EVIDENCE FOR SEXUAL REPRODUCTION IN THE PRIMITIVE GREEN ALGA NEPHROSELMIS OLIVACEA (PRASINOPHYCEAE)1

Evidence for a specialized sexual process in Nephroselmis olivacea Stein is presented. This alga is a member of the Prasinophyceae, which is regarded by some as the most primitive Class of green plants. N. olivacea has a heterothallic type of mating system. Plus and minus gametes were morphologically similar but showed different behaviors during the mating process. The minus gamete settled to the substratum, attaching by its ventral side. The plus gamete attached to the dorsal side of the minus gamete by the region near the flagellar bases of the plus gamete. The mature zygotes were spherical and strongly adhered to the substratum. After zygote germination, two biflagellate daughter cells, each with two pyrenoids were liberated. These cells divided, resulting in four vegetative cells, each with a single pyrenoid.     

OBSERVATIONS ON THE MORPHOLOGY AND SEXUAL REPRODUCTION OF COOLIA MONOTIS (DINOPHYCEAE)1

The surface morphology of the dinoflagellate Coolia monotis Meunier was compared with the surface morphology of Ostreopsis, The apical pore of C. monotis is similar in architecture to that of Ostreopsis but considerably longer (12 μm) than in O. heptagona (8–9 μm) and O. ovata (6–7 μm). A ventral pore in C. monotis is located on the right ventral margin between apical plate l′ and precingular plate 6″ and is similar in appearance and location to the ventral pore of O. ovata. The longitudinal flagellum (20 μm) in C. monotis is longer than in O. ovata (12 μ). Although Coolia and Ostreopsis appear to be distinctly different and should remain as two separate genera, they appear to be related. Cells of C. monotis divided by binary fission. Doubling time was 3–4 days in the logarithmic phase of growth at 23°C, 12:12 h L:D, 30–90 μE-m^?2·s^?1, and a salinity of 36%. Cultures reached cell densities of 2.5 × 10³ cells·L^?1 after 15 days of growth. The sexual process in C. monotis occurred in Erdschreiber's medium when Danish soil extract was substituted with mangrove sediment extract under the culture conditions described above. Gamete fusion produced large biflagellated planozygotes (70–75 μm diam). Planozygote maturation involved cytoplasmic reorganization, loss of motility, development of a spherical shape (80–90 μm diam), and two to three orange accumulation bodies. The cells at this stage appeared to be thin-walled cysts. Further development included reorganization of cyst contents, emergence of non-motile gametes, and development of chloroplasts, sulcus, and girdle. The nucleus of the newly formed cells occupied 50% or more of the total cell volume. Meiosis occurred in the cyst, but nuclear cyclosis was not observed. Four daughter cells were produced within 36–48 h, and motile gametes developed. The gametes exhibited sexuality for 2 months and completed the sexual life cycle by going through a thin-walled cyst stage.     

双角多甲藻有性生殖的初步观察

通过对双角多甲藻有性过程的初步研究,表明在这种间核生物的生活史中存在着典型的育性生殖。在双角多甲藻春季生长高峰的末期(3月底至4月初),有性生殖大量发生。形成的合子经过一系列变化后成为厚垣合子进入休眠期。     

ASEXUAL AND SEXUAL REPRODUCTION IN GONIUM QUADRATUM (CHLOROPHYTA) WITH A DISCUSSION OF PHYLOGENETIC RELATIONSHIP WITHIN THE GONIACEAE1

Morphological details of asexual and sexual reproduction in Gonium Quadratum Pringsheim ex Nozaki (Goniaceae, Chlorophyta) were observed by light microscopy, based on clonal cultured materials originating from Nepal. In asexual reproduction, the alga exhibited two different patterns of cell cleavage during formation of 8-and 16-celled daughter colonies. Sexual reproduction was heterothallic and isogamous. The gametes bore a tubular mating structure (bilateral mating papilla) at the base of the flagella, and the papillae of the two gametes. The germinating zygote gave rise to four biflagellate gone cells joined in a colony (germ colony). Possible phylogenetic relationships within the Goniaceae at the species level are outlined, mainly on the basis of reproduction characteristics.     

REVISION OF THE MASTOPHOROIDEAE (CORALLINALES,RHODOPHYTA) AND POLYPHYLY IN NONGENICULATE SPECIES WIDELY DISTRIBUTED ON PACIFIC CORAL REEFS1

