Effect of hatching time on larval mortality and survival of the prawn Macrobrachium idae

The prawn Macrobrachium idae Heller carries 40 to 160 eggs depending upon the body size of the mother animal. After incubation, 63, 35 and 2% eggs are hatched on the first, second and third hatching nights, respectively. Mean dry weight of a single larva relased on the first night is 420 g (equivalent to 2.86 cal). Larvae released on the second or third hatching nights weighed 380 g (=2.56 cal) or 308 g (=2.02 cal). The total reserve yolk-energy available in a larva hatched on the first night is 1 cal. There is a definite shift from protein to fat metabolism as hatching is delayed. Oxygen consumption of developing eggs awaiting release on the first or second hatching night is 1.9 l/mg dry weight/h. In comparison to larvae released on the first night, those released on the second night exhibit 2% increase in total body-length and 2.4 or 14.3% decrease in the lengths of the 6th abdominal segment or the orbit. Larvae released on the first, second or third hatching nights, on exposure to starvation stress, survive for 3.8, 2.3 or 1.5 days. The swimming speed of larvae released on the first or second night is 1.0 or 0.6 cm/sec. Larvae released on the subsequent hatching nights committed nearly 2 times greater number of mistakes per cm distance in the horizontal plane. Since hatching of all developing eggs simultaneously on the first hatching night is possible by means of artificial technique(s), it is possible to improve survival rate of decapod larvae.     

Ecophysiological studies on the developing eggs and embryos of the European lobster Homarus gammarus

During the course of its embryonic development, the European lobster Homarus gammarus Linnaeus exhibits progressive increases in content of water (54.0 to 83.1%), ash (2.7 to 16.7%), protein (47.4 to 50.9%) and non-protein nitrogen (1.0 to 2.4%), and steady decreases in content of fat (43.8 to 25.4%) and energy (6343 to 5431 cal/g dry organic substance). Cumulative yolk utilization efficiency during the total development is 81.8% for dry weight; the corresponding value for energy is 60.1, for protein 75.6 and for fat 47.4%. Energy content of a single egg is 10.49 cal. Of 4.20 cal expended for metabolic processes of the embryo, only 13.3% energy is drawn from protein oxidation; fat oxidation supplies as much as 87.7% energy, that of carbohydrate only 2.3%. Embryonic development results in a remarkable decrease in net yolk utilization efficiency, which falls from 85.5% in the early developmental stages, to less than 70% in later developmental stages. The mean dry weight of a single egg membrane increases from 38 g (2.2% of egg weight) in a freshly laid and attached egg, to 81 g in an egg with an almost completely developed embryo. This result supports the earlier observation of Cheung (1966) that the formation of the inner chitinous egg membrane occurs after the egg is laid and attached to the setum. Protein seems to be the major constituent of the egg membrane (4049 cal/g dry weight), which has the following composition: protein 70.4%, non-protein nitrogen 0.13%, ash 2.83%. Initial permeability of the egg membrane to water (about 6% of the total water requirement is let in) is followed by a period during which the egg membrane is almost impermeable to water (stages I to III); the egg membrane becomes permeable to water again and lets in 85% of the total water requirement (the rest, i.e. 9%, is metabolic water) at a relatively advanced stage of development. These assumed changes in egg membrane permeability appear to be indicative of variations in the egg's osmoconcentration leading to shiftings in net transport of water. Rates of water and salt uptake during embryonic development are essentially parallel (Fig. 1). The egg membrane remains permeable to salts throughout development; salt intake almost doubles after the egg passes through stage III. A single egg, weighing 3.7 mg requires 4.9 mg water for successful completion of embryonic development. The imbibition of water by the developing marine demersal egg seems to (1) serve in osmotic hatching; (2) float the hatched larva by means of specific gravity reduction; (3) aid the larva to quickly adjust its body temperature. The simple osmotic hatching mechanism, proposed by previous workers, seems to be inadequate to account for the events and timing of the hatching process in the lobster. It is suggested that hatching time is determined not solely by increased internal pressure caused by inflow of water and salts, but also by some unknown internal factor. In the lobster egg, as well as in many other marine demersal eggs, protein metabolism is suppressed to a considerable extent, and fat metabolism is geared up Thus, the non-cleidoic lobster eggs exhibit metablic properties which are typical of cleidoic eggs. This finding is discussed in the light of Needham's (1950) concept of cleidoicterrestrial and non cleidoic-aquatic eggs.Dedicated to Professor P. Kochukutta Menon, Montreal, on his 62nd birthday, June 3, 1970.     

