Pleurobrachia bachei

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Pleurobrachia bachei
Pleurobrachia bachei.jpg
Pleurobrachia bachei with its oral end down.
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Ctenophora
Class: Tentaculata
Order: Cydippida
Family: Pleurobrachiidae
Genus: Pleurobrachia
Species:
P. bachei
Binomial name
Pleurobrachia bachei
A. Agassiz, 1860

Pleurobrachia bachei is a member of the phylum Ctenophora and is commonly referred to as the Pacific sea gooseberry. These comb jellies are often mistaken for medusoid Cnidaria, but lack stinging cells.

Contents

Morphology

An individual sea gooseberry's body length can reach up to 20 mm (0.79 in) with each of the two tentacles stretching 150 mm (5.9 in). [1] Their gelatinous globular bodies are composed of 99% water. [2] They have eight rows of well-developed comb plates consisting of thousands of fused macrocilia controlled by an apical organ. Unlike most other ctenophores, Pleurobrachia lacks a conventional photoprotein and is therefore incapable of producing light. [3] Their bodies are virtually transparent and the many cilia refract the light, producing rainbow-like colors that can give the false appearance of bioluminescence. The branched tentacles can be white, yellow, pink or orange. They have no nematocysts (stinging cells). Instead, the two long extensile branched tentacles are armed with colloblasts: specialized adhesive cells with which to ensnare their prey. [4]

Their mitochondrial genome consist of only 12 genes. [5]

Lifespan

The sea gooseberry is only alive for around 4–6 months. [2]

Reproduction

Pleurobrachia lack any sessile (attached) stages and are wholly planktonic in their life cycle. They are self-fertile hermaphrodites [6] that spawn eggs and sperm freely into the sea, and develop thereafter without any parental protection with indirect development. [2]

Feeding

Foraging behavior

Pleurobrachia bachei is a selective carnivore and its feeding habits are analogous to other ambush "sit and wait" predators, such as the orb-weaving spider. When searching for prey the Pleurobrachia swims with its oral pole forward to set its tentacles. To allow the two main tentacles and numerous lateral tentilla to relax and expand behind it they are often in a curved or helical pathway. Once the tentacles are set, the ctenophore drifts passively. Occasionally, it will retract its tentacles to varying degrees into the sheaths before swimming to another location where it then resets them. This behavior appears to be regulated by its hunger level [4] and can be construed as an attempt to find an area with more prey abundance.

When handling prey both tentacles contract and carry the prey to the mouth. This is achieved by several rapid rotations of the body which swipes the tentacle bearing the food across the oral region. The Pleurobrachia has its oral end opposite of where its tentacles originate. [4]

Trophic strategy

Sea gooseberries are insatiable feeders of copepods and other small plankton, rarely fish eggs and larvae. It has been shown that their prey is more susceptible at an early age (naupliar/larval stages) because of minimal swimming speeds and small size which makes handling more efficient. This generalization is not necessarily true for all Pleurobrachia. In one experiment the ctenophore favored adult Pseudocalanus minutus more than other forms of zooplankton. [7]

Ecology and distribution

Geographic range

P. bachei is found along the West coast of North America from Southeast Alaska to Mexico. [2] [8]

Habitat

The sea gooseberry occurs primarily in surface waters of the coastal NW Pacific within 5 km of shore to about 50 m deep, though is usually in the upper 15 m during the day. [6]

Conservation

Conservation status

Pleurobrachia bachei has not been evaluated by the International Union for Conservation of Nature (IUCN), but seems to be prevalent and is not considered threatened. [9]

Economic importance for humans

Negative

Although Pleurobrachia has not been associated with declines in other populations, a closely related species Mnemiopsis leidyi has. This ctenophore had catastrophic effects on fish catches after its introduction into the Black and Azov Seas. It is believed to have been the main cause of decline in these waters after dissection confirmed its stomach contents had large quantities of the local fish eggs and larvae. [10] Because of their diets Pleurobrachia and other ctenophore species can directly or indirectly affect trophic cascades and ultimately regulate yield of commercially important fish stocks.

