Detection and Evaluation of an Inducer of a Diffusible Mating Pheromone of the Heterothallic Closterium peracerosum-strigosum-littorale Complex

When mating-type plus cells of the Closterium peracerosum-strigosum-littoralecomplex were incubated in nitrogen-deficient medium obtainedfrom a 24-h-old mixed culture of mating-type plus and mating-typeminus cells, protoplast-release-inducing activity specific formating-type minus cells was detected in the medium. When mating-typeplus cells were incubated in the medium from a culture of exclusivelymating-type minus cells, protoplast-release-inducing activitywas also detected. These results suggested the existence ofa substance, released from mating-type minus cells, that hasthe ability to make mating-type plus cells release protoplast-release-inducingprotein (PR-IP). We designated it PR-IP Inducer. The PR-IP Inducerwas constitutively released from mt^– cells in the light.The PR-IP Inducer was heat-labile and had a relative molecularweight of 10,000 on gel filtration. We suggest that the PR-IPInducer is also a pheromonal substance that plays a role inthe initial events in the sexual communication of this Closteriumcomplex. (Received April 26, 1993; Accepted July 15, 1993)     

Regulation of Free Calcium Concentration in the Pitchers of the Carnivorous Plant Sarracenia purpurea: A Model for Calcium in the Higher Plant Apoplast?

The pitcher of the carnivorous plant Sarracenia purpurea L.contains an entrapped body of liquid within which its prey isdigested. Free calcium in the pitcher is derived from eitherthe pitcher walls or from prey falling into the pitcher; inthe absence of exogenous (prey-derived) calcium it will dependon the active and passive calcium regulatory properties of thepitcher walls and may to some extent therefore mimic calciumin the apoplast of plant cells. Using a calcium-specific electrode,the free calcium concentration of the pitchers of Sarraceniaplants was investigated and the effect of adding a variety ofconcentrations of calcium in water determined. The mean pitcherfree calcium concentration in vivo was 2.3 x 10^–5 M±2.5x 10^–5 M; when pitchers were washed and filled with watercontaining lower calcium concentrations, the concentration inthe pitcher water rose to 1–5 x 10^–5 M. When highercalcium concentrations (up to 1 x 10^–4 M) were added,the pitcher calcium concentration declined to 1–7 x 10^–5M. Concentrations of calcium above 1 x 10^–4 M were alsoreduced, but to a lesser extent. Metabolic inhibition of activeion transport, while inhibiting pitcher acidification, did notinhibit regulation of pitcher free calcium, suggested that itoccurs as a result of calcium exchange sites in the pitcherwalls. The data are discussed in relation to the physiologyof Sarracenia pitchers and to the usefulness of the pitcheras a model for free calcium in the higher plant apoplast. Sarracenia purpurea L., carnivorous plant, pitcher, free calcium, plant apoplast     

Discrimination of female sex pheromone by male Trichoplusia ni (Hubner)

The olfactory discrimination process of male cabbage loopermoths, Trichoplusa ni (Hübner), was assessed by measuringtheir response to one of two emission sources within a windtunnel. The males discriminated between (1) Z7–12:Ac concentrations;(2) Z7–12:Ac alone and the volatile emission from excisedfemale sex pheromone glands; and (3) Z7–12:Ac and theemission from a mixture of six synthetic pheromone componentsthat mimics the volatile emissions of a female gland. Althoughmales could discriminate between a freshly excised female sexpheromone gland and 7.4x 10^–11 M Z7–12:Ac, theycould not discriminate between a gland and 78.5x10^–11M Z7–12:Ac. Males also could not discriminate betweenthe mixture of six volatile compounds and 28.7x10^–11 Mof Z7–12:Ac. The data show that male cabbage looper mothshave difficulty discriminating between Z7–12:Ac aloneand in mixtures with other female-emitted volatile compounds.     

