''Pythium porphyrae'', is a

parasitic Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson has c ...

species of

oomycete Oomycota forms a distinct phylogenetic lineage of fungus-like eukaryotic microorganisms, called oomycetes (). They are filamentous and heterotrophic, and can reproduce both sexually and asexually. Sexual reproduction of an oospore is the resul ...

in the family

Pythiaceae Pythiaceae is a family of water moulds. The family includes serious plant and animal pathogens in the genus '' Pythium''. The family was circumscribed by German mycologist Joseph Schröter in 1893. Lifecycle *Live on land ( terrestrial), and in ...

. It is the cause of red rot disease or red wasting disease, also called ' () in

Japanese Japanese may refer to: * Something from or related to Japan, an island country in East Asia * Japanese language, spoken mainly in Japan * Japanese people, the ethnic group that identifies with Japan through ancestry or culture ** Japanese diaspor ...

. The

specific epithet In taxonomy, binomial nomenclature ("two-term naming system"), also called nomenclature ("two-name naming system") or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, bot ...

''porphyrae'' () stems from the genus of one of its common hosts, ''

Porphyra ''Porphyra'' is a genus of coldwater seaweeds that grow in cold, shallow seawater. More specifically, it belongs to red algae phylum of laver species (from which comes laverbread), comprising approximately 70 species.Brodie, J.A. and Irvine, ...

'', and the purple-red color of the lesions on the

thallus Thallus (plural: thalli), from Latinized Greek (), meaning "a green shoot" or "twig", is the vegetative tissue of some organisms in diverse groups such as algae, fungi, some liverworts, lichens, and the Myxogastria. Many of these organisms wer ...

of the host. However, many of its hosts have been moved from the genus ''Porphyra'' to ''

Pyropia ''Pyropia'' is a genus of red algae eaweedin the family Bangiaceae. It is found around the world in intertidal zones and shallow water. The genus has folding frond-like blades which are either red, brown or green. Some ''Pyropia'' species are u ...

''.

Economic impact

''Pythium porphyrae'' can destroy an entire crop of

nori Nori is a dried edible seaweed used in Japanese cuisine, made from species of the red algae genus ''Pyropia'', including ''P. yezonesis'' and '' P. tenera''. It has a strong and distinctive flavor, and is often used to wrap rolls of sushi or '' ...

within 3 weeks.ARASAKI, S. (1962). Studies on the artificial culture of Porphyra tenera Kjellm. 111. On the red wasting disease of Porphyra, especially on the physiology of the causal fungus Pythium sp.nov. n Japanese, English summary.Journal of the Agricultural Laboratory, Abiko, Japan. Central Research Institute of Electric Power Industry 3, 87-93 It prefers low

salinity Salinity () is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal ...

and warm water (24-28 °C).SUTO, S., SAITO, Y., AKIYAMA, K. & UMEBAYASHI, 0. (1972). Text Book of Diseases and their Symptoms in Porphyra. n Japanese.Contribution E, Number I 8 of Tokai Regional Fisheries Research Laboratory, Japan. 37 pp.SAKURAI, Y., AKIYAMA, K. & SATO, S. (1974). On the formation and the discharge of zoospores of Pythium porphyrae in experimental conditions. n Japanese, English summary.Bulletin of the Tohoku Regional Fisheries Research Laboratory (33), I 19-27. It will only grow in the 15-35 °C range. Mild winters correlate with higher infestations and lower crop yields, possibly due to decreased temperatures inducing the development of sex organs in the oomycete. Losses can be combated by destroying diseased fronds and exposing thalli to the air for 3–4 hours daily. The

oospore An oospore is a thick-walled sexual spore that develops from a fertilized oosphere in some algae, fungi, and oomycetes. They are believed to have evolved either through the fusion of two species or the chemically-induced stimulation of mycelia, ...

s can be spread in contaminated organic matter and the

sporangia A sporangium (; from Late Latin, ) is an enclosure in which spores are formed. It can be composed of a single cell or can be multicellular. Virtually all plants, fungi, and many other lineages form sporangia at some point in their life cy ...

can spread through the water.

Description

''Pythium porphyrae'' has a

mycelial Mycelium (plural mycelia) is a root-like structure of a fungus consisting of a mass of branching, thread-like hyphae. Fungal colonies composed of mycelium are found in and on soil and many other substrates. A typical single spore germinates ...

thallus that is eucarpic, meaning only part of the thallus turns into

. It is primarily a

facultative parasite A facultative parasite is an organism that may resort to parasitic activity, but does not absolutely rely on any host for completion of its life cycle. Examples of facultative parasitism occur among many species of fungi, such as family members ...

of algae, but can also be

saprobic Saprotrophic nutrition or lysotrophic nutrition is a process of chemoheterotrophic extracellular digestion involved in the processing of decayed (dead or waste) organic matter. It occurs in saprotrophs, and is most often associated with fungi ( ...

