Gonimoblast Initials Research Articles

Revisiting the systematics of the genera Grateloupia, Phyllymenia, and Prionitis (Halymeniaceae, Rhodophyta) with a description of a new species-Prionitis taiwani-borealis.

The taxonomy of the genera Grateloupia, Phyllymenia, and Prionitis has been revised several times but remains controversial. The anatomy of female reproductive structures in combination with phylogenetic reconstructions is mostly used to define the genera. However, the architecture and behavior of the auxiliary cell ampullae before and after diploidization are not well documented for most species. To fill this knowledge gap, we examined the female reproductive structures of a new species (Prionitis taiwani-borealis sp. nov.) from Taiwan and compared our observations to the species currently placed in the Phyllymenia/Prionitis complex. The female reproductive structures of the Phyllymenia/Prionitis complex are characterized by (1) 2-celled carpogonial branches with the supporting cell being the basal cell of a third-order ampullar filament; (2) auxiliary cell ampullae composed of three orders of unbranched ampullar filaments before diploidization; (3) cells of auxiliary cell ampullar filaments forming a cellular cluster after diploidization and surrounding the developing gonimoblasts; (4) gonimoblast initials produced from the diploidized auxiliary cells before fusing with them; and (5) branched auxiliary cell ampullar and secondary medullary filaments involved in early pericarp formation. A monophyletic relationship of species possessing female structures similar to those of Pr. taiwani-borealis and related species was highly supported based on combined rbcL and LSU rDNA sequence analyses. The female reproductive structures of other species of Grateloupia sensu lato, phylogenetically closely related to the Prionitis and Phyllymenia assemblage, require reinvestigation as correct interpretations of pre- and post-fertilization events have proven to be informative for resolving the systematics of the Halymeniaceae.

The Phyllophoraceae (Gigartinales, Rhodophyta) from Peru with descriptions of Acletoa tarazonae gen. & sp. nov. and Gymnogongrus caespitosus sp. nov.

:We investigated species in the family Phyllophoraceae from Peru using sequences of the plastid rbcL sequences and morphological examination. Here we describe Acletoa tarazonae gen. & sp. nov., characterized by the presence of secondary medullary cells around cystocarps, gonimoblast initials that are downwardly and upwardly directed, and a linear arrangement of gonimoblast filaments on medullary cells. Acletoa tarazonae consistently formed a clade with Ahnfeltiopsis vermicularis and Chilean Gymnogongrus sp., and this clade was distinct from other genera in the Phyllophoraceae in the rbcL phylogeny. We also describe a new species of the Phyllophoraceae, Gymnogongrus caespitosus sp. nov., from northern Peru, characterized by a semirigid and flattened thallus, narrow branches, absence of hair cells, and cystocarps immersed in a single cavity. Ahnfeltiopsis concinna was not distinct from Ahnfeltiopsis durvillei, and consistently grouped in the genus Gymnogongrus sensu stricto in the rbcL phylogeny. A new combination of Gymnogongrus durvillei comb. nov. was made on the basis of A. durvillei, and A. concinna was merged with G. durvillei.

A phylogenetic re-appraisal of the family Liagoraceae sensu lato (Nemaliales, Rhodophyta) based on sequence analyses of two plastid genes and postfertilization development.

The marine red algal family Liagoraceae sensu lato is shown to be polyphyletic based on analyses of a combined rbcL and psaA data set and the pattern of carposporophyte development. Fifteen of eighteen genera analyzed formed a monophyletic lineage that included the genus Liagora. Nemalion did not cluster with Liagoraceae sensu stricto, and Nemaliaceae is reinstated, characterized morphologically by the formation of the primary gonimolobes by longitudinal divisions of the gonimoblast initial. Yamadaella and Liagoropsis, previously placed in the Dermonemataceae, are shown to be independent lineages and are recognized as two new families Yamadaellaceae and Liagoropsidaceae. Yamadaellaceae is characterized by two gonimoblast initials cut off bilaterally from the fertilized carpogonium and diffusely spreading gonimoblast filaments. Liagoropsidaceae is characterized by at least three gonimoblast initials cut off by longitudinal septa from the fertilized carpogonium. In contrast, Liagoraceae sensu stricto is characterized by a single gonimoblast initial cut off transversely or diagonally from the fertilized carpogonium. Reproductive features, such as diffuse gonimoblasts and unfused carpogonial branches following postfertilization, appear to have evolved on more than one occasion in the Nemaliales and are therefore not taxonomically diagnostic at the family level, although they may be useful in recognizing genera.

