EFFECT OF SILICATE LIMITATION ON VALVE MORPHOLOGY IN THALASSIOSIRA AND COSCINODISCUS (BACILLARIOPHYCEAE)1

Coscinodiscus radiatus Ehrenb. and Thalassiosira eccentrica (Ehrenb.) Cleve were grown in a silicate-limited chemostat at silicate concentrations below 1 μg-atoms · l^?1. The resulting abnormal valves of C. radiatus lacked a thickened ring around the foramina; their pore membranes were thinner and their loculi shallower than those in normal cells. Abnormal valves of T. eccentrica had a fasciculate areolae pattern; they lacked a silica covering over the foramina and some tangential areolae walls. Neither abnormal valve could be termed a new species.     

FRUSTULAR MORPHOLOGY AND TAXONOMIC AFFINITIES OF NAVICULA COMPLANATOIDES (BACILLARIOPHYCEAE)1

Live and prepared cells of the marine pennate diatom Navicula complanatoides Hust. were examined with light and electron microscopy. It has narrowly lanceolate valves (26–55 μm long, 4–5 μm wide) and girdles 10–24 μm in depth. Striae are parallel at the center of the valve (24–28 in 10 μm), becoming slightly convergent toward the apices. Electron microscopy revealed that the external valve surface presents a longitudinally ribbed appearance (20–28 parallel ribs at its maximum width), whereas internally, rectangular areolae are occluded by ricae. The raphe slit lies in a narrow axial area, and one side of the raphe sternum is deeper and folds over the other, obscuring the internal opening. Internally, the central virga on one side of the raphe and two virgae on the other are somewhat broader. A conspicuous pore (stigma) is present between the two broadened virgae. The girdle consists of valvocopulae, copulae, and pleurae. There are 16–20 bands per cingulum. The valvocopulae and copulae are hollow tube-like structures, with inner and outer portions contrsting in morphology. They decrease in diameter in an abvalvar direction. There are four pleurae. These are flat bands which facilitate overlap of the epicingulum and hypocingulum. Fundamental features of the valve and girdle reveal the distinctness of this species within Navicula. The areolae, external longitudinal ribs, and raphe structure suggest affinities with Pleurosigma, Gyrosigma, and Haslea. It is hypothesized that they share a derived state which indicates a recent common ancestor for these taxa. N. complanatoides and related species of the Naviculae microstigmatacae are distinctive enough to merit their own genus within the Naviculaceae.     

VALVE AND BAND MORPHOLOGY OF SOME FRESHWATER DIATOMS. V. VARIATIONS IN THE CINGULUM OF PLEUROSIRA LAEVIS (BACILLARIOPHYCEAE)1

Frustule ultrastructure of Pleurosira laevis (Ehr.) Compère from an epilithon sample collected from the Missouri River was examined using scanning electron microscopy. Valve characteristics were similar to those found by other authors, whereas certain features of the cingulum were new. The cingulum consists primarily of three girdle bands (a valvocopula and two pleurae). The valvocopula can be complete but open at one end, below the ocellus. However, it is more commonly bisegmented, with two narrow and severable connecting points located in the pars interior region underlapping the mantle. The first and second pleurae are either biligulate or uniligulate and closed, but the former, when uniligulate, may be an open band as well. The second pleura is narrower and more delicate than the first. When a natural cleavage of a band subtends a ligula, the band is prone to break along the cleavage during specimen preparation, thus making difficult the assessment of band form and cingulum arrangement. Regions of band overlap have smooth poreless edges, whereas those of underlap are rimmed with either fine fimbriae or, occasionally, a coarser comblike fringe. The variability of the bands results in a cingulum that can be assembled in at least four different arrangements.     

