MORPHOLOGY AND LIFE HISTORY OF SCYTOSIPHON LOMENTARIA (SCYTOSIPHONACEAE,PHAEOPHYCEAE) FROM THE AZORES1

Morphological and culture studies of Scytosiphon lomentaria (Lyngbye) Link and Microspongium gelatinosum Reinke (Scytosiphonaceae, Phaeophyceae) were undertaken on material collected on the Island of São Miguel, Azores, where both species were commonly found. Erect thalli of S. lomentaria collected in the field were up to 33 cm long and 2.3 mm wide, tubular, hollow, and commonly constricted at intervals. The plurilocular sporangia were positioned in continuous sori on the thallus surface. Ascocysts were present. In the field, M. gelatinosum formed crustose to slightly pulvinate plants, were spongy in texture, and dark brown to black in color, which were circular or irregularly spreading over several centimeters and firmly attached to the substratum. Sessile unilocular sporangia were located in sori on the crust surface. In culture S. lomentaria plurispores developed into Microspongium‐like crustose prostrate thalli that formed unilocular sporangia. Unispores developed into new erect thalli that formed plurilocular sporangia. Sexual reproduction was not observed. In culture, M. gelatinosum unispores developed into erect thalli identical with S. lomentaria. These results are similar to those reported for other areas and suggest the occurrence in the Azorean plants of a monophasic and heteromorphic life history, involving both entities studied.     

RELATION OF TEMPERATURE TO DEVELOPMENT OF THE MACROTHALLUS OF DESMOTRICHUM UNDULATUM1,2

Desmotrichum undulatum (J. Agardh) Reinke (Phaeophyta) was found in the winter months in the littoral zone of a tidal marsh in Virginia. When field collections were maintained in culture media at 21 C, most cells of the thallus developed into plurilocular sporangia. Released zoospores developed into microthalli from which clonal cultures were established. At 21 C microthalli produced sporangia which released zoospores, subsequently developing into more microthalli. However, microthalli at 6 C formed filaments which subsequently developed into thalloid plants. When the thalloid plants of Desmotrichum formed in culture were subjected to 21 C, plurilocular sporangia were formed. These results support the proposition that the seasonal periodicity of Desmotrichum is due to a temperature-regulated phenomenon in the development of macrothalli.     

Morphology and life history of Scytosiphon canaliculatus comb. nov. (Scytosiphonales,Phaeophyceae) from Japan*

Morphology of field material and life history in culture were studied in Scytosiphon canaliculatus (Setchell et Gardner) comb. nov. from northern Japan. Erect gametophytes of S. canaliculatus are cylindrical, tubular, up to 7 mm wide and 40 cm long, and without regular constrictions. S. canaliculatus has pronounced anisogamy and ascocysts accompanied with plurilocular gametangia. The life history of S. canaliculatus showed an alternation between erect gametophytes and crustose prostrate sporophytes bearing unilocular sporangia. Since field sporophytes of S. canaliculatus were found to be identical with Hapterophycus canaliculatus Setchell et Gardner (Ralfsiaceae, Phaeophyceae), it is proposed to transfer H. canaliculatus to the genus Scytosiphon. In the field, gametophytes with plurilocular gametangia appeared in spring and disappeared in summer. Sporophytes with unilocular sporangia were collected in late autumn and winter. Unilocular sporangia were produced at 15°C in short-day culture conditions and unispores developed into erect gametophytes at 5–15°C. It is suggested that the seasonal Occurrence of gametophytes in the field is due to the seasonal formation of unilocular sporangia, which is regulated by temperature and photoperiod.     

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 life history of Halopteris filicina (Sphacelariales, Phaeophyceae) from Korea

The vegetative morphology and life history of Halopteris filicina (Grateloup) Kutzing, collected from Korea, were examined in laboratory culture. Field plants attaining 3–5 cm in height were epilithic, tufted, yellowish-brown, and produced numerous erect axes with alternately distichous branches from compact basal discs. They were cultured under a 12:12 h LD photoperiod at 10°-C, 15°C and 20°C to observe the influence of temperature on reproduction. At 10°C plants grew only vegetatively, whereas at 15°C and 20°C they produced unilocular sporangia. Unispores released from sporangia developed into monoecious, anisogamous gametophytes that formed plurilocular female and male gametangia on the same lateral branches. The zygotes, by fusion of female macrogametes and male microgametes, developed into sporophytes bearing unilocular sporangia, whereas the unfused female gametes germinated parthenogenetically. This species was confirmed to have an isomorphic life history, basically similar to the other species of Sphacelariales.     

