| Sphacelaria | |
|---|---|
Scientific classification  | |
| Domain: | Eukaryota |
| Clade: | Diaphoretickes |
| Clade: | SAR |
| Clade: | Stramenopiles |
| Phylum: | Gyrista |
| Subphylum: | Ochrophytina |
| Class: | Phaeophyceae |
| Order: | Sphacelariales |
| Family: | Sphacelariaceae |
| Genus: | Sphacelaria H.C.Lyngbye, 1818 |
Sphacelaria is a genus of brown macroalgae (or seaweed) in the family Sphacelariaceae. [1] [2]
The genus and its type species (Sphacelaria reticulata) were briefly described by Hans Christian Lyngbye in Florae Danicae in 1818. [3] [4] At the time of publication, such brief descriptions were considered to be valid by virtue of descriptio generico-specifica; [4] Lyngbye immediately added nine more species to the genus in 1819. [5] Recent studies, however have revealed that this genus is polyphyletic, with the type species forming a separate clade with from the rest of the genus—in addition, it was also observed that S. reticulata does not exhibit the key morphological characteristics of the genus. [6] Thus, it has been proposed to change the type species into S. cirrosa, one of the most widespread species, to conserve the genus name. [7] Dr. Willem F. Prud’homme van Reine (1941–2020) was the foremost expert on Sphacelaria taxonomy [8] and has contributed to the clarification and naming of the 37 confirmed species. [1]
Sphacelaria is mainly characterized by the blackening of their cell walls when treated with bleach, polystichous (parenchymatous) filamentous thallus, hemiblastic branching (i.e. laterals arise from the secondary), and leptocaulus growth (i.e. uniform size of filaments, such as their mature segments have almost the same diameter as their apical ones); moreover majority of the species also have specialized branchlets for vegetative reproduction called propagules. [4] [9] [10] [6] Delineation of Sphacelaria species have been traditionally based on morphological differences, especially the variation among the propagule shape, cell dimensions, and cell arrangement of the propagules. [4] In terms of cellular ultrastructure, Sphacelaria cells contain discoid chloroplasts and do not have pyrenoids. [1]
Sphacelaria is a cosmopolitan genus with a majority of the species found in temperate regions [9] but representatives also thrive in the tropics up to the arctic and antarctic areas. [1] Species from this genus are mainly marine, however, freshwater species have been found in USA (S. lacustris) [11] and China (S.fluviatilis). [12]
Sphacelaria species are epiphytic and/or epilithic in nature, they form filamentous tufts or mats on the surfaces they have reclaimed and are normally found on the intertidal to shallow subtidal. [1]
Members of this genus exhibit isomorphic (i.e., the gametophyte (N) and sporophyte (2N) stage are morphologically similar) and diplohaplontic [i.e., both gametophyte (N) and sporophyte (2N) generations are free-living and equally distinct bodies but only differ in chromosome number and strategy] life cycle with isogamy (i.e., gametes with the same size and form) or anisogamy (i.e., gametes with different size and form). [4] [1] Culture studies have revealed that the reproductive strategy of Sphacelaria species are mainly dictated by the temperature, wherein propagule formation is favored during warmer seasons while sexual reproduction (i.e., formation of plurilocular and unilocular gametangia /zoidangia) occur when temperatures drop; in addition, daylength exposure is believed to contribute to the production of propagules and consequent inhibition of gametogenesis. [13] [14]
This genus is neither commercially nor traditionally cultivated and harvested.
Sphacelaria has been known to contain several natural products such as carotene, chlorophyll a, and fucoxanthin (the pigment responsible for the brown color of phaeophycean seaweeds). [2] Furthermore, they also contain sulfated polysaccharides in the form of xylogalactofucan and alginic acid which have shown to have antiviral properties against the herpes simplex virus type 1 (HSV-1). [15]
This genus has been used for plant morphogenesis studies, [16] environmental stressors research, [17] and much of the industry interest on Sphacelaria revolves around its easy protoplast production which has implications in cellular studies involving expression profiling, RNA sequencing, and transcriptomics. [18]
Phycology is the scientific study of algae. Also known as algology, phycology is a branch of life science.
