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.     

Studies on freshwater red algae of Malaysia III. development of carposporophytes ofBatrachospermum cayennense Montagne,B. beraense Kumano andB. hypogynum Kumano et Ratnasabapathy

The development of the carposporophytes ofBatrachospermum cayennense, B. beraense andB. hypogynum is observed. The carpogonium bearing branch ofB. cayennense is very long and its cells are differentiated from those of the vegetative fascicles in size and shape. The trichogyne nucleus ofB. cayennense andB. beraense is not recognized. In the above two species it is observed that after contact with the trichogyne the nucleus of the spermatium divides into two daughter nuclei, one of which fuses with the female nucleus, while the other remains in the trichogyne. InB. beraense the fertilized carpogonium is divided transversely and the gonimoblast filaments are produced from the divided carpogonium. The protoplasmic connection between the carpogonium and the hypogynous nutritive cell is especially pronounced inB. hypogynum. Carpospores ofB. hypogynum germinate within the carposporangia and young germlings often throw away original carpospores, hence these young germlings look like gemmae.     

OBSERVATIONS ON THE DEVELOPMENT OF THE CARPOSPOROPHYTE OF SCINAIA PSEUDOJAPONICA YAMADA ET TANAKA (NEMALIALES,CHAETANGIACEAE)1

The development of the carposporophyte of Scinaia pseudojaponica Yamada et Tanaka is described for the first time. The carpogonial branch is 3-celled. Before fertilization the hypogynous cell divides into a group of 4 cells. Concurrently the cell beneath the hypogynous cells also produces initials which, following fertilization, develop into branched filaments that envelop the carposporophyte. After fertilization the gonimoblast initial is produced laterally from the basal part of the carpogonium. Carposporangia are produced in chains from the free ends of the gonimoblast filaments which grow toward the surface of the thyllus. A very thick pericarp surrounds the mature carposporophyte.     

THE DEVELOPMENT AND REPRODUCTIVE MORPHOLOGY OF HALOSACCION AMERICANUM I. K. LEE (RHODOPHYTA,PALMARIALES)1

Halosaccion americanum, a member of Palmariaceae, was grown in culture from spores and the life history was critically examined by the use of scanning EM and light microscopy. A mature tetrasporangium of H. americanum produces four spores that germinate to form two male and two female gametophytes. The male gametophytes grow to maturity in approximately eight months and macroscopically resemble the tetrasporophyte. Following the first division of the tetraspore, the two-celled female gametophyte consists of a vegetative cell and a carpogonium with trichogynes. Fertilization is accomplished by spermatia from male plants of the preceding generation, as male plants of the same season are immature. Spermatia are formed in a continuous layer over the surface of the mature male gametophytes and, when released, are entrained in long strands of mucous. Spermatia adhere to and fuse with trichogynes and, nuclear fusions presumably follow. The carposporophyte is absent; the new tetrasporophyte develops directly from the fertilized carpogonium. Growth of the sporophyte eventually obliterates the female gametophyte, and development into a mature tetrasporophyte proceeds over a period of approximately eight months. The development of H. americanum, with its extremely abbreviated female gametophyte stage and direct development of the tetrasporophyte from the zygote, indicates that this rhodophyte has the same life history as reported for other members of the Palmariales.     

