153,840 species and infraspecific names are in the database, 21,012 images, 59,576 bibliographic items, 413,468 distributional records.

Mesophyllum Me.Lemoine, 1928

Classification:
Empire Eukaryota
Kingdom Plantae
Subkingdom Biliphyta
Phylum Rhodophyta
Subphylum Eurhodophytina
Class Florideophyceae
Subclass Corallinophycidae
Order Hapalidiales
Family Mesophyllaceae

Lectotype species: Mesophyllum lichenoides (J.Ellis) Me.Lemoine

Original publication:Lemoine, M. (1928). Un nouveau genre de Mélobésiées: Mesophyllum. Bulletin de la Société Botanique de France 75: 251-254.

Type designated in Hamel, G. & Lemoine, Mme P. [=M.] (1953). Corallinacées de France et d'Afrique du Nord. Archives du Museum National d'Histoire Naturelle (Paris), série 7 1: 15-136.

Precise date of publication

between 23 March and 27 April 1928 (see Woelkerling & Lamy 1998: 721 for details) The requirements for valid publication are specified in the ICBN (International Code of Botanical Nomenclature).

Taxonomic status: currently recognized as a distinct genus.

Most recent taxonomic treatment adopted: Hind, K.R., Gabrielsen, P.W., Jensen, C.P. & Martone, P.T. (2016). Crusticorallina gen. nov., a nongeniculate genus in the subfamily Corallinoideae (Corallinales, Rhodophyta). Journal of Phycology 52(6): 929-941.

Nomenclatural notes
The ICBN rules cited below are those adopted by the Seventeenth International Botanical Congress, Vienna, Austria, July 2005 (McNeill et al. 2006).

In accordance with ICBN Art 13.3, the name Mesophyllum M. Lemoineis treated as pertaining to a non-fossil taxon because its type is based on a non-fossil specimen. Both non-fossil and fossil species have been assigned to the genus.

The generic name Mesophyllum is typified (ICBN Art 10.1) by the type of M. lichenoides, the designated lectotype species of Mesophyllum and one of 16 species Lemoine (1928) originally included in the genus.

Woelkerling & Irvine (1986) designated a specimen in the Natural History Museum, London (BM, Algal Box Collection 1658) as neotype of Mesophyllum lichenoides. Woelkerling & Irvine (2007) noted, however, that subsequent changes in the International Code of Botanical Nomenclature meant that this neotypification had to be superseded, and they lectotypified the species with an original protologue illustration (Ellis 1768, pl. 17, fig. 9) and then designated the specimen in BM Algal Box Collection 1658 (depicted in Woelkerling & Irvine 1986: figs 1D, 3, 4) as epitype. - (26 Aug 2009) -

Lectotype species Mesophyllum lichenoides (Ellis) Lemoine, 1928c designated by Ishijima, 1942 (Aguirre et al. 2012). - (3 Oct 2012) - Wendy Guiry

Description:

Plants calcified, lacking genicula, entirely pseudoparenchymatous; encrusting to warty, lumpy, fruticose, discoid, layered or foliose; epigenous and growing partially to completely attached to the surface of various substrates (e.g. algae, sponges, molluscs, rock), or growing unattached and free-living as rhodoliths; haustoria unknown.

Thallus organization generally dorsiventral in crustose portions but more or less radial in branches; thallus construction monomerous throughout, consisting of a single system of branched laterally coherent filaments that contribute to a ventral or central core and a peripheral region where portions of core filaments or their derivatives curve outwards towards the thallus surface; coaxial growth (in which cells of adjacent filaments in core region are aligned in arching tiers) reportedly present in most species to varying degrees. Most filaments usually terminating at the thallus surface in epithallial cells (generally one per filament); outermost walls of epithallial cells rounded or flattened but not flared at the corners; cell elongation occurring mainly within actively dividing subepithallial initials that are usually as long as or longer than their immediate inward derivatives. Cells of adjacent filaments linked by fusions; secondary pit-connections unknown.

Gametangia (where known) and carposporangia (where known) developing in uniporate conceptacles. Spermatangia (male gametangia) and carpogonia (female gametangia) produced in separate conceptacles; male and female conceptacles formed on the same or on different plants. Spermatangia (where known) formed on unbranched filaments that arise from the conceptacle chamber floor and roof; spermatangial initials (where known) at first each overlain by a ‘protective cell’ that soon degenerates; spermatangial conceptacle roof formation (where known) occurring centripetally from groups of vegetative filaments peripheral to developing spermatangial filaments on the conceptacle chamber floor. Carpogoina (where known) terminating 2-4 celled unbranched filaments that arise from the conceptacle chamber floor. Carposporophytes (where known) developing in carpogonial conceptacles after presumed fertilization; mature carposporophytes apparently lacking a large conspicuous central fusion cell but composed of an irregularly shaped fusion cell or a several-celled fusion-cell-complex (not always evident) and possessing several-celled filaments bearing terminal carposporangia.

