VARIATION IN THE OCCURRENCE OF ABNORMAL EMBRYOS IN FEMALES OF THE INTERTIDAL GASTROPOD LITTORINA SAXATILIS OLIVI

The incidence of abnormally developed embryos within the brood-pouchof female L. saxatilis was very variable, ranging from 0–100%of embryos being abnormal. A minor part of the total variationwas attributed to between-shore variation, while 82% reflectedwithin sample differences between females. Possible factorsresponsible for the variation in embryo abnormality shown bythis and other investigations, are discussed and it is concludedthat genetic rather than non-genetic factors are important. (Received 8 November 1983;     

THE GENETIC RELATIONSHIPS OF THREE TAXA IN THE LITTORINA SAXATILIS SPECIES COMPLEX (PROSOBRANCHIA: LITTORINIDAE)

Three species in the Littorina saxatilis complex (the ovoviviparousL. saxatilis and the two oviparous species L. arcana and L.nigrolineata) were screened for the products of up to 22 lociusing gel elec-trophoresis. Analysis of allele frequencies andderived genetic distances showed that, with rare exceptionsin L. saxatilis and L. arcana, conspecific populations clusteredtogether. Sympatric pairs of populations showed significantdifferentiation at many polymorphic loci. The results confirmedthe biological reality of the three taxa, and did not suggestthe existence of any previously unrecognized species. The speciesare genetically closely related to each other, with Nei geneticdistances ranging from 0.035 to 0.083. (Received 24 October 1989; accepted 18 April 1990)     

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)     

DISTRIBUTION AND ABUNDANCE OF HYDROBIA ULVAE (PENNANT) IN THE LOWER MEDWAY ESTUARY, KENT

Measurements of densities and distribution of populations ofH. ulvae were made in the lower Medway estuaryduring the period1969–1975, together with measurements of salinity, substrateparticle size and macrophyte distribution. Results indicatedthat sheltered siteswere more favourable to the snail as shownby higher population density and greater shell size. ^*Current address: Southern Water Authority, Maidstone, Kent (Received 20 May 1979;     

RANDOM AMPLIFIED POLYMORPHIC DNA (RAPD) MARKERS REVEAL CROSS-FERTILISATION IN BIOMPHALARIA GLABRATA (PULMONATA: BASOMMATOPHORA)

The freshwater, schistosome-transmitting snail, Biomphalariaglabrata is a simultaneous hermaphrodite which can reproduceby both cross-and selffertilisation, but despite the medicalimportance of this species, little is known about the matingstrategies adopted by wild-type individuals from natural populations.The identification of cross-fertilised progeny is a prerequisitefor both evolutionary studies of the relative fitness of differentreproductive strategies, and for the production of exclusivelyoutcrossed F₁ populations for genetic mapping of biologicallyimportant phenotypes, most notably, resistance to schistosomeinfection. In this study, parents, offspring and ‘syntheticoffspring’ (controls) from four families of B. glabratarecently derived from wild populations were analysed using theRandom Amplified Polymorphic DNA (RAPD) assay. RAPDs were usedbecause they reveal more genetic variation, require less tissue(juvenile snails were only 4–5 mm diameter) than proteinelectrophoresis, are less laborious than other molecular analyses,and do not require sequence data. Seven of the 19 arbitrarysequence, oligonucleotide primers used gave bands that werepolymorophic between pairs of parent snails. Scoring the offspringfor the presence/absence of these polymorphic bands showed thatall the offspring tested were the products of cross-fertilisation.This study provides the first demonstration of the applicabilityof the RAPD technique to an analysis of fertilisation in wild-typeB. glabrata. (Received 20 December 1994; accepted 27 March 1995)     

RECRUITMENT AND LIFE SPAN OF TWO NATURAL MUSSEL POPULATIONS PERNA PERNA(LINNAEUS) AND MYTILUS GALLOPROVINCIALIS (LAMARCK) FROM THE ALGERIAN COAST

