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)     

Phytoplankton distribution and composition off the coast of Galicia (northwest of Spain)

During October 1977, phytoplankton iamples were collected alongwith other hydrographic and biological data from a grid of stationslocated off Galicia (NW of Spain), between the coast and about100 km offshore. Chlorophyll a distribution and phytoplanktoncomposition were studied and related to hydrographic and geographicfeatures of the area. The higher phytoplankton biomasses werefound off the western coast and were conditioned by the presenceof the rias - flooded tectonic valleys of moderate depth functioningas positive estuaries - and the occurrence of coastal upwelling,which allows the injection of nutrient rich water along thebottom of the rias. The qualitative composition of the phytoplanktonreflected principally the influence of the rias but appearedalso to show variability related to the distribution of watermasses. The patterns of circulation of the surface and sub-surfacewaters were likely to reinforce the phytoplankton differencesbetween the northern and western coasts of Galicia.     

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;     

CHROMOSOME NUMBER IN TWO PHENOTYPICALLY DISTINCT POPULATIONS OF LITTORINA SAXATILIS OLIVI, AND IN SPECIMENS OF THE LITTORINA OBTUSATA (L.) SPECIES-COMPLEX

Chromosome numbers counted from embryo cells of the marine gastropodLittorina saxatilis (=L. rudis), were the same, 2n = 34, inpopulations of two different phenotypes from a small area inSweden. Chromosome number in the related species-complex, Littorinaobtusata, could not be determined definitely, but the most adequatefigure seemed to be 2n = 34. (Received 9 September 1982;     

FIELD OBSERVATIONS ON FEEDING OF THE LAND SNAIL HELIX ASPERSA MULLER

Feeding of the land snail Helix aspersa (Müller) was observedat monthly intervals. Three natural populations in Galicia (NW-Spain)were studied. At two sites only a few plants constituted thebulk of the diet and in spring the snails' diet had the highestdiversity (H'). In the third population feeding and distributionof Helix aspersa (Müller) were observed in a small plotwith permanent patches of Urtica dioica. Nearly one half offeeding snails fed upon Urtica dioica. Most of the other observations wereon Mentha suaveolens, Ranunculus repens and Gramineae. The diversity ofthe snails' diet showed seasonal variation with the maximumin the autumn months. Comparison between the availability ofthe different plant species and their contribution to the snails'diet showed that the snails did not eat at random; Urtica dioicawas eaten much more than expected from its occurrence and grasseswere strongly under-represented in the snails' diet. Temporalchanges of availability were significantly correlated with the amountseaten in the case of Urtica, but not for the other food plants.The distribution of the snails in the plot was significantlycorrelated with that of Urtica. Chemical analyses of the foodplants revealed Urtica as the species with the higher protein,ash and calcium contents. The strong preference of Helix aspersafor Urtica dioica could be explained by the value of Urticaas food or by its suitability as habitat for the snails. The largestproportions of green material in the snails' diet occurred inthe spring and juveniles ate more green material than adultsin the three populations. (Received 16 March 1998; accepted 30 November 1998)     

THE BIOMPHALARIA HAVANENSIS COMPLEX (GASTROPODA: PLANORBIDAE) IN CUBA: A MORPHOLOGICAL AND GENETIC STUDY

Conchological, anatomical and genetic characteristics werecompared among several populations of the Biomphalaria havanensis complexfrom Cuba and other localities in the Caribbean region. Two morphometricmeasures (height and diameter) distinguished two closely similarmorphs of the shell. The reproductive system also separated thesemorphs, particularly upon comparison of sizes of the penis sheathand the preputium. The two morphological groups differed in9 to 12 fixed alleles according to population. Further allozymicdata analyzed in the present work confirmed this difference.The results strongly support the assumption that the B. havanensis complexincludes two distinct species: B. havanensis, for which thetype locality is the swampy area near the vicinity of Havana,Cuba and Biomphalaria sp. a species which commonly occurs inCuba and in Dominican Republic. The taxonomic identity of Biomphalariasp. is discussed. (Received 28 January 2000; accepted 15 August 2000)     

THE ROLE OF LYMNAEA AURICULARIA (LINNAEUS) AND LYMNAEA PEREGRA (MULLER) (GASTROPODA: PULMONATA) IN THE TRANSMISSION OF LARVAL DIGENEANS IN THE LOWER THAMES VALLEY