Entwisleia bella, gen. et sp. nov., a novel marine ‘batrachospermaceous’ red alga from southeastern Tasmania representing a new family and order in the Nemaliophycidae

A new family, genus and species in the new order Entwisleiales of the subclass Nemaliophycidae are described for a subtidal marine red alga (Entwisleia bella F.J. Scott, G.W. Saunders & Kraft) from Tasmania in Australia’s cool-temperate southeast. Thalli are uniaxial, the stout cells of the single central-axial filament bearing varying numbers of whorled periaxial cells and fascicles of determinant cortical filaments at their distal poles, as well as dense aggregates of secondary internodal filaments arising perpendicularly on basipetal rhizoids that issue from periaxial cells. Plants are dioecious, the spermatangia sessile on distal bearing cells of primary and secondary cortical filaments. Carpogonial branches are four- to eight-celled and directed outwardly from the thallus, and produce simple to highly branched laterals from subhypogynous cells. Presumed fertilization results in several gonimoblast initials being cut from the lateral surface of the carpogonium by vertical cross walls, the ensuing gonimoblasts forming a compact carposporophyte subtended by, but not mixed with, the sterile filaments on the carpogonial branch. Terminal carposporangia form across the surface layer of the gonimoblasts and a fusion cell is not produced. The thalli are particularly batrachospermaceous in vegetative and reproductive morphology, a highly anomalous phenomenon considering that the Batrachospermales is an order totally confined to freshwater habitats. Despite the morphological and anatomical similarities to Batrachospermum and closely related genera, the consensus of multigene sequence analyses indicates that the new genus forms a sister clade to the Colaconematales, even though the members of that group differ in virtually every aspect of habit and anatomy from the gametophytic thalli of Entwisleia.

Molecular phylogeny and developmental studies of Apoglossum and Paraglossum (Delesseriaceae, Rhodophyta) with a description of Apoglosseae trib. nov.

Our morphological and molecular studies indicate that species from the southern hemisphere previously placed in Delesseria belong in Paraglossum and that Paraglossum and Apoglossum comprise a separate tribe, the Apoglosseae, S.-W. Lin, Fredericq & Hommersand, trib. nov., within the family Delesseriaceae. From a vegetative perspective the Apoglosseae is readily recognized because some or all fourth-order cell rows are formed on the inner sides of third-order cell rows. All fourth-order cell rows grow adaxially in Apoglossum, whereas both adaxial and abaxial cell rows are present in Paraglossum. Periaxial cells do not divide in Apoglossum, whereas they divide transversely in Paraglossum in the same way as in Delesseria. Major branches are formed mainly from the margins of midribs in the Apoglosseae. The procarp consists of a straight carpogonial branch and two sterile cells, with the second formed on the same side as the first. The carpogonium cuts off two connecting cells in tandem from its apical end, the terminal cell being nonfunctional and the subterminal cell typically fusing with the auxiliary cell. Gonimoblast filaments radiate in all directions from the gonimoblast initials and produce carposporangia terminally in branched chains, with pit connections between the inner gonimoblast cells broadening and enlarging. The auxiliary cell, supporting cell, and sterile cells unite into a fusion cell, which remains small in Apoglossum but incorporates the branched inner gonimoblast filaments and cells in the floor of the cystocarp in Paraglossum. Elongated inner cortical cells seen in mature cystocarps in the Delesserieae are absent in the Apoglosseae. Phylogenetic studies based on rbcL (RuBisCO large subunit gene) sequence analyses strongly support the recognition of the Apoglosseae within the subfamily Delesserioideae of the Delesseriaceae, in agreement with our previous observations based primarily on analyses of large subunit ribosomal DNA (LSU).

