Influence of food concentration on the physiological energetics and growth ofOstrea edulis larvae

Feeding, respiration and growth rates of oyster (Ostrea edulis L.) larvae reared at five food levels were measured throughout the entire larval period. Energy budgets were derived as a function of alga (Isochrysis galbana Parke) food concentration. Ingestion rate (IR, cells h^-1) and oxygen consumption rate ( , nl h^-1) were almost isometric functions of larval size [ash-free dry weight, (AFDW, g)], characterized by the equations: IR=803.9 AFDW^1.13 and =4.85 AFDW^1.09. Ingested ration was directly correlated to cell concentration up to a maximum at 200 cells l^-1, with further increases failing to support higher ingestion rates. Likewise, growth rate linearly increased with food ration up to 100 cells l^-1 (max. growth efficiency,K ₁=25%) and reached a maximum at 200 cells l^-1 (growth rate=5.6 m d^-1), with further increases in food not supporting significantly faster growth. Maintenance ration was 2 to 3% daily dry weight (DW); optimum ration increased during larval development from 5 to 20% DW; maximum ration was 20% DW. During larval rearing, an increasing feeding schedule of 50, 100 and 200 cells l^-1 from Days 0, 5 and 10, respectively, is recommended.     

Physiological responses of Mytilus edulis and Cardium edule to aerial exposure

Physiological responses of two bivalves (Mytilus edulis L. and Cardium edule L.) to intertidal conditions were studied. Specimens were collected from S. W. England in autumn/winter, 1980, and acclimatized to either intertidal or subtidal regimes before measurement of rates of heat dissipation and oxygen uptake during 5 h of air exposure, and rates of , particle clearance, ammonia excretion, and food-absorption efficiency during 7 h of reimmersion. Subtidal individuals were either intermittently or continuously fed in order to distinguish the effects of periodic food supply from the effects of air exposure. Specimens of M. edulis had low aerial rates of (14 to 20% of aquatic rate), and was greater than the energy equivalent of , indicating that they were largely anaerobic. In contrast, C. edule air-gaped and had higher aerial rates of and (50 to 75% of aquatic rate). There were behavioural and metabolic differences in the responses of intertidally and subtidally acclimatized mussels and cockles to air exposure. Intertidal individuals of both species were more quiescent, had lower aerial rates of and , and showed a conditioned response at the expected time of reimmersion. The reduction in aerial rate of was an energy-saving mechanism and the payment of the oxygen-debt within 2 h of reimmersion represented a significant cost. The heat increment associated with feeding and digestion was estimated as 15 to 17% of the oxygen uptake by M. edulis during all stages of recovery. M. edulis adapted to the intertidal regime by reducing its time-averaged aerial and aquatic rates of ammonia excretion. In contrast, C. edule maintained a high aerial and aquatic rate of ammonia excretion. The clearance rates of M. edulis recovered rapidly (0.5 to 1.5 h) following reimmersion, whereas those of C. edule recovered more slowly, particularly for the subtidal individuals following acute exposure (>4 h). There was no evidence of increased clearance rate or absorption efficiency by intertidal individuals to compensate for the loss of feeding time. Intertidally acclimatized individuals of M. edulis and C. edule had more energy available for growth (scope for growth) integrated over a 12 h period and higher growth efficiencies than subtidal individuals subjected to acute air exposure and intermittent feeding regimes. This was the result of reduced aerial and aquatic rates of energy expenditure, a relatively small cost in terms of the payment of oxygen-debt and a rapid recovery of clearance rate following reimmersion.     

Bacterial associations in the teredo Bankia australis (Lamellibranchia: Mollusca)

Electron microscope examination of the so-called Gland of Deshayes in the teredos Bankia australis and related species has revealed that this structure is not a glandular tissue, but represents associations of bacteria.     

Does displacement of spawning time occur in the sibling species Cerastoderma edule and C. lamarcki?

The spawning cycles of the sibling species Cerastoderma edule (L.) and C. lamarcki (Reeve) were studied in allopatric and sympatric Danish populations from 1978–1980. The results do not support earlier findings of reproductive character displacement in sympatric populations of the two species. New records of hybrid formation and intermediate forms are presented and discussed.     

