Acetabularia acetabulum | |
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Top view of caps of Acetabularia acetabulum | |
Scientific classification | |
(unranked): | Viridiplantae |
Division: | Chlorophyta |
Class: | Ulvophyceae |
Order: | Dasycladales |
Family: | Polyphysaceae |
Genus: | Acetabularia |
Species: | A. acetabulum |
Binomial name | |
Acetabularia acetabulum (Linnaeus) P. C. Silva, 1952 | |
Synonyms [1] | |
Acetabularia integra J. V. Lamouroux Contents |
Acetabularia acetabulum is a species of green alga in the family Polyphysaceae. It is found in the Mediterranean Sea at a depth of one to two metres. [2]
This alga adheres to the substrate with rhizoids (root-like processes), and these are the only part of the alga present in the winter. The thallus consists of a single cell, and in the spring a slender stem develops from the holdfast, growing vertically to a length of about 5 cm (2 in). Growth is interrupted at intervals while a whorl of hairs develop which encircle the stem, branching dichotomously. As the stem lengthens and more whorls grow, the lower hairs drop off leaving behind a circular scar. When the stem is fully developed, a disc-shaped cap up to 1.2 cm (0.5 in) wide grows at the tip, the whole frond resembling a pale green parasol; further whorls of hairs grow from the upper surface of the cap. [3] [4]
Before cap expansion, the organism consists of a single cell with a single nucleus, located at the base of the stem. [3] As the cap expands, the nucleus divides once by meiosis after which it divides multiple times by mitosis, producing thousands of haploid "secondary" nuclei. These migrate up the stem into the cap, each becoming enclosed in a gametangium containing the nucleus and a small amount of cytoplasm. Inside the gametangium, the nucleus undergoes further repeated mitotic division, so that by the end of summer, when the cap disintegrates, thousands of "tertiary" nuclei are released into the sea as gametes from each gametangial ray. Fertilisation occurs in the open water, and the zygotes settle on the seabed. [3]
This alga is unicellular, each frond being formed from a single large cell containing several million chloroplasts. [5] These are in constant motion: in the daytime, they move to expose to themselves to the maximum degree possible to the light and the stems appear uniformly dark green, while at night they aggregate into clusters and the stem becomes pale green. This effect can be demonstrated by shining a ray of blue light on a stem in the dark and extinguishing it some time later, forming a transient green band. [5]
This alga has been used as a model organism in developmental biology, being useful for this purpose because of the enormous size of its single cell with its single nucleus, and its complex cell structure and development. [3]
The main storage polysaccharide of Acetabularia acetabulum is starch as granules within the chloroplast's stroma. [2]
Predators of Acetabularia acetabulum include the sea slug Elysia timida . [2]
A chloroplast is a type of membrane-bound organelle known as a plastid that conducts photosynthesis mostly in plant and algal cells. The photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, and stores it in the energy-storage molecules ATP and NADPH while freeing oxygen from water in the cells. The ATP and NADPH is then used to make organic molecules from carbon dioxide in a process known as the Calvin cycle. Chloroplasts carry out a number of other functions, including fatty acid synthesis, amino acid synthesis, and the immune response in plants. The number of chloroplasts per cell varies from one, in unicellular algae, up to 100 in plants like Arabidopsis and wheat.
The plastid is a membrane-bound organelle found in the cells of plants, algae, and some other eukaryotic organisms. They are considered to be intracellular endosymbiotic cyanobacteria. Examples include chloroplasts, chromoplasts, and leucoplasts.
The chlorarachniophytes are a small group of exclusively marine algae widely distributed in tropical and temperate waters. They are typically mixotrophic, ingesting bacteria and smaller protists as well as conducting photosynthesis. Normally they have the form of small amoebae, with branching cytoplasmic extensions that capture prey and connect the cells together, forming a net. They may also form flagellate zoospores, which characteristically have a single subapical flagellum that spirals backwards around the cell body, and walled coccoid cells.
Sacoglossa, commonly known as the sacoglossans or the "solar-powered sea slugs", are a superorder of small sea slugs and sea snails, marine gastropod mollusks that belong to the clade Heterobranchia. Sacoglossans live by ingesting the cellular contents of algae, hence they are sometimes called "sap-sucking sea slugs".
Acetabularia crenulata, one of the many species known as mermaid's wineglass, is a form of green alga generally found in shallow tropical seas. It can be found growing in great abundance along stretches of the overseas highway to Key West, Florida bordering on Florida Bay. It has been used in some important research on nuclear and cytoplasmic relationships. During its life cycle it has one large nucleus.