Eleven species of larval digeneans are reported for the firsttime in the UK from the freshwater snail Lymnaea (Radix) auricularia.The latter replaced its congener L. peregra in a gravel pitnear Wraysbury, Berkshire in the Lower Thames Valley and hostedan assemblage of larval digeneans similar to that previouslytransmitted by L peregra. The larval digeneans of L. peregrain small bodies of water in the area were also similar to thosefound in L. auriculania in the gravel pit. This replacementin the role of the host is explained on the basis of morphological,physiological and ecological similarities of the two lymnaeidspecies. (Received 19 February 1992; accepted 27 April 1992)     

CHANGES IN EMISSION SPECTRA OF PHOTOSYNTHETIC PIGMENTS IN VIVO

1. The effects of 3-(4'-chlorophenyl)-1, 1-dimethylurea (CMU)onthe fluorescence of photosynthetic pigments in vivo wereinvestigatedin blue-green, red and brown algae and in isolatedspinach chloroplasts.CMU caused an increase in steady statelevel of fluorescenceof chlorophyll a, but did not influencethe fluorescence ofphycobilins. The spectrum of the fluorescenceincrement hada peak at 685 m/µ and a shoulder at 730–740mµ.These two bands probably arise from chlorophyll a(C_f684) belongingto pigment system II.
2. On excitation of chlorophylla in a red alga, Porphyra yezoensis,a fluorescence band witha peak at 720 mµ was observedbesides a shoulder at 685mµ. The 720 m band is inferredto arise from chlorophylla (probably, C_f-1) in pigment systemI.
3. On addition of CMUto the algal cells, the induction of fluorescencewas modifiedto take a simple time course. The induction wasobserved onlywith respect to the fluorescence of chlorophylla, but not inthe fluorescence of phycobilins. The spectrumof the "transient"fluorescence showed two emission bands ofchlorophyll a at 685mµ and 740 mµ, and was quitesimilar in form tothe spectrum of the CMU-caused increase insteady state fluorescence.
4. These facts were interpreted in terms of the correlation offluorescence of chlorophyll a and the photochemical reactionsof photosynthesis

(Received July 20, 1967; )     

LAND USE AND SUMMER BIRD POPULATIONS IN NORTHWESTERN GALICIA, SPAIN

Summer bird populations were studied in ten sites: two heathlands, two maritime pine Pinus pinaster plantations, one, four, seven and 13-year-old eucalypt Eucalyptus globulus plantations, one climax oak Quercus robur woodland, and a farmland area in northwestern Galicia, Spain. The farmland and oak wood contained the greatest number of species (24 and 17 respectively) while the one and four-year-old eucalypt stands contained the fewest species (four and six respectively). Avian density was highest in the oak wood (93 birds/ 10 ha) and lowest in a heathland site, the four and one-year-old eucalypt stands (26,13, and seven bird/10 ha respectively). The wren was the most widespread and dominant species occurring in all study areas except the one-year-old eucalypt stand. Mean bird species diversity for the four eucalypt stands was significantly lower than mean bird species diversity for the other wooded habitats. The avian communities of the heathlands, maritime pine and eucalypt plantations, in contrast to the oak wood and farmland, show an excessively high dominance of one species. Using avian dominance as a biological index of habitat perturbation suggests that over half the landscape (4000 km²) in northwestern Galicia is suffering from chronic stress. The newest stress to the avifauna in a long history of land exploitation by man is the importation and cultivation on grand scale of eucalypts. Balancing this tendency, traditional, small-scale farming on the mountainous terrain leads to the development of many tiny parcels whose average size is 0.28 ha; this in turn creates much ‘edge’ in hedgerow which serves to maintain a relatively rich avian species diversity in farmland.     