Elemental composition (C,N,H) in larval and crab-1 stages of Pagurus bernhardus (Decapoda,Paguridae) and Carcinus maenas (Decapoda,Portunidae)

Analyses of individual content of carbon (C), nitrogen (N), and hydrogen (H) were carried out for all larval stages of Pagurus bernhardus and Carcinus maenas, and for newly metamorphosed crabs. Maximum range in total larval development is 12.8 to 165.8 g C, 3.2 to 35.1 g N, and 1.9 to 24.9 g H in P. bernhardus and 3.1 to 43.2 g C, 0.7 to 10.1 g N, and 0.4 to 6.3 g H in C. maenas. From these data energy equivalents were calculated. Maximum range in total larval life is 0.43 to 6.38 J ind. ^-1 in P. bernhardus and 0.1 to 1.49 J ind. ^-1 in C. maenas. There is a 32.4% mean loss of energy in P. bernhardus megalopa development; this seems to describe the normal developmental pattern in this stage. Biomass was determined as fresh and dry weight respectively. Individual dry weight is about 3.6 to 5.6 times higher in P. bernhardus (44 to 340 g) than in C. maenas (12 to 93 g) larvae.Contribution to research project Experimentelle marine Ökosystemanalyse sponsored by Bundesministerium für Forschung und Technologie, Bonn (Grant No. MFU-0328/1)     

Effect of inhibitors of carbonic anhydrase activity on photosynthesis in the red alga Soliera filiformis (Gigartinales: Rhodophyta)

The effect of light intensity, pH and carbonic anhydrase (CA) inhibitors on photosynthesis of the red marine macroalgae Solieria filiformis (Kützing) Gabrielson, collected from Taliarte (Gran Canaria, Canary Islands) in 1991, has been investigated. Plants taken from the sea (wild phenotype) developed spherical morphology (ball phenotype) after 2 mo culture in aerated tanks. The photosynthetic oxygen evolution in the wild phenotype was saturated at 100 mol photons m^-2s^-1, while the ball phenotype displayed saturation at 200 mol photons m^-2s^-1. The inhibitors of total CA activity (6-ethoxizolamide) and extracellular CA activity (dextran-bound sulfonamide) inhibited photosynthesis at pH 8.2, to 90 and 50% respectively, in both phenotypes. No inhibition of the photosynthetic oxygen evolution was detected at pH 6.5. CA activity was associated with both supernatant and pellet fractions of crude extracts of S. filiformis. The rate of alkalization of the medium by the algae was dependent on light intensity. We suggest that carbon dioxide is the general form of inorganic carbon transported across the plasmamembrane in S. filiformis. HCO₃ transport into the cell takes place simultaneously by an indirect mechanism (dehydration to CO₂ catalyzed by CAext) and by direct uptake. Extracellular (CAext) and intracellular (CAint) CAs are involved in the mechanisms of inorganic carbon assimilation by S. filiformis.     

Genetic variation and biochemical systematics in the marine bryozoan Alcyonidium mytili

For many years the taxonomic position of the marine ctenostome bryozoan Alcyonidium mytili Dalyell (1848) has been in doubt, with some authorities regarding it as being conspecific with A. polyoum (Hassall). We have set out to resolve this problem using enzyme electrophoresis to examine the genetics of the population structure in the two species. The results show beyond reasonable doubt that sympatric populations of the two species are indeed from quite separate and non-interbreeding gene pools. An examination of various allopatric populations shows a new species of A. mytili to exist sympatrically with the other at Langstone Harbour, Hampshire, England. This species can be readily distinguished on morphological as well as genetic ground. Samples of A. mytili from Guernsey also show substantial genetic differences from other populations examined. It is tentatively concluded that this population also represents a separate gene pool and consequently should be recognised as a third species of A. mytili.     

Effects of acute changes in temperature and salinity on the oxygen uptake of larvae of herring (Clupea harengus) and plaice (Pleuronectes platessa)

Routine oxygen uptake (QO₂) by yolk-sac and firstfeeding larvae of herring (Clupea harengus L.) and plaice (Pleuronectes platessa L.) was studied after acute change of temperature (8°, 13°, 18°C) and salinity (5, 12.7, 32, 40). In both species, QO₂ (l mg^-1 dry wt h^-1) of both larval stages increased with increasing temperature. Salinity effect on QO₂ varied: for yolk-sac larvae of both species a lower QO₂ was found at lower combined salinities (5 and 12.7); for feeding larvae a lower QO₂ was observed at 12.7 for both species, possibly due to the relatively smaller size of larvae used at this salinity. For both species, oxygen uptake increased as larvae grew and weight regression coefficients were between 0.74 and 1.33. At 32 S, no difference was found in oxygen consumption between species as a function of temperature.Based on a dissertation submitted in partial fulfillment of the requirements for the degree of Master of Science at the University of Stirling, Stirling, Scotland. The work was performed at the Dunstaffnage Marine Research Laboratory, Oban, Scotland     