鹧鸪菜生殖器官发育的研究

鹧鸪菜[Caloglossa leprieurii(Mont)J.Ag.]细胞含多核。在生殖季节,孢子体、雌、雄配子体在外形上有明显的差异:四分孢子体大而平展,分枝的上部肉眼可见有红色小斑点,即为四分孢子囊群。雌配子体顶部略蜷曲,分枝密,囊果呈球状,多位于分枝上部分枝点的腹面。雄配子体个体较小,枝顶蜷曲,颜色淡,特别生有精子囊的部分更淡。每种藻体的营养细胞的纹孔连结非常发达,每个细胞都具有4-5条,多者达7-8条。果胞枝由四个细胞组成,一般由围轴细胞分裂形成,果胞受精后,由支持细胞分裂形成辅助细胞,一个生育小枝上,可以连续形成5-7个甚至10个以上幼果胞系,但多数仅有一个果胞受精发育成囊果。当一个果胞受精时,其他果胞系就停止发育。精于囊位于分枝上部中肋的两侧,背腹面均有分布。一个营养细胞沿着叶面平行方向平周分裂成三个细胞,在两个外侧细胞各形成3-4个精子囊母细胞,每个精子囊母细胞斜壁分裂产生2-4个精子囊,放散后,余下的精子囊母细胞仍留在中间盘状细胞上。     

Studies on the Development of the Reproductive Organs of Caloglossa leprieurii (Mont.) J. Ag.

The cell of Caloglossa leprieurli is a polycaryon. The sexual thalli are usually dioecious. Its life cycle involves the alternation of three generations. In the reproductive season, the appearance of tetrasporophyte and female and male gametophyte shows evident difference. The tetrasporophyte is big and flat. The branches are sparse. Many small red spots, i.e. tetrasporogial groups, can be seen with the naked eyes in the upper part of the branch. The terminal part of the female gametophyte is a little twisted with thick branches. The cystocarps are spherical and most of them are located in ventral side of the upper branch points. The male gametophyte is smaller with less branches. Its terminal part is a little twisted with pale colour. The pit connections of the vegetative cells of every thallus are all well developed. The carpogonial branch consists of four cells. Generally, it is formed by the division of the pericentral cell. After fertilization of the carpogonium, an auxiliary cell is formed by the division of supporting cell. Usually five to seven, even more than ten young procarps can be formed at the apical part of the reproductive branch. The procarps often occur on consecutive segments of pericentral ceils. But among most of them only a carpogonium is fertilized and developes into cystocarp. When a carpogonium is fertilized, the other one on this branch usually cease further development. The spermatangia are formed on the lateral wing cells of both sides of the upper part midrib of a reproductive branch and distributed on both dorsal and ventral surfaces. A vegetative cell is divided into three cells in parallel to the surface of the thallus. The cortical cells under the two outer surfaces forms three to four permatangial mother cells. Each spermatangial mother cell divides into two to four spermatangia. After the sperm dispersal of the mature spermatangia, the spermatangial mother cells are still retained on both sides of the middle discoid cells.     

LEACHIELLA PACIFICA,GEN. ET SP. NOV., A NEW PARASITIC RED ALGA FROM WASHINGTON AND CALIFORNIA

Leachiella pacifica, gen. et sp. nov., a marine alloparasitic red alga is described from Washington and California. Several species of Polysiphonia and Pterosiphonia are hosts for this parasite. The thallus is a white, multiaxial, unbranched pustule with rhizoidal filaments that ramify between host cells, forming numerous secondary pit connections with host cells. All reproductive structures develop from outer cortical cells. Tetrasporocytes, situated on stalk cells, undergo simultaneous, tetrahedral cleavage to form tetraspores. Spermatia are formed continuously by oblique cleavages of the elongate spermatial generating cells. This results in spermatial clusters consisting of 4–8 spermatia in an alternate arrangement. Carposporophyte development is procarpial. The carpogonium is part of a six-celled branch including a sterile cell that is formed by the basal cell. The carpogonial branch is attached laterally to an obovate supporting cell that also forms an auxiliary cell, presumably formed prior to fertilization. After fertilization the carpogonium temporarily fuses with the auxiliary cell apparently to transfer the diploid nucleus and initiate further fusion with the subtending supporting cell to form an incipient fusion cell. The auxiliary cell portion of this fusion cell divides to form gonimoblast initials that continue to divide, forming gonimoblast filaments whose terminal cells differentiate into carpospores. The remainder of the fusion cell enlarges by continual fusion with adjacent vegetative cells. The resultant carposporophyte consists of a basal, multinucleate fusion cell supporting a hemispherical cluster of gonimoblast filaments with terminally borne carpospores. Vegetatively, Leachiella resembles several other parasitic red algae but it is clearly separated by the procarp, carposporophyte development and structure, and tetrasporocyte cleavage.     

