Bangia
Encyclopedia
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 plants are attached by down-growing rhizoid
s, usually in dense purple-black to rust-colored clumps. The chloroplasts of Bangia, like others in the division Rhodophyta, contain chlorophyll a
and sometimes chlorophyll d
, as well as accessory pigments such as phycobilin
pigments and xanthophyll
s. Depending on the relative proportions of these pigments and the light conditions, the overall color of the plant can range from green to red to purple to grey; however, the red pigment, phycoerythrin
, is usually dominant.
All sexual reproduction in rhodophytes is oogamous. Carposporangia are formed through direct division of the zygote. Carpospores germinate to form the diploid filamentous conchocelis phase, which produces conchosporangial branches bearing conchosporangia, each containing a single conchospore. These conchospores then germinate to form gametophytes. During the "conchocelis stage", the plants can also self-replicate using monospores. The monospores develop directly into new plants and may germinate within the sporangia.
). Because these fossils have multiseriate filaments derived by longitudinal divisions from uniseriate filaments, taxonomists believe that these fossils are related to Bangia. This resolution distinguished these fossils from other pre-Ediacaran eukaryotes and contributes to evidence that multicellular algae diversified before the Ediacaran radiation of large animals.
, Erythrotrichia and Erythrocladia.
Freshwater
Fresh water is naturally occurring water on the Earth's surface in ice sheets, ice caps, glaciers, bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifers and underground streams. Fresh water is generally characterized by having low concentrations of dissolved salts and...
habitats. Bangia has small thalli with rapid growth and high reproductive output, and exhibits behavior characteristic of r-selected species. The plants are attached by down-growing rhizoid
Rhizoid
Rhizoids are thread-like growths from the base or bottom of a plant, found mainly in lower groups such as algae, fungi, bryophytes and pteridophytes, that function like roots of higher plants ....
s, usually in dense purple-black to rust-colored clumps. The chloroplasts of Bangia, like others in the division Rhodophyta, contain chlorophyll a
Chlorophyll a
Chlorophyll a is a specific form of chlorophyll used in oxygenic photosynthesis. It absorbs most energy from wavelengths of violet-blue and orange-red light. This photosynthetic pigment is essential for photosynthesis in eukaryotes, cyanobacteria and prochlorophytes because of its role as primary...
and sometimes chlorophyll d
Chlorophyll d
Chlorophyll d is a form of chlorophyll, identified in 1996. It absorbs far-red light, at 710 nm wavelength, just outside the optical range. Acaryochloris marina, a bacterium, uses it for photosynthesis....
, as well as accessory pigments such as phycobilin
Phycobilin
Phycobilins are chromophores found in cyanobacteria and in the chloroplasts of red algae, glaucophytes and some cryptomonads...
pigments and xanthophyll
Xanthophyll
Xanthophylls are yellow pigments that form one of two major divisions of the carotenoid group. The name is from Greek xanthos + phyllon , due to their formation of the yellow band seen in early chromatography of leaf pigments...
s. Depending on the relative proportions of these pigments and the light conditions, the overall color of the plant can range from green to red to purple to grey; however, the red pigment, phycoerythrin
Phycoerythrin
Phycoerythrin is a red protein from the light-harvesting phycobiliprotein family, present in cyanobacteria, red algae and cryptomonads.Like all phycobiliproteins, phycoerythrin is composed of a protein part, organised in a hexameric structure of alpha and beta chains, covalently binding...
, is usually dominant.
Description
Bangia is a red alga that arises from a discoid holdfast and short stipe consisting of the extensions of rhizoidal cells. Bangia has unbranched, erect thalli forming initially uniseriate filaments becoming multiseriate at maturity. The plant is composed of filiform, unbranched cylinders of cells embedded in a firm gelatinous matrix. The cell contains a stellate chloroplast with prominent pyrenoid, as well as single thylakoids (characteristic of division Rhodophyta). The growth of Bangia is diffuse and intercalary, and each cell is quadrate to rectangular in shape. Primary pitt connections are absent in all but the conchocelis stage.Distribution
Bangia grows in freshwater or in marine habitats, usually forming dense clumps or mats, and occur throughout the intertidal area and subtidally to the maximum depth at which benthic algae occur. The plants are usually attached to a solid substratum (rock or shell), but can also occur as epiphytes attached to other algae.Ecology
Marine populations of Bangia in the Atlantic Ocean are common food for the periwinkle Littorina littorea.Reproduction
Species of Bangia undergo a heteromorphic alternation of generation life cycle in which the haploid generation is dominant. Reproduction can be either sexual or asexual; sexual plants occur mainly during the cold season of the year, while at other times the thalli often bear monosporangia only. Bangia, like all Rhodophytes, lack motile sperm and so depend upon water currents to transport their gametes to the trichogyne (receptive area of the female gamete or carpogonium).All sexual reproduction in rhodophytes is oogamous. Carposporangia are formed through direct division of the zygote. Carpospores germinate to form the diploid filamentous conchocelis phase, which produces conchosporangial branches bearing conchosporangia, each containing a single conchospore. These conchospores then germinate to form gametophytes. During the "conchocelis stage", the plants can also self-replicate using monospores. The monospores develop directly into new plants and may germinate within the sporangia.
Scientific interest
Silicified peritidal carbonate rocks have been found off Somerset Island, arctic Canada, which contain fossils of well-preserved bangiophyte red algae (BangiomorphaBangiomorpha
Bangiomorpha pubescens is a red alga. It is the first known sexually reproducing organism. A multicellular fossil of Bangiomorpha pubescens was recovered from Arctic Canada that strongly resembles the modern red alga Bangia despite occurring in rocks dating to ....
). Because these fossils have multiseriate filaments derived by longitudinal divisions from uniseriate filaments, taxonomists believe that these fossils are related to Bangia. This resolution distinguished these fossils from other pre-Ediacaran eukaryotes and contributes to evidence that multicellular algae diversified before the Ediacaran radiation of large animals.
Related genera
Bangiadulcis and Pseudobangia were previously thought to be part of the genus Bangia. However, it has since been discovered that these plants can only undergo asexual reproduction through the formation of archaeosporangia. In fact, sexual reproduction has so far only been recorded in Bangia, PorphyraPorphyra
Porphyra is a foliose red algal genus of laver, comprising approximately 70 species. It grows in the intertidal zone, typically between the upper intertidal zone and the splash zone in cold waters of temperate oceans. In East Asia, it is used to produce the sea vegetable products nori and gim ,...
, Erythrotrichia and Erythrocladia.