Coexisting populations of the mussels, Perna perna and Mytilusgalloprovincialis, were monitored at two sites on the NorthAfrican coast, east of Algiers, over a five year period (1985–1989).While spatfalls were observed throughout the year, only themajor spring-summer recruitment, which occurred during favourableweather conditions, contributed to the renewal of both musselspecies at both sites. Very high densities (>10, 000 ind.m^–2) were observed at both sites, but the mussel bedswere composed principally of young and small specimens due toharvesting of the largest animals for use as bait and for humanconsumption. The maximal length observed was 75 mm in P. pernaand 49 mm in M. galloprovincialis. The life span of the specieswas low, 12–24 months in P. perna and 11–28 monthsin M. galloprovincialis. This survey showed that M. galloprovincialisbecame dominant in both mussel beds due to its resistance todisturbance by human activities. (Received 5 January 1995; accepted 18 April 1995)     

PHENOTYPIC DIFFERENTIATION IN LITTORINA SAXATILIS OLIVI (MOLLUSCA, PROSOBRANCHIA) IN A SMALL AREA ON THE SWEDISH WEST COAST

The Littorina saxatilis species-complex exhibits two distinctmorphs in the area investigated. Differences in shell morphologyand number of penial glands are statistically significant (P<0.02)between populations from exposed and sheltered habitats. However,in intermediate environments intermediate specimens as wellas typical specimens of both morphs are found. The differencesare considered intraspecific and at least partly geneticallydetermined, and possible selection pressures responsible arediscussed. (Received 8 February 1981;     

Effects of temperature and salinity on the growth of the red tide flagellates Heterocapsa circularisquama (Dinophyceae) and Chattonella verruculosa (Raphidophyceae)

Growth responses of the red tide flagellates, Heterocapsa circularisquama(Dinophyceae) and Chattonella verruculosa (Raphidophyceae),were examined with 36 different combinations of temperature(5–30°C) and salinity (10–35 PSU). Heterocapsacircularisquama did not grow at or below a temperature of 10°C.The maximum growth rate of H.circularisquama (1.3 divisionsday^–1) was obtained with a combination of 30°C and30 PSU. In contrast, C. verruculosa did not grow at 10 PSU andat temperatures of 25°C or more. The maximum growth rateof C. verruculosa (1.74 divisions day^–1) was obtainedwith a combination of 15°C and 25 PSU. A significant temperature-salinityinteraction on growth was found by factorial analysis. Basedon the physiological characteristics obtained in the presentstudy, these novel flagellates have a potential for future outbreaksof red tides in pre viously unaffected waters.     

SIZE-ASSORTATIVE MATING IN A NATURAL POPULATION OF VIVIPARUS ATER (GASTROPODA: PROSOBRANCHIA) IN LAKE ZURICH, SWITZERLAND

The number of mating pairs, the size of the mating partners,and the distribution of individuals of Vivi-parus ater on agrid in Lake Zürich were recorded during one breeding seasonin 1990. There was positive assortative mating with respectto shell size. The proportion of copulating individuals rangedfrom 1% to 6% (average 3%) of the active population at any onetime. Individual snails copulated 60 times on average from Apriluntil November. Snails were abundant and copulated in shallowwater close to the shore in Spring. They moved towards deeperareas in Autumn. V. ater copulated on all substrates at anydepth (1–9 m)of the grid. The spatial distribution ofcopulations throughout the summer reflected the pattern of snailabundance. (Received 29 January 1993; accepted 14 November 1994)     

The effect of salinity and temperature on the larval development of Mithrax caribbaeus Rathbun, 1920 (Brachyura: Majidae) reared in the laboratory