Acetabularia is a genus of green algae in the family Polyphysaceae. Typically found in subtropical waters, Acetabularia is a single-celled organism, but gigantic in size and complex in form, making it an excellent model organism for studying cell biology. In form, the mature Acetabularia resembles the round leaves of a nasturtium, is 4 to 10 centimetres tall and has three anatomical parts: a bottom rhizoid that resembles a set of short roots; a long stalk in the middle; and a top umbrella of branches that may fuse into a cap. Unlike other giant unicellular organisms, which are multinucleate, members of this genus a single nucleus located in the rhizoid and allows the cell to regenerate completely if its cap is removed. The caps of two Acetabularia may also be exchanged, even from two different species. In addition, if a piece of the stem is removed, with no access to the nucleus in the rhizoid, this isolated stem piece will also grow a new cap.
Kleptoplasty or kleptoplastidy is a process in symbiotic relationships whereby plastids, notably chloroplasts from algae, are sequestered by the host. The word is derived from Kleptes (κλέπτης) which is Greek for thief. The alga is eaten normally and partially digested, leaving the plastid intact. The plastids are maintained within the host, temporarily continuing photosynthesis and benefiting the host.
Elysia chlorotica is a small-to-medium-sized species of green sea slug, a marine opisthobranch gastropod mollusc. This sea slug superficially resembles a nudibranch, yet it does not belong to that clade. Instead it is a member of the clade Sacoglossa, the sap-sucking sea slugs. Some members of this group use chloroplasts from the algae they eat for photosynthesis, a phenomenon known as kleptoplasty. Elysia chlorotica is one species of such "solar-powered sea slugs". It lives in a subcellular endosymbiotic relationship with chloroplasts of the marine heterokont alga Vaucheria litorea.
Bryopsidales is an order of green algae, in the class Ulvophyceae.
Bryopsis is a genus of marine green algae in the family Bryopsidaceae. It is frequently a pest in aquariums, where it is commonly referred to as hair algae.
Chlorotetraedron is a genus of green algae, in the family Neochloridaceae. The name may also be written as Chlorotetraëdon. It is found as freshwater plankton or in soil.
Elysia timida is a species of sacoglossan sea slug, a marine opisthobranch gastropod mollusk. Found in the Mediterranean and nearby parts of the Atlantic, it is herbivorous, feeding on various algae in shallow water.
Guillardia is a genus of marine biflagellate cryptomonad algae with a plastid obtained through secondary endosymbiosis of a red alga.
Vaucheria litorea is a species of yellow-green algae (Xanthophyceae). It grows in a filamentous fashion. V. litorea is a common intertidal species of coastal brackish waters and salt marshes of the Northern Atlantic, along the coasts of Europe and North America. It is also found in the Eastern Pacific coasts of Washington state. It is found to be able to tolerate a large range of salinities, making it euryhaline.
Halimeda tuna is a species of calcareous green seaweed in the order Bryopsidales. It is found on reefs in the Atlantic Ocean, the Indo-Pacific region and the Mediterranean Sea. Halimeda tuna is the type species of the genus Halimeda and the type locality is the Mediterranean Sea. The specific name "tuna" comes from the Taíno language, meaning "cactus" and referring to the resemblance of the thallus to the growth form of an Opuntia cactus.
Caulerpa prolifera is a species of green alga, a seaweed in the family Caulerpaceae. It is the type species of the genus Caulerpa, the type location being Alexandria, Egypt. It grows rapidly and forms a dense mass of vegetation on shallow sandy areas of the sea.
Acetabularia caliculus, the umbrella alga, is a species of green alga found in shallow temperate and tropical seas. It usually grows on pebbles, shells or pieces of rock, and is often found in seagrass meadows, on mudflats and coral reefs, in estuaries and growing on the submerged roots of mangroves. Each individual thallus consists of a single cell with a long stipe and a terminal cup-shaped or flattened disc.
Scytothamnus australis is a brown alga species in the genus Scytothamnus found in New Zealand. It is a sulphated polysaccharide and the type species in the genus.
Padina boergesenii, commonly known as the leafy rolled-blade alga, is a species of small brown alga found in the tropical and subtropical western Atlantic Ocean, the Mediterranean Sea, and the Pacific Ocean. This seaweed was named in honour of the Danish botanist and phycologist Frederik Børgesen.
Acinetospora crinita is a species of brown alga in the family Acinetosporaceae. It is found in the temperate northeastern Atlantic Ocean and the Mediterranean Sea.