Periphylla periphylla are bioluminescent at all stages of life, and this bioluminescence may be used as a warning to predators. Periphylla periphylla react to light - it can be lethal to those mature individuals. Members of this species lack an acoustically sensitive organ (such as the gas bladder of fish) and react very little to sound. They also react to tactile stimulation, producing bioluminescent light that spreads from the point of stimulation to the nerve nets of the individual.
Communication Channels: visual
Other Communication Modes: photic/bioluminescent
Perception Channels: infrared/heat ; tactile ; chemical
In the Northern Atlantic ocean, two common predators of P. periphylla at depths of below 1000 meters are Alepocephalus bairdii and Coryphaenoides rupestris. A third predator is the pelagic shrimp Notostomus robustus. Along with nematocysts, the bioluminescence could be a form of defense, as it may repel potential predators by signaling danger or distastefulness. Anemones, such as Isotealia antarctica, are also potential predators, as well as sea spiders, if they are able to make contact with an individual.
Known Predators:
Anti-predator Adaptations: aposematic
Periphylla periphylla are deep-sea medusae with twelve stiff tentacles, which extend from a thick, bell shaped body. These animals have dark red and/or brown stomachs, and are bioluminescent. They can be up to 20 cm long, and their bodies, or central domes, have a diameter of up to 35 cm. The coronal groove, located on the lower portion of the bell, helps to contain prey, and also provides flexibility for movement. The coronal groove divides the aboral surface into the central dome and the peripheral zone, which contains radial thickenings called pedalia and marginal lappets that contain some sense organs. This zone also contains the tentacles, which are useful in moving prey to the mouth. The mouth is very simple and is located on the manubrium. Externally, males and females of this species are similar. No indication of geographical or seasonal variation was reported.
The pigment that gives P. periphylla their red-brown color is protoporphyrin (also known as porphyrin), which can lead to tissue damage as a result of photosynthesis. The pigment is not harmful to this species as they do not usually stay in shallow waters.
Periphylla periphylla contain relatively high levels of lactate dehydrogenase, an enzyme important to anaerobic metabolic functions. This is likely useful for movement in ocean layers with minimal amounts of oxygen.
The Q10 value of an organism is its temperature coefficient- the factor of change in respiration caused by an increase in temperature of 10 °C. The value for P. periphylla, calculated in the range of 5°C - 10°C, was found to be 2.6. This value indicates that temperature affects the biochemical reactions of the organism. A value of 1 would mean that the organism is insensitive to temperature.
The water content of P. periphylla is 95.7 - 96.6 percent of the total wet weight. The measured salinity of the surrounding water when this was measured was 33.1-33.3 percent.
Periphylla periphylla are one of the only five scyphozoan species that is bioluminescent. The bioluminescence, along with with its red-brown coloring and the direction of its tentacles, make it easy to distinguish. The blue or blue-green light emission occurs as a result of stimulation and is concentrated in specific parts of the organism, such as the marginal lappets and near the coronal groove. Members of these species exhibit bioluminescence as a response to a short pulse of alternating current with a series of flashes.
Range length: 20 (high) cm.
Other Physical Features: ectothermic ; heterothermic ; radial symmetry ; venomous
Sexual Dimorphism: sexes alike
Little is known about the lifespan of P. periphylla. However, individuals of this species may have relatively long lives compared to similar species, perhaps as much as several decades. Mortality might be slightly lower in Norwegian Fjords, where this species is abundant. The life span of these jellyfish is also affected by light exposure, which may cause its pigments to have a lethal affect on the individual.
Due to the large geographic range of P. periphylla, factors such as local predation and food availability should be taken into account while determining regional lifespans. For example, in clear water, predators might be more likely to find medusae, so the average lifespan may be lower.
Periphylla periphylla are difficult to maintain and raise for long periods of time, which may explain why no data have been recorded regarding the longevity of these medusae in captivity.
Average lifespan
Status: wild: 30 years.
These members of the Class Scyphozoa live anywhere from the surface to 1000 meters deep in the ocean. At night, or when feeding, they may get closer to the surface. This vertical migration occurs particularly at latitudes farther from the equator, as is the case of medusae under ice in Antarctica. Much research has focused on the abundance of P. periphylla in Norwegian fjords, where the distribution follows a vertical layering pattern. Distribution also seems to be strongly affected by the location of food, as well as physical conditions. For example, P. periphylla may not approach the surface if strong winds result in turbulence.
Periphylla periphylla tends to live in deeper waters in subtropical and tropical regions. Depths vary with latitude, as it can live in shallow areas north of 42°N. This species likely submerges when it is closer to the equator due to the temperature of the water in the surface layer. Periphylla periphylla can survive temperatures up to 19.8 °C, although most specimens are collected at temperatures between 4 °C and 11 °C. There may be a connection between temperature tolerance, temerature-dependent metabolic rates, and food supply. Vertical mixing can also affect the jellyfish's submerging at a certain latitude.
