Cloning and Characterization of the Ribosomal Protein Genes in the spc Operon of a Prokaryotic Endosymbiont of the Pea Aphid, Acyrthosiphon kondoi

To correlate a prokaryotic endosymbiont in the pea aphid, Acyrthosiphonkondoi, with the endosymbionts in related aphid species as wellas with free-living bacteria and subcellular organelles, andto study the mode of its gene expression within aphid cells,we have cloned and characterized the genes encoding ribosomalproteins S3, L16, L29, S17, L14, L24, L5, S14, S8, L6, L18,S5, L30, L15 and secretion protein Y (Sec Y) from the S10 andspc ribosomal protein gene operons of this endosymbiont. Theorganization of these genes is identical to that in Escherichiacoli, and their nucleotide sequences are highly similar (87%identity) to the corresponding E. coli genes. They are muchless similar to the corresponding chloroplast and mitochondrialgenes. The guanine plus cytosine G+C content of the genes ofthe A. kondoi endosymbiont is much higher than those of theendosymbionts in related aphid species reported so far. It appearseither that the A. kondoi endosymbiont is derived from an ancestralbacterium different from those in other aphids or that its G+Ccontent increased in a relatively short time after the evolutionarydivergence of its host.     

The seasonal distribution of the marine diatom genus Chaetoceros Ehr. in Narragansett Bay, Rhode Island (1981-1982)

The seasonal dynamics of the diatom genus Chaetoceros Ehrenbergwere investigated in Narragansett Bay, Rhode Island. Whole watersamples were collected weekly from July 1981 to October 1982at four locations in the lower Bay and were preserved, concentratedby settling and enumerated. Chaetoceros were most abundant inlate winter–early spring; a second peak occurred in thefall. As in many other temperate neritic areas, C. debilis,C. compressus and C. didymus were major components of die Chaetocerospopulation and could be found throughout the year. Species compositionand dynamics were quite similar at the Jerusalem, GSO Pier andWickford Harbor stations, but were markedly different in PettaquamscuttRiver, a reduced salinity tidal estuary.     

Structure of the dnaA region of the endosymbiont, Buchnera aphidicola, of aphid Schizaphis graminum

Buchnera aphidicola is an intracellular prokaryote (endosymbiont)that lives in the body cavity of the aphid. Phylogenetic studiesindicated that it is closely related to Escherichia coli andmembers of Enterobacteria. The gene order of the region containingthe dnaA gene is well conserved in many bacteria. Seven genesof the endosymbiont of the aphid Schizaphis graminum, gyrB,dnaN, dnaA, rpmH, rnpA, yidD, and 60K, were found to be homologousin sequence and relative location to those of E. coli. We havefurther sequenced the region downstream of the 60K gene to elucidatethe boundary of the conserved region, and found that one moregene, thdF , is conserved. The comparison of gene organizationsof the dnaA region of the related bacteria supported the closephylogenetic relationship of B. aphidicola to E. coli. In addition,we have identified groES and groEL genesnext to the thdF gene.GroEL protein was reported to be expressed at an elevated levelin the endosymbionts of aphids, and is considered to play animportant role in their association with the aphid host. Comparisonof the structure of the groE operon with that of the endosymbiontof the aphid Acyrthosiphon pisum revealed the conservation ofa sequence resembling the E. coli consensus heat shock promoter,and this sequence may be responsible for the high expressionof the groEL gene in aphid endosymbionts.     

OCCURRENCE OF RICHELIA INTACELLULARIS (CYANOPHYTA)WITHIN THE DIATOMMMS HEMIAULUS HAUKII ADN H. MEMBRANACEUS OFF HAWAII1

The presence of nitrogen–Fixing cyanobacterial endophytes, such as Richelia intracellularis Schmidit commonly observed within several species of Rhizosolenia, in nitrogen-limited oceanic waters has obvious implications both for the host organism(s) and for the entire planktonic assemblage. Recently, epi-fluorescent examination of pllankton samples collected off Oahu, Hawaii, in september 1982 revealed R. intracellularis within the diatoms Hemiaulus membranaceus Cleve and H. hauckii Grunow as well as its expected presence within Rhizosolennia spp. Richelia intracellularis coccurred with within Hemiaulus spp. at frequenccies (ca.80%)comparable to those noted for Rhizosolenia spp. Standard bright field or phaseconrast microsocopy could not reliably distinguish the cyanobacteria within Hemiaulus spp. If this association is common, the occurrence of R.intracellularis (and its significance in the nitrogen dynamics of the ocean)may have been greatly underestimated in previous studies.     