Yolk utilization and hatching time in the Canadian lobster Homarus americanus

During the course of its embryonic development, the Canadian lobster Homarus americanus Milne-Edwards exhibits steady increases in water content (56.2 to 86.8%) and ash (5.8 to 21.2%), and a progressive decrease in energy content from 6636 to 4292 cal/g dry weight. Mean dry weight of a single egg is 965 g, equivalent to 6.4 cal; a freshly hatched egg. The lobster hatches about 1,500 larvae per night over a period of 4 to 5 days. Dry weight, ash and calorific contents of larvae hatched on different days show considerable variations. After larvae hatch on the first day, continuous salt absorption by eggs to hatch on subsequent days leads to a steady increase in ash content from 143 g/larva hatched on the first day to 255 g/larva hatched on the fourth day, and consequently, to an increase in dry weight from 854 to 956 g/larva. Metabolism of embryos (0.1 cal/day), which are yet to be hatched on subsequent days, depletes the calorific content per unit weight (from 4637 to 3837 cal/g dry weight) as well as per larva (from 3.98 to 3.67 cal).Dedicated to my colleague K.-H. Schumann (Biologische Anstalt Helgoland) who died on December 12, 1969 due to a diving accident.     

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     

Relationships between seston,available food and feeding activity in the common mussel Mytilus edulis

The feeding and metabolic rates of Mytilus edulis L. of different body sizes were measured in response to changes in particle concentrations ranging from 2 to 350 mg l^-1. Rates of oxygen consumption were not significantly affected by changes in seston concentration, whereas clearance rates gradually declined with increasing particle concentration. Pseudofaeces production was initiated at relatively low seston concentrations (<5 mg l^-1). Marked seasonal changes were recorded in the composition of suspended particulates (seston) in an estuary in south-west England. Total seston was sampled at frequent intervals throughout an annual cycle and analysed in terms of: particle size-frequency distributions, total dry weight (mg l^-1), inorganic content, chlorophyll a, carbohydrate, protein and lipid. The particulate carbohydrate, protein and lipid content provided an estimate of the food content of the seston. The results are discussed in terms of the food available to a nonselective suspension feeder, such as M. edulis, during a seasonal cycle. The effect of inorganic silt in suspension was mainly to limit by dilution the amount of food material ingested rather than to reduce the amount of material filtered by the mussel. In winter, the food content of the material ingested was 5%, and this increased to 25% during the spring and summer.     

Stable isotope and biochemical fractionation in the marine pelagic food chain: the jellyfish Pelagia noctiluca and net zooplankton

In our field study we analyzed the C and H isotopic and biochemical (C, N, P, protein, lipid, carbohydrate) composition of the jellyfish Pelagia noctiluca (collected from the Gulf of Trieste in 1985 to 1986) and its presumed diet-net zooplankton. The mean ¹³C (-18.8) and D (-58.4) ratios of P. noctiluca showed enrichment in heavy isotopes relative to net zooplankton (2 for carbon and 30 for hydrogen). Both the jellyfish and net zooplankton were characterized by a linear correlation between ¹³C and D. C. N, P, protein, lipid, and carbohydrate contents of P. noctiluca were low on a dry weight basis as compared to net zooplankton. Significantly lower C:N and C:P ratios were found in jellyfish indicating a greater loss of carbon relative to nitrogen and phosphorus along the passage to a higher trophic level. Isotopic and biochemical evidence indicate that, though collected in nearshore waters, P. noctiluca depended on autochthonous marine organic matter.     