Positive

As predators, ctenophores have a tremendous capacity to regulate abundance of their prey and therefore help to balance an ecosystem. While they can decimate other populations they can also restrain an overabundance of copepods which, when left to their own devices, could virtually eliminate all phytoplankton from the water column. [4]

Related Research Articles

<span class="mw-page-title-main">Plankton</span> Organisms living in water or air that are drifters on the current or wind

Plankton are the diverse collection of organisms that drift in water but are unable to actively propel themselves against currents. The individual organisms constituting plankton are called plankters. In the ocean, they provide a crucial source of food to many small and large aquatic organisms, such as bivalves, fish, and baleen whales.

<span class="mw-page-title-main">Zooplankton</span> Heterotrophic protistan or metazoan members of the plankton ecosystem

Zooplankton are the animal component of the planktonic community, having to consume other organisms to thrive. Plankton are aquatic organisms that are unable to swim effectively against currents. Consequently, they drift or are carried along by currents in the ocean, or by currents in seas, lakes or rivers.

<span class="mw-page-title-main">Ctenophora</span> Phylum of gelatinous marine animals

Ctenophora comprise a phylum of marine invertebrates, commonly known as comb jellies, that inhabit sea waters worldwide. They are notable for the groups of cilia they use for swimming, and they are the largest animals to swim with the help of cilia.

<i>Aurelia aurita</i> Species of jellyfish

Aurelia aurita is a species of the family Ulmaridae. All species in the genus are very similar, and it is difficult to identify Aurelia medusae without genetic sampling; most of what follows applies equally to all species of the genus.

<span class="mw-page-title-main">Tentaculata</span> Class of comb jellies

Tentaculata is a class of comb jellies, one of two classes in the phylum Ctenophora. The common feature of this class is a pair of long, feathery, contractile tentacles, which can be retracted into specialised ciliated sheaths. In some species, the primary tentacles are reduced and they have smaller, secondary tentacles. The tentacles have colloblasts, which are sticky-tipped cells that trap small prey.

<span class="mw-page-title-main">Beroidae</span> Family of comb jellies without tentacles

Beroidae is a family of ctenophores or comb jellies more commonly referred to as the beroids. It is the only known family within the monotypic order Beroida and the class Nuda. They are distinguished from other comb jellies by the complete absence of tentacles, in both juvenile and adult stages. Species of the family Beroidae are found in all the world's oceans and seas and are free-swimmers that form part of the plankton.

<span class="mw-page-title-main">Lobata</span> Order of comb jellies

Lobata is an order of transparent marine invertebrates belonging to the phylum of Ctenophora in the class Tentaculata, and are commonly referred to as comb jellies or sea gooseberries. There are currently 19 extant known species in the order of Lobata. Members of Lobata exhibit a compressed body in the vertical plane and a pair of oral lobes. They are known to inhabit marine pelagic surfaces and the marine shores.

<i>Aequorea victoria</i> Species of hydrozoan

Aequorea victoria, also sometimes called the crystal jelly, is a bioluminescent hydrozoan jellyfish, or hydromedusa, that is found off the west coast of North America.

<i>Solmissus</i> Genus of hydrozoans

Solmissus, or dinner plate jellyfish, is a genus of hydrozoans. Its species are unique among cnidarians in that they actively hunt for prey as opposed to passively waiting for plankton to pass by. They are found in the deep waters of Monterey Bay, California. They are most likely to be found in the deep sea, mid water. They grow to be 20 cm (7.9 in) in diameter. These hydrozoans feed on gelatinous zooplankton, including salps and doliolids, ctenophores, jellyfish, and copepods. However, Solmissus may be limited to feeding on soft-bodied prey by the type of nematocysts on their tentacles (Mills).

