Mature Cystocarps Research Articles

Chondrus retortus (Gigartinales, Rhodophyta) in Hawai‘i: a taxonomic and biogeographic puzzle

Abstract Members of the genus Chondrus are well-known from temperate and cold waters. Chondrus ocellatus Holmes was reported from Hawai‘i Island (19° N latitude) in 1999 as a new record based on vegetative and tetrasporangial characteristics. The first specimens were collected by Setchell in 1900 in Hilo, HI. The presence of a Chondrus species in the subtropics has been a phycological enigma for over 100 years. We addressed the question of species identity and biogeographic affinities of the Hawaiian Chondrus with fresh cystocarpic material, DNA samples, and phylogenetic analyses. Analysis and comparison of five genes (nuclear: EF2; plastid: psbA, rbcL, and 23S/UPA; mitochondrial: COI) from Hawaiian Chondrus and holotype and topotype material of 10 of the 11 accepted Chondrus species indicate that Hawaiian specimens are C. retortus Matsumoto et Shimada. However, unlike type material, the Hawaiian specimens are commonly pinnulate, vary significantly in secondary medullary filament density, and have mature cystocarps filling the entire medullary space. This study shows the value of using multi-gene loci and comparing multiple sequences of several species to confirm taxonomic conclusions. Our findings suggest that C. retortus may have immigrated via rafting on natural floating material or on ships’ hulls. Solving this old puzzle adds new insight into Hawaiian phytogeography.

Gracilaria khanjanapajiae sp. nov. (Gracilariales, Rhodophyta) from the Andaman coast of Thailand

ABSTRACT Taxonomy and diversity of the Gracilariaceae has been increasingly investigated by using integrated morphological and genetic approaches. The Indo-Pacific is likely a hotspot for diversity of these macroalgae. Collections of flattened Gracilaria samples from Natai beach, Andaman coast of Thailand, were morphologically and genetically analysed. Our results clearly indicated the presence of a new species, G. khanjanapajiae sp. nov., in Thailand. In comparison to other known Indo-Pacific flattened species, G. khanjanapajiae can be distinguished by its dentate blade margin, deep spermatangial conceptacles (verrucosa-type) and numerous lateral and basal nutritive filaments within mature cystocarps. This new species resembles G. srilankia in having similar branching pattern and male reproductive structures, but differs in blade margin features. Phylogenetically, G. khanjanapajiae was more closely related to G. spinulosa from Taiwan than other Thai and Indian Ocean species. This present study highlights the continuing discovery of Gracilaria diversity and distribution in the tropical Indo-Pacific.

<div class="page" title="Page 1"><div class="layoutArea"><div class="column"><p><strong>The genus <em>Phyllophorella</em> (Phyllophoraceae, Rhodophyta) on the central coast of Peru, range extensions and anatomical description of the female gametophyte and carposporophyte</strong></p></div></div></div>

Phyllophorella was recently described from two localities on the central coast of Peru (12°S), based on the endemic species Phyllophora (Ph.) peruviana. The genus currently accommodates three species, Phyllophorella (P.) peruviana, P. humboldtiana and P. limaensis. Recent field surveys for Phyllophorella on the central coast of Peru led to the discovery of collections outside the originally reported ranges. Morphological, anatomical, and genetic characterization of the specimens confirms range extensions for P. peruviana to 9° S and 15° S, and P. humboldtiana to 12° S and 15° S. A combined phylogenetic analysis of rbcL and COI-5P gene sequences supports the taxonomic status of these two species and reasserts the genus as monophyletic. Anatomically, the two species differ in nemathecial structure. Phyllophorella peruviana displays dome-shaped and well-defined circular nemathecia, whereas in P. humboldtiana they are irregular and diffuse in form. Mature cystocarps were observed for the first time in Phyllophorella, in P. humboldtiana from Lima and Ica, Peru. Phyllophorella, as well as the other genera classified to the family Phyllophoraceae, have a procarpic sexual system, with a carpogonial branch of three cells; the cystocarp develops a thickened cortex, is immersed in the medulla, and lacks a pericarp and an ostiole. This study demonstrates that field work, together with morphological, developmental, and genetic analyses, are useful methods for improving our understanding of seaweed distributions and systematics.