GENETIC VARIATION IN SIX SPECIES OF SACOGLOSSAN OPISTHOBRANCHS

Genetic variation in allozymes of six species of Saco-glossa(Mollusca, Opisthobranchia) from Denmark was studied. Nine enzymesrepresenting 11 loci gave reactions that could be used to calculateallele frequencies. Elysia viridis, Limapontia capitata, L.de-pressa, Ercolania nigra, Alderia modesta and Calliopaea oophagaall showed very great variation both within and between species.Levels of polymorphism varied between 0.5 and 0.8, and levelsof observed heterozygosity were between 0.18 and 0.42. Interspecificidentity of alleles in polymorphic loci was only found betweenthe two species of Limapontia. Even in these two species geneticidentity (I) was very low (0.07) for congeneric species. Theresults are discussed in relation to habitat, fertility, developmenttype and geographic range of the species. (Received 28 February 1990; accepted 26 July 1990)     

准噶尔荒漠早春短命植物的光合特性及生物量分配特点

准噶尔荒漠分布的早春短命植物不仅具有十分独特的生物学特点,而且在荒漠植物群落演替、物种多样性维持及土壤改良与防治水土流失等方面具有重要的生态学价值。该文运用Li-6400开放式气体交换光合作用测定系统,对分布于准噶尔荒漠的16种早春短命植物生长盛期的净光合速率(P_n)、蒸腾速率(T_r)、水分利用效率(WUE)等特征进行了测定,并对其中7种植物与生长相关的生物量分配特征进行了分析。结果表明:1)16种植物的最大P_n、 最大T_r及WUE分别为8.07~35.96 μmol CO₂·m^-2·s^-1、3.16~29.64 mmol H₂O·m^-2·s^-1、0.54~4.26 μmol CO₂·mmol^-1H₂O;种间最大P_n与最大气孔导度(Stomatal conductance, G_s)之间存在正相关关系,其相关系数为0.77(p<0.05),线性回归斜率为26.36 μmol·mmol^-1;从光合速率对胞间CO₂浓度及光量子通量密度的响应曲线来看,这类植物的表观CO₂补偿点均在4~5 Pa之间(28~30 ℃),表观羧化效率为0.64~1.86 μmol CO₂·m^-2·s^-1·Pa^-1,表观量子效率为0.05~0.06。2)从生物量分配来看,所测植物的个体生物量为0.05~0.39 g;单株总叶面积为 3.24~51.40 cm²;单位叶面积干重为0.40~0.77 g·m^-2,根在总生物量中所占比例为5.72%~19.43%,单株叶面积比在2.92~9.00 m²·kg^-1之间。种间根所占生物量的比与对应的WUE之间的比较分析结果表明,二者之间存在显著的正相关关系,其相关系数r为0.93(p<0.01)。这些结果表明,所观测的早春短命植物具有典型的C₃植物特征,相比其它类型的荒漠植物具有较高的单位叶面积P_n、高T_r及低WUE,并且在生长发育过程中表现出很低的根/地上生物量比、较高的叶面积比和单位叶面积干重,说明它们具有相对高的生长速率,这与其生长发育节律相一致,反映了它们与准噶尔荒漠环境相适应的特点。     

An Analysis of Seed Development in Pisum sativum: IV. COTYLEDON CELL POPULATIONS IN VIVO AND IN VITRO

A method for quantifying changes in the cell population of Pisumsativum cotyledons during development is described. The methodis based on determining the frequency distribution for cellarea following the random sampling of a single-cell suspensionof cotyledon cells. The population profile of these cells changedprogressively and systematically from a single population, similarin size to meristematic cells, found in embryos less than 3.0mg in fresh weight, to a bimodal population in embryos greaterthan 100 mg fresh weight. This method was used to compare embryosof similar size from two genotypes near-isogenic except forgenes at the r locus. No significant differences were foundbetween the cell population profiles of embryos up to 30 mgfresh weight. However, a significant difference was found betweenembryos with fresh weights of 100 mg, the wrinkled (rr) linehaving a higher mean and maximum cell area (2 951 µm²and 9 240 µm² respectively) than the round (RR) line (2591µm²and 6470 µm²respectively). Comparisons were alsomade between cotyledon cell populations from round (RR) embryosgrown in vivo and in vitro. The most obvious differences werethe higher mean and maximum cell size of the large cell populationof in vitro grown embryos which were twice those found in vivo.Embryos grown to either 30 mg or 100 mg fresh weight in vitrohad a much greater proportion of large cells in the populationwith a corresponding reduction in total cotyledon cell number,compared with similar sized embryos grown in vivo. These data suggest that comparisons between different genotypes,or, between cultured and in vivoembryos, based on morphologicalsimilarities between embryos, may be invalid and subject tomisinterpretation. Key words: Pea, seed development, cell population     