<i>Chrysaora colorata</i> Species of jellyfish

Chrysaora colorata (Russell), commonly known as the purple-striped jelly or purple-striped sea nettle, is a species of jellyfish that exists primarily off the coast of California from Bodega Bay to San Diego. The bell (body) of the jellyfish is up to 70 cm (2.3 ft) in diameter, typically with a radial pattern of stripes. The tentacles vary with the age of the individual, consisting typically of eight marginal long dark arms, and four central frilly oral arms. It is closely studied by scientists due to not much being known about their eating habits. A 15-foot-long specimen has been seen.

<i>Ocyropsis</i>

Ocyropsis is a genus of Ctenophores, which are commonly known as Comb Jellies. Ocyropsis belong to the family of Ocyropsidae. Ocyropsis possesses two large lateral muscular lobes and four auricles, and appear pale and translucent in color. Ocyropsis habitat is not precise as their gelatinous composition can make it difficult to study. They have been found in warm and cold waters. Unlike other, slow swimming Ctenophores, Ocyropsis are efficient in evading their predators. They use their oral lobes for additional propulsion and a secrete luminous mucous in efforts to evade predators. The muscular oral lobes of the Ocyropsis are used to grab its prey, and then moved to the prehensile mouth for absorption.

<span class="mw-page-title-main">Forage fish</span> Small prey fish

Forage fish, also called prey fish or bait fish, are small pelagic fish that feed on plankton and other tiny organisms. They are preyed on by larger predators, including larger fish, seabirds and marine mammals. Typical ocean forage fish feed near the base of the food chain on plankton, often by filter feeding. They include particularly fishes of the order Clupeiformes, but also other small fish, including halfbeaks, silversides, smelt such as capelin and goldband fusiliers.

<span class="mw-page-title-main">Cydippida</span> Order of comb jellies with retractable branched tentacles

Cydippida is an order of comb jellies. They are distinguished from other comb jellies by their spherical or oval bodies, and the fact their tentacles are branched, and can be retracted into pouches on either side of the pharynx. The order is not monophyletic, that is, more than one common ancestor is believed to exist.

<i>Mertensia ovum</i> Species of comb jelly

Mertensia ovum, also known as the Arctic comb jelly or sea nut, is a cydippid comb jelly or ctenophore first described as Beroe ovum by Johan Christian Fabricius in 1780. It is the only species in the genus Mertensia. Unusually among ctenophores, which normally prefer warmer waters, it is found in the Arctic and adjacent polar seas, mostly in surface waters down to 50 metres (160 ft).

<span class="mw-page-title-main">Benthic comb jelly</span> Comb jelly found in the Ryukyu Trench near Japan

The benthic comb jelly is a comb jelly living in the Ryukyu Trench near Japan. Found at a depth of 7,217 metres (23,700 ft), it is the deepest dwelling ctenophore discovered. Since its discovery, similar comb jellies have been found in the New Britain and Yap trenches.

<span class="mw-page-title-main">Planktivore</span> Aquatic organism that feeds on planktonic food

A planktivore is an aquatic organism that feeds on planktonic food, including zooplankton and phytoplankton. Planktivorous organisms encompass a range of some of the planet's smallest to largest multicellular animals in both the present day and in the past billion years; basking sharks and copepods are just two examples of giant and microscopic organisms that feed upon plankton.

<i>Beroe ovata</i> Species of comb jelly

Beroe ovata is a comb jelly in the family Beroidae. It is found in the South Atlantic Ocean and the Mediterranean Sea and has been introduced into the Black Sea, the Aegean Sea, the Sea of Azov and the Caspian Sea. It was first described by the French physician and zoologist Jean Guillaume Bruguière in 1789.

<i>Bolinopsis infundibulum</i> Species of comb jelly

Bolinopsis infundibulum, commonly known as the common northern comb jelly, is a species of comb jelly in the family Bolinopsidae. It is found in the northern Atlantic Ocean and was first described by the Danish naturalist Otto Friedrich Müller in 1776.

<i>Pleurobrachia pileus</i> Species of comb jelly

Pleurobrachia pileus is a species of comb jelly, commonly known as a sea gooseberry. It is found in open water in the northern Atlantic Ocean, the North Sea, the Baltic Sea and the Black Sea, and was first described by the Danish zoologist Otto Friedrich Müller in 1776.

