Pleurobrachia bachei

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Geographic Range

Sea gooseberries are among the most common comb jellies found in the northern Pacific Ocean. During spring and summer months, vast numbers of them appear in coastal waters stretching from Friday Harbor, Washington to La Jolla Bay, California. There are also reports of this species from as far north as Alaska and as far south as Acapulco, Mexico; recent research has documented them off the coast of Mejillones, Chile. They are considered native to the coast of Ireland as well, being found in Galway Bay, specifically. (Bishop, 1968; Cowles and Cowles, 2007; Haddock and Case, 1995; Hirota, 1974; Mills, 2013; Moriarty, 2009; Pavez, et al., 2006)

Habitat

Sea gooseberries thrive in pelagic zones and are most commonly seen at depths of 15-30 meters from the surface. They are typically found 5-10 kilometers from shore. Diel migration is a typical behavior among sea gooseberries, allowing vertical movement within the epipelagic and mesopelagic layers, as deep as 1000 meters. Sea gooseberries seem to prefer more temperate waters and are strictly marine. (Hirota, 1974; Mills, 2013; Pavez, et al., 2006)

  • Range depth
    0 to 1000 m
    0.00 to 3280.84 ft
  • Average depth
    20 m
    65.62 ft

Physical Description

Sea gooseberries are elliptical in shape with two long tentacles protruding from each side. These tentacles often measure up to 15 cm in length and, when the animal is not swimming, they hang downward. Several sticky branches lie along each tentacle. Eight comb rows, comprised of fused cilia, run nearly the entire length of the body, from the mouth to the opening at the opposite end of the body. These combs are responsible for propulsion via a beating mechanism and also bend, refracting light and giving the illusion of bioluminescence. Sea gooseberries are colorless or transparent; their tentacles and organs, however, may be colored (most often pink, white, yellow, or orange-brown) and they often have a purple blotch near the pharynx. They grow up to 1.5 cm in diameter, with a slightly greater length. (Haddock, 2007; Cowles and Cowles, 2007; Haddock and Case, 1995; Haddock, 2007)

  • Sexual Dimorphism
  • sexes alike
  • Average length
    2 cm
    0.79 in

Development

Sea gooseberries are monomorphic. Eggs develop significantly more quickly (on average 10-15 days) in warmer waters than cooler (20°C versus 15°C, respectively), but mortality rates are also higher in warmer waters. Embryos grow into pelagic cydippid larvae; they do not undergo metamorphosis, as larvae in this stage resemble the adult form. Larvae have been estimated to grow anywhere from 1.5-6.5 mm in 30 days. (Brusca and Brusca, 2003; Hirota, 1974; Lotterhos, et al., 2010)

Reproduction

Sea gooseberries are hermaphrodites and fertilization occurs externally. Gonadal tissues are located under the comb rows and eggs and sperm are released from the mouth. Sperm is released in pulses for approximately 5 minutes; egg release follows in bursts for 5 to 10 minutes. In lab settings, egg release has been associated with an abundant food source, although results are not conclusive. Successful spawning often depends on several factors, including the viscosity of the spawned material and the flow of the surrounding water. (Brusca and Brusca, 2003; Cowles and Cowles, 2007; Lotterhos, et al., 2010; Pavez, et al., 2006)

Sea gooseberries are hermaphroditic and spawn throughout their lifetimes. The greatest populations of these animals are seen during spring and summer months and there is typically a large drop in population size during the winter. The reasons are unknown but possible influences include water temperature and predation. Time to hatching is dependent on water temperature; at 15°C, eggs hatch within 24 hours. Populations typically double in cycles of 25-35 days. (Hirota, 1974; Lotterhos, et al., 2010)

  • Breeding interval
    Sea gooseberries spawn throughout their lifetimes.
  • Breeding season
    Breeding seems to be most common during spring and summer months.
  • Average gestation period
    24 hours

This species exhibits no parental investment beyond production of gametes. (Lotterhos, et al., 2010)

  • Parental Investment
  • no parental involvement

Lifespan/Longevity

The lifespan of sea gooseberries typically ranges from 120-180 days during the spring and summer months. During winter months, population sizes decline significantly. ("Pleurobrachia bachei: Sea Gooseberry", 2012)

  • Typical lifespan
    Status: wild
    4 to 6 months

Behavior

Sea gooseberries use their comb rows to create propulsion, which moves them up and down in the water column as they search for food or preferred environmental conditions. These comb jellies are known for their ability to remain still in the water for a relatively long period of time before feeding (rather than just drifting with the water current). In order to capture prey, a sea gooseberry moves horizontally in a semi-circle, allowing its tentacles, which are covered in colloblasts (cells which produce a sticky substance) to dangle from its body. It waits with an open mouth until prey is caught in its tentacles and then retracts them while moving forward, rotating its body around and bringing the prey in. Diel migration has been reported; these animals are likely following the migration of their prey. Sea gooseberries are active during the day and night but are mostly observed, near the water surface, at night. They are often found in large groups, particularly during spring and summer months. These comb jellies, unlike many ctenophores, are not bioluminescent, despite previous reports to the contrary. (Brusca and Brusca, 2003; Cowles and Cowles, 2007; Haddock and Case, 1995; Haddock, 2007; Hirota, 1974)