Temporal variations of vegetative features, sex ratios and reproductive phenology in a Dictyota dichotoma (Dictyotales, Phaeophyceae) population of Argentina

This paper addresses the phenology of a Dictyota dichotoma population from the North Patagonian coasts of Argentina. The morphology of the individuals was characterized, and analyses of the temporal variations of vegetative features, diploid and haploid life cycle generations and sex ratios are provided. Individuals, represented by growing sporophytes and gametophytes, occurred simultaneously throughout the year. Morphological variables showed temporal variation, except the width and height of medullary cells, which did not vary between seasons. All vegetative variables were significantly correlated with daylength. Besides, frond length, frond dry mass and apical and basal branching angles were significantly correlated with seawater temperatures. Vegetative thalli were less abundant than haploid and diploid thalli. Sporophytes were less abundant than male and female gametophytes. Male gametophytes dominated in May, August, October and January, and female gametophytes were more abundant in September, November, December, February and March. The formation of female gametangia showed a significant correlation with daylength, and the highest number of gametangia was registered in spring. In general, the male/female sex ratio varied between 1:2 and 1:1. Apical regions were more fertile than basal regions. Our data about frequency in the formation of reproductive structures and male/female ratios are the first recorded in the Dictyota genus and thus could not be compared with populations from other regions of the world. Significant morphological variation was observed in thalli of both life cycle generations, regarding length and dry mass, number of primary branches and branching basal angle. In general, all variables analyzed varied seasonally except cortical cell width.     

OBSERVATIONS ON THE LIFE HISTORY OF PAPENFUSSIELLA CALLITRICHA (PHAEOPHYCEAE,CHORDARIALES) IN CULTURE1

Papenfussiella callitricha (Rosenv.) Kylin from eastern Canada was studied in culture. Zoids from unilocular sporangia develop into microscopic, filamentous, dioecious gametophytes which produce isogametes in filament cells and few-chambered plurilocular gametangia. Unfused gametes germinate to reproduce the gametophytes. Fusion takes place between a settled (“female”) and a motile (“male”) gamete. The zygote gives rise to a filamentous plethysmothallus that reproduces asexually by zoids formed in thallus cells and in few-chambered plurilocular zoidangia. Erect macrothalli are produced on the plethysmothallus, beginning with the formation of upright filaments. Later on, these filaments become the terminal assimilators of the macrothalli. Further assimilatory filaments, rhizoids, and unilocular sporangia are produced in a branching region at the base of the terminal assimilator. Zoids from unilocular sporangia formed in culture germinate to reestablish the gametophyte phase. Chromosome counts yielded n = 19 ± 3 for the gametophytes, and 32 ± 6 for the sporophyte, both plethysmothallus and macrothallus.     

Morphology and molecular relationships of Leptofauchea rhodymenioides (Rhodymeniales,Rhodophyta), a new record for Japan