The first-stage zoeas of Carpilius convexus (Forskal, 1775) and Carpilius maculatus (Linnaeus, 1758) (Crustacea: Decapoda: Brachyura: Xanthoidea: Carpiliidae): an example of heterochrony

The first-stage zoeas of Carpilius convexus (Forskål,1775) and Carpilius maculatus (Linnaeus, 1758) are describedand fully illustrated. Both these Indo-West Pacific speciesexhibited a unique xanthoidean character for the basis of thesecond maxilliped, which possesses five (arranged 1,1,1,2) setaeinstead of the expected four (arranged 1,1,1,1). A comparisonwith the zoeal stages of Carpilius corallinus (Herbst, 1783)as reported by Laughlin et al. (Laughlin et al., 1983) revealedmarked differences including the possession of carapace lateralspines (v. absent in C. convexus only), the subterminal setationof the distal maxillule endopod segment with two subterminalsetae (versus one subterminal seta in Indo-West Pacific species),the terminal setation of the distal maxillule endopod segmentwith four setae (versus three setae in C. convexus only), twolateral spines on the telson (versus three in Indo-West Pacificspecies) and the number of zoeal stages. The first-stage zoeasof the two Indo-West Pacific species appear to have hatchedin a more advanced state of development than those of C. corallinus,and the expression of a number of characters has been accelerated(early onset). In fact, the zoeal stages of both Indo-West Pacificspecies and carpiliid species appear to be abbreviated becausethe first zoeas are considered to be equivalent to the third-stagezoeas of C. corallinus.     

PHYLOGENY OF THE GENUS ROSTANGA (NUDIBRANCHIA), WITH DESCRIPTIONS OF THREE NEW SPECIES FROM SOUTH AFRICA

Rostanga elandsia sp. nov., Rostanga aureamala sp. nov. andRostanga phepha sp. nov. are characterized by having the radulawith slender innermost lateral teeth, which lack denticles onthe inner side of the cusp and have a single denticle on theouter side. The outermost lateral teeth of these three speciesare elongate, but shorter than in other species of the genus.In addition, R. aureamala is the only species of the genus withrachidian teeth and R. phepha is unique within the genus Rostanga byvirtue of its white coloration with dark spots. A phylogenetic analysis shows that the three new species fromSouth Africa and Rostanga setidens (Odhner, 1939) are the sistergroup of the rest of the genus. The species from Japan and MarshallIslands (North Pacific Ocean) are basal in the sister cladecontaining the other species of Rostanga Bergh, 1879. The tropicalIndo-Pacific species of Rostanga are not monophyletic. The Atlanticand Eastern Pacific species form a monophyletic, derived clade,being the sister group of Rostanga australis Rudman & Avern,1989, which has a narrow range restricted to south eastern Australia.The widespread Indo-Pacific species Rostanga bifurcata Rudman& Avern, 1989, is the sister group of Rostanga dentacus Rudman& Avern, 1989, also widesprad in the tropical western Pacific. This phylogeny suggest s a viariant origin of the Sourth African, Atlantic-EasternPacific, and probably North Pacific species, whereas in thetropical Indo-Pacific most sister speceis are sympatric. (Received 16 May 1999; accepted 31 July 2000)     

Novel Chemoautotrophic Endosymbiosis between a Member of the Epsilonproteobacteria and the Hydrothermal-Vent Gastropod Alviniconcha aff. hessleri (Gastropoda: Provannidae) from the Indian Ocean

