Halosphaera F.Schmitz, 1878
Holotype species: Halosphaera viridis F.Schmitz
Original publication and holotype designation: Schmitz, F. (1878). Halosphaera, eine neue Gattung grüner Algen aus dem Mittelmeer. Mittheilungen aus der Zoologischen Station zu Neapel 1: 273-286, pl. III.
Description: Unicellular algae which occur in two stages, a coccoid so-called Phycoma stage and a motile quadriflagellate stage. The Phycoma stage up to 800 µm in diameter, surrounded by smooth or punctate double wall, the inner of pectic nature, the outer of material related to sporopollenin. The Phycoma stage contains numerous chloroplasts, in most species with pyrenoids. At maturity the contents divide into smaller round or oval discs, forming so-called "rosettes". Initially uninucleate, the nucleus of the mature Phycoma stage divides into numerous swarmers. These are released surrounded by the inner wall, while the outer wall is cast off. The inner wall eventually bursts, releasing the swarmers. These possess 4 anterior flagella, 1-2 times cell length, arising from an anterior pit surrounded by 4 lobes. The single parietal chloroplast contains 2-4 pyrenoids situated below the junction of the 4 anterior cell lobes. A rhizoplast emanates from the flagellar bases, passes through the cell and terminates on the eyespot. A large pouch of unknown function connects to the flagellar pit. A vacuole located near the pouch often contains plant cells, indicating phagotrophy. Ejectile organelles (mucocysts) are distributed in the peripheral cytoplasm. All surfaces covered with organic scales of several types. The cell body in the only species examined in detail covered with 4 types of scales, one type restricted to the flagellar pit (Pennick 1977). The flagella covered with 3 types of scales, one type hair-shaped, another limuloid resembling the limulus scales of Pyramimonas. The motile stage divides by fission. The changeover from motile to Phycoma stage is apparently related to the lunar cycle. Sexual reproduction unknown.
Information contributed by: Ø. Moestrup & M.D. Guiry. The most recent alteration to this page was made on 2014-09-22 by M.D. Guiry.
Taxonomic status: This name is of an entity that is currently accepted taxonomically.
Most recent taxonomic treatment adopted: Throndsen, J. (1996). The planktonic marine flagellates. In: Identifying marine phytoplankton. (Tomas, C.R. Eds), pp. 591-730. San Diego: Academic Press.
Comments: The species differ in size and ornamentation of the Phycoma and in the number and appearance of the "rosettes". Differences in the scale structure of the swarmers have also been recorded. The Phycoma stage is widely distributed in the plankton of both hemispheres. It is easily visible in plankton hauls, containing large amounts of lipid and in calm weather accumulating at the surface. The ultrastructure of Halosphaera was examined by Hori and others (1985), scale structure by Pennick (1977).
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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=44991
Cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 22 September 2014. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 29 September 2023