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.     

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.     

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 AND SYSTEMATIC POSITION OF AKKESIPHYCUS LUBRICUS (PHAEOPHYCEAE)1

The life history in culture of Akkesiphycus lubricus Yamada et Tanaka, an alga which has been placed in the Coilodesmaceae or the Punclariaceae, Dictysiphonales, was studied. In culture the species alternates between a microscopic filamentous gametophyte and a macroscopic polystichous sporophyte, a pattern common to the Dictyasiphonales and Laminariales. However, it has a unique anisogamous dioecious gametophyte. Fusions between mac-ro-gametes and micro-gametes were not observed, Macro-gametes or zygotes germinated, mostly developing into sporophytes that formed unilocular sporangia and the rest developed into reduced gametophytic flaments again. The gametophyte matures in 50C short-day conditions, corresponding to winter in Hokkaido. The sporophyte develops normally and matures only in low-temperature conditions irrespective of daylength. In regard to iits systematic position, Akkesiphycus lubricus is considered to have a closer relationship with the Laminariales than with the Dietyosiphonales in the following characters; lack of pyrenoids; early stages of parenchyma formation in the sporophyte; direct development of sporophytes from gametes or zygotes without forming a besal system zoospore becomes almost empty after germination by the migration of cell contents into a germ lube; formation of macro-gametangia by direct conversions of mother cells of mother cells of fertile branches; and micro-gametangia formed in clusters showing closeresemblance to the antheridia of Pseudochorda nagii (Tokida) Inagaki.     

MORPHOLOGY,LIFE HISTORY,AND MOLECULAR PHYLOGENY OF STSCHAPOVIA FLAGELLARIS (TILOPTERIDALES,PHAEOPHYCEAE) AND THE ERECTION OF THE STSCHAPOVIACEAE FAM. NOV.1

The phenology, life history, ultrastructure of reproductive structures, and molecular phylogeny using rbcL and rDNA (5.8S, internal transcribed spacer 2, and partial 26S) gene sequences of Stschapovia flagellaris, endemic to the northwestern Pacific Ocean, were studied. This species was first classified in the order Delamareales together with Delamarea, Coelocladia, and Cladothele. Those three genera, however, were later transferred to Dictyosiphonales, whereas the systematic position of Stschapovia remained unclear. At Abashiri, Hokkaido, Japan, the species regenerated by forming a new erect thallus from a perennial crustose holdfast or by presumably parthenogenetic development of eggs released from the erect thallus. There was no alternation of generations. In winter, the monoecious erect thallus formed reproductive structures (i.e. plurilocular antheridia and oogonia) in the thickened part of the thallus. Sperm had a chloroplast with an eyespot and a long anterior and short posterior flagellum. Eggs contained numerous disc‐shaped chloroplasts, physodes, and vacuoles. Neither sexual attraction of the presumptive sperm by eggs nor their sexual fusion was observed. Molecular phylogenetic analyses revealed the closest phylogenetic relationship between Stschapovia and Halosiphonaceae, and they grouped with Phyllariaceae and Tilopteridaceae (Tilopteridales s. s.). Stschapovia and Tilopteridaceae have several important morphological similarities: chloroplasts lacking pyrenoids, lack of sexual reproduction despite the release of obvious sperm, occurrence of monoecious gametophytes, and similarity in the early developmental pattern of the erect thallus. In conclusion, we propose the establishment of the new family Stschapoviaceae to accommodate Stschapovia and the placement of the family in the order Tilopteridales together with Tilopteridaceae, Halosiphonaceae, and Phyllariaceae.     

LIFE HISTORY AND SYSTEMATIC POSITION OF PSEUDOCHORDA GRACILIS SP. NOV. (LAMINARIALES,PHAEOPHYCEAE)1

Pseudochorda gracilis sp. Nov. (Pseudochordacease, Laminariales) is described from the Japan Sea coast of Hokkaido/ the species is subtidal, epilithic and annual, appearing in spring and maturing in winter. Erect thalli grow solitary or in tufts on a small discoid holdfast. They are simple, cord-shaped and hollow, with inner hyphal filaments, cylindrical medullary cells and paraphyses consisting of 3–6 cells. Hair tufts are observed only in young thalli. Unilocular sporangia are sessile and narrowly ovate. In culture, P. gracilis shows a heteromorphic life history with oogamy, characteristic of the order Laminariales. Gametophytes are dioecious and dimorphic. Gametophytes mature under lower temperature conditions (usually below 10°C), and sporophytes mature under low temperature and short-day conditions (5°C, SD). The seasonal growth pattern of the species results from the photoperiod-temperature conditions controlling saprophyte maturation.     