Larvae of Mithrax caribbaeus were reared in the laboratoryin a factorial experiment employing three temperatures (22,25 and 28°C) and three salinities (32, 35 and 38). Survivaland duration of larval stages were recorded. Ovigerous femalesof M.caribbaeus were collected from the south-eastern coastof Margarita Island, Venezuela, and maintained in individualaquaria until hatching. Eggs from three of the females hatchedin the laboratory. Larvae from each hatching were subdividedinto groups of 10 and reared in plastic bowls containing 200ml filtered and UV-irradiated sea water at different temperature–salinitycombinations. Larvae were transferred daily to clean bowls withnewly hatched Artemia nauplii, and the number of molts and mortalitywithin each bowl was recorded. Complete larval development ofM.caribbaeus occurred under all experimental conditions. Salinityhad the greatest effect on percentage survival of each larvalstage and complete development up to the first crab stage. Thefirst zoeal stage exhibited the highest survival rate. Maximumsurvival for this stage occurred at 25°C, 32–35. Survivalin the second zoeal stage and the megalopa was affected onlyby salinity. Effects of temperature and salinity on survivaldecreased with advance in development. The duration of the twozoeal stages, the megalopa, and development to the first crabstage showed a gradual reduction with increasing temperature.Salinity showed an effect on the duration of zoeal stages butnot on the megalopal stage. Development from hatching to thefirst crab stage required 8–18 days, depending on thetemperature–salinity combination, and was inversely relatedto temperature, averaging 14.3 days at 22°C, 11.8 days at25°C and 9.2 days at 28°C.     

Effects of growth medium, temperature, salinity and seawater source on the growth of Gymnodinium catenatum (Dinophyceae) from Bahia Concepcion, Gulf of California, Mexico

Laboratory studies were performed to determine the effect oftemperature, salinity, seawater sources and culture media onthe vegetative growth of clonal cultures of Gymnodinium catenatumisolated from Bahía Concepción, Mexico. Theseisolates were heterothallic and isogamous. Exponential growthrates of G. catenatum in f/2 with different selenium concentrationsand soil extract and GSe media were moderate. Maximum cell yieldswere obtained in GSe and f/2 media with selenium (10^–8and 10^–7 M), while in f/2 medium with soil extract cellyields were considerably lower. The highest percentage of longchains was found in f/2 media supplied with selenium (10^–8M). The optimal temperature range for growth was 11.5–30°C,with the highest growth rates between 21 and 29°C. The rangeof salinity tolerated by G. catenatum changed with seawatersource. With seawater from Vineyard Sound (Massachusetts, USA),G. catenatum grew at salinities from 15 to 36, with an optimalgrowth rate obtained at salinities between 26 and 30. With seawaterfrom Bahía Concepción, this species toleratedsalinities from 25 to 40, with optimal growth at salinitiesbetween 28 and 38. Ecophysiological measurements reported hereare consistent with the environment of the bay, which has limitedinput of humic materials from runoff and high salinity and temperature.These data, when viewed with data from studies of globally distributedG. catenatum, demonstrate the ability of this species to livein a broad array of habitats.     

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)     

AGE AND GROWTH OF LITHOPHAGA LITHOPHAGA (LINNAEUS, 1758) (BIVALVIA: MYTILIDAE), BASED ON ANNUAL GROWTH LINES IN THE SHELL

The life span of Lithophaga lithophaga was found to be >54 years when the annual growth lines in longitudinal shellsections were counted. The age determination was confirmed bya) length frequency histograms, b) the time taken for the formationof annual and reproduction rings and c) by determining the agein different parts of the shell. The age of individuals of thesame length varies, for example, individuals with a length of5.0 ± 0.2 cm range in age from 18–36 years. Theoldest individuals were found at depths of 1–5 m. Maximumgrowth (75%) was observed from the end of spring to the beginningof summer. The increase in length of the borehole, which was1.5 times greater than the length of L. lithophaga, was continuousand occurred at a faster rate in winter. Parameters, such as,shell length, age, axes, the occurrence of abnormal, white andpearlcontaining forms and wetflesh weight varied significantlywith depth. There was no variation in the ratio of boreholevolume/shell volume. On the basis of the above parameters, andalso the population density, each depth at which samples werecollected, was graded. Depths of 2–4 m were found to bethe most suitable for growth and habitation. Depths of 0–1m were most inhospitable due to strong wave action and the directeffect of the atmosphere. (Received 15 August 1994; accepted 17 March 1995)     

