Ammonia excretion by the benthic estuarine shrimp Crangon franciscorum (Crustacea: Crangonidae) in relation to diet

Ammonia excretion of individual Crangon franciscorum Stimpson was monitored in response to ingestion of single meals. The three experimental diets were tubificids, mysids and fish. Ammonia excretion was also monitored for individual shrimp which had been starved. The rate of ammonia excretion was higher for fed than for starved individuals in all cases. Ammonia excretion rates were higher for shrimp which were fed tubificids than those fed the other diets. The rate of excretion was influenced by both weight of the individual and the amount ingested of each diet. Ammonia excretion was influenced by dietary factors other than nitrogen content of the diet or the quantity ingested. The data suggest that field estimates of ammonia excretion based on the excretion rates of starved animals may be underestimates. The recent feeding history of an organism influences the rate of ammonia excretion as well as the relationship between the rate of excretion and weight.     

Effects of various diets on the nutritional value of Artemia sp. as food for the prawn Penaeus monodon

The nutritional value of Artemia sp. as food for marine fish and crustacean larvae has been linked to the level of its polyunsaturated fatty acid (PUFA) content. Experiments in August 1984 were conducted to determine the effects of various artificial diets and algae on fatty acid composition of PUFA-deficient Artemia sp. (Utah GSL strain) and their resulting value as food for postlarvae of the prawn Penaeus monodon (Fabricius). Nauplii of the brine shrimp were grown on extracts of corn, copra, soybean and rice bran containing precursors (C18) to long-chain PUFA and also on algal species containing different levels of long-chain PUFA (C20). The nauplii were then used as food for P. monodon postlarvae. The results revealed that absence of C20 polyunsaturates from the feeds and their presence in the algae were reflected in the polyunsaturated fatty acid content of the tissues of Artemia sp. When fed with brine shrimp fed on algae, P. monodon displayed better postlarval survival and significantly higher growth; related to the content of polyunsaturated fatty acids in Artemia sp. A practical feeding approach in prawn hatcheries would be to grow Artemia sp. on a cheap diet such as rice bran, and then to enhance its nutritional value with a diet high in PUFA prior to harvesting, in order to improve hatchery production.     

Marker technique for investigating gut throughput rates in coral reef fishes

Artemia sp. shells were evaluated to determine their accuracy for tracing the passage of algal filaments through the gut of the damselfish Pomacentrus amboinensis Bleeker, 1868 (family Pomacentridae), an omnivorous coral reef fish. An automatic faeces-collection apparatus enabled the quantitative collection of markers and faeces in the laboratory. Defecation rates were similar for light and heavy doses of Artemia sp. shells and controls, indicating no detrimental effects of Artemia sp. shells on the gut throughput rate of P. amboinensis. In addition, similar rates and patterns of the passage of Artemia sp. shells and the algal markers Enteromorpha sp. and Lyngbya sp. indicated that Artemia sp. shells provide a reliable representation of the throughput rate of algal filaments. The mean throughput time of P. amboinensis was 4.6 h ±0.3 SE, with a modal recovery time of 4 h. Laboratory throughput estimates were validated by comparing the distribution patterns of Artemia sp. shells in the dissected gut of specimens administered markers in the laboratory and field. In addition, the retention of markers in the stomach of P. amboinensis suggested a likely site of prolonged processing. Received: 24 October 1996 / Accepted: 18 March 1997     

Nitrogen balance in marine fish larvae: influence of developmental stage and prey density