Importance of the fatty acids 20:5ω 3 and 22:6ω 3 in the diet of plaice (Pleuronectes platessa) larvae

The requirement of plaice (Pleuronectes platessa L.) larvae for the fatty acids 20:5 3 and 22:6 3 was studied. Larvae were reared from first feeding to beyond metamorphosis on Artemia sp. nauplii (EG brand), whose nutritional content had been manipulated by enrichment. Some larvae were fed Artemia rich in 20:5 3 and 22:6 3, and others were fed nauplii with no 22:6 3 and low levels of 20:5 3 (1.9% of the total fatty acids). The differences in diet had no significant difference on growth or survival of the plaice larvae. The results indicate that the plaice larvae in this study did not require 22:6 3 in their diet, even when the levels of 20:5 3 were low.     

Physiological ecology of picoplankton in the North Sea

The distribution of cyanobacteria in the surface waters of the North Sea was measured during July 1987. Numbers of cyanobacteria ranged from 2.5x10⁶ to 1.7x10⁸ cells 1^-1. In the majority of stations, cyanobacterial numbers were highest in the near-surface water and a subsurface maximum was found at only one station. The distribution of ¹⁴C among the end-products of photosynthesis was determined for picoplankton (<1 m) and other phytoplankton >1 m throughout the North Sea. The majority of label was found in the protein fraction of both picoplankton and >1 m phytoplankton; incorporation into lipids and polysaccharides plus nucleic acids was much lower. We interpret the large incorporation into protein to be a consequence of nutrient limitation of these natural assemblages. Photosynthetic parameters of the two size fractions were also determined. Assimilation number (P _m ^B ) and initial slope were greater for the picoplankton fraction than for phytoplankton >1 m but there was no evidence of significant photoinhibition of either fraction at irradiances up to 1 000 E m^-2 s^-1.     

Aqua regia extractable trace elements in surface soils of venezuela

Surface soils (0–15 cm) were sampled at 10–20 km intervals along two transects in Venezuela. One (1162 km, 70 samples) ran west to east parallel with the Caribbean coastline, the other (920 km, 92 samples) ran south to north from the frontier with Brazil to the Caribbean shore. Sampling took place in both a wet and a dry season. Trace metals were extracted from dried, sieved (<2 mm) soil with boiling aqua regia followed by analysis by ICP or flame AAS. Metal values did not differ significantly between the two seasons and dates were averaged. Geometric mean values for the west–east transect were: Cr=41.5, Cu 17.9, Cs 3.6, Li=13.9, Mn=294, Ni=21.3, Pb=17.4, Sr=39.4, V=60.4 and Zn = 83.7g g^–1, respectively. Similarly, for the south–north transect Cr=21.3, Cu=4.3, Cs=1.1, Li=2.0, Mn=55.7, Ni=4.4, Pb=6.1, Sr=13.3, V=28.2 and Zn=16.7g g^–1, respectively. A classification of samples by lithology showed surface soil composition to be related to rock composition. Metal values were low in the soils in the south of the country, in the Guyana highlands (Gran Sabana). Low Zn contents were prevalent. Lead contents were affected by roadside fallout from vehicles using leaded petrol except that high Pb contents of soils in the Gran Sabana were of more complex origin.     

The structure of plankton communities of the Indian Ocean

Species diversity and trophic structure of plankton communities have been considered as most important biological features. The Fisher () and Simpson () indices and the information index H=- pi log₂ pi (Margalef) were used for evaluation of species diversity. The indices have been calculated within the group of filter feeders by numbers ( and H) and biomass ( and H) of the species; the best results were obtained in the latter case. The index H=- pi log₂ pi is proposed for the quantitative evaluation of trophic structure, where a portion of an individual trophic group is taken as pi. The plankton material was collected by the R.V. Vityaz in the northern Indian Ocean in January through February, 1960. Analysis of characteristics of zooplankton distribution, species and trophic diversity in connection with characteristics of the water regime resulted in the definition of 3 types of the plankton communities: (a) those in intensive divergence zones; (b) those in poor divergence zones; (c) those in regions with stable water stratification or with feebly marked convergence, distiguished by different values of biomass, species diversity, and trophic group ratios.     

