Sea Walnut Comb Jelly: A New World Native That Has the Old World by its Tentacles

Mnemiopsis leidyi is commonly known as sea walnut comb jelly or as warty comb jelly. Other scientific synonyms include Mnemiopsis gardeni and Mnemiopsis mccradyi.

Its genus name, Mnemiopsis, is derived from two Greek words, Μνήμη, mneme, “memory”, and ὄψις, opsis, “act of seeing, sense of sight”, which, in combination, usually are translated as meaning "unforgettable sight." And, indeed, especially in the dark, sea walnuts are unforgettable.

Renowned scientist Alexander Agassiz (December 17, 1835-March 27, 1910) selected its species epithet, leidyi, to honor Joseph Leidy (September 9, 1823-April 30, 1891), a physician, vertebrate paleontolgist, and naturalist from Philadelphia, Pennsylvania. Dr. Leidy studied marine invertebrates along the coasts of Rhode Island and New Jersey. President of the Academy of Natural Sciences of Philadelphia for the last eight years of his life, Joseph Leidy published more than 800 scientific papers in his lifetime.

What is a sea walnut?

A sea walnut is a sea dweller in the genus Ctenophora (Greek χτένα, khtena, "comb" + φέρω, pherō, "carry"). Ctenophores characteristically have cilia, or bristles, which are grouped in four double combs, or rows. Movement of the ciliated combs serves to propel the lobed body of the sea walnut through its watery world. Because of their transparency and their distinctive combs, ctenophores are popularly referred to as comb jellies.

With water comprising over 95 percent of their body, sea walnuts often delicately disintegrate upon capture and removal from water. Soon after contact with air the only remnants are comb sections with the cilia still beating.

Another feature of sea walnuts is their ability to regenerate as long as each fragment represents at least one-fourth of the entire body.

Their common name of sea walnut derives from the resemblance of their bodies to a walnut (genus Juglans) both in size and in shape.

Native distribution: prehistoric New World native

The sea walnut is a New World prehistoric native which hugs the western Atlantic Ocean from subtropical southern Argentina in South America northward to temperate Massachusetts in North America. Its domain largely is demarcated by the Valdes Peninsula (Península Valdés), at 42° 30′ South latitude, 63° 56′ West longitude, to the south and by Cape Cod, at 41° 41′ 20″ North latitude, 70° 17′ 49″ West longitude, to the north.

Habitat: sunlit, salty waters

Sea walnuts live in the ocean's photic (Greek: φῶς, phos, "light"), or sunlit, region, which is the topmost horizontal layer where the energy of sunlight converts carbon dioxide into organic compounds through the chemical process of photosynthesis (Greek: φώτο-, photo-, "light," + σύνθεσις, synthesis, "putting together").

The sea walnut's sunlit, marine habitat encompasses both the bountiful littoral (Latin: litus, "beach, shore") zone and the teeming pelagic (Greek: πέλαγος, pélagos, "open sea") zone. Thus, sea walnuts, not being bottom dwellers, are not found in either the benthic (Greek: βένθος, benthos, "depths of the sea") or the demersal (Latin: demergere, "to dip, sink") zones, the two bottommost layers of the deep ocean's aphotic (Greek: prefix ἀ-, a-, "without" + φῶς, phos, "light") zone.

Despite the seeming fragile collapsibility of their appearance, sea walnuts are adaptable, stalwart marine denizens. They do not have a narrowly defined ecology. Their euryoecious (Greek: ευρυς, eurys, "wide" + οἰκία, oikia, “house, dwelling”) nature allows them to tolerate a variety of environmental conditions and habitats.

euryhaline: Sea walnuts are euryhaline (Greek: ευρυς, eurys, "wide" + ἅλς, hals, "salt"), meaning that they are not intimidated by varying levels of salinity. Sea walnuts tolerate salinity levels as low as 3.4 and as high as 75.

eurythermic: As eurytherms (Greek: ευρυς, eurys, "wide" + θέρμη, thermē, "heat"), sea walnuts survive in a wide range of temperatures, from 36° to 90° Fahrenheit (2° to 32° Celsius).

hypoxic: Sea walnuts are not distressed by hypoxia (Greek: ὑπό, hypó, “under”), "under" + , ὀξύς, oxys, "sharp"), which is inadequately low or reduced levels of oxygen.