Gracilaria phuquocensis sp. nov., a new flattened Gracilaria species (Gracilariales, Rhodophyta), previously recognized as G. mammillaris, from the southern coast of Vietnam

SUMMARYFlattened Gracilaria species are widely distributed along the coasts of the South China Sea with more than 20 species recorded. Within the South China Sea, Gracilaria mammillaris has only been reported from Vietnam, but this species is likely restricted to the western Atlantic. This study aimed to reevaluate the taxonomic status of Vietnamese specimens of ‘G. mammillaris’ using combined morphological and molecular data. Our data clearly indicated that Vietnamese specimens were morphologically and genetically distinct from authentic G. mammillaris from the western Atlantic, and also other described flat Gracilaria species. We, therefore, propose that specimens from Vietnam originally identified as G. mammillaris be designated as a new species, Gracilaria phuquocensis sp. nov. Morphologically, G. phuquocensis can be distinguished from other flat Gracilaria species by its small thallus size, narrower blades, many medullary layers, abundant basal nutritive filaments within mature cystocarps, and tetrasporangial nemathecium. Our rbcL sequence analyses showed that the new species was sister to Gracilaria rhodymenioides from Thailand, and these two species formed a clade with cylindrical Gracilaria species. Our study contributes to clarification of the taxonomic status of misidentified specimens attributed to the flattened Gracilaria species in the South China Sea.

Gracilaria suzannae sp. nov. (Gracilariales, Rhodophyta), a new flattened species from northeast Brazil based on morphological and molecular evidence

:A new species of Gracilaria, G. suzannae sp. nov., is described on the basis of detailed morphological, anatomical and molecular evidence from recent collections from intertidal reefs of northeastern Brazil. Diagnostic features of the new species include: tufted and tough thalli with subdichotomous, alternate to irregular branches; some branches incurved, with discrete marginal teeth, giving thalli a dentate to lacerate appearance in the upper parts; an abrupt transition of cell size between cortical and medullary regions; spermatangial conceptacles of the textorii type; and mature cystocarps with inconspicuous inner pericarp and few tubular nutritive filaments, particularly in basal portions. Universal plastid amplicon sequences of G. suzannae formed a distinct group within the genus Gracilaria, with intraspecific divergence of 0.24%. In the rbcL analysis, G. suzannae was recovered as sister to a well-supported clade containing G. occidentalis from the United States, with interspecific divergence of 1.3%. Unlike our specimens, the thallus habit of G. occidentalis is repeatedly forked, with smooth margins and rounded apices. Furthermore, G. suzannae was phylogenetically positioned close to a major clade composed of Indo-Pacific flat species with lobed, spiny or denticulate margins, all of which diverged 1.1 to 4.8% from G. suzannae. Gracilaria suzannae becomes the 16th flat species of Gracilaria reported for Brazil.

Polyamines in morphogenesis and development: a promising research area in seaweeds.

Polyamines in morphogenesis and development: a promising research area in seaweeds.

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).

Reproductive morphology of Gastroclonium pacificum (Champiaceae, Rhodymeniales) from Japan

SummaryMorphological studies were undertaken on Gastroclonium pacificum (E.Y. Dawson) C.F. Chang et B.M. Xia (Champiaceae, Rhodymeniales) from Japan. We describe the details of male reproductive structures, the procarp and early post‐fertilization stages. This species has a solid axis, with both tetrasporangia and polysporangia, spermatangia are cut off from spermatangial parent cells, and a procarp is composed of a 4‐celled carpogonial branch and two 2‐celled auxiliary cell branches. The mature cystocarp lacks a conspicuous ostiole, a characteristic of the genus Gastroclonium. The most distinctive characteristic of the species is the tela arachnoidea, which is lacking in other species of Gastroclonium.

Molecular systematics of the genus Actinotrichia (Galaxauraceae, Rhodophyta) from Taiwan, with a description of Actinotrichia taiwanica sp. nov.

