Belongs within: Rhodomelaceae.
Chondria is a genus of much-branched Rhodomelaceae with distinct pericentral cells throughout the thallus and flat spermatangial plates (Womersley 2003).
Chondria: turf of the surf
Published 27 April 2020
Of the major groups of multicellular algae (or ‘seaweeds’ in the common parlance) found in the world today, the red algae are unquestionably the most speciose. In this post, I’m looking at a widespread genus of red algae going by the name of Chondria.
Chondria is a genus of fifty or more known species of marine algae belong to the Rhodomelaceae, one of the most diverse families of red algae, found in tropical and temperate regions of the world. Species vary in size and are found in a range of habitats from intertidal to subtidal. They may live attached to rock or growing over other seaweeds. Turfs of Chondria may form a significant part of local habitats, but like many smaller red algae they tend not to receive a great deal of attention from humans (I did come across webpages referring to it as a weed in marine aquaria). In the majority of Chondria species, the thallus is erect; more rarely, it grows prostrately against its substrate or free-floating. The thallus is attached to the substrate by a discoid holdfast or by haptera growing from stolons. The greater part of the thallus is filamentous and more or less irregularly branched. The branches may be cylindrical and compressed; the younger branches are often constricted at their bases. The tips of the branches may end in a depression or in a tapering filament. Structure-wise, filaments are solid in cross-section without internal hollows. A central axial cell is surrounded by a ring of five pericentral cells, with the outside of the filament composed of smaller cortical cells.
Like other red algae, Chondria species have a complicated triphasic life cycle. The haploid gametophytes are dioecious: that is, there are separate male and female individuals. Males produce flat, disc-shaped or slightly lobed spermatangia that release male gametes. Female gamete-producing structures grow from the base of lateral filaments on the thallus; fertilised female gametes grow into a diploid, more or less ovoid cystocarp that remains attached to the parent gametophyte. Diploid spores released by the cystocarp grow into independent tetrasporophytes. These produce haploid spores by meiosis that will be released and grow into new gametophytes, and the cycle begins again.
Systematics of Chondria
Characters (from Womersley 2003): Thallus usually erect, rarely prostrate or free-floating, much branched irregularly radially or unilaterally, rarely subdistichously, with or without one to a few percurrent axes; a few species with tendrils, axillary branches often present; branches terete or compressed, young branches basally constricted. Some species with swollen, bulbous, sterile storage organs. Attachment by discoid holdfasts or haptera from stolons; epilithic or epiphytic. Structure. Apices of branches depressed or rounded, or tapering, with an apical filament usually 10–20 cells long, the subapical cells cutting off 5 pericentral cells in alternating order and branched trichoblasts. Pericentral cells of similar length to axial cells except near apices of tetrasporangial thalli, producing 2–5 series of di- to quadrichotomous branchings, expanding rapidly to form the rounded ends of branches; pericentral cells remaining clear throughout the thallus, cortex of compact, ovoid cells with the epidermal cells ovoid or angular to elongate in surface view. Pericentral and often the inner cortical cells of most species developing wall thickenings of various forms often characteristic of the species. Rhizoids usually formed from pericentral and inner cortical cells, sparse to dense around these cells in larger branches. Secondary cortex absent or present on the lower axes by proliferation of the epidermis. Reproduction: Gametophytes dioecious. Procarps borne on a lower cell of trichoblasts, with the fifth-formed pericentral (supporting) cell bearing a 4-celled carpogonial branch and lateral and basal sterile cell groups; auxiliary cell cut off post-fertilization or in some species the supporting cell acting as auxiliary cell. Carposporophytes with a basal fusion cell and branched gonimoblast with clavate terminal carposporangia, replaced from lower cells. Cystocarps ovoid to slightly urceolate, in some species with a basal spur developed from trichoblast cells above the supporting cell; pericarp ostiolate, with 9–18 erect filaments arising pre-fertilization from adjacent pericentral cells, each cell with 2–3 outer pericentral cells and ecorticate or not. Spermatangial plates flat, discoid or slightly lobed, developed from the whole or a basal branch of a trichoblast, with the primary cells producing a layer of initials each cell of which cuts off 2–4 spermatangia, and with a sterile margin 1–3 cells broad. Tetrasporangia developed in lesser branchlets, cut off singly from near the outer ends of 1–3 radially elongate pericentral cells per axial cell, covered by the outer cortex and epidermal cells.