The utilization and fate of nitrogen in larvae of plaice (Pleuronectes platessa), blenny (Blennius pavo) and herring (Clupea harengus), from the stage of first-feeding to metamorphosis, was examined under laboratory conditions. Rates of ammonia excretion, primary amine defaecation, and growth in terms of protein-nitrogen were monitored throughout larval life. Data were used to calculate daily ration, the coefficient of nitrogen utilization (absorption efficiency), and gross and net growth efficiencies. The developmental pattern of nitrogen balance was similar for plaice and blenny larvae. These species showed increasing growth efficiency (k₁: 55 to 80%) with decreasing weight-specific waste nitrogen losses with age. Absorption efficiencies. were high (83 to 98%) in plaice and blenny larvae, and tended to increase with development in the former species. Ration relative to body weight decreased with growth in both species. Herring larval development, although at a slower rate than blenny and plaice, appeared normal up to 33 d, after which high mortality occurred. Absorption efficiency in this species tended to decline (83 to 43%) with age, until metabolic costs exceeded the absorbed ration and growth ceased. Artemia sp. nauplii proved a suitable food source for the rearing of plaice and blenny larvae, but this diet may have long-term toxicity or deficiency effects on herring. Availability and density of food affected nitrogen balance in the larvae of all three species. Feeding stimulated the output of wastes in excretion and defaecation by a factor of up to ten times the 12-h non-feeding basal rates. Waste nitrogen output reached a peak some 2 to 3 h after commencement of feeding and returned slowly to the baseline in 5 to 10 h after cessation of feeding. There was an asymptotic increase in ration, ammonia output and growth of larvae as prey density increased. Ration saturated at a higher prey density (>4 prey ml^-1) than either growth or excretion rate (1 prey ml^-1). Thus the efficiency with which food is absorbed and utilized for growth must eventually decline in response to high prey density. The idea that larval fish are adapted to maximize ingestion and growth rate, rather than optimize growth efficiency and thus to respond to prey occurring in either low density or in occasional patches, is supported by these results.     

Nitrogen and energy loss via nonfaecal and faecal excretion in the marine teleost Lithognathus lithognathus

Nitrogen excretion and assimilation efficiencies of individual Lithognathus lithognathus (Cuvier 1830), a marine teleost from high energy surf zones in Algoa Bay, South Africa, were determined under laboratory conditions in 1985. Nonfaecal-nitrogen excreted by starved and fed L. lithognathus consists mainly of ammonia with urea and amino acids as secondary excretory products. Ammonia excretion rates were temperature dependant with the excretion rate of starved fish significantly lower than those of fed fish, at all three experimental temperatures. The mass component b of the mass/ammonia excretion equation was temperature independent and ranged from 0.651 to 0.700 and 0.589 to 0.635 for starved and fed fish respectively. The mean percentage of food energy lost via dissolved nonfaecal excretory products (exogenous plus endogenous) was 6.11±6.07%. Assimilation efficiencies ranged from 70.75 to 99.29% for dry matter and from 95.72 to 99.58% on an energy basis. The combined nonfaecal and faecal energy loss was calculated at 11.87% of the ingested energy. The benthic feeding ichthyofauna recycle 255 g total nitrogen per metre strip per year which constitutes 2% of total phytoplankton nitrogen requirements of the surf zone.     

Influence of environmental salinity on oxygen consumption and ammonia excretion of the arctic under-ice amphipodOnisimus glacialis

Changes in salinity affect the metabolic rate of the sympagic amphipodOnisimus glacialis collected from the Barents Sea in 1986 and 1988. When transferred from 35 to 5 ppt S, oxygen consumption and ammonia excretion both increase three-fold during the first 5 h of exposure, and they remain high throughout the rest of the experimental period (26 h). During 24-h acclimation to various salinities (5 to 45 ppt), the amphipods exhibit a respiratory and excretory response to hyper- and hypoosmotic stress; however, a rather constant O:N atomic ratio (around 15) was obtained at the experimental salinities, indicating protein/lipids as metabolic substrate. Both rates of oxygen consumption and ammonia excretion increased with an increasing osmotic difference (0 to 650 mOsm) between the haemolymph and the environmental medium, indicating higher energy requirements for osmotic and ionic regulation at low salinities. In amphipods abruptly transferred from 35 to 5 ppt, a minor decrease of the haemolymph sodium concentrations together with an increased ammonia excretion output indicate a counter-ion regulation of NH ₄ ⁺ and Na⁺ during hyposmotic stress.     