Leptofauchea rhodymenioides Taylor (Faucheaceae, Rhodymeniales) is reported from Japan for the first time, based on detailed morphological studies and molecular phylogenetic analyses of nuclear‐encoded small subunit ribosomal RNA (SSU rRNA) and plastid‐encoded rbcL gene sequences. This is the first report of male gametophytes and detailed carposporophyte development in the genus Leptofauchea. This species is characterized as follows: (i) flat, membranous, and regularly and dichotomously branched thalli; (ii) the older blades are constricted below the apices; (iii) the cortex is composed of a continuous layer with an irregularly arranged outer layer, and the medulla of two to three incomplete layers; (iv) gametophytes are dioecious; (v) in males, the cortical cells cut off two to three spermatangial mother cells, which produce terminal spermatangia; (vi) in females, the procarp is composed of a three‐celled carpogonial branch and a two‐celled auxiliary cell branch; (vii) upon fertilization, the carpogonium directly contacts the auxiliary cell; (viii) the auxiliary mother cell fuses with vegetative cells, and forms a large trunk‐like fusion cell; (ix) gonimoblast filaments develop outwardly, and transform completely into carposporangia; (x) the carposporophyte is covered with a pericarp with a well‐defined tela arachnoidea; (xi) the mature cystocarp is spherical, has an ostiole, and protrudes from the blade margins; and (xii) the cruciately divided tetrasporangia are formed in nemathecia, produced laterally from paraphyses or terminally on short filaments. Molecular analyses suggest that Leptofauchea forms a strong sister alliance with the genus Webervanbossea. The families Faucheaceae and Lomentariaceae, and the genera Leptofauchea and Webervanbossea are monophyletic, but the latter two genera are not included in the Faucheaceae.     

Developmental morphology of Odonthalia floccosa (Ceramiales, Rhodophyta) in laboratory culture

Material of the red alga Odonthalia floccosa (Esper) Fal-kenberg (Rhodomelaceae, Ceramiales), collected from California, was cultured in the laboratory and its life-history was completed. Tetraspores grew into bipolar sporelings that differentiated into a colorless rhizoidal portion and a pigmented upright shoot. The sporelings became compressed apically and formed lateral branches in a regularly distichous manner that were congenitally fused with the main axis. These tetraspore germlings grew into diecious gametophytes. Male ga-metophytes produced numerous spermatangia on modified fertile branchlets (male trichoblasts) that possessed three to four monosiphonous, proximal segments. Female gametophytes formed a single pro-carp on the suprabasal segment of unbranched female trichoblasts. Cystocarps developed on the female gametophytes cocultured with male gametophytes and released viable carpospores that developed into fertile te-trasporophytes. Tetrasporangia were produced from the third and fourth periaxial cells in each of 12–45 successive fertile segments and provided three (two lateral and one basal) cover cells. The occurrence of both spermatangia and procarps on fertile trichoblasts in O. floccosa suggests that the alga is the most derived in these two characters among the species of the genus Odonthalia. This species is distributed in cold temperate regions in the North Pacific, and it should be excluded from the North Atlantic marine algal flora.     

GENETICS OF GRACILARIA TIKVAHIAE (RHODOPHYCEAE). X. STUDIES ON A BISEXUAL CLONE12

A male done of the red alga Gracilaria tikvahiae McLachlan spontaneously produced a bisexual frond which remained bisexual in subsequent subcultures. Both male and female components of bisexual fronds were functional; however, some unusual results were obtained in crosses. When bisexual fronds were crossed with a normal haploid male, the resulting carpospores all developed into diploid male gametophytes. When bisexual plants were self fertilized, all the carpospores yielded diploid bisexual gametophytes. Only when bisexual plants were crossed to normal haploid females, did carpospores develop into diploid tetrasporophytes as they normally do. The F₁ gametophyte generation obtained from these tetrasporophytes, however, included not only females and males but also bisexual plants, in a 2:1:1 ratio. These results are consistent with the interpretation that bisexual plants have a recessive mutation of a gene other than the primary sex determining locus, and that this mutation is expressed only in male plants. It is suggested that the altered gene may ordinarily have a regulatory function in the maintenance of the dioecious condition.     