THE GENUS ACTINOCYCLUS (BACILLARIOPHYCEAE): FRUSTULE MORPHOLOGY OF A. SAGITTULUS SP. NOV. AND TWO RELATED SPECIES1

Actinocyclus octonarius var. tenellus (Bréb.) Hendey, A. actinochilus (Ehr.) Simonsen and A. sagittulus sp. nov. were examined by light and scanning electron microscopy from field samples and/or culture material. Consistent cingulum patterns of a wide valvocopula and one narrow pleura were found. In A. actinochilus, a small third band was found filling the opening of the pleura and is probably present in the other two taxa. The observed variability of the pseudonodulus, especially in A. actinochilus but also in other members of the genus, was confirmed and our results support the literature definition of Actinocyclus as having: 1) a marginal ring of large labiate processes, laterally expanded internally, 2) no external tubes, 3) essentially radial areolation arranged in fascicles, 4) external cribrum, internal foramen, and 5) a pseudonodulus usually present, but may be absent or difficult to detect on individual valves. On the basis of the present study another characteristic should be added; 6) hyaline bands with a wide valvocopula and at least one pleura. This characteristic appears to extend throughout the family Hemidiscaceae, suggesting a close relationship to those Coscinodiscus species with a single marginal row of large labiate processes and zero or one central labiate processes. In addition, Actinocyclus has been noted to have a thin valve overhang extending outside the valvocopula for as much as one-third of its width.     

VALVE AND BAND MORPHOLOGY OF SOME FRESHWATER DIATOMS. II. INTEGRATION OF VALVES AND BANDS IN NAVICULA CONFERVACEA VAR. CONFERVACEA12

Chemically cleaned and critical-point dried cells of a clonal culture were examined with scanning electron microscopy. Cells form filaments by valve-to-valve connections maintained by organic material which adheres to the central area of the valve face. Bending of filaments is probably restricted to some extent by the articulation of overlapping spatulate marginal spines with an adjacent underlapping set of much shorter spines (ridges), and with the mantle edge itself. Cell division results in three possible spine patterns for each cell: a set of overlapping and a set of underlapping spines; no overlapping sets of spines (two underlapping); or two sets of overlapping spines (no underlapping). Each filament inherits cells with spine set patterns in the ratio of 2 (with 1 set overlapping): 1 (with no sets overlapping): 1 (with 2 sets overlapping). Valvocopulae are shaped similarly to pleurae except that the partes exteriores of the valvocopulae are wider. The pars interior of both is delimited by an advalvar row of pores continuous around the cell apex. The pars exterior also has a row of pores, but it is median in the valvocopula and first pleura and does not continue around the cell apex. The valvocopulae always underlap the mantle and the pleurae always underlap their preceding band. The ends of both appeared attached, but may become free in acid-cleaned preparations. Bands alternate with each other so that the ends of the valvocopula attach to the first continuous apical portion of the first pleura; the ends of the first pleura attach in that same fashion to the second pleura but at the opposite apex; and all subsequent pleurae alternate in the same fashion with up to at least 13 pleurae/epicingulum. The continuous apical portion of each band is elevated so that a functional (but not structural) ligula is formed, with the continuous apical portion of alternate bands becoming adjacent and underlapping each other only in this region. The valvocopulae in a single cell, or of adjacent cells, may have their continuous apical ends on the same or on opposite apices. It is recommended that N. confervacea var. peregrina (W. Sm.) Grun. be merged with the nominate variety.     

FUNCTIONAL VALVE MORPHOLOGY IN SOME SURIRELLA SPECIES (BACILLARIOPHYCEAE) AND A COMPARISON WITH THE NAVICULACEAE1

On the basis of results of stratigraphic and comparative morphological studies on the diatom frustule, the Surirellaceae is generally assumed to be the endpoint of the evolution of the Pennales. The present study shows that a line of development, based on frustule construction and which parallels the search for optimum design of comparable elements in engineering, can be traced from the Naviculaceae to the Surirellaceae. In both cases lightweight construction is achieved through economy of material and energy expenditure. This leads to structural stability and in the case of the diatom valve, a larger area for metabolic exchange. From the functional-morphological point of view, three construction principles can be distinguished in the genus Surirella: 1. valves with pennate costal framework, raphe keels and fibulae (Surirella gemma group); 2. frustules where all supporting elements are in the form of corrugations, with raphe keel and fibulae (Pinnatae, Fastuosae, Surirella striatula group); and 3. as in 2, but with true alae with alar canals (Robustae) instead of keels with fibulae.     