The hydrothermal-vent gastropod Alviniconcha aff. hessleri from the Kairei hydrothermal field on the Central Indian Ridge houses bacterium-like cells internally in its greatly enlarged gill. A single 16S rRNA gene sequence was obtained from the DNA extract of the gill, and phylogenetic analysis placed the source organism within a lineage of the epsilon subdivision of the Proteobacteria. Fluorescence in situ hybridization analysis with an oligonucleotide probe targeting the specific epsilonproteobacterial subgroup showed the bacterium densely colonizing the gill filaments. Carbon isotopic homogeneity among the gastropod tissue parts, regardless of the abundance of the endosymbiont cells, suggests that the carbon isotopic composition of the endosymbiont biomass is approximately the same as that of the gastropod. Compound-specific carbon isotopic analysis revealed that fatty acids from the gastropod tissues are all ¹³C enriched relative to the gastropod biomass and that the monounsaturated C₁₆ fatty acid that originates from the endosymbiont is as ¹³C enriched relative to the gastropod biomass as that of the epsilonproteobacterial cultures grown under chemoautotrophic conditions. This fractionation pattern is most likely due to chemoautotrophy based on the reductive tricarboxylic-acid (rTCA) cycle and subsequent fatty acid biosynthesis from ¹³C-enriched acetyl coenzyme A. Enzymatic characterization revealed evident activity of several key enzymes of the rTCA cycle, as well as the absence of ribulose-1,5-bisphosphate carboxylase/oxygenase activity in the gill tissue. The results from anatomic, molecular phylogenetic, bulk and compound-specific carbon isotopic, and enzymatic analyses all support the inference that a novel nutritional strategy relying on chemoautotrophy in the epsilonproteobacterial endosymbiont is utilized by the hydrothermal-vent gastropod from the Indian Ocean. The discrepancies between the data of the present study and those of previous ones for Alviniconcha gastropods from the Pacific Ocean imply that at least two lineages of chemoautotrophic bacteria, phylogenetically distinct at the subdivision level, occur as the primary endosymbiont in one host animal type.     

Roles of the endosymbiont and leishmanolysin-like molecules expressed by Crithidia deanei in the interaction with mammalian fibroblasts

Crithidia deanei is an insect trypanosomatid that harbors a bacterial endosymbiont in its cytoplasm. In this work, we have demonstrated the influence of the endosymbiont on the interaction of C. deanei with mammalian fibroblasts, also implicating the surface leishmanolysin-like molecules of C. deanei in this process. The wild strain of C. deanei expressed a higher amount (2-fold) of leishmanolysin-like molecules in the parasite surface than the aposymbiotic strain. The treatment of parasites with anti-leishmanolysin antibodies or the fibroblasts with purified leishmanolysin-like molecules from C. deanei significantly reduced the association index. The aposymbiotic strain of C. deanei presented interaction rates about 2- and 3-fold lower with fibroblasts than the endosymbiont-bearing counterpart after 1 and 2 h, respectively. However, the association indexes were similar after 3 and 4 h of interaction. Additionally, we observed a 2-fold increase in the association index after 24-96 h of parasite-fibroblast interaction when compared to the interaction process performed for 4 h, irrespective to the presence of the endosymbiont, suggesting that fibroblasts support multiplication and survival of C. deanei. Both parasite strains were able to induce fibroblast lysis. Interestingly, the wild strain led to a 2-fold increase in fibroblasts death in comparison to the aposymbiotic strain after 48-96 h. We also showed that both wild and aposymbiotic biotinylated live parasites recognized the same receptor in the fibroblast cells.     

EASTERN MEDITERRANEAN OPISTHOBRANCHIA: RUNCINIDAE (RUNCINACEA), WITH A REVIEW OF RUNCINID CLASSIFICATION AND A DESCRIPTION OF A NEW SPECIES FROM FIJI

An account is given of the runcinaceans Runcina adriatica, R.brenkoae and R. zavodniki collected on diving expeditions inthe northern Adriatic Sea. The new data permit a clear separationof these from other runcinaceans of the north Atlantic Ocean.Several diagnostic features of the radulae and the oral cuticu-lararmature are corrected or amplified. Dental metamorphoses aredescribed for R. adriadca and R. zavodniki. The world's runcinaceanfamilies, genera and species are reviewed, and Runcina fijiensisn.sp. is described from the Pacific island of Viti Levu, Fiji (Received 14 December 1987; accepted 7 January 1988)     

Tobacco Nuclear Genes for Photosystem I Subunits, psaD, psaE and psaH Share an Octamer Motif Bound with Nuclear Proteins

In Nicotiana sylvestris, nuclear-encoded photosystem I (PSI)genes, psaD, psaE and psaH, share an octamer motif bound withthree phosphoproteins. This motif is not found in the chloroplastgenome. From the view point of endosymbiont hypothesis, theseresults suggest that a set of ancient PSI genes acquired a commoncis-element in the nucleus after they were transferred fromthe ancestral organelle. (Received March 20, 1995; Accepted August 9, 1995)     