Distribution of Growth in the Apical Region of the Shoot of Lupinus albus

The purpose of the investigation is the determination of thevolumes and numbers of cells of the meristematic dome and ofeach of the first 7 primordia and internodes at the apex ofthe shoot of Lupinui albus. This system occupies a zone whichis about 0·4 mm. in length. Techniques are describedfor dissecting the region in which the observations are made,for determining the numbers of cells and the volumes of theseveral fragments. From the number of cells and the volume ofeach fragment an average cell volume it calculated. It is shown that in the midphase of the plastochron the domecontains 3,500 cells and has a volume of 1·6 x10^–3mm.³,the first primordium contains 1,630 cells and has a volume of0·38 x10^–3 mm.³, and the first intemode containsabout 700 cells and has a volume of about 1·4 x10^–3mm³The number of cells and the volume of the primordium increaseexponentially with increasing plastochron age, and the seventhprimordium contains 26,000 cells and has a volume of 20·9x 10^–3mm³ The seventh intemode contains about 5,000 cellsand has a volume of 8·6x10^–3mm³ The average cell volume in the dome is 4·7 x 10^–7mm.³in the first primorndium it is 2·3 x 10^–7mm.³ andin the first internode it is 20·9x 10^–7mm.³ Inthe seventh primordium the average cell volume increases to7·9 x 10^–7mm.³ In the internodes there is little,if. any, change in cell volume from the first to the seventhof the series. The significance of these changes is discussed.     

Density and distribution of bacterioplankton and planktonic ciliates in the Bering Sea and North Pacific

The total number of planktonic bacteria in the upper mixed layerof the Bering Sea during the late spring-early summer periodranged between 1 and {small tilde}4 x 10⁶ ml^–1 (biomass10–40mg C m^–3). In the northern Pacific, along 47–52⁶N,the corresponding characteristics of the bacterioplankton densityin the upper mixed water layer were: total number 1–2x 10⁶ cells ml^–1 and biomass 15–46mg C m^–3Below the thermocline at 50–100 m, the density of bacterioplanktonrapidly decreased. At 300 m depth, it stabilized at 0.1–0.2x 106 cells ml^–1. The integrated biomass of bacterioplanktonin the open Bering Sea ranged between 1.2 and 3.6 g C m^–2(wet biomass 6–18 g m^–2) Its production per dayvaried from 2 to 23 mg C m^–3 days^–1 in the upper0–100 m. The numerical abundance of planktonic ciliatesin this layer was estimated to be from 3 to l0 x 10³ cells l^–1,and in the northern Pacific from 0.4 to 4.5 x 10³ l^–2.Their populations were dominated by naked forms of Strombidium,Strombilidium and Tontonia. In some shelf areas, up to 40% ofthe total ciliate population was represented by the symbioticciliate Mesodinium rubrum. The data on the integrated biomassof basic groups of planktonic microheterotrophs are also presented,and their importance in the trophic relationships in pelagiccommunities of subarctic seas is discussed.     

Effects of Colchicine, Vinblastine, Cytochalasin B and Phalloidin on the Seismonastic Movement of Mimosa pudica Leaf and on Motor Cell Ultrastructure

Fleurat-Lessard, P., Roblin, G., Bonmort, J. and Besse, C. 1988.Effects of colchicine, vinblastine, cytochalasin B and phalloidinon the seismonastic movement of Mimosa pudica leaf and on motorcell ultrastructure.—J. exp. Bot. 39: 209–221. Colchicine at 1 x 10^–3 mol dm^–3 does not affectthe seismonastic movement of Mimosa pudica leaves but disruptsmicrotubules in motor cells. Vinblastine at 5 x 10^–3 moldm^–3 does not affect this movement and partly disruptsmicrotubules. Vinblastine at 1 x 10^–4 mol dm^–3 alwaysdisrupts microtubules, even after a 12 h reversibility whenthe movement is restored. These drugs, applied at the same respectiveconcentrations, do not alter cytoplasmic and vacuolar fibrils.Cytochalasin B and phalloidin alter the seismonastic movementof Mimosa leaves when applied at concentrations of 1.25 x 10^–3and 2.4 x 10^–4 mol dm^–3 respectively. These drugs,used at the same respective concentrations, also affect themotor cell structure and, in particular, modify the arrangementand the structure of the fibrils but they do not destroy themicrotubules. These data suggest that microtubules are not directly involvedin the seismonastic reaction whereas fibrils, formed by thin(3.0 nm wide) filaments, may be implicated in this reaction. Key words: Colchicine, cytochalasin B, phalloidin, Mimosa pudica, motor cells, vinblastine     

L-Leucine Transport in Isolated Protoplasts of Vinca Suspension Culture: Characterization of Uptake