CULTURE STUDIES ON THE LIFE HISTORY OF CHORDARIA LINEARIS (PHAEOPHYCEAE) FROM TIERRA DEL FUEGO,SOUTH AMERICA1

Studies of laboratory cultures of Chordaria linearis (Hooker et Harvey) Cotton from southernmost South America revealed that this species has an obligate sexual life history in which a macroscopic sporophyte alternates with a monoecious microscopic gametophyte. Sexual reproduction is isogamous and under photoperiodic control. Gametes are produced only in short days, whereas in long days, asexual zoospores are formed that recycle the gametophyte generation. Unfused gametes develop into gametophytes, and sporophytes originate only from zygotes. Unlike other sexual members of the Chordariales, gametes of C. linearis have a reduced stigma and do not show phototaxis. They are released at the beginning of the night, not in the morning. In nature, C. linearis seems to be regularly infected by a dictyosiphonalean epiphyte resembling the rare arctic species Trachynema groenlandicum (Lund) Pedersen. The epiphyte is responsible for previous contradictory results obtained in laboratory cultures of C. linearis. This is the first record of Trachynema in the southern hemisphere.     

GROWTH OF COLPOMENIA PEREGRINA (PHAEOPHYCEAE) IN CULTURE: EFFECTS OF SALINITY,TEMPERATURE AND DAYLENGTH1

Increases in size of Colpomenia peregrina (Sauv.) Hamel microthalli were determined at six different combinations of salinity and temperature under laboratory conditions. Microthalli grown at low salinity (15%) did not have a growth rate significantly different from microthalli grown at high salinity (30%). However, more macrothalli were produced in higher salinity media. Fewer macrothalli were produced at lower temperatures. Growth of C. peregrina microthalli was also determined at six different combinations of daylength and temperature. Microthalli under 15:9 h (LD cycle) did not have a growth rate significantly different from microthalli under 9:15 h LD. However, more macrothalli were produced under long day conditions. Of the three different temperatures utilized (5, 13 and 20° C) only 5° C produced significantly different growth rates. Low temperature reduced growth to such an extent that macrothalli of a size that could be recognized in the field took approximately two months to produce in culture. These results may explain the seasonal presence/absence of the delophycean phase of C. peregrina in the field. Zoospore survivorship and macrothallus production of C. peregrina in culture indicated that both PES and an artificial medium were suitable for the laboratory cultivation of this plant.     

DIFFERENTIAL LIFE HISTORY PHASE EXPRESSION IN TWO COEXISTING SPECIES OF SCYTOSIPHON (PHAEOPHYCEAE) IN NORTHERN CHILE1

The identity of two phaeophycean taxa that monopolized the middle‐lower rocky intertidal zone of a coastal area chronically exposed to copper mine wastes in northern Chile was unraveled. One of them was preliminarily identified as the gametophytic stage of Scytosiphon lomentaria (Lyngbye) Link. The other, a dark crust, resembled the alternate stage of some Scytosiphon species. Comparative analysis of morphology, life history, and DNA sequences strongly suggests that crusts corresponded to sporophytic S. tenellus Kogame and confirm that erect thalli belonged to S. lomentaria. A clear segregation of erect and crustose thalli was found using internal transcribed spacer region 1 and RUBISCO spacer sequences. Furthermore, whereas crusts always grouped with S. tenellus, erect thalli always grouped with S. lomentaria. Life history studies failed to connect the two entities. First, field‐collected S. tenellus produced progeny that either recycled the crust, which reproduced by unilocular zoidangia, or developed into erect thalli. The latter, unlike typical gametophytic S. lomentaria, developed patchy sori of plurilocular zoidangia. Second, S. lomentaria displayed a direct‐type life cycle, in which progeny from erect individuals only developed into erect thalli and produced only plurilocular zoidangia. This constitutes the first experimental study on Scytosiphon from the Pacific coast of South America and the first report of S. tenellus on this coast. It is also the first report of the crustose stage of Scytosiphon appearing as a perennial and dominant algal species in a temperate rocky intertidal system.     

