PHYSIOLOGICAL PERFORMANCE OF FLOATING GIANT KELP MACROCYSTIS PYRIFERA (PHAEOPHYCEAE): LATITUDINAL VARIABILITY IN THE EFFECTS OF TEMPERATURE AND GRAZING1

Rafts of Macrocystis pyrifera (L.) C. Agardh can act as an important dispersal vehicle for a multitude of organisms, but this mechanism requires prolonged persistence of floating kelps at the sea surface. When detached, kelps become transferred into higher temperature and irradiance regimes at the sea surface, which may negatively affect kelp physiology and thus their ability to persist for long periods after detachment. To examine the effect of water temperature and herbivory on the photosynthetic performance, pigment composition, carbonic anhydrase (CA) activity, and the nitrogen (N) and carbon (C) content of floating M. pyrifera, experiments were conducted at three sites (20° S, 30° S, 40° S) along the Chilean Pacific coast. Sporophytes of M. pyrifera were maintained at three different temperatures (ambient, ambient ? 4°C, ambient + 4°C) and in presence or absence of the amphipod Peramphithoe femorata for 14 d. CA activity decreased at 20° S and 30° S, where water temperatures and irradiances were highest. At both sites, pigment contents were substantially lower in the experimental algae than in the initial algae, an effect that was enhanced by grazers. Floating kelps at 20° S could not withstand water temperatures >24°C and sank at day 5 of experimentation. Maximal quantum yield decreased at 20° S and 30° S but remained high at 40° S. It is concluded that environmental stress is low for kelps floating under moderate temperature and irradiance conditions (i.e., at 40° S), ensuring their physiological integrity at the sea surface and, consequently, a high dispersal potential for associated biota.     

PRESENCE OF SPOROPHYLLS IN FLOATING KELP RAFTS OF MACROCYSTIS SPP. (PHAEOPHYCEAE) ALONG THE CHILEAN PACIFIC COAST1

Some species of macroalgae continue to live for extended periods of time after detachment and may even maintain reproductive structures, yet very little is known about this process. Here, we describe the presence of sporophylls (with sporogenous tissues) on floating kelp rafts of Macrocystis spp. along the coast of Chile. Surveys were conducted at nine sites (18–50° S) during austral summer 2002, and floating kelp rafts were seen and collected at seven of these nine sites (between 22 and 50° S). Fifteen (26.8%) of the 56 samples had sporophylls, indicating maintenance of sporophylls after detachment. Some of the kelp sporophytes with reproductive blades showed signs of having been afloat for long periods (indicated by the large size of attached stalked barnacles). Additionally, experiments showed that floating kelps released viable zoospores. To understand the reproductive dynamics of floating kelps, we compared these results with information from attached populations of Macrocystis spp. at nearby coastal sites. In general, attached kelp had higher proportions of sporophylls than floating rafts, suggesting that detachment may negatively affect reproductive status. Nevertheless, floating kelps remained functionally reproductive, suggesting that zoospores may be dispersed via floating rafts. Published reports on other macroalgae indicate that some species (Lessoniaceae, Fucaceae, and Sargassaceae) are fertile and probably release zoospores or zygotes while floating or drifting in ocean currents. Because dispersal distances achieved by spores of most macroalgae are relatively short, release of spores from floating algae may be an alternative mechanism of long‐distance dispersal.     

ROLE OF SETTLEMENT DENSITY ON GAMETOPHYTE GROWTH AND REPRODUCTION IN THE KELPS PTERYGOPHORA CALIFORNICA AND MACROCYSTIS PYRIFERA (PHAEOPHYCEAE)1

