DISTRIBUTION AND PRODUCTION OF THREE HYDROBIA SPECIES (GASTROPODA: HYDROBIIDAE) IN A SHALLOW COASTAL LAGOON IN THE BAY OF CADIZ, SPAIN

The abundance, life span, growth and production of the mud snailsHydrobia minoricensis, H. ulvae and H. ventrosa in a semi-naturallagoon system were studied by taking monthly samples at threesites during 1991 and 1992. The most abundant species, H. minoricensisoccurred at mean densities of 12834 to 26264 snails m^–2(10.7 to 25.8g dry weigh m^–2), depending on the site.The least abundant species, H. ulvae, occurred at mean densitiesof 185 to 353 snails m^–2 (3.2 to 2.2g dry weight m^–2).The numerical abundance and biomass of the three Hydrobia specieswere positively related to the biomass of benthic macroalgae(P<0.01). Although H. ulvae egg capsules were recorded throughoutthe year, newly hatched snailsof this species were not observed,in contrast to the other two species. The early spring and summercohorts of H. minoricensis and H. ventrosa seemed to be themost numerous. The average life spans of these two species wereestimated to be about 18 and 13 months respectively. Annualproduction estimates for the whole lagoon system were 29.0 (6.3),5.5 (0.8) and 5.2 (1.0)g dry weight (ash-free dry weight) m^–2yr^–1 for H. minoricensis, H. ulvae and H. ventrosa respectively.The annual P/B ratio was about 2 for H. minoricensis and H.ventrosa. (Received 5 July 1994; accepted 5 October 1994)     

INTER-YEAR CONTRAST IN NUMBERS AND ANNUAL PRODUCTION OF THE CEPHALASPIDEAN OPISTHOBRANCH RETUSA OBTUSA (MONTAGU) AND THE POSSIBLE INFLUENCE OF WIND-SPEED

Retusa obtusa was far more abundant throughout August 1986-July1987 than in all 12 corresponding months of April 1992-March1993. The greatest difference was when the highest of all counts(3232 m^-2) in May 1987 was 18-times that in May 1992. The leastdifference was a 2.4-fold discrepancy between the two Septembercounts. Mean monthly counts for the 2 periods were 781.4 m^-2(1986-87) and 123.6 (1992-93): a difference of 6.3-times. Biomasssimilarly differed between the 2 periods by factors between2.5 (July) and 12 (March), with a 5.3-fold difference betweenmean monthly biomass values. Annual production was accordinglyestimated as 618.3 (1986-87) and 152.4 (1992-93) mg AFDW m^-2y^-1; so differing by a factor of 4. Yet, in both these 1-yearperiods of observation, the general pattern of annual changewas the same, with settlement in February-May, growth from springto winter, most spawning in December-March and death of adultsat about 1 year in April-May. It is likely that the winter-springperiod of early development in benthic eggs followed by pelagicdispersal, and then settlement in February -May, is a periodof especial vulnerability. In particular, it seems likely thatduring January-May, markedly higher wind-speeds in 1992 thanin 1987 might have contributed to the huge difference in numbersof recruits (Received 2 February 1994; accepted 18 March 1994)     

COMPARATIVE LIFE-CYCLE, BIOMASS AND SECONDARY PRODUCTION OF THREE SYMPATRIC FRESHWATER GASTROPOD SPECIES

The life cycles, biomass and secondary production of three sympatricfreshwater basommatophoran snails, Lymnaea palustris (MÜller),Physa fontinalis Linnaeus and Anisus rotundatus (Poiret) werestudied during two years in a freshwater ditch. L. palustrisexhibited an iteroparous life-cycle whereas the two other speciespresented a semelparous life-cycle, adults died just after oviposition.L. palustris secondary production (dry weight) value was higher(P = 11 298.4 mg 0.1 m^–1 yr^–1) than those of P.fontinalis (P = 846.3 mg 0.1 m^–2 yr^–1) and A. rotundatus(P = 1192 mg 0.1 m^–2 yr^–1). (Received 16 March 1992; accepted 30 June 1992)     