New features in the vegetative and reproductive morphology of Cystoclonium purpureum (Cystocloniaceae, Rhodophyta) from the North Atlantic Ocean

The seminal work of Kylin (1923, 1932, 1956) defined the family Cystocloniaceae (as the Rhodophyllidaceae) for genera having (1) a percurrent central-axial filament surrounded by a well-developed cortex; (2) procarps in which the auxiliary cell is one of the daughter cells borne immediately distal to the supporting cell of the carpogonial branch; (3) gonimoblast filaments that originate from a single initial directed either inwardly or laterally; and (4) zonately divided tetrasporangia. Most of the species currently placed in the Cystocloniaceae produce some kind of secondary gametophytic filaments in conjunction with gonimoblast development, although no such filaments have been reported in Cystoclonium purpureum or C. obtusangulum, the only two species currently recognized under Cystoclonium. Unlike the reports of previous studies, we observed an extensive system of short-celled secondary gametophytic filaments in C. purpureum that form regularly in association with gonimoblast initiation and continue their elaboration throughout gonimoblast and carposporangial development. Terminal cells of the secondary gametophytic filaments fuse with nearby fused and unfused gonimoblast cells throughout carposporophyte development. Secondary gametophytic filaments of one sort or another have been reported in nearly all other species placed in the Cystocloniaceae–Solieriaceae complex, often with linkage occurring between cells of the gonimoblast filaments and those of the secondary gametophytic filaments; however, the particular pattern of gametophyte–gonimoblast interaction described here in C. purpureum is, so far, unique among Rhodophyta.

A NEW METHOD OF CYSTOCARP DEVELOPMENT IN THE RED ALGAL GENUS CALLOPHYLLIS (KALLYMENIACEAE) FROM CHILE(1).

Traditional studies suggest that the Kallymeniaceae can be divided into two major groups, a nonprocarpic Kallymenia group, in which carposporophyte formation involves an auxiliary cell branch system separate from the carpogonial branch system, and a procarpic Callophyllis group, in which the carpogonial branch system gives rise to the carposporophyte directly after fertilization. Based on our phylogenetic studies and unpublished observations, the two groups each contain both procarpic and nonprocarpic genera. Here, we describe a new method of reproductive development in Callophyllis concepcionensis Arakaki, Alveal et Ramírez from Chile. The carpogonial branch system consists of a supporting cell bearing both a three-celled carpogonial branch with trichogyne and two-lobed "subsidiary" cells. After fertilization, large numbers of secondary subcortical and medullary cells are produced. Lobes of the carpogonial branch system cut off connecting cells containing enlarged, presumably diploid nuclei that fuse with these secondary vegetative cells and deposit their nuclei. Derivative enlarged nuclei are transferred from one vegetative cell to another, which ultimately cut off gonimoblast initials that form filaments that surround the central primary medullary cells and produce carposporangia. The repeated involvement of vegetative cells in gonimoblast formation is a new observation, not only in Callophyllis, but in red algae generally. These results call for a revised classification of the Kallymeniaceae based on new morphological and molecular studies.

Grammephora peyssonnelioides gen. et sp. nov. (Rhodophyta, Rhodymeniaceae) from the Solomon Islands, South Pacific

SUMMARYA new genus and species of red alga in the Rhodymeniaceae, Grammephora peyssonnelioides, is described from both shallow and deepwater habitats in the Solomon Islands, South Pacific. The new genus and species is characterized by prostrate overlapping lobes with a strongly cartilaginous flexible texture, distinct surface linear markings perpendicular to the growing margins, and a compact three to four celled medulla of relatively small refractive cells. Tetrasporangia are elongate and decussately divided, and occur in large scattered dorsal surface sori. Cystocarps are prominent and conical, on the dorsal surface of the blade, with a network of nutritive filaments and basal nutritive tissue around the suspended, centrally located carposporophyte, with all gonimoblast initials becoming carposporangia. The columnar fusion cell is uniquely crowned by a ring of discoid cells of nonalgal origin.