Influence of temperature changes on oxygen uptake and ammonia and phosphate excretion,in relation to body size and weight,in Oikopleura dioica (Appendicularia)

The relationship between the rates of oxygen consumption, ammonia and phosphate excretion of a pelagic tunicate, the larvacean Oikopleura dioica Fol, 1872 were assessed as a function of size, dry weight and ash-free dry weight at 15°, 20° and 24°C. O. dioica has higher respiration and excretion rates than copepods of similar weight, but the weight exponent of the allometric power function: Y=aX ^b is similar to that of other poikilotherms. Temperatures above 20°C have a depressing effect on respiration and ammonia excretion. 90% of the variance in metabolic rates is explainable by body mass and temperatures Q₁₀ values for oxygen consumption, ammonia and phosphate excretion, respectively, are 2.45, 1.86 and 1.75 between 15° and 20°C, and 3.75, 2.90 and 3.60 between 20° and 24°C. Metabolic quotients (O:N, O:P, N:P) indicate a protein-oriented diet. The results of this study suggest weak metabolic regulation in O. dioica, an energetic strategy which allows an immediate response to favourable changes in feeding conditions.     

The effect of laboratory conditions on the extrapolation of experimental measurements to the ecology of marine zooplankton. IV. Changes in respiration and excretion rates of boreal zooplankton species maintained under fed and starved conditions

Herbivorous zooplankton species (Calanus plumchrus, Paracalanus parvus and Euphausia pacifica) and carnivorous species (Parathemisto pacifica and Pleurobrachia pileus) collected from Saanich Inlet, British Columbia, Canada, were maintained in the laboratory under fed and starved conditions. Respiration rate and excretion rates of ammonia and inorganic phosphate were measured successively on the same batch populations of each species in different feeding conditions. Respiration rate remained at a constant level or increased during the feeding experiment but decreased progressively in starved individuals. Herbivorous, but not carnivorous, species showed a rapid decrease in both excretion rates for the first few days of an experiment irrespective of feeding conditions. However, the general level of excretion rates of fed specimens was higher than that of starved ones. The O:N, N:P and O:P ratios were calculated from respiration, ammonia excretion and phosphate excretion and discussed in relation to metabolic substrates of animals during the experiment. A marked difference was shown in the O:N ratio between fed hervivores (>16) and fed carnivores (7 to 19), suggesting highly protein-oriented metabolism in the latter. One unknown factor causing variation in excretion rates is speculated to be the physiological stress on animals during sampling from the field. It is suggested that the laboratory measurement of realistic excretion rates of zooplankton is difficult owing to their large fluctuations, but this is not the case with respiration rate.     

Nutrient transfer in a marine mutualism: patterns of ammonia excretion by anemonefish and uptake by giant sea anemones

Many symbioses involve multiple partners in complex, multi-level associations, yet little is known concerning patterns of nutrient transfer in multi-level marine mutualisms. We used the anemonefish symbiosis as a model system to create a balance sheet for nitrogen production and transfer within a three-way symbiotic system. We quantified diel patterns in excretion of ammonia by anemonefish and subsequent absorption by host sea anemones and zooxanthellae under laboratory conditions. Rates of ammonia excretion by the anemonefish Amphiprion bicinctus varied from a high of 1.84 μmole g⁻¹ h⁻¹ at 2 h after feeding, to a basal rate of 0.50 μmole g⁻¹ h⁻¹ at 24–36 h since the last meal. Conversely, host sea anemones Entacmaea quadricolor absorbed ammonia at a rate of 0.10 μmole g⁻¹ h⁻¹ during the daytime in ammonia-enriched seawater, but during the night reduced their absorption rate to near zero, indicating that ammonia uptake was driven by zooxanthella photosynthesis. When incubated together, net ammonia excretion was virturally zero, indicating that host anemones absorbed most of the ammonia produced by resident fish. Adult anemonefish weighed about 11 g under laboratory conditions, but on the coral reef may reach up to 64 g, resulting in a maximal potential ammonia load of >200 μmole h⁻¹ produced by two adult fish during daylight hours. In contrast, host sea anemones weighed about 47 g in the laboratory, but under field conditions, large individuals may reach 680 g, so their maximal ammonia clearance rates may reach about 70 μmole h⁻¹ during the daytime. As such, the ammonia load produced by adult anemonefish far exceeds the clearance rate of host anemones and zooxanthellae. Ammonia transfer likely occurs mainly during the daytime, when anemonefish consume zooplankton and excrete rapidly, and in turn the zooxanthellae are photosynthetically active and drive rapid ammonia uptake. We conclude that zooplanktivorous fishes that form mutualisms with coral reef cnidarians may serve as an important link between open water and benthic ecosystems, through the transfer of large quantities of nutrients to zooxanthellate hosts, thus enhancing coral reef productivity.     