Laboratory studies were used to examine how variation in the density of spore settlement influences gametophyte growth, reproduction, and subsequent sporophyte production in the kelps Pterygophora californica Ruprecht and Macrocystis pyrifera (L.) C. Ag. In still (non-aerated) cultures, egg maturation in both species was delayed when spores were seeded at densities 300 · mm^?2. Although the density at which this inhibition was first observed was similar for both species, the age at which their eggs matured was not. P. californica females reached sexual maturity an average of 4 days (or ～ 30%) sooner than did M, pyrifera. As observed previously in field experiments, per capita sporophyte production was negatively density dependent for both species when seeded at spore densities of 10 · mm^?2. Total sporophyte production (i.e. number · cm^?2) for both species, however, was greatest at intermediate densities of spore settlement (～ 50 spores · mm^?2). In contrast, total sporophyte production by P. californica steadily increased with increasing spore density in aerated cultures; highest sporophyte density was observed on slides seeded at a density of 1000 spores · mm^?2. Preliminary experiments with P. californica involving manipulation of aeration and nutrients indicate that inhibition of gametophyte growth and reproduction at higher densities of spore settlement in non-aerated cultures was probably caused by nutrient limitation.     

蚤状蚤的生长和生殖

在３５、３０、２５℃３种温度下观察了蚤状（Ｄａｐｈｎｉａｐｕｌｅｘ）的生长和生殖。其生长随年龄的增加而逐渐减慢，寿命因温度升高而缩短。在２５℃条件下，蚤状寿命、产仔数和产仔率明显高于其他组，其平均寿命为６５．５天，累计产仔总数为４０１．６个，产仔率为２１．２２。     

ROLE OF NUTRIENT FLUCTUATIONS AND DELAYED DEVELOPMENT IN GAMETOPHYTE REPRODUCTION BY MACROCYSTIS PYRIFERA (PHAEOPHYCEAE) IN SOUTHERN CALIFORNIA1

Organisms occurring in environments subject to severe disturbance and/or periods of poor environmental quality that result in severe adult mortality can survive these periods by relying on alternate life stages that delay their development in a resistant state until conditions improve. In the northeast Pacific, the forest‐forming giant kelp Macrocystis pyrifera (L.) C. Agardh periodically experiences widespread adult mortality during extended periods of extremely low nutrients and high temperatures, such as those associated with El Niño. Recovery following these periods is hypothesized to occur from microscopic life stages that delay their development until the return of favorable conditions. In the laboratory, we experimentally examined the environmental conditions responsible for regulating delayed development of the microscopic stages of M. pyrifera from Southern California, USA. Nutrients controlled the delay and resumption of gametophyte growth and reproduction, perhaps linked to the large fluctuations in nutrients occurring seasonally and interannually in this region. Although growth of gametophytes proceeded in the virtual absence of nitrate, both nitrate and other trace nutrients were necessary for gametogenesis. Upon exposure to elevated nutrients, delayed gametophytes produced sporophytes more quickly (5–20 d) and at smaller sizes (10–200 μm) than gametophytes that had never been delayed (18–80 d, 80–400 μm, respectively), reducing negative density‐dependent effects. This finding demonstrates that delayed gametophytes of M. pyrifera rapidly utilize increased resources to consistently produce sporophytes. Further work is needed to assess their potential role in population recovery following periods of poor environmental quality.     

NORTHERN AND SOUTHERN HEMISPHERE HYBRIDS OF MACROCYSTIS (PHAEOPHYCEAE)1

All combinations of individuals of Macrocystis pyrifera (L.) C. Agardh, M. integrifolia Bory, and M. angustifolia Bory hybridized. Gametophyte isolates obtained from 18 individuals were used, including M. pyrifera and M. integrifolia from the extremes of their Northern Hemisphere ranges along the Pacific Coast of North America and M. pyrifera and M. angustifolia from Tasmania, Australia. All combinations of gametophytes produced sporophytes of normal morphology, with the exception of crosses involving three gametophyte isolates. One female (M. integrifolia) and two male (M. pyrifera and M. angustifolia)gametophyte isolates were unable to produce normal sporophytes in combination with gametophytes of the opposite sex. Some cultures of female gametophytes produced abnormally shaped parthenogenetic sporophytes. Gametophytes and sporangia of M. pyrifera had n= 16 chromosomes. The M. integrifolia female gametophyte that was unable to produce normal sporophytes had n = ca. 32 chromosomes. These results show that these species of Macrocystis have not become reproductively isolated. Although these species may be considered conspecific according to the biological species concept, we recommend that they continue to be recognized as separate species based on morphological differences.     