Three species of Actinotrichia from Taiwan (Galaxauraceae, Rhodophyta) are described on the basis of morphological and molecular evidence, including A. fragilis, the generitype, A. robusta, a new record for Taiwan, and A. taiwanica sp. nov. Actinotrichia fragilis can be distinguished from the other two species by having a wider branching angle (usually > 40°), persistent and distinctly whorled assimilatory filaments and paraphyses issuing from the pericarp, which do not intermix with the gonimoblasts. Actinotrichia robusta can be distinguished from A. taiwanica by its narrower branches, thinner cortex, more obvious whorled assimilatory filaments and smaller fusion cell that is usually indistinguishable in the mature cystocarp. Recognition of these three species was also supported by rbcL sequence analysis. While A. fragilis is distributed in the pantropical regions of the Indian and Pacific oceans, A. robusta and A. taiwanica sp. nov. are only found along the Kuroshio Current in the northwestern Pacific Ocean.

The morphology of Ostiophyllum sonderopeltae gen. et sp. nov. (Gigartinaceae, Rhodophyta) from south-eastern Australia

Ostiophyllum sonderopeltae Kraft, gen. et sp. nov. (Gigartinaceae, Gigartinales) is an obligate epiphyte of Sonderopelta coriacea (Peyssonneliaceae, Gigartinales) in dimly illuminated, rough-water habitats at depths of 3–20 m in south-eastern Victoria and Tasmania. Plants consist of ovate to lobed, flattened blades < 3 cm in length and breadth that are shallowly anchored in the dorsal surface of the host. Distinguishing features of the genus are the ostiolate tetrasporangial sori that are invariably scattered across the broad faces of the fronds, and restriction of cystocarps to the blade edges, where they communicate with the surface via submarginal ostioles. Tetrasporangial development is unique in the family and begins when roughly circular patches of cortical filaments fail to keep pace with growth of the surrounding cortex, resulting in the formation of a cylindrical pit lined by the apical cells of cortical filaments. Filaments at the base of the pit, which now face towards the interior of the frond, then commence rapid apical growth and produce branched, inwardly directed tetrasporoblastic chains, each cell of which becomes a sporangial primordium. The chains aggregate densely within the lax medulla, forming a compact sorus of cruciate and decussate-cruciate tetrasporangia. Female gametophytes differ from tetrasporophytes in being less ovoid in outline, often broader than long, and usually more lobed. Procarps are typical for the family, and diploidized auxiliary cells issue filiform lateral and inwardly growing gonimoblasts that penetrate a lax weft of primary and secondary medullary filaments. Gonimoblasts then establish secondary pit-connections to the gametophytic cells and form consolidated pockets of spherical carposporangia between narrow islands of sterile cells and within an initially narrow hull of encircling filaments, there being no consolidated ‘Faserhülle’ around the mature cystocarp. Published studies of rbcL gene sequences by Hommersand and his colleagues [M.H. Hommersand, S. Fredericq, D.W. Freshwater & J. Hughey (l999) Phycological Research 47: 139–151] suggest that Ostiophyllum occupies an isolated and basal position within the Gigartinaceae, a conclusion reinforced by the anatomical features now reported.

CARRAGEENANS BIOSYNTHESIZED BY CARPOSPOROPHYTES OF RED SEAWEEDS GIGARTINA SKOTTSBERGII (GIGARTINACEAE) AND GYMNOGONGRUS TORULOSUS (PHYLLOPHORACEAE)1

Carrageenans biosynthesized by gametophytic and tetrasporic plants of seaweeds belonging to the Gigartinaceae and Phyllophoraceae are different: gametophytes produce carrageenans of the kappa family, whereas lambda‐carrageenans are extracted from tetrasporophytes. For Gigartina skottsbergii Setchell and Gardner and Gymnogongrus torulosus Hooker et Harvey, mature cystocarps were isolated and carrageenans were extracted. Structural determination by methylation analysis, Fourier transform infrared spectroscopy, and 13C‐NMR spectroscopy showed that they were kappa/iota‐carrageenans. For the extract obtained from cystocarps of Gigartina skottsbergii with water at room temperature, the ratio kappa:iota was 1:0.30 and at 90° C was 1:0.43; significant amounts of precursors were also present. The extract obtained from cystocarps of Gymnogongrus torulosus at 90° C showed prevalence of iota‐carrageenans (ratio kappa:iota 1:1.21). These extracts are similar to the polysaccharides produced by gametophytes of these seaweeds. For Gigartina skottsbergii, it was possible to separate the pericarpic tissue from the carposporophyte. Thus, they were extracted separately, and the carrageenans isolated were studied as described before, obtaining similar conclusions. These results clearly show that whereas the carposporophytes are located inside the cystocarp, they produce carrageenans of the kappa family despite of being diploid cells.

