Comb jellyfish

http://www.montereybayaquarium.org/animal-guide/invertebrates

 Comb jellyfish Mnemiopsis leidyi

The comb jelly belongs to the Bolinopsidae  family.

These jellyfish belong to the small phylum group Ctenophora which contains ninety species. Most of the jellyfish are transparent but there are a few which are colourful displaying blues and greens. 

There are a few special characteristics of the Ctenophora; 

1. Radially or bi-radial symmetrical. 2. Multi-cellular body with small amount of tissues, organs and organelles. 3.Body contains an internal cavity and a mouth and anal pores. 4.Swims by means of plates of cilia which are the the combs like features 5.Reproduction mostly sexual as hermaphrodites 6. Well developed sub-epidermal nerve 7. Larval stage (planktonic.) 8. Marine 9. Carnivorous.

The comb jellies are oval in shape with eight small comb-like sections, which are called Costa, they use the costa to move through the water and to keep orientation. When the jellyfish is swimming the comb-like sections deflects the sunlight which produces a multi-coloured effect. When they are hunting they hold the prey in their increased stomach. 

The comb jellies have particular organs which allows them to find chemicals in the mouth which allows the jellies find their food. These jellies will sometimes eat other comb jellies which are bigger than them, they do this by using their cilia to bite chunks of the opponent. They also have a statocyst (gravity sensitive structure), this allows them to effortlessly move up and down and stay upright within the water. 

The comb jellies are most commonly found in the Atlantic and prey on copepods and the larvae of the oysters. 
These jellyfish live near the shore in warm water and are easily found but other jellyfish live in the deep sea and in the poles. The comb jellyfish move around in great numbers and sometimes have bad effects on the fish stocks as they eat the fish eggs. 

The body has three layers (Epidermis, Mesoglea and Gastrodermis). The comb jellyfish has a mouth and an anus at either end of the body, the gut goes straight from the mouth to the anus, there are canals which come from the stomach to the costa. The waste is removed by the anus and the mouth and digestion is intracellular and extracellular. These jellyfish have no organs for gas exchange but this happens right away across the body. They have no circulatory system or brain, but they do have a sub-epidermal nerve net which is a connection of nerves which runs under the skin. Statocyst is the main sense organ and it located close to the anus. 

They are ctenophores are hermaphroditic, so the sperm and eggs are dispersed into the water to fertilise. The larvae are called Cydippid, they are free swimming. 

Earthlife.net, (2015). The Comb Jellies (Phylum Ctenophora). [online] Available at: http://www.earthlife.net/inverts/ctenophora.html [Accessed 5 Apr. 2015].

Montereybayaquarium.org, (2015). Comb jelly, Open Waters, Invertebrates, Beroe spp at the Monterey Bay Aquarium. [online] Available at: http://www.montereybayaquarium.org/animal-guide/invertebrates/comb-jelly [Accessed 5 Apr. 2015].