Experimental evaluation of the energy balance in Octopus vulgaris, fed ad libitum on a high-lipid diet

A complete energy balance equation was estimated for the common octopus Octopus vulgaris at a constant temperature of 20°C, fed ad libitum on anchovy fillet (Engraulis encrasicolus). Energy used for growth and respiration or lost with faeces and excreted ammonia was estimated, along with total energy consumption through food, for six specimens of O. vulgaris (with masses between 114 and 662 g). The energy balance equation was estimated for the specimens at 10-day intervals. During each 10-day interval, food consumed, body mass increase and quantity of faeces voided were measured. The calorific values of octopus flesh, anchovy flesh and faeces were measured by bomb calorimetry. Oxygen consumption and ammonia excretion rates were monitored for each specimen during three 24-h experiments and daily oxygen consumption and ammonia excretion were estimated. It was found that 58% of the energy consumed was used for respiration. The amount of energy invested in somatic and gonadal growth represented 26% of the total energy budget. The energy discarded through faeces was 13% of consumed energy. The estimated assimilation efficiency (AE) values of O. vulgaris feeding on anchovy (80.9–90.7%) were lower than the AE values estimated for other cephalopod species with different diets of lower lipid content such as crabs or mussels. Specific growth rates (SGR) ranged 0.43–0.95 and were similar to those reported for other high-lipid diets (bogue, sardine) and lower than SGR values found for low-lipid, high-protein diets (squid, crab, natural diet). Ammonia excretion peak (6 h after feeding) followed the one of oxygen consumption (1 h after feeding). The values of atomic oxygen-to-nitrogen (O:N) ratio indicated a protein-dominated metabolism for O. vulgaris.     

Effects of salinity and dietary DHA (22:6n - 3) content on lipid composition and performance of Penaeus kerathurus postlarvae

A two-way ANOVA experiment was designed to study the effects of salinity and dietary docosahexaenoic acid (DHA; 22:6n-3) on lipid composition and performance of postlarvae from the marine shrimp Penaeus kerathurus (Forskål, 1775). Shrimp were reared from 1- to 8-d-old postlarvae at 35 and 25‰S with Kelko-enriched Artemia sp. [20.0 μg (n-3)?HUFA mg^?1 dry weight; 9.1 μg DHA mg^?1 dry weight] and nonenriched Artemia sp. [14.2 μg (n-3)?HUFA mg^?1 dry weight; 0.3 μg DHA mg^?1 dry weight]. Dietary DHA content did not affect either total length or survival but influenced the nutritional status represented by condition indices (triacylglycerol/total polar lipid and triacylglycerol/free cholesterol) of 8-d-old postlarvae at the end of the experiment. Culture salinity affected final total length and condition indices but did not show any effect on survival in the different experimental treatments. The interaction of dietary DHA and culture salinity was not significant for total length and survival but was significant for both condition indices used. P. kerathurus 8-d-old postlarvae showed better growth, survival and nutritional condition when reared at 35‰S and when fed on Kelko-enriched Artemia sp., but the differences with postlarvae from other treatments were very poorly marked. The results demonstrate that 8-d-old postlarvae may have sufficiently developed osmoregulatory capabilities to resist 25‰S under good conditions, although (n-3) HUFA-enriched diets may also enhance osmotic stress resistance, general performance and disease resistance.     

Nitrogen regeneration by two surf-zone mysids,Mesopodopsis slabberi andGastrosaccus psammodytes

Nitrogen regeneration by two surf zone mysids,Mesopodopsis slabberi andGastrosaccus psammodytes, was determined under laboratory conditions. The mysids were collected from the lower Sundays River estuary, South Africa, from early spring 1984 to late summer 1985. The forms of nitrogen excreted and the effects of mass, temperature and feeding on excretion rate were determined for each species at three experimental temperatures. Comparison of the forms of nitrogen excreted revealed only slight differences between species, with ammonia the major form and urea and amino acids the secondary excretory products in both cases. Mass significantly influenced the rate of ammonia excretion at all experimental temperatures, with no significant difference in slope (common b=0.602) detected between species. During the day sediment deprivation resulted in a 15% and 20% increase in mean ammonia excretion rates of juvenile and adultG. psammodytes respectively, whereas no significant differences were found at night. The mean ammonia excretion rates of fedM. slabberi andG. psammodytes were 2 and 2.5 times higher than starved excretion rates, respectively.G. psammodytes andM. slabberi recycle 139 to 150 g N per running meter of surf zone per year and 1 007 to 1 208 g N m^-1 yr^-1, respectively. Togehter this constitutes 10% of total phytoplankton nitrogen requirements in the surf zone.     

