The Oomycetes, or Oomycota, form a distinct phylogenetic lineage of fungus-like eukaryotic microorganisms within the Stramenopiles. They are filamentous and heterotrophic, and can reproduce both sexually and asexually. Sexual reproduction of an oospore is the result of contact between hyphae of male antheridia and female oogonia; these spores can overwinter and are known as resting spores. Asexual reproduction involves the formation of chlamydospores and sporangia, producing motile zoospores. Oomycetes occupy both saprophytic and pathogenic lifestyles, and include some of the most notorious pathogens of plants, causing devastating diseases such as late blight of potato and sudden oak death. One oomycete, the mycoparasite Pythium oligandrum, is used for biocontrol, attacking plant pathogenic fungi. The oomycetes are also often referred to as water molds, although the water-preferring nature which led to that name is not true of most species, which are terrestrial pathogens.
Myxozoa is a subphylum of aquatic cnidarian animals – all obligate parasites. It contains the smallest animals ever known to have lived. Over 2,180 species have been described and some estimates have suggested at least 30,000 undiscovered species. Many have a two-host lifecycle, involving a fish and an annelid worm or a bryozoan. The average size of a myxosporean spore usually ranges from 10 μm to 20 μm, whereas that of a malacosporean spore can be up to 2 mm. Myxozoans can live in both freshwater and marine habitats.
A genetic screen or mutagenesis screen is an experimental technique used to identify and select individuals who possess a phenotype of interest in a mutagenized population. Hence a genetic screen is a type of phenotypic screen. Genetic screens can provide important information on gene function as well as the molecular events that underlie a biological process or pathway. While genome projects have identified an extensive inventory of genes in many different organisms, genetic screens can provide valuable insight as to how those genes function.
The Rhizaria are a diverse and species-rich supergroup of mostly unicellular eukaryotes. Except for the Chlorarachniophytes and three species in the genus Paulinella in the phylum Cercozoa, they are all non-photosynthethic, but many foraminifera and radiolaria have a symbiotic relationship with unicellular algae. A multicellular form, Guttulinopsis vulgaris, a cellular slime mold, has been described. This group was used by Cavalier-Smith in 2002, although the term "Rhizaria" had been long used for clades within the currently recognized taxon. Being described mainly from rDNA sequences, they vary considerably in form, having no clear morphological distinctive characters (synapomorphies), but for the most part they are amoeboids with filose, reticulose, or microtubule-supported pseudopods. In the absence of an apomorphy, the group is ill-defined, and its composition has been very fluid. Some Rhizaria possess mineral exoskeletons, which are in different clades within Rhizaria made out of opal, celestite, or calcite. Certain species can attain sizes of more than a centimeter with some species being able to form cylindrical colonies approximately 1 cm in diameter and greater than 1 m in length. They feed by capturing and engulfing prey with the extensions of their pseudopodia; forms that are symbiotic with unicellular algae contribute significantly to the total primary production of the ocean.
Labyrinthulomycetes (ICBN) or Labyrinthulea (ICZN) is a class of protists that produce a network of filaments or tubes, which serve as tracks for the cells to glide along and absorb nutrients for them. The two main groups are the labyrinthulids and thraustochytrids. They are mostly marine, commonly found as parasites on algae and seagrasses or as decomposers on dead plant material. They also include some parasites of marine invertebrates and mixotrophic species that live in a symbiotic relationship with zoochlorella.
Perkinsus marinus is a species of alveolate belonging to the phylum Perkinsozoa. It is similar to a dinoflagellate. It is known as a prevalent pathogen of oysters, causing massive mortality in oyster populations. The disease it causes is known as dermo or perkinsosis, and is characterized by the degradation of oyster tissues. The genome of this species has been sequenced.
Perkinsus is a genus of alveolates in the phylum Perkinsozoa. The genus was erected in 1978 to better treat its type species, Perkinsus marinus, known formerly as Dermocystidium marinum. These are parasitic protozoans that infect molluscs, at least some of which cause disease and mass mortality. P. marinus is the most notorious, causing the disease perkinsosis, or dermo, in wild and farmed oysters.
The hard clam, also known as the round clam, hard-shellclam, or the quahog, is an edible marine bivalve mollusk that is native to the eastern shores of North America and Central America from Prince Edward Island to the Yucatán Peninsula. It is one of many unrelated edible bivalves that in the United States are frequently referred to simply as clams. Older literature sources may use the systematic name Venus mercenaria; this species is in the family Veneridae, the venus clams.
A xenoma is a growth caused by various protists and fungi, most notably microsporidia. It can occur on numerous organisms; however is predominantly found on fish.