OBSERVATIONS ON THE POPULATION DYNAMICS OF SNAIL HOSTS FOR SCHISTOSOMES IN THE DELTA OF THE SENEGAL RIVER BASIN

Between 1987 and 1990, snail surveys were carried out in theSenegal River Basin at Lampsar, in a natural ‘marigot’,and at Richard Toll, in an irrigation canal. Lymnaea natalensis.Bulinus guernet^* and B.forskalii, were regularly found at boththe sites. Bulinus globosus/jousseaumei and B. umbilicatus wereonly present at Lampsar. A decrease of the snail density wasobserved during the rainy season at Lampsar. The recent appearanceof Biomphalaria pfeifferi at Richard Toll is discussed. Thedata show that adult B. pfeiffert are present in the main irrigationcanal all through the year. Consequently parasite transmissionwill be possible throughout the year as well. (Received 23 October 1991; accepted 20 May 1992)     

SURFACING AND WATER LEAVING BEHAVIOUR OF THE FRESHWATER PULMONATE SNAILS LYMNAEA PEREGRA (MULLER), BIOMPHALARIA GLABRATA (SAY) AND BULINUS JOUSSEAUMEI (DAUTZENBERG)

Surfacing and water-leaving behaviour (quitting) of aquaticpulmonate snails was investigated in the laboratory. Regressioncoefficients of surfacing rate per hour for 16 snails in 200cm³ of water were 1.28 for L. peregra, 1.35 for B. glabrata(albino form), 0.47 for B. glabrata (pigmented form) and 0.17for B. jousseaumei. Disturbance, snail size and conditioningof the water were relatively unimportant factors; water volumeadjusted by depth was also unimportant up to 50 mm depth. Importantfactors controlling surfacing appeared to be population density,time of year, temperature, water volume adjusted by perimeterand dissolved oxygen concentration. The response to the latterwas not clear and both B. glabrata and L. peregra orientatedalmost as well to a nitrogen/water interface as to an air/waterinterface. Water-quitting regressed on volume, which had beenadjusted by perimeter variation, revealed a curvilinear relationshipfor B. glabrata, with maximum quitting at 1 snail per 7cm³ (1snail per 14cm of climbable perimeter). L. peregra showed anegative exponential curve, with maximum quitting at 1 snailper 3 cm³ of water (1 snail per 8 cm of climbable perimeter).These data could be relevant to design and management of irrigationchannels where bilharzia might occur. (Received 28 November 1990; accepted 22 October 1991)     

THE LIFE CYCLE, POPULATION DYNAMICS, GROWTH AND SECONDARY PRODUCTION OF THE SNAIL BRADYBAENA FRUTICUM (MULLER, 1774) (GASTROPODA PULMONATA) IN NORTHERN GREECE

The life cycle, population dynamics, growth and secondary productionof the pulmonate land snail Bradybaena fruticum were studiedin northern Greece. The demographic analysis of the populationsof B. fruticum revealed that a) two cohorts exist in the fieldthroughout the year b) the reproductive period started in thebeginning of summer and c) growth was increased during springand autumn. According to von Bertallanffy' method B. fruticum needs 5 yearsto attain its maximum size in the field of 25.40 mm. Mortalityrate increases and life expectancy decreases with increasingage. Net reproductive rate (Ro) was equal to 3. 15 and per capitarate of increase (r^c) was equal to 1. Annual secondary production, calculated by Hynes' size frequencymethod, revealed a mean annual density of 5.9 individuals/m²,a mean standing crop (B) of 8.09 g/m²/year and an annual production(P) of 1.92 ± 0.11g/m²/year. Annual turnover ratio (P/B)was equal to 2.37. (Received 25 May 1989; accepted 17 March 1989)     

POPULATION DYNAMICS OF ZEBRA MUSSELS DREISSENA POLYMORPHA (PALLAS, 1771) DURING THE INITIAL INVASION OF THE UPPER MISSISSIPPI RIVER, USA

