids crossing the boundary layer, but they often dive into the hypoxic layer during the day when competition is high. By diving deep into the hypoxia zone, the fried egg jellyfish evades competition; unlike other species where hypoxia
Hypoxia means a lower than normal level of oxygen, and may refer to:
Reduced or insufficient oxygen
* Hypoxia (environmental), abnormally low oxygen content of the specific environment
* Hypoxia (medical), abnormally low level of oxygen in the tis ...
generally causes species to move away from the oxygen depleted zone, the fried egg jellyfish is able to withstand low oxygen levels for several hours at a time. And, with the belief that hypoxia
Hypoxia means a lower than normal level of oxygen, and may refer to:
Reduced or insufficient oxygen
* Hypoxia (environmental), abnormally low oxygen content of the specific environment
* Hypoxia (medical), abnormally low level of oxygen in the tis ...
regions will continue to grow, the fried egg jellyfish could thrive.
References
External links
Image of ''Phacellophora camtschatica''
{{Taxonbar, from=Q2352335
Semaeostomeae
Animals described in 1835
Taxa named by Johann Friedrich von Brandt
Cnidarians of the Pacific Ocean