''Cephaleuros'' is a genus of thalloid

green algae The green algae (: green alga) are a group of chlorophyll-containing autotrophic eukaryotes consisting of the phylum Prasinodermophyta and its unnamed sister group that contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ...

comprising approximately 14 species. Its common name is red rust. ''Cephaleuros'' species are parasitic algae which grow within

vascular plant Vascular plants (), also called tracheophytes (, ) or collectively tracheophyta (; ), are plants that have lignin, lignified tissues (the xylem) for conducting water and minerals throughout the plant. They also have a specialized non-lignified Ti ...

s, typically within the subtropics or tropics.

Description

''Cephaleuros'' forms velvet-like spots up to 10 mm or more in diameter; these consists of a filamentous or pseudoparenchymatous, prostrate thallus and an erect system of filaments which branch from the prostrate thallus. The organism grows below the

cuticle A cuticle (), or cuticula, is any of a variety of tough but flexible, non-mineral outer coverings of an organism, or parts of an organism, that provide protection. Various types of "cuticle" are non- homologous, differing in their origin, structu ...

epidermis The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and Subcutaneous tissue, hypodermis. The epidermal layer provides a barrier to infection from environmental pathogens and regulates the ...

of the host plant. Filaments branch dichotomously or pinnately, forming roughly circular thalli. Cells contain a single nucleus and a irregularly reticulate, parietal

chloroplast A chloroplast () is a type of membrane-bound organelle, organelle known as a plastid that conducts photosynthesis mostly in plant cell, plant and algae, algal cells. Chloroplasts have a high concentration of chlorophyll pigments which captur ...

with no pyrenoids. The cytoplasm often contains accumulations of

carotenoid Carotenoids () are yellow, orange, and red organic pigments that are produced by plants and algae, as well as several bacteria, archaea, and fungi. Carotenoids give the characteristic color to pumpkins, carrots, parsnips, corn, tomatoes, cana ...

pigments, giving the thallus an orange-red color.

Identification

''Cephaleuros'' is often confused with non-algal taxa, since the fuzzy reddish spots are reminiscent of rust disease. For species identification, the most important morphological characteristics are the thallus growth habit (filamentous or pseudoparenchymatous, location within the host plant cell), morphology of reproductive structures, and the kind of lesions prodduced (which are distinctive for a few species). Chromosome counts may also be useful.

Reproduction

''Cephaleuros'' reproduces both asexually and sexually. Asexual reproduction occurs via the formation of zoospores, which are formed on zoosporangia on fertile branches. The fertile branches consist of a enlarged "head cell", and multiple "sporangiate laterals" which themselves consist of a short suffultory cell and a round, enlarged zoosporangium. Zoosporangia produce 8 to 64

zoospore A zoospore is a motile asexual spore that uses a flagellum for locomotion in aqueous or moist environments. Also called a swarm spore, these spores are created by some protists, bacteria, and fungi to propagate themselves. Certain zoospores are ...

s. The zoospores have four equal flagella, and are released when the zoosporangia become wet. Sexual reproduction is

isogamous Isogamy is a form of sexual reproduction that involves gametes of the same morphology (indistinguishable in shape and size), and is found in most unicellular eukaryotes. Because both gametes look alike, they generally cannot be classified as ma ...

, with gametangia developing from lateral and terminal thallus cells. Eight to 64 gametes are produced within a gametangium; the gametes are biflagellate and somewhat smaller than their zoospore counterparts. They fuse outside of the gametangia if sufficient moisture is present, otherwise they fuse within the gametangia. The resulting

zygote A zygote (; , ) is a eukaryote, eukaryotic cell (biology), cell formed by a fertilization event between two gametes. The zygote's genome is a combination of the DNA in each gamete, and contains all of the genetic information of a new individ ...

s reportedly develope into dwarf sporophytes which then produces spores through

meiosis Meiosis () is a special type of cell division of germ cells in sexually-reproducing organisms that produces the gametes, the sperm or egg cells. It involves two rounds of division that ultimately result in four cells, each with only one c ...

. However, this heteromorphic alternation of generations is not fully documented and may differ between species.

Fossil record

''Cephaleuros'' has been recorded from the

fossil record A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved ...

once, as ''Pelicothallos villosus'' (originally thought to be a fungus, and now recognized to be a form of ''Cephaleuros''). This fossil was found within the cuticle of

Myrtaceae Myrtaceae (), the myrtle family, is a family of dicotyledonous plants placed within the order Myrtales. Myrtle, pōhutukawa, bay rum tree, clove, guava, acca (feijoa), allspice, and eucalyptus are some notable members of this group. All ...

leaves in a

Middle Eocene The Eocene ( ) is a geological epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period in the modern Cenozoic Era. The name ''Eocene'' comes from the Ancient Greek (''Ēṓs'', ' Dawn') a ...

deposit in the Claiborne Formation,

Tennessee Tennessee (, ), officially the State of Tennessee, is a landlocked U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders Kentucky to the north, Virginia to the northeast, North Carolina t ...

