The spirotrichs are a large and diverse group of ciliate protozoa. They typically have prominent oral cilia in the form of a series of polykinetids, called the adoral zone of membranelles, beginning anterior to the oral cavity and running down to the left side of the mouth. There may also be one or two paroral membranes on its right side. The body cilia are fused to form polykinetids called cirri in some, and are sparse to absent in others.
The gastrotrichs, commonly referred to as hairybellies or hairybacks, are a group of microscopic (0.06-3.0 mm), worm-like, pseudocoelomate animals, and are widely distributed and abundant in freshwater and marine environments. They are mostly benthic and live within the periphyton, the layer of tiny organisms and detritus that is found on the seabed and the beds of other water bodies. The majority live on and between particles of sediment or on other submerged surfaces, but a few species are terrestrial and live on land in the film of water surrounding grains of soil. Gastrotrichs are divided into two orders, the Macrodasyida which are marine, and the Chaetonotida, some of which are marine and some freshwater. Nearly 800 species of gastrotrich have been described.
The heterotrichs are a class of ciliates. They typically have a prominent adoral zone of membranelles circling the mouth, used in locomotion and feeding, and shorter cilia on the rest of the body. Many species are highly contractile, and are typically compressed or conical in form. These include some of the largest protozoa, such as Stentor and Spirostomum, as well as many brightly pigmented forms, such as certain Blepharisma.
The plagiopylids are a small order of ciliates, including a few forms common in anaerobic habitats.
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.
The Litostomatea are a class of ciliates. The group consists of three subclasses: Haptoria, Trichostomatia and Rhynchostomatia. Haptoria includes mostly carnivorous forms such as Didinium, a species of which preys primarily on the ciliate Paramecium. Trichostomatia (trichostomes) are mostly endosymbionts in the digestive tracts of vertebrates. These include the species Balantidium coli, which is the only ciliate parasitic in humans. The group Rhynchostomatia includes two free-living orders previously included among the Haptoria, but now known to be genetically distinct from them, the Dileptida and the Tracheliida.
The Colpodea are a class of ciliates, of about 200 species common in freshwater and soil habitats. The body cilia are typically uniform, and are supported by dikinetids of characteristic structure, with cilia on both kinetosomes. The mouth may be apical or ventral, with more or less prominent associated polykinetids. Many are asymmetrical, the cells twisting sideways and then untwisting again prior to division, which often takes place within cysts. Colpoda, a kidney-shaped ciliate common in organic rich conditions, is representative.
Trematoda is a class within the phylum Platyhelminthes. It includes two groups of parasitic flatworms, known as flukes.
A cephalochordate is an animal in the chordate subphylum, Cephalochordata. They are commonly called Amphioxus or lancelets. Cephalochordates possess 5 synapomorphies, or primary characteristics, that all chordates have at some point during their larval or adulthood stages. These 5 synapomorphies include a notochord, dorsal hollow nerve cord, endostyle, pharyngeal slits, and a post-anal tail . The fine structure of the cephalochordate notochord is best known for the Bahamas lancelet, Asymmetron lucayanum. Cephalochordates are represented in modern oceans by the Amphioxiformes and are commonly found in warm temperate and tropical seas worldwide. With the presence of a notochord, adult amphioxus are able to swim and tolerate the tides of coastal environments, but they are most likely to be found within the sediment of these communities.
The prostomium is the cephalized first body segment in an annelid worm's body at the anterior end. It is in front of the mouth, being usually a small shelf- or lip-like extension over the dorsal side of the mouth. The prostomium together with the peristomium, which includes the mouth and pharynx, make up the annelid head.
Articulata are the only extant subclass of the class Crinoidea. The group includes "sea lilies" and "feather stars". The Articulata are differentiated from the extinct subclasses by their lack of an anal plate in the adult stage and the presence of an entoneural system.
Nassula is a genus of unicellular ciliates, belonging to the class Nassophorea. Like other members of the class, Nassula possesses a basket-like feeding apparatus made up of cytopharyngeal rods (nematodesmata), which are themselves composed of closely packed microtubules. Nassula use this structure to ingest filamentous cyanobacteria, drawing individual strands of blue-green algae through the cytopharynx and into the body of the cell, where they are digested. As the algae are broken down, they can take on a variety of bright colours, which give Nassula a distinctive, variegated appearance under the microscope.
Karyorelictea is a class of ciliates in the subphylum Postciliodesmatophora. Most species are members of the microbenthos community, that is, microscopic organisms found in the marine interstitial habitat, though one genus, Loxodes, is found in freshwater.
Loxodes is a genus of karyorelictean ciliates, belonging to family Loxodidae. It is the only known karyorelictean ciliate that lives in freshwater habitats.
The ciliates are a group of protozoans characterized by the presence of hair-like organelles called cilia, which are identical in structure to eukaryotic flagella, but are in general shorter and present in much larger numbers, with a different undulating pattern than flagella. Cilia occur in all members of the group and are variously used in swimming, crawling, attachment, feeding, and sensation.
A mixotroph is an organism that can use a mix of different sources of energy and carbon, instead of having a single trophic mode on the continuum from complete autotrophy at one end to heterotrophy at the other. It is estimated that mixotrophs comprise more than half of all microscopic plankton. There are two types of eukaryotic mixotrophs: those with their own chloroplasts, and those with endosymbionts—and those that acquire them through kleptoplasty or by enslaving the entire phototrophic cell.
Armophorea is a class of ciliates in the subphylum Intramacronucleata. . It was first resolved in 2004 and comprises three orders: Metopida, Clevelandellida, and Armophorida. Previously members of this class were thought to be heterotrichs because of similarities in morphology, most notably a characteristic dense arrangement of cilia surrounding their oral structures. However, the development of genetic tools and subsequent incorporation of DNA sequence information has led to major revisions in the evolutionary relationships of many protists, including ciliates. Metopids, clevelandellids, and armophorids were grouped into this class based on similarities in their small subunit rRNA sequences, making them one of two so-called "riboclasses" of ciliates, however, recent analyses suggest that Armophorida may not be related to the other two orders.
Tracheloraphis is a genus of ciliates in the family Trachelocercidae.
Parablepharismea is a class of free-living marine and brackish anaerobic ciliates that form a major clade of obligate anaerobes within the SAL group, together with the classes Muranotrichea and Armophorea.
Halteria, sometimes referred to as the jumping oligotrich, is a genus of common planktonic ciliates that are found in many freshwater environments. Halteria are easy to locate due to their abundance and distinctive behaviour with observations of Halteria potentially dating back to the 17th century and the discovery of microorganisms. Over time more has been established about their morphology and behavior, which has led to many changes in terms of classification.