Morphology and reproduction of Bostrychia pinnata (Rhodomelaceae, Ceramiales) in laboratory culture

SUMMARY In unialgal culture, isolates of vegetative plants of Bostrychia pinnata often developed tetrasporangial stichidia and released viable tetraspores. Most tetra-sporelings developed normal branching before reproduction, however, some sporelings developed procarps, and later, spermatangia on juvenille unbranched stages ( 2 mm) were initially female before becoming bisexual when older and larger (> 5 mm). Unisexual male gametophytes were not seen in culture. Carposporophytes developed slowly (40–70 days) and were sometimes abortive or produced reduced numbers of carpo-sporangia (10–15 in cultures compared with 40–50 in field material). Carpospores germinated more slowly than tetraspores and the tetrasporophytes required up to 6 months to reach reproductive maturity. The Polysi-phonia-type life-history was completed in 9–12 months in the laboratory. Peripherohaptera were absent in cultured plants. The isolates from Florida, Guatemala and Peru did not reproduce sexually, but regularly underwent lower branch abscission as a means of vegetative reproduction. After several years in culture, most individual isolates became self-incompatible. In the female, 1 or 2 procarps formed on each axial segment and most were 4-celled with a few having 3 cells. A single branched sterile group of 3–7 cells was also present. After fertilization, the diploid nucleus in the carpogonium divided twice, isolating the capping element and trichogyne and establishing the connecting element adjacent to the auxiliary cell. In mature normal cystocarps the sterile group persisted and secreted mucilage into the central cavity. The mature pericarp was four layers thick (one layer of axial filaments and three cortical cell layers). Pseudocystocarps were common, produced no carpo-sporangia, contained elongate sterile cells, and were enclosed with a partially developed pericarp. Carpogonia in which 4 nuclei were usually seen may indicate developmental failure resulting in pseudocystocarps.

Reappraisal of the type species of Polysiphonia (Rhodomelaceae, Rhodophyta)

The genus Polysiphonia Greville, nom. cons., has had a long and confused nomenclatural history. At present, Polysiphonia has a wide circumscription, including at least 200 species, but it is heterogeneous in many vegetative and reproductive developmental features. Central to any re-evaluation of the genus is a detailed examination of the type species of Polysiphonia, P. urceolata (Lightfoot ex Dillwyn) Greville, which is conspecific with P. stricta (Dillwyn) Greville. We here report on the vegetative and reproductive morphology of P. stricta, including P. urceolata, based on type and other material from the British Isles. Thalli consist of prostrate and erect ecorticate axes with four pericentral cells, attached by unicellular rhizoids remaining in open connection with pericentral cells. Prostrate axes lack vegetative trichoblasts ; trichoblasts occur seasonally on erect axes. Branch initials are cut off from the subapical cell at intervals of four or five segments in dichotomous and alternating pairs rather than being formed from each axial cell in the spiral pattern typical of most species of Polysiphonia. Spermatangial branch initials, which are trichoblast homologues, are produced directly from each axial cell at the tips of erect branches, not subtended by trichoblasts, and have two- to five-celled sterile tips when mature. The mature carpogonial branch is four-celled with a two-celled first sterile group and a one-celled second sterile group. Following presumed fertilization, direct fusion apparently takes place between carpogonium and auxiliary cell; mature cystocarps are usually urceolate. Tetrasporangia are formed from the third pericentral cell, in straight series, and have two pre-sporangial cover cells. Previous accounts of a third, post-sporangial cover cell could not be substantiated. P. stricta and a small group of other Polysiphonia species differ in several important respects from most members of the genus, which have rhizoids cut off from pericentral cells by a cell division, abundant trichoblasts, spirally arranged tetrasporangia and a post-sporangial cover cell. The branching pattern of P. stricta highlights the difficulties of distinguishing between the tribes Polysiphonieae and Pterosiphonieae.