DISTRIBUTION AND POPULATION DYNAMICS OF THREE POPULATIONS OF SIPHONARIA ON ROCKY INTERTIDAL SHORES IN HONG KONG

The pulmonate limpets Siphonaria japonica and Siphonana siriusoccur over a wide range of local habitat types in terms of exposureto wave action and salinity. This is a study of these two specieson three different shore types in Hong Kong, ranging from anextremely exposed, high salinity (32–35) shore at Caped'Aguilar to a sheltered, low salinity (16–33) shore atTai Lam Chung. Both species are restricted to the low shore,year round. S. japonica is a winter breeder and recruitmentoccurred between October and January. The recruitment of S.sirius could not be recognised from the size-frequency histograms.The algal standing crop at Tai Lam Chung was higher than atWu Kwai Sha during the winter period, i.e., between Octoberand April. Seasonal fluctuations in growth rate were recordedfor both Siphonaria species with the time of fastest growthoccurring in winter. S. japonica grew faster at Tai Lam Chungthan at Wu Kwai Sha. Food availability is thought to be an importantfactor affecting growth. (Received 17 September 1993; accepted 16 June 1994)     

Effect of Salinity on Growth, Nodulation and Nitrogen Yield of Chickpea (Cicer arietinum L.)

Chickpea cultivar ILC 482 was inoculated with salt-tolerantRhizobium strain Ch191 in solution culture with different saltconcentrations added either immediately with inoculation or5 d later. The inhibitory effect of salinity on nodulation ofchickpea occurred at 40 dS m^–1 (34.2 mol m^–3 NaCl)and nodulation was completely inhibited at 7 dS m^–1 (61.6mol m^–3 NaCl); the plants died at 8 dS m^–1 (71.8mol m^–3 NaCl). Chickpea cultivar ILC 482 inoculated with Rhizobium strain Ch191^spcstrwas grown in two pot experiments and irrigated with saline water.Salinity (NaCl equivalent to 1–4 dS m^–1) significantlydecreased shoot and root dry weight, total nodule number perplant, nodule weight and average nodule weight. The resultsindicate that Rhizobium strain Ch191 forms an infective andeffective symbiosis with chickpea under saline and non-salineconditions; this legume was more salt-sensitive compared tothe rhizobia, the roots were more sensitive than the shoots,and N₂ fixation was more sensitive to salinity than plant growth. Key words: Cicer arietinum, nodulation, N₂ fixation, Rhizobium, salinity     

Growth and Osmoregulation of Chaetoceros muelleri in Relation to Salinity

The growth and osmoregulation of Chaetoceros muelleri Lemmermann(Bacillariophyceae) were investigated as a function of salinity.This centric diatom grew well over a wide range of salinityand required concentrations of NaCl above 10 mM for growth.Using gas chromatography- mass spectroscopy (GC-MS) analysisof cell extracts, we demonstrated that the alga contains anisomer of cyclohexanetetrol. The level of this isomer increasedwith increasing salinity. Levels of free amino acids also increasedwith increasing salinity, and quantitative determination withan amino acid analyzer revealed that the level of glutamic acidincreased the most with increases in salinity. Levels of intracellularK⁺ and Cl^– also increased significantly with increasesin salinity. Thus, in C. muelleri, not only organic solutessuch as the cyclohexanetetrol isomer and glutamic acid, butalso inorganic solutes such as K⁺ and Cl^– contribute toosmoregulation. (Received November 7, 1994; Accepted April 10, 1995)     

MORPHOLOGICAL DIVERGENCE AND EVIDENCE FOR REPRODUCTIVE ISOLATION IN LITTORINA SAXATILIS(OLIVI) IN NORTHEAST ENGLAND

Current work at Old Peak (Ravenscar) on the northeast coastof England indicates that boulder-dwelling Lutonna saxatilis(Olvi) comprise at least two distinct forms, inhabiting high-and mid-shore boulders Using multivariate morphometrics we showthat these forms are significantly different in shape. Rareintermediates between these two distinct forms were occasionallyfound, usually with the low shore animals The two forms showdifferent reproductive strategies. High shore females (L. saxatilisH) mature at a smaller size and produce a smaller number oflarge eggs giving rise to large crawlaways The mid-shore form(L. saxatilis M) matures at a larger size and produces a largenumber of small eggs which give rise to small crawlaways. Anovel observation is that intermediate females (L. saxatilisI) contain eggs of both sizes, giving rise to a bimodal distributionof egg sizes within the brood pouch. The usual incidence ofabortion (observed in H and M forms) is Very low (<1%) However,in the intermediates the large eggs showed a high incidenceof abortion (about 60%) and the incidence of abortion in thesmall eggs was also increased (about 30%) Thus there appearsto be a partial reproductive barrier between the two forms,presumably resulting in reduced fitness due in the intermediatesto reproductive dysfunction. These findings extend to othershores in the region, over total distance of about 66 km. Thefacts are suggestive of a hitherto unrecognised reproductivebarrier with L. saxatilis, the nature and strength of whichis under investigation ^*Present address: University College Scarborough. Filey Road.Scarborough Yo11 3AZ. (Received 12 June 1995; accepted 15 September 1995)     