PHOSPHORUS AND THE GROWTH OF JUVENILE MACROCYSTIS PYRIFERA (PHAEOPHYTA) SPOROPHYTES1

The effect of phosphate (P_i) supply on growth rate and tissue phosphorus content of juvenile Macrocystis pyrifera (L.) C. Ag. sporophytes was examined. Sporophytes were batch cultured in aquaria with flowing recirculated seawater enriched by 30 μM nitrate. Each aquarium was supplemented with a different seawater P_i concentration, 0, 0.3, 1, 2, 3, and 6 μM. Sporophyte mean specific growth rates declined with time in all cultures presumably due to the normal developmental decrease in the proportion of meristematic tissue of each plant. Growth rate declines were more pronounced in cultures that were nutrient limited. Sporophyte growth was P-limited after two-week exposure to P_i less than 1 μM, corresponding to a tissue P concentration of less than 0.20% dry weight. Plants cultured at 6 μM P_i contained tissue P levels of 0.53% dry weight after three weeks. Luxury consumption and storage of P occurred.     

EFFECT OF TEMPERATURE AND IRRADIANCE ON GROWTH OF HAEMATOCOCCUS PLUVIALIS (CHLOROPHYCEAE)1

The growth characteristics of Haematococcus pluvialis Flotow were determined in batch culture. Optimal temperature for growth of the alga was between 25° and 28°C, at which the specific growth rate was 0.054 h^?1. At higher temperatures, no cell division was observed, and cell diameter increased from 5 to 25 μm. The saturated irradiance for growth of the alga was 90 μmol quanta · m^?2·s^?1; under higher irradiances (e.g. 400 μmol quanta·m^?2·s^?1) astaxanthin accumulation was induced. Growth rate, cell cycle, and astaxanthin accumulation were significantly affected by growth conditions. Careful attention should be given to the use of optimal growth conditions when studying these processes.     

REPRODUCTIVE LONGEVITY OF DRIFTING KELP MACROCYSTIS PYRIFERA (PHAEOPHYCEAE) IN MONTEREY BAY,USA1

Drifting Macrocystis pyrifera (L.) C. Agardh sporophytes have long been viewed as the primary long‐distance dispersal vector; yet, few data exist that support the ability of reproductive viable sporophytes to actually travel the presumed hundreds to thousands of kilometers. This study addressed the reproductive longevity of experimental and naturally occurring M. pyrifera drifters. Temporal variability in sporophyte size and reproduction was estimated for experimental drifting sporophytes that were tethered to surface buoys and compared with attached plants (controls). Reproductive viability was also studied for beach‐cast drifters (BCD), and naturally drifting sporophytes observed during field surveys in Monterey Bay. Detached drifting sporophytes were tracked with radio transmitters to follow drifter trajectories and to measure drifting speed. Experimental drifters (ED) experienced a 74% reduction in frond length after 35 days, a 76% reduction in average frond number after 70 days, and a reduction in average sorus area by 83% after 28 days. Although zoospore production was reduced following detachment, sporophytes remained fertile with high zoospore germination success as long as sori were present (125 days). Zoospore production and germination success for natural and BCD was similar to ED. The average displacement of radio‐tagged drifters was 7.12 km·day^?1, suggesting that a sporophyte adrift for 125 days disperses viable propagules (zoospores) over 890 km (±363). Dispersal of propagules is important for population restoration, distribution, and genetic diversity. Such dispersal distances are long enough to connect potentially all Northern Hemisphere Macrocystis populations across a generational timescale and may facilitate inter‐hemispheric gene flow.     

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.     

