What are Comb Jellies?

Comb jellies are marine creatures in the phylum Ctenophora, which includes around 150 known species. These organisms can be found all over the world, sometimes acting as invasive species in areas where they are not native, and causing environmental problems or difficulties in the fishing industry. They are very unusual-looking creatures, and some people find them quite beautiful, while others consider them to be pests in regions where they have proliferated at the expense of other marine organisms.

Although comb jellies have “jelly” in their name, they are not related to jellyfish. Their bodies are roughly egg-shaped, typically with two trailing sticky tentacles. The outside of the jelly's body is covered in a pair of translucent skins which surround a jelly-like membrane, and the inside has a number of basic anatomical structures. The most notable structure is the “comb” for which the jellies are named. Each jelly has multiple combs, long ridges covered in cilia which run along the body. The movements of the cilia propel the creature through the water, allowing it to pursue prey.

Comb jellies are carnivores, pursuing a wide range of marine organisms. They vary in size from around the size of a pinky to the size of a small child, and they reproduce sexually, generating eggs which hatch into larvae. The larvae go through a planktonic stage which involves drifting through the ocean without the ability to move freely before they develop into fully grown adults. Several species remain planktonic as adults, catching prey as it drifts through the ocean with them.

The body of the comb jelly is translucent, and it may be colorless, orange, yellow, red, or black. Many live in regions of the ocean where they can be readily observed and identified, although some species prefer deeper waters, and these creatures are ideally adapted to life in the ocean. Their bodies are lightweight, posing minimal resistance, and the jelly membrane allows comb jellies to go quite deep without being damaged by the high pressure. Some produce chemical sensors which they use to detect passing prey.

Because comb jellies do not have stinging cells, they are not harmful to people. Many of them are bedecked with rainbow colors in the daylight, thanks to the refraction of light through their transparent bodies. Their sticky tentacles, however, can entrap prey, including other jellies. Some examples of well-known comb jellies include sea gooseberries and Venus' girdle.

Comb jellies, or ctenophores, are gelatinous marine animals that, despite their name, are not jellyfish. They are distinguished by rows of ciliary plates, known as 'combs,' which they use for locomotion. Unlike jellyfish, they lack stinging cells and instead capture prey with sticky cells called colloblasts. Comb jellies are also bioluminescent, emitting a beautiful light in the dark ocean waters.

Comb jellies inhabit a wide range of marine environments, from shallow coastal waters to the deep sea. They are globally distributed, with species found in every ocean. Some prefer the open sea, while others reside in brackish estuaries. Their adaptability allows them to thrive in various temperatures and depths, making them a common sight in many marine ecosystems.

Comb jellies are carnivorous, feeding primarily on microscopic plankton, small crustaceans, and sometimes even other comb jellies. They play a crucial role in the ocean's food web, both as predators and prey. By consuming large amounts of plankton, they help regulate plankton populations and serve as a food source for larger marine animals, thus maintaining ecological balance.

Comb jellies have a fascinating reproductive strategy; they are hermaphrodites, meaning each individual possesses both male and female reproductive organs. They can reproduce both sexually, by releasing eggs and sperm into the water, and asexually, through a process called fission. Their lifecycle includes a planktonic larval stage before they grow into the free-swimming adult form.

Yes, certain species of comb jellies, such as Mnemiopsis leidyi, have become invasive in non-native waters. For example, when introduced into the Black Sea, this species caused significant ecological and economic damage by outcompeting native fish for food. Their rapid reproduction and voracious appetite can disrupt local ecosystems and fisheries, highlighting the impact of invasive species on biodiversity.

Comb jellies hold a key position in the evolutionary tree of life, providing insights into the early evolution of animals. Their unique nervous system and muscle structures are of particular interest to biologists. Additionally, their remarkable regenerative abilities, which allow them to heal rapidly from injuries, are being studied for potential applications in regenerative medicine and biology.