Sexual reproduction of the solitary sunset cup coral<Emphasis Type="Italic"> Leptopsammia pruvoti</Emphasis> (Scleractinia: Dendrophylliidae) in the Mediterranean. 1. Morphological aspects of gametogenesis and ontogenesis

Information on the reproduction in scleractinian solitary corals and in those living in temperate zones is notably scant. Leptopsammia pruvoti is a solitary coral living in the Mediterranean Sea and along Atlantic coasts from Portugal to southern England. This coral lives in shaded habitats, from the surface to 70 m in depth, reaching population densities of >17,000 individuals m^–2. In this paper, we discuss the morphological aspects of sexual reproduction in this species. In a separate paper, we report the quantitative data on the annual reproductive cycle and make an interspecific comparison of reproductive traits among Dendrophylliidae aimed at defining different reproductive strategies. The present study on L. pruvoti is the first in-depth investigation of the reproductive biology of a species of this genus. As expected for a member of the family Dendrophylliidae, L. pruvoti is a gonochoric and brooding coral. The gastrodermal tissue of the gametogenetic mesenteries we examined was swollen and granular, which led us to hypothesize that interstitial cells could have a trophic function favoring gametogenesis. Undifferentiated germ cells arose in the gastrodermis and subsequently migrated to the mesoglea, where they completed gametogenesis. During spermary development, spermary diameter increased from a minimum of 14 m during the immature stages to a maximum of 410 m during the mature stages. As oogenesis progressed, we observed a gradual reduction in the nucleus to cytoplasm ratio due to the steady synthesis of yolk. During the final stages of oogenesis, after having migrated to the extreme periphery of the oocyte and having firmly adhered to the oolemma, the nucleus became indented, assuming a sickle or dome shape. We can hypothesize that the nucleus migration and change of shape may have to do with facilitating fertilization and determining the future embryonic axis. During oogenesis, oocyte diameter increased from a minimum of 20 m during the immature stage to a maximum of 680 m when mature. Embryogenesis took place in the coelenteron. We did not see any evidence that even hinted at the formation of a blastocoel; embryonic development proceeded via stereoblastulae with superficial cleavage. Gastrulation took place by delamination. Early and late embryos had diameters of 204–724 m and 290–736 m, respectively. When released, the larvae had completed ontogenesis and swam by a ciliary movement with the aboral pole at the anterior, their shape varied from spherical to cylindrical (in the latter the oral–aboral axis measured 695–1,595 m and the transversal one measured 267–633 m).Communicated by R. Cattaneo-Vietti, Genova     

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.     

Potential effects of a resuspension event on the vertical distribution of copepod eggs in the sea bed: a laboratory simulation

Adult female Acartia tonsa and Labidocera aestiva were obtained from inshore marine waters near Turkey Point, Florida (29°54.5N;84°31W) during April and May 1991. For each species, eggs spawned overnight in the laboratory were collected, mixed with sediment, and added to a plastic tube (26 to 29 cm longx5 cm diam) to yield a 2 cm-thick layer. This tube was connected to a 245 cm-long tube, seawater was added and the contents were thoroughly mixed by turning the assembly end-over-end several times. The vertical distribution of eggs in the sediments following resuspension varied according to the grain size of the sediments. For sediments of 125 m particle-diameter, 68 to 72%, and 70 to 73% of the eggs of A. tonsa and L. aestiva, respectively, occurred in the upper 4 mm.For sediments 63 to <125 m particle-diameter, 34 to 36% of the eggs of A. tonsa and L. aestiva, respectively, occurred in the upper 4 mm. For sediments of <63 m particle-diameter, egg distribution was uniform for both species throughout the 2 cm layer. The results indicate that the vertical distribution of eggs in the sea bed following a resuspension event should be highly dependent upon the grain-size composition of the sediments.     

Seston composition of the bottom waters of Great Lameshur Bay,St. John,US Virgin Islands

Seston composition [particulate organic carbon (POC), particulate nitrogen (PN), phyto- and microzooplankton numbers and biomass] was investigated in the bottom waters of Great Lameshur Bay, St. John, Virgin Islands (USA), in October, 1970 during Tektite II Mission 17–50. Mean values of 67.4 g POC · I^-1 and 7.2 g PN · I^-1 were determined. A mean phytoplankton carbon content of 42.2 g · I^-1 and zooplankton carbon content of 5.5 g · I^-1 were calculated from counts. The phytoplankton consisted mainly of dinoflagellates 71.2% phytoplankton carbon. Copepods were the dominant zooplankters (61.8% zooplankton carbon), followed by larvaceans (30.9% zooplankton carbon). Organic carbon content of counted zooplankton faecal pellets ranged between 0.4 and 1.6 g · I^-1, and amounted probably to about 15% of the total zooplankton carbon value. Plankton and detritus components as possible food for coral-reef animals are discussed. The ratio carbon: nitrogen of suspended particles is compared to that of sedimented matter.     