Ultrastructure of post-fertilization development in the red alga Callophyllis linearis (Kallymeniaceae, Cryptonemiales, Rhodophyta)

The ultrastructure of post-fertilization development of the red alga Callophyllis linearis (Kyl.) Abb. & Norr. of the Kallymeniaceae showed that the Kallymeniaceae are more closely related to the Cryptomeniales than to the Gigartinales. The auxiliary cell produces multinucleate gonimoblast initials which divide to produce generative gonimoblast cells. These cells undergo repeated cleavages to form clusters of carpospore initials, which finally differentiate into carpospores. Carpospore differentiation is simple and occurs in three developmental stages. In the first stage, young carpospores are avacuolate, contain a large nucleus, have few undeveloped plastids and exhibit incipient dictyosome activity. During the intermediate stage, plastids develop their internal thylakoid system, starch granules are formed and dictyosomes continue to produce vesicles that contribute carpospore wall material. The formation of fibrous vacuoles originates from the fibrous vacuole associated organelles (FVAOs). In the final stage, mature carpospores form cored vesicles. They also contain well-developed plastids, fibrous vacuoles, numerous starch granules and are surrounded by a two-layered carpospore wall.

The Liagoraceae (Nemaliales, Rhodophyta) of the Hawaiian Islands II: the species of Liagora with quadripartite carposporangia, including descriptions of L. donaldiana sp. nov. and L. julieae sp. nov.

The Hawaiian species of Liagora with quadripartite carposporangia are described, including two new species, L. donaldiana and L. julieae, and the previously described L. perennis. Liagora donaldiana is characterized by a coarse thallus with distinct annulations and, at the anatomical level, outer cortical cells that are large and clavate.Liagora julieae is distinguished by the production of gonimoblast initials from both cells of the divided zygote (= postfertilization carpogonium). Liagora perennis is described in detail, and features allowing it to be distinguished from the closely related (but with undivided carposporangia) L. divaricata are highlighted. All species conform to the genus Liagora (sensu stricto), in which cortical filaments are much divided and the gonimoblast is moderately diffuse, with sterile filaments intermingling with or loosely enveloping the fertile filaments.

Ultrastructure of auxiliary and gonimoblast cells during carposporophyte development in the red alga Cryptopleura ruprechtiana (Delesseriaceae, Ceramiales, Rhodophyta)

The ultrastructure sequence for the complete post-fertilization development is described in Cryptopleura ruprechtiana (C. Agardh) Kylin, a member of the Delesseriaceae. Following fertilization the diploid nucleus is transferred to the auxiliary cell. This contains typical red algal proplastids, cytoplasmic concentric membranes, numerous small vacuoles and lipid bodies. Crystalline inclusions and virus-like particles are also present. In addition darkly staining spherical masses possibly represent dehydrated haploid chromatin. The multinucleate auxiliary cell produces initially one large gonimoblast initial and subsequently many smaller gonimoblast initials. The first formed generative gonimoblast cell is similar in cellular structure to the auxiliary cell. Gonimoblast initials are uninucleate but through caryokinesis they become multinucleate. They undergo repeated cleavage to form more gonimoblast cells. Subsequent, centripetal cytokinesis results in the formation of clusters of gonimoblast cells. A new type structural cap or association is observed in the septal plugs that interconnect gonimoblast initials. Terminal or generative gonimoblast cells cleave to form additional gonimoblast cells. Only terminal gonimoblast cells are differentiated to carpospores.

