Pelagia noctiluca
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| Pelagia noctiluca Forsskal, 1775 |
Pelagia noctiluca (Forsskal, 1775) is a jellyfish, belonging to the family
In Greek Pelagia means “of the sea”, nocti stands for night and luca means light thus Pelagia noctiluca can be described as a marine organism with the ability to glow in the dark.
This species of jellyfish commonly known as mauve stinger, amongst many other common names, is widely distributed in all warm and temperate waters such as the Mediterranean Sea, Red Sea and Atlantic Ocean. However there were also some sightings of this species in Hawaii.
[edit] Classification of P. noctiluca
P. noctiluca is an animal, thus non-photosynthetic, multicellular eukaryote. Being a cnidarian it is diploblastic, having an
The body is radially symmetrical. There is only one body cavity (coelenteron) known as gastrovascular cavity. This is a primitive gut or digestive cavity with only one opening that acts as a mouth and anus. Being radially symmetrical it has no head and thus no centralized nervous system. The nervous system present is primitive, consisting of a simple net composed of naked and largely non-polar neurons. In addition P. noctiluca also lacks a gaseous exchange, excretory and circulatory system. However cnidaria have evolved cnidae, cells which serve for a variety of functions that include prey capture, defense, locomotion and attachment. When fully formed cnidae are called
P. noctiluca is a scyphozoan and adapted to a pelagic mode of life. This class of organisms has adapted in such a way that the polyp stage is shortened or in some cases such as that of the genus Pelagia this is absent, thus direct development exists. These organisms have a well developed
Semaeostomates are mainly distinguished from the other orders by having simple oral arms with frilled or folded lips. The order semaestomae comprises three families: Pelagiidae, Cyaneidae,and Ulmaridae, distinguishable by the following characters:
1. Gastrovascular cavity divided by radial septa into rhopalar and tentacular pouches.
a. Pouches simple and unbranched………………………………...Pelagiidae
b. Pouches branched……………………………………………..…Cyaneidae
2. Gastrovascular system in form of unbranched and branching canals, or with anastomosing radial canals……………………………………………....Ulmaridae
In addition the Pelagiidae has no ring canal, marginal tentacles arising from umbrella margin. There are three genera in this family.
[edit] Structure and adaptations of Pelagia noctiluca
P. noctiluca has eight marginal tentacles alternating with eight marginal sense organs. This species reproduces sexually. Four
Feeding reactions were studied by Bozler (1926), where a piece of food was given to the marginal tentacle, the tentacle contracted quickly. There was a slow contraction of the coronal muscle which brought the tentacle nearer to the mouth. The food was grasped by the lip of one of the oral arm and transported slowly along until it reached the stomach. They were found to feed on Thalia democratica, however they are found mainly to feed by taking food particle by the amoeboid process of the endoderm cells, thus being suspension feeders.
Movement is caused when the medusa pulsates, the marginal tentacles are contracted straightened and stiffened. Pulsation was found to be optimal between 8° to 26°C. Movement is only restricted vertically and thus P. noctiluca are carried in large swarms by currents.
As its name implies P. noctiluca has luminescing power. Light is given in the form of flashes when the medusa is stimulated by turbulence created by a ship’s motion or by waves. This flashing is only of gradual duration and gradually fades.
[edit] References
- 'Pelagia noctiluca' 2005 assignment, Matthew Schembri
- ‘Mauve stinger - Pelagia noctiluca’[online] available at: [1]
- ‘Open ocean jellyfish’ [online] available at: [2]
- ‘Common Jellyfish’ [online] available at: [3]
- Russell, F.S. 1970. ‘The Medusae of the British Isles, Volume 2’: Pelagic Scyphozoa, with a supplement to Vol. I. Cambridge University Press
- R.S.K. Barnes 1998. ‘The Diversity of Living Organisms’, Blackwell Science
- R.S.K. Barnes, P. Calow and P.J.W Olive 1993, ‘The Invertebrates’ (second edition) Blackwell Science