The subfamily Mastophoroideae (Corallinaceae, Rhodophyta) is characterized by species possessing nongeniculate, uniporate tetrasporangial conceptacles without apical plugs, the presence of cell fusions, and the absence of secondary pit connections. However, molecular phylogenetic studies not including the type genus Mastophora indicated that the Mastophoroideae was polyphyletic. Our molecular phylogenetic analysis of the subfamily including the type genus using DNA sequences of SSU rDNA and plastid‐encoded gene of PSII reaction center protein D1 (psbA) revealed that Mastophora formed a robust clade only with Metamastophora. The other mastophoroid genera were divided into six lineages within the family Corallinaceae. Five supported lineages—(i) Pneophyllum; (ii) Hydrolithon gardineri (Foslie) Verheij et Prud’homme, Hydrolithon onkodes (Heydr.) Penrose et Woelk., and Hydrolithon pachydermum (Foslie) J. C. Bailey, J. E. Gabel et Freshwater; (iii) Hydrolithon reinboldii (Weber Bosse et Foslie) Foslie; (iv) Spongites; and (v) Neogoniolithon—were clearly distinguished by the combination of characters including the presence or absence of palisade cells and trichocytes in large, tightly packed horizontal fields and features of tetrasporangial and spermatangial conceptacles. Therefore, we amend the Mastophoroideae to be limited to Mastophora and Metamastophora with a thin thallus with basal filaments comprised of palisade cells, tetrasporangial conceptacles formed by filaments peripheral to fertile areas, and spermatangia derived only from the floor of male conceptacles. This emendation supports Setchell’s (1943) original definition of the Mastophoroideae as having thin thalli. We also propose the establishment of three new subfamilies, Hydrolithoideae subfam. nov. including Hydrolithon, Porolithoideae subfam. nov. including the resurrected genus Porolithon, and Neogoniolithoideae subfam. nov. including Neogoniolithon. Taxonomic revisions of Pneophyllum and Spongites were not made because we did not examine their type species.     

EFFECTS OF HYDROXAMATE SIDEROPHORES (STRONG Fe (III) CHELATORS) ON THE GROWTH OF ALGAE1

Varying concentrations of Fe were tested with three hydroxamate siderophores to demonstrate the interactions affecting growth of Chlamydomonas reinhardtii and Chlorella vulgaris. Schizokinen was purified from the excretions of the blue-green alga Anabaena sp. grown in low-Fe medium. Chlamydomonas reinhardtii was inhibited by schizokinen when in molar excess of the Fe concentration; the inhibition was overcome with excess Fe. The growth of C. vulgaris was not affected by this chelator. Results with desferrioxamine were similar. A weaker chelator, rhodorulic acid, did not inhibit the growth of either alga. Low concentrations of the chelators may stimulate algal growth when Fe precipitates are hydrolyzed. Since different algae respond differently to the presence of the chelators, the observed interactions could be important in determining competitive relationships when Fe is limiting. If an alga can excrete a strong chelating agent, as does Anabaena, algae lacking the ability to compete with the chelator may not grow.     

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。     

THE LIFE HISTORY OF FREE-RANGING ATLANTIC SPOTTED DOLPHINS (STENELLA FRONTALIS): AGE CLASSES, COLOR PHASES, AND FEMALE REPRODUCTION

Atlantic spotted dolphins (Stenella frontalis) were observed underwater and from the surface from 1985 to 1996 and photographed through successive years. Individuals were categorized into age classes by their degree of spotting and color phases. Dolphins spent an average of 3 yr in the two-tone color phase, 5 yr in the speckled phase, 7 yr in the mottled phase and up to 10 yr or more in the fused phase.
Sex ratios were close to parity, with old adults skewed towards females and juveniles and young adults skewed towards males. The average calving interval for 24 females was 2.96 years with a range of 1–5 yr. Females whose calves survived the first year had a significantly longer calving interval (3.56 years). The ages of first parturition for five females were estimated to be 10–12 yr. The age at sexual maturation was estimated to range from 8 to 15 yr.
Pregnancy rate fluctuated annually, with an average rate of 0.25 (range 0.07–0.57). Annual average birth rate was 0.08 (range 0.07–0.14), average calf production was 0.33 (range 0.06–0.52), average fecundity was 0.23 (range 0.13–0.30), and average recruitment was 0.06 (range 0.03–0.08). Most females who lost a calf conceived the same or following year.
Lactation lasted up to 5 yr, and 45% of visibly pregnant females were also lactating. Age of first parturition was associated with the mottled color phase. Average first-year mortality rate of calves was 0.24.     

PHOTOSYNTHESIS OF THE RED ALGA GASTROCLONIUM COULTERI (RHODOPHYTA) IN RESPONSE TO CHANGES IN TEMPERATURE,LIGHT INTENSITY,AND DESICCATION1

Previously reported transplantation experiments in the field showed that Gastroclonium coulteri (Harvey) Kylin could survive above its normal intertidal range (0.0–0.5 m above MLLW), except during periods of daytime low tides in spring. Net photosynthetic rate measurements in the laboratory were performed to determine which physical factors might determine the upper boundary for this species in the intertidal zone. Maximum net photosynthesis occurred between 15 and 20° C, but remained positive between 4 and 35° C. The air temperature extremes observed in the field were 2° C (only seen once) and 26° C. Net photosynthesis increased as expected with light intensity to the highest value obtainable in the laboratory, 1400 μEin m^?2 s^?1. Plants collected from the field under higher light intensity (up to 2000 μEin m^?2 s^?2) also showed high rates of photosynthesis. Neither the temperature nor light levels observed in the field were directly damaging to photosynthesis. Desiccation, however, resulted in a sharp decrease in both photosynthesis and respiration. G. coulteri fully recovered from successive daily treatments of about 35% desiccation, but not from successive treatments of 50% desiccation. One exposure to 70% desiccation allowed no recovery of photosynthetic capacity.     

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.