Tetrasporangia/bisporangia formed in conceptacles on separate plants from gametangia and carposporangia. Roofs of tetrasporangial/bisporangial conceptacles multiporate and composed of cells. Tetrasporangia each containing four zonately arranged spores and producing an apical plug that blocks a roof pore before spore release. Bisporangia each containing two spores but otherwise similar to tetrasporangia.

Information contributed by: Wm. J. Woelkerling. The most recent alteration to this page was made on 14 Dec 2017 by M.D. Guiry.

Characters considered diagnostic of Mesophyllum: Mesophyllum is the only known genus of Hapalidiaceae, Subfamily Melobesioideae with: 1) monomerous thallus construction throughout; 2) epithallial cells with outermost walls rounded or flattened but not flared at the corners; 3); subepithallial initials usually as long as or longer than their immediate inward derivatives; 4) haustoria unknown; 5) spermatangia formed on unbranched filaments that arise from the conceptacle chamber floor and roof; 6) spermatangial initials overlain by a layer of protective cells during early stages of development; and 7) spermatangial conceptacle roof formation occurring centripetally from groups of vegetative filaments peripheral to the spermatangial filaments.

As noted by Woelkerling & Harvey (1992: 395-397, Table 2), distinctions between Mesophyllum, Synarthrophyton, and Clathromorphum currently are based on differences in spermatangial filaments (unbranched in Mesophyllum and Clathromorphum; branched & unbranched in Synarthrophyton); the occurrence of protective cells associated with young spermatangial initials (present in Mesophyllum and Synarthrophyton; unknown in Clathromorphum), and spermatangial conceptacle roof development (centripetal from groups of vegetative filaments peripheral to spermatangial filaments in Mesophyllum and Synarthrophyton; but vertical from continued meristematic activity in filaments that form the spermatangial initials in Clathromorphum). These character states have been confirmed to occur in the type species of Mesophyllum and Synarthrophyton, but male conceptacles remain unknown in C. compactum, the type species of Clathromorphum (see Lebednik 1977: 69-71, 107). In addition, the use of spermatangial filament branching to separate Mesophyllum from Synarthrophyton requires further study (see Keats & Chamberlain 1997: 77; Keats & Maneveldt 1997: 465-466; Woelkerling 1996: 201). The assignment of species for which male conceptacles are unknown to any of the above genera therefore appears equivocal. See AlgaeBase entries for Clathromorphum and Synarthrophyton for further information on those genera.

Similarly the presence or absence of coaxial growth at best provides limited indication of generic affinity. Species lacking coaxial growth occur in all three genera, while species with at least some coaxial growth occur in both Mesophyllum and Synarthrophyton.

Coaxial growth, once considered diagnostic of Mesophyllum, is no longer used in that capacity (e.g. see Woelkerling & Harvey 1992: 395-396; Keats et al. 2000: 397) for non-fossil species, and, indeed, non-fossil species lacking coaxial growth have been assigned to the genus (e.g. Athanasiadis 1999: 240, 244). For fossil taxa, coaxial growth still remains in use as a generic character on pragmatic grounds (e.g. see Stockar 2000: 416; Braga 2003: 53-55; Iryu et al. 2009: 412-413) because fossil male conceptacles (see below) have yet to be found. As a result, palaeontologists, in the absence of evidence from male conceptacles, continue to place species with multiporate conceptacles, cell fusions and at least some coaxial growth in Mesophyllum although it is not possible to determine unequivocally whether such species belong to Mesophyllum or Synarthrophyton. Both genera include species that possess at least some coaxial growth.

Characters considered diagnostic of higher taxonomic ranks known/presumed to occur in all species of Mesophyllum: 1) calcification in the form of calcite; 2) pit plugs with two cap layers at cytoplasmic faces, the outer cap dome shaped; membrane absent; 3) cell walls impregnated with calcite; 4) gametangia and carposporangia produced within uniporate conceptacles; 5) tetrasporangia/bisporangia produced within conceptacles and possessing zonately arranged spores; 6) tetrasporangial/bisporangial conceptacles possessing multiporate plates or roofs; 7) tetrasporangia/bisporangia producing apical plugs; 8) tetrasporangial/bisporangial conceptacles with multiporate roofs composed of cells; lacking an acellular multiporate plate recessed below a single outer opening; and 9) cells of contiguous vegetative filaments linked exclusively by cell fusions. Characters 1-2 are considered diagnostic of the Corallinophycidae, 3-5 of the Corallinales, 6-7 of the Hapalidiaceae, and 8-9 of the Melobesioideae.