The uptake of L-leucine into Vinca protoplasts was studied undervarious conditions. The uptake was highly pH-dependent, withthe optimal pH between 3.0 and 4.0. The uptake was also energydependent, since azide, 2,4-dinitrophenol (DNP), carbonyl cyanidem-chlorophenyl hydrazone (CCCP), and iodoacetate inhibited theuptake. Oligomycin, N,N'-dicycIohexyI carbodiimide (DCCD) andvanadate, but not ouabain, inhibited the uptake, suggestingthat ATPase for H⁺ electrogenic extrusion was necessary to theuptake of L-leucine. The uptake showed stereospecificity, butwas partially inhibited by other L-amino acids. A kinetic studyof the uptake showed that the uptake was multiphasic with threesaturable phases and one unsaturable phase which occurred atconcentrations of L-leucine over 1 mM. The K_m values of thethree affinity sites were 1.4 x 10^–3 M, 1.3 x 10^–4M, 4.3 x 10^–5 M; the maximum velocity values were 3.3x 10^–8, 4.5 x 10^–9, 1.8 x 10_–9 mol/10 min/4x 10⁶ cells. (Received April 18, 1981; Accepted August 25, 1981)     

Fluxes of diatoms in the Dona Paula Bay, west coast of India

Sediment traps were deployed at a station in the Dona PaulaBay to collect sedimenting particles at weekly intervals fromNovember to May during 1995–1997. Sedimented particleswere analysed for total diatom flux, chlorophyll a (Chl a) andparticulate organic carbon (POC). The highest diatom flux wasrecorded in April–May for both the years. Fluxes of diatomsvaried from0.6 x 10⁴ cells m^–2 day^–1 (November 1995)to 121.47 x 10⁴ cells m^–2 day^–1 (December 1996).In all, 19 diatom genera were identified in the sedimented material.Navicula, Nitzschia, Pleurosigma, Licmophora, Coscinodiscus,Rhizosolenia and Surirella were the most abundant genera inthe sedimented material throughout the sampling period. Meanflux of POC and diatom carbon was 251 and 0.39 mg C m^–2day^–1, respectively. The diatom carbon accounted for 0.15%of the POC flux. Mass flux of diatoms showed significant negativecorrelation with the concentration of nitrate and phosphate.This suggests that the nutrient concentration played an importantrole in influencing the sedimentation of diatoms at this coastalstation.     

The Genetic Basis of Preference for Sweet Substances Among Inbred Strains of Mice: Preference Ratio Phenotypes and the Alleles of the Sac and dpa Loci

Five inbred strains (129/J, BALB/cByJ, C3HeB/FeJ, C57BI/6J andDBA/2J) were examined with two-bottle (48 h) preference ratiotesting across concentrations of sodium saccharin (3 x 10^–4M, 10^–3 M, 3 x 10^–3 M and 10^–2 M), d-phenylalanine(10^–3 M, 10^–2 M and 10^–1 M), and l-glutamine(10^–2 M, 3 x 10^–2 M, 10^–1 M and 3 x 10^–1M). Three consistent groupings of strains were observed acrosssubstances and concentrations:

1. C57BI/6J (preference at low andhigh concentrations);
2. BALB/cByJ and C3HeB/FeJ (preferenceat high concentrations);
3. 129/J and DBA/2J (preference at highconcentration for sodiumsaccharin and indifference to d-phenylalanineand l-glutamine).

If a single locus (presumably dpa or Sac) determines these phenotypes,there are likely to be three alleles. If two independent loci(presumably dpa and Sac) determine these phenotypes, an allelicassignment of Sac^b/dpa^+s for the C57BI/6J strain, Sac^b/dpa^–sfor the BALB/cByJ and C3HeB/FeJ strains, and either Sac^d/dpa^+sor Sac^d/dpa^–s for the 129/J and DBA/2J strains is suggested.Chem. Senses 20: 291–298, 1995.     

Purification, Identification, Concentration and Bioactivity of (Z)-7-Dodecen-1-yl Acetate: Sex Pheromone of the Female Asian Elephant, Elephas maximus

