Biochemical compositions of two dominant bloom- forming species isolated from the Yangtze River Estuary in response to different nutrient conditions

Variations of cellular total lipid, total carbohydrate and total protein content of two dominant bloom-forming species (Skeletonema costatum and Prorocentrum donghaiense) isolated from the Yangtze River Estuary were examined under six different nutrient conditions in batch cultures. Daily samples were collected to estimate the cell growth, nutrient concentration and three biochemical compositions content during 7 days for S. costatum and the same sampling procedure was done every other day during 10 days for P. donghaiense. Results showed that for S. costatum, cellular total lipid content increased under phosphorus (P) limitation, but not for nitrogen (N) limitation; cellular carbohydrate were accumulated under both N and P limitation; cellular total protein content of low nutrient concentration treatments were significantly lower than that of high nutrient concentration treatments. For P. donghaiense, both cellular total lipid content and total carbohydrate content were greatly elevated as a result of N and P exhaustion, but cellular total protein content had no significant changes under nutrient limitation. In addition, the capability of accumulation of three biochemical constituents of P. donghaiense was much stronger than that of S. costatum. Pearson correlation showed that for both species, the biochemical composition of three constituents (lipid, carbohydrate and protein) had no significant relationship with extracellular N concentration, but had positive correlation with extracellular and intracellular P concentration. The capability of two species to accumulate cellular total lipid and carbohydrate under nutrient limitation may help them accommodate the fluctuating nutrient condition of the Yangtze River Estuary. The different responses of two species of cellular biochemical compositions content under different nutrient conditions may provide some evidence to explain the temporal characteristic of blooms caused by two species in the Yangtze River Estuary.     

Studies in the biochemistry of cirripede eggs. VI. Changes in the general biochemical composition during development of Tetraclita squamosa rufotincta Pilsbry,Balanus perforatus Brug., and Pollicipes cornucopia Darwin

The carbohydrate, protein, lipid, total RNA and DNA at four stages in the development of the eggs of Tetraclita squamosa rufotincta Pilsbry, Balanus perforatus Brug., and Pollicipes cornucopia Darwin have been determined. The initial caloric content varies with species, that of the large egg of Tetraclita being extremely high; on a relative volume-specific basis, however, differences, although still present, are much less variable. A comparison has been made with other species. Those eggs in which lipid predominates over protein in Stage I lose more lipid during development. The relatively large quantities of reserves in Tetraclita may serve as metabolic substrate during the development of the planktonic larvae under nutrient-poor conditions.     

The biochemical composition of the larvae of two strains of Artemia salina (L.) reared on two different algal foods

A sequential carbohydrate, protein, and lipid method of analysis has been used to determine the biochemical composition of freshly hatched and 48-h old larvae of two strains of the brine shrimp Artemia salina (L.). During a 48-h starvation period the percentage of carbohydrates and lipids of freshly hatched larvae decreases whereas the ash content increases by 40–100%. When fed with dried Scenedesmus or dried Spirulina for 2 days after hatching the protein level of the larvae increases significantly and the relative increase in ash content is lower than in the case of starvation.Amino acid analyses of the algal food and the unfed and fed larvae did not show any change except for the absence (below detection) of methionine in the starved nauplii.The fatty acid pattern of 48-h old Artemia larvae is different from that of freshly hatched nauplii both in unfed and fed larvae; in the latter case it seems to be determined to a large extent by the fatty acid composition of the food.     

