Tetrasporangial Conceptacle Research Articles

Cryptic Diversity of Mediterranean Neogoniolithon (Corallinales, Corallinophycidae, Rhodophyta)

ABSTRACTNeogoniolithon is a widespread genus of non‐geniculate coralline algae in the Mediterranean Sea. Three vaguely differentiated species have been reported in the region. This study examined the diversity of Neogoniolithon in the Mediterranean by inferring phylogenies using psbA and COI‐5P markers, applying delimitation algorithms and comparing morpho‐anatomies of putative species. In contrast to previous reports, 13 species were delimited from the Mediterranean in two distant clades. Initial observations suggested that tetrasporangial conceptacle size might be used to separate the two clades. Only three species showed fruticose morphologies. Further morpho‐anatomical differentiation was difficult. One species included Mediterranean, Pacific and Atlantic samples, while three other species occurred in the Mediterranean and the Canary Islands. The global tree revealed that most species were geographically restricted. Crypticity in multiple lineages implied a much higher diversity than currently reported, even lacking samples from the eastern Mediterranean. Only sequence data can be used to identify these cryptic lineages. High endemism emphasizes the importance of conservation of coralline algal bioconstructions to prevent extinctions. The presence of cryptic diversity also invites a reassessment of the knowledge on species distributions that are important in conservation planning and management.

Lithophyllum nagaokaense sp. nov. (Corallinales, Corallinophycidae, Rhodophyta): A new rhodolith‐forming non‐geniculate coralline alga from Japan

SUMMARYLithophyllum is a cosmopolitan coralline algal genus with 12 species currently recognized in Japan based on modern morpho‐anatomical taxonomic concepts primarily characterized by having uniporate tetrasporangial and bisporangial conceptacles, the presence of secondary pit‐connections between cells of adjacent filaments and a dimerous thallus construction with a single basal layer of predominantly non‐palisade cells. In the present study, we describe Lithophyllum nagaokaense sp. nov. based on a combination of molecular and morpho‐anatomical data of specimens from the temperate waters of Japan. The new species forms both attached epilithic thalli and free‐living rhodoliths. Phylogenetic analyses of psbA, rbcL and COI markers resolved L. nagaokaense as an independent species. Morpho‐anatomically, L. nagaokaense resembles Lithophyllum johansenii, originally described from Australia, but distinguished from the latter by the absence of enlarged angular cells occluding pore canals of tetrasporangial conceptacle chambers. Lithophyllum nagaokaense shared a fruticose morphology with Lithophyllum kaiseri, Lithophyllum kuroshioense, Lithophyllum neo‐okamurae, Lithophyllum okamurae, and Lithophyllum pygmaeum from Japan. Of these, L. nagaokaense is the most similar to L. neo‐okamurae in having attached and free‐living thalli with encrusting and warty to lumpy growth forms bearing knobby protuberances that are dichotomously branched or anastomosing. The new species is distinct from other Japanese fruticose species collectively by five tetrasporangial conceptacle chamber characters and the absence of trichocytes. A taxonomic key for identifying Japanese fruticose species is provided. This is the fifth Lithophyllum species and the third rhodolith‐forming species verified by DNA sequencing to be found in Japan.

Chamberlainium (Corallinales, Rhodophyta) in South Africa, an exemplar for the study of coralline algae, description of C. tenue sp. nov., biogeography of the genus, and species keys