Parasitism

''Cephaleuros'' is a parasite on

angiosperm Flowering plants are plants that bear flowers and fruits, and form the clade Angiospermae (). The term angiosperm is derived from the Greek words (; 'container, vessel') and (; 'seed'), meaning that the seeds are enclosed within a fruit ...

s, and to a lesser extent

gymnosperm The gymnosperms ( ; ) are a group of woody, perennial Seed plant, seed-producing plants, typically lacking the protective outer covering which surrounds the seeds in flowering plants, that include Pinophyta, conifers, cycads, Ginkgo, and gnetoph ...

s. It is parasitic on some important economic plants of the

tropics The tropics are the regions of Earth surrounding the equator, where the sun may shine directly overhead. This contrasts with the temperate or polar regions of Earth, where the Sun can never be directly overhead. This is because of Earth's ax ...

and

subtropic The subtropical zones or subtropics are geographical and climate zones immediately to the north and south of the tropics. Geographically part of the temperate zones of both hemispheres, they cover the middle latitudes from to approximately 3 ...

s such as

tea Tea is an aromatic beverage prepared by pouring hot or boiling water over cured or fresh leaves of '' Camellia sinensis'', an evergreen shrub native to East Asia which probably originated in the borderlands of south-western China and nor ...

coffee Coffee is a beverage brewed from roasted, ground coffee beans. Darkly colored, bitter, and slightly acidic, coffee has a stimulating effect on humans, primarily due to its caffeine content, but decaffeinated coffee is also commercially a ...

mango A mango is an edible stone fruit produced by the tropical tree '' Mangifera indica''. It originated from the region between northwestern Myanmar, Bangladesh, and northeastern India. ''M. indica'' has been cultivated in South and Southeast As ...

and

guava Guava ( ), also known as the 'guava-pear', is a common tropical fruit cultivated in many tropical and subtropical regions. The common guava '' Psidium guajava'' (lemon guava, apple guava) is a small tree in the myrtle family (Myrtaceae), nativ ...

causing damage limited to the area of algal growth on leaves (algal leaf spot), or killing new shoots, or disfiguring fruit. Spores germinate on plants in the rainy season. It is unclear how ''Cephaleuros'' enters its host plants. Members of the genera may also grow with a

fungus A fungus (: fungi , , , or ; or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and mold (fungus), molds, as well as the more familiar mushrooms. These organisms are classified as one ...

to form a

lichen A lichen ( , ) is a hybrid colony (biology), colony of algae or cyanobacteria living symbiotically among hypha, filaments of multiple fungus species, along with yeasts and bacteria embedded in the cortex or "skin", in a mutualism (biology), m ...

that does not damage the plants. In some cases (such as with '' Strigula smaragdula''), it appears that the fungi surround the algae instead of the plants and extract water and nutrients from the algae; therefore, the fungi could be described as a

hyperparasite A hyperparasite, also known as a metaparasite, is a parasite whose host, often an insect, is also a parasite, often specifically a parasitoid. Hyperparasites are found mainly among the wasp-waisted Apocrita within the Hymenoptera, and in two ot ...

. Most species of ''Cephaleuros'' grow between the cuticle and epidermis of infected plants. A few species grow intercellularly, and these intercellular species cause more damage to host plants.

Species

The species currently recognised are: *'' Cephaleuros biolophus'' *'' Cephaleuros diffusus'' *'' Cephaleuros drouetii'' *'' Cephaleuros endophyticus'' *'' Cephaleuros expansa'' *'' Cephaleuros henningsii'' *'' Cephaleuros karstenii'' *'' Cephaleuros lagerheimii'' *'' Cephaleuros minimus'' *'' Cephaleuros parasiticus'' *'' Cephaleuros pilosa'' *'' Cephaleuros solutus'' *'' Cephaleuros tumidae-setae'' *'' Cephaleuros virescens''

References

External links

Images
f ''Cephaleuros'' at

Algaebase AlgaeBase is a global species database of information on all groups of algae, both seaweed, marine and freshwater algae, freshwater, as well as sea-grass. History AlgaeBase began in March 1996, founded by Michael D. Guiry, Michael Guiry. Text ...

{{Taxonbar, from=Q5063258 Trentepohliaceae Ulvophyceae genera