In their natural ecosystems, adult male and female Asian elephants,Elephas maximus, live separately. For several weeks prior toovulation, female elephants release a substance in their urinewhich elicits a high frequency of non-habituating chemosensoryresponses, especially flehmen responses, from male elephants.These responses occur prior to, and are an integral part of,mating. Using bioassay-guided fractionation, quantitativelydependent on these chemosensory responses, a specific sex pheromonewas isolated and purified by an alternating series of organicand/or aqueous extractions, column chromatography, gas chromatographyand high-performance liquid chromatography. Using primarily¹H-proton nuclear magnetic resonance (NMR) spectrometry andgas chromatography-mass spectrometry (GC-MS) of the urine-derivedpheromone and its dimethyl disulfide derivative, we determinedthe structure of the active compound to be (Z)-7-dodecen-1-ylacetate (Z7-12:Ac). Concentrations of Z7-12:Ac in the femaleurine increased from non-detectable during the luteal phaseto 0.48µg/ml (0.002 mM) early in the follicular phaseand to 33.0µg/ml (0.146 mM) just prior to ovulation. Bioassayswith commercially available authentic synthetic Z7-12:Ac, using10 Asian male elephants at several locations in the US, demonstratedquantitatively elevated chemosensory responses that were robustduring successive tests, and several mating-associated behaviors.Bioassays with Z7-12:Ac with adult male elephants dwelling inmore natural social situations in forest camps in Myanmar revealedsome differing contextual pre-mating behavioral components.The remarkable convergent evolution of this compound suggeststhat compounds identified in mammalian exudates that are alsopresent in pheromone blends of insects should be re-evaluatedas potential mammalian chemosignals. Chem. Senses 22: 417–437,1997.     

Effect of Spermidine and Methylglyoxal-bis (Guanyl-hydrazone) (MGBG) on In Vitro Pollen Germination and Tube Growth in Catharanthus roseus

Incorporation of polyamine-spermidine into the nutrient mediumat 10^–6 and 10^–5 M concentrations stimulates pollen-tubegrowth in vitro in Catharanthus roseus L. G. Don. MGBG, an inhibitorof spermidine biosynthesis, at 0.5 x 10^–3 and 1 x 10^–3M concentrations reduced the percentage of germination as wellas tube growth and at a concentration of 1.5 x 10^–3 Mgermination was totally inhibited. Pollen grains incubated inthe medium containing 1.5 x 10^–3 M MGBG, when transferredto a fresh medium with 10^–5 M spermidine, resulted in80% germination recovery, along with considerable tube growth.Experiments with actinomycin-D indicate that stimulation ofpollen-tube growth by spermidine may involve de novo synthesisof protein. Catharanthus roseus, pollen germination, tube growth, spermidine, MGBG, inhibition, actinomycin-D     

Dynamics of herbivorous grazing by the heterotrophic dinoflagellate oxyrrhis marina

In a series of batch experiments in the dark the heterotrophicdinoflagellate Oxyrrhis marina grazed three phytoplankton prey(Phaeodactylun tricornutum, Isochrysis galbana and Dunaliellateriolecta) with equal efficiency. Growth rates of the dinoflagellateranged between 0.8 and 1.3 day–1 Maximum observed ingestionrates on a cell basis varied according to the size of the preyfrom about 50 cells flagellate^–1 day^–1 when D.tertiolectawas the prey to 250–350 cells fiagellate^–1 day^–1when the other species were eaten. However, when compared ona nitrogen basis, ingestion rates were independent of prey type.Both ingestion and growth ceased when prey cell concentrationsfell below a threshold concentration of about 10⁵ cells ml^–1.Maximum specific clearance rates were 0.8x10⁴0ndash;5.7x10⁴it day which is considerably lower than that found for heterotrophicdinoflagellates in oceanic waters and may explain why O.marinagenerally thrives only in productive waters. The timing of NHregeneration was linked to the C:N ratio of the prey at thestart of grazing. Regeneration efficiencies for NH₄. never exceeded7%; during the exponential phase and were 45% well into thestationary phase. These results are comparable to those obtainedwith heterotrophic flagellates and demonstrate that the bioenergeticpatterns of grazing and nutrient cycling by different protozoaare very similar. Moreover, they support the notion that toachieve 90+% nutrient regeneration in the open ocean, as iscurrently believed, the microbial food loop must consist ofmultiple feeding steps. Alternatively, nutrient regenerationefficiencies may be considerably lower than 90%.     

Direct Somatic Embryogenesis in Roots of Cichorium: Is Callose an Early Marker?

