The Mesozoa are minuscule, worm-like parasites of marine invertebrates. Generally, these tiny, elusive creatures consist of a somatoderm of ciliated cells surrounding one or more reproductive cells.
The alveolates are a group of protists, considered a major clade and superphylum within Eukarya. They are currently grouped with the stramenopiles and Rhizaria among the protists with tubulocristate mitochondria, the group being referred to as SAR.
The Oligohymenophorea are a large class of ciliates. There is typically a ventral groove containing the mouth and distinct oral cilia, separate from those of the body. These include a paroral membrane to the right of the mouth and membranelles, usually three in number, to its left. The cytopharynx is inconspicuous and never forms the complex cyrtos found in similar classes. Body cilia generally arise from monokinetids, with dikinetids occurring in limited distribution over part of the body.
Orthonectida is a small phylum of poorly known parasites of marine invertebrates that are among the simplest of multi-cellular organisms. Members of this phylum are known as orthonectids.
The Ascetosporea are a group of eukaryotes that are parasites of animals, especially marine invertebrates. The two groups, the haplosporids and paramyxids, are not particularly similar morphologically, but consistently group together on molecular trees, which place them near the base of the Cercozoa. Both produce spores without the complex structures found in similar groups.
The Syndiniales are an order of early branching dinoflagellates, found as parasites of crustaceans, fish, algae, cnidarians, and protists. The trophic form is often multinucleate, and ultimately divides to form motile spores, which have two flagella in typical dinoflagellate arrangement. They lack a theca and chloroplasts, and unlike all other orders, the nucleus is never a dinokaryon. A well-studied example is Amoebophrya, which is a parasite of other dinoflagellates and may play a part in ending red tides. Several MALV groups have been assigned to Syndiniales; recent studies, however, show paraphyly of MALVs suggesting that only those groups that branch as sister to dinokaryotes belong to Syndiniales.
The Archamoebae are a group of protists originally thought to have evolved before the acquisition of mitochondria by eukaryotes. They include genera that are internal parasites or commensals of animals. A few species are human pathogens, causing diseases such as amoebic dysentery. The other genera of archamoebae live in freshwater habitats and are unusual among amoebae in possessing flagella. Most have a single nucleus and flagellum, but the giant amoeba Pelomyxa has many of each.
The Lessepsian migration is the migration of marine species across the Suez Canal, usually from the Red Sea to the Mediterranean Sea, and more rarely in the opposite direction. When the canal was completed in 1869, fish, crustaceans, mollusks, and other marine animals and plants were exposed to an artificial passage between the two naturally separate bodies of water, and cross-contamination was made possible between formerly isolated ecosystems. The phenomenon is still occurring today. It is named after Ferdinand de Lesseps, the French diplomat in charge of the canal's construction.
Syndinium is a cosmopolitan genus of parasitic dinoflagellates that infest and kill marine planktonic species of copepods and radiolarians. Syndinium belongs to order Syndiniales, a candidate for the uncultured group I and II marine alveolates. The lifecycle of Syndinium is not well understood beyond the parasitic and zoospore stages.
Hematodinium is a genus of dinoflagellates. Species in this genus, such as Hematodinium perezi, the type species, are internal parasites of the hemolymph of crustaceans such as the Atlantic blue crab and Norway lobster. Species in the genus are economically damaging to commercial crab fisheries, including causing bitter crab disease in the large Tanner or snow crab fisheries of the Bering Sea.
Orchitophrya stellarum is a species of single-celled marine ciliates, a member of the class Oligohymenophorea. It is found living freely in the north Atlantic and Pacific Oceans but is also parasitic, being found inside the gonads of starfish.
Colliniidae is a family of ciliates of the order Apostomatida.
Collinia is a genus of parasitoid ciliates of the Colliniidae family.
Collinia beringensis is a species of parasitoid ciliates of the Colliniidae family. It is an endoparasite of Thysanoessa inermis, a species of krill.
Chromidina is a genus of apostome ciliates of the family Opalinopsidae. Species of Chromidina are parasitic in the renal and pancreatic appendages of cephalopods.
Chromidina elegans is a species of parasitic ciliates. It is a parasite of the cuttlefish Sepia elegans, which was described from off Naples, Italy, by Foettinger in 1881 under the name Benedenia elegans and latter assigned to the genus Chromidina by Gonder, in 1905. The species was redescribed by Chatton & Lwoff in 1935.
Sepia elegans, the elegant cuttlefish, is a species of cuttlefish in the family Sepiidae from the eastern Atlantic Ocean and the Mediterranean Sea. It is an important species for fisheries in some parts of the Mediterranean where its population may have suffered from overfishing.
Coccidinium is a genus of parasitic syndinian dinoflagellates that infect the nucleus and cytoplasm of other marine dinoflagellates. Coccidinium, along with two other dinoflagellate genera, Amoebophyra and Duboscquella, contain species that are the primary endoparasites of marine dinoflagellates. While numerous studies have been conducted on the genus Amoebophyra, specifically Amoebophyra ceratii, little is known about Coccidinium. These microscopic organisms have gone relatively unstudied after the initial observations of Édouard Chatton and Berthe Biecheler in 1934 and 1936.
Microcotyle sebastis is a species of monogenean, parasitic on the gills of a marine fish. It belongs to the family Microcotylidae.
Euduboscquella (juˌduːboʊˈskwɛlə) is a genus of early branching dinoflagellates found in coastal waters around the globe. The members of this genus are all intracellular parasites that primarily infect Tintinnids. Euduboscquella are commonly found in marine environments, either infecting a host or in a resting stage in search of a new host, but there are a few freshwater and terrestrial species. Euduboscquella possess a multi-grooved shield separating their cytoplasm from the host’s cytoplasm, which is used by researchers to taxonomically identify them. The genus Euduboscquella contains nine species.
