Jania J.V.Lamouroux, 1812

Lectotype species: Jania rubens (Linnaeus) J.V.Lamouroux

Original publication: 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.

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Type designated in: Manza, A.V. (1937). The genera of the articulated corallines. Proceedings of the National Academy of Science of the United States of America 23: 44-48.

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Description: Thalli mostly 1–100 mm tall, epilithic, epiphytic or occasionally epizoic, consisting of a calcified crustose holdfast (sometimes obscured or replaced by stolons with or without secondary holdfasts) and erect to procumbent axes composed of alternating calcified intergenicula and uncalcified genicula. Intergenicula terete to compressed to flattened, sometimes with two more-or-less prominent distal, upward- or laterally projecting lobes, wings or spine-like extensions. Main axes (branches arising from holdfasts or stolons) and lateral axes (branches arising from main axis or other lateral branches) mostly or entirely complanate (more-or-less flattened into one plane) to partly or entirely multiplanar (developing in various planes); general branching of axes from distal ends of intergenicula, dichotomous throughout, largely pinnate, or varying from dichotomous to pinnate to alternate to irregular, with trichotomies and polychotomies sometimes present; adventitious branching absent to common, peripheral, arising from surfaces of intergenicula or outer walls of conceptacles, sometimes bearing further conceptacles. Vegetative apical intergenicula columnar, of similar width from base to top, or tapering somewhat towards the tip; or becoming swollen, commonly wedge-shaped (cuneiform) pear-shaped (pyriform) or globular; or compressed and narrower at base becoming flattened and wider at top, before new general branch formation. Thallus construction in axes and stolons (creeping horizontal runners that form new plants or branches along its length) monomerous, consisting of a single system of branched, laterally coherent filaments organised into alternating intergenicula and genicula. Intergenicula (as seen in a precise median longitudinal section) composed of a central core (medullary) region in which thin-walled, calcified, elongate cells of adjacent filaments appear more-or-less aligned to form tiers of cells (tiers not obvious if not seen in median longitudinal section), and a peripheral (cortical) regionwhere distal portions of calcified core filaments or their derivatives bend or project outward and terminate at the thallus surface in epithallial cells with rounded or flattened outer walls. Actively growing filaments in apical intergenicula terminating in elongate meristematic cells. Successive cells of the same filament linked by primary pitconnections. Some cells of adjacent intergenicular filaments linked by cell fusions; secondary pit-connections unknown. Genicula arising secondarily behind branch apices, composed (as seen in median longitudinal section) of one tier of decalcified, transformed, usually thick-walled core-region cells. Trichocytes reported for several species.

Life history, where known, triphasic with monoecious or dioecious haploid gametangial thalli, diploid carposporophytes and diploid tetrasporangial thalli. Bisporangial thalli and trisporangial thalli of unknown ploidy level also found in some species. Gametangial thalli, tetrasporangial thalli and bisporangial thalli all isomorphic; carposporophytes developing within old female conceptacles after presumed karyogamy, much smaller in size than and remaining attached to gametangial thallus. Gametangia and sporangia, where known, produced in uniporate conceptacles; conceptacles axial (formed at distal ends of intergenicula either terminally or at general branch dichotomies) or in some species embedded in lateral, upwardprojecting lobes (upward-pointing wing-like projections) of intergenicula; conceptacles walls often bearing adventitious branches producing further conceptacles and branches or sometimes bearing adventitious antenna-like (surmounting) branchlets not usually producing further conceptacles or branches.

Spermatangia, where known, formed on the walls of narrow, vertically elongate, male conceptacle chambers possessing short (30–120 µm long) pore canals; carpogonial branches, where known, arising on the floor of female-carposporangial chambers; carposporophytes, where known, developing within female conceptacle chambers after presumed karyogamy; mature carposporophytes usually composed of a comparatively small, compact central fusion cell up to 35 µm thick and 40–130 µm broad, and marginal carposporangial filaments bearing terminal carposporangia; tetrasporangial or bisporangial conceptacles solitary, or occasionally in a series of concatenate conceptacles, containing fewer than 15 mature sporangia per conceptacle chamber.

Information contributed by: Harvey, Woelkering & Reviers (2020, as emended by Kim et al. 2007). The most recent alteration to this page was made on 2021-02-11 by M.D. Guiry.

Taxonomic status: This name is of an entity that is currently accepted taxonomically.

Gender: This genus name is currently treated as feminine.

Most recent taxonomic treatment adopted: Harvey, A.S., Woelkerling, W.J. & Reviers, B. de (2020). A taxonomic analysis of Jania (Corallinaceae, Rhodophyta) in south-eastern Australia. Australian Systematic Botany 33: 221-277, 34 figs, 5 tables.

Comments: Common as epiphytic or epilithic tufts, or forming turfs in tropical, subtropical, and warm temperate areas. Fronds of most species probably growing rapidly and with lifespans of less than one year. Compared to Corallina, tetraspores (of J. rubens) secrete more mucilage, become attached more quickly, and produce sporelings with articulated fronds sooner (in 8 days) from limited holdfasts. Culture experiments have shown that lowering the phosphate concentration in media enhances growth (phosphate is a crystal inhibitor of calcite). Chromosome studies yield n = 24 (J. rubens). Jania is in the tribe Janieae together with Haliptilon and Cheilosporum. The tribe is clearly delimited from the Corallineae on the basis of reproductive cells and conceptacle structure

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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.

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Citing AlgaeBase
Cite this record as:
M.D. Guiry in Guiry, M.D. & Guiry, G.M. 11 February 2021. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. https://www.algaebase.org; searched on 16 July 2024

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