Direct somatic embryogenesis can be obtained from epidermaland cortical cells in roots from in vitro Cichorium plantlets.The first embryogenic cells are seen after six days of culturein darkness, at 35 °C, in a liquid medium supplemented withNAA (1 x 10^–7 M), 6-dimethylallyl-amino-purine (2·5x 10^–6 M), sucrose (0.03 M) and glutamine (1·7x 10^–3 M). Embryogenic cells undergo first a linear andthen a globular segmentation, with increasing cytoplasmic density.These cells and young embryoids show aniline blue fluorescence.SEM allows the same microglobular pattern to be seen on thesurface of young embryoids and on young microspores of Cichoriumused as controls. In this root system, callose deposition seemsto be an early marker in somatic embryogenesis. Somatic embryogenesis, callose, Cichorium     

Cyst formation: an important mechanism for the termination of Scrippsiella trochoidea (Dinophyceae) bloom

A sediment trap study was conducted at Daya Bay, South ChinaSea, to investigate the relationships between encystment andpopulation dynamics of Scrippsiella trochoidea from December1999 to January 2001. A dense bloom of S. trochoidea occurredduring the study period from August to September 2000, withthe maximum cell number of 3.18 x 10⁴ cells mL^–1.Two morphotypes of cysts, one with a thick calcareous wall (calcifiedcyst) and another without the obvious calcareous cover (non-calcifiedcyst), were observed during this investigation. The morphologicaland excystment characteristics of these two cyst types werestudied as well. Mass encystments of S. trochoidea, with themaximum of 3.05 x 10⁵ cysts m^–2 d^–1for calcified cyst, and 1.54 x 10⁷ cysts m^–2 d^–1for non-calcified cyst, coincided with the maximum abundanceof the vegetative cells. Encystment caused the transfer of atotal of 2.24–4.49 x 10⁸ cells m^–2 vegetativecells from the water column to the sea bottom during the bloomand resulted in a considerable loss of the bloom population.High assemblages of cysts of S. trochoidea were detected inthe surface sediments as well. This rich ‘seed bed’in the surface sediments caused by the high efficiency of encystmentafter blooms acting as a benthic reservoir for future vegetativepopulation, together with the short dormant period (15–26days) and high germination rate (50–90%), may explainthe repeated occurrence of S. trochoidea blooms in Daya Bay.     

Purification of Ribulose 5-phosphate Kinase and Minor Polypeptides of Pyrenoid from the Green Alga Bryopsis maxima

Ribulose 5-phosphate (Ru5P) kinase (ATP:D-ribulose 5-phosphate1-phosphotrans- ferase; EC 2.7.1.19 [EC] ), an enzyme in the reductivepentose phosphate cycle, was purified from the green alga Bryopsismaxima and its activity and peptide composition were studied.The specific activity of purified Ru5P kinase was 20 µmoleRuBP formed (mg protein)^–1 min^–1 corresponding toa 490-fold purification from the supernatant of chloroplasts.The K_m values of Ru5P kinase for ATP and Ru5P were 69 µMand 330 µM, respectively. The molecular size of Ru5P kinase was estimated as 90 kDa bygel filtration and that of its polypeptide as 41 kDa by SDS-polyacrylamidegel electrophoresis. A small portion of the Ru5P kinase wasfound in a large molecular state (500 kDa) which was consideredto be an inactive form of the enzyme. Ru5P kinase activity has been reported in the pyrenoid of Eremosphaeraviridis as well as ribulose 1,5-bisphosphate carboxylase-oxygenase(RuBisCO) and ribose 5-phosphate isomerase activity (Holdsworth1971). In Bryopsis maxima, among the pyrenoid polypeptides otherthan that of RuBisCO, we found a polypeptide of 42 kDa, similarto that of Ru5P kinase in molecular size and ratio to RuBisCO.A peptide map of the 42 kDa pyrenoid polypeptide, however, showedthat it differed from that of Ru5P kinase. In conclusion, Ru5Pkinase may be not involved in the pyrenoid of this alga. (Received January 19, 1985; Accepted May 15, 1985)     

Enzymes involved in the last steps of the biosynthesis of mannitol in brown algae