As a product of the marine (Latin: mare, "sea") environment, sea walnuts are saltwater organisms. Nevertheless, they are not restricted to salty waters. Sea walnuts thrive in brackish (Dutch: brak, "salty") waters, a mixture of fresh water with the sea's saline waters. Estuaries (Latin: aestus, "tide, boiling [of the sea]"), which are partly enclosed, river- or stream-fed coastal bodies of water with influxes of saline water from the open sea, transition from fresh water to brackish water to salt water. An estuary favored by sea walnuts is the Chesapeake Bay. The largest estuary in the eastern United States, the Bay covers a drainage basin of 64,299 square miles (166,534 square kilometers) touching Washington, D.C., and six mid-Atlantic states (Delaware, Maryland, New York, Pennsylvania, Virginia, West Virginia).

Externals: What sea walnuts look like

Sea walnuts have a length ranging from 3 to 5 inches (7 to 12 centimeters). Their width usually halves their length.

Two lobes open at one end to form a mouth, which in turn segues into a flattened, elongated pharynx. A small esphagus links the pharynx with the stomach funnel. Canals branch off from the stomach, running from there throughout the body. At the aboral pole, which is the end opposite from the oral pole of the mouth, canals open to the outside through anal pores.

Two main feeding tentacles, which are retractable into pouches, are each located laterally on opposite sides of the body. Embedded in the tentacles are colloblasts (Greek: κόλλα, kolla, “glue” + βλαστός, blastos, "bud, sprout"), which are specialized lasso cells for ensnaring prey. Two filaments protrude from each cell. One straight filament is paired with a spiraled filament. Both are topped with a granular head from which a sticky substance is secreted that adheres to their prey, which are then transported to the sea walnut's mouth.

Bristly cilia (Latin: cilium, "eyelid, eyelash"), which are hairlike cellular projections, are arranged in double-tiered rows known as combs because of the overall resemblance to fine-tooth combs. Coordinated movement of these cilia propel sea walnuts through their watery world. Sea walnuts primarily move with their mouth forward and open.

Sea walnuts and other comb jellies are favorite photographic subjects. As light is diffracted between the cilia, the iridescence of the combs sparkles and shimmers against the transparent body.

Also sea walnuts appear magically in the nighttime waters as they bioluminesce, or glow blue-green, in the darkness, especially when disturbed, for example, by choppy waves roiling the watery world or by canoe paddles slapping reverberations nearby.

Continuity of the species: reproduction

As a simultaneous hermaphrodite, each sea walnut exhibits both male and female reproductive organs. Reproduction is achieved efficiently by self-fertilization. Eggs, which usually average 2,000 to 3,000 per day, are spawned (Latin: expandere, "spread out"), or shed, into the water. Spawning, which requires plentiful food and water temperature between 66.2° to 73.4° Fahrenheit (19° to 23° Celsius), is only triggered at night. Fertilization takes place externally in the aqueous environment.

Within only twenty hours of fertilization, a sea walnut embryo is fully developed.

Thirteen days after hatching, a sea walnut is able to reproduce.

A sea walnut's lifespan ranges from several months to one year.

Sea walnut flaws: running amok and going hog wild

In the presence of abundant food, sea walnuts are intemperately enthusiastic. They do not observe satiety, or fullness, in a feast. As long as food is accessible, sea walnuts are able to keep consuming by way of a flow-through digestion system which has three distinct, consecutive phases. In this way, prey items are treated simultaneously in each phase. Apart from a small area of overlap, consumption and elimination occur along separate pathways. Food enters in the center of the mouth, and large indigestible fragments are ejected in the corners of the mouth. Digestive waste is excreted through the anal pores. Thus, consumption, digestion, and elimination can occur simultaneously.

Sustenance: no specific food preferences

As generalized feeders, sea walnuts consume an array of organisms in their aquatic environment, from fish eggs and larvae to zooplankton (Greek: ζῴον, zoon, "animal" + πλαγκτος, planktos, "wanderer, drifter"), which are tiny animals in the first link of the marine food chain. Zooplanktonic prey include fellow marine invertebrates, such as:

*** younger sea walnuts,

*** cnidarians (Greek: κνίδη, knide, "nettle"), which characteristically have cells for stinging their prey and a single opening for both consuming food and eliminating wastes, and

*** crustaceans (Latin: crusta, "crust"), which have an exoskeleton, or external skeleton, segmented body, and jointed limbs.

Sea walnuts regularly consume such crustaceans as:

*** brine shrimp (Artemia salina), with a lifespan of up to one year and an adult length of about 0.5 inches (1 centimeter), and

*** copepods (subclass Copepoda), one-eyed, ubiquitous, with a lifespan of up to two years and an adult length averaging from 0.04 to 0.08 inches (1 to 2 millimetres).