A microbial cyst is a resting or dormant stage of a microorganism, that can be thought of as a state of suspended animation in which the metabolic processes of the cell are slowed and the cell ceases all activities like feeding and locomotion. Many groups of single-celled, microscopic organisms, or microbes, possess the ability to enter this dormant state.
Protozoan infections are parasitic diseases caused by organisms formerly classified in the kingdom Protozoa. These organisms are now classified in the supergroups Excavata, Amoebozoa, Harosa, and Archaeplastida. They are usually contracted by either an insect vector or by contact with an infected substance or surface.
Ranavirus is a genus of viruses in the family Iridoviridae. There are six other genera of viruses within the family Iridoviridae, but Ranavirus is the only one that includes viruses that are infectious to amphibians and reptiles. Additionally, it is one of the three genera within this family which infect teleost fishes, along with Lymphocystivirus and Megalocytivirus.
Dermocystidium is a genus of cyst-forming, eukaryotic fish parasites, the causative agents of dermocystidiosis.
Aeromonas salmonicida is a pathogenic bacterium that severely impacts salmonid populations and other species. It was first discovered in a Bavarian brown trout hatchery by Emmerich and Weibel in 1894. Aeromonas salmonicida's ability to infect a variety of hosts, multiply, and adapt, make it a prime virulent bacterium. A. salmonicida is an etiological agent for furunculosis, a disease that causes sepsis, haemorrhages, muscle lesions, inflammation of the lower intestine, spleen enlargement, and death in freshwater fish populations. It is found worldwide with the exception of South America. The major route of contamination is poor water quality; however, it can also be associated stress factors such as overcrowding, high temperatures, and trauma. Spawning and smolting fish are prime victims of furunculosis due to their immunocompromised state of being.
The genus Labyrinthula is part of the protist group Labyrinthulomycetes and contains thirteen species. The major feature of this genus is the formation of an ectoplasmic net secreted by specialized organelles called bothrosomes which surrounds the colony, which is also used by Labyrinthula for moving. The protist reproduces by zoosporulation as it sets some flagellated spores free from a sporangium. One of the flagella of the zoospores has stiff tripartite hairs (mastigonemes) - the defining characteristic of the stramenopiles.
Amyloodinium ocellatum is a cosmopolitan ectoparasite dinoflagellate of numerous aquatic organisms living in brackish and seawater environments. The dinoflagellate is endemic in temperate and tropical areas, and is capable of successfully adapting to a variety of different environments and to a great number of hosts, having been identified in four phyla of aquatic organisms: Chordata, Arthropoda, Mollusca and Platyhelminthes. Moreover, it is the only dinoflagellate capable of infecting teleosts and elasmobranchs.
Philasterides dicentrarchi is a marine protozoan ciliate that was first identified in 1995 after being isolated from infected European sea bass reared in France. The species was also identified as the causative agent of outbreaks of scuticociliatosis that occurred between summer 1999 and spring 2000 in turbot cultivated in the Atlantic Ocean. Infections caused by P. dicentrarchi have since been observed in turbot reared in both open flow and recirculating production systems. In addition, the ciliate has also been reported to cause infections in other flatfishes, such as the olive flounder in Korea and the fine flounder in Peru, as well as in seadragons, seahorses, and several species of sharks in other parts of the world.
Black spot disease in crustaceans, commonly studied on the edible brachyuran crab Cancer pagurus, is a progressive degradation of the carapace cuticle and expresses itself by discoloration of the carapace. The disease has been observed on a variety of crustacean species including crabs, lobster, and shrimp. This discoloration, black spots on the carapace, chelae, or legs, is the result of melanisation; a defense response to the deterioration of the cuticle. Black nodules have also been observed on the gills, heart, and hepatopancreas of affected individuals, and the presence of the disease is associated with accumulation of material in the lungs and tubular degradation in the hepatopancreas. Simply put, there is a positive correlation between the amount of black spot on the external carapace and decreased function of internal organs. There is some debate surrounding the cause of the disease, with both bacteria and fungi having been implicated as shell disease pathogens. Crustaceans can rid themselves of the diseased carapace by molting, as the severity of the infection is typically mild. However, in older individuals with lower molt occurrences, the disease can persist, and eventually lead to death.
Hennegoides is a genus of cnidarian that is part of the family Myxobolidae.
Thraustochytriidae or Thraustochytriaceae is a family of heterotrophic protists. They are unicellular eukaryotes characterized by round cells that use a cytoplasmic network to feed and anchor to the substrate, with an appearance similar to chytrids.