• South African Chamberlainium , an exemplar for the study of coralline algal systematics • Description of Chamberlainium tenue, a new cryptic/pseudocryptic species of coralline algae • Integrated taxonomic approach using DNA sequences from historical and field specimens • Keys to all Chamberlainium species in South Africa • Biogeographic considerations Based on plastid encoded DNA sequences from psb A and rbc L markers, a new non-geniculate coralline algal species, Chamberlainium tenue , is described from South Africa that was previously passing under the misapplied name, Spongites yendoi . DNA sequences, supported by the morpho-anatomical character of tetrasporangial conceptacle roof development, placed C. tenue in Chamberlainium , subfamily Chamberlainoideae. Instead of one species, Spongites yendoi , widely distributed across the entire coastline of South Africa, seven molecularly distinct species were present under that name and all belong in Chamberlainium . Three occur in the cooler water Benguela Marine Province, C. capense, C. glebosum , and C. occidentale, the last extending into the Benguela-Agulhas Transition Zone; three occur in the warmer water Agulhas Marine Province, C. tenue, C. cochleare and C. natalense , with the latter two extending into the Benguela-Agulhas Transition Zone; two occur only in the Benguela-Agulhas Transition Zone, C. agulhense and the historically recognized, C. impar . Both the rbc L and psb A phylograms indicate that ancestral taxa gave rise to species found in both warmer and cooler water habitats. Keys to species of South African Chamberlainium are provided for use in both the field and the laboratory. The methodology used to study these Chamberlainium species, that included: 1) DNA sequencing of type specimens to correctly apply names; 2) DNA sequencing of numerous field-collected specimens; and 3) morpho-anatomical observations on these same DNA sequenced specimens, can be an exemplar for resolving the systematics and biogeography of the many unresolved and unstudied species of South African coralline algae.

Morphological and molecular assessment of Lithophyllum okamurae with the description of L. neo-okamurae sp. nov. (Corallinales, Rhodophyta)

ABSTRACT Lithophyllum okamurae has been widely reported in the Pacific Ocean with identification based on morpho-anatomical observations. Two infraspecific taxa, L. okamurae f. okamurae and f. angulare, described from Japan, have been recorded in the temperate region of Japan. We assessed branched Lithophyllum samples morphologically referable to L. okamurae using morpho-anatomical data and DNA sequences (psbA, rbcL and partial LSU rDNA) obtained from herbarium specimens, including type material, as well as recently field-collected material in Japan. The molecular analyses showed that these ‘L. okamurae’ samples contained two species: L. okamurae and a cryptic new species which we describe as L. neo-okamurae sp. nov. Because the holotype of L. okamurae f. angulare was conspecific with original material cited in the protologue of L. okamurae, it is a heterotypic synonym of L. okamurae f. okamurae. Lithophyllum okamurae and L. neo-okamurae were morphologically similar in having warty, lumpy and fruticose thalli and in often forming rhodoliths. Lithophyllum okamurae can be morpho-anatomically distinguished from L. neo-okamurae by the thallus with tapering or plate-like protuberances (knobby protuberances in the latter) and by having smaller tetrasporangial conceptacle chambers (167–314 µm; 248–380 µm in L. neo-okamurae). Our LSU rDNA sequence data from L. okamurae f. angulare (=L. okamurae f. okamurae) was identical to that of the type of L. margaritae, which has nomenclatural priority over L. okamurae. However, considering that psbA and rbcL sequences of L. margaritae type material could not be generated in the present study, we refrain, for the moment, from proposing the taxonomic synonymy between these two taxa until the status of L. margaritae and its synonyms from the type locality (Gulf of California) are clarified.

DNA sequencing reveals three new species of Chamberlainium (Corallinales, Rhodophyta) from South Africa, all formerly passing under Spongites yendoi

Abstract Three new non-geniculate coralline algal species from South Africa are described that were passing under the misapplied name, Spongites yendoi. Based on plastid encoded DNA sequences from psbA and rbcL markers, these species belong in the subfamily Chamberlainoideae. The DNA sequences, supported by the morpho-anatomical character of tetrasporangial conceptacle roof development, placed all three species in the genus Chamberlainium and not Pneophyllum, the only other genus in Chamberlainoideae. In addition to the diagnostic DNA sequences, Chamberlainium capense sp. nov., C. glebosum sp. nov. and Chamberlainium occidentale sp. nov. may be distinguished by a combination of habit, habitat, geographic distribution, and several morpho-anatomical features. Biogeographically all three species are found in the Benguela Marine Province of South Africa, with C. occidentale being the most widespread. Chamberlainium glebosum also has a wide, but disjunct distribution and C. capense is another South African endemic non-geniculate coralline, whose range is restricted to a 43 km stretch of coastline. Thus far, DNA sequences from type specimens of non-geniculate corallines show that only those species whose type localities are from South Africa are correctly applied; all other non-geniculate coralline names are likely misapplied in South Africa.