VALVE MORPHOGENESIS AND THE MICROTUBULE CENTER IN THREE SPECIES OF THE DIATOM NITZSCHIA1

The relationship of cell organelles to valve morphogenesis was investigated in three species of Nitzschia. One, N. sigmoidea (Nitzsch) W. Sm., showed consistent ability to generate both nitzschioid and hantzschioid symmetry in daughter cells following cytokinesis; the other two maintained nitzschioid symmetry stably. From previous work with Hantzschia, a certain sequence of events could be anticipated in the cytoplasm. In two significant areas–the behavior of the Microtubule Center (MC) and its microtubule (MT) system, and the central origin of the silicalemma–not only were the results unexpected, but the three species showed fundamental differences among themselves. In N. sigmoidea, the silicalemma (and the future raphe region) arises centrally on the cleavage furrow, and after some lateral expansion, the silicalemmas and their associated organelles move in opposite directions in daughter cells, so that the raphe and the raphe canals end up along the girdle side of the cell as expected. However, the MCs never become associated with their silicalemma, remaining throughout near the girdle bands. In N. sigma (Kütz) W. Sm., the silicalemmas arise centrally and after lateral growth, move in opposite directions to generate nitzschioid symmetry. In this case, the MCs move to the vicinity of but never close to the silicalemmas, and follow them distantly during their lateral movement. In N. tryblionella Hantzsch, the new silicalemmas arise opposite one another, on one side of the daughter cells; each MC soon moves very close to its silicalemma, and remains thus through most of valve morphogenesis. Later, only one silicalemma/MC complex moves laterally, establishing the nitzschioid symmetry in both daughter cells. In all three species, as in Hantzschia, linear arrays of mitochondria aligned along MTs occupy the forming raphe canal, and microfilaments line the outer edge of the expanding silicalemma. The fibulae (the wall struts arching across the raphe canal) in Hantzschia always grow from the valve surface to the girdle surface of the forming valves. In these three Nitzschiae, this invariably happens in only one daughter cell of any pair; in the other, all the fibulae grow from the girdle surface to the valve surface. An explanation of these variations is proposed: that the morphogenetic machinery of Nitzschia and Hantzschia have a common origin, with present Nitzschiae having undergone considerable diversification at the intracellular level, causing the unstable cell symmetry exhibited by several modern species. Perhaps a taxonomic distinction between Hantzschia and Nitzschia lies in whether the morphogenetic machinery associated with valve morphogenesis moves laterally in the same or in opposite directions.     

VARIATION IN PATTERNS OF VALVE MORPHOGENESIS BETWEEN REPRESENTATIVES OF SIX BIRAPHID DIATOM GENERA (BACILLARIOPHYCEAE)

Scanning electron microscopic studies of silica valve formation in naviculoid diatoms representing six different genera revealed that the precise sequence of depositional events varied among genera. Valve deposition begins with the formation of the raphe sternum, from which virgae (lateral outgrowths) extend. Areolae (pores) are formed between the virgae by the fusion of cross-extensions (vimines). In most of the species studied ( Craticula ambigua (Kützing) D. G. Mann, Frustulia vulgaris (Thwaites) De Toni, Craspedostauros australis E. J. Cox, and Gomphonema truncatum Ehrenberg), areola (pore) formation began near the raphe sternum before completion of the valve margin, but in Pinnularia gibba Ehrenberg the valve margin fused before the areolae were formed. Silica deposition in all these taxa was mainly distal to proximal (with respect to the cytoplasm), but in Haslea sp. it was mainly proximal to distal. Haslea also differed in that areolae were defined as the valve margin was completed. These data have also contributed to the interpretation of taxonomically important features, such as raphe endings. In P. gibba the internal central raphe fissures were laterally deflected but subsequently obscured by additional silicification of the valve, whereas in G. truncatum they were initially straight, becoming laterally deflected as valves mature. External raphe fissures in Frustulia became Y-shaped only just before maturity; in immature valves they were dotlike, as in Amphipleura Kützing. The comparison of developmental pathways in diatoms is a useful adjunct to morphological and other approaches in diatom systematics and warrants renewed attention.     