The Liagoraceae (Rhodophyta: Nemaliales) of the Hawaiian Islands. 1: First Record of the Genus Gloiotrichus for Hawai'i and the Pacific Ocean

Gloiotrichus fractalis Huisman & Kraft is documented for the first time from the island of Hawai'i, Hawaiian Islands, which also represents the first record for the Pacific Ocean. The single specimen on which the record is based is 12 cm in height, extremely mucilaginous, with percurrent primary axes and irregularly arranged lateral branches. Carpogonial branches are borne on the basal one to three cells of cortical fascicles; when mature they are five to eight cells long and straight. Before fertilization, cells of the carpogonial branch produce several lateral branches similar in morphology to cortical filaments. After presumed fertilization the zygote (= postfertilization carpogonium) divides transversely and gonimoblast initials are produced from both of the resultant cells. Mature carposporophytes are spherical, with terminal carposporangia and a fusion cell formed from the cells of the carpogonial branch and basal cells of lateral filaments. The Hawaiian specimen is identical in virtually all respects to those from the Indian Ocean type locality in the Houtman Abrolhos Islands of Western Australia.

Ultrastructure of post-fertilization development in the red alga Scinaia articulata (Galaxauraceae, Nemaliales, Rhodophyta)

The ultrastructure of the carposporophyte and carposporogenesis is described for the red alga Scinaia articulata Setch. After fertilization, the trichogyne disappears, and the pericarp develops to form a thick protective tissue that surrounds the carposporophyte. The hypogynous cell cuts off both one-celled and two-celled sterile branches. Patches of chromatin are frequently observed in evaginations of the nuclear envelope, which appear to produce vesicles in the cytoplasm of the cell of the sterile branch. Large gonimoblast lobes extend from the carpogonium and cleave to form gonimoblast initials. Subsequently, a fusion cell is formed from fusions of the carpogonium, the hypogynous cell and the basal cell of the carpogonial branch. The mature carposporophyte comprises the fusion cell that is connected to the sterile branch cells, gonimoblast cells and carpospores and is surrounded by extensive mucilage. Young carpospores possess a large nucleus and proplastids with a peripheral thylakoid, but they have few dictyosomes and starch granules and are indistinguishable from gonimoblast cells. Subsequently, dictyosomes are formed, which produce vesicles with an electron-dense granule, which indicates an initiation of wall deposition. Thylakoid formation coincides with incipient starch granule deposition. The nuclear envelope produces fibrous vacuoles and concentric membrane bodies. Carpospores are interconnected by pit connections with two cap layers. Dictyosome activity increases, resulting in the production of vesicles, which either continue to deposit wall material or coalesce to form fibrous vacuoles. The final stage of carposporogenesis is characterized by the massive production of cored vesicles from curved dictyosomes. Mature carpospores are uninucleate and contain fully developed chloroplasts, numerous cored vesicles, numerous starch granules and fibrous vacuoles. The mature carpospore is surrounded by a wall layer and a separating layer, but a carposporangial wall is lacking.

New Insights in the Cryptonemiales–Rhodymeniales Complex and Resurrection of the Allied Red Algal Order Nemastomatales Kylin 1925 as Inferred From rbcL Sequence Analysis and Comparative Reproductive Morphology

AbstractIn a global molecular phylogeny of florideophycean red algae inferred from chloroplast‐encoded rbcL sequence analysis, a major monophyletic assemblage comprises the Cryptonemiales (=Halymeniales), the Rhodymeniales, the Schizymeniaceae (Schizymenia, Titanophora, Platoma) and the Nemastomataceae (Nemastoma, Predaea). The phylogenetic significance of the auxiliary cell and its interaction with the fertilized egg cell in this assemblage is discussed in relation to established and newly proposed classification schemes. The order Nemastomatales Kylin 1925 is reinstated and emended to contain the nonprocarpic Schizymeniaceae and Nemastomataceae. Unifying characters of the Nemastomatales include fertilized carpogonia that may establish fusions with carpogonial nutritive cells prior to the formation of septate connecting filaments, and simple gonimoblasts developing outwardly from auxiliary cells or from connecting filaments in their vicinity. The auxiliary cell is a transformed vegetative intercalary cell (Sebdeniaceae), that becomes surrounded by either clusters of nutritive cells (Nemastomataceae), involucral filaments (Schizymeniaceae) or by three‐dimensional ampullary filaments (Halymeniaceae including the Corynomorphaceae), or is part of a procarp (Rhodymeniales). The homology of outward gonimoblast initiation and maturation into a simple ball of carposporangia in the Cryptonemiales, Rhodymeniales and Nemastomatales will be illustrated.