Effects of Atmospheric NO2 on Azolla-Anabaena Symbiosis

Cultures of the water fern Azolla pinnata R, Br. exposed for1 week to atmospheric NO₂ (50, 100 or 200 nl l^-1) induced additionallevels of nitrate reductase (NaR) protein and nitrite reductase(NiR) activity. At low concentrations of NO₂ (50 nl l^-1), nitratederived from NO₂ provides an alternative N source for Azollabut does not affect rates of acetylene reduction. However, thesymbiotic relationship between Azolla and its endosymbiont,Anabaena azollae is only affected adversely by high concentrations(100 and 200 nl l^-1) of atmospheric NO₂. The resultant decreasesin rate of growth, nitrogen fixation, heterocyst formation,and overall nitrogen cycling are probably due to the additionalaccumulation of N products derived from higher levels of atmosphericNO₂. Parallel increases in levels of polyamines suggest thatAzolla partially alleviates these harmful effects by incorporatingsome of the extra NO₂-induced N into polyamines.Copyright 1994,1999 Academic Press Azolla-Anabaena symbiosis, nitrogen dioxide pollution, nitrogen metabolism, polyamines     

Early Pleistocene glacial-interglacial radiolarian assemblages from the eastern equatorial Pacific

Polycystine radiolaria from ODP Hole 677A in the eastern equatorialPacific were examined at isotopically identified Early Pleistoceneglacial maxima and minima. Two distinct radiolarian assemblagesare recognized, characterizing glacial and interglacial optima.The Glacial Assemblage is characterized by high abundances ofTheocalyptra davisiana, Botryostrobus auritus, Anthocyrtidiumzanguebaricuim andHexacontium enthacanthum. The InterglacialAssemblage is characterized by Tetrapyle octacantha, Octapylestenozoa and Theocorythium vetulum. A comparison of these fossilassemblages with modern radiolarian distribution suggests thatthe Glacial Assemblage represents intensified upwelling of coldadvected water via the Eastern Pacific Boundary Current, whilstthe Interglacial Assemblage indicates climatic ameliorationin the eastern equatorial Pacific, with the prevalence of warm(>21C) tropical/subtropical surface waters. The recognitionof these radiolarian assemblages could be successfully appliedto studies of adjacent east Pacific areas where other palaeoecologicalindicators are lacking.     

An endosymbiotic bacterium in a plant-parasitic nematode: Member of a new Wolbachia supergroup

Wolbachia is an endosymbiotic bacterium widely present in arthropods and animal-parasitic nematodes. Despite previous efforts, it has never been identified in plant-parasitic nematodes. Random sequencing of genes expressed by the burrowing nematode Radopholus similis resulted in several sequences with similarity to Wolbachia genes. The presence of a Wolbachia-like endosymbiont in this plant-parasitic nematode was investigated using both morphological and molecular approaches. Transmission electron microscopy, fluorescent immunolocalisation and staining with DAPI confirmed the presence of the endosymbiont within the reproductive tract of female adults.16S rDNA, ftsZ and groEL gene sequences showed that the endosymbiont of R. similis is distantly related to the known Wolbachia supergroups. Finally, based on our initial success in finding sequences of this endosymbiont by screening an expressed sequence tag (EST) dataset, all nematode ESTs were mined for Wolbachia-like sequences. Although the retained sequences belonged to six different nematode species, R. similis was the only plant-parasitic nematode with traces of Wolbachia. Based on our phylogenetic study and the current literature we designate the endosymbiont of R. similis to a new supergroup (supergroup I) rather than considering it as a new species. Although its role remains unknown, the endosymbiont was found in all individuals tested, pointing towards an essential function of the bacteria.     

