Analysis of the Extracellular and Enigmatic Myxazoa
Analysis of the Extracellular and Enigmatic Myxazoa
The phylum Myxozoa falls under the domain Eukarya and were traditionally thought of as protozoa. Within the last two decades however more advanced identifying techniques have led us to believe that they are in fact metazoans more closely related to Cnidarians, but this will be discussed later in this essay. There are approximately twelve thousand species of Myxozoa, and it is believed that there may be more than this number. Most Myxozoa are parasites which inhabit primarily tissues and organ cavities of ectothermic vertebrates, especially fish, and can cause major problems within fish farms and hatcheries.
Myxozoans are extra cellular parasites of ectothermic vertebrates and invertebrates. They mainly infect fish especially salmonoids, but do also infect some amphibians, reptiles and annelids. In fish they are found in cavities such as gall bladder, urinary tract, ureters or tissues including – cartilage, muscle gills and skin. In Annelids they can be found in the intestinal epithelium.
Myxozoans have multicellular spores which contain two or more shell valves which join at a sutural plane, a sporoplasm that is infective to the host, and polar capsules containing polar filaments coiled within. Once ingested these polar filaments are then be expelled and it is thought that they are used as a means of attachment to the host.
The most well known species of Myxozoa is the Myxobolus cerebalis due to its affect on salmonoids farms and hatcheries as it is responsible foe significant losses of stock. It affects the cartilage and nervous systems of many salmonoids worldwide.
Nearly all Myxozoa have a typical lifecycle common amongst most organisms of the phylum normally involving two host species. The life cycle of Myxobolus cerebalis ids the best example as it is the most known about and most others follow essentially the same pattern.
Spores released by the host species (salmonoids usually) are ingested by a tubificid oligochaete. The polar filaments within the polar capsules of the spore are then everted and the spores release the infective sporoplasma. During development within the oligochaete a form of sexual reproduction occurs along with the production of triactinomyxon spores. These new spores are released into the environment along with the host faeces. These spores were until recently believed to be a different species. When the next host, a salmonoids...