Lithothrix J.E.Gray, 1867
Holotype species: Lithothrix aspergillum J.E.Gray
Original publication and holotype designation: Gray, J.E. (1867). Lithothrix, a new genus of Corallinae. Journal of Botany, British and Foreign 5: 33, 2 figs.
Description: Thalli comprising crustose holdfasts bearing one to several erect, branched, articulated fronds made up of calcified intergenicula separated by uncalcified genicula. Branching of main axes sparsely dichotomous; lateral branches often present. Cells in contiguous filaments often joined by secondary pit-connections; cell fusions lacking. Intergenicula consisting of filaments arranged in single tiers of short medullary cells (20-30 um long); periphery of intergenicular medulla proliferating cells downward so as to form a photosynthetic cortical flange of short cells overlying subtending geniculum. Near branch apices flanges increasing in length as they grow and as underlying genicular cells elongate. Genicula each consisting of a single tier of medullary cells up to 600 um long, the proximal parts of which are uncalcified. Trichocytes not reported. Reproductive cells forming within conceptacles on intergenicular surfaces (lateral conceptacles). Tetrasporangial initials forming in ring around central sterile cells and sometimes also in central group. Central cells (cavity cells) producing conceptacle roof and then atrophying below roof to form conceptacle chamber. Spores germinating into crustose sporelings by the Amphiroa-type of spore germination.
Information contributed by: H.W. Johansen. The most recent alteration to this page was made on 2010-10-13 by Wendy Guiry.
Taxonomic status: This name is of an entity that is currently accepted taxonomically.
Most recent taxonomic treatment adopted: Schneider, C.W. & Wynne, M.J. (2007). A synoptic review of the classification of red algal genera a half a century after Kylin's "Die Gattungen der Rhodophyceen". Botanica Marina 50: 197-249.
Comments: Lithothrix is a monotypic genus on the Pacific coast of Baja California to British Columbia. There appear to be large gaps in this distribution, for example in Bodega Head in northern California. Together with Corallina forms low intertidal turfs in S. California. This genus has unusual characteristics that set it clearly aside from Amphiroa. Both genicula and intergenicula are single-tiered. Intergenicular tissue grows downward from each intergeniculum to form an extensive flange over a long-celled subtending geniculum. Conceptacles develop on the sides of the intergenicula and, as far as known, the reproductive cells are similar to those in Amphiroa. Lithothrix is known mostly in the bisporangial condition, with the only known tetrasporangial and gametangial plants in southern California. Lithothrix, appearing to share ancesters with Amphiroa, has become isolated in the northeastern Pacific and is able to tolerate colder water than species in the latter genus.
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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: https://www.algaebase.org/search/genus/detail/?genus_id=42218
Citing AlgaeBase
Cite this record as:
Wendy Guiry in Guiry, M.D. & Guiry, G.M. 13 October 2010. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 16 April 2024
