Feeding, nutrition, & growth
 

There is an extensive literature on feeding in jellyfishes in the scientific journals, most notably for the cosmopolitan Aurelia aurita, but little is known for other west-coast species.  A few examples of feeding, nutrition, and growth from these other worldwide studies on A. aurita are included here.

Any references to moon jellies Aurelia aurita on the west coast of North America should be corrected to A. labiata. Some Research Studies below are so corrected, but not all. Any references to moon jellies Aurelia aurita in other parts of the world are, of course, correct.

  black dot
Research study 1
 

drawing of juvenile jellyfish Aurelia aurita with recently eaten fishLaboratory tests at the Pacific Biological Station, Departure Bay, British Columbia confirm that adult jellyfishes Aurelia aurita eat larval herring Clupea harengus pallasi.  Distributions of both species overlap in the field and the potential thus appears to exist for natural predation to occur.  Although Aurelia is known to be an important predator on herring larvae in the Baltic See and other parts of Europe (see Research Study to follow), this appears to be the first documentation for British Columbian waters. Arai & Hay 1982 Can J Fish Aquat Sci 39: 1537.

NOTE  even the tiniest Aurelia are capable of preying on larval fishes, as shown by the accompanying drawing.  The author does not identify the species of fish eaten, but it is probably a larval herring. Fraser 1969 Fish Res Bd Can 26: 1743.

NOTE  although described in the publication as A. aurita, based on more recent taxonomic information, it is more likely to have been the endemic west-coast species A. labiata

  black dot
Research study 2
 

graph comparing predation rates of adult jellyfishes Aurelia aurita on larval herring in the dark and in the lightConcern over the impact that jellyfish predation may be having on commercial fish stocks prompts a laboratory investigation of predation by Aurelia (aurita) labiata on larval herring Clupea harengus.  Although the experiments are done in Scotland, the species are common to the west coast and the studies deserve mention here.  The authors develop a mathematical model to describe the feeding relationship that includes rate of encounter and capture efficiency, the latter a product of density of prey and volume swept by the tentacles.  Rate of encounter takes into account the relative velocities of predator and prey.  Athough the fit of predicted to actual predation rates is quite good (see graph), the authors comment on its discrepancies.  The first is that actual predation in relation to size of predator is somewhat higher than predicted by the mathematical model, especially for intermediate-sized medusae. Also, a greater number of larval fishes are captured at low prey densities than predicted by the model (data not shown here).  The authors note that a feature of the predator’s behaviour may help to explain this.  Apparently, the medusae change from initial slow swimming speeds to faster speeds after capture of their first prey, to slow speeds once again as more prey are consumed.  In nature, this change in swimming pattern may serve to keep medusae in a patch of prey.  Satiation is also is evident once a medusa has consumed sufficient larvae to fill its gastrovascular cavity.  The authors discuss other factors that might influence the predictive usefulness of their model.  In documenting killing frequencies of up to 7 larvae per hour, the authors underscore the importance of A. (aurita) labiata as a potential predator of fish larvae.  Bailey & Batty 1983 Mar Biol 72: 295; see also Bailey & Batty 1984 Mar Biol 83: 287 for more such studies done in Scotland.

  black dot
Research study 3
 

photograph of jellyfish Phacellophora camtschatica courtesy Dave Cowles, Walla Walla U, Washington
In Saanich Inlet, British Columbia the jellyfish Phacellophora camtschatica appears to eat mainly other jellyfishes, such as Aurelia labiata, and several species of hydromedusae. Strand & Hamner 1988 Mar Biol 99: 409. Photo courtesy Dave Cowles, Walla Walla U, Washington rosario.wallawalla.edu.

 



 

Jellyfish Phacellophora camtschatica 0.2X

 
Research study 4
 

schematic showing power and recovery strokes in swimming/feeding jellyfish Aurelia auritaPredation by jellyfishes Aurelia aurita is usually described as them feeding on whatever types of zooplankton are available with no prey selectivity.  By use of video to record body and water motions, researchers at Providence, Rhode Island show that adult A. aurita create fluid motions during swimming that entrain prey and bring them into contact with the tentacles. The authors find that prey with escape speeds slower than the flow velocities at their bell margins, such as barnacle nauplii and slow-swimming hydromedusae, will be captured, while ones with faster escape speeds, such as larger copepods, will not be captured.  Swimming in Aurelia is divided into power stroke and recovery stroke.  During the power stroke, shown in phases 1-3 in the drawing on the Left, water is forced out of the bell cavity (subumbrella space) as a propulsive jet. As the bell expands during the recovery stroke (phases 4-6), water adjacent to the jellfish rushes into the subumbrella space and carries potential prey into the tentacles.  Most prey are captured during this phase of the swimming cycle.

drawing showing currents and vortices created around the bell of a swimming/feeding jellyfish Aurelia auritaBecause the inward-flowing water velocities generated during swimming are a function of bell diameter, larger jellyfishes will capture faster-swimming copepods, and dietary preferences will correspondingly change with size of individual.  As the medusa moves ahead, a “bow wave” is created that reduces pressure near the bell margin and causes water to flow around the bell (see drawing on Right). Vortices are shed at the bell margin resulting in a turbulent wake behind the swimming medusa.  Particles within this flow are accelerated around the bell margin, get caught up in these vortices, and do not enter the subumbrella cavity. Note that arrow lengths in the drawing correspond to velocity.  Costello & Colin 1994 Mar Biol 121: 327.

