| Abstract from DBPedia | Red algae, or Rhodophyta (/roʊˈdɒfɪtə/, /ˌroʊdəˈfaɪtə/; from Ancient Greek ῥόδον (rhódon) 'rose', and φυτόν (phutón) 'plant'), are one of the oldest groups of eukaryotic algae. The Rhodophyta also comprises one of the largest phyla of algae, containing over 7,000 currently recognized species with taxonomic revisions ongoing. The majority of species (6,793) are found in the Florideophyceae (class), and mostly consist of multicellular, marine algae, including many notable seaweeds. Red algae are abundant in marine habitats but relatively rare in freshwaters. Approximately 5% of red algae species occur in freshwater, environments with greater concentrations found in warmer areas. Except for two coastal cave dwelling species in the asexual class Cyanidiophyceae, there are no terrestrial species, which may be due to an evolutionary bottleneck in which the last common ancestor lost about 25% of its core genes and much of its evolutionary plasticity. The red algae form a distinct group characterized by having eukaryotic cells without flagella and centrioles, chloroplasts that lack external endoplasmic reticulum and contain unstacked (stroma) thylakoids, and use phycobiliproteins as accessory pigments, which give them their red color. Red algae store sugars as floridean starch, which is a type of starch that consists of highly branched amylopectin without amylose, as food reserves outside their plastids. Most red algae are also multicellular, macroscopic, marine, and reproduce sexually. The red algal life history is typically an alternation of generations that may have three generations rather than two.The coralline algae, which secrete calcium carbonate and play a major role in building coral reefs, belong here. Red algae such as dulse (Palmaria palmata) and laver (nori/gim) are a traditional part of European and Asian cuisines and are used to make other products such as agar, carrageenans and other food additives.紅藻（こうそう） (英: red algae) は、植物界またはアーケプラスチダ (古色素体類) の1門である紅色植物門 (または紅藻植物門、学名: Rhodophyta) のこと、またはこれに属する藻類のことである。7,000種以上が知られ、7綱ほどに分けられている。。 多くは多細胞性であり (上図)、細胞間にピットプラグとよばれる特異な構造がある。ただし、単細胞性の種もいる (下図)。細胞壁には多量のガラクタンが含まれ、また石灰化するものもいる。葉緑体は2枚の膜で包まれ、ふつう赤い光合成色素タンパク質であるフィコエリスリンを多くもつため、その名の通り赤い色をしている (上図)。しかしフィコエリスリンを欠き、青緑色をした種もいる (下図)。貯蔵多糖はα-グルカンであり、細胞質基質中に貯蔵される。また大きな特徴として、生活環を通じて鞭毛や中心小体もたないことが挙げられる。有性生殖が知られるものは、造果器（卵）と不動精子によるを行い、単相の配偶体と複相の胞子体の間で世代交代を行う。 多くは沿岸岩礁域に生育しており、海藻として最も種数が多い生物群は紅藻 (特に真正紅藻) である。また、淡水域や温泉に分布する種も知られている。食用 (海苔、ダルス、フノリ類など) や増粘多糖類（寒天、カラギーナン) の原料とされる有用な藻類を多く含む。 (Source: http://dbpedia.org/resource/Red_algae) |