GEOGRAPHIC VARIATION IN THE LIFE HISTORY OF MASTOCARPUS PAPILLATUS (RHODOPHYTA)1

Variation in the geographic distribution of the life histories of Mastocarpus papillatus was investigated. Carpospores were isolated from 377 female gametophytes collected from eight localities on the Pacific coast of Baja California, Mexico, and California, U.S.A., and grown in laboratory culture. All carpospores from a single female gave rise either to basal discs with gametophyte-like uprights or crustose plants formerly referred to the genus Petrocelis. Early stages in the development of each type of germling were observed, and environmental factors affecting development were suggested. Based on carpospore germlings, females from each location were scored as having either the 1) sexual life history (crustose germlings) or 2) direct-development life history (discoid germlings with uprights). All females from the two southernmost locations in Baja California exhibited the sexual life history. In the three locations from the central-southern California coast, 70-95% of the females exhibited the sexual life history and the remainder exhibited the direct-development life history. In two of the three populations from the central-northern California coast, 70-90% of the females exhibited the direct-development life history and the remainder the sexual life history. In the third location from the central-northern California coast, the northernmost location sampled in the current study, 60% of the females exhibited the sexual life history and 40% the direct-development life history. The relative ecological advantages and disadvantages of the life histories are unknown as are the environmental factors that produced the ratios of sexual to direct-development females observed at each location.     

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.     

DISTINCTION OF SOUTH AMERICAN HAPLOGLOIA ANDERSONII AND CHORDARIA LINEARIS (PHAEOPHYCEAE) BASED ON DIFFERENCES IN SEXUAL REPRODUCTION,MORPHOLOGY, ECOPHYSIOLOGY,AND DISTRIBUTION1

Haplogloia andersonii (Farlow) Levring is an anti-tropical species that occurs on cold and warm-temperate Pacific coasts of both Americas. In its habit it resembles the subantarctic species Chordaria linearis (Hooker et Harvey) Cotton. Culture studies show that the species differ in morphology and ecophysiology of their microscopic gametophytes and in gamete behavior. Details of sporophyte anatomy are presented that also allow the distinction of field plants. In South America, H. andersonii occurs only on the Pacific coast, from central Perú (14°S) to southern Chile (50°S). Chordaria linearis occurs on the Pacific coast from Chiloé Island (43°S) to Cape Horn (56°S). In the shared area the species may co-occur. On the Atlantic coast, C. linearis was newly collected at a locality in northern Patagonia (41°S). In addition, C. linearis occurs in Antarctica. Haplogloia moniliformis Richer, recently described from Macquarie Island, is probably synonymous with Chordaria linearis.     

LIFE IN THE FAST LANE: THE LIFE HISTORY OF HARBOR PORPOISES FROM THE GULF OF MAINE

We describe the life history of harbor porpoises in the Gulf of Maine by examining 239 animals killed in gill net fisheries and comparing these findings with the results of previous studies from the Bay of Fundy. Most female porpoises matured at age three and became pregnant each year thereafter. Reproduction was strictly seasonal, with ovulation, conception, and parturition occurring in the spring and early summer. The oldest specimen in the sample was 17 yr of age, but most individuals were younger than 12. The findings are similar to those of earlier studies from the Bay of Fundy and support the hypothesis that these animals form a single population. Harbor porpoises represent one end of a continuum of odontocete life histories that spans a wide diversity of strategies. In comparison with other, large odontocetes, harbor porpoises mature at an earlier age, reproduce more frequently, and live for shorter periods.     

REPRODUCTION AND LIFE HISTORY OF THE RED ALGA GALAXAURA OBLONGATA (NEMALIALES,GALAXAURACEAE)1

Culture and morphological studies showed that Galaxaura oblongata (Ellis et Solander) Lamouroux has a triphasic life history with conspicuous gametophytes and small filamentous tetrasporophytes. Development of male and female reproductive structures is very similar and both begin with the enlargement of a terminal cell of a filament branch occupying a normal vegetative position within the apical pit of a thallus branch. In male thalli this modified branch forms a conceptacle in which spermatangia are produced. In female thalli, this modified branch forms a three-celled carpogonial branch consisting of a carpogonium, hypogynous cell and basal cell. Filament branches from the basal cell form a pericarp and the gonimoblast develops directly from the carpogonium. Carposporangia are produced in conceptacles which resemble the male conceptacles. About the time the first carposporangia are produced, the carpogonium, hypogynous cell and basal cell form a large fusion cell. Released carpospores germinate in a unipolar or bipolar manner and form small filamentous thalli. Under short day conditions, cruciate tetrasporangia are produced in small clusters. Tetraspores germinate similarly to carpospores and also form small filamentous thalli. Under low nutrient conditions, small cylindrical thalli develop on the filaments and these appear similar to gametophytes collected in nature.     