Proximate composition and nucleic acid content of premetamorphic leptocephalus larvae of the congrid eel Ariosoma balearicum

Water, ash, proximate composition (protein, lipid, carbohydrate, hexosamine), and nucleic acid (DNA, RNA) content were measured in premetamorphic larvae of the congrid eel Ariosoma balearicum (Delaroche) collected from the eastern Gulf of Mexico. Specimens ranged from 15.0 to 202.3 mm total length (TL) and 0.0116 to 4.3860 g wet mass (WM). Water content increased linearly with increasing specimen mass over the entire size range; consequently, percent water was uniform and had a mean value of 92.9±1.09% WM. Ash content also increased linearly with specimen mass, but only up to a mass of 2.5 g WM (165 mm TL). Ash content in specimens >165 mm TL showed only a small increase with mass, suggesting an improved osmoregulatory capability in larger individuals. The absolute amount of all proximate components increased with increasing specimen size, but rates of deposition among the components varied, resulting in different patterns in the relative concentrations of each with growth. Protein dominated the ash-free dry mass (AFDM) throughout development (29 to 59% AFDM); carbohydrate and hexosamine occurred in similar proportions (8 to 24% AFDM). Lipid was a significant proportion of the AFDM in only the smallest individuals. Lipid concentrations decreased initially as mass increased in individuals smaller than 0.4 g WM (90 mm TL), indicating a low rate of lipid deposition in small individuals. In specimens >90 mm TL, lipid concentrations were uniform and had a mean of 12% AFDM. Trends for biochemical components and nucleic acids suggest that growth of Phase I leptocephali occurs in two subphases (Ia and Ib). Phase Ia is characterized by cellular proliferation, preferential synthesis of protein and carbohydrate relative to lipid, and growth manifested more as increased length rather than increased mass. For A. balearicum, Phase Ia extends from yolk-sac absorption to 90 mm TL. In Phase Ib, nucleic acid content levels off, lipid deposition increases, and mass increases exponentially.     

Possible strategy for the survival of marine bacteria under starvation conditions

A population of a psychrophilic marine vibrio (Ant-300) suspended at a low cell density in natural seawater (SW) or artificial seawater (ASW) showed an initial 200-fold increase in cell numbers. Ant-300 suspended in ASW at various densities showed a magnified initial increase in numbers as well as increased longevity as the population density decreased. The magnitude of the initial increase and the viability of the cells after 7 weeks continued incubation were the same whether the cells were suspended in SW, ASW amended with amino acids, or organic-free ASW. Continued incubation (long-term starvation) of a culture of Ant-300 at low cell densities in ASW showed that after 70 weeks over 15 times the orginal number of cells were still viable. When compared to the starvation survival of other bacceria, Ant-300 exceeds the longest reported starvation survival by at least 2.5 times. Our data indicate that Ant-300 is especially adapted for survival at low nutrient concentrations and low population densities due to a sustained increase in cell numbers that may represent a species survival mechanism for marine bacteria.Technical Paper No. 4493, Oregon Agricultural Experiment Station.     

Physiological and biochemical aspects of embryonic and larval development of the winter flounder Pseudopleuronectes americanus

Eggs and larvae of the winter flounder Pseudopleuronectes americanus Walbaum were hatched and raised in the laboratory under controlled conditions. Biochemical composition was measured during development and found to be similar to that of other species: 65 to 80 percent protein, 15 to 30 percent fat, and 0 to 5 percent carbohydrate. Ash content was 7 to 10 percent of dry weight. The chorion comprised more than half of the weight of an egg and the data suggested that it was possibly a source of nutrition to the developing embryo. The sequence of utilization appeared to be carbohydrate and then protein to hatching, lipid, mixed lipid and protein, the predominantly protein until feeding began. Carbohydrate was accumulated at first feeding and depleted when growth began. Protein and lipid were deposited in approximately constant proportions. Respiration rates of eggs were low, 0.002–0.015 l O₂ egg^-1 h^-1, but rose gradually from fertilization to hatching. Respiration rates of early larvae were from two to eight times that of eggs (0.033–0.131 l O₂ larva^-1 h^-1). Variation in larval respiration rates indicated a three-fold difference in rate according to level of activity. Eggs excreted ammonia at an increasing rate from fertilization to hatching. Larvae excreted ammonia, primary amines, and other unidentified organic nitrogenous substances. Rates of excretion and proportions of excretory products varied with stage of development. Primary amine excretion was variable and a major component in early stages. Ammonia-N excreted was two to 20 times primary amine N excreted. Unidentified substances were the predominant form of N excretion during early feeding. Ammonia accounted for most of the N excreted in older larvae. Early specific growth rates were 2.1 and 5.5%. Net caloric conversion and net and gross nitrogen efficiencies were low in first feeding larvae compared to adult fishes (32.2, 27.7, and 10.7% respectively).Contribution no. 5071 from the Woods Hole Oceanographic Institution     