Rhodolith-forming species of the subfamilies Neogoniolithoideae and Hydrolithoideae (Rhodophyta, Corallinales) from Espírito Santo State, Brazil

The taxonomy of the rhodolith-forming species of non-geniculate coralline algae from the subfamilies Neogoniolithoideae and Hydrolithoideae (Rhodophyta, Corallinales) found from Espírito Santo State, Brazil, was evaluated based on extensive subtidal sampling. A comparative analysis of the Brazilian material to other recently described species lead us to conclude that one relatively well-known species, namely Hydrolithon rupestre, a conferatum species Neogoniolithon cf. brassica-florida and a probably new species of the genus Hydrolithon, are present in the area. All three species can be distinguished by their tetrasporangial or gametangial conceptacle anatomy. This study strengthens the hypothesis that Brazilian rhodolith beds are comparatively more diverse in numbers of rhodolith-forming species than other areas of the world.

The genus Lithophyllum in the north-western Indian Ocean, with description of L. yemenense sp. nov., L. socotraense sp. nov., L. subplicatum comb. et stat. nov., and the resumed L. affine, L. kaiseri, and L. subreduncum (Rhodophyta, Corallinales)

Based on literature, the genus Lithophyllum was represented in the whole Indian Ocean by 14 taxa, mostly in need of revision in a modern context. Molecular analyses integrated with morpho-anatomical comparisons between the recently revised type material of Lithophyllum kotschyanum Unger, and the related infraspecific taxa, lead to a resumption of L. affine, L. kaiseri, and L. subreduncum, and the description of L. socotraense sp. nov., L. yemenense sp. nov., and L. subplicatum comb. et stat. nov. Detailed accounts are provided for each species, including keys, along with information on synonymy, examined collections, distribution, habitat as well as sequence data of the 5’ end of the LSU from the type specimens. The anatomical features of the tetrasporangial conceptacle that were considered collectively diagnostic for species identification are: the mean diameter of the tetrasporangial conceptacles, the length of the pore-canal in the tetrasporangial conceptacles (with the number of cells in roof filaments), the occurrence of a depression at the top of the conceptacle roof in relation to the pore opening, and the number of cells from the floor of the tetrasporangial conceptacle chamber to the thallus surface. This study provides evidence of a previously unsuspected diversity within the Red Sea and NW Indian Ocean species of Lithophyllum.

Neogoniolithon (Corallinales, Rhodophyta) on the Atlantic coast of Mexico, including N. siankanensis sp. nov.

This is the first revision of Neogoniolithon species on the east coast of Mexico based on both DNA sequences (psbA) and morpho-anatomical characters. Nine species names are provisionally applied based on morpho-anatomical comparisons with type specimens or with species descriptions: N. accretum, N. acropetum, N. erosum, N. mamillare, N. propinquum, N. rhizophorae, N. solubile, N. spectabile and N. strictum. For none of these species was type or topotype material sequenced, but all have their type localities in the subtropical or tropical western Atlantic Ocean. Neogoniolithon siankanensis is described on the basis of a distinctive branched thallus, apical tetrasporangial conceptacles and DNA sequence. Another four species are present, each characterized by DNA sequence, but insufficient reproductive material was available to adequately describe these species. A suite of vegetative and reproductive characters can adequately segregate the currently named Mexican east coast Neogoniolithon species, including 1) branched versus unbranched thalli, 2) monomerous versus dimerous construction, 3) disposition of trichocytes, 4) interior dimensions of mature tetrasporangial conceptacles, 5) number of cell layers comprising tetrasporangial conceptacle roof and 6) shape of cells that line tetrasporangial pore canal. Morpho-anatomical descriptions and distributions are provided for all named species.