NOTE  this species is not found on the west coast, but the study is interesting and likely applicable to the local species Aurelia labiata

NOTE  movements of water are tracked by use of fluorescent dyes injected into the paths of moving medusae

 
 

CLICK HERE to see a video of Aureia labiata swimming.

NOTE the video replays automatically

 
Research study 5
 

photograph of a jellyfish Aurelia auritaIn Narragansett Bay, Rhode Island, prey selection by jellyfishes Aurelia aurita varies with age.  Young individuals (<12mm diameter) consume mostly hydromedusae, while older ones eat mostly copepods.   However, a comparison of what is available with what is consumed indicates that the larger medusae are preferentially preying on barnacle nauplii and hydromedusae, as well as copepods.  Sullivan et al. 1994 Mar Biol 121: 335.

NOTE investigations in Corpus Christi, Texas additionally demonstrate that the scyphistomae of Aurelia aurita are able to take up amino acids directly from seawater.  In fact, a tendency to reduce the rate of strobilation when starved can be offset by exposing the polyps to glycine or alanine during the starvation period. The studies are in part done using a clonal culture of scyphistomae begun with a single individual polyp over a decade earlier.  In laboratory culture the polyps are fed nauplii of brine shrimp Artemia salina. Shick 1973 Biol Bull 144: 172;  Shick 1975 Biol Bull 148: 117.

 

Shown here, the moon jelly Aurelia labiata 0.5X

 
Research study 6
 

graph showing change in daily body mass in ephyrae of different sizes of Aurelia auritaIf provided food in excess, the ephyrae of Aurelia aurita can increase in size by an average of 35% per day over a 10-d period (at 18oC), and development to the medusa stage can be quick. Through the ephyra stage, growth tends to be more in diameter than in mass.The authors provide extensive data on growth at different temperatures, salinities, and rations, not included here.  They note that although food concentrations as provided in their experiments would rarely occur in the natural environment, it is clear that A. aurita is especially well adapted to exploit prey patches and utilise the high food intake efficiently for growth.  Båmstedt et al. 1999 Mar Biol 135: 89.

NOTE  nauplii of brine shrimp Artemia salina at densities of about 200 . liter-1

 
Research study 7
 

Observations in Norway show that 2mm-dia ephyrae of Aurelia aurita can capture and feed on phytoplankton, copepods, and suspended particulate organic matter.  Båmstedt et al. 2001 Mar Biol 139: 641.

 
Research study 8
 

histograms of dietary compostion of jellyfishes Aurelia aurita and Cyanea capillata in Prince William Sound, AlaskaThe summer diets of scyphozoans Aurelia labiata and Cyanea capillata in Prince William Sound, Alaska comprise a variety of zooplankton species.  The former species eats primarily small copepods, while the latter species eats mainly larvaceans.  Purcell & Sturdevant 2001 Mar Ecol Progr Ser 210: 67. Photograph
courtesy Dan Leus, DFO, Nanaimo, British Columbia.
photograph of jellyfish Cyanea capillata courtesy Dan Leus, DFO, Nanaimo, B.C.

NOTE  the main purpose of the study is to assess the degree of dietary overlap among zooplanktivorous jellyfish and juvenile fishes (walleye pollock, sandlance, herring, and pink salmon), which the authors estimate to be about 50%.  With this degree of overlap in diets the authors conclude that the potential for competition for prey exists for these zooplanktivores

 

Jellyfish Cyanea capillata 0.3X

 
Research study 9
 

photograph of jellyfish Aurelia labiata
Another study provides further information on zooplanktivory in scyphozoan medusae Cyanea capillata and Aurelia labiata.  Main dietary items of these species, as noted in Research Study 6 above, are copepods, larvaceans, and cladocerans, but also include a few fish eggs and larvae.  Numbers of main prey taxa eaten are correlated both with medusa size and prey density.  Digestion rates for both species of jellyfish range from 1.5-3h depending on the type of prey.  From data obtained, the author considers the overall effects of predation by the jellyfishes to be low, less than 8% of standing stock per day.  The author remarks that in view of this, predation by medusae would likely not significantly reduce copepod availability to juvenile sandlance, herring, and walleye pollock, but may affect larvacean availability to juvenile pink salmon.  Purcell 2003 Mar Ecol Progr Ser 246: 137. Photo courtesy Dave Cowles, Walla Walla University, Washington rosario.wallawalla.edu

 

 

Jellyfish Aurelia labiata 0.5X. Until recently, A. labiata
on the west coast were thought to be A. aurita.