Thus, sea walnuts' primary diet is carnivorous, piscivorous, and zooplanktivorous.

Through aquatic glidings, sea walnuts propel water, which is replete with edible organisms, over their mucous-covered lobes and thereby trap their prey.

Sea walnuts are able to consume prey even after filling their stomach chamber because they simultaneously eject excess food as a ball of mucous.

Sea walnuts tackle famine by reducing their body size, which allows them to survive for up to one month without food.

Trophic synecology: natural predators preying on sea walnuts

Synecology (Greek: σύν, syn, “with” + oικoλoγία, ecologia, “house” + “study”) identifies organisms which regularly coexist with sea walnuts in their native habitats. Persistent cohabitants include not only sea walnuts' prey but also sea walnuts' predators, which is the other aspect of prey-predator trophic (Greek: τροφή, trophē, "food, feeding") levels in the food chain.

Natural predators, whose native waters in eastern North America overlap with sea walnuts' native territory, serve to control this comb jelly's population. Influenced by such factors as dearth of preferred prey, generalized feeders may or may not consume sea walnuts in their vicinity and thus are whimsical predators of uncertain, although unlikely, concern to these comb jellies.

On the other hand, natural predators which specialize in preying upon sea walnuts include:

*** Atlantic butterfish (Peprilus triacanthus), averaging about 6 to 9 inches in length, with a short head, blunt snout, and a coloration of leaden blue, with pale sides dotted with dark irregular spots, and silvery belly;

*** Atlantic sea nettle (Chrysaora quinquecirrha), dome-shaped body, usually white in color, occasionally with radiating bands of pale pink, red-brown, or yellow along their upper surface, and with up to 24 long, thin, trailing tentacles;

*** lion's mane jellyfish (Cyanea capillata), an eight-lobed bell- or dome-shaped body ranging in color from crimson or purple to light orange or tan, with eight clusters of sticky, long, trailing tentacles in bundles of over 100 per cluster, and featured as the killer in "The Adventure of the Lion's Mane" by Sir Arthur Conan Doyle (May 22, 1859–July 7, 1930);

*** spiny dogfish (Squalus acanthias), a small schooling shark with spines in front of both dorsal fins, distinguished by scatterings of small white spots against its slate grey to brown back and light grey to pure white belly; and

*** pink comb jelly (Beroe ovata), a fellow ctenophore with a voracious proclivity for devouring sea walnuts, having a mitten-shaped body with a length of around 4 inches (10.16 centimeters) and a width of 2 inches (5.08 centimeters), and having a milky coloring tinted pink or reddish brown.

Along the U.S. mid-Atlantic coast, these five natural predators are attracted to sea walnuts as prey. Predators and prey cluster in the same marine environments.

Sea walnuts especially thrive in the Chesapeake Bay as well as further north in Rhode Island's Narragansett Bay and in Massachusett's Cape Cod Bay.

Invasive species: discovery of new habitats as stowaways in ballast water

A plant or animal is not necessarily restricted to living and flourishing in its native habitat forever. Relocation may occur over vast expanses. In the waning decades of the twentieth century sea walnuts experienced a considerable, easterly relocation. In their new locations, sea walnuts flourished glaringly and were labeled undesirably as alien invasive species.

The International Union for Conservation of Nature (IUCN), a global organization focused on the conservation of biodiversity and the sustainable, equitable use of natural resources, defines an alien invasive species as a non-native species "which becomes established in natural or semi-natural ecosystems or habitat, is an agent of change, and threatens native biological diversity." Invasive species may be introduced, intentionally or unintentionally, on land or in water.

Introducing invasive, non-native marine plants and animals into different, new environments through ship ballast water poses one of the four greatest threats to the oceanic world. (The other three threats are identified as marine pollution, overexploitation of living marine resources, and physical alteration and/or destruction of marine habitats.) Over 80 percent of the world's commodities are moved by ships. With each tonne equaling 2,204.62 pounds (1,000 kilograms), approximately 10 billion tonnes of ballast water are transferred internationally through shipping each year.

By providing balance and stability to cargoless ships, ballast water is an operational necessity for modern shipping. Unweighted by cargo, a ship flounders. Thus, after a ship's cargo is unloaded, unsteadiness is corrected by opening intake ports and pumps in the hold, which is the area between the bottom of the ship and the lowermost deck. As cargo is loaded, an imbalance of weight is offset by opening discharge valves to release water from the ballast tanks.

