2 Oct 2016

What do Jellyfish Eat?

jellyfish diet

Diet of Jellyfishes

Jellyfish is an invertebrate that lives in the oceans. It can be seen almost every parts of the oceans. You have seen them in the seas, but do you know what they eat? 

Jellyfish is a carnivore. Carnivores are the animals that are hunters. Yes, these sea creatures are not vegetarians. They are active predators of the sea.

There are thousands of species of jellyfishes. They have different body sizes. There habitation is also different. That’s why there can be some difference between the foods taken by each species.

Jellyfish is a plankton eater. Plankton is groups of diverse tiny sea animals and plants. Plankton float in the sea water (usually close to the surface). There are two types of plankton- zooplankton and phytoplankton. Zooplankton is the group of small animals and phytoplankton is of tiny algae and other plant materials. As jellyfishes are carnivores, generally they eat only zooplankton.

Plankton cannot move against the ocean currents. They are too small to move against the forces of the ocean. So, they float in the upper layer of the water columns. Jellyfishes feed on them by floating with them. In fact, jellyfishes themselves are big plankton.

Jellyfish eat plankton animals like copepod, krill, isopod, amphipod etc. Copepods are small crustaceans. They are two small (1 to 2 mm). They are the main food source of most jellies. Krill is another type of crustacean that looks like shrimps. A krill can be anywhere between 1 to 10 cm in length. Another comparatively larger planktonic crustacean is amphipods. They have no carapace or shell like most other crustacean.

What Does Pet Jellyfish Eat

Pet jellies lived in controlled environments. They can’t get natural plankton in aquariums. So, you need to supply outside food to them. The baby jellies need small, newly hatched brine shrimps. The adults can eat the frozen brine shrimps too. Cyclopeeze is a popular jellyfish food which is very common in pet stores.

You can hatch baby brine shrimps at home by using the tool kits like the San Francisco Bay Brand Brine Shrimp Hatchery Kit. It is easy to use.

San Francisco Bay Brand Brine Shrimp Hatchery Kit, (Pack of 3) - 0.74 ounce (21 g)


Does Jellyfish Eat Fishes?

Small jellyfishes eat fish eggs. Some small fish larva that floats with the plankton like that of some eels and ocean sunfishes are being eaten with other stuff. Big jellies like the Nomura’s jellyfish or the Lion’s mane is known to consume small fishes, too. But most species can’t eat fish because there mouth is not that large and they do not have any teeth to cut the fish into smaller pieces.
Big jellyfishes also eat small shrimps. Some is also observed to eat crabs. Bigger crabs or shrimps can’t be eaten by any jellyfish.

How Does Jellyfish Feed?

Jellyfishes are not active hunters. They do not chase prey like sharks. So, it is not possible to make a movie named “Tentacles” with them. They are chance hunters.

Jellyfish medusa floats with the water current from one place to another. When an unfortunate copepod or krill comes contact with the trailing tentacles, they get stuck. Jellies use their tentacles as nets to catch the food items. The tentacles are armed with thousands of small stinger cells. The small animal catch becomes unable to move due to the venom injected by the jellyfish stings.

The incapacitated and doomed animal is brought to the mouth hole of the jellyfish by the movement of the tentacles. The mouth hole doubles as anus. It is situated at the inner center of the bell of the medusa. It has no teeth so the prey is devoured whole. There are no digestive organs, too. So, the tiny animal is digested inside the body cavity.


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