DISTRIBUTION AND ABUNDANCE OF GYMNOSOMATA (GASTROPODA: OPISTHOBRANCHIA) IN THE SOUTHWEST ATLANTIC

The distribution and abundance of gymnosome gastropods in theArgentine Sea and Brazil—Malvinas Confluence during 1978–1979and 1988 were studied. The collections analyzed included 768quantitative samples obtained between 48°W and the coast,and from 35°S to 55°S. Two species were found. Spongiobranchaeaaustralis was the most frequent and abundant (up to 730 per1000 m3); its presence in the area was associated with the coreof the Malvinas Current. Clione antarctica was less abundant(maximum abundance: 230 per 1000 m³) and was also associatedwith the Malvinas Current. The geographic ranges of both speciesin the area are wider than previously described. Since the rangeof S. australis in the area extends far from the range of itsprey Clio, it is not clear whether S. australis can feed onthe thecosomatous pteropod Limacina (and not only on Clio, asdescribed in the bibliography) or it starves in that area. Duringthe 1978–1979 annual cycle, the abundance of both speciesfollowed neither the abundance patterns of their prey nor ofthe total zooplankton, and differed from each other. The residencetime of swarms of both gymnosomes were shorter than one month.As a general pattern, the aggregates are rapidly transportednorthward by the Malvinas Current and also penetrate the outershelf water, but they remain there only during a short periodand cannot preclude the final expatriation. So, the abundanceof gymnosomes in the area depends on passive migration morethan intrinsic population factors. (Received 9 July 1997; accepted 15 December 1997)     

DISTRIBUTION OF MOLLUSCS ACROSS A PNEUMATOPHORE BOUNDARY IN A SMALL BAY IN NORTHWESTERN AUSTRALIA

The number of species, total density and total biomass of molluscswere examined for 50 m either side of an Avicennia pneumatophoreboundary in the Bay of Rest, North West Cape, Western Australia(22°18'S; 114° 08'E). Two mollusc assemblages were found,separated almost exactly at the pneumatophore boundary. Themudflat association had more species of molluscs but a lowertotal density and total biomass than the assemblage in the Avicenniazone. Stations among pneumatophores on the seaward fringe ofthe Avicennia zone were more diverse and had a greater densityand biomass than stations among the trees. Possible reasonsfor the pneumatophore area having a higher density and biomassof molluscs than the adjacent mudflat and tree zones are discussed. (Received 18 June 1985;     

SPERM AND SPERMIOGENIC ULTRASTRUCTURE IN THE MATHILDIDAE WITH A REVIEW OF SPERM MORPHOLOGY AND ITS SYSTEMATIC IMPORTANCE IN THE ARCHITECTONICOIDEA (GASTROPODA)

The ultrastructure of spermiogenesis and spermatozoa is examinedfor the first time in the heterogastropod family Mathildidae(Mathilda brevicula Bavay and Mathilda sp.). Mathildid spermatozoaexhibit the following features: (1) an ovoid acrosomal vesicleshowing curved dense layers basally and underlain by a thincurved plate; (2) a solid, rod-shaped nucleus showing a shallowbasal invagination (nucleus helically keeled in Mathilda sp.);(3) a midpiece composed of a 9+2 axoneme, 9 thick and periodicallybanded coarse fibres (associated with the axonemal doublets)and a continuous mitochondrial derivative; (5) glyco-gen piececomposed of the axoneme surrounded by dense granules; (6) andend piece (paddle-shaped terminally). Results of the study demonstratethat mathildids share the same key sperm and spermi-ogenic featuresobserved in the Architectonicidae. The monophyly of the Architectonicoidea,established by previous authors on anatomical grounds, is thereforeconfirmed using sperm morphology. Spermatozoa of the two mathildidsinvestigated lack the periodically banded midpiece structuresseen in investigated species of Architectonica (A. pcrspectiva(Linnaeus), A. perdix (Hinds)), Heliacus (H. (Heliacus) variegatus(Gmelin)) and Pseudotorinia (P. laseronorum (Iredale)) therebyresembling most closely the spermatozoaof Philippia lutea (Lamarck)and Psilaxis oxytropis (A. Adams) which also lack suchbandedstructures. Given the widely accepted primitive status of theMathildidae within the Architectonicoidea, the genera Philippiaand Psilaxis may prove to be relatively basal rather than advancedgenera within the Architectonicidae. Thi: view needs to be testedby examination of sperm morphology in other genera of the Architectonicidaeand also the basal mathildid genus Tuba sensu lato (= Gegania+ Tubena). Such information will be vital in any future cladisticstudy of the Architectonicoidea. (Received 16 June 1994; accepted 6 February 1995)     