MUCILAGE TUBE MORPHOLOGY OF THREE TUBE-DWELLING DIATOMS AND ITS DIAGNOSTIC VALUE1

Colonies of Berkeleya rutilans (Trent.) Grun., Navicula pseudocomoides Hendey and N. ramosissima (C. A. Ag.) Cleve were examined using light and electron microscopy to elucidate the structure of their mucilage tubes. Each species was found to have a characteristic tube construction which could be used for identification. A summary of features on which these species can be recognized was compiled.     

BIOCHEMICAL TAXONOMY OF MARINE PHYTOPLANKTON BY ELECTROPHORESIS OF ENZYMES. I. THE CENTRIC DIATOMS THALASSIOSIRA PSEUDONANA AND T. FLUVIATILIS1,2

Diatom systematics depends almost entirely upon structure of the silica shell. It is not known to what extent the taxonomic species, as defined by shell structure, corresponds to the genetic species—i.e., to the reproductively isolated population. As an approach to this problem, we report here a comparison of enzymes by electrophoresis. We have examined the genetic constitution of a number of clones of (presumably) the same species for each of 2 closely related, centric diatom species: Thalassiosira pseudonana Hasle and Heimdal and T. fluviatilis Hustedt. The 4 clones of T. fluviatilis form a distinct group, clearly separated from all the T. pseudonana clones. Within T. pseudonana, 4 estuarine clones and one reef clone form a group that is distinctly different from 4 oceanic clones. A single clone of T. pseudonana from the Continental Slope waters is intermediate between these 2 groups and probably shares genes with both groups, indicating that the 2 T. pseudonana groups are not genetically isolated. We conclude that i) within groups, isolates are closely related even though they originated from different continents; and, ii) T. pseudonana is subdivided into ecological races.     

STRUCTURE,LIFE HISTORY AND SYSTEMATICS OF RHOICOSPHENIA (BACILLARIOPHYTA). IV. CORRELATION OF SIZE REDUCTION WITH CHANGES IN VALVE MORPHOLOGY OF RH. GENUFLEXA1

Rhoicosphenia Grun. is a relatively isolated genus among the biraphid diatoms. Morphological changes in an isopolar member of the genus, Rh. genuflexa (Kütz.) Medlin, were investigated using light and scanning electron microscopy. The fully raphid valve showed changes in its flexure that could be correlated with size reduction during its life history from the initial cells to the smallest cells found in the population. Bands showed changes in number (from three to one) related to size reduction. Rh. genuflexa is morphologically similar to Rh. abbreviata (C. Ag.) Lange-Bert. (=Rh. curvata (Kütz.) Grun.), although the two are distinct taxa. These observations support previous contentions that Rhoicosphenia is a natural taxonomic grouping.     

BIOCHEMICAL TAXONOMY OF MARINE PHYTOPLANKTON BY ELECTROPHORESIS OF ENZYMES. II. LOSS OF HETEROZYGOSITY IN CLONAL CULTURES OF THE CENTRIC DIATOMS SKELETONEMA COSTATUM AND THALASSIOSIRA PSEUDONANA1, 2

An electrophoretic survey of 12 new isolates of Thalassiosira pseudonana Hasle & Heimdal and 25 new isolates of Skeletonema costatum (Grev.) Cleve revealed several heterozygote genotypes at malate dehydrogenase (MDH) and phosphohexose isomerase (PHI) loci. The new clones were maintained in culture for 6 mo and then reasayed at these two loci. All MDH heterozygotes and halj of the PHI heterozygotes had become homozygous. This resulted in a collection of clones that are largely homozygous but that are samples of polymorphic species. The physlogical implications of this loss of heterozygosity in clonal cultures has not been analyzed. Hawever, any change in a clone that is the result of culturing conditions reduces the usefulness of that clone as a laboratory test organism for ecological correlations.     

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.     