Brown algae are a large group of multicellular algae comprising the class Phaeophyceae. They include many seaweeds located in colder waters of the Northern Hemisphere. Brown algae are the major seaweeds of the temperate and polar regions. Many brown algae, such as members of the order Fucales, commonly grow along rocky seashores. Most brown algae live in marine environments, where they play an important role both as food and as a potential habitat. For instance, Macrocystis, a kelp of the order Laminariales, may reach 60 m (200 ft) in length and forms prominent underwater kelp forests that contain a high level of biodiversity. Another example is Sargassum, which creates unique floating mats of seaweed in the tropical waters of the Sargasso Sea that serve as the habitats for many species. Some members of the class, such as kelps, are used by humans as food.
Caulerpa is a genus of seaweeds in the family Caulerpaceae. They are unusual because they consist of only one cell with many nuclei, making them among the biggest single cells in the world.
Macrocystis is a monospecific genus of kelp with all species now synonymous with Macrocystis pyrifera. It is commonly known as giant kelp or bladder kelp. This genus contains the largest of all the Phaeophyceae or brown algae. Macrocystis has pneumatocysts at the base of its blades. Sporophytes are perennial and the individual may live for up to three years; stipes/fronds within a whole individual undergo senescence, where each frond may persist for approximately 100 days. The genus is found widely in subtropical, temperate, and sub-Antarctic oceans of the Southern Hemisphere and in the northeast Pacific. Macrocystis is often a major component of temperate kelp forests.
Leathesia marina (Lyngbye) Decaisne, 1842, previously known as Leathesia difformis Areschoug, 1847, commonly known as the sea cauliflower the sea potato, and brown brains is a species of littoral brown algae in the class Phaeophyceae and the order Ectocarpales, which is commonly attached to other seaweeds and sometimes rocks. When young, the organism is solid but as it matures it becomes hollow and somewhat convoluted and has the appearance of a small leathery brown bag about the same size as a tennis ball. The texture is rubbery and the outer surface smooth.
Cystoseira is a genus of brown algae in the order Fucales.
Colpomenia is a genus of brown macroalgae in the family Scytosiphonaceae.
Chlainomonas is a genus of algae in the family Chlamydomonadaceae. They are found in freshwater habitats or on snow, where they are one of the main algae responsible for causing watermelon snow.
Durvillaea is a genus of large brown algae in the monotypic family Durvillaeaceae. All members of the genus are found in the southern hemisphere, including Australia, New Zealand, South America, and various subantarctic islands. Durvillaea, commonly known as southern bull kelps, occur on rocky, wave-exposed shorelines and provide a habitat for numerous intertidal organisms. Many species exhibit a honeycomb-like structure in their fronds that provides buoyancy, which allows individuals detached from substrates to raft alive at sea, permitting dispersal for hundreds of days over thousands of kilometres. Durvillaea species have been used for clothing, tools and as a food source by many indigenous cultures throughout the South Pacific, and they continue to play a prominent role in Chilean cuisine.
Durvillaea antarctica, also known as cochayuyo and rimurapa, is a large, robust species of southern bull kelp found on the coasts of Chile, southern New Zealand, and Macquarie Island. D. antarctica, an alga, does not have air bladders, but floats due to a unique honeycomb structure within the alga's blades, which also helps the kelp avoid being damaged by the strong waves.
Turbinaria is a genus of brown algae (Phaeophyceae) found primarily in tropical marine waters. It generally grows on rocky substrates. In tropical Turbinaria species that are often preferentially consumed by herbivorous fishes and echinoids, there is a relatively low level of phenolics and tannins.
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Sphacelariales is an order of brown algae.
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Gavino Trono Jr. is a Filipino marine biologist dubbed as the "Father of Kappaphycus farming". He was conferred the rank of National Scientist of the Philippines for contributions to the study of tropical marine phycology, focusing on seaweed biodiversity. He is currently a professor emeritus of the University of the Philippines Marine Science Institute.
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