Water which is being pumped into the hold contains an abundance of visible and microscopic marine plants and animals. Water which is being discharged from the hold releases its stowaways into a different marine environment. Ballast water transports approximately 7,000 species every day from one part of the globe to another location.

A problem, with an ensuing threat, is presented by species which, acclimating to their new habitat, proliferate excessively due to the absence of the natural predators of their native ecosystem.

Such is the nightmare situation in European and Eurasian seas, where disproportionate, unnatural population excesses of sea walnuts recently have wreaked economic and environmental havoc or potential are poised to create ecological and economic imbalances.

The Black Sea, one of Eurasia's major inland seas, lies well over 6,050 miles (9,735 kilometers; 5,257 nautical miles) to the east of the Chesapeake Bay, where sea walnuts abound natively. Sometime in the early 1980s sea walnuts were unintentionally introduced into the Black Sea, presumably through ship ballast water. The environment in which sea walnuts found themselves was weakened by irregularities in the food chain through overfishing and by compromised water quality through agricultural runoff. Unfettered by the absence of pink comb jellies (Beroe ovata), their natural predators in the Chesapeake Bay, sea walnuts ate their way into top food predator status in the unprepared and overwhelmed food chain.

Feasting on the eggs and young of European anchovies (Engraulis encrasicolus), sea walnuts single-handedly depleted the Black Sea population of this snout-nosed forage fish. Preyed upon by larger fish, European anchovies are critical components of the Black Sea food chain. Additionally, European anchovies are commercially valuable as bait and in fresh, dried, smoked, canned, and frozen commodities to area fishing industries operated by Bulgaria, Georgia, Romania, the Russian Federation, Turkey, and the Ukraine. By 1989 the monopolistic presence of sea walnuts in the Black Sea was estimated at around one billion tonnes, and area fishing industries losses soared into the equivalent of several hundred million dollars.

Their devastating crash of the Black Sea fishery industry qualify sea walnuts within the top 100 of the world's worst invasive species, as determined by the Invasive Species Specialist Group (ISSG). The detrimental impact of sea walnuts on biological diversity and their devastating collapse of fishing industries illustrate critical issues concerning ecological invasion by non-native marine species.

Pink comb jellies: a predator surprises its fugitive prey

A natural solution to the reign of terror by sea walnuts in the Black Sea presented itself with the unintentional introduction of a ferocious predator from the western Atlantic Ocean, pink comb jelly (Beroe ovata). Presumably, these jellies were pumped into ship ballast tanks in eastern North America and discharged beyond the eastern extent of the Atlantic Ocean into this distant inland sea.

As sea walnuts now are spreading throughout European and Eurasian seas, affected countries are reviewing the recent drastic situation in the Black Sea and are considering strategies for confronting the escalating distribution of sea walnuts as they run amok in nonthreatening ecosystems. As a result of the fortuitously accidental invasion of the Black Sea by pink comb jellies, the global strategy is focused largely on biological control by a natural predator.

Biological controls: Atlantic butterfish and spiny dogfish

Atlantic butterfish (Peprilus triacanthus): The First International Meeting on the Invasion of the Caspian Sea by Mnemiopsis leidyi was held in Baku, Azerbaijan, at the end of April 2001. Participants closed the meeting with the decision to suspend consideration of intentionally introducing Atlantic butterfish, another major predator of sea walnuts, into the Caspian Sea as a biological control. Intentional introduction of non-native species is oftentimes a controversial measure which requires extensive precautions.

Spiny dogfish (Squalus acanthias): Spiny dogfish have a worldwide distribution, appearing natively in the Atlantic, Indian, and Pacific oceans, and inhabiting as well the Mediterranean Sea and the Black Sea. Nevertheless, this natural predator of sea walnuts poses a small threat to its prey because of its own declining worldwide population as a result of overfishing by target and bycatch fisheries. In 2006 the International Union for the Conservation of Nature (IUCN) added spiny dogfish to its Red List of Threatened Species, categorizing the once abundant species as vulnerable to the endangerment of extinction.

Pink comb jellies: Participants at the First International Meeting on the Caspian Sea invasion by sea walnuts concluded that pink comb jellies are the best choice for biological control. Pink comb jellies are expected soon to follow the sea walnuts' route into the Caspian Sea by way of ship ballast water.

