''Acetabularia'' is a genus of

green algae The green algae (singular: green alga) are a group consisting of the Prasinodermophyta and its unnamed sister which contains the Chlorophyta and Charophyta/ Streptophyta. The land plants (Embryophytes) have emerged deep in the Charophyte alga ...

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 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 4 to 10 cm 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 Multinucleate cells (also known as multinucleated or polynuclear cells) are eukaryotic cells that have more than one nucleus per cell, i.e., multiple nuclei share one common cytoplasm. Mitosis in multinucleate cells can occur either in a coordina ...

, ''Acetabularia'' has 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. 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 ''Acetabularias genetic information is contained in the nucleus. This was the first demonstration that

gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...

s are encoded by DNA in

eukaryote Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bacter ...

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 molecula ...

and others had shown that this was true for

prokaryote A prokaryote () is a single-celled organism that lacks a nucleus and other membrane-bound organelles. The word ''prokaryote'' comes from the Greek πρό (, 'before') and κάρυον (, 'nut' or 'kernel').Campbell, N. "Biology:Concepts & Con ...

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 a dialect spoken in the lower Tiber area (then known as Latium) around present-day Rome, but through ...

word ''

acetabulum The acetabulum (), also called the cotyloid cavity, is a concave surface of the pelvis. The head of the femur meets with the pelvis at the acetabulum, forming the hip joint. Structure There are three bones of the ''os coxae'' (hip bone) that c ...

'', 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 educate ...

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