FLYING SNAILS--HOW FAR CAN TRUNCATELLINA (PULMONATA: VERTIGINIDAE) BE BLOWN OVER THE SEA?

With populations of land snails of very small size like Vertiginidae,questions have arisen as to whether populations of relativelydistant islands in archipelagos are really isolated from eachother. Apart from other flight agencies, airborne transportof loose specimens is not improbable in stormy weather conditions.Currently, mechanisms of wind-borne transport of sand particlesover short and long distances have been intensively studied.The results are available in the literature on sediments, allowingthe calculation of probable flight distances for particles insuspension. For living snails of the Aegean species Truncatel-lina rothi,an average fall velocity of 2.6–2.7 m s^–1 has beendetermined in experiments under laboratory conditions. Applyingthese results, Truncatellina living on an island at 100 m altitudeand close to the coast could be transported up to several kilometersin heavy storms, which are not uncommon in the Aegean archipelago(Greece). This would imply that many of the Aegean islands arenot effectively isolated for minute snail species, and thatgenetic interchange between island populations is probably frequent. (Received 3 April 1996; accepted 27 January 1997)     

Growth Characteristics and Substrate Specificity of Aerobic Photosynthetic Bacterium, Erythrobacter Sp. (OCh 114)

Optimal growth conditions and substrate specificity of the aerobicphotosynthetic bacterium, Erythrobacter sp. (OCh 114), wereinvestigated. Erythrobacter utilized 19 out of 26 substratestested, including several sugars and amino acids. Glycerol andlactate were the most effective as electron donors or carbonsources. Maximum growth was obtained at a salinity of about25, pH 8–9 and temperature 28°C in a glycerol-enrichedmedium. A suitable growth medium for Erythrobacter sp. (OCh114) is proposed. (Received October 18, 1985; Accepted January 10, 1986)     

The Variability of Organs Differentially Involved in Pollination, and Correlations of Traits in Genisteae (Leguminosae: Papilionoideae)

Size differences in organs involved to varying degrees in pollenexchange (standard and keel petals, calyx, pedicel and inflorescencestem diameter), together with correlations among these traits,were investigated at both the intraspecific and interspecificlevels in populations of 15 southern Spanish species of thepapilionoid legume tribe Genisteae. Characteristics less relatedto pollination (e.g. pedicel length and stem diameter) wereroughly twice as variable between individuals as petal or calyxdimensions. The coefficients of variation were in the range16–19%vs. 7–10%, respectively. Standard and keelpetal size varied in parallel, not only in conspecific individualsbut also across species and genera, suggesting a tight developmentalrelationship between these organs and a low potential for evolutionarymodification. The remaining characteristics covaried in differentways within and between species and thus appeared much lessmutually constrained (particularly so for calyx size). Multivariateanalyses of variance revealed significant population divergencein five out of six species. Overall, 28% of all variation inflower size occurred among populations and 72% within populations,but the proportion of variance accounted for by population membershipvaried extensively across species (from 1 to 64%) and was highestin two selfing annuals (Lupinus). Outcrossing perennials mayshow either high (Stauracanthus, Genista) or low (Cytisus) populationdifferentiation. In addition to contributing to the increasingamount of data on quantitative floral variation in plants, resultsof this study may help understand how pleiotropic effects limitthe evolutionary modification of some flower traits more thanothers in diverse plant groups. Copyright 2001 Annals of BotanyCompany Calyx, corolla, Genisteae, legumes, shrub, population divergence, Mediterranean, pollination, individual variation