Home Range

These animals are typically found within 5 km of shore but are not known to have a specific home range or defend a territory. (Bishop, 1968; Hirota, 1974)

Communication and Perception

Intracelluar and extracellular recordings have been taken from the comb rows of a closely related species, Pluerobrachia pileus. These recordings show that electrical potentials arise in the animal's cilia, and are triggered by prey activity. An ectodermal nerve net, similar to that of cnidarians, seems to be responsible for the detection of prey. Movements toward or away from prey or predators, respectively, depend on depolarization levels. Sea gooseberries also have an apical sense organ which is responsible for maintaining balance and orientation. (Brusca and Brusca, 2003; Moss and Tamm, 1993)

Food Habits

Sea gooseberries seem to follow the diel migration of their prey, and diet is somewhat controlled by time of day and location in the water column. These comb jellies feed on plankton and small animals including larval fish, other eggs, and copepods. Specific known prey includes Acartia clausii, Acartia tonsa, Calanus pacificus, Pseudevadne tergestina, Evadne nordmanni, Evadne spinifera, Labidocera trispinosa, Penilia avirostris, Pseudocalanus spp., and Sagitta euneritice. (Bishop, 1968; Greene, et al., 1986; Haddock, 2007; Hirota, 1974)

  • Primary Diet
  • carnivore
    • eats eggs
    • eats non-insect arthropods
    • eats other marine invertebrates
  • planktivore
  • Animal Foods
  • eggs
  • aquatic crustaceans
  • other marine invertebrates
  • zooplankton

Predation

Sea gooseberries have little protection against predators. If a predator is detected, they may reverse the direction of their cilial motion, sending them away from danger. Other, larger comb jellies are known to eat this species, as are moon jellies. (Greene, et al., 1986; Haddock, 2007)

  • Known Predators

Ecosystem Roles

Sea gooseberries are important intermediate consumers in marine ecosystems. During the periods of spring algal blooms, the areas occupied by this species often contain a vast abundance of phtyoplankton and zooplankton, which they consume and help to control. They are also a primary consumer of copepods, and research suggests that they may play a major role in balancing phytoplankton ecosystems by regulating copepod populations. They may be hosts to amphipods; the population cycles and sizes of these parasites seem to be closely related to that of their hosts. They have also been found with parasitic dinoflagellates. (Brusca, 1970; Cowles and Cowles, 2007; Greene, et al., 1986; Hirota, 1974; Mills and McLean, 1991; Pavez, et al., 2006; Reeve, et al., 1978)

Commensal/Parasitic Species

Economic Importance for Humans: Positive

Sea gooseberries may control populations of copepods, reducing declines in phytoplankton and potentially increasing coastal fish catches. (Bishop, 1968; Greene, et al., 1986; Hirota, 1974)

Economic Importance for Humans: Negative

Due to their selective feeding on copepods, these comb jellies may negatively impact fishing as well, if they reduce the populations of these animals too much. (Chandy and Greene, 1995)

Conservation Status

This species has not been assessed by the IUCN and is not listed as an endangered or threatened species by any agency. (IUCN, 2012)

Contributors

Jeffery Willis (author), Radford University, Joel Hagen (editor), Radford University, Jeremy Wright (editor), University of Michigan-Ann Arbor.

Glossary

Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

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Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

World Map

Palearctic

living in the northern part of the Old World. In otherwords, Europe and Asia and northern Africa.

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carnivore

an animal that mainly eats meat

coastal

the nearshore aquatic habitats near a coast, or shoreline.

colonial

used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.

crepuscular

active at dawn and dusk

detritus

particles of organic material from dead and decomposing organisms. Detritus is the result of the activity of decomposers (organisms that decompose organic material).

diurnal
  1. active during the day, 2. lasting for one day.
electric

uses electric signals to communicate

external fertilization

fertilization takes place outside the female's body

fertilization

union of egg and spermatozoan

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

the area in which the animal is naturally found, the region in which it is endemic.

nocturnal

active during the night

pelagic

An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).

phytoplankton

photosynthetic or plant constituent of plankton; mainly unicellular algae. (Compare to zooplankton.)

planktivore

an animal that mainly eats plankton

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

protandrous

condition of hermaphroditic animals (and plants) in which the male organs and their products appear before the female organs and their products

radial symmetry

a form of body symmetry in which the parts of an animal are arranged concentrically around a central oral/aboral axis and more than one imaginary plane through this axis results in halves that are mirror-images of each other. Examples are cnidarians (Phylum Cnidaria, jellyfish, anemones, and corals).