The vertical location of these jellyfish is also linked to light intensity. The pigment that gives P. periphylla red-brown color can have a lethal affect when exposed to light. Since light intensity is based on depth, individuals tend to migrate to depths with relatively low light exposure.
Range depth: 1000 to surface m.
Average depth: 500 m.
Habitat Regions: temperate ; tropical ; polar ; saltwater or marine
Aquatic Biomes: pelagic
Periphylla periphylla can be found in numerous locations around the world including the South Shetland Islands, South Sandwich Islands, South Georgia Island, the Southern Ocean, Antarctica, the Antarctic Peninsula, and other marine habitats worldwide. The only large body of water they are not found in is the Arctic Ocean. While it has a wide distribution, P. periphylla is significantly more abundant in some Norwegian Fjords.
Biogeographic Regions: nearctic (Native ); palearctic (Native ); oriental (Native ); ethiopian (Native ); neotropical (Native ); australian (Native ); antarctica (Native ); indian ocean (Native ); atlantic ocean (Native ); pacific ocean (Native ); mediterranean sea (Native )
Other Geographic Terms: cosmopolitan
Periphylla periphylla use tentacles to grasp their prey, and with the help of marginal lappets, bend them inwards to transfer the prey into the mouth of the individual. Some research has indicated that the location of prey has an effect on the movement of these medusae.
One of the earliest studies that was conducted on the diets of different scyphozoans included P. periphylla. Fourteen specimens contained food, and 100% of the prey were copepods, the majority being calanoid copepods. These medusae also feed on krill (such as Meganyctiphanes norvegica), a type of zooplankton, as well as chaetognaths and ostracods. They may also eat small fish and other medusae.
Animal Foods: fish; aquatic crustaceans; cnidarians; other marine invertebrates; zooplankton
Primary Diet: carnivore (Eats non-insect arthropods, Eats other marine invertebrates); planktivore
Pelagic amphipods, genus Hyperia, live on, or even in, P. periphylla. It has not yet been determined if they are parasitic.
Periphylla periphylla are predators of copepods, krill, chaetognaths, and ostracods. They are also the prey of organisms such as Alepocephalus bairdii and Coryphaenoides rupestris.
Due to their role as both predator and prey to other species, P. periphylla is part of several food webs, and it is possible that its presence is necessary to maintain the populations of its prey, and to the survival of its predators. This could, consequently, affect fishing industries. However, there are no well documented benefits that P. periphylla provide to humans.
The large abundance of P. periphylla in Norwegian fjords has impacted the local fishing industry, as they clog the nets used by fishermen. There have been no adverse effects of this species on humans reported in any other regions.
Studies on live specimens obtained from Lurefjorden in Norway showed the life cycle of P. periphylla involves direct development from egg to young medusae, lacking a planula, polyp stage, and an ephyra stage.
The life cycle contains a total of 14 developmental stages. Stage 1, which can last anywhere from 1 to 10 days, are the eggs, which are relatively large, and at first are sessile and on average, do not live as deep as fully grown individuals. In Stage 2 (5-14 days in duration), the egg has flattened slightly in the middle. In stage 3, the first signs of the coronal groove can be seen. In Stage 4 (6-16 days in duration), wavy structures may be observed, as well as radial lines pointing toward what will become the mouth. This is also the stage in which the first movements occur. By Stage 5, marginal lappets will have appeared, and the coronal groove is clearly visible. The main feature of Stage 6 is the newly developed tentacle buds. In this stage, one may also see larger marginal lappets, and the organism will have started to regain a spherical shape. Bell pulsations allow it to swim. The pigment porphyrin increases during development, although it first becomes visible in Stage 7, when the mouth also forms. In Stage 8, the tentacles are the same length as the marginal lappets, and the central disc begins to flatten. Individuals resembling young medusa, begin feeding and are fully motile in Stage 9. At this stage, marginal lappets will be at least 0.9 mm long. The duration of development from Stage 1 to 9 is estimated to last 2-3 months.
Pigmentation develops in the tips of the twelve tentacles by Stage 10. The pigmentation continues to spread in Stage 11, and by Stage 12, the tentacles are completely pigmented. In Stage 13, the marginal lappets and the coronal furrow are pigmented, and the pigment continues to move towards the bell.
The final stage, Stage 14, is when the medusa is completely pigmented. In this stage gonads appear and sexual dimorphism can be observed, however, the process of sex determination is unknown. At the end of this stage, the individual is a fully mature medusa.
Members of this species are bioluminescent, exhibiting a blue fluorescence, during all stages of life.
Periphylla periphylla is not a species that is not considered to be threatened, and it does not appear in any animal conservation databases. Much of the research done on this species has been sparked by the abundance of these medusae in Norwegian fjords.