Spongites yendoi (Foslie) Chamberlain (Corallinales, Rhodophyta) on the coast of Bahia, Brazil

(Spongites yendoi (Foslie) Chamberlain (Corallinales, Rhodophyta) on the coast of Bahia, Brazil). We report the first occurrence of S. yendoi (Foslie) Chamberlain on the northeastern coast of Brazil, and the second record of the species on the Brazilian coast. We collected specimens on two beaches in the cities of Salvador and Camacari, Bahia, Brazil. The species were identified by the presence of monomerous thallus construction, trichocytes arranged in horizontal fields, central columella, and tetrasporangial conceptacle morphometry. Our record extends the distribution range of this species into Brazilian waters.

Fossil semi-endophytic species of Lithophyllum (Corallinaceae, Rhodophyta) from Tahiti, including L. kenjikonishii sp. nov., and their taphonomic signatures

Woelkerling W.J., Iryu Y. and Bassi D. 2013. Fossil semi-endophytic species of Lithophyllum (Corallinaceae, Rhodophyta) from Tahiti, including L. kenjikonishii sp. nov., and their taphonomic signatures. Phycologia 52: 387–397. DOI: 10.2216/13–129.1Fossil specimens of two semi-endophytic species of Lithophyllum, L. kenjikonishii sp. nov. and L. cuneatum (Corallinaceae, Rhodophyta), were discovered in thin sections of ocean floor cores of the last deglacial period (c. 20,000–10,000 years before present) obtained from Tahiti, French Polynesia, during Expedition 310 of the Integrated Ocean Drilling Program. Detailed morphological–anatomical accounts of both species are provided, and their placement in Lithophyllum and the subfamily Lithophylloideae is discussed in relation to recent classification proposals. Lithophyllum kenjikonishii, recorded only from fossil thalli, and L. cuneatum, known from fossil and nonfossil thalli, are readily distinguished in tetrasporangial conceptacle pore canal anatomy and on differences in spermatangial conceptacle chamber anatomy. Both species are semi-endophytic in Hydrolithon onkodes, another species of Corallinaceae. Taphonomic signatures evident in thin sections suggest that the occurrence of L. kenjikonishii, L. cuneatum, or Hydrolithon braganum (another semi-endophyte) growing in H. onkodes may be a reliable reference for identifying shallow-water settings (fore reef, reef flat and lagoon) in coral reef depositional systems within Pleistocene to last deglacial sedimentary successions in the Pacific Ocean. Taphonomic signatures thus have considerable potential as a palaeoecologic proxy in interpreting reef growth history.

A re-description of Lithothamnion crispatum and the status of Lithothamnion superpositum (Rhodophyta, Corallinales)

Basso D., Rodondi G. and Bressan G. 2011. A re-description of Lithothamnion crispatum and the status of Lithothamnion superpositum (Rhodophyta, Corallinales). Phycologia 50: 144–155. DOI: 10.2216/10-20.1After re-examination of the original Hauck's collection, a buried, empty multiporate tetrasporangial conceptacle was detected in the lectotype material of Lithothamnion crispatum. The morphology and anatomy of the type material were compared to freshly collected representative plants from the Mediterranean. In L. crispatum, the five to seven rosette cells surrounding each pore of the tetra/bisporangial conceptacle roof are larger than the normal epithallial cells and undergo degeneration. As a consequence of the disintegration of the outermost cells in filaments surrounding the pore canals, the tetra/bisporangial conceptacle roofs appear pitted with depressions, each one hosting a pore and the surrounding rosette cells. A previous revision of the type material of Lithothamnion superpositum from South Africa showed this same tetra/bisporangial conceptacle roof structure and development, and corresponding vegetative and reproductive characters. These taxa are thus conspecific; therefore, L. superpositum is a younger heterotypic synonym of L. crispatum, the latter having nomenclatural priority. While the type specimen lacked gametangial plants, these are described for representative freshly collected material and found to be dioecious.