SUBSPECIATION IN TWO SPECIES OF CYPRAEIDAE

SELECTED dimensions have been measured on 307 specimens of C.caputserpentis L. and C. capuldraconis Melvill. Analysis ofthe results shows three groups which merit taxonomic distinction.They are : C. caputserpentis caputserpentis L. Indian and Pacific Oceans. C. c. capulophidii (Schilder) Hawaiian Is. C. capuldraconis Melvill Easter I. (Received 14 November 1958;     

Cospeciation Between the Primary Endosymbionts of Mealybugs and Their Hosts

Mealybugs have an association with prokaryotic endosymbionts that are located in specialized cells called bacteriocytes. In order to compare the phylogeny of the host with that of the previously published phylogeny of the endosymbionts, 3.1 to 3.2 kilobase DNA fragments containing mitochondrial cytB (part), nd1,16S ribosomal DNA(rDNA), and 12S rDNA (part) were amplified and sequenced. A phylogenetic analysis of the data and a comparison with the trees obtained from endosymbiont genes and host 18S and 28S rDNA indicated that all the trees were similar. This result is consistent with an infection of a mealybug ancestor with a precursor of the endosymbiont followed by the vertical transmission of the endosymbiont to progeny. Comparison of the guanine + cytosine (G + C) contents of the mealybug mitochondrial genes with the same genes from other members of Sternorrhyncha and Arthropoda indicated that the mealybug genes had unusually low G + C contents in their DNAs (10.2 to 11.1 mol%).     

Recent bivalve molluscs of the genus Calyptogena (Vesicomyidae)

The genus Calyptogena (Bivalvia: Vesicomyidae) comprises highlyspecialized bivalves living in symbiosis with sulphur-oxidizingbacteria in reducing habitats. In this study, the genus is revisedusing shell and anatomical features. The work is based on typematerial, as well as on the extensive collection of vesicomyidsobtained during twelve expeditions to the Pacific and IndianOceans. Nine Recent species are ascribed to the genus Calyptogena,four of which are new: C. pacifica Dall, 1891, C. fausta Okutani,Fujikura & Hashimoto, 1993, C. rectimargo Scarlato, 1981,C. valdiviae (Thiele & Jaeckel, 1931), C. gallardoi Sellanes& Krylova, 2005, C. goffrediae n. sp., C. starobogatovin. sp., C. makranensis n. sp. and C. costaricana n. sp. Thecharacteristic features of Calyptogena are: shell up to 90 mmin length, elongate-elliptical or elongate; presence of escutcheon;presence of broad posterior ramus (3b) of right subumbonal cardinaltooth as well as right posterior nymphal ridge; absence of pallialsinus as a result of attachment of intersiphonal septal retractorimmediately adjacent to ventral surface of posterior adductor;absence of processes on inner vulva of inhalant siphon; presenceof inner demibranch only, with descending and ascending lamellaewith interlamellar septa not divided into separate tubes. Themost closely related taxa to Calyptogena are probably the genusIsorropodon Sturany, 1896, and the group of species representedby ‘Calyptogena’ phaseoliformis Métivier,Okutani & Ohta, 1986. These groups have several charactersin common, namely absence of pallial sinus, presence of singleinner pair of demibranchs and absence of processes on innervulva of inhalant siphon. The worldwide distribution of thegenus Calyptogena suggests that methane seeps at continentalmargins are the major dispersal routes and that speciation waspromoted by geographical isolation. Recent species diversityand fossil records indicate that the genus originated in thePacific Ocean. Sufficient data to discuss the distribution atspecies level exist only for C. pacifica, which has a remarkablynarrow bathymetric range. Published studies on the physiologyof C. pacifica suggest that adaptation to a specific geochemicalenvironment has led to coexisting vesicomyid genera. The bacteria-containinggill of C. pacifica and other Calyptogena species is one ofthe most specialized in the family Vesicomyidae and may reflectthese ecological adaptations. (Received 23 December 2005; accepted 3 April 2006)     

The presence of chlorophyll b and the estimation of phaeopigments in marine phytoplankton

A reverse-phase h.p.l.c. technique was used to estimate theconcentration of chlorophyll b in phytoplankton cultures, fecalpellets of Calanus pacificus, and suspended paniculate matterfrom the Central North Pacific, Oregon coastal waters, and DabobBay (a temperate fjord in Puget Sound, WA, USA). The purposewas to assess the distribution of this pigment in the euphoticzone and its effect on the fluorometnc estimation of phaeopigments.Analyses of natural waters confirm high chlorophyll b concentrations(median mass ratio of b:a > 0.3) at the depth of the chlorophylla maximum in tropical waters while values for temperate planktonare relatively low (median mass ratio of chl b:a = 0.05) andpatchy. Zooplankton fecal pellets showed a significant enrichmentin chlorophyll b, suggesting grazing as a mechanism to explainhigh concentrations of this pigment at the bottom of the euphoticzone. It is estimated that the presence of chlorophyll b couldcause an average overestimation of phaeopigment concentrationby the fluorometnc technique of 38% between 0 and 200 m in theCentral North Pacific. This effect is more pronounced at thelayer of chlorophyll b maximum (120–140 m). ¹Present address: Marine Biology Research Division, A-002, ScrippsInstitution of Oceanography, La Jolla, CA 92093, USA     

