Acetabularia J.V. Lamouroux, 1812: 185

Classification:
Empire Eukaryota
Kingdom Plantae
Subkingdom Viridaeplantae
Phylum Chlorophyta
Class Ulvophyceae
Order Dasycladales
Family Polyphysaceae

• Taxonomy
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Holotype species: Acetabularia acetabulum (Linnaeus) P.C. Silva

Original publication and holotype designation: Lamouroux, J.V.F. (1812). Extrait d'un mémoire sur la classification des Polypiers coralligènes non entièrement pierreux. Nouveaux Bulletin des Sciences, par la Société Philomathique de Paris 3: 181-188.

Taxonomic status: currently recognized as a distinct genus.

Description: Thallus unbranched unicell 1-6 cm long, composed of a compact rhizoid, a tubular stalk ca. 1 mm diam., whorls of thrice-branched sterile laterals and a more or less flattened apical cap 0.5-1.5 cm dia. Whorls periodical from the apex of the stalk and deciduous leaving scars. The mature cap composed of 30-75 free or joined, terminally tapered or rounded elongate rays, which are associated basally with whorls of enlargements, the basipetal inferior corona and the apical superior corona from which project sterile laterals. Thallus lightly to heavily calcified. Thallus size, cap diameter and cap morphology are important species characteristics. Numerous parietal, discoid, grass green plastids without pyrenoids circulate in the peripheral cytoplasm which surrounds a large central vacuole. Chloroplast ultrastructure variable, without or with stacked grana; variable species specific. Starch grains in chloroplast and cytoplasm, the latter not membrane bound. Vegetative cells with a single diploid primary nucleus 75-200 mm dia. located in a branch of the rhizoid. Nucleate and anucleate fragments regenerate normal thalli. Primary nuclear division meiotic followed by a series of mitotic divisions forming secondary nuclei which migrate up the stalk establishing themselves in the rays. Uninucleate aggregations of cytoplasm become thick-walled cysts the nuclei of which further divide and form biflagellate isogametes. Number of cysts per ray variable into the 100's. Gametes 20-50 per cyst . Gametes from heterogenetic cysts fuse after liberation through an ostiole formed by a structured operculum, the cysts liberated from the rays. From zygote germination to gamete liberation takes ca 1 yr. Asexual reproduction by fragmentation, regeneration or development from basal rhizoids. Parthenogenesis of gametes reported in culture but thalli did not form normal apices. Acetabularia pantropical and subtropical. A. calyculus found at 37.5%N and A. mobii at 34%N in Japan. Common in brackish to hypersaline shallow waters. Thalli firmly attached to solid substrates such as stones, coral rubble, shells as well as to wood and industrial detritus such as rubber. Variable seasonal life history especially at the cool extremes of the range. Known from fossil record to Tertiary. The development, nucleo-cytoplasmic interactions, biochemistry, photobiology, genetics and molecular biology of Acetabularia species have been extensively studied. Changes in microtubules and microfilaments associated with key phenomena during growth and differentiation. The taxonomy remains uncertain with some authors accepting the generic segregates Chalmasia and Polyphysa, and others segregating Acetabularia in family Polyphysaceae with Halicoryne or place these genera in a subfamily of Dasycladaceae.

NCBI Nucleotide Sequences
As of 2 June 2009, nucleotide sequence data are available at http://www.ncbi.nlm.nih.gov/Genbank for 4,541 samples identified as Acetabularia. Taxonomic identifications of these samples to genus (or species) levels unaccompanied by explicit indication of voucher specimens may not be verifiable on morphological/anatomical grounds and consequently be of little or no taxonomic value, as noted by Harvey et al. 2009.

Numbers of names and species: There are 38 species names in the database at present, of which 12 have been flagged as currently accepted taxonomically.

Names: ('C' indicates a name that is currently accepted taxonomically; 'S' a homotypic or heterotypic synonym; 'U' indicates a name of uncertain taxonomic status, but which has been subjected to some verification nomenclaturally; 'P' indicates a preliminary AlgaeBase entry that has not been subjected to any kind of verification. For more information on a species click on it to activate a link to the Species database):

Acetabularia myriospora A.B. Joly & Cordeiro-Marina C 
Acetabularia parvula var. americana W.R. Taylor S 
Acetabularia parvula Solms-Laubach S 
Acetabularia peniculus var. cliftonii (Harvey) Solms-Laubach S 
Acetabularia peniculus (R. Brown ex Turner) Solms-Laubach C 
Acetabularia philippinensis Gilbert S 
Acetabularia polyphysoides f. deltoidea S 
Acetabularia polyphysoides P.L. Crouan & H.M. Crouan S 
Acetabularia pusilla (M.A. Howe) F.S. Collins S 
Acetabularia roxasii Tron et al. S 
Acetabularia ryukyuensis Okamura & Yamada C 
Acetabularia ryukyuensis var. philippinensis (Gilbert) Valet P 
Acetabularia schenckii K. Möbius C 
Acetabularia suhrii Solms-Laubach S 
Acetabularia toxasii Troño, Santiago & Ganzon-Fortes C 
Acetabularia tsengiana Egerod S 
Acetabularia velasquezii Troño, Santiago & Ganzon-Fortes S 
Acetabularia wettsteinii Schussnig S 

Information contributed by: L.B. Liddle. The most recent alteration to this page was made on 22 Feb 2005 by Robert Wilkes.

Contributors
Many of the descriptions included in AlgaeBase were originally from the unpublished Encyclopedia of Algal Genera, organised in the 1990s by Dr Bruce Parker on behalf of the Phycological Society of America and intended to be published in CD format. The descriptions are being continually updated, however, and each current contributor is identified above. The PSA and AlgaeBase warmly acknowledge the generosity of all past and present contributors and of Dr Parker.