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
Periphylla periphylla are known by several names, including duncecaps and helmet jellies.
While very little is known about the details of reproduction of P. periphylla, mating most likely occurs near the surface. One observation is that only mature individuals are found near the surface, whereas smaller, immature individuals tended to stay a little lower, even at night. Examination of these mature specimens revealed gonads with mature sperm or eggs (respective to the determined sex). Little is also known about the social structure of P. periphylla.
The life-cycle of P. periphylla does not depend on season, so at any one time, an individual may be at a different stage. Reproduction occurs year round.
Observers have also noted that patches of these medusae seem to be denser in water that have dust and foam, which might indicate that individuals take advantage of water movements in order to aggregate.
While there is little more conclusive knowledge about the mating behaviors of P. periphylla, observed behaviors are similar to those of Tripedalia cystophora and Carybdea sivickisi, whose individuals exhibit internal fertilization, achieved by the male holding the female until sperm is transferred. However, since it is now known that these individuals continuously spawn, it is possible that they exhibit external fertilization. In order to conclusively determine what occurs, further observations are required.
Mating System: polygynandrous (promiscuous)
Periphylla periphylla breeds year-round. Individuals of this species are either male or female, and they reproduce sexually. Very little is known about fertilization in this species, including whether external or internal fertilization occurs. The frequency of breeding has not been determined.
Individuals of this species undergo direct development, growing gradually in size throughout their 14 stages of development, from egg to sexual maturity. While the time from stage 1 to 9 is believed to be 2-3 months, the length of time until sexual maturation is still unknown.
Female members of this species continuously produce a few, relatively large, eggs over a long period of time. Upon maturation they spawn (release gametes) continuously.
One unique feature of P. periphylla that separates it from other species of the Order Coronatae is that the medusae have complete and fully developed follicles.
Breeding interval: The breeding interval of Periphylla periphylla is currently undetermined.
Breeding season: Periphylla periphylla breed year-round.
Key Reproductive Features: iteroparous ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual
Observations of parental involvement of mature P. periphylla have not been made. Other scyphozoan species, however, do not display this behavior.
Parental Investment: no parental involvement
The helmet jellyfish (Periphylla periphylla), sometimes called the merchant-cap,[1] is a luminescent, red-colored jellyfish of the deep sea, belonging to the order Coronatae of the phylum Cnidaria. It is the only species in the monotypic genus Periphylla and is one of the rare examples in Scyphozoa which life-cycle lacks a polyp stage. This species is photophobic and inhabits deeper parts of the oceans to avoid light. It may be found at the surface on dark nights.
Helmet jellyfish reach a body size of up to 30 cm (12 in). The average wet weight of the jellyfish is 540 grams.[2] Overall, helmet jellyfish have a uniform size.[3] They consist 90% of water, the rest being tissue and gelatinous mass, which give the animals their form. They light themselves from within by means of bioluminescence, the red flashes serving as a signal amongst themselves. Between their marginal lobes sit small sense bulbs, by which the helmet jelly can distinguish between light and dark; they have been observed to avoid light. Their nature of avoiding light has given them the title of being photophobic. They have a biochemical content that consists of having a small amount of carbohydrates, average amount of lipids, and a large content of protein. The helmet jellyfish have twelve tentacles that consist of layers of endoderm and mesoglea, but each jellyfish can have a different type of tentacle posture. Through observational studies, it was found that within fifty-one of the observed jellyfish, there were eight different tentacle postures. The two most common type of tentacle postures are straight-extended tentacles with a forty-five degree angle in respect to the oral-aboral body axis, and straight-extended tentacles with a forty-five to ninety degree angle in respect to the oral-aboral body axis.[4] These tentacle postures are how each individual helmet jellyfish swims.[5]
The jellyfish is found in depths up to 2700 meters and is adapted to its dark environment.[6] Not only have they become adapted and more abundant in darker environments, but they are also found in very opaque and cloudy waters.[7] They are found in these deep and dark waters due to the fact that sunlight can be very harmful to adult helmet jellyfish, and even deadlier to younger helmet jellyfish.[8] The depth that they can be found at varies throughout the day. They're found in abundance at a depth of approximately 13.75 m during the nighttime, and as deep as 150 m during the daytime. The abundance of helmet jellyfish at the depth of 150 m during the day time is nearly three times the abundance of them found during the nighttime. The jellyfish were also seen as far below the surface as 250 m. At this depth, one-third of the total population inhabited the lower water column during daylight while less than 10% were found at the same depths after the sun had gone down.[9] This observation of migration shows that they are constantly migrating vertically throughout the depths of water based on the amount of available sunlight at the given time.[10] However, they can also be seen commonly at different depths depending on their physical size and age. Helmet jellyfish consistently have been found at higher depths, across different locations, if they are smaller in size or are less fit juveniles.[11]