The genus Amphiroa (Lithophylloideae, Corallinaceae, Rhodophyta) from the temperate coasts of the Australian continent, including the newly described A. klochkovana

Harvey A.S., Woelkerling W.J. and 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. DOI: 10.2216/08-84.1Studies of Amphiroa (Lithophylloideae, Corallinaceae, Rhodophyta) from the temperate coasts of Australia provide new evidence that differences in tetrasporangial conceptacle pore canal anatomy are diagnostically significant in delimiting species within the genus. Differences in overall morphology and genicular anatomy are also reliable for delimiting species. These data are supported by examination of relevant type specimens. Four species occur in temperate Australian waters. Three (Amphiroa anceps, Amphira beauvoisii, and the newly described Amphiroa klochkovana) occur in southeastern Australia, and three (A. anceps, A. beauvoisii, and Amphiroa gracilis) occur in southern and southwestern Australia. Comparisons of A. beauvoisii and A. anceps have shown that they cannot be separated at species level morphologically but clearly differ in tetrasporangial conceptacle pore canal anatomy. This has important flow-on implications concerning specimen identification, reported geogeographic distribution and putative heterotypic synonymy of the two species. Relevant historical data, a species key and a synoptic description of Amphiroa also are included.

Rhodolith-forming species of Lithophyllum (Corallinales; Rhodophyta) from Espírito Santo State, Brazil, including the description of L. depressum sp. nov.

Villas-Boas A.B., Riosmena-Rodriguez R., Amado-Filho G.M., Maneveldt G.W. and de O. Figueiredo M.A. 2009. Rhodolith-forming species of Lithophyllum (Corallinales; Rhodophyta) from Espírito Santo State, Brazil, including the description of L. depressum sp. nov. Phycologia 48: 237–248. DOI: 10.2216/08-35.1.The taxonomy of the rhodolith-forming species of Lithophyllum (Corallinales, Rhodophyta) found from Espirito Santo State, Brazil, were evaluated based on extensive subtidal sampling. A comparative analysis of the Brazilian material with recently described species lead us to conclude that three known species (Lithophyllum corallinae, L. johansenii, L. stictaeforme) and one species new to science (Lithophyllum depressum Villas-Boas, Figueiredo & Riosmena-Rodriguez) are present in the area. All four species can be distinguished primarily by their tetrasporangial conceptacle roof anatomy. This study has shown that Brazilian rhodolith beds are comparatively more diverse in number of Lithophyllum species than other areas of the world.

Paulsilvella huveorum gen. & sp. nov. (Corallinaceae, Rhodophyta) from the Holocene of Somalia and Kenya, with a reassessment of Lithothrix antiqua from the Late Pleistocene of Mauritius

A morphological, anatomical and taxonomic account of Paulsilvella Woelkeriing, Sartoni & Boddi gen. nov. (Corallinales, Rhodophyta) is provided. Paulsilvella belongs to the Corallinaceae, subfamily Lithophylloideae sensu lato (encompassing the Amphiroideae) and differs from other lithophylloid genera (Amphiroa, Ezo, the Lithophyllum-Titanoderma complex, Lithothrix, Tenarea) in possessing nongeniculate protuberant branches that resemble a series of fused beads. The branches are entirely monomerous, with a core region composed of single arching tiers of elongate, columnar cells alternating with two tiers of short, noncolumnar cells. Paulsilvella includes one known extant species, P. huveorum Woelkerling, Sartoni & Boddi sp. nov. from Somalia and Kenya, and one known fossil species, P. antiqua (G.F. Elliott) Woelkerling, Sartoni & Boddi comb. nov. from the Late Pleistocene of Mauritius. The latter was originally described as Lithothrix antiqua (‘antiquum’). In P. huveorum, the uniporate carposporangial and tetrasporangial conceptacle chambers are largely buried within the thallus, whereas in P. antiqua they protrude above the surrounding thallus surface. A key to species is provided, and generic relationships within the Lithophylloideae are discussed.