Life histories of Colpomenia sinuosa and Hydroclathrus clathratus (Scytosiphonaceae, Phaeophyceae) in culture

Life-history studies in culture were carried out on Colpomenia sinuosa (Mertens ex Roth) Derbès et Solier and Hydroclathrus clathratus (C. Agardh) Howe (Scytosiphonales, Phaeophyceae) from Japan. These species showed a heteromorphic life-history pattern with an alternation between erect thalli bearing plurilocular zoidangia and prostrate thalli bearing ectocarpoid plurilocular and unilocular zoidangia. Plurizoids released from erect and prostrate thalli developed into prostrate thalli. Unizoids, however, developed into erect thalli. Prostrate thalli produced plurilocular zoidangia in long-day conditions and unilocular zoidangia in short-day conditions at 10-20°C. Prostrate thalli of C. sinuosa formed ascocysts. Germlings of both species did not grow at 5°C.     

Life history of Chnoospora implexa (Chnoosporaceae, Phaeophyceae) in culture

The life history of the brown alga Chnoospora implexa J. Agardh (Chnoosporaceae, Scytosiphonales) from Japan was studied in laboratory cultures. This species showed a heteromorphic and diphasic life history, alternating between erect gametophytes and discoid sporophytes. The gametophytes were dioecious and produced isogametes. The zygotes developed into sporophytes at 20°C under long‐day conditions, which formed plurilocular zoidangia. Zoids released from the plurilocular zoidangia developed again into sporophytes that always formed plurilocular zoidangia at 20°C and 25°C in long‐day conditions, and mainly unilocular zoidangia at 25°C in short‐day conditions. Zoids released from unilocular zoidangia developed into dioecious gametophytes. At 15°C zygotic erect thalli were formed and were revealed to be diploid by microspectrofluorometric measurements of nuclear DNA contents. The development and reproduction of unfused gametes were similar to those of zygotes. Some strains showed a direct‐type life history; gametophytic thalli were produced, but not via a sporophytic phase.     

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.     

First record of Asteronema rhodochortonoides (Phaeophyceae) for the Pacific Ocean

Morphological observations of a minute, filamentous, branched brown alga epiphytic on Sargassum thun‐bergii (Mertens ex Roth) Kuntze were made on material collected at Tsuyazaki (33°48′N, 130°27′E), Fukuoka Prefecture, southern Japan. This alga was assignable to Asteronema rhodochortonoides (Børgesen) Möller et Parodi in having stellately arranged chloroplasts with several pyrenoids grouped in the center, predominantly apical growth, narrow filaments, and elliptical or broadly elliptical plurilocular zoidangia that are apically or laterally formed on upright filaments. A comparison of partial nuclear small subunit rDNA sequences between the Japanese material and A. rhodochortonoides from the Canary Islands showed only two or three nucleotide differences. This supports our assignment of the Japanese material to this species as a first report for the Pacific Ocean. In laboratory cultures, zoids released from plurilocular zoidangia developed into plants with morphology similar to the field‐collected plants. This cycle repeated without production of unilocular zoidangia in our cultures.     

Life history of Japanese Stypocaulon durum (Sphacelariales, Phaeophyceae)

Phenology, morphology, life history and responses to different temperature and photoperiod conditions were studied in Japanese Stypocaulon durum (Ruprecht) Okamura. Erect thalli of the species were collected year-round, but the mature thalli forming either uniloc-ular sporangia or two different types of plurilocular structures (evidently gametangia) on separate thalli were found only in winter. ln culture, an isomorphic life history is suggested for the species, alternating between a sporophyte forming unilocular sporangia and gam-etophytes forming plurilocular macro- (female) and micro- (male) gametangia. Contents of unilocular sporangia were not released, but germinated in situ, developing into erect thalli forming plurilocular gametangia. Macrogametangia released aplanogametes (oospores), but male gametangia appeared to be non-functional, although flagellated cells were once formed in the loc-uli. This is the first report of plurilocular gametangia in the species. Although the species grew well and matured under considerably lower temperature conditions than European Stypocaulon scoparium (L.) Sauvageau, its temperature requirements showed similarity to northwestern Atlantic Stypocaulon species. This supports the notion that northwestern Atlantic Stypocaulon is conspecific with S. durum.     

FACTORS DETERMINING VARIOUS FORMS IN CLADOSIPHON ZOSTERAE (PHAEOPHYCEAE)

The brown alga Cladosiphon zosterae (J. Ag.) Kylin (Chordariaceae) is found to exist in culture in a variety of forms, including filaments, discoid or crustose forms, and two types of erect cylindrical thalli. Asexual spores from plurilocular sporangia of each form can produce any and all forms. Three factors controlling morphological expression in C. zosterae have been identified. These factors include: (1) heteroblasty (formation of filamentous and discoid germlings as a consequence of alternate modes of spore germination), which was independent of all environmental factors tested including temperature, photoperiod, nitrogen source, and general fertility of the growth medium; (2) influence of certain nitrogen sources, notably ammonium, which induce a compact discoid or crustose form; and (3) a morphogenetic factor presumed to be bacterial which determines mode of development and subsequent morphology of the erect Cladosiphon thallus.     