Effects of nitrogen and phosphorus enrichement on in vivo symbiotic zooxanthellae of Pocillopora damicornis

The reef coral Pocillopora damicornis (Linnaeus) was grown for 8 wk in four nutrient treatments: control, consisting of ambient, unfiltered Kaneohe Bay seawater [dissolved inorganic nitrogen (DIN, 1.0 M) and dissolved inorganic phosphate (DIP, 0.3 M)]; nitrogen enrichment (15 M DIN as ammonium); phosphorus enrichment (1.2 M DIP as inorganic phosphate); and 15 M DIN+1.2 M DIP. Analyses of zooxanthellae for C, N, P and chlorophyll a after the 8 wk experiment indicated that DIN enrichment increased the cellular chlorophyll a and excess nitrogen fraction of the algae, but did not affect C cell^-1. DIP enrichment decreased both C and P cell^-1, but the decrease was proportionally less for C cell^-1. the response of cellular P to both DIN and DIP enrichment appeared to be in the same direction and could not be explained as a primary effect of external nutrient enrichment. The observed response of cellular P might be a consequence of in situ CO₂ limitation. DIN enrichment could increase the CO₂ (aq) demand by increasing the net production per unit area. DIP enrichment could slow down calcification, thus decreasing the availability of CO₂ (aq) in the coral tissue.Hawaii Institute of Marine Biology Contribution No. 920     

Dance dialects and foraging range in three Asian honey bee species

Summary We measured the distance dialects in the dance languages of three honey bee species in Thailand (Apis florea, A. cerana, and A. dorsata), and used these dialects to examine the hypothesis that a colony's dialect is adaptively tuned to enhance efficiency of communication over the distances that its foragers typically fly. in contrast to previous interspecific comparisons in Sri Lanka (Lindauer 1956; Punchihewa et al. 1985), we found no striking dialect differences among the Asian bees in Thailand. The adaptive tuning hypothesis predicts that the foraging ranges of the three species should also be similar, but comparisons of colonial foraging range using the forage mapping technique (Visscher and Seeley 1982) actually revealed marked differences. This raises the possibility that the link between ecology and distance code is more subtle than previously supposed, if a link exists at all. Offprint requests to: F.C. Dyer     

Metabolism and swimming efficiency of the bonnethead sharkSphyrna tiburo

Routine metabolic rates of bonnethead sharks,Sphyrna tiburo, of 95 to 4 650 g, ranged from 70.4 to 15.0 kcal kg^–1 d^–1. Over the size range 34 to 95 cm total length, shark swimming-velocities varied from about 29 to 67 cm s^–1. Swimming velocities predicted using Weih's cost-optimization model were similar to observed velocities. The total cost of transport (the energetic cost of transporting 1 unit of body mass 1 km distance) for 1 to 8 kg sharks varied from 0.67 to 0.40 cal g^–1 km^–1. The energetic range (an estimation of the distance traveled after a 25% reduction in body weight) indicates that a 1 kg bonnethead shark would travel 500 km distance in 17 d before displaying a 25% reduction in weight. An 8 kg individual would travel 830 km in 23 d. Although the bonnethead shark is a continuously active species, its routine metabolic rate and the efficiency of its locomotory system may be similar to that of typical bony fishes.     

Allozyme and colour differences between two sibling species of the heteronemertean Lineus torquatus from the Sea of Japan

Brown and cherry colour morphs of the heteronemertean Lineus torquatus Coe, 1901 from the Vostok Bay of the Sea of Japan were compared using allele frequencies at 18 isozyme loci. These morphs shared no common alleles at 9 of the 18 loci. The observed genetic differences are strong evidence that the brown and cherry colour morphs, which occur sympatrically, are different species. Nei's genetic distance between these species (D=1.135) is considerably higher than typical D values for congeneric animal species. As with much previous work on nemerteans, intraspecific allozymic variability in both species was high, with mean expected heterozygosity values 0.286±0.049 and 0.159±0.051 for L. torquatus (brown) and L. torquatus (cherry) species, respectively.     

Residues of Organochlorinated Pesticides in Eggs of Water Birds from Tai Lake in China