Sea walnut: a New World native in an Old World setting

Sea walnuts are now regarded as the most studied ctenophore in the world. The attention which these durable water denizens have garnered stems from their explosively successful adaptation to European and Eurasian seas. Their colonization of the Old World was an accident of history that continues to this day and beyond. Through ecological imbalances, an innocuous, inconspicuous creature which is closer to the bottom of the food chain wreaked havoc throughout the oceanic food chain and devastated human economies as well.

Unsuspectingly pumped from their territorial waters and then unceremoniously dumped into an alien environment in a distant quarter of the globe, sea walnuts first sought to survive and then flourished because the Black Sea, their new home, was less threatening and more accommodating than their native waters. Unfortunately, their success created a massive deficit in the defenseless, unprepared Black Sea ecosystem. Then while the Black Sea staggered to recover, sea walnuts staged a similar, albeit swifter, takeover of the delicate Caspian Sea.

Transported from the New World to the Old World, sea walnuts have enthralled the world's seas by their tentacles. The problem is how to loosen their sticky grip. And the dramatic lesson which sea walnuts are teaching the world is that there are no easy answers to disruptions in the oceanic food chain.

My special thanks to talented photographers/concerned organizations who make their fine images available on the internet:

*** Marco Faasse for photo of Mnemiopsis leidyi (Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported license)

*** ottompo for January 25, 2005 Flickr photos of Mnemiopsis leidyi, São Sebastião, Sao Paulo, Brazil (Creative Commons Attribution-NonCommercial-NoDerivs 2.0 Generic license)

*** Bastique for 2006-06-01 photos, Solitary warty comb jelly, Monterey Aquarium, and Two warty comb jellies, Monterey Aquarium (Creative Commons Attribution-Share Alike 3.0 Unported license)

*** jillmotts for March 6, 2008 Flickr photo of Warty comb jelly, Monterey Aquarium (Creative Commons Attribution-NonCommercial-ShareAlike 2.0 Generic license)

*** Steven G. Johnson for August 16, 2008 Flickr photo of Sea walnut comb jellies, New England Aquarium, Boston, Massachusetts (Creative Commons Attribution-Share Alike 3.0 Unported license)

*** National Aeronautics and Space Administration (NASA) for (1) Landsat image of Chesapeake Bay and adjacent watershed region, (2) International Maritime Organization's Cross section of ships showing ballast tanks and the ballast water cycle, and (3) Northeast Fisheries Science Center's photo of Atlantic butterfish

*** Aqua-photos.com for August 29, 2007 Flickr photo of Mnemiopsis leidyi, Alvern, Akershus Fylke, Norway (Creative Commons Attribution-NonCommercial-ShareAlike 2.0 Generic license)

*** Lyubomir Klissurov/UniProt Consortium for Black Sea photos of Mnemiopsis leidyi and Beroe ovata (Creative Commons Attribution-NoDerivs 3.0 Unported license)

*** Daniel Ashton for November 29, 2007 Flickr photo of Glowing jellies, National Zoo, Mount Pleasant, Washington DC (Creative Commons Attribution-NonCommercial-ShareAlike 2.0 Generic license)

*** Ross Pollack (Ross Hong Kong) for July 8, 2011 Flickr photo of Sea walnuts, New England Aquarium, Boston, Massachusetts (Creative Commons Attribution-NonCommercial-ShareAlike 2.0 Generic license)

*** Kent McFarland for January 23, 2011 Flickr photo of Leidyi's comb jelly, New England Aquarium, Boston, Massachusetts (Creative Commons Attribution-NonCommercial 2.0 Generic license)

*** Hans Hillewaert for February 26, 2010 photo of Brine shrimp (Artemia salina) (Creative Commons Attribution-Share Alike 3.0 Unported license)

*** Uwe Kils for photo of Copepod (Creative Commons Attribution-Share Alike 3.0 Unported license)

*** Wally Gobetz (wally g) for October 29, 2010 Flickr photo of Atlantic sea nettle, National Aquarium, Baltimore, Maryland (Creative Commons Attribution-NonCommercial-NoDerivs 2.0 Generic license)

*** Eric Heupel (eclectic echoes) for May 26, 2011 Flickr photo of Atlantic sea nettle (Chrysaora quinquecirrha) with juvenile Atlantic butterfish (Peprilus triacanthus), Grey's Reef National Marine Sanctuary, Georgia (Creative Commons Attribution-NonCommercial 2.0 Generic license)

*** Travis S for December 27, 2007 Flickr photo of Lion's mane jellyfish (Cyanea capillata), Resurrection Bay, Seward, Alaska (Creative Commons Attribution-NonCommercial 2.0 Generic license)