LIFE HISTORY OF COLPOMENIA SINUOSA (SYCTOSIPHONACEAE,PHAEOPHYCEAE) IN THE AZORES1

Colpomenia sinuosa (Mertens ex Roth) Derbès and Solier (Scytosiphonaceae, Phaeophyceae) is a common species on the rocky intertidal shores of the Azores, where reproductive gametophytes occur throughout the year. Life‐history studies of this species were carried out in culture, and both sexual and asexual reproduction were observed. Anisogamous gametes fused to form zygotes. The zygotes gave rise to a filamentous prostrate sporophyte generation bearing unilocular sporangia, under both short‐day and long‐day conditions at 15 and 22°C, and to both unilocular and plurilocular sporangia, under the lower temperature condition. Unispores developed into gametophytes, and plurispores gave rise to filamentous sporophytes. Asexual reproduction was carried out by unfused female gametes and asexual plurispores produced from the same gametophyte. Unfused gametes developed into filamentous prostrate sporophytes producing unilocular sporangia in both culture conditions, and unispores released from the sporangia gave rise to gametophytes. Asexual plurispores from field gametophytes, under both culture conditions, developed directly into new gametophytes. The species exhibited three types of life history: a heteromorphic, diplohaplontic; a heteromorphic, monophasic (both with alternation between the erect and filamentous prostrate thalli); and a monomorphic, monophasic.     

CULTURE AND HYBRIDIZATION STUDIES ON PETROCELIS (RHODOPHYTA) FROM ALASKA AND CALIFORNIA1,2

Cultured tetraspores of Petrocelis middendorffii (Ruprecht) Kjellman from Amchitka Island, Alaska, gave rise to foliose, dioecious gametophytes similar to cultured gametophytes of P. franciscana Setchell & Gardner. A 1:1 ratio male:female gametophytes was obtained. Fertilized female plants produced cystocarps and carpospores that gave rise to crustose plants anatomically similar to field-collected Petro-celis sporophytes. Cultured male gametophytes of P. middendorffii were interfertile with cultured female blades of field-collected Gigartina pacifica Kjellman. Cultured P. middendorffii gametophytes from Amchitka were interfertile with cultured gametophytes of P. franciscana from 2 localities in California. Hybrid carpospores gave rise to crustose sporophytes that have not reproduced. Anatomical comparisons of P. middendorffii from Amchitka with P. franciscana from California showed no important differences in the characters originally used to separate these species. The interfertility of cultured Petrocelis gametophytes from california and Amchitka as well as the similarities of the history and anatomy suggests that a single species is involved. P. franciscana is reduced to a synonym of P. middendorfii.     

The life history ofAcrochaete wittrockii (Ulvellaceae,Chlorophyta)

Acrochaete wittrockii (Wille) Nielsen is a heteromorphic diplohaplont. The haplophase consists of isomorphic, dioecious filamentous epiphytes on brown algae. Several generations follow each other by triflagellate zoospores from spring to early summer. By late summer and throughout autumn, quadriflagellate zoopores are produced by the epiphytic thalli; they give rise to male and female gametophytes of a globular, pseudoparenchymatic appearance in culture. The gametophytes produce anisogamic biflagellate gametes which, after gametic union, develop into diploid unicellular sporophytes. After 6–7 days, the sporophyte produces triflagellate zoospores, repeating the life history when germinating on brown algal hosts. Alternatively, triflagellate zoospores which settle on the bottom of petri dishes, develop into unicellular, autonomous sporangial plants. Their triflagellate spores repeat the epiphytic stage on brown algal hosts, or the sporangial plant cycle on non-living substrate, respectively.     

Morphological variability in a red seaweed: confirmation of co-occurring f. lessonii and f. chauvinii in Chondracanthus chamissoi (Rhodophyta,Gigartinales)