Vertical migration of Rhizosolenia mats and their significance to NO3- fluxes in the central North Pacific gyre

Rhizosolenia mat abundance, distribution and chemical compositionwere studied on two cruises in the central North Pacific gyrein order to determine large-scale distribution patterns andcontribution to upward nitrogen (N) flux. These macroscopicdiatom mats are composed of multiple species of Rhizosoleniathat exploit subsurface nitrate pools by vertically migratingbelow the euphotic zone. Although numerically dominated by thesmall-diameter species, R.fallax (73–95% of total numbers),mat biovolume was dominated by large-diameter (>50 µmdiameter) Rhizosolenia spp. (85–99% of total volume).Integrated mat abundance was substantially higher when matsaccumulated at the surface during calm weather (     

Antitranspirant-induced Heat Stress in the Parasitic Plant Striga hermonthica--A Novel Method of Control

Leaf temperatures (T₁) of the parasitic plant Striga hermonthicaare substantially below those of the air (T_a), [T_a–T₁]reaching 7 ?C at T_a = 40 ?C. This results from high rates oftranspiration and the consequent evaporative cooling of theleaf. Application of an antitranspirant, which mechanicallyimpedes foliar loss of water vapour, reduced transpiration andstomatal conductance by 40% and 57%, respectively, and reduced[T_a– T₁] to 2 ?C at T_a = 40 ?C. The temperature sensitivityof photosynthesis in the host-parasite association differed,the optima (T_opt) being 37.2 and 40.1 ?C for S. hermonthicaand sorghum, respectively. Once Topt had been exceeded in S.hermonthica net photosynthesis declined rapidly, reaching thelethal limit (Tmax) at 42.6 ?C. S. hermonthica is particularlysensitive to high temperatures and antitranspirant-induced overheatingleads to blackening and shrivelling of the leaf after as littleas 4 h at T_a = 40 ?C. Application of an antitranspirant underfield conditions in the Sudan at T_a = 40 ?C resulted in 28%and 67% reductions in transpiration and stomatal conductance,together with a 5 ?C increase in T₁, and subsequent leaf death.In addition to these short-term physiological responses, antitranspirantspraying of the arasite increased the grain and straw yieldof the crop by factors of 3.4 and 2.6, respectively. Antitranspirantsmay have potential use as a method of controlling Striga inthe field. Key words: Striga hermonthica, sorghum, photosynthesis, transpiration, high temperature stress, anti-transpirant     

Evaluation of nitrogen fixation in the diatom genus Rhizosolenia Ehr. in the absence of its cyanobacterial symbiont Richelia intracellularis Schmidt

Aggregates of two species of Rhizosolenia (R. castracanei andR. imbricata var. shrubsolei) have been reported to containendosymbiotic bacteria and to fix nitrogen. The general importanceof this process to the genus is not known, although of greatpotential significance. Clonal cultures of five species of Rhizosolenia(R. alata, R. bergonii, R. calcar-avis, R. imbricata var. shrubsoleiand R. setigera) were examined for nitrogen fixation using acetylenereduction and compared to cyanobacterial controls. Mecososmaggregates of R. imbricata var. shrubsolei were tested, as wellas chains of R. debyana hand-collected using SCUBA. The Rhizosoleniaspecies did not contain the endosymbiotic cyanobacterium Richeliaintracellularis and were not examined for the presence of endosymbioticbacteria. Nitrogen fixation was not found in the Rhizosoleniaspp.; in contrast, the diazotrophic cyanobacterial controlsOscillatoria erythraea and Anabaena sp. reduced acetylene atsignificant rates. The absence of nitrogen fixation in the Rhizosoleniaspp. suggests diazotrophy by endosymbiotic bacteria is not widespreadin the genus Rhizosolenia, nor is it necessary for survivalof these large diatom cells in nutrient-poor, near-shore waters.