. Its

hypha A hypha (; ) is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium. Structure A hypha consists of one or ...

e can grow up to 4.5 µm wide, and are not

septate In biology, a septum (Latin for ''something that encloses''; plural septa) is a wall, dividing a cavity or structure into smaller ones. A cavity or structure divided in this way may be referred to as septate. Examples Human anatomy * Interatr ...

. On algae, the hyphae will extend through the cell wall. It does not have

haustoria In botany and mycology, a haustorium (plural haustoria) is a rootlike structure that grows into or around another structure to absorb water or nutrients. For example, in mistletoe or members of the broomrape family, the structure penetrates t ...

not

chlamydospore A chlamydospore is the thick-walled large resting spore of several kinds of fungi, including Ascomycota such as '' Candida'', Basidiomycota such as ''Panus'', and various Mortierellales species. It is the life-stage which survives in unfavourable c ...

s. The appressoria are club-shaped. It has sporangia that are unbranched, filamentous, and non-inflated, typically forming 6-17

zoospore A zoospore is a motile asexual spore that uses a flagellum for locomotion. Also called a swarm spore, these spores are created by some protists, bacteria, and fungi to propagate themselves. Diversity Flagella types Zoospores may possess one or mo ...

s per vesicle. Encysted zoospores are 8-12 µm in diameter. Hyphal swellings are

intercalary Intercalation may refer to: *Intercalation (chemistry), insertion of a molecule (or ion) into layered solids such as graphite *Intercalation (timekeeping), insertion of a leap day, week or month into some calendar years to make the calendar follo ...

and

globose A sphere () is a geometrical object that is a three-dimensional analogue to a two-dimensional circle. A sphere is the set of points that are all at the same distance from a given point in three-dimensional space.. That given point is the ce ...

, from 12-28 µm in diameter.

Oogonia An oogonium (plural oogonia) is a small diploid cell which, upon maturation, forms a primordial follicle in a female fetus or the female (haploid or diploid) gametangium of certain thallophytes. In the mammalian fetus Oogonia are formed in larg ...

average 17 µm in diameter and are also intercalary and globose, but rarely are terminal. In each oogonium are 1-2

diclinous Plant reproductive morphology is the study of the physical form and structure (the morphology) of those parts of plants directly or indirectly concerned with sexual reproduction. Among all living organisms, flowers, which are the reproductive s ...

antheridia An antheridium is a haploid structure or organ producing and containing male gametes (called ''antherozoids'' or sperm). The plural form is antheridia, and a structure containing one or more antheridia is called an androecium. Androecium is also t ...

coming out far away from the oogonial stalk. The antheridia's cells are

clavate This glossary of entomology describes terms used in the formal study of insect species by entomologists. A–C A synthetic chlorinated hydrocarbon insecticide, toxic to vertebrates. Though i ...

(club shaped) or globose. The antheridia will be

apical Apical means "pertaining to an apex". It may refer to: *Apical ancestor, refers to the last common ancestor of an entire group, such as a species (biology) or a clan (anthropology) *Apical (anatomy), an anatomical term of location for features loc ...

to the oogonial wall. Sometimes there will be two antheridial cells on one stalk. The

yellow Yellow is the color between green and orange on the spectrum of light. It is evoked by light with a dominant wavelength of roughly 575585 nm. It is a primary color in subtractive color systems, used in painting or color printing. In the R ...

ish

s average 15 µm in diameter, have thick (~2 µm) walls, and are plerotic (fill the whole oogonium).

Conidia A conidium ( ; ), sometimes termed an asexual chlamydospore or chlamydoconidium (), is an asexual, non-motile spore of a fungus. The word ''conidium'' comes from the Ancient Greek word for dust, ('). They are also called mitospores due to the ...

are spherical at 8.8-30.8 μm diameter, but rarely produced. ''Pythium porphyrae'' shares many physical traits with '' P. marinum'' and '' P. monospermum'', and appears to be most closely related to '' P. adhaerens''. However it has up to four diclinous antheridia and sometimes two antheridial cells per stalk; ''P. monospermum'' has 1-4 either diclinous or

monoclinous Plant reproductive morphology is the study of the physical form and structure (the Plant morphology, morphology) of those parts of plants directly or indirectly concerned with sexual reproduction. Among all living organisms, flowers, which are t ...

antheridia and ''P. marinum'' has only a single diclinous antheridium. ''P. monospermum'' and ''P. marinum'' also have oogonia terminally on short branches, yet in ''P. porphyrae'' they tent to be intercalary. In a

laboratory A laboratory (; ; colloquially lab) is a facility that provides controlled conditions in which scientific or technological research, experiments, and measurement may be performed. Laboratory services are provided in a variety of settings: physicia ...

it will grow 5 mm per day on seawater-cornmeal agar with low aerial

mycelium Mycelium (plural mycelia) is a root-like structure of a fungus consisting of a mass of branching, thread-like hyphae. Fungal colonies composed of mycelium are found in and on soil and many other substrate (biology), substrates. A typical single ...

and colorless colonies, but will not grow at all on potato-carrot agar.

Ecology

''Pythium porphyrae'' has been found in

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...