PHYLOGENY AND CLASSIFICATION OF REEF‐BUILDING CORALLINE ALGAE (CORALLINALES, RHODOPHYTA)

The Corallinales includes ca. 40 genera of calcified red seaweeds. Species are of two distinct morphotypes; those that possess genicula (uncalcified nodes) and those that lack genicula. Most nongeniculate species take the form of crusts. The presence (or absence) of genicula, secondary pit connections, and tetrasporangial conceptacle features have traditionally been used as key characters for delimiting coralline subfamilies. In this study, nuclear encoded 18S and 26S rRNA gene sequences were determined and used to reexamine relationships among coralline taxa. Separate and combined phylogenetic analyses of these data yielded similar trees in which four major lineages are resolved. Heydrichia and Sporolithon (Sporolithaceae) are positioned at the base of the tree and appear to be distantly related to other species examined. Within the Corallinaceae, the nongeniculate Melobesioideae is resolved as a monophyletic group. All members of this subfamily produce mutiporate tetraspoangial conceptacles. The Corallinoideae, which are characterized by unizonate genicula, are resolved as sister to a clade containing species placed in the Lithophylloideae, Mastophoroideae and Metagoniolithoideae. The molecular data indicate that geniculate and nongeniculate species characterized by the presence of secondary pit connections are closely related. For example, both data sets robustly support a sister taxon relationship between Amphiroa and Titanoderma. Our results indicate that: 1) all taxa in which secondary pit connections are present should be referred to the Lithophylloideae and, 2) genicula are nonhomologous structures that are independently derived in Amphiroa, Lithothrix, Metagoniolithon and the last common ancestor of the Corallinoideae.

Taxonomic reassessment of rhodolith-forming species of Lithophyllum (Corallinales, Rhodophyta) in the Gulf of California, Mexico

Rhodolith beds (beds composed of unattached coralline red algae) in the Gulf of California, Mexico, are widespread and commonly dominated by specimens belonging to Lithophyllum. The number of rhodolith-forming species of Lithophyllum in these beds, however, has been uncertain, and there are contradictory statements in the recent literature concerning putative species. Five species have been recognized, but it also has been suggested that these represent only a single polymorphic species. More than 700 specimens from 45 localities were examined and compared with all relevant types to determine how many species are represented and how they might be distinguished. Most of the types analyzed agree with the modern concept of Lithophyllum; however, two species, Lithophyllum californiense Heydrich and Lithophyllum bracchiatum (Heydrich) Me.Lemoine, do not agree with the modern concept of Lithophyllum and have been excluded from the genus. None of the characters used previously to delimit species in the group was taxonomically reliable. Moreover, an evaluation of all specimens based on modern characters, especially relating to tetrasporangial conceptacle anatomy, showed that only a single species was present, namely Lithophyllum margaritae (Hariot) Heydrich. Both within and between populations, L. margaritae exhibits a continuum of growth forms: encrusting to foliose to fruticose to warty to lumpy. The dominance of particular growth forms within an area appears to be linked to local environmental conditions.

Lithophyllum insipidum Adey, Townsend et Boykins and L. flavescens sp. nov.: two flat lithophylloid coralline algae (Corallinales, Rhodophyta) abundant in shallow reef environments in Fiji