Vegetative and reproductive development of Laurencia venusta (Ceramiales, Rhodophyta)

The previously unknown vegetative and reproductive development of Laurencia venusta Yamada (Ceramiales, Rhodophyta) were studied based on specimens collected from Korea and Japan. Each vegetative axial segment bears a trichoblast and four pericentral cells; the first of the latter is always produced below the basal cell of the trichoblast; the second pericentral cell is formed at some distance from the first, followed by the third and fourth pericentral cells in an alternating sequence. Spermatangial branches are produced from one of two laterals on the suprabasal cell of a trichoblast in cup-shaped spermatangial pits. The procarp-bearing segment of the female trichoblast has five pericentral cells, of which the fifth becomes the supporting cell of the carpogonial branch. Mature cystocarps are ovoid with a non-protuberant ostiole. Tetrasporangia, with two pre- and one post-sporangial cover cells, are produced abaxially from the existing third and fourth pericentral cell, or occasionally only the fourth pericentral cell, and are parallel to the stichidial axis. Two pre-sporangial cover cells are aligned transversely to the stichidial axis in surface view. These features confirm the placement of L. venusta in the revised Laurencia Lamouroux. Laurencia venusta is characterized by a loosely intricate, small thallus without percurrent axis, numerous holdfasts from the creeping and coalesced basal branches, and abundant medullary lenticular thickenings. Furthermore, it seems to be distinct from other species in having a single, comparatively large (20–30 μm diam.) corps en cerise per epidermal cell.

Life History, Reproduction and Growth of Gracilaria domingensis (Gracilariales, Rhodophyta) from Brazil

The life history, reproduction and impact of fertilization on growth rate of Gracilaria domingensis (Kützing) Sonder ex Dickie were studied in vitro . The life history is of the Polysiphonia -type, and was completed in six months. Carpospores developed into plants which produced tetraspores in 60 days. The gametophytes originated from the released tetraspores became fertile after 101 days with a sex ratio of 1:1. Spermatangia were found in single deep conceptacles, verrucosa -type, as well as confluent ones, henriquesiana -type. Mature cystocarps have a conspicuous fusion cell and tubular nutritive cells formed from the gonimoblast to both pericarp and cystocarps floor. Non-fertilized female gametophytes showed a higher number of new apices during cultivation. Fertilized female branches grew similarly to the unfertilized branches during the first three weeks, but much slower from that time on. The reproductive cost, expressed as growth differential was around 55% smaller than the control.

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.

ECOTYPIC VARIATION IN PHYLLOPHORA PSEUDOCERANOIDES (RHODOPHYTA) ENSURES WINTER REPRODUCTION THROUGHOUT ITS GEOGRAPHIC RANGE1

ABSTRACTResponses to temperature and daylength were determined in laboratory culture for isolates of the red alga Phyllophora pseudoceranoides (Gmelin) Newroth et A.R.A. Taylor from Nova Scotia, Iceland, Roscoff (France), and Helgoland (Germany). All isolates grew from 3° to 25° C and survived from ‐2° or 0° C to 27° C but not 30° C. Reproductive requirements differed between life history phases and isolates. Isolates from Helgoland and Roscoff formed sporangial sori at 3°‐20° C, tetraspores at 3°‐12° C, and procarps at 10°‐20° C, irrespective of daylength. Spermatangia developed at 10°‐23° C but only in long days. As the other European isolates, the isolate from Iceland formed tetrasporangia at 3°‐12° C, but it had an additional requirement for short days. The Nova Scotian isolate formed sori at 10°‐20° C and sporulated at 10°‐18° C. When grown plants were transferred from noninductive to inductive conditions, sori were formed after 4 months and tetraspores developed and were shed (1‐)3 months later. Procarps formed 1(‐3) months after transfer.The phenology of P. pseudoceranoides was studied at Helgoland and Roscoff, where similar seasonal patterns were observed. Plants were perennial, forming new blades from October to June, which degenerated between August and February. In June, reproductive structures (sori, spermatangia, and procarps) started to appear on the new blades. From October to April, mature cystocarps were found. Mature tetrasporangia were observed only in February.The life history of P. pseudoceranoides is regulated by temperature and daylength. Differential effects on the different life history phases all serve to confine the production of spores (both carpospores and tetraspores) to the winter season. Differences in response between isolates from different geographic regions bring about the same effect: spores are shed only in winter.The nature of the geographic boundaries of P. pseudoceranoides is discussed.