The aim of this study was to document and model the populationdynamics of zebra mussels Dreissena polymorpha (Pallas, 1771)in Pool 8 of the Upper Mississippi River (UMR), USA, for fiveconsecutive years (1992–1996) following their initialdiscovery in September 1991. Artificial substrates (concreteblocks, 0.49 m² surface area) were deployed on or aroundthe first of May at two sites within each of two habitat types(main channel border and contiguous backwater). Blocks wereremoved monthly (30 ± 10 d) from the end ofMay to the end of October to obtain density and growth information.Some blocks deployed in May 1995 were retrieved in April 1996to obtain information about over-winter growth and survival.The annual density of zebra mussels in Pool 8 of the UMR increasedfrom 3.5/m² in 1992 to 14,956/m² in 1996. The average May–Octobergrowth rate of newly recruited individuals, based on a von Bertalanffygrowth model fitted to monthly shell-length composition data,was 0.11 mm/d. Model estimates of the average survivalrate varied from 21 to 100% per month. Estimated recruitmentvaried substantially among months, with highest levels occurringin September–October of 1994 and 1996, and in July of1995. Recruitment and density in both habitat types increasedby two orders of magnitude in 1996. Follow-up studies will benecessary to assess the long-term stability of zebra musselpopulations in the UMR; this study provides the critical baselineinformation needed for those future comparisons. (Received 5 November 2004; accepted 30 September 2005)     

INTRA-POPULATION VARIATION OF THE SHELL OF LITTORINA RUDIS (MATON) (MOLLUSCA: PROSOBRANCHIA)

Shell variation within a single population of Litlorina rudis(Maton), collected near the Biological Station at Trondheim,Norway, was studied. The variation of the shell features studied, which includedthe shape of the basal part of the outer lip, and the relativeheight of the spire, width of the shell and of the aperture,were found to be at least partially related to shell height.Furthermore, the shell shape in the population investigated,besides varying with age, also varies due to shell damage. Nosignificant differences were found between the shapes of theshells of males and females. The shell characteristics of different populations of L. rudisalso vary greatly, one of the causes being differences in theenvironmental conditions. When studying this variation betweendifferent populations, however, it must be emphasized that onlyundamaged shells of individuals of about the same age shouldbe compared, in order to obviate the effects of the variabilitydue to age differences and shell damage within each individualpopulation. ^*Contribution from Trondhjem Biological Station no. 199 (Received 18 February 1980;     

ALLOZYME VARIATION AMONG POPULATIONS OF BIOMPHALARIA PFEIFFERI (KRAUSS, 1848) (GASTROPODA: PLANORBIDAE) IN CAMEROON

Allozyme electrophoresis was used to study genetic diversityamong the freshwater, hermaphroditic snail Biomphalaria pfeifferiin Cameroon. Four of 19 loci studied were polymorphic. The allozymesfor two loci, aspartate aminotransferase-1 (AAT-1) and isocitratedehydrogenase (IDH), showed distribution patterns related toclimatic zones. AAT-1¹⁰⁰ and IDH¹⁰⁰ occurred predominantly inthe Tropical Climatic Zone, located in the northern half ofthe country. AAT-1¹⁴⁰ and IDH⁹⁰ were common in the EquatorialZone. Intrapopulation variations occurred in 5 of 19 populationsampled. Only one population, polymorphic for AAT-1 locus, waspanmictic. The other 4 populations were not in Hardy-Weinbergequilibrium. The deficiency of heterozygotes in those populationsis unusual for a member of the genus Biomphalaria and may bedue to a predominance of self-fertilization. Other explanationsinclude ecological factors or the presence of segregated sub-populationsthat do not outcross. This latter hypothesis is supported bythe total absence of heterozygotes for PGM alleles. (Received 24 August 1989; accepted 14 September 1989)     

TROPHIC ROLES OF CO-OCCURRING SPECIES OF DRUPA (GASTROPODA: MURICIDAE) AT ENEWETAK ATOLL

Diets in nature differed significantly among three species ofthe gastropod genus Drupa (Muricidae: Thaidinae) on a windward,seaward reef platform at Enewetak Atoll, Marshall Islands. Nereidand eunicid polychaetes and vermetid gastropods were the mostimportant prey organisms. D. morum ate mainly Perinereis, Ceratonereisand eunicids; D. ricinus ate mainly Ceratonereis in protectedsites and Dendropoma near the exposed outer reef edge. Sizeof Drupa was correlated with that of vermetid but not polychaeteprey. The results are compared with data from studies of otherpredators on the same prey species at Enewetak, and with J.D. Taylor's data on the diets of Drupa species elsewhere inthe Indo-Pacific region. ^*Present address: Department of Zoology, University of California,Berkeley, California 94720. (Received 4 February 1989; accepted 6 March 1989)     