Vegetative and reproductive morphology of Dudresnaya canariensis sp. nov. (Dumontiaceae, Rhodophyta)

The marine red alga Dudresnaya canariensis sp. nov. (Dumontiaceae, Gigartinales) from the Canary Islands is described. Gametophytes are terete and radially branched, young branches are nonannulate, outer cortical cells are cylindrical, axial cells contain hexagonal crystals, cells of primary axes are conspicuous, and rhizoids reach 95 μm in diameter. Spermatangial mother cells occur in corymbose clusters on the outer cortex, and carpogonial and auxiliary-cell filaments, both of which lack a thick mucilage coat, arise in the mid-cortex. Carpogonial filaments are reflexed, the carpogonium and trichogyne differentiating after final oblique division. The gonimoblast initials do not recurve around the auxiliary-cell filament, and the cystocarps are distinctly cleft. Tetrasporophytes are unknown. The only unique feature of D. canariensis is the arrangement of its spermatangia in corymbose terminal and subterminal fascicles, a feature unreported in the few species of Dudresnaya where male gametophytes are known. However, D. canariensis differs from the other Dudresnaya species by a unique combination of significant attributes. It is postulated that the Australian D. capricornica and the Japanese D. kuroshioensis are the closest relatives of the new species.

Reproductive morphology ofEucheumagelatinae (Esper) J. Agardh (Solieriaceae, Gigartinales, rhodophyta)

Eucheuma gelatinae (Esper) J. Agardh has vegetative and reproductive features distinguishing it from other species ofEucheuma. The occurrence of reproductive nemathecia containing carpogonial branches, auxiliary cells and post-fertilization stages including gonimoblast and pericarp initiation, fusion cell formation stages and carposporophyte development are described and ilustrated for the first time for this species.

Carposporangial development in the red alga Scinaia pseudocrispa ( S. forcellata) from India

The three-celled carpogonial branch of Scinaia pseudocrispa (Clemente) Wynne ( S. forcellata Bivona-Bernardi) consists of a basal cell, a hypogynous cell and a carpogonium. After fertilisation, the trichogyne severs and shrivels. The zygote nucleus is transferred from the carpogonium to the hypogynous cell. The gonimoblast initials arise from the hypogynous cell. A polysaccharidic envelope provides an isolated and protective environment for the carposporophyte and thus enables it to develop within the confines of the gametophyte. The carpospores are released through a well developed ostiole.

The red algal genus Liagora (Liagoraceae, Rhodophyta) from the Canary Islands

Eight species of the genus Liagora (Liagoraceae, Rhodophyta) are reported from the Canary Islands. Six of these (L. viscida (Forsskål) C. Agardh, L. distenta (Mertens) Lamouroux, L. gymnarthron Børgesen, L. canariensis Børgesen, L. maderensis Kützing and L. tetrasporifera Børgesen) are endemic to the NE Atlantic and Mediterranean and two (L. valida Harvey and L. ceranoides Lamouroux) have a wide distribution. L. maderensis, known only from the type collection and often cited as a synonym for L. ceranoides or L. valida, has a reproductive and vegetative morphology that supports its recognition as an independent species. Evidence suggests that L. gymnarthron has often been erroneously identified as L. distenta (Mertens) Lamouroux and that the latter species has thus been characterized by a combination of features from two different taxonomic entities. Although closely related, the two species show distinctive differences in the morphology of their cystocarps: in L. distenta sterile filaments persist under the gonimoblast and do not surround the mature carposporophyte, while in L. gymnarthron mature carposporophytes are surrounded by a conspicuous involucre. Habit, vegetative and reproductive development have been examined in the eight species. The previously controversial reproductive development in L. viscida, the lectotype species of the genus, has been clarified. Gametophytes of L. viscida are monoecious and, after presumed fertilization, cells adjacent to the supporting cell form sterile colourless filaments that grow and branch towards the thallus surface; simultaneously gonimoblast initials produce outwardly radiating lax gonimoblast filaments that form terminal carposporangia, resulting in a mature carposporophyte with sterile filaments intermingled with the gonimoblast filaments. The features used at present to delineate the genus Liagora in the Liagoraceae are analysed and the potential use of post-fertilization characters to subdivide the genus is discussed.