 
Research study 10
 

photographs of ephyrae of moon jellies Aurelia labiata courtesy Widmer 2005 J Mar Biol Ass UK 85: 569 and the Monterey Bay AquariumA study on temperature effects on growth of newly released ephyrae of moon jellies Aurelia labiata at the Monterey Bay Aquarium shows that the optimum temperature range for rearing is 12-21oC over a 14-d culture period.  At temperatures below this, growth is slow or body size may even decrease; at higher temperatures the ephyrae evert their bells (see photograph) and are unable to feed or swim effectively.  The paper will be of interest to aquarists who wish to set up in-house jellyfish cultures for display purposes. Widmer 2005 J Mar Biol Ass UK 85: 569. Photographs courtesy the author and Monterey Bay Aquarium.

NOTE  food in culture consists of brine-shrimp Artemia sp. nauplii

 
Research study 11
 

pie diagrams comparing diets of 2 jellyfishes Chrysaora and Aurelia in OregonThere is growing concern by scientists over jellyfishes, most notably their enormous blooms, and large individual sizes and appetites.  A study by researchers at the Hatfield Marine Science Center, Oregon discloses overlap in diet between several species of  pelagic fishes and the large jellyfishes Chrysaora fuscescens and Aurelia labiata off the coast of southern Oregon. The data show a high preference by both jellyfish species for euphausid eggs and larvae (see pie diagrams), also a favourite of several “silverside”-type fishes.  Overall, the jellyfish diets significantly overlap the diets of herrings, sauries, anchovies, and sardines by 60-74%.  Dietary overlap with 2 species of smelts ranges from 14-22%, but there is little similarity with diets of jack mackerel and 2 species of juvenile salmon (<1%). The occupation of a similar trophic level by the two groups of organisms suggests the potential for competition between them.  Brodeur et al. 2008 Mar Biol 154: 649. 

 
Research study 12
 

photograph of jellyfish Chrysaora fuscescens courtesy Kevin LeeA companion paper to the one above done by researchers based in Newport, Oregon provides further information on invertebrate prey eaten by 3 large jellyfish species Chrysaora fuscescens, Aurelia labiata, and Phacellophora camtschatica off the coast of Oregon.  The main dietary items of all 3 species in this area of rich upwelling are eggs and early developmental stages of euphausiids, and some gelatinous and crustacean species. The picture that emerges is that these jellyfish species are opportunistic predators, but with some preferences, that photograph of jellyfish Phacellophora camtschatica courtesy Kevin Lee, Fullerton, Californiawhen abundant are capable of removing a large portion or even much of the standing stock of a given food taxon over a relatively short period.  Digestion times measured by the researchers for Chrysaora fuscescens range from 2-4h for gelatinous prey and from 4-6h for crustacean, molluscan, and polychaete prey.  Given the importance of euphausiids in the diets of many fish species in particular, and to the ocean ecosystem in general, the authors suggest that more attention be paid to the role of jellyfishes in fisheries management and ecosystem models.  However, as witness the burgeoning number of research papers on jellyfishes, including the authors’ own fine contributions, this is a message that is being received loud and clear.  Suchman et al. 2008 Mar Ecol Progr Ser 358: 161. Photographs courtesy Kevin Lee, Fullerton, California diverkevin.

NOTE  gelatinous prey consists mostly of larvaceans, but also ctenophores, hydromedusae, salps, doliolids, and siphonophores

 

Jellyfishes, Chrysaora fuscescens (above Left) in the company of
several "medusa-fishes" 0.15X; and Phacellophora camtschatica (Right)
with a few parasitic goose-barnacles growing on top of its bell (0.15X)

 
Research study 13
 

photograph of Aurelia jellyfish with feeding features labeledIt is commonly thought that jellyfishes eat only live prey.  However, as part of other experiments with medusae of Aurelia labiata in Roscoe Bay, British Columbia, a researcher shows that this species will readily consume oat bran, oatmeal, 8-grain cereal, peas, and couscous, as well as canned crab and shrimp meats.  Even white paper scraps are ingested, so there seems to be little selectivity.  Is all this stuff digested?  The author follows the post-capture fates of these materials and notes that all are picked from the bell margin by the oral arms, ingested, transported to the stomach, and moved into the gastric pouches within 30min or so.  The extent of digestion of the various foodstuffs, however, is not known.  Albert 2014 Hydrobiologia 736: 61.

 
  RETURN TO TOP