Variability in thallus morphology is common in red seaweeds. Two co-occurring forms have been described for Chondracanthus chamissoi based mainly on blade width. To determine whether two distinct forms or a range of intermediate morphologies occur in C. chamissoi, thalli were collected from three localities in southern Chile in autumn–winter, repeating the sampling in one locality in spring and in summer. In each occasion, individual sporophytic and male and female gametophytic clumps were collected, and the longest blade with intact apex from each clump was evaluated. Blade length, width, density of spines, axis curvature and thickness, and pinnule length and width were evaluated in each blade. Principal components analyses separated two groups of thalli, one group with narrow, thick, and curved (concavo-convex) blades, with few spines consistent with f. lessonii, and another with broad, thin, and flat blades, with many spines consistent with f. chauvinii. These variables also had bimodal frequency distributions. Pinnule measurements were mainly associated with differences among sporophytes and gametophytes. Age (length), phase of the life cycle, and sex were not related to the forms. Furthermore, thalli of both forms were collected side by side in the study sites and throughout the year so the occurrence of the two forms was not attributable to local environmental conditions. In this species, secondary basal disks are produced after attachment of apexes to the substratum. These disks may produce blades with a modified morphology in a way similar to proliferations and regenerations described for Schottera nicaeensis.     

Amphithallia,a genus with four-celled carpogonial branches and connecting filaments in the Corallinales (Rhodophyta)

The South African marine alga Amphithallia crassiuscula, previously subsumed in the widely reported Synarthrophyton patena, is here re-described as a distinct species and genus. Thalli grow as obligate epiphytes on Gelidium capense in the upper sublittoral zone (while S. patena grows on Ballia callitricha). Gametophytes are monoecious with four-celled carpogonial branches and sterile cells are borne on supporting cells (dioecious or hermaphroditic with two or three-celled carpogonial branches and sterile cells borne on hypogynous cells in Synarthrophyton). Postfertilization stages involve a connecting filament linking the carpogonium to several putative auxiliary cells, demonstrating a non-procarpic condition with apparent absence of a fusion cell. Gonimoblast filaments develop at the level of basal cells of carpogonial branches. Spermatangial mother cells remain either unbranched (cutting off spermatangia only) or develop dendroid (branched) filaments with terminal spermatangia (as in Synarthrophyton). Multiporate conceptacles develop straight pore canals lined by non-differentiated cells (conical canals with differentiated pore cells along the base in Synarthrophyton). The here described pre- and post-fertilization characters are new for the order Corallinales motivating the establishment of the new genus Amphithallia.     

Karyology and sex determination in Aglaothamnion oosumiense Itono (Ceramiaceae,Rhodophyta)

A cytogenetic investigation on male and female reproductive cells of Aglaothamnion oosumiense Itono indicates that the sexuality of this species might be determined by a sex chromosome. Chromosome counts in female and male gametophytes gave 37 and 36, respectively. Sex ratio of gametophytes was 1:1. Both male-derived and female-derived bisexual plants were observed. Bisexual plants were different in gross morphology and position of carpogonial branches from normal unisexual gametophytes. The chromosome number of female-derived bisexual plants was N=37 and male-derived bisexual plants was N=36. Some male plants developed parasporangia in addition. The paraspore germlings showed the same chromosome number as the male plants. The fertilized carpogonium and gonimoblast cells had 2N = ca. 70 chromosomes.     

Reproductive structures of Dictyopteris undulata (Dictyotales, Phaeophyceae) from Japan

sporophytes, and both male and female gametophytes of Dictyopteris undulata Holmes were collected from the Pacific coast and the Japan Sea coast of Japan. Female gametophytes are reported for the first time in the present study. All reproductive structures are aggregated in sori that form on both sides of the midrib in the upper and the middle parts of a blade. Tetraspor-angia are spherical and project from the cortical layer with a 2–4-celled stalk at the base. They are sometimes divided tetrahedrally to form four spores, but often remain undivided. Oogoniat sori also project from the cortical layer. Each oogonium is ovoid, sometimes borne on a single stalk cell at the base. Antheridial sori appear swollen above the cortex and each antheridium has a basal stalk cell. Fertile female gametophytes and te-trasporophytes are difficult to distinguish from each other in surface view because tetrasporangial and oogonial sori are similar in size and undivided tetrasporangia resemble oogonia. Oogonia are not so closely packed in small groups, unlike in Dictyota species, and they can be distinguished by the cell sizes (i.e. tetrasporangia are bigger in diameter than oogonia).