The life histories in culture of the brown algae Gononema alariae sp.nov. and G. aecidioides comb.nov. from Greenland

Plants that agree with those provisionally referred to as Entonema alariae Jaasund (nom.prov.) have a direct type of life history. The swarmers from the plurilocular sporangia germinate and develop directly into new, small tufts. This development takes place under cold (4°C) as well as under warm (15°C) long day (LD) conditions in a medium with liver infusion. Erect, branched, uniseriate filaments develop in a medium without liver infusion. The laterals of these filaments are transformed to uniseriate, plurilocular sporangia under cold LD conditions. A lateral true hair has been observed on the erect filaments. Such filaments resemble those of the genus Gononema and the plant in question is, therefore, named Gononema alariae sp.nov. Ectocarpus aecidioides Rosenvinge = Entonema aecidioides (Rosenvinge) Kylin also has a direct type of life history. In a medium without liver infusion it occasionally develops erect filaments. These filaments also resemble those of the genus Gononema and the combination Gononema aecidioides (Rosenvinge) comb.nov. is, therefore, proposed.     

The life history of Ahnfeltiopsis paradoxa (Gigartinales, Rhodophyta) in laboratory culture

The life history of the red alga Ahnfeltiopsis paradoxa (Suringar) Masuda (Phyllophoraceae, Gigartinales) from Japan was completed in laboratory culture. Carpospores isolated from field-collected plants germinated to form circular crusts that were composed of a monostromatic hypothallium consisting of radiating filaments, a polystromatic perithallium consisting of tightly coalescent erect filaments, and hypobasal tissue derived from the hypothallium. The crusts were induced to sporulate by transferring them from short-day to long-day regimes at 15° and 2°C. Each crust produced several nemathecia along 1-4 concentric rings. Intercalary, cruciately or decussately divided tetrasporangia were formed in 4-6 (1-2 at the margin of the nemathecium) successive cells of a single filament of the nemathecia. Tetraspore germlings gave rise to basal discs from which upright axes developed. The upright axes first grew without branches or were sparsely branched and later bore many marginal reproductive proliferations. Procarps and spermatangia were formed in the proliferations on different individuals. Carposporophytes developed on female plants that were co-cultured with male plants. Gonimoblast filaments were formed from an auxiliary cell that fused with a carpogonium. Carposporangia developed from gonimoblast filaments and medullary cells contacted by the gonimoblast filaments. Carpospores were discharged through carpostomes formed in the thickened cortex. Tetraspores were cultured from field-collected crusts of a morphology similar to that of cultured tetrasporophytes. They gave rise to upright gametophytic axes similar in morphology to this species as seen in the field.     

A Virus Infection in the Marine Brown Alga Ectocarpus siliculosus (Phaeophyceae)

Laboratory cultures of Ectocarpus siliculosus originating from New Zealand showed a defect in gametangium formation. Nuclear divisions in gametangium initials are not followed by cell wall formation. In the resulting multinucleate cells nuclear DNA increases dramatically, and nuclear membranes disintegrate. Eventually, the entire structure is filled with hexagonal particles of approximately 130 nm diameter. These were isolated and shown by EM to consist of a dense core surrounded by a 3-layered shell. They are released into the culture medium when the host cells burst. Ectocarpus gametes from healthy cultures could be infected by these particles. The resulting partheno-sporophytes developed pathological symptoms, suggesting that the particles are viruses. The expression of the defect is temperature dependent. At 10°C all gametangia are abnormal, while between 15 and 20 °C defective and normal gametangia and gametes are formed on the same plant. Partheno-sporophytes developing from such gametes carry the viral particles expressed in deformed unilocular and plurilocular sporangia.     

Life history and systematic position of the rare brown alga Climacosorus mediterraneus

Cultures of Climacosorus mediterraneus were established with material from Spitsbergen. This species has previously been reported from three widely separated geographic areas: the west Mediterranean, north-west France, and north Norway. Although adapted to temperatures near 0°C, the northern isolate grew well at 15°C which approximates the summer temperature of the southern habitats. The life history proved to be entirely asexual with successive generations bearing unilocular sporangia on the erect filaments and plurilocular sporangia infrequently on the prostrate system. Swarmers of the two reproductive organs gave rise to similar progeny. Chromosome counts revealed equal numbers in somatic cells and unilocular sporangia which substantiates the development observed. The absence of true hairs and the few longitudinal divisions, which only occur in connection with formation of unilocular sporangia and branches, suggest that C. mediterraneus should be assigned to the Pilayellaceae.     

