Freshwater Jellyfish - Characteristics, Diet and Reproduction

Freshwater jellyfish: find out what this animal is like, its physical characteristics, character, behavior, etc. Jellyfish are aquatic animals that are grouped together in...

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" Jellyfish are aquatic animals that are grouped in the cnidarian family, a name that refers to a type of cell known as cnidocyte, from which is released a structure capable of inoculating a substance poison whose composition and intensity vary according to the species and that jellyfish use to defend themselves and hunt. Most of these invertebrates live in marine waters, however, a few species thrive in freshwater bodies, and in this PlanetAnimal file we are going to tell you about one of these species."

Do you want to know all the characteristics of the freshwater jellyfish? Its scientific name is Craspedacusta sowerbyi and it lives in different parts of the world. Find out everything about its habitat, its diet and its bite!

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  • Asia
  • China

Freshwater Jellyfish Features

The main characteristics of the freshwater jellyfish are:

  • Taxonomically, it is placed in the Medusozoan subphylum and the Hydrozoan class. Thus, despite the name given to the species, they are not considered true jellyfish because they are grouped in the class Scyphozoa.
  • It has no head or skeletal structure, as it is an invertebrate animal. It also has no separate organs for respiration or excretion and has a single orifice for feeding and excreting.
  • The body is made up of more than 90% of a water-based gelatinous substance.
  • As an adult, it is bell-shaped and also somewhat flattened compared to other jellyfish.
  • Around the bell are about 400 tentacles of various lengths, strong and loaded with nematocysts, useful for hunting, food and defense.
  • The digestive or stomach structure known as the manubrium is located towards the center and below the animal, where there is also the single opening we have already mentioned, through which food enters and waste exits excreted.
  • There is a circular channel bordering the bell and four radial channels, the latter being connected to the stomach area, which facilitate the transport of nutrients.
  • It is common to observe the four gonads (genital glands) associated with the four radial canals, which are differentiated by sex, as they are dysmorphic animals.
  • On the edge of the bell are structures called statocysts, which allow the jellyfish to orient itself and maintain its balance.
  • " On the tentacles there is a tissue called ocelli, thanks to which it detects light, darkness and, in general, food and potential predators."
  • The diameter of an adult freshwater jellyfish can reach about 2.5 cm and its body mass can vary from 3 to 5 g.

Freshwater Jellyfish Colors

One of the easiest ways to identify jellyfish species, aside from their distinctive sizes and shapes, is by the colors they possess. The color of the freshwater jellyfish is whitish or greenish, and the gonad area is usually more opaque than the rest of the body.

Freshwater jellyfish habitat

The freshwater jellyfish was identified and described in England in the late 1800s, but is native to China, specifically the Yangtze River Basin.It is now found on all continents except Antarctica, due to its introduction as a result of trade between countries, as ornamental aquatic plants.

The freshwater jellyfish adapts very well to different ecosystems of this type, but it seems to be more present in areas where the waters are calm and where there are no strong currents. Thus, it is commonly found in freshwater lakes, natural or man-made reservoirs, rocky quarry areas with water or ponds with algae.

In particular, freshwater jellyfish have been reported in most parts of the United States and Canada.

Habits of the Freshwater Jellyfish

The species is usually found at the bottom of shallow water bodies and does not move around often except to forage for food or to escape predation. It can be found solitary or in colonial aggregations.

Freshwater jellyfish blooms typically occur during the summer and fall months, with peaks around August and September. These population growths are mainly related to the increase in water temperature and the presence of food, which testifies to its preference for warm waters.

However, the freshwater jellyfish is somewhat unpredictable in terms of its presence and population development, as it sometimes does not respond to the aforementioned patterns. Scientists therefore continue to study its behavior to learn more about it.

Reproduction of the freshwater jellyfish

" Freshwater jellyfish generally follow the reproductive cycle of this type of marine animal. Sexual phase, during which the female and the male release their gametes into the water where they are fertilized. Subsequently, a larva is formed, which in this case is called a planula.This larva then seeks a place at the bottom of the water, which can be on plants, rocks or roots, to attach itself, form hills and develop into the next stage called a polyp, which gives rise to a polyp of jellyfish."

" Jellyfish polyp is produced asexually as the polyp divides by budding and gives rise to an immature jellyfish, which will develop into an adult individual. But a particular aspect is that this species can also produce a bud known as a frustule, which lives freely and, although it cannot travel as far as the planula, it seeks another place to settle and give result in further polyp formation. In other words, this phase, called a frustule, would be a kind of transition used by the polyp to move to other spaces and continue to reproduce."

" In contrast, freshwater jellyfish polyps can enter a dormant state when conditions are unfavorable, and change shape by contracting.In this case, they are called podocysts, which, in turn, are passively transported on the legs of waterfowl, in algal clumps or on aquatic animals in general. Then, when conditions are favorable, the podocyst is activated to give rise to the polyp again and continue development."

Precise aspects of the above phases are still unknown and scientists are continuing their studies to better understand these reproductive cycles in freshwater jellyfish. However, it is speculated that its massive spread around the world could be due to this dormant state.

Feeding the Freshwater Jellyfish

It is a predatory animal, which feeds mainly on zooplankton and in particular small crustaceans such as daphnia and copepods. However, if given the chance, it can capture and eat small fish.

When prey touches the tentacle of the jellyfish, the nematocyst is activated, injecting the poisonous substance that paralyzes the victim. Then, using the same tentacle, the food is brought into the mouth to be digested.

Freshwater jellyfish sting

All jellyfish produce poisonous substances, some even fatal to humans, others having a milder but still painful or embarrassing effect. However, one particular aspect of this species is that its nematocysts have not been shown to penetrate human skin, so it would be completely harmless to humans. It is therefore a deadly predator for its main source of food, but not at all dangerous for humans. In fact, it is even considered a non-stinging jellyfish for humans.

State of conservation of the freshwater jellyfish

There is no assessment report on the conservation status of the freshwater jellyfish and, as mentioned, the evolution of its population in the water bodies is something somewhat unpredictable, but not believed to be at risk in this regard.

Freshwater jellyfish pictures

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