Comments: Information on the taxonomic history, nomenclature, and other matters associated with the name Mesophyllum is contained in Woelkerling (1988: 193-195). Growth form terminology (encrusting, lumpy, fruticose, etc.) follows Woelkerling et al. (1993).

An account of the epitype specimen of M. lichenoides (J. Ellis) M. Lemoine, the lectotype species of Mesophyllum, is presented in Woelkerling & Irvine (1986); additional data on isoepitype material (LTB 16595) are provided in Woelkerling & Harvey (1993: 596 & figs 30A-30B).

The types and other specimens of most species currently referred to Mesophyllum need to be re-examined in detail to verify whether generic placement is correct, to re-assess whether recognition as a distinct species is justified, to understand more fully the extent of infraspecific morphological and anatomical variation, and to determine the diagnostic characters that separate each species from others within the genus. At present, most species assigned to Mesophyllum are poorly or incompletely known.

Biogeographically, Mesophyllum appears to be widespread, but many records require confirmation.

The lists below of diagnostic characters of Mesophyllum, and of the higher taxa to which it belongs, are derived from data in Harvey, Broadwater, Woelkerling & Mitrovski (2003), Harvey, Woelkerling & Millar (2003), Le Gall & Saunders (2007), Woelkerling et al. (2008: 282) and/or Le Gall et al. (2009). Diagnostic characters are those that taken together distinguish a taxon from others of the same taxonomic rank (e.g. characters distinguishing Mesophyllum from other genera of the Hapalidiaceae, subfamily Melobesioideae). Harvey, Woelkerling & Millar (2003: 653) also provide a diagnostic comparison of Mesophyllum with other currently recognized non-fossil genera of Melobesioideae.

Numbers of names and species: There are 145 species names in the database at present, as well as 15 infraspecific names. Of the species names, 47 have been flagged as accepted taxonomically on the basis of the listed literature under the species name. In some instances, opinions on taxonomic validity differ from author to author and users are encouraged to form their own opinion. AlgaeBase is a work in progress and should not be regarded as a definitive source only as a guide to the literature..

Names: ('C' indicates a name that is 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):

Click here to also show infraspecific names in the list below.

References
Athanasiadis, A. (1999). Mesophyllum macedonis, nov. sp. (Rhodophyta, Corallinales), a putative Tethyan relic in the north Aegean Sea. European Journal of Phycology 34: 239-252, 23 figs, 1 table.

Braga, J.C. (2003). Application of botanical taxonomy to fossil coralline algae (Corallinales, Rhodophyta). Acta Micropalaenotologica Sinica 20: 47-56.

Ellis, J. (1768). Extract of a letter from John Ellis, Esquire, F.R.S. to Dr. Linnaeus of Upsala, F.R.S. on the animal nature of the genus of zoophytes, called Corallina. Philosophical Transactions of the Royal Society of London 57: 404-425, pls XVII, XVIII.

Harvey, A.S., Woelkerling, W. J. & Millar, A.J.K. (2003). An account of the Hapalidiaceae (Corallinales, Rhodophyta) in south-eastern Australia. Australian Systematic Botany 16: 647-698.

Harvey, A.S., Woelkerling, W.J. & Millar, A.J.K. (2009). The genus Amphiroa (Lithophylloideae, Corallinaceae, Rhodophyta) from the temperate coasts of the Australian continent, including the newly described A. klochkovana. Phycologia 48: 258-290.

Heydrich, F. (1904). Stereophyllum, eine neues Genus der Corallinaceen. Beichte der Deutsche Botanischen Gesellschaft 22: 196-199.

Hughey, J.R., Braga, J.C., Aguirre, J., Woelkerling, W.J. & Webster, J.M. (2008). Analysis of ancient DNA from fossil corallines (Corallinales, Rhodophyta). Journal of Phycology 44: 374-383.

Ishijima, W. (1942). The first find of Mesophyllum from the Tertiary of Japan. Journal of the Geological Society of Japan 49: 174-176.

