Mastocarpus Kützing, 1843: 14-16

Classification:
Empire Eukaryota
Kingdom Plantae
Phylum Rhodophyta
Subphylum Eurhodophytina
Class Florideophyceae
Subclass Rhodymeniophycidae
Order Gigartinales
Family Phyllophoraceae

Lectotype species: Mastocarpus mamillosus (Goodenough & Woodward) Kützing

Currently accepted name for the type species: Mastocarpus stellatus (Stackhouse) Guiry

Original publication:Kützing, F.T. (1843). Phycologia generalis oder Anatomie, Physiologie und Systemkunde der Tange... Mit 80 farbig gedruckten Tafeln, gezeichnet und gravirt vom Verfasser. pp. [part 1]: [i]-xxxii, [1]-142, [part 2:] 143-458, 1, err.], pls 1-80. Leipzig: F.A. Brockhaus.
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Type designated inSetchell, W.A. & Gardner, N.L. (1933). A preliminary survey of Gigartina, with special reference to its Pacific North American species. University of California Publications in Botany 17: 255-339, Plates 46-65.

Taxonomic status: currently recognized as a distinct genus.

Description: Gametophytes reach 20 cm in length and are erect from basal discs. Thalli are broadly to narrowly and fairly regularly dichotomous, with or without marginal and surface proliferations, and with the main axes usually conspicuously channeled. Cystocarps lack an enveloping filamentous hull round the carposporophyte. Tetrasporangia occur singly and intercalarily within erect filaments.

Kim (1976) distinguished gametophytes of Mastocarpus from those of Gigartina by the absence of a filamentous hull around the carposporophyte (comparable to the situation in Chondrus), the presence of sterile laterals on the basal cell of the carpogonial branch, and the smaller number of gonimoblast initials, which are not exclusively directed inwardly. Guiry et al. (1984) emphasize the channelled thalli, carpogonial/cystocarpic papillae, and the unchained tetrasporangia in heteromorphic tetrasporophytes as distinghishing features of the family and genus.

Comments: The type species occurs in the north Atlantic Ocean from Russia to Portugal and from Morocco to Mauritania in the east and from Rhode Island to Newfoundland in the west. Two other species are common in the eastern Pacific from Alaska to Baja, and a fourth is known from the northern Pacific from Hokkaido to s.e. Alaska. Both the gametophyte and tetrasporophytic stages are characteristic of high to mid intertidal rocks on open coasts, although the type species also occurs subtidally (Dixon and Irvine, 1977). Until Kim's (1976) study of the Gigartinaceae, Mastocarpus had been treated as a subgenus of Gigartina. Kim informally proposed the family Mastocarpaceae for the assemblage, although Denizot (1968) had earlier established the Petrocelidaceae for "species" the tetrasporophytic stage. Fletcher and Irvine (1982) described gametophytes and an isomorphic alternation of generations in Petrocelis hennedyi, a species of very similar vegetative anatomy to P. cruenta but with catenate intercalary tetrasporangia. This taxon was later transferred to the genus Haemescharia of the Haemeschariaceae by Wilce and Maggs (1989).

A monotypic family of 4-6 species of cool- to cold temperate Northern Hemisphere distribution. Gametophytic plants are erect from discoid bases and are composed of a filamentous medulla of extensively secondarily pit-connected cells surrounded by a broad cortex of seudodi-/trichotomous filaments oriented perpendicularly to the medulla. Female gametophytes are procarpic, the carpogonial branches being 3 celled and generally bearing one or two sterile lateral cells on the basal cell. The supporting cell becomes the generative auxiliary cell following fertilization, and multiple gonimoblast initials grow as filaments directed both inwardly and outwardly, with most development taking place thallus inwardly. Carpogonial branches and cystocarps are formed in papillar outgrowths, the cystocarps consisting of pockets of catenate carposporangia isolated among sterile placental filaments of mixed and partially fused carposporophyte and gametophyte cells. Tetrasporophytes are heteromorphic to gametophytes, being non-calcified crusts anchored without rhizoids to rock and consisting of a several-layered hypothallus that gives rise to perpendicular, erect, simple to sparingly branched dorsal perithallial filaments occasionally linked by secondary pit connections. Tetrasporangia are cruciate and intercalary in a deeply buried layer of the perithallus.

Several studies, beginning with that of West (1972) and continuing with West et al. (1977, 1978, 1983), Dion (1979), Masuda and Kurogi (1981), Guiry and West (1983), and Masuda et al. 1984, 1987), have shown that certain common species of what were previously considered Gigartina from Europe, North America and Japan in which tetrasporophytes were formerly unknown alternate with a crustose tetrasporophytic phase identical to described species of the genus Petrocelis. In some isolates, a direct type of life history has been demonstrated, the basal discs from which erect thalli arise directly yielding lambda carrageenan indicative of diploidy, and the erect fronds producing kappa carrageenan, which normally typifies gamemtophytes in this family and the Gigartinaceae (West et al. 1983).

NCBI Nucleotide Sequences

Numbers of names and species: There are 26 species (and infraspecific) names in the database at present, of which 14 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):

References
Kützing, F.T. (1843). Phycologia generalis oder Anatomie, Physiologie und Systemkunde der Tange... Mit 80 farbig gedruckten Tafeln, gezeichnet und gravirt vom Verfasser. pp. [part 1]: [i]-xxxii, [1]-142, [part 2:] 143-458, 1, err.], pls 1-80. Leipzig: F.A. Brockhaus.

Setchell, W.A. & Gardner, N.L. (1933). A preliminary survey of Gigartina, with special reference to its Pacific North American species. University of California Publications in Botany 17: 255-339, Plates 46-65.

Guiry, M.D., West, J.A., Kim, D.-H. & Masuda, M. (1984). Reinstatement of the genus Mastocarpus Kützing (Rhodophyta). Taxon 33: 53-63.

Contributors
Some 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 (PSA) and intended to be published in CD format. These AlgaeBase descriptions are now being continually updated, and each current contributor is identified above. The PSA and AlgaeBase warmly acknowledge the generosity of all past and present contributors and particularly the work of Dr Parker.

Descriptions of chrysophyte genera were subsequently published in J. Kristiansen & H.R. Preisig (eds.). 2001. Encyclopedia of Chrysophyte Genera. Bibliotheca Phycologica 110: 1-260.

Linking to this page: http://www.algaebase.org/search/genus/detail/?genus_id=20

Citing AlgaeBase
Cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 2013. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched on 24 May 2013.

Algaebase taxon LSID: urn:lsid:algaebase.org:taxname:8425