''Nephromyces'' is a genus of

apicomplexa The Apicomplexa (also called Apicomplexia) are a large phylum of parasitic alveolates. Most of them possess a unique form of organelle that comprises a type of non-photosynthetic plastid called an apicoplast, and an apical complex structure. T ...

ns that are symbionts of the

ascidian Ascidiacea, commonly known as the ascidians, tunicates (in part), and sea squirts (in part), is a polyphyletic class in the subphylum Tunicata of sac-like marine invertebrate filter feeders. Ascidians are characterized by a tough outer "tunic" m ...

genus ''

Molgula ''Molgula'', or sea grapes, are very common, globular, individual marine tunicates roughly the size of grapes.Sanamyan, K.; Monniot, C. (2012). Molgula Forbes, 1848. In: Noa Shenkar, Arjan Gittenberger, Gretchen Lambert, Marc Rius, Rosana Moreira ...

'' (sea grapes).

Systematics

''Nephromyces'' was first described in 1888 by

Alfred Mathieu Giard Alfred Mathieu Giard (8 August 1846 – 8 August 1908) was a French zoologist born in Valenciennes. Biography In 1867 he began his studies of natural sciences at the École Normale Supérieure, followed by work as ''préparateur de zoologie'' a ...

as a

chytrid fungus Chytridiomycota are a division of zoosporic organisms in the kingdom Fungi, informally known as chytrids. The name is derived from the Ancient Greek ('), meaning "little pot", describing the structure containing unreleased zoöspores. Chytrid ...

, because of its filamentous cells. He formally named three species, each corresponding to a different species of the host animal.

Molecular phylogenetics Molecular phylogenetics () is the branch of phylogeny that analyzes genetic, hereditary molecular differences, predominantly in DNA sequences, to gain information on an organism's evolutionary relationships. From these analyses, it is possible to ...

later showed that ''Nephromyces'' are not actually fungi, but instead constitute a group within the

Apicomplexa The Apicomplexa (also called Apicomplexia) are a large phylum of parasitic alveolates. Most of them possess a unique form of organelle that comprises a type of non-photosynthetic plastid called an apicoplast, and an apical complex structure. T ...

that is related to the Piroplasmida.

Species of ''Nephromyces''

* ''Nephromyces molgularum'' Giard, 1888 * ''Nephromyces rosocovitanus'' Giard, 1888 * ''Nephromyces sorokini'' Giard, 1888

Description

''Nephromyces'' is found in the lumen of the renal sac of its host animals. The renal sac is a closed, fluid-filled structure that is derived from the

epicardium The pericardium, also called pericardial sac, is a double-walled sac containing the heart and the roots of the great vessels. It has two layers, an outer layer made of strong connective tissue (fibrous pericardium), and an inner layer made of ...

during development. There are different cell types (at least seven in ''Nephromyces'' from ''

Molgula manhattensis ''Molgula manhattensis'', commonly known as "sea grapes", is a species of ascidian commonly found along the East Coast and Gulf Coast region of the United States. Although it is native to this region, it has been introduced to other areas of Eur ...

'') which appear to be different life cycle stages, as the different types appear in a consistent sequence after initial infection of the host animal. However, in a mature infection, different stages simultaneously co-occur in the same host individual. They include filaments (trophic stages), spores, motile but non-flagellated cells, and biflagellated swarmer cells. The non-flagellated motile cells resemble the

sporozoites Apicomplexans, a group of intracellular parasites, have life cycle stages that allow them to survive the wide variety of environments they are exposed to during their complex life cycle. Each stage in the life cycle of an apicomplexan organism i ...

of other apicomplexans, while the spores contain structures that resemble the rhoptries of the

apical complex The Apicomplexa (also called Apicomplexia) are a large phylum of parasitic Alveolata, alveolates. Most of them possess a unique form of organelle that comprises a type of non-photosynthetic plastid called an apicoplast, and an apical complex stru ...

, another typical apicomplexan feature.

Symbiosis

''Nephromyces'' is specific to the family Molgulidae, and has been found in species of ''

'' and at least one other molgulid genus, '' Bostrichobranchus'' (''B. pilularis''). Every wild-collected adult ''Molgula'' animal examined has been found to contain ''Nephromyces'', suggesting that it is a beneficial symbiont rather than a parasite; this makes ''Nephromyces'' an exception among apicomplexans, which are usually parasitic on their animal hosts. However, animals without ''Nephromyces'' can be obtained by spawning and raising them in filtered seawater. These symbiont-free animals have been used to study the ''Nephromyces'' life cycle. ''Nephromyces'' is released into surrounding seawater when its host dies, and cells of ''Nephromyces'' can remain alive and infective for at least 29 days outside of a host. The renal sac organ where ''Nephromyces'' lives contains high concentrations of

urate Uric acid is a heterocyclic compound of carbon, nitrogen, oxygen, and hydrogen with the formula C5H4N4O3. It forms ions and salts known as urates and acid urates, such as ammonium acid urate. Uric acid is a product of the metabolic breakdown o ...

, a nitrogenous waste product. Activity of

urate oxidase The enzyme urate oxidase (UO), uricase or factor-independent urate hydroxylase, absent in humans, catalyzes the oxidation of uric acid to 5-hydroxyisourate: :Uric acid + O2 + H2O → 5-hydroxyisourate + H2O2 : 5-hydroxyisourate + H2O → al ...

, an enzyme that breaks down urate, has been found in ''Nephromyces'' cells, hence they may be using the waste products from their host animal as a nitrogen source for themselves. Intracellular bacteria have been found within cells of ''Nephromyces'' from ''

'' and '' M. occidentalis'', making this a symbiosis within a symbiosis.

References

{{Taxonbar, from=Q21445659 Apicomplexa genera Symbiosis