''Acetabularia'' is a genus of

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 ...

in the family

Polyphysaceae The Polyphysaceae is a taxonomic family (biology), family of green algae, one of three families in the order Dasycladales. For single-celled organisms, they are huge, growing to nearly a foot long in some cases. References

Dasycladales ...

. 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 Cell biology (also cellular biology or cytology) is a branch of biology that studies the structure, function, and behavior of cells. All living organisms are made of cells. A cell is the basic unit of life that is responsible for the living an ...

. In form, the mature ''Acetabularia'' resembles the round leaves of a nasturtium, is tall and has three anatomical parts: a bottom

rhizoid Rhizoids are protuberances that extend from the lower epidermal cells of bryophytes and algae. They are similar in structure and function to the root hairs of vascular land plants. Similar structures are formed by some fungi. Rhizoids may be un ...

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 Multinucleate cells (also known as multinucleated cells or polynuclear cells) are eukaryotic cells that have more than one nucleus, i.e., multiple nuclei share one common cytoplasm. Mitosis in multinucleate cells can occur either in a coordinate ...

, members of this genus possess a single nucleus located in the rhizoid, which 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. Acetabularia meditarranea

In the 1930s–1950s

Joachim Hämmerling Dr. Joachim Hämmerling (9 March 1901 - 5 August 1980) was a pioneering Danish-German biologist funded by Nazi Germany who determined that the nucleus of a cell controls the development of organisms. His experimentation with the green algae ''A ...

conducted experiments in which he demonstrated ''Acetabularia''s genetic information is contained in the nucleus. This was the first demonstration that

gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...

s are encoded by

DNA Deoxyribonucleic acid (; DNA) is a polymer composed of two polynucleotide chains that coil around each other to form a double helix. The polymer carries genetic instructions for the development, functioning, growth and reproduction of al ...

eukaryote The eukaryotes ( ) constitute the Domain (biology), domain of Eukaryota or Eukarya, organisms whose Cell (biology), cells have a membrane-bound cell nucleus, nucleus. All animals, plants, Fungus, fungi, seaweeds, and many unicellular organisms ...

s; earlier studies by

Oswald Avery Oswald Theodore Avery Jr. (October 21, 1877 – February 20, 1955) was a Canadian-American physician and medical researcher. The major part of his career was spent at the Rockefeller Hospital in New York City. Avery was one of the first molecu ...

and others had shown that this was true for

prokaryote A prokaryote (; less commonly spelled procaryote) is a unicellular organism, single-celled organism whose cell (biology), cell lacks a cell nucleus, nucleus and other membrane-bound organelles. The word ''prokaryote'' comes from the Ancient Gree ...

Etymology

The name, ''Acetabularia'', derives from the

Latin Latin ( or ) is a classical language belonging to the Italic languages, Italic branch of the Indo-European languages. Latin was originally spoken by the Latins (Italic tribe), Latins in Latium (now known as Lazio), the lower Tiber area aroun ...

word ''

acetabulum The acetabulum (; : acetabula), also called the cotyloid cavity, is a wikt:concave, concave surface of the pelvis. The femur head, head of the femur meets with the pelvis at the acetabulum, forming the Hip#Articulation, hip joint. Structure The ...

'', a broad, shallow cup used for dipping bread; the upturned cap of ''Acetabularia'' resembles such a cup. For this reason, it is also sometimes called mermaid's wineglass. In the 19th century, the same designation ''Acetabularia'' was proposed by

George Edward Massee George Edward Massee (20 December 1845 – 16 February 1917) was an English mycologist, plant pathologist, and botanist. Background and education George Massee was born in Scampston, East Riding of Yorkshire, the son of a farmer. He was educ ...

for a genus of fungi (now '' Cyphellopus''), but this usage is obsolete and considered invalid as the algal name takes precedence.

Anatomy and life cycle

''Acetabularia'', as well as being unicellular, is also a

uninucleate {{Short pages monitor