*** D. Ross Robertson for August 2010 photo of Spiny dogfish (Squalus acanthias), Monterey Bay Aquarium (Creative Commons Attribution-NonCommercial 3.0 Unported license)

*** UNEP/GRID-Arendal for Philippe Rekacewicz's maps (1) How the comb jelly (Mnemiopsis leidyi) is spreading through European sea and (2) Comb jelly (Mnemiopsis leidyi) spreading through the Caspian Sea

*** Etrusko25 for October 24, 2008 Public Domain photo of European anchovies (Engraulis encrasicolus), Ligurian Sea, Italy

*** Smithsonian Environmental Research Center for YouTube video of Removing Invasive Species from Ballast Water

*** DTUAqua for YouTube video of Mnemiopsis leidyi cruising for prey

*** Ed Hunsinger (edrabbit) for March 18, 2007 Flickr photo of Warty comb jelly, Monterey Aquarium (Creative Commons Attribution-NonCommercial 2.0 Generic license)

Bailey, Robert S. Inhabitants of Chesapeake Bay. Part 1: Animals of Jelly. Gloucester Point VA: Virginia Fisheries Laboratory, 1960.

Bumann, Dirk, and Gabriela Puls. “The ctenophore Mnemiopsis leidyi has a flow-through system for digestion with three consecutive phases of extracellular digestion.” Physiological Zoology, Volume 70, No. 1 (January-February 1997): 1-6.

“Comb Jellies.” Chesapeake Bay Program: Bay Field Guide by Habitat. www.chesapeakebay.net/bfg_combjellies.aspx?menuitem=14417 (Last accessed August 31, 2011)

Dunning, Page. “Mnemiopsis leidyi.” Animal Diversity Web. http://animaldiversity.ummz.umich.edu/site/accounts/information/Mnemiopsis_leidyi.html (Last accessed August 31, 2011)

Ghabooli, Sara, Tamara A. Shiganova, Aibin Zhan, Melania E. Cristescu, Peyman Eghtesadi-Araghi, and Hugh J. MacIsaac. “Multiple introductions and invasion pathways for the invasive ctenophore Mnemiopsis leidyi in Eurasia.” Biological Invasions, Volume 13 Issue 3 (2011):679-690.

Goode, George Brown. The Fisheries and Fishery Industries of the United States. Washington DC: Government Printing Office, 1884.

Hansson, Hans G. “Leidyi.” Biographical Etymology of Marine Organism Names (BEMON). Tjärnö Marine Biological Laboratory. http://www.tmbl.gu.se/libdb/taxon/personetymol/index.htm (Last accessed August 31, 2011)

Harbison, Richard. "The Biology of Mnemiopsis leidyi in the Americas." Proceedings: First International Meeting on the Invasion of the Caspian Sea by the Comb Jelly Mnemiopsis --- Problems, Perspectives, Need for Action, Baku, Azerbaijan, April 24-26, 2001.

“Jellyfish of the Chesapeake.” Maryland Sea Grant: Coast, Bay & Watershed Issues: The Living Chesapeake. http://www.mdsg.umd.edu/issues/chesapeake/jellyfish/ (Last accessed August 31, 2011)

Mills, Claudia E. “Ctenophores.” University of Washington Department of Biology. http://faculty.washington.edu/cemills/Ctenophores.html (Last accessed August 28, 2011)

“Mnemiopsis leidyi A. Agassiz, 1865.” Encyclopedia of Life. http://www.eol.org/pages/393337 (Last accessed August 31, 2011)

National Science Foundation. “The First Animal On Earth Was Significantly More Complex Than Previously Believed.” ScienceDaily, April 11, 2008. http://www.sciencedaily.com/releases/2008/04/080410153648.htm (Last accessed August 31, 2011)

Reshetiloff, Kathy. “Nature’s light shows dazzle those who know where to look.” Bay Journal, July/August 2009. http://www.bayjournal.com/article.cfm?article=3640 (Last accessed August 31, 2011)

Roman, Joe, and Marion McClary. “Aquatic invasive species.” In: Cutler J. Cleveland, ed. Encyclopedia of Earth. Washington DC: Environmental Information Coalition, National Council for Science and the Environment, July 2, 2010. http://www.eoearth.org/article/Aquatic_invasive_species (Last accessed August 31, 2011)

Stephens, Lester D., and Dale R. Calder. Seafaring Scientist: Alfred Goldsborough Mayer, Pioneer in Marine Biology. Columbia SC: University of South Carolina Press, 2006.

Copyright Wednesday, August 31, 2011 by Derdriu