LIFE HISTORY AND THE EVOLUTION OF PARENTAL CARE

Patterns of parental care are strikingly diverse in nature, and parental care is thought to have evolved repeatedly multiple times. Surprisingly, relatively little is known about the most general conditions that lead to the origin of parental care. Here, we use a theoretical approach to explore the basic life‐history conditions (i.e., stage‐specific mortality and maturation rates, reproductive rates) that are most likely to favor the evolution of some form of parental care from a state of no care. We focus on parental care of eggs and eggs and juveniles and consider varying magnitudes of the benefits of care. Our results suggest that parental care can evolve under a range of life‐history conditions, but in general will be most strongly favored when egg death rate in the absence of care is high, juvenile survival in the absence of care is low (for the scenario in which care extends into the juvenile stage), adult death rate is relatively high, egg maturation rate is low, and the duration of the juvenile stage is relatively short. Additionally, parental care has the potential to be favored at a broad range of adult reproductive rates. The relative importance of these life‐history conditions in favoring or limiting the evolution of care depends on the magnitude of the benefits of care, the relationship between initial egg allocation and subsequent offspring survival, and whether care extends into the juvenile stage. The results of our model provide a general set of predictions regarding when we would expect parental care to evolve from a state of no care, and in conjunction with other work on the topic, will enhance our understanding of the evolutionary dynamics of parental care and facilitate comparative analyses.     

ARE LIFE HISTORY CHARACTERISTICS GOOD PREDICTORS OF GENETIC DIVERSITY AND STRUCTURE? A CASE STUDY OF THE INTERTIDAL ALGA FUCUS SPIRALIS (HETEROKONTOPHYTA; PHAEOPHYCEAE)1

Characteristics of an organism's life history are often good predictors of genetic diversity and genetic structure. We tested hypotheses about genetic structure and diversity in an intertidal alga based on life history and life form. Fucus spiralis L. is a perennial monoecious alga that is abundant on the shores of Maine. Reproduction in fucoids is highly sensitive to water motion, resulting in fertilization success close to 100%. Given these life history characteristics, we predicted genetic structure among populations to be high and genetic diversity within populations to be low. We used five microsatellite loci to analyze genetic structure and diversity in F. spiralis from four sites on each of two coastal points, Maine, USA. Observed heterozygosities were relatively low (0.23 to 0.56), and F_IS estimates were usually significantly large, ranging from 0.021 to 0.476. This suggests that selfing and/or inbreeding may occur. Contrary to predictions, genetic differentiation between the two coastal points was insignificant. Moreover, few sites were genetically different from one another. Pairwise tests revealed complex patterns among sites. Genetic differentiation was not correlated with distance (P>0.05). Life history characteristics are good predictors of genetic diversity but not of population genetic structure in F. spiralis. We suggest that long distance dispersal of F. spiralis via drifting algal rafts increases gene flow. In addition, low levels of genetic structure may arise due to episodic recruitment or recent recolonization events. We discuss the implications of our results in terms of using life history characteristics as predictors of genetic diversity and structure in algae.     

LIFE HISTORY AND GROWTH OF LAURENCIA BRACHYCLADOS (RHODOPHYTA,CERAMIALES)1

Laurencia brachyclados Pilger from Hawai'i completed a “Polysiphonia-type” tri-phasic life history in 21 weeks in laboratory culture. Tetraspores developed into gametophytes in a nearly 1:1:1 ratio of females: males: non-reproductive. Carpospores were released as early as 21 days after mixing virgin female and male gametophytes. Cultured thalli showed a “guerilla type” growth form. Other Hawaiian Laurencia species in culture had longer maturation times or remained non-reproductive. Variation in life history schedules may influence Laurencia species coexistence and algal community structure.