Two unbranched species of Lithophyllum are characterized from Fiji, South Pacific, where both are common in the shallow reef environment. Lithophyllum insipidum Adey, Townsend et Boykins is characterized by a mainly lavender-colored thallus that is tessellate, with chalky white to brownish patches. Basal filaments are composed of nonpalisade cells that are rectangular prisms shaped like a book. The thallus surface, viewed by scanning electron microscopy, is of the Leptophytum type. Tetrasporangial pores are not blocked by occluding cells, and the tetrasporangial pore canal is lined by papillae that project into the pore canal. The floor of the tetrasporangial conceptacle chamber is six to nine cells deep, and the tetrasporangial conceptacle roof is formed from filaments that originate both peripheral to and central to a ring-shaped fertile area. A columella is present, and tetrasporangia are located at the conceptacle periphery. Tetrasporangial conceptacles are buried in the thallus after their senescence. Lithophyllum flavescens sp. nov. is characterized by a thallus that is mainly brilliant yellow, almost glossy, with a marble-like appearance under low magnification owing to the presence of small areas of low pigment concentration. The basal filaments are composed of mainly book-shaped, nonpalisade cells. The cell surface viewed by scanning electron microscopy is of the Phymatolithon type. Tetrasporangial pores are blocked by enlarged occluding cells that project above the surrounding roof surface in younger conceptacles and degenerate in mature conceptacles. The tetrasporangial conceptacle chamber floor is mainly five or six cells deep. The tetrasporangial conceptacle roof is formed from filaments that originate both peripheral to and central to a ring-shaped fertile area, and a columella is present. Tetrasporangia are located at the conceptacle periphery, and tetrasporangial conceptacles are buried in the thallus following their senescence.

First report of the melobesioid alga (Corallinales, Rhodophyta) Mesophyllum incisum (Foslie) Adey in South Africa

Mesophyllum incisum is reported and studied for the first time in South Africa. It has a thallus surface (SEM) with Leptophytum-type epithallial cells. Tetra/bisparangial conceptacles are mound-like and lack a peripheral rim but have a flattened pore plate. The rosette cells surrounding the tetrasporangial pores are distinct from surrounding roof cells (SEM, surface view) in being narrower, and sunken below the level of the surrounding pore plate. The cells of filaments bordering the tetrasporangial conceptacle pore canal differ from the other roof cells within the pore plate in being more elongate, narrower, and often more densely staining. Pore canal filaments also generally contain fewer cells than the surrounding filaments of the pore plate and the pore canal is more-or-less parallel sided. Our material agrees closely with the species as reported in Australia.

An accoount of southern Australian species of Lithothamnion (Corallinaceae, Rhodophyta)

Lithothamnion (Corallinaceae, Rhodophyta) is represented in southern Australia by at least two species: L. muelleri, the type species of the genus, and L. indicum. Detailed accounts are provided along with a key to the species, and information on distribution, seasonality and habitat, nomenclature and synonymy, and infraspecific taxonomy. Two characters associated with tetrasporangial conceptacle roof anatomy are considered diagnostic of the two southern Australian species. Twenty-five characters used by other authors to separate species of Lithothamnion were examined; none were found to be diagnostic of L. muelleri or L. indicum, and only one (plant habit) was sometimes found to be useful as an ancillary character. None of the measured characters assessed could be used in a diagnostic or ancillary manner. The status and disposition of 22 other specific and infraspecific taxa ascribed to Lithothamnion and reported from southern Australia are summarised; 3 are considered synonyms of L. indicum or L. muelleri, 12 are referable to other genera, 6 are considered to be of uncertain status, and 1 constitutes an unconfirmed record.

Pneophyllum amplexifrons (Harvey) comb. nov., a mastophoroid crustose coralline red algal epiphyte from Natal, South Africa

Abstract Pneophyllum amplexifrons (Harvey) comb. nov. is an epiphytic crustose coralline alga (Rhodophyta, Corallinaceae) of the subfamily Mastophoroideae. It occurs commonly in northern Natal, South Africa and is particularly abundant on intertidal populations of the seagrass Thalassodendron ciliatum (Forsskaring;l) den Hartog. It agrees well with the type specimen of Melobesia amplexifrons Harvey. A germination disc with 8 central cells is present, as usually seen in Pneophyllum. The roof of the tetrasporangial conceptacle forms from filaments surrounding and filaments interspersed among sporangial initials. A pore canal lined with numerous small cells confirms that the species pertains to the mastophoroid genus Pneophyllum. Two diagnostic features of P. amplexifrons are humps of uncalcified filaments at the thallus surface and tapered pore canals in the tetrasporangial conceptacles, lined with small, upward-pointing, non-protruding filaments. Comparison with syntypes of Lithophyllum pseudolichenoides H...