<i>Euplokamis</i> Genus of ctenophores

Euplokamis is a genus of ctenophores, or comb jellies, belonging to the monotypic family Euplokamididae. It shares the common name sea gooseberry with species of the genus Pleurobrachia. Despite living for hundreds of millions of years in marine environments, there is minimal research regarding Euplokamis, because they are uncommon. Research on the evolution of the basic body structures of diploblastic metazoans revealed that there are four major phyla, including the Ctenophores. Although the morphology of Euplokamis often resembles the medusa stage of Cnidarians, their eight rows of combs are one distinguishing feature that led to the official classification of Ctenophores. After being originally described by Chun (1879), the family Euplokamididae was expanded by Mills (1987) due to the discovery of a new species, Euplokamis dunlapae. Further research indicated that Euplokamis should be identified from Mertensiidae due to the rows of combs and some compression. They may also be distinguished from the genus Pleurobrachia due to their more elongated shape. Additionally, various adaptations of Euplokamis have been observed such as the use of tentacles for movement/feeding, a complex nervous system, and bioluminescent capabilities. Other characteristics including a defined mesoderm, lack of stinging cells, developmental differences, and symmetry supported the reclassification of these organisms.

References

  1. Hanby, Andy Lamb and Bernard P. Hanby ; seaweed and annelid worm sections in collaboration with Michael W. Hawkes and Sheila C. Byers respectively ; photography by Bernard P. (2005). Marine life of the Pacific Northwest : a photographic encyclopedia of invertebrates, seaweeds and selected fishes . Madeira Park, BC: Harbour Pub. ISBN   978-1550173611.{{cite book}}: CS1 maint: multiple names: authors list (link)
  2. 1 2 3 4 "Sea gooseberry". The Blue Planet. BBC. Archived from the original on 2010-10-18.
  3. Haddock, SHD; Case, JF (1995). "Not all ctenophores are bioluminescent: Pleurobrachia". The Biological Bulletin. 189 (3): 356–362. doi:10.2307/1542153. JSTOR   1542153. PMID   29244577.
  4. 1 2 3 4 Greene, Charles H; Landry, Michael R; Monger, Bruce C (December 1986). "Foraging behavior and prey selection by the ambush entangling predator Pleurobrachia bachei". Ecology. 67 (6): 1493–1501. doi:10.2307/1939080. JSTOR   1939080.
  5. Kohn, A. B.; Citarella, M. R.; Kocot, K. M.; Bobkova, Y. V.; Halanych, K. M.; Moroz, L. L. (2011). "Rapid evolution of the compact and unusual mitochondrial genome in the ctenophore, Pleurobrachia bachei". Molecular Phylogenetics and Evolution. 63 (1): 203–207. doi:10.1016/j.ympev.2011.12.009. PMC   4024468 . PMID   22201557.
  6. 1 2 Hirota, J. 1974. Quantitative natural history of Pleurobrachia bachei in La Jolla Bight. Fishery Bulletin 72: 295-335.
  7. Bishop, John W (September 1968). "A Comparative Study of Feeding Rates of Tentaculate Ctenophores". Ecology. 49 (5): 996–997. doi:10.2307/1936552. JSTOR   1936552.
  8. Wrobel, D. and C. Mills, 1998. Pacific Coast Pelagic Invertebrates: a Guide to the Common Gelatinous Animals. Sea Challengers and the Monterey Bay Aquarium, Monterey, California, iv plus 108 pages.
  9. Bishop, John W. (1968). "Sea Gooseberry (Pleurobrachia bachei)". Encyclopedia of Life. 49 (5). EOL: 996–997. JSTOR   1936552.
  10. Chandy, Shonali T; Greene, Charles H (1995). "Estimating the predatory impact of gelatinous zooplankton" (PDF). Limnology and Oceanography. 40 (5): 947–955. Bibcode:1995LimOc..40..947C. doi:10.4319/lo.1995.40.5.0947. Archived from the original (PDF) on 2012-02-13. Retrieved 2012-04-22.