人胎儿肝内甲胎蛋白的成份及其对T.B淋巴细胞发育的影响

本文用免疫组织化学方法,分别在冰冻和石蜡切片上,对24例不同胎龄的胎儿肝比较研究了肝内 AFP~+细胞数量及其与 T,B 淋巴细胞之间的关系。结果发现 AFP 仅分布于肝细胞内,其他细胞阴性。不同胎龄的肝脏,AFP 的染色强度和阳性率不同。17周前的胎肝,AFP~+细胞最多以后逐渐减少。出生前的肝脏内只有少数 AFP~+细胞。AFP~+细胞的多少与 B 细胞分化发育无多大关系,但与 T 细胞似乎关系密切,两者呈负相关,即 AFP~+细胞多时,T 细胞很少,AFP~+减少时,T 细胞增加,提示 AFP 对 T 细胞具有抑制作用。同时也证明 B 细胞在胎肝内受 T 细胞的影响不大,主要依赖于肝脏的微环境。另外对 AFP 的生物学意义也进行了讨论。     

DIATOM MINERALIZATION OF SILICIC ACID. VII. INFLUENCE OF MICROTUBULE DRUGS ON SYMMETRY AND PATTERN FORMATION IN VALVES OF NAVICULA SAPROPHILA DURING MORPHOGENESIS1

Microtubule involvement in diatom valve symmetry and pattern formation was investigated using cells synchronized subsequent to mitosis and cytokinesis but prior to cell wall formation. Two analog drug pairs, each consisting of an active and an inactive microtubule drug, were used to distinguish inhibitory effects related or unrelated to microtubule disruption. The active anti-microtubule drug of each analog pair produced significantly higher percentages of aberrant valves than did the respective inactive analogs. High frequencies of aberrant valves also were caused by N-isophenlpropylcarbamate, which disorganizes rather than disrupts microtubules. Valves could be placed into different classes based upon characteristic aberrations. Formation of these classes was not random but was instead a function of both the drug and the drug concentration. The central nodule and the raphe were the principal valve components affected by anti-microtubule drugs. Stria alterations appeared as a secondary result of alterations in the central nodule/raphe. Valve aberrations occurred at very low drug concentrations in the range 1 × 10^?6 to 1 × 10^?9M.     

THE MORPHOLOGY AND DEVELOPMENT OF SOME PROMINENTLY STALKED SOUTHERN AUSTRALIAN HALYMENIACEAE (CRYPTONEMIALES,RHODOPHYTA). I. CRYPTONEMIA KALLYMENIOIDES (HARVEY) KRAFT COMB. NOV. AND C. UNDULATA SONDER1

Several southern Australian red algae of the family Halymeniaceae (Cryptonemiales) are differentiated into hard, massive stalks and considerably softer laminar blades or phyllodes. The taxonomy, morphology and pit-connection ultrastructure of one such species, Cryptonemia kallymenioides (Harvey) Kraft comb. nov., are compared to C. undulata Sonder, which lacks massive stalks. In both species there is extensive periodic secondary cortication of the stalks, resulting in the formation of distinct “growth rings.” The blades of C. kallymenioides appear to be seasonal and its stalks perennial, while plants of C. undulata are apparently perennial but shorter lived than C. kallymenioides. As a result, stalks in the latter can reach 2–3 cm in diameter with up to 18 growth rings, compared to the 1–2 mm diameters and up to 6 rings within the stalks of C. undulata. Heavy secondary thickening of cortical cell walls occurs in both species and confers a “woody” texture to the stalks of C. kallymeniodes. Regardless of the large differences in average stalk diameters between the two species, the pit-connection ultrastructure from cortex to medulla shows much the same sequence of morphological modification. Pit-connections are standard red algal structures in the outer cortex, but become increasingly convoluted on the membrane-bound surfaces abutting cytoplasm and develop wider apertures and less dense cores with increasing distance from the stalk surface. In occasional medullary cells of C. kallymenioides, the cytoplasm disintegrates, leaving cell walls and pit-connections to play an apparently structural role which has not been reported in other red algae. It is suggested that the increase in aperture size and surface areas of pit-connections is compatible with their playing a role in the intercellular transport of solutes towards the inner cell layers which may, in C. kallymenioides, lie many millimeters distant.     

