What is a Sea Walnut? A Sea Walnut is a ctenophore organism (a stingless jellyfish-like animal having comb-like structures). Mnemiopsis leidyi, this warty comb jellyfish or sea walnut, is a species of tentaculata ctenophora (comb jelly). Inhabitant to the western Atlantic coastal waters and the east coast of South America, but has become entrenched as an invasive species in European and western Asian areas. However, since 1982 it has been spotted in the Black Sea and thereafter the Caspian Sea. In both the seas, the population has burgeoned since they do not contain any natural predators in the region, and thus this resulted in the collapse of various fisheries in the region for as much as they feed on the zooplankton that the commercial fish essentially consume.
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Sea Walnut Scientific Name
Mnemiopsis leidyi (Sea Walnut) is the Latin term of sea walnut’s scientific name. This ctenophore is an inhabitant of the east coast of North and South America.
Sea Walnut Scientific Description
Sea Walnut Anatomy
Sea Walnut Conservation Status
Sea walnut invasive species are not threatened. It is however invasive in some seas.
Sea Walnut Physical Description
The bodies of comb jellies are quite tender and can be adversely collapsed when eliminated from water (during storms, comb jellies sink to depths to avoid harmful currents); hence, when seizing a comb jelly, it is ideal to gently scoop the organism into a jar with environs water. Since even small whirl currents can injure the specimen, enormous care is needed.
The Sea walnut is about 100-120mm in length, and the width of the body is estimated at half of its length. Their body is split up into eight symmetrical parts having longitudinal bands of cilia. They are bio-luminescent and their bodies are clear.
The diet of comb jelly comprises zooplankton along with the eggs and larva of juvenile fish, sea jellies, copepods, and even other ctenophores. They are first and foremost consumers and are also the filter feeders that feed by pumping water into its body and capturing small prey on the inside surface of the two lobes on tentacles.
Sea Walnut Size & Shape
As the name (common) suggests, sea walnuts are shaped like the meat of a walnut. As adults, they are deficient in tentacles and can grow to several inches in length. Also referred to as a comb jelly, since they have rows of cilia that somewhat look like the teeth of a comb. These cilia easily deflect beams of light and induce pulsing rainbows to travel along their body.
Sea Walnut Color
Sea walnuts are white or transparent. They can produce light when flustered, and can commonly be found flashing brightly in boat wakes at night.
Sea Walnut Habitat & Abundance
Within reach-surface waters in the Western Atlantic. The comb jelly or sea walnut is quite common across most of Chesapeake Bay, and, while the population fastens seasonally, exists year-round. This ctenophore (a stingless jellyfish-like animal) is inhabited to the east coast of North and South America. In 1982, it was found in the Black Sea, where it was carried off by ballast water. Following this, it spread to the Caspian Sea. In both places, it multiplied and developed huge populations. The sea walnuts subscribed to the slumping of local fisheries since they feed on zooplankton that the commercial fish also consume. M. leidy has also been spotted in the Baltic, Mediterranean, and North Seas.
The Secret behind Success of Sea Walnut
It is believed that the secret to the success of sea walnut’s lies in their unfussy and effective hunting habits. There has been a research study conducted by Colin where he hand-picked sea walnuts from his domestic dock and had put them in water seeded with tiny particles. The particles were lit with a laser and pictured with a camera, for the purpose to understand how the sea walnut twisted the flow of water around it.
It was discovered that it produces a current that sucks everything in the encompassing water into its tentacle-ringed mouth. The current it produces flows smoothly at just 2 millimetres per second. Only when it passes through the animal’s mouth does it amplify and warp, spiralling into a corkscrew motion, which goes past the tentacles. The mouth shuts, and virtually everything gets trapped in this feeding current. The sea walnut produces its own conveyor belt of food, a streaming buffet composed of a different selection of dishes
To escape this, the sea walnut requires stealth. Floating plankton won’t display much of a challenge, but some morsels like small crustaceans (copepods) are active swimmers which can trace the movements of incoming predators. If they sense danger, it only takes 2 milliseconds to swim away at the highest possible speed. However, Colin discovered that the water interruption caused by the sea walnut's current is much less than what the copepods can trace.
Feeding currents are not uncommon. Shellfish and other animals use them but they do so in a plain-spoken manner. Their currents are chaotic and explosive, used to attract small plankton that can’t swim away. A brute force approach is actually applied, and one that’s very distinctive to the stealthy strategy of the sea walnut.
Sea Walnut Amazing and Quick Facts
The sea walnut is a simple, sheer, marine pellet, only a few inches long.
A sea walnut looks like a jellyfish but in fact, it comes from a different but related group known as the comb jellies or ctenophores.
The sea walnut invasive species is not exactly a fearsome predator.
Ocean’s stealthiest predators, the sea walnut are a major player in the oceans. This ability also makes it a notorious invader.
This invasive species cannot see but can only sense the movement of prey slightly beyond its body.
It has no evident weapons and it does not even have the potential of great speed.
As an outcome of its biological-physical characteristics, it is unable to chase its prey. Rather, it employs beating hairs referred to as cilia in order to create undetectable water currents that bring its prey straight into its mouth.
The weapons of a sea walnut are surprising and have a harsh efficiency.
Irrespective of its simplicity, the sea walnut’s ninja-like stealth makes it ruthlessly successful.
For a sea walnut’s size, the animal can seize its prey at the same rate as fish, and that’s just when it stays still. If it moves, it could double what it consumes.