Keats, D.W. & Chamberlain, Y.M. (1997). The non-geniculate coralline algae Synarthrophyton eckloniae (Foslie) comb. nov., and S. magellanicum (Foslie) comb. nov. (Rhodophyta) in South Africa including a comparison with relevant types. European Journal of Phycology 32: 55-79.

Keats, D.W. & Maneveldt, G. (1997). Two new melobesioid algae (Corallinales, Rhodophyta), Synarthrophyton robbenense sp. nov. and S. munimentum sp. nov., in South Africa and Namibia. Phycologia 36: 447-467, 54 figs, 1 table.

Lebednik, P.A. (1977 '1976'). The Corallinaceae of northwestern North America. I. Clathromorphum Foslie emend. Adey. Syesis 9: 59-112.

Le Gall, L. & Saunders, G.W. (2007). A nuclear phylogeny of the Florideophyceae (Rhodophyta) inferred from combined EF2, small subunit and large subunit ribosomal DNA: establishing the new red algal subclass Corallinophycidae. Molecular Phylogenetics and Evolution 43: 1118-1130.

Lemoine, M. (1928). Un nouveau genre de Mélobésiées: Mesophyllum. Bulletin de la Société Botanique de France 75: 251-254.

Mason, L.R. (1953). The crustaceous coralline algae of the Pacific coast of the United States, Canada and Alaska. University of California Publications in Botany 26: 313-389, Plates 27-46.

McNeill, J., Barrie, F.R., Burdet, H.M., Demouline, V., Hawksworth, D.L., Marhold, K., Nicolson, D.H., Prado, J., Silva, P.C., Skog, J.E., Wiersema, J.H. & Turland, N.J. (2006). International Code of Botanical Nomenclature (Vienna Code) adopted by the Seventeenth International Botancial Congress Vienna, Austria, July 2005. pp. [i-iv], v-xviii + 1-568. Liechtenstein: A.R.G. Gantner Verlag.

Mitten, W. (1859). Musci Indiae Orientalis: an enumeration of the mosses of the East Indies. The Journal of the Proceedings of the Linnean Society, Botany 1(suppl.): 1-171.

Stockar, R. (2000). Fossil coralline algae from the Paleocene Montorfano Member type-section (Tabiago Formation, northern Italy). Eclogae Geologicae Helvetiae 93: 409-427.

Woelkerling, W.J. (1988). The Coralline Red Algae: an analysis of the genera and subfamilies of nongeniculate Corallinaceae. pp. i-xi, 1-268, 259 figs, tables numbered by chapter. London & Oxford: British Museum (Natural History) & Oxford University Press.

Woelkerling, W. J. (1996). Subfamily Melobesioideae. In: The Marine Benthic Flora of Southern Australia - Part IIIB. Gracilariales, Rhodymeniales, Corallinales and Bonnemaisoniales. (Womersley, H.B.S. Eds), pp. 164-210. Canberra: Australian Biological Resources Study.

Woelkerling, W.J. & Harvey, A. (1992). Mesophyllum incisum (Corallinaceae, Rhodophyta) in Southern Australia - implications for generic and specific delimitation in the Melobesioideae. British Phycological Journal 27: 381-399.

Woelkerling, W.J. & Irvine, L.M. (1986). The neotypification and status of Mesophyllum (Corallinaceae, Rhodophyta). Phycologia 25: 379-396.

Woelkerling, W.J. & Irvine, L.M. (2007). The genus Mesophyllum (Hapalidiaceae, Corallinales, Rhodophyta): typification update. Phycologia 46: 230-231.

Woelkerling, W.J., Irvine, L.M. & Harvey, A.S. (1993). Growth-forms in non-geniculate coralline red algae (Corallinales, Rhodophyta). Australian Systematic Botany 6: 277-293.

Woelkerling, W.J. & Lamy, D. (1998). Non-geniculate coralline red algae and the Paris Museum: Systematics and scientific history. pp. i-vii, 1-767. Paris: Publications Scientifiques du Muséum/ADAC.

Woelkerling, W.J., Millar, A.J.K., Harvey, A. & Baba, M. (2008). Recognition of Pachyarthron and Bossiella as distinct genera in the Corallinaceae, subfamily Corallinoideae (Corallinales, Rhodophyta). Phycologia 47: 265-293.

Wynne, M.J. & Schneider, C.W. (2010). Addendum to the synoptic review of red algal genera. Botanica Marina 53: 291-299.

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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.

Created: 01 January 2001 by M.D. Guiry

Verified by: 14 December 2017 by M.D. Guiry

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M.D. Guiry in Guiry, M.D. & Guiry, G.M. 2018. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org; searched on 13 December 2018.

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