Dudresnaya kuroshioensis sp. nov. (Dumontiaceae, Rhodophyta) from Japan

The marine red alga Dudresnaya kuroshioensis sp. nov. (Dumontiaceae, Rhodophyta) is described from southernmost Honshu, Japan. It is a deep-water species with the following characters: terete, radially branched and not villose thalli, hexagonal crystals in axial cells, hairs, distinct primary axes, cylindrical outer cortical cells, rhizoids up to 21 μm in diameter, carpogonia once obliquely or transversely divided, a distinctly cleft cystocarp and an isomorphic alternation of generations. It lacks annulations in young branches, indeterminate-axis primordia, rhizoids with cortical laterals, a mucilage coat around the carpogonial and auxiliary-cell filaments; gonimoblast initials mayor may not be recurved around their auxiliary-cell filaments.Dudresnaya kuroshioensis is compared to Japanese, Austral-Pacific and North American species that most resemble it anatomically but differ in at least one significant character. It is concluded that the Australian D. capricornica is probably the closest relative of the new species, differing mainly in overall size, rhizoid diameter and the anatomy of the mature cystocarp.

Studies of the Liagoraceae (rhodophyta) of Western Australia:Gloiotrichus fractalisgen. et sp. nov. andGanonema helminthaxissp. nov.

Two new taxa of Liagoraceae (Nemaliales) are described from Western Australia. Gloiotrichus fractalis gen. et sp. nov. has been collected from 3–20 m depths at the Houtman Abrolhos, Western Australia. Plants are calcified, extremely lubricous, and grow to 17 cm in length. Carpogonial branches are straight, 6 or 7 cells in length, arise from the basal or lower cells of cortical fascicles, and are occasionally compound. Branched sterile filaments of narrow elongate cells arise on the lower cells of the carpogonial branch prior to gonimoblast initiation, at first on the basal cells, then on progressively more distal cells. Following presumed fertilisation the carpogonium divides transversely, with both cells giving rise to gonimoblast filaments. The distal cells of the carpogonial branch then begin to fuse, with fusion progressing proximally until most of the cells of the carpogonial branch are included. As fusion extends, the filaments on the carpogonial branch are reduced to the basal 2 or 3 cells. The gonimoblast is compact and bears terminal carposporangia. Spermatangial clusters arise on subterminal cells of the cortex, eventually displacing the terminal cells. The sequence of pre- and post-fertilisation events occurring in the new genus separates it from all others included in the Liagoraceae, although it appears to have close affinities with the uncalcified genus Nemalion. Ganonema helminthaxis sp. nov. was collected from 12 m depths at Rottnest Island, Western Australia. Plants are uncalcified and mucilaginous, the axes consisting of a few (< 10) primary medullary filaments, each cell of which gives rise to a cortical fascicle at alternate forks of the pseudodichotomies borne on successive medullary cells. Subsidiary (adventitious) filaments and rhizoids comprise the bulk of the thallus. Carpogonial branches are straight, (3-)4(-6) cells in length, arise on the basal 1–4 cells of the cortical fascicles, and are frequently compound. Carposporophytes develop from the upper of two daughter cells formed by a transverse division of the fertilised carpogonium. Ascending and descending sterile filaments girdle the carpogonial branch cells and arise mostly on the supporting cell prior to fertilisation. Ganonema helminthaxis is the first completely non-calcified member of the genus, and its reproductive and vegetative morphology supports the recognition of Ganonema as a genus independent from Liagora. Liagora codii Womersley is a southern Australian species displaying features of Ganonema, to which it is transferred.