温度对烟粉虱发育和繁殖的影响

研究了7个不同温度梯度对烟粉虱(Beimisia tabaci )B生物型发育、存活和繁殖的影响。在17℃时,烟粉虱从卵到成虫羽化需要48．7天,而在29℃则仅需要13．9天。烟粉虱发育的最佳温度是26℃,低温(＜20℃)和过高的温度(＞32℃)对烟粉虱发育有抑制作用。经线性回归分析,烟粉虱的发育起点温度约为13℃,有效积温为263．8℃。烟粉虱在20℃时,其成虫寿命和产卵量都是32℃时2倍多,单雌最高产卵量达到208粒。烟粉虱的存活率以26℃时最高,低温和高温对烟粉虱的存活率有负面影响。烟粉虱的内禀增殖率在26℃和29℃时较高,分别为0．1456和0．1470。所有数据显示26℃是烟粉虱种群发育和繁殖的最佳温度。     

EFFECT OF TEMPERATURE ON THE DEVELOPMENT AND REPRODUCTION OF BEMISIA TABACI B BIOTYPE (HOMOPTERA: ALEYRODIDAE)

Abstract The development, survivorship and reproduction of Bemisia tabaci B biotype on eggplant at seven constant temperatures (17, 20, 23, 26, 29, 32 and 35°C) were studied. The developmental periods from egg to adult varied from 48.7 days at 17°C to 13.9 days at 29°C and the developmental threshold estimated for a generation by linear regression was 12.4°C. The optimum temperature for B. tabaci population growth was 26°C, both extremely low (< 17°C) and high temperature (> 32°C) delayed the development. Survivorships from egg to adult was 67.3% at 26°C, 27.6% and 29.0% at 35°C and 17°C respectively. The average longevity of females ranged from 39.6 days at 20°C to 12.8 days at 35°C. Oviposition per female varied from 164.8 eggs at 20°C to 78.5 eggs at 32°C. Both the longevity and oviposition of B. tabaci females at different temperatures were significantly different ( P < 0.05), and the intrinsic rate of natural increase ( r _m) for B. tabaci at 29°C was the highest.     

DISPERSAL OF HORMOSIRA BANKSII (PHAEOPHYCEAE) VIA DETACHED FRAGMENTS: REPRODUCTIVE VIABILITY AND LONGEVITY1

Drifting, fertile thalli are well documented to be the primary long‐distance dispersal vector for many marine macroalgae, but little information about reproductive viability of drift is known. This study examined the reproductive viability and longevity of floating fragments of the intertidal Australasian fucoid Hormosira banksii (Turner) Decne. Beach wrack surveys and field experiments were conducted to test the model that long‐distance dispersal is achieved in H. banksii via floating, fertile fronds. High densities of beach wrack fragments were evident during summer compared to autumn. The majority of beach wrack occurred on sandy beaches rather than rocky shores. Both male and female fragments were present in the beach wrack. Detached fronds were capable of releasing gametes up to 8 weeks after detachment. Beach wrack produced high fertilization rates and recruited successfully onto artificial panels. Results suggest that detached fragments are reproductively viable and that floating, fertile fronds may be an important mechanism for facilitating long‐distance dispersal in this species. Nevertheless, the frequency of fronds reaching a suitable habitat and contributing to gene flow between populations, or colonizing new populations, may not be proportional to the total density of beach wrack.     

A FIELD-COMPATIBLE METHOD FOR EXTRACTION OF FINGERPRINT-QUALITY DNA FROM MACROCYSTIS PYRIFERA (PHAEOPHYCEAE)1

A method for extracting DNA from laminarialean algae resulting in DNA of sufficient quantity and purity for DNA fingerprints is presented. The method both eliminates the use of liquid N₂ and delays the use of toxic chemicals in the initial extraction steps; thus, it is appropriate for use in remote field locations. The algal samples were ground in a solution of hexadecyltrimethylammonium bromide (CTAB) and polyvinylpyrrolidone (PVPP) at room temperature and then stored for 1 week in the CTAB-PVPP solution at room temperature before extraction with chloroform-isoamyl alcohol and purification by cesium chloride ultracentrifugation. No degradation of DNA was observed. Hybridization of RsaI-digested Macrocystis pyrifera (L.) C. Ag. DNA with the M13repeat probe yielded a DNA fingerprint with 12 discrete bands 4–19 kb in molecular size.     