THE GROWTH OF PELTODORIS ATROMACULATA BERGH, 1880 (GASTROPODA: NUDIBRANCHIA) IN THE LABORATORY

The growth of Peltodons atromaculata Bergh, 1880, measured astotal dorsal body area, was followed in the laboratory for 15months. The growth of dorsal brown patches was compared to thetotal area of the mantle, and was shown to be approximatelyconstant over time in the different animals. This numericalapproach can be useful to quantify the body pigmentation clinepreviously described for Mediterranean specimens. P atromaculatahas an annual life-cycle in the laboratory, reaching its maximumsize before opposition. Post-spawning mortality followed a decreasein size for all specimens. Mantle margin autotoray in P atromaculataseems not to be related to defence against predation, but itis a process that takes place before death in laboratory. (Received 1 December 1994; accepted 28 April 1995)     

SPATIOTEMPORAL DISTRIBUTIONAL PATTERNS OF BULINUS ROHLFSI (CLESSIN), BULINUS FORSKALI (EHRENBERG) AND BULINUS SENEGALENSIS MULLER IN NEWLY-IRRIGATED AREAS IN NORTHERN NIGERIA

Over a 16 month period, monthly net samples of aquatic snailswere collected from 30 sites within distributary canals anddrains in a newly-irrigated area of the South Chad IrrigationProject, Borno State, northern Nigeria. Initial colonizationin distributary canals was at the blind ends where bulrusheshad become established, the colonising species being Bulinusforskali and B. rohlfsi. These two species also invaded thedrains where B. senegalensis occurred during the rains. In aconcurrent study, weekly Typha-leaf mat samples of B. rohlfsiwere collected from three sites in a distributary canal anddata on changes in population structure, density and reproductiveactivity were obtained. Patterns of colonization are discussedin relation to the probable origins of the snails, their modesof dispersal and habitat preferences. Population changes inB. rohlfsi are considered in relation to environmental factors.The potential for other planorbids to eventually invade thearea is also considered. ^*Present address: Department of Biological Sciences, BayeroUniversity, P.M.B. 3011, Kano, Nigeria (Received 3 July 1983;     

EFFECT OF AMINO ACID IMBALANCE IN ARTIFICIAL DIETS ON FOOD CHOICE AND FEEDING RATES IN TWO SPECIES OF TERRESTRIAL SNAILS, CEPAEA NEMORALIS AND ACHATINA FULICA

Postingestive response to dietary imbalance of amino acids wasstudied in two species of terrestrial pulmonate gastropods Cepaeanemoralis and Achatina fulica using agar-based chemical diets.Both species showed preference responses to an experimentaldiet complete in all nutrients, and aversive responses to experimentaldiets containing excesses of methionine (in concentrations 1-10%dry wt of diet). Aversion to methionine was stronger in Achatinathan in Cepaea. One day's experience on a particular diet didnot significantly affect an animal's subsequent feeding responseon the same or different diets. What appeared to be more importantin influencing food choice in both species was day-to-day contactwith a given diet. (Received 7 March 1988; accepted 4 May 1988)     

A Rapid Method for the Determination of the Leaf Area of Oxalis corniculata L. and Tephrosia purpurea (Linn.) pers.

A rapid simple method has been described for the determinationof leaf area of Oxalis corniculata L. (Oxalidaceae) and Tephrosiapurpurea (Linn.) pers. (Leguminoseae) by evaluating area = a²x0.866and a²x0.335 respectively for the two plants, where a representsa single linear measurement. The relation has been derived afterintegrating the equation of the curve r² = a² cos 2 coveringthe area of each leaflet. Areas of a large number of leaflets have been determined withthe help of two methods (1) Planimeter method, (2) Evaluationmethod. The significance of the difference between the two valuesfor a particular leaf has been statistically examined and itappears that the former method can be replaced by the latterin the case of these plants.