The levels of organochlorine compounds in eggs of water birds from the colony on Tai Lake in China were studied. The eggs were collected in 2000 and belonged to the following species: 65 samples of black-crowned night heron (Nycticorax nycticorax), 36 samples of little egret (Egretta garzetta), 26 samples of cattle egret (Bubulcus ibis) from 13 clutches and 43 samples of Chinese pond heron (Ardeola bacchus) from 17 clutches. Dichlorodiphenyltrichloroethane (DDT) and its derivates (DDE and DDD), hexachlorocyclohexane (HCH) and its isomers (-HCH, -HCH, -HCH, -HCH), heptachlor, heptachlor epoxide, aldrin, dieldrin, endrin, endrin aldehyde, -endosulfan, -endosulfan, and endosulfan sulfate were determined in the laboratory by gas chromatography. The data showed that DDE had the highest levels in all the samples, followed by -HCH. The mean levels of DDE among the water bird species were in the order as follows: black-crowned night heron (5464.26ng/g, dry weight) > Chinese pond heron (2791.12ng/g, dry weight) > little egret (1979.97ng/g, dry weight) > cattle egret (660.11ng/g, dry weight). DDT and its metabolites accounted for 90% of the total organochlorines, except that it was only 73% for cattle egret. The differences of the residue among the bird species were statistically significant and could be attributed to their variations in prey and habitat. Although the DDE burdens in Tai Lake were much lower than 8 g/g (wet weight) which are thought to have significant adverse effects on black-crowned night herons, they would be expected to increase the risk of adverse effects on survival of chicks of herons and egrets, particularly black-crowned night heron, based on the critical value of 1 g/g (wet weight) DDE. The burdens of HCHs in this study were higher and the cyclodienes were lower than those found elsewhere.     

Male bird song attracts females — a field experiment

Summary The initial stage of pair formation of the pied and the collared flycatcher (Ficedula hypoleuca and F. albicollis) was simulated in a field experiment. Male dummies positioned near nest boxes and singing by means of tape-recorded song from loudspeakers offered prospecting females a nest box combined with an automatic trap. An unequivocal demonstration of female arrival at the male's territory was obtained by the trapping of the female. Control nest-box traps were provided with silent dummies. Factors other than male song causing female attraction were controlled by a daily switch of the position of singing and silent dummies. Nine out of ten females were caught in nest-box traps with singing dummies (one-tailed binomial test, P=0.011). The result supports the hypothesis that male song functions in mate attraction. This hypothesis has never previously been tested in field experiments although circumstantial evidence for it has been available.     

Seasonal photosynthetic characteristics of Ascoseira mirabilis (Ascoseirales,Phaeophyceae) from King George Island,Antarctica

Monthly variation in photosynthesis, dark respiration, chlorophyll a content and carbon: nitrogen (C:N) ratios in different lamina sections of adult plants of Ascoseira mirabilis Skottsberg from King George Island, Antarctica, was investigated between September 1993 and February 1994. Light saturated net photosynthesis (P _max) showed maximum values in September (12 to 25 mol O₂ g^-1 fr wt h^-1), and decreased towards the summer to values ranging between 2.0 and 5.0 mol O₂ g^-1. In the distal section, however, a second optimum occurred in December (25 mol O₂ g^-1 fr wt h^-1). Dark respiration rates were also highest in October and November and decreased strongly in December to February (6.0 and 1.0 mol O₂ g^-1 fr wt h^-1, respectively). Gross photosynthesis exhibited high values between September and December. Concomitant with the seasonal decrease of photosynthetic efficiency () from mean values of 1.2 mol O₂ g^-1 fr wt h^-1 (mol photons cm^-2 s^-1)^-1 in September to 0.3 mol O₂ g^-1 fr wt h^-1 (mol photons cm^-2 s^-1)^-1 in January, the initial light saturating point (I _k) gradually increased from 19 to 60 mol photons m^-2 s^-1. Likewise C:N ratios were low in spring (12 to 13) and increased in summer (20). In general, the photosynthetic parameters P _max, gross photosynthesis, and Chl a concentrations were significantly higher in the distal section of the thallus. In contrast, C:N ratios were lower in the distal section of the lamina. The results show that photosynthesis obviously strongly supports growth of the alga in late winter to spring, as it does in some morphologically related brown algae from temperate and polar regions. The question whether growth is additionally powered     

Influence of salinity and temperature on the oxygen consumption in young juveniles of the Indian prawn Penaeus indicus

Routine oxygen consumption of very young juveniles (0.1 g) of Penaeus indicus H. Milne Edwards was significantly influenced by ambient temperature and weight of the animal, but not by ambient salinity, when tested at salinities (7, 21, and 35) to which they had been long-term (over 10 days) acclimated. Standard oxygen consumption of young juvenile prawns (1 to 3 g), subjected to step-wise changes in ambient salinity, from sea water to low salinity waters (2 to 6), and measured after short-term (24 h) salinity acclimation at each step, was lowest at salinities where prawns such as those tested occur naturally (10 to 15). The metabolic rates do not appear to have a direct relation to the osmotic gradient, even when the influence of interfering activity is eliminated. It appears that factors other than osmotic gradient will have to be sought in order to explain the metabolic patterns of P. indicus in relation to salinity.