Netherlands ) , anthem = ( en, "William of Nassau") , image_map = , map_caption = , subdivision_type = Sovereign state , subdivision_name = Kingdom of the Netherlands , established_title = Before independence , established_date = Spanish Netherl ...

New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...

, and

Korea Korea ( ko, 한국, or , ) is a peninsular region in East Asia. Since 1945, it has been divided at or near the 38th parallel, with North Korea (Democratic People's Republic of Korea) comprising its northern half and South Korea (Republic o ...

, but this range is likely underreported. It has a parasitic relationship with the following

hosts A host is a person responsible for guests at an event or for providing hospitality during it. Host may also refer to: Places *Host, Pennsylvania, a village in Berks County People *Jim Host (born 1937), American businessman *Michel Host ( ...

. Though some species of ''

'' and ''

'' are susceptible to infection in their

gametophytic A gametophyte () is one of the two alternation of generations, alternating multicellular organism, multicellular phases in the life cycles of plants and algae. It is a haploid multicellular organism that develops from a haploid spore that has on ...

phase, they are resistant in their '' Conchocelis'' (

sporophytic A sporophyte () is the diploid multicellular stage in the life cycle of a plant or alga which produces asexual spores. This stage alternates with a multicellular haploid gametophyte phase. Life cycle The sporophyte develops from the zygote pr ...

) phase. *''

Bangia atropurpurea ''Bangia'' is an extant genus of division Rhodophyta that grows in marine or freshwater habitats. ''Bangia'' has small thalli with rapid growth and high reproductive output, and exhibits behavior characteristic of r-selected species. The plan ...

'' *'' Callophyllis adhaerens'' *''

Chondrus crispus ''Chondrus crispus''—commonly called Irish moss or carrageen moss (Irish ''carraigín'', "little rock")—is a species of red algae which grows abundantly along the rocky parts of the Atlantic coast of Europe and North America. In its fresh c ...

'' *'' Gelidium elegans'' *'' Gloiosiphonia capillaris'' *''

Gracilaria ''Gracilaria'' is a genus of red algae (Rhodophyta) notable for its economic importance as an agarophyte, as well as its use as a food for humans and various species of shellfish. Various species within the genus are cultivated among Asia, South ...

'' spp. *'' Grateloupia turuturu'' *'' Griffithsia subcylindrica'' *'' Lomentaria hakodatensis'' *'' Mastocarpus papillatus'' *'' Polyopes affinis'' ('' Carpopeltis affinis'') *'' Polysiphonia morrowii'' *'' Pterocladiella capillacea'' *''

Pyropia cinnamomea ''Pyropia'' is a genus of red algae eaweedin the family Bangiaceae. It is found around the world in intertidal zones and shallow water. The genus has folding frond-like blades which are either red, brown or green. Some ''Pyropia'' species are u ...

'' *''

Pyropia plicata ''Pyropia'' is a genus of red algae eaweedin the family Bangiaceae. It is found around the world in intertidal zones and shallow water. The genus has folding frond-like blades which are either red, brown or green. Some ''Pyropia'' species are us ...

'' *'' Pyropia suborbiculata'' *'' Pyropia tenera'' *'' Pyropia virididentata'' *'' Pyropia yezoensis'' *'' Rhodymenia intricata'' *''

Stylonema alsidii ''Stylonema alsidii'' is a species of marine red algae. The type locality is Trieste in Italy, but it has a worldwide distribution. The species was first described by Giovanni Zanardini in 1840 as ''Bangia alsidii''. Distribution It is one of t ...

'' *'' Wrangelia tanegana''

Taxonomy

A 2005 study concerning a case of

Pythiosis Pythiosis is a rare and deadly tropical disease caused by the oomycete ''Pythium insidiosum''. Long regarded as being caused by a fungus, the causative agent was not discovered until 1987. It occurs most commonly in horses, dogs, and humans, with ...

from a related species ('' P. insidiosum'') indicated that ''P. porphyrae'' is related to '' P. dissotocum'', '' P. myriotylum'', '' P. volutum'', and '' P. vanterpoolii''. In 2004, molecular analysis of ''Pythium'' determined that ''P. porphyrae'' is in "

Clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

A" along with '' P. adhaerens'', '' P. deliense'', '' P. aphanidermatum'', and '' P. monospermum'' Clade A has two clusters, and ''P. porphyrae'' shares one with the species also originating on

algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular mic ...

, ''P. adhaerens''. A 2017 study of ''Pythium'' species in Clade A showed the following

phylogenetic tree A phylogenetic tree (also phylogeny or evolutionary tree Felsenstein J. (2004). ''Inferring Phylogenies'' Sinauer Associates: Sunderland, MA.) is a branching diagram or a tree showing the evolutionary relationships among various biological spec ...

. It further demonstrated that ''P. porphyrae'' and ''P. chondricola'' are the same species. '' P. adhaerens'' may also be conspecific based solely on genetic comparison, but showed a number of physical differences that show it may be a separate but very closely related species.

References

External links