Mannitol-1-phosphate dehydrogenase (EC 1.1.1.17 [EC] ) and mannitol-1-phosphatase(EC number yet unassigned) were detected in the brown algae,Spatoglossum pacificum and Dictyota dichotoma. The enzymes wereextracted from algal fronds and their properties were investigatedusing partially purified preparations. Mannitol-1-phosphatase shows maximum activity at pH 7. The enzymehad a narrow substrate specificity. The Km value for mannitol-1-phosphateis 8.3x10^–4 M (30°C, pH 7.0). The enzyme is activatedby Mg⁺⁺ and Mn⁺⁺and is strongly inhibited by PCMB, Hg⁺⁺and NaF. Mannitol-1-phosphate dehydrogenase showed maximum activitiesat pH values 6.5 and 10.2 in reductive and oxidative reactions,respectively. The dehydrogenase also showed narrow substratespecificity; mannitol-1-phosphate and NAD or fructose-6-phosphateand NADH₂ are utilized, respectively, in oxidative and reductivereactions by the enzyme. Km values for these substrates andthe coenzymes are 2.5x10^–4 M and 7.1x10^–5 M forthe first pair and 2.8x10^–4 M and 1.3x10^–5 M forthe latter pair. This enzyme was strongly inhibited by PCMBand Hg⁺⁺, but was only slightly affected by adenosine phosphates. Possible roles of these enzymes in the biosynthesis of mannitolin brown algae are discussed. ¹ Contributions from the Shimoda Marine Biological Station ofTokyo Kyoiku University, No. 233. This work was supported inpart by a Grant-in-Aid for Co-operative Research from the Ministryof Education, Japan and in part by a grant to one of us (T.Ikawa) from the Matsunaga Science Foundation. ² Present address: Chemical and Physical Laboratory, HoechstJapan Research Laboratory, Minamidai, Kawagoe, Japan. (Received February 22, 1972; )     

Effects of indoleacetic, p-chlorophenoxyisobutyric and 2,4,6-trichlorophenoxyacetic acids on three phases of rooting in Azukia cuttings

In adventitious root formation of disbudded epicotyl cuttingstaken from light-grown, 5-day-old Azukia angularis seedlings,indoleacetic acid (IAA), 1 x 10^–4 M, applied during thefirst day showed no effect, but enhanced the effect of IAA,1 x 10^–4 M, applied during the second day. Treatment duringthe second day promoted rooting by about 70%, and a combinationof treatments for the first and second days promoted rootingsome 200%. p-Chlorophenoxyisobutyric acid (PCIB), 3 x 10^–4M, and2,4,6-trichlorophenoxyacetic acid (2,4,6-T), 2 x 10^–44M, applied the first day also enhanced the effect of IAA, 2x 10^–4 M, applied the second day. When applied the second day, PCIB, 2 x 10^–4M, increasedthe number of root primordia or clusters of small cells, butnot die number of protruded roots. Formation of the cell clusterwas inhibited by 2,4,6-T, 3 x 10^–4M, applied the secondday. Rooting processes in Azukia cuttings seem to include at leastthree phases: the first phase is induced not only by IAA butalso by PCIB or 2,4,6-T, the second phase is induced by IAAor PCIB and the diird phase depends specifically on IAA. (Received October 28, 1970; )     

Laboratory-measured grazing and ingestion rates of the salp, Thalia democratica Forskal, and the doliolid, Dolioletta gegenbauri Uljanin (Tunicata, Thaliacea)

Grazing and ingestion rates of laboratory-born Thalia democraticaaggregates and Dolioletta gegenbauri gonozooids, phorozooidsand oozooids were determined while fed Isochrysis galbana (4–5µm diameter) alone or in combination with Peridinium trochoideum(16–18 µm diameter) at concentrations of 0.15–0.70mm³ x 1^–1. Grazing rates (ml x zooid^–1 x 24 h ^–1)ranged from 10 to 355, and at zooid weights greater than 5 µgcarbon were in order oozooid > gonozooid > aggregate.Grazing rates increased exponentially with increasing zooidweight. Weight-specific grazing rates (ml x µgC^–1x 24 h^–1) were independent of the four-fold initial foodconcentration. Mean weight-specific grazing rates increasedlinearly with increasing zooid weight for the aggregates andoozooids, but gonozooid mean rates were independent of zooidweight. Aggregate and gonozooid ingestion rates (10⁶ µm³x zooid^–1 x 24 h^–1) ranged from 4 to 134 while oozooidrates ranged from 3 to 67. All ingestion rates were independentof the initial food concentration but increased linearly withincreasing zooid weight at similar rates. All mean weight-specificingestion rates (ml x µgC^–1 x 24 h^–1) wereindependent of zooid weight. The mean aggregate daily ration(µgC ingested x µg body C^–1) was 59% and themean doliolid ration was 132%. Field studies indicate that normalconcentrations of D. gegenbauri in the Georgia Bight clear theirresident water volume (1 m³) in about 4 months, but that highlyconcentrated, swarm populations which occur along thermohalinefronts clear their resident water volume in less than 1 day. ¹Current address: MacLaren Plansearch Ltd., P.O.Box 13250, sta.A.,St.John's, Nfld. A1B 4A5