GENETIC VARIABILITY WITHIN A POPULATION AND BETWEEN DIPLOID/HAPLOID TISSUE OF MACROCYSTIS PYRIFERA (PHAEOPHYCEAE)1

Multi-locus DNA fingerprints using an M13 probe were obtained for eight individuals of giant kelp Macrocystis pyrifera (L.) C. Ag. collected from Monterey Bay, California. For each individual, DNA was extracted from a diploid blade and from ca. 10⁹ haploid spores that were released from four to Jive sporophylls. Viable or swimming spores from one individual were pooled and referred to as a spore group. A total of 34 bands (4–19 kb) was detected in DNA fingerprints from the eight blades and eight spore groups, with individual blade or spore groups exhibiting 7–18 bands (mean = 12.6). One band (4.5 kb) was present in all 16 samples. Eight bands were detected in 11–14 of the 16 samples. Similarity indices were calculated for all pairwise comparisons of fingerprint bands among all possible combinations of blades and spore groups. Mean similarity indices for the eight blades (0.51, SE = 0.032) and spore groups (0.56, SE = 0.031) were significantly lower than for the eight comparisons of the blade and spore groups from a single individual (0.86, SE = 0.052). The data indicate that DNA fingerprints can be used to measure genetic variation within populations of M. pyrifera because variation of DNA fingerprints associated with meiotic products (spores) of a given individual is small relative to variation observed among individuals within the population. Additionally, fingerprint variation between diploid vegetative tissue and haploid meiotic products may be a measure of genetic change due to recombination or DNA turnover mechanisms.     

EFFECT OF HIGH IRRADIANCE ON RECRUITMENT OF THE GIANT KELP MACROCYSTIS (PHAEOPHYTA) IN SHALLOW WATER1

Laboratory and field experiments were done hi Still-water Cove, Carmel Bay, California, and Monterey Harbor, California, to determine the effect of photosynthetically active radiation (PAR) on the shallow (upper) limit of giant kelp, Macrocystis pyrifera (L.) C. Agardh. At shallow depths, M. pyrifera did not recruit or grow to macroscopic size from gametophytes or embryonic sporophytes transplanted to vertical buoy lines; sharp decreases in PAR with depth coincided with observed recruitment and sporophyte distributions. Shade manipulations indicated that settlement of M. pyrifera zoospores was decreased, but not prohibited, by high PAR. Postsettlement stages (gametophytes and embryonic sporophytes), however, survived only under shade. These results suggest that high PAR can inhibit the recruitment of M. pyrifera to shallow water by killing its postsettlement stages; whether or not ultraviolet (UV) radiation also inhibits recruitment was not tested. In either case, however, it appears that high irradiance (PAR and/or UV) regulates the shallow limit of M. pyrifera prior to temperature and desiccation stresses inherent to intertidal regions. In an additional experiment, recruitment or growth of transplanted gametophytes or embryonic sporophytes of Macrocystis integrifolia Bory also did not occur at shallow depths, suggesting that this shallow water species accesses high irradiance regions via a method other than sexual reproduction.     

GROWTH, REPRODUCTION AND FIELD POPULATION DYNAMICS OF FRANKLINIELLA BISPINOSA (THYSANOPTERA: THRIPIDAE)

Abstract Frankliniella bispinosa was reared at five constant temperatures using pollen of Typha domingensis as food. At 15°C, 37.5 days are required for completing the life cycle and the adult females survived for about 30 days. The immature stage and the female longevity were significantly reduced when temperature increased and they were only 9.2 and 3.9 days, respectively, at 35°C. The maximal number of eggs (123.2/female) were laid at 25°C, as compared with 29.5, 42.1, 11.6 eggs per female, respectively, at 15°C, 20°C and 30°C. F. bispinosa occurs on Bidens pilosa flowers all the year round in south Florida. However, the population is more abundant from mid-March to early April.     