MONOCLONAL ANTIBODIES AS MOLECULAR MARKERS FOR THE INTRACELLULAR AND CELL WALL DISTRIBUTION OF CARRAGEENAN EPITOPES IN KAPPAPHYCUS (RHODOPHYTA) DURING TISSUE DEVELOPMENT1

Carrageenan, the major cell wall carbohydrate of certain red algae, is variable in structure and gelling properties. Sequence types include gelling (kappa and iota) and nongelling (lambda) types in addition to precursors, often in hybrid molecules containing more than one precursor and/or sequence type. Molecular markers to subunits were needed to study carrageenan synthesis, cell wall organization, and the relationship between structure and function. Monoclonal antibodies were produced to carrageenan, and their specificities were determined by competitive enzyme immunoassay. Antibodies were identified with specificities related to kappa, iota, and lambda carrageenan. The patterns of immunofluorescence localization on Kappaphycus alvarezii = Eucheuma alvarezii var. tambalang (Doty) sections were distinctive for each antibody. The antibody to a kappa-related epitope labeled mature tissue strongly; antibodies to an iota-related epitope and a lambda-related epitope labeled weakly, consistent with the kappa-enriched carrageenan produced by this alga. Kappa-related epitopes were distributed throughout the wall and matrix, whereas iota-related epitopes were concentrated in the middle lamella. Lambda-related epitopes were localized primarily at the plant cuticle where kappa and iota antigens were lacking. An antibody appeared to be specific for a precursor of the gelling subunits because it showed maximal wall and intracellular labeling at the youngest developmental stage. All antibodies labeled intracellular inclusions in the transition zone between the epidermis and medulla during the development of medullary cells from the peripheral meristem in young branches. The results demonstrate the intracellular synthesis of epitopes related to all major carrageenan subunits and their differential extracellular distribution.     

DEVELOPMENTAL STUDIES IN PORPHYRA (RHODOPHYCEAE). III. EFFECT OF CULTURE CONDITIONS ON WALL REGENERATION AND DIFFERENTIATION OF PROTOPLASTS1

Protoplasts isolated from thalli of four Porphyra species regenerated successfully into differentiated plantlets. The efficiency of protoplast isolation and the developmental patterns of the regenerating protoplasts depended on the type of tissues from which they were isolated. However, culture conditions greatly influenced the patterns of development at the cellular and organismal levels. Sorbitol, nitrogen, and agar concentration in the medium controlled rates of cell division, thickening of cell walls, development of rhizoids, and formation of calluses or differentiated blades. Agitation disturbed the attachment of the protoplasts to a substrate. Cells in agitated cultures produced suspensions of single cells and non-polarized small calluses. Calluses which developed from protoplasts survived in storage for over two years. The stored calluses, and cells and protoplasts that were isolated from them, were subcultured successfully. We forsee extensive use of Porphyra cell suspensions for strain selection and vegetative propagation of cultivars. This technology, which makes vegetative cloning of selected Porphyra plants possible, may eliminate the need for cultivation and storage of the conchocelis phase. Protoplasts are also being used as tools for studies in genetic engineering of these commercial species.     

THE FUCUS (PHAEOPHYCEAE) SPERM RECEPTOR FOR EGGS. I. DEVELOPMENT AND CHARACTERISTICS OF A BINDING ASSAY1

To explore the molecular basis of egg-sperm recognition in the brown alga , Fucus serratus L., we developed an in vitro binding assay involving egg plasma membrane vesicles (PMVs) and proteins contained in a KCl extract of sperm. Binding between the two components was measured using biotinylated PMVs followed by the addition of streptavidin conjugated to alkaline phosphatase and the appropriate substrate. Biotinylation did not affect the ability of egg PMVs to inhibit fertilization in a species-preferential manner. Binding of labeled egg PMVs to the sperm KCl extract was saturable and competable with unlabeled PMVs but was not species-specific. Protease treatment of the KCl extract abolished binding, whereas periodate had no effect, suggesting that sperm protein rather than carbohydrate was involved. Preincubation of the sperm extract with sulfated polysaccharides (e.g. fucoidan and ascophyllan) inhibited binding of egg plasma membranes. Sulfation seems to be important for this effect since desulfated fucoidan was far less effective at blocking binding. Polysaccharides which inhibited binding also inhibited fertilization. Overall, the results indicate that at least some aspects of binding between Fucus sperm and eggs are mediated by a protein(s) derived from sperm which recognizes sulfated glycoconjugates on the egg plasma membrane .