Variation in urea excretion in the gulf toadfishOpsanus beta

Under long-term (24 h) control measurements, significant urea was excreted (15 to 90% of excreted nitrogen) byOpsanus beta (Goode and Bean) collected in 1989 from Biscayne Bay, Florida, USA. Urea excretion rates and plasma urea concentrations were not affected by antibiotic treatments which decreased intestinal microbe populations. These results suggest that nitrogen recycling by gut microbe urease is probably not significant in this species. Urea excretion rates increased significantly following 8 h of air-exposure and in response to high levels of NH₄Cl. These results suggest that urea is synthesized and excreted by the toadfish primarily in situations that limit ammonia excretion. Thus, the ornithineurea cycle in the toadfish liver primarily maintains low concentrations of ammonia within the fish. High levels of variability in urea excretion rates and variation in response to air-exposure suggest that urea synthetic rates are affected by immediate past environmental conditions.     

Ecological growth strategies in the seaweeds Gracilaria foliifera (Rhodophyceae) and Ulva sp. (Chlorophyceae): Soluble nitrogen and reserve carbohydrates

The seaweeds Gracilaria foliifera (Rhodophyceae) and Ulva sp. (Chlorophyceae) were grown in an outdoor continuous-flow system at both ambient incident light (I₀) and 0.13 I₀. During the winter, both species accumulated substantial soluble nitrogen reserves (up to 1020 g-at N·g dry wt^-1 in G. foliifera and 630 g-at N·g dry wt^-1 in Ulva sp.). The rate at which these N reserves were depleted was proportional to the growth rate. Seaweeds grown at 0.13 I₀ had lower growth rates and higher levels of soluble tissue N than plants grown at I₀. During the spring-summer growing season, peaks in tissue N followed nutrient peaks in the ambient seawater. Ulva sp. had higher nutrient uptake and growth rates than G. foliifera and showed greater fluctuations in soluble tissue N. This may characterize opportunistic seaweed species with high biomass turnover rates. At I₀, the levels of starch (up to 340 mg·g dry wt^-1 in G. foliifera and 170 mg·g dry wt^-1 in Ulva sp.) were highest during the spring and summer. During this period, fluctuations in starch content were inversely related to growth rate and soluble tissue N. Seaweeds grown at 0.13 I₀ did not accumulate starch. Neither species was found to overwinter with starch reserves.     

Physiological and antioxidative response of Brassica nigra (L.) to ZnO nanoparticles grown in culture media and soil

Abstract

To investigate metal nanoparticle-induced phytotoxicity, Brassica nigra seeds were exposed to 50–1000?mg L^?1 ZnO nanoparticles in culture media and 100–1000?mg kg^?1 in soil. Plant length and weight were adversely affected in culture conditions, but with soil the effect was not significant. Determination of the radical-scavenging potential revealed that soil grown plants were less stressed than plants grown on culture medium. The total antioxidant and reducing power potential of soil grown plants were less variable compared to plants grown on culture medium. Total phenolic and flavonoid concentrations varied in plants, which changed with the nanoparticle’s concentrations in medium and soil. High performance liquid chromatography analysis showed that rutin was the major antioxidative molecule that significantly increased in nanoparticles-stressed B. nigra plants.     

Light intensity and the feeding behaviour of herring,Clupea harengus

An infra-red sensitive video-recording technique was used to study the effects of darkness and light intensities from 0.0001 to 270 photopic lx on the feeding behaviour of herring (Clupea harengus L.). When offered natural zooplankton, consisting of a mixture ofCalanus finmarchicus, Euchaeta norvegica, Oithona similis, Balanus sp. nauplii, and crustacean nauplii as prey, the fish fed by biting (snapping) at light intensities above a threshold of 0.001 lx and were size-selective, taking the larger organisms first. When fed on pure cultures of CaliforniaArtemia sp. nauplii (San Francisco Bay brand), the threshold light intensity was 0.01 lx. Swimming speed increased with increasing light intensity when the fish were actively feeding by biting. When the fish were filter-feeding on high densities ofArtemia sp. nauplii in the light, they continued to school and swimming speed was not related to light intensity.     