Through their vertical swimming, the jellyfish can swim several different speeds. The majority of their vertical swimming is seen at a speed of <2 cm/s. If they are swimming at full speed they can reach over 10 cm/s, but this is only for a short time span. If they do reach this speed, it is assumed that they follow this with a time of no vertical movement.[12] In 2017, many helmet jellyfish were caught to be studied to determine their main prey. In this experiment it was found that each jellyfish had only an average of five different species of prey in their digestive system. The prey in their digestive system was examined as well as the abundance of the prey. There was a 27% abundance of copepods, 23% abundance of pteropods, 20% abundance of amphipods, 17% abundance of euphausiids, and a 13% abundance of chaetognaths.[13] With a full stomach it turns from the surface back to the depths. Other deep-sea inhabitants feed upon its faeces. They move by swimming with their tentacles being in an aboral position.[14] Their tentacles also have various unique muscles. These include longitudinal, ring-, radial-, and diagonal musculatures. The two most unique are the longitudinal and the diagonal musculature. The longitudinal is used for consuming prey by moving very quickly to the jellyfishes mouth. The diagonal is used for the corkscrew reaction that is used in order to obtain and capture prey.[4]
Periphylla periphylla represents an exception, very rarely found in the phylum Cnidaria: the medusae do not go through a polyp stage, thus presenting a "holopelagic" life cycle. They also do not undergo an ephyra stage as well as a sessile stage.[15] The helmet jellyfish is also unique in its growth and sexual reproduction in that they are the only known scyphozoan that undergoes sexual propagation but lacks the planula stage.[2] During reproduction, the female helmet jellyfish contain thousands of eggs within their gonads. Their eggs are actually the largest sized eggs within all Cnidaria. Despite the eggs being very large, females will only produce a small number of eggs.[16] The jellyfish release their eggs on the surface of the water, where they rapidly sink to a depth that limits visibility of predators.[17] The medusae release fertilized eggs in open water and these develop directly into medusae, whose development rests entirely upon the egg's high yolk supply. This yolk supply is seen during the first stage of development and is found inside of a network of plasma strains. This is when nuclei dispersed, and many of them are only found during this stage. During the second stage of development a minor indentation is seen. This will then later develop into a mouth. The yolk supply has by then shrunk to only one to two layers above the nucleus. An acid mucus develops through secretion of the endodermal layer. As the jellyfish enters its third stage of development a smooth pit is visible on its anterior end. There is the first indication of a mouth, and their body shape resembles a hat. The amount of yolk granules decrease throughout this stage, and occur in three to four layers. The fourth stage of development shows their “umbrella” to have four indentations which creates the gastric septa on its inside. This stage is when there is the first indication of a histone. As for stage five, there are now sixteen lappets and four rhopalic buds developed. Their medusa shape is much more defined. There is also nearly no yolk present. Stage six of development is when the first glimpse of an opaque jelly is seen. At the end of the hypstome, the cross-shaped mouth is now opened. The seventh stage of development is when they begin to take on their medusa jellyfish shape. They have twelve tentacles as well as four interradial rhopalia. They do not begin to show pigmentation in this stage, but this stage is when cilia is first seen. The final eighth stage is known for when the purple pigmentation of the helmet jellyfish is now seen in their mouth and stomach.[2]
The helmet jelly is found in nearly every ocean of the world, as well as in the Norwegian fjords and in the Mediterranean Sea. The only ocean they are not known to inhabit is the Arctic Ocean. They can also be found in the Iceland and Greenland Seas. Additionally, there has been an increase in their population throughout the northern Barents Sea in recent years. The helmet jellyfish has also been found commonly in Arctic fjords that are located within Lurefjorden and western Spitsbergen, Norway.[18][17] Their distribution throughout these different locations are greatly influenced by the depths of water, abundance of food sources, and preferred light intensities.[19] Their distribution can also be affected by physical conditions. They have been observed to position themselves further from the surface of the water if there are harsh weather conditions[16] or to avoid too much sunlight.[9] Their distribution can also be affected by water temperature. The vast majority of helmet jellyfish live in temperatures ranging from 4 - 11°C but they are able to survive in water temperatures reaching up to nearly 20°C.[20]
{{cite journal}}: Cite journal requires |journal= (help) The helmet jellyfish (Periphylla periphylla), sometimes called the merchant-cap, is a luminescent, red-colored jellyfish of the deep sea, belonging to the order Coronatae of the phylum Cnidaria. It is the only species in the monotypic genus Periphylla and is one of the rare examples in Scyphozoa which life-cycle lacks a polyp stage. This species is photophobic and inhabits deeper parts of the oceans to avoid light. It may be found at the surface on dark nights.