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

seasonal breeding

breeding is confined to a particular season

semelparous

offspring are all produced in a single group (litter, clutch, etc.), after which the parent usually dies. Semelparous organisms often only live through a single season/year (or other periodic change in conditions) but may live for many seasons. In both cases reproduction occurs as a single investment of energy in offspring, with no future chance for investment in reproduction.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

zooplankton

animal constituent of plankton; mainly small crustaceans and fish larvae. (Compare to phytoplankton.)

References

2012. "Pleurobrachia bachei: Sea Gooseberry" (On-line). Encyclopedia of Life. Accessed March 05, 2013 at http://eol.org/pages/393303/overview.

Bishop, J. 1968. A comparative study of feeding rates of tentaculative ctenophores. Ecology, 49/5: 996-997.

Brusca, G. 1970. Notes on the association between Hyperoche medusarum A. Agassiz (Amphipoda, Hyperiidea) and the ctenophore, Pleurobrachia bachei (Muller). Bulletin of the Southern California Academy of Sciences, 69/3-4: 179-181. Accessed March 05, 2013 at http://biostor.org/reference/114547.

Brusca, R., G. Brusca. 2003. Invertebrates (2nd Ed.). Sunderland, MA: Sinauer Associates, Inc..

Chandy, S., C. Greene. 1995. Estimating the predatory impact of gelatinous zooplankton. Limnology and Oceanography, 40: 947-955.

Cowles, D., J. Cowles. 2007. "Pleurobrachia bachei (A. Agassiz, 1860)" (On-line). Accessed March 05, 2013 at http://www.wallawalla.edu/academics/departments/biology/rosario/inverts/Ctenophora/Pleurobrachia_bachei.html.

Esser, M., W. Greve, M. Boersma. 2004. Effects of the temperature and the presence of benthic predators on the vertical distribution of the Ctenophore Pleurobrachia pileus. Marine Biology, 145: 595-601.

Greene, C., M. Landry, B. Monger. 1986. Foraging Behavior and Prey Selection by the Ambush Entangling Predator Pleurobrachia Bachei. Ecology, 67/6: 1493-1501.

Haddock, S. 2007. Comparative feeding behavior of planktonic ctenophores. Integrative and Comparative Biology, 47/6: 847–853. Accessed March 05, 2013 at http://icb.oxfordjournals.org/content/47/6/847.full.

Haddock, S., J. Case. 1995. Not all ctenophores are bioluminescent: Pleurobrachia. Biological Bulletin, 189: 356-362. Accessed March 05, 2013 at http://www.lifesci.ucsb.edu/~haddock/abstracts/haddock_pleuro.pdf.

Hirota, J. 1974. Quantitative natural history of Pleurobrachia bachei in La Jolla bight. Fishery Bulletin, 72/2: 295-333. Accessed March 05, 2013 at http://fishbull.noaa.gov/72-2/hirota.pdf.

IUCN, 2012. "The IUCN Red List of Threatened Species" (On-line). Accessed March 05, 2013 at http://www.iucnredlist.org/search.

Lotterhos, K., D. Levitan, J. Leonard, A. Cordoba-Aguilar. 2010. The Evolution of Primary Sexual Characters in Animals. 198 Madison Ave, New York, New York 10016: Oxford University Press, Inc..

Mills, C. 2013. "Pleurobrachia bachei (A. Agassiz, 1860)" (On-line). World Register of Marine Species. Accessed March 05, 2013 at http://www.marinespecies.org/aphia.php?p=taxdetails&id=265191.

Mills, C., N. McLean. 1991. Ectoparasitism by a dinoflagellate (Dinoflagellata: Oodinidae) on 5 ctenophores (Ctenophora) and a hydromedusa (Cnidaria). Diseases of Aquatic Organisms, 10: 211-216. Accessed March 05, 2013 at http://www.int-res.com/articles/dao/10/d010p211.pdf.

Moriarty, M. 2009. "Pleurobrachia bachei (A. Agassiz)" (On-line). Species.ie: The Irish Species Register. Accessed March 05, 2013 at http://www.species.ie/search/species/detail/?species_id=32383&-session=abv4:48E0117C077312A51CxxX167136E.

Moss, A., S. Tamm. 1993. Patterns of electrical activity in comb plates of feeding Pleurobrachia (Ctenophora). Philosophical Transactions: Biological Sciences, 339: 1-16.

Pavez, M., L. Casrto, H. Gonzalez. 2006. Across-shelf predatory effect of Pleurobrachia bachei(Ctenophora) on the small-copepod community in the coastal upwelling zone off northern Chili. Journal of Plankton Research, 28/2: 115-129.

Reeve, M., M. Walter, T. Ikeda. 1978. Laboratory Studies of Ingestion and Food Utilization in Lobate and Tentaculate ctenophores. Limnology and Oceanography, 23/4: 740-751.

Thuesen, E., L. Rutherford, P. Brommer. 2005. The role of aerobic metabolism and intragel oxygen in hypoxia tolerance of three ctenophores: Pleurobrachia bachei, Bolinopsis infundibulum and Mnemiopsis leidy. Journal of the Marine Biological Association of the United Kingdom, 85: 627-633.