Effects of Acriflavine on the Formation of the Plasma Membrane of Escherichia coli

When cells of acriflavine-sensitive (acrA) and acriflavine-resistant(acrA⁺) Escherichia coli K-12 strains were treated with a ratherhigh concentration (100 µg ml^-1) of acriflavine in mediumthat had been adjusted to pH 8.1, distinct whirlpool-like structuresderived from the plasma membrane appeared not only in the acrAcells but also in the acrA⁺ cells. Chemical analysis was performedto determine the lipid composition of the cells by thin-layerchromatography on silica gel and gas-liquid chromatography.The amount of total fatty acids was significantly higher inthe acrA cells than in the acrA⁺ cells, when cells were culturedin the presence of acriflavine. This difference seems to becaused by the greater accumulation of unsaturated fatty acids(palmitoleic and cis-vaccenic acid) in the acrA mutant cellsthan in the acrA⁺ cells and by the acceleration of this accumulationas a result of the presence of the dye. A comparison of phospholipidcontents between the acrA and acrA⁺ cells cultured under acriflavine-freeconditions showed that the former cells contained more phosphatidylethanolamine(PE) and, in particular, more cardiolipin (CL) than the lattercells. However, the situation was reversed in the case of phosphatidylglycerol(PG). Addition of acriflavine to the medium led to a markedincrease in levels of PE and CL in both acrA and acrA⁺ cellsbut an increase in levels of PG was found only in the acrA⁺cells. (Received October 13, 1992; Accepted May 31, 1993)     

UPTAKE OF ACETATE BY NEOTRICULA APERTA (GASTROPODA: POMATIOPSIDAE), THE SNAIL HOST OF SCHISTOSOMA MEKONGI IN THE LOWER MEKONG BASIN

All three races of Neotricula aperta, an epilithic, schistosometransmitting, snail of the Mekong and Mul rivers of NortheastThailand and southern Laos, were found to take up acetate froma dilute solution. After 48 h incubation the mean specific netuptake rates (µmol^–1 g^–1 h^–1), from750 µM acetate, were: 1.86, -race; 1.39, ß-raceand 3.25, y-race. Over 48 h the snails were able to achievereductions in the ambient acetate concentration of up to 60%.Incubations under bacteriostatis suggested that bacteria arenot involved in the uptake of acetate by N. aperta. The uptakecharacteristics conform to the Michaelis-Menten model. The transportconstants, J_max (µmol^–1 g^–1 h^–1) andK_t (µM) were 1.10 and 102 respectively (-race). Racialdifferences in uptake characteristics are discussed in relationto micro-habitat differences. HPLC indicated concentrations of acetate in y-N. aperta microhabitatsof around 325 µM. This suggests a pool size sufficientto satisfy only 6% of the snail's basal metabolic rate (BMR).Levels within the epilithic aufwuchs, however, are probablyhigh enough to provide for more than 50% of the BMR. The possible role of acetate in the energy metabolism of N.aperta is discussed. Short-chain carboxylic acids (such as acetate),arising from the decomposition of the aufwuchs, could representsources of fermentable organics that may be taken up by N. apertasnails and used to supplement their nutrition during times offood shortage. However, further investigations involving ¹⁴C-labellingtechniques are required. The findings of this investigationhave implications for the chemical ecology and life-cycle ofN. aperta. (Received 16 June 1994; accepted 28 July 1994)     

Abolition of Heavy Metal Toxicity on Kirchneriella lunaris (Chlorophyta) by Calcium

The green alga Kirchneriella lunaris was incubated with variousheavy metals (Cd²⁺, Co²⁺, Mn²⁺, Ni²⁺) in presence/absence ofcalcium (Ca²⁺). The uptake of heavy metal was affected by Ca²⁺.Growth rate was inhibited by all heavy metals applied. In allCa²⁺-containing cultures Kirchneriella exhibited higher ratesof growth than those containing heavy metal alone. Photosynthesis/respirationratio of K. lunaris cells seems to be the determinant in thiswork. Ca²⁺ variably abolished the effects of the heavy metalsstudied. Maximal positive effect of Ca²⁺ was found with Cd²⁺while with Ni²⁺ it was negligible.Copyright 1995, 1999 AcademicPress Cadmium, cobalt, manganese, nickel, calcium, heavy metals, growth, photosynthesis, Kirchneriella lunaris     