Metabolism and body composition of two euphausiids (Euphausia superba and E. crystallorophias) collected from under the pack-ice off Enderby Land,Antarctica

Oxygen consumption, ammonia excretion and phosphate excretion rates were measured for Euphausia superba and E. crystallorophias captured under the pack-ice off Enderby Land, Antarctica, during November 1985. Water, ash, carbon, nitrogen and phosphorus composition were also determined. Compared with summer data, body composition of E. superba at this time of year was characterized by low carbon (40.2 to 40.7% of total dry wt), high nitrogen (11.8 to 12.0%), high phosphorus (1.2%) and high water (80.6 to 81.7% of total wet wt) content. Metabolic rates, expressed as percentage daily losses of body carbon, nitrogen and phosphorus were 1.3 to 1.6%, 0.38 to 0.42% and 1.9 to 2.2%, respectively; these fall within the ranges of summer data. E. superba fed on algae growing on the bottom of the ice, but body compositional features of this species suggest limited contribution of ice-algae to nutrition. Compared to E. superba, E. crystallorophias displayed greater metabolic rates and much higher body carbon content (40.9 to 45.0%), implying that feeding conditions under the ice were better suited to the requirements of E. crystallorophias. The only gravid females found belonged to E. crystallorophias.     

The influence of fresh weight and water temperature on metabolic rates and the energy budget of Meretrix meretrix Linnaeus

Meretrix meretrix L. was held in the laboratory under simulated natural conditions to measure specific physiological parameters of its energy budget. O₂ consumption rate, NH₃ excretion rate (NR), ingestion rate, faeces excretion rate and scope for growth (SFG) were negatively related in an exponential manner to the fresh weight of the clams at all water temperatures, while almost all metabolic rates of the clams were positively related in an exponential or e-exponential manner with water temperature. However, the co-relationship between metabolic rates and water temperature was not as close as that between metabolic rates and fresh weight of the clam. The combined effect of fresh weight and water temperature was observed on all metabolic rates except for NR and SFG. At all culture temperatures and for all fresh weights of clams used, respiration took the largest percentage of ingested energy (41.5–51.2%), faeces excretion was second (31.0–42.3%), growth third (12.1–15.5%) and urine production last (2.1–5.6%).     

Effects of water motion and prey behavior on zooplankton capture by two coral reef fishes

Water motion is an important factor affecting planktivory on coral reefs. The feeding behavior of two species of tube-dwelling coral reef fish (Chaenopsidae) was studied in still and turbulent water. One species of blenny, Acanthemblemaria spinosa , lives in holes higher above the reef surface and feeds mainly on calanoid copepods, while a second, A. aspera , lives closer to the reef surface, feeds mainly on harpacticoid copepods, and is exposed to less water motion than the first. In the laboratory, these two blenny species were video recorded attacking a calanoid copepod ( Acartia tonsa, evasive prey) and an anostracan branchiopod (nauplii of Artemia sp., passive prey). Whereas A. spinosa attacked with the same vigor in still and turbulent water, A. aspera modulated its attack with a more deliberate strike under still conditions than turbulent conditions. For both fish species combined, mean capture success when feeding on Artemia sp. was 100% in still water and dropped to 78% in turbulent water. In contrast, when feeding on Acartia tonsa, mean capture success was 21% in still water and rose to 56% in turbulent water. We hypothesize that, although turbulence reduces capture success by adding erratic movement to Artemia sp. (passive prey), it increases capture success of Acartia tonsa (evasive prey) by interfering with the hydrodynamic sensing of the approaching predator. These opposite effects of water motion increase the complexity of the predator-prey relationship as water motion varies spatially and temporally on structurally complex coral reefs. Some observations were consistent with A. aspera living in a lower energy benthic boundary layer as compared with A. spinosa: slower initial approach to prey, attack speeds modulated according to water velocity, and lower proportion of approaches that result in strikes in turbulent water.Communicated by P.W. Sammarco, Chauvin     

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