<==Chondria Agardh 1817 (nom. cons.)W03 |--C. capillaris (Hudson) Wynne 1991W03 (see below for synonymy) |--C. acrorhizophoraLY96 |--C. angustata (Hooker & Harvey) Kylin ex Kylin & Skottsb. 1919 [=Laurencia pinnatifida var. angustata]L27 |--C. angustissima Gordon-Mills & Womersley 1987W03 |--C. arcuata Hollenberg 1945W03 |--C. armata (Kützing) Okamura 1907HS14 |--C. atropurpureaLY96 |--C. baileyanaLY96 |--C. bulbosa Harvey 1859 (see below for synonymy)W03 |--C. capensis (Harvey) Falkb. 1901 [=Chondriopsis capensis]L27 |--C. capreolis Gordon-Mills & Womersley 1987 [=Laurencia uncinata Kützing 1849 non Zanardini 1847]W03 |--C. chejuensis Lee in Lee & Yoon 1996LY96 |--C. concrescensLY96 |--C. crassicaulis Harvey 1859LY96 |--C. curdieana (Harvey) de Toni 1903 (see below for synonymy)W03 |--C. dasyphyllaLY96 [=Fucus dasyphyllus Woodward 1794LY96, Laurencia dasyphyllaG64] |--C. expansa Okamura 1927LY96 |--C. flagellaris Hooker & Harvey 1855 [=Chondriopsis flagellaris]L27 |--C. foliifera (Agardh) Falkenberg 1901 [=Chondriopsis foliifera Agardh 1885]W03 |--C. fusifolia (Hooker & Harvey) Harvey 1859 (see below for synonymy)W03 |--C. harveyana (Agardh) de Toni 1903 (see below for synonymy)W03 |--C. hieroglyphica Gordon-Mills & Womersley 1987W03 |--C. incrassata (Agardh) Gordon-Mills & Womersley 1987 (see below for synonymy)W03 |--C. incurva Gordon-Mills & Womersley 1987W03 |--C. infestans (Lucas) Millar 1990 (see below for synonymy)W03 |--C. intertexta Silva 1972 [=C. intricata Okamura 1912 non (Lamouroux) Agardh 1817]LY96 |--C. lanceolata Harvey 1855 [=Chondriopsis lanceolata (Harvey) Agardh 1892]W03 |--C. lancifolia Okamura 1934LY96 |--C. macrocarpa Hooker & Harvey 1855 [=Chondriopsis macrocarpa]L27 |--C. minutulaHK90 |--C. pellucida Lee in Lee & Yoon 1996LY96 |--C. simpliciuscula Weber-van Bosse 1914LY96 |--C. stoloniferaLY96 |--C. subfasciculata (Agardh) Gordon-Mills & Womersley 1987 [=Chondriopsis succulenta var. subfasciculata Agardh 1892]W03 |--C. subsecunda Gordon-Mills & Womersley 1987W03 `--C. succulenta (Agardh) Falkenberg 1901 (see below for synonymy)W03
Chondria bulbosa Harvey 1859 [=Chondriopsis bulbosa (Harvey) Agardh 1890, Rhododactylis bulbosa (Harvey) Agardh 1876; incl. Chondria suprabulbosa Gordon-Mills & Womersley 1987]W03
Chondria capillaris (Hudson) Wynne 1991W03 [incl. Fucus tenuissimusLY96, *C. tenuissima (Withering) Agardh 1817W03, Laurencia tenuissimaG64]
Chondria curdieana (Harvey) de Toni 1903 [=Chondriopsis curdieana Harvey ex Agardh 1892; incl. Chondria dasyphylla var. pyrifera Agardh 1863]W03
Chondria fusifolia (Hooker & Harvey) Harvey 1859 [=Laurencia fusifolia Hooker & Harvey 1847, Chondriopsis fusifolia (Hooker & Harvey) Agardh 1892]W03
Chondria harveyana (Agardh) de Toni 1903 [=Chondriopsis harveyana Agardh 1863; incl. Chondriopsis arborescens Agardh 1892, Chondria arborescens (Agardh) de Toni 1903, Bolboclinum rytidophloeum Agardh 1894 (n. n.)]W03
Chondria incrassata (Agardh) Gordon-Mills & Womersley 1987 [=Coeloclonium incrassatum Agardh 1876; incl. Dolichoscelis disticha Agardh 1899, Chondriopsis ovalifolia Agardh 1890, Chondria ovalifolia (Agardh) de Toni 1903]W03
Chondria infestans (Lucas) Millar 1990 [=Laurencia infestans Lucas 1919; incl. C. myriopoda Gordon-Mills & Millar in Gordon-Mills & Womersley 1987]W03
Chondria succulenta (Agardh) Falkenberg 1901 [=Chondriopsis succulenta Agardh 1892; incl. Chondria iridescens Lucas 1927, Chondria dasyphylla var. sedifolia Harvey 1863]W03
*Type species of generic name indicated
References
[G64] Gray, J. E. 1864. Handbook of British Water-weeds or Algae. R. Hardwicke: London.
[HK90] Huisman, J. M., G. A. Kendrick, D. I. Walker & A. Couté. 1990. The marine algae of Shark Bay, Western Australia. In: Berry, P. F., S. D. Bradshaw & B. R. Wilson (eds) Research in Shark Bay: Report of the France-Australe Bicentenary Expedition Committee pp. 89–100. Western Australian Museum.
[HS14] Huisman, J. M., & A. Sampey. 2014. Kimberley marine biota. Historical data: marine plants. Records of the Western Australian Museum Supplement 84: 45–67.
[L27] Laing, R. M. 1927. A reference list of New Zealand marine algae. Transactions and Proceedings of the New Zealand Institute 57: 126–185.
[LY96] Lee, Y.-P., & S.-Y. Yoon. 1996. Taxonomy of Chondria (Rhodophyta) in Korea. Algae 11 (1): 107–139.
[W03] Womersley, H. B. S. 2003. The Marine Benthic Flora of southern Australia. Rhodophyta pt IIID. Ceramiales—Delesseriaceae, Sarcomeniaceae, Rhodomelaceae. Flora of Australia Supplementary Series 18. Australian Biological Resources Study: Canberra, and the State Herbarium of South Australia: Adelaide.