Changes in the Levels of Ribulose-l,5-bisphosphate Carboxylase/Oxygenase (Rubisco) in Tetraedron minimum (Chlorophyta) during Light and Shade Adaptation

Exponentially growing cultures of the chlorophyta Tetraedronminimum were allowed to photoadapt to low (50µmole quantam^–2s^–1) and high (500µmole quanta m^–2–1)irradiance levels. In these cultures, various aspects of theorganization of the photosynthetic apparatus and related differencesin its performance were studied. In this organism, the observed five-fold increase in pigmentationof low-light adapted cells was due to increases in the numbersof PSU's, while their sizes remained constant. Using radioimmunoassay technique, we found that high-light adaptedalgae had over five times more Rubisco per PSU than their low-lightadapted counterparts. The high-light adapted algae also exhibited far higher (x2.3)light saturated photosynthetic rates per chl a. This increasewas the result of a reduction of tau, , the turnover time ofPS II reaction centers. We propose that the increase in Rubisco per PSU in high-lightadapted algae explains the reduction in , which results in thehigher P_max rates per chl a in these algae. The relationship is non linear, since the increase in Rubiscoper PSU was x5.3 whereas that in P_mM per chl a was only x2.3. (Received July 30, 1988; Accepted December 2, 1988)     

安徽虫瘟霉的黍米培养及其对桃蚜的侵染力

安徽虫瘟霉Zoophthora anhuiensis (Li) Humber是较难人工培养的蚜虫专化性病原真菌。将灭菌并适度熟化的黍米Panicum miliaceum L.作为固体基质与挑碎的安徽虫瘟霉平板菌落混合,在20℃和12L∶12D的温光条件下静止固体培养,获得了产孢潜能大、杀蚜活性强的米粒培养物。培养7天的黍米的产孢量达13.0×10⁴个孢子/粒,产孢持续时间长达6天。用此黍米培养物弹射的孢子对桃蚜Myzus persicae (Sulzer) 若蚜进行7.9～134.9个孢子/mm²共9个剂量的孢子浴接种,所获数据很好拟合时间 剂量 死亡率模型。接种后第5～7天各天的LC₅₀依次为59.8, 39.5和33.5个孢子/mm²,LC₉₀依次为354,234和198个孢子/mm²。在57.7～134.9个孢子/mm²的接种剂量范围内,致死中时LT₅₀从5.1天下降到4.3天。由此表明,安徽虫温霉的黍米培养不仅简单易行,而且菌种的产孢和侵染生物学特性在培养物中被充分体现,每颗米粒如同自然罹病而死的蚜尸,值得进一步研究开发和利用。     

PHOTOCHEMICAL REDUCTION AND OXIDATION OF MENADIONE (VITAMIN K3) IN CHLOROPLASTS

1. Menadione (vitamin K³) was found to be completely reduced byilluminated spinach chloroplasts under highly anaerobic conditionand in the presence of ethylenediamine tetraacetate (EDTA) inthe reaction mixture. This photoreductive reaction is sensitivetoward heat-treatment and inhibited by 2?10^-3M hydroxylamine.
2. In the presence of oxygen, the reduced form of menadione israpidly photooxidized by chloroplasts. This photooxidative activityalso is suppressed by heat-treatment but not inhibited by hydroxylamine.
3. Dyes which are inefficient as HILL oxidants such as thionineand methylene blue were found to be readily reduced by illuminatedchloroplasts, if the experimental conditions were appropriateto prevent the reoxidation of the photoreduced dyes; i.e., exhaustiveremoval of oxygen and the addition of EDTA in the reaction mixture.Menadione was found to accelerate the HILL reaction with thesedyes as oxidant under such experimental conditions.
4. In thepresence of molecular oxygen in the reaction mixture,menadionewas found to inhibit the HILL reaction with 2,6–dichlorophenolindophenol as oxidant, while the reaction rate was little influencedin high anaerobiosis.
5. These findings are explained by theintermediary oxidation and(photo-) reduction of menadione asan intermediary hydrogencarrier, and by the trends toward rapidphotooxidation of reducedmenadione.