浒苔(Enteromorpha prolifera)藻体发育的显微观察

通过显微镜观察以及石蜡切片法观察了浒苔属浒苔藻体的发育过程,阐述了浒苔从孢子释放到形成成熟藻体这一发育过程的显微特征。结果表明:浒苔孢子由成熟体细胞分化发育而成,每个成熟体细胞可形成10～30个孢子;孢子首先分裂为2细胞结构,2细胞具有明显的极性,基细胞发育成为假根,顶端细胞不断进行横分裂形成丝状体;丝状体顶端以下细胞通过纵分裂形成管状叶状体,顶端细胞始终保持横分裂;纵分裂分为切向分裂与径向分裂,切向分裂增加管状叶状体管周细胞数从而使管体增大,径向分裂形成管外壁突起细胞,最终发育为分枝;管状叶状体管腔内部有绒毛状的突起及糖蛋白成分的网架结构;当管状叶状体管周细胞达到30～50h,管腔内部突起消失,网架结构收缩拉紧,管壁细胞贴近形成片状叶状体;整个浒苔藻体始终保持极性发育。     

A taxonomic study of Japanese Scytosiphon (Scytosiphonales, Phaeophyceae), including two new species

Morphological and culture studies were carried out on the genus Scytosiphon (Scytosiphonales, Phaeophyceae) growing in Japan. Morphologies of plurilocular zo-idangia and sporophytic thalli were found to be useful as taxonomic characters. Two types of plurilocular zo-idangial sori were recognized: (i) loosely coherent plurilocular zoidangia without a cuticular layer (loose type); (ii) tightly coherent plurilocular zoidangia with a cuticular layer (coherent type). The sporophytic thallus morphology was different among species in general appearance (tufted or discoid), degree of cohesion of erect filaments, and presence or absence of paraphyses. Two new species are described, Scytosiphon gracilis sp. nov. and Scytosiphon tenellus sp. nov, Scytosiphon gracilis is distinguished from other species by a thin medullary layer, coherent plurilocular zoidangia, no ascocysts associated with plurilocular zoidangia, and Compsonema-like sporophytic thalli. Scytosiphon tenellus is characterized by a thin medullary layer, coherent plurilocular zoidangia, ascocysts among plurilocular zoidangial sori, and Stragularia-like sporophytic thalli. Scytosiphon lo-mentaria (Lyngbye) Link is characterized by a constricted gametophytic thallus, loose plurilocular zoidangia, the presence of ascocysts, and sporophytic thaili identified with Microspongium gelatlnosum Reinke.     

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

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 (< 1 mm). Most normally branched gametophytes (> 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.     

CULTURE STUDIES ON REPRODUCTION OF SPERMATOCHNUS PARADOXUS (PHAEOPHYCEAE,CHORDARIALES)1

The life history of Spermatochnus paradoxus (Roth) Kütz. isolated from the Mediterranean Sea was studied in culture. Meiospores develop to a microscopic stage (microthallus) which at 20°C perpetuates asexually by plurilocular sporangia and formation of new microthalli. At 9°C microthalli act as homothallic gametophytes. Fusion of isogametes results in a diploid microthallus which, after differentiation of an apical cell, leads back to Spermatochnus plants. In addition, gametes develop without fusion to form haploid macrothalli, the further fate of which has not been determined. Chromosome numbers alternate between n = 20 ± 2 in the microthalli and 2n = 41 ± 4 in macrothalli.     

Laminarionema elsbetiae gen. et sp. nov. (Ectocarpales, Phaeophyceae), a new endophyte in Laminaria sporophytes

Laminarionema elsbetiae gen. et sp, nov, (Ectocarpaceae, Ectocarpales. Phaeophyceae), a new endophyte of Laminaria japonica Areschoug (Laminariales, Phaeophyceae), is described from Muroran. Hokkaido, Japan. Laminarionema elsbetiae grows in the host tissues forming networks in the epidermal and subcortical layers as well as penetrating into the cortical and medullary layers. Only phaeophycean hairs emerge from the surface of the host tissue. No reproductive cells were found in field material. However, under host-free culture the species formed three morphologically different reproductive structures. Macrosporangia containing a single large motile spore were formed under long and short day conditions below 20°C, transformed from vegetative cells, conical to elongated in shape, 50–75 μm in length and ca. 10 μm in diameter. Microsporangia were linear to lanceolate, sometimes branched, formed under long and short day conditions below 15°C. Unilocular sporangia were more or less irregular in shape, formed under short day conditions of 5–15°C, 60–75 μm in length and 40–45 μm in diameter. Sexual fusion between macro- and microspores was not seen. In mixed cultures of L. elsbetiae with young sporophytes of L Japonica Areschoug as well as Saccorhiza dermatodea (de la Pylaie) J. Agardh, L elsbetiae infected both hosts, grew in the same manner as in natural hosts, and formed macrosporangia between host epidermal cells.