Organic,inorganic, and caloric composition of eggs,pentaculae, and adults of the brooding sea cucumber Cucumaria curata cowles (Echinodermata: Holothuroidea)

Levels (percentage composition) of water, ash, carbohydrate, lipid, protein, and calories were determined for eggs, pentaculae, and adults of the sea cucumber Cucumaria curata Cowles. Component contents (μg/individual) were calculated for eggs and pentaculae. During the 28 days of development to hatching, the large yolky eggs gain water and ash, the total dry weight increasing from 169 to 190 μg/egg during embryogenesis. There were no statistically significant changes in lipid, protein, and caloric contents during embryogenesis, but carbohydrate decreased by 0.82 μg/egg.The decrease in carbohydrate is sufficient to account for estimated embryonic energy requirements. Based on the utilization of carbohydrate, embryos of C. curata show a nutritional pattern similar to that of the planktonic embryos of sea urchins and different from that of embryos developing from terrestrial eggs, freshwater eggs, and planktonic and demersal marine eggs.Although broods varied widely in egg number and mean egg dry weight, C. curata gives eggs which contain a constant proportion of organic components.Levels of ash, water, and protein in the adults exceeded those in the pentacula, and lipid comprises a much smaller proportion of the adult body than it did of the pentacula.     

In Vivo Growth of Romanomermis culicivorax: Biochemical Changes During Parasitism

Biochemical analyses of total protein, lipid, carbohydrate, DNA, amino acid, and length, width, and dry weight measurements are reported for different stages of Romanomermis culicivorax cultured in the mosquito, Culex pipiens. The Bradford technique for assaying total protein was the most sensitive and reliable biochemical technique tested for assaying in vivo growth of R. culicivorax. Increases in total protein, lipid, carbohydrate, and dry weight during growth from preparasite to postparasite were greater than 6,900-fold for females and 2,300-fold for males. DNA increased 650-fold and 233-fold during development to female and male postparasites, respectively. The proportions of amino acids for preparasites were significantly different (P ≤ 0.01) from female and male postparasites for all amino acids tested, except methionine and tyrosine. Female and male postparasites were similar in protein, lipid, carbohydrate, DNA, and most amino acid proportions, but were significantly different in relative concentrations of serine, glycine, and alanine (P ≤ 0.01). Preliminary results suggest that the use of amino acid ratios from female postparasites improves the in vitro culture performance of R. culicivorax.     

Storage and mobilisation of nutriment for uterine milk synthesis by Glossina morsitans

Nitrogen content of eggs and larvae of Glossina morsitans was a constant proportion of dry weight and equivalent to ca. 55% protein assuming tsetse proteins contain 16% nitrogen. The larval gut content (uterine milk) contained 40% protein. Fatty acid composition of lipids in the milk and in the larval body was similar, with Palmitic (35–38%), Palmitoleic (31–35%) and Oleic acid (23–25%) predominating. Results support the hypothesis that uterine milk contains both protein and lipid and that its composition is relatively constant throughout the period of its synthesis and secretion.Patterns of incorporation of radioactivity by fertilized adult females from injected [¹⁴C]-leucine changed throughout a pregnancy cycle. High levels of incorporation into lipid (22–30%) during early pregnancy fell to around 10% during late pregnancy. Over the same period low levels of incorporation into protein (5%) increased to 15%. Results support the hypothesis that uterine milk is synthesized from a lipid store laid down in early pregnancy coupled with protein derived largely from blood meals ingested later. Such a system would not require the insect to store proteins for larval growth and is economical in terms of energy expenditure.     

Utilization of pre-existing energy stores of female Aedes aegypti mosquitoes during the first gonotrophic cycle

Pre-existing energy reserves may play an important role in regulating the utilization of blood meal proteins in female anautogenous mosquitoes. Determining the fate of reserves derived from the sugar meal and larval food during the first gonotrophic cycle would help to elucidate the relative contributions of larval and adult nutrition to survival and reproduction. We measured the allocation of pre-blood-meal reserves to egg production or energy production during the first gonotrophic cycle by using [14C]-labeled female Aedes aegypti mosquitoes. Feeding adults [3,4-14C]-glucose labeled the glycogen and sugar stores (approximately 50%), lipid stores (approximately 25%), and protein and amino acid stores (approximately 25%). During the first gonotrophic cycle, about 60% of the glycogen and sugar stores were metabolized and all were used for energy production. About 33% of the labeled protein and 72% of the labeled amino acid stores were metabolized, with about 9% being transferred to the eggs and the rest oxidized. About 30% of