(Received July 2, 1960; )     

Distribution pattern of decapod larvae off the north-western Iberian Peninsula coast (NE Atlantic)

In October 1977 the model of general circulation of the watermasses off the coast of Galicia, and the presence of a coastalupwelling, led to a high primary productivity. This high productivityin turn favoured the development of a rich population of decapodlarvae. The abundance and distribution pattern of these organismswere closely linked (i) to the abundant presence of the correspondingadult species in the area, (ii) with the spatial distributionof phytoplanktonic populations concurrently studied by Estrada[J. Plankton Res ., 6, 417–434 (1984)] and (iii) withthe hydrodynamic pattern in the area. Fifty-two decapod larvaetaxa were identified and Solenocera membranacea, Pisidia longicornis,Pilumnushirtellus and Goneplax rhomboides were the most representativespecies It was observed that the greatest concentrations oflarvae (3387 larvae 10^–2 m^–3) were to be found nearthe mouth of the Rfas Baixas (situated in the south-west ofthe coastal area) and in some zones further out to sea (863larvae 10^–2 m^–3) (due to a process of hydrodynamictransport)     

Seasonal dynamics in the abundance of Micromonas pusilla (Prasinophyceae) and its viruses in the Gulf of Naples (Mediterranean Sea)

To assess the role of viruses in the bloom dynamics of Micromonaspusilla in the Gulf of Naples (Mediterranean Sea), variationsof host and virus abundance were followed over one annual cycleand in late winter–spring of three consecutive years.Micromonas pusilla was recorded from autumn to spring, withpeak values up to 6.6 x 10³ cells ml^–1, but was undetectablein summer. Free M.pusilla viruses were detectable in all seasons,with concentrations from 0.02 viruses ml^–1 to 1.9 x 10³viruses ml^–1, exceeding host abundances only in one case.We found a great intraspecific variability in host susceptibilityto viruses present in natural samples, with viral titres rangingover one or two orders of magnitude for the same samples incubatedon different M.pusilla strains. Over the winter–springperiods, a highly dynamic situation was evident, with wide fluctuationsfor both host and virus abundances from one week to another.In some cases, peak host concentrations were accompanied byan increase in viral numbers, whereas in other cases the respectivefluctuations were uncoupled. Although fluctuations of M.pusillaabundance could be influenced by viral infection, there wasno evidence that viruses were able to terminate host blooms.The summer decline of M.pusilla populations did not appear tobe related to the impact of viral infection.     

GROWTH OF JUVENILE BITHYNIA TENTACULATA (PROSOBRANCHIA, BITHYNIIDAE) UNDER DIFFERENT FOOD REGIMES: A LONG-TERM LABORATORY STUDY

The growth of juvenile Bithynia tentaculata (Proso-branchia,Bithyniidae) was measured under controlled laboratory conditionsover 18 months. The animals were fed with different concentrationsof suspended food (Chlamydomonas reinhardii at 2, 000 cells.ml^–1and at 10, 000 cells.ml^–1), solid food (lettuce) and combinationsof both (lettuce with 2, 000 cells.ml^–1 and with 10, 000cells.ml^–1 Chlamydomonas). The growth of all animals wasmeasured weekly, and after 1 years final shell sizes, shelldry weights and ash-free dry weights, as well as soft body dryweights and ash-free dry weights were determined. Survival rateof the animals increased from 20% when fed with 2, 000 algalcells.ml^–1 to 75% with lettuce and 10, 000 cells.ml^–1as food. Final shell sizes and shell weights were not influencedby food, but soft body dry weights were significantly reducedwhen animals were fed on suspended food only. Reproduction (i.e.egg laying) was observed at the end of the second summer whenlettuce (with or without algal addition) was given as food.The ecological consequences of these results are discussed. (Received 7 April 1993; accepted 9 August 1994)     

Two Suppressors, Supprescins A and B, Secreted by a Pea Pathogen, Mycosphaerella pinodes

Two mucin-type glycopeptides that suppressed the productionof pisatin, a phytoalexin of pea, were purified from a pea pathogen,Mycosphaerella pinodes. The structures of Supprescin A (Mr,452) and Supprescin B (Mr, 959) were determined by an analysisof amino acid sequences and ¹³C- and ¹H-NMR. (Received April 22, 1992; Accepted June 16, 1992)