Brood size and chemical composition of Pareuchaeta norvegica (Crustacea: Copepoda) in Loch Etive,Scotland

Brood size and chemical composition (carbon, nitrogen, and ash) of Pareuchaeta norvegica in Loch Etive, Scotland have been determined. From 23 to 37 eggs were found in each egg mass (mean=30 eggs). The eggs are oval; the mean size of the longer axis is 438 m. Variation in egg mass (as dry weight) is related to increase in dry weight of the maternal body. an increase of 1 mg in maternal body dry weight produces an increase of 0.03 mg dry weight in the egg mass. Carbon content increases with increasing body dry weight both in pre-spawning and spent females, but nitrogen content decreases with increasing body weight. Thus, the carbon:nitrogen ratio increases with increasing body dry weight. The carbon content of an egg mass ranges from 61.4 to 65.3%, and nitrogen content from 9.6 to 13.2% of the total dry weight. Some examples of partitioning of chemical components of the maternal body into the egg mass are also described.     

Arsenic tissue concentration of immature mice one hour after oral exposure to gold mine tailings

A potentially high bioavailability of arsenic in gold mine tailings from a site in northern California has been suggested by solubility studies. To help address this issue, an in vivo dosing study was conducted using 12dayold Swiss Webster mouse pups (n=8/group). A sample of sizefractionated mine tailings from the site (<20m particle size, 691g g^–1 arsenic) was prepared as an aqueous suspension and administered by gavage in a volume that provided 4mg As/kg body weight. The control group received the same volume of a commercial soil (1g g^–1 As) of similar particle size (<60m). No mortality or toxic signs were noted in either group. Tissue samples were collected 1h after gavage, freezedried, microwavedigested and analysed for arsenic by ICP/MS (detection limit 2ng As g^–1 dry weight). Arsenic concentrations (ng As g^–1 dry weight) in tissues from the pups who received mine tailings were significantly higher than in control tissues. The mean elevation in arsenic concentration was highest in the liver (3364% of control, p<0.0001), followed by blood (818 of control, p<0.0001), skin (207% of control, p=0.07), and brain (143% of control, p<0.0001). The carcass arsenic concentration (excluding the GI tract, liver, brain and skin) was 138 of control (p=0.02). The data indicate uptake of arsenic from weathered mine tailings by the immature mouse pups after oral exposure.     

Responses of Leptasterias hexactis (Echinodermata: Asteroidea) to low salinity

The six-rayed starfish Leptasterias hexactis (Stimpson, 1862) is seasonally exposed to low salinities in southeastern Alaska. Individuals that were gradually exposed to reduced salinities in the laboratory had a 28-d TLm of 12.9 S. The activity of L. hexactis, as measured by its activity coefficient, varied directly with salinity. Individual feeding rates of the starfish on similarly exposed Mytilus edulis, measured daily for 21 d at salinities of 30, 20 and 15 S, also varied directly with salinity. The dry weight of mussel tissue consumed was 8.84, 8.49 and 0.58 mg ·starfish^-1·d^-1 at 20, 20 and 15 S. Expressed as percent of dry starfish weight, the daily feeding rate was 1.35, 0.76 and 0.10% at 30, 20 and 15 S. Absorption efficiency decreased from 64% at 30 S to 49% at 20 S, further reducing the energy available for metabolism. Growth, measured in terms of changes in total dry weight or dry weight of soft tissues, also varied directly with salinity. Although exposure to hyposmotic conditions did induce stress responses, as indicated by reductions in activity, feeding, absorption efficiency and growth rates, L. hexactis maintained positive growth for at least a 3-wk period in the laboratory at 20 S and 13°CC. The population of L. hexactis investigated must be considered euryhaline and brief periods of exposure to hyposmotic conditions should not limit its distribution.     