花蓟马Frankliniella bispinosa的生长繁殖特性及种群动态研究(英文)

本文提出一种用香蒲 (Typhadomingensis)花粉饲养花蓟马 (F .bispinosa)的方法 ,恒温饲养表明 ,在1 5℃时 ,该蓟马的世代历期长达 3 7 5d ,雌成虫平均寿命为 3 0d ;在 2 0℃和 2 5℃恒温下 ,世代历期分别为1 8 9和 1 3 8d ,雌成虫寿命分别为 2 9 0和 2 3 3d。平均产卵量在 2 5℃时达到最高 (1 2 3 2头 雌 ) ,而在其他几种恒温下产卵量显著减少。在佛罗里达南部 ,终年可见该蓟马在鬼针三叶草 (BidenspilosaL .)花上发生 ,而种群高峰期在三月中旬到四月初 ,平均每朵花中蓟马成虫数最高时可达 48 7头。     

EFFECTS OF LIGHT AND TEMPERATURE ON NET PHOTOSYNTHESIS AND DARK RESPIRATION OF GAMETOPHYTES AND EMBRYONIC SPOROPHYTES OF MACROCYSTIS PYRIFERA1

The rates of net photosynthesis as a function of irradiance and temperature were determined for gametophytes and embryonic sporophytes of the kelp, Macrocystis pyrifera (L.) C. Ag. Gametophytes exhibited higher net photosynthetic rates based on oxygen and pH measurements than their derived embryonic sporophytes, but reached light saturation at comparable irradiance levels. The net photosynthesis of gametophytes reached a maximum of 66.4 mg O₂ g dry wt^?1 h^?1 (86.5 mg CO₂ g dry wt^?1 h^?1), a value approximately seven times the rate reported previously for the adult sporophyte blades. Gametophytes were light saturated at 70 μE m^?2 s^?1 and exhibited a significant decline in photosynthetic performance at irradiances 140 μE m^?1 s^?1. Embryonic sporophytes revealed a maximum photosynthetic capacity of 20.6 mg O₂ g dry wt^?1 h^?1 (25.3 mg CO₂ g dry wt^?1 h^?1), a rate about twice that reported for adult sporophyte blades. Embryonic sporophytes also became light saturated at 70 μE m^?2 s^?1, but unlike their parental gametophytes, failed to exhibit lesser photosynthetic rates at the highest irradiance levels studied; light compensation occurred at 2.8 μE m^?2 s^?1. Light-saturated net photosynthetic rates of gametophytes and embryonic sporophytes varied significantly with temperature. Gametophytes exhibited maximal photosynthesis at 15° to 20° C, whereas embryonic sporophytes maintained comparable rates between 10° and 20° C. Both gametophytes and embryonic sporophytes declined in photosynthetic capacity at 30° C. Dark respiration of gametophytes was uniform from 10° to 25° C, but increased six-fold at 30° C; the rates for embryonic sporophytes were comparable over the entire range of temperatures examined. The broader light and temperature tolerances of the embryonic sporophytes suggest that this stage in the life history of M. pyrifera is well suited for the subtidal benthic environment and for the conditions in the upper levels of the water column.     

EFFECT OF LIGHT AND TEMPERATURE INTERACTIONS ON GROWTH OF CRYPTOMONAS EROSA (CRYPTOPHYCEAE)1

Cryptomonas erosa Skuja, a planktonic alga, was grown in batch culture at different combinations of light intensity and temperature, under nutrient saturation. Growth was maximal (1.2 divisions · day^?1) at 23.5 C and 0.043 ly · min^?1, declining sharply with temperature (0.025 divisions-day^?1 at 1 C). With decreasing temperature, the cells showed both light saturation and inhibition at much reduced light intensities. At the same time the compensation light intensity for growth declined towards a minimum of slightly above 0.4 × 10^?4 ly · min^?1 (~1 ft-c) at 1 C or <0.1 ly · day^?1 (PAR). Cell division was more adversely affected by low temperature than carbon uptake, and the resulting excess production of photosynthate was both stored and excreted. Extreme storage of carbohydrates resulted in cell volumes and carbon content ca. 22 and 30 × greater, respectively, than the maxima observed for cells incubated in the dark, whereas, at growth inhibitory light levels, as much as 57% of the total assimilated carbon was excreted. A marked increase in cell pigment was observed at the lowest light levels (<10^?3 ly · min^?1), at high temperature. The growth response of C. erosa in culture provides insight into the abundance and distribution of cryptomonads and other small algal flagellates in nature.