Semnocarpagen. nov. (Rhodophyta: Rhodymeniales) from Southern and Western Australia

An examination of cystocarps from the rarely collected southern Australian alga currently known as Lomentaria corynephora (J. Agardh) Kylin has shown it to be a member of the Rhodymeniales but incorrectly placed in Lomentaria. As it is not referable to any of the genera presently ascribed to the order, the new genus Semnocarpa is proposed to accommodate its suite of unique features. Semnocarpa closely resembles Lomentaria in habit and in having basally septate branches, a peripheral network of widely separated medullary filaments around the cell-free (but mucilage-filled) centres of the main and lateral axes, gland cells directed inwardly on scattered medullary cells, and tetrasporangia produced laterally from surface cortical cells that line deep cavities in the branch surfaces. Features of the mature cystocarp, however, strongly differentiate Semnocarpa from Lomentaria. The carposporophyte has a fusion cell in which outlines of the component cells remain discernible, as opposed to having a fully consolidated fusion cell, and is laxly enclosed in a system of filaments derived from surrounding inner cortical cells. The cystocarp is entirely submerged within the bearing branch, there being no protuberant pericarp derived from the outer cortex of the sort previously thought to be a uniform feature of the family Lomentariaceae and virtually all Rhodymeniales. These features suggest that Semnocarpa is likely to be a highly derived member of the Lomentariaceae. A second species is newly described from material collected in Western Australia. Semnocarpa minuta sp. nov. differs from S. corynephora in its exclusively epiphytic habit, two-layered medulla, smaller stature and extensive crustose holdfast.

Life history and morphology ofChondrus nipponicus(Gigartinales, Rhodophyta) from Japan

The vegetative and reproductive morphology of Chondrus nipponicus from Japan is described. This species is dichotomously or irregularly branched with marginal and surface proliferations. Plants are dioecious; spermatangia develop singly or in pairs from outer cortical cells; the carpogonial branches are three-celled and borne on a large supporting cell. An enveloping tissue is absent in the mature cystocarp. Tetrasporangia are transformed from intercalary or terminal branches produced secondarily from medullary cells. In culture, tetraspores from plants collected in Oshoro Bay, Hokkaido, and Iwamuro, Niigita Prefecture, gave rise to dioecious male and female gametophytes, but only under short-day conditions at 15°C. In the presence of male plants, female plants formed carposporophytes that released carpospores, which germinated in turn to form tetrasporangial plants under both long- and short-day conditions at 15°C. The species thus has a Polysiphonia-type life history. Gametangial formation is under shor...

Reproductive development and classification of the red algal genus Ceratodictyon (Rhodymeniales, Rhodophyta)

Abstract Ceratodictyon spongiosum Zanardini (Rhodymeniales, Rhodophyta) is a widely distributed tropical Indo-Pacific species, the thalli consisting of a reticulate network of algal axes surrounded and covered by a sponge symbiont. Several important reproductive features of the algal partner are described in detail for the first time. Procarp organization, early gonimoblast and fusion cell development, mature cystocarp structure, and cruciately divided tetrasporangia, as well as the occasional presence of vesicular (‘gland’) cells on medullary filaments, relate the alga to the family Rhodymeniaceae of the order Rhodymeniales, rather than to the Gracilariaceae or the Gigartinales as has been previously considered. It is argued that Ceratodictyon and the non-sponge-associated Gelidiopsis are closely related genera that should be maintained as distinct taxa, rather than combined into the single genus Ceratodictyon as has been advocated recently.