Water and salt balance of halibut eggs and larvae (Hippoglossus hippoglossus)

Eggs of halibut [Hippoglossus hippoglossus (L.)] have a negative buoyancy in sea water of 35 S, in contrast to eggs of most flatfish species. The cause of this was investigated. The osmolality of the yolk is 350–420 mOsm during embryonic development. This is within the range for marine teleost serum and for yolk of pelagic eggs. Concentrations of major inorganic ions are comparable with those of pelagic plaice eggs [Pleuronectes platessa (L.)]. The values for Na⁺, K⁺ and Cl^- are 6, 85, and 64 mmol · (1 H₂O)^-1 after fertilization, and at the time of hatching the corresponding values are 17, 11, and 80. Large amounts of other inorganic constitutents are excluded for osmotic reasons. Malfunction in the regulation of osmolality or of inorganic constituents is thus unlikely to be the cause of negative buoyancy. The relative dry weight of the chorion (egg shell) in halibut eggs is less than in several pelagic egg types, excluding the chorion as the main contributor of negative buoyancy. It is concluded that a high content of organic matter in the rest of the egg is the cause of the negative buoyancy.     

“Copper” granules in the barnacle Balanus balanoides

Balanus balanoides (L.) collected from an area with high heavy-metal run-off contained two different types of granule within the parenchyma cells of the prosoma. X-ray microprobe analysis shows one to be the familiar zinc granule made up of concentric layers and giving major peaks for phosphorus and zinc, and the other to be homogeneous and giving peaks for sulphur and copper. This latter granule is designated the copper granule. Whilst zinc granules are known to be composed of inorganic phosphate, various tests on copper granules in sections and in a granule-rich pellet have shown that the copper is probably complexed with organic matter. The tests also demonstrated the relatively, insoluble (inert) nature of these granules. Although zinc and copper granules were present together in the prosoma, atomic absorption analyses of whole bodies (prosoma+thorax) have shown the level of zinc (50.28 g/mg dry weight) to be much higher than that of copper (3.75 g/mg dry weight).     

Isolation and characterization of granules from the kidney of the bivalveMercenaria mercenaria

Intracellular and extracellular granules are found in most bivalve kidneys. We examined the composition of kidney granules from the infaunal bivalveMercenaria mercenaria (L.) collected in 1985 from Cataumet Bay, Bourne, and Waquoit Bay, Falmouth, Massachusetts, USA. Small granules are numerically dominant, but large granules dominate the samples on the basis of weight. Large granules (estimated diam. >15 m) are composed primarily of metals (28% by weight) with Mn (8%), Ca (8%), Zn (4%) and Fe (4%) as the major contributors. Non-metal elements (P, C, H, N, S) together constituted 21% of the granule dry weight, though organic content (0.02% protein, 0.3% carbohydrate and 0.5% lipid) was low. Small kidney granules (10 m diam.) and digestive gland granules fromM. mercenaria had significantly higher C, H, and N contents than larger kidney granules. Our results, taken together with those from other bivalve species, suggest that kidney granule formation and subsequent increase in size is a continuous process of lysosomal maturation, residual body release and extracellular accumulation of predominately inorganic elements.     

Mass culture of the rotifer Brachionus plicatilis and its evaluation as a food for larval anchovies

Growth rates of anchovy larvae, Engraulis mordax, reared for 19 days under constant environmental conditions on a diet of laboratory-cultured organisms, exceeded the growth rates of anchovies fed on a diet of wild plankton. The rotifer Brachionus plicatilis was found to be a nutritous food source when fed to the larvae in concentrations of 10 to 20/ml and in combination with the dinoflagellate Gymnodinium splendens (100/ml). Optimum conditions were determined for mass culture of the rotifer. A high food concentration was the most important parameter needed to assure a high yield of rotifers. Large volumes (464 I) of the unicellular flagellate Dunaliella sp. were cultured for feeding the rotifers. The rotifer culture technique described produces approximately 2.5×10⁶ organisms/day, providing a reliable food source for rearing studies. The lengths of B. plicatilis (without eggs) ranged between 99 and 281 , most rotifers being larger than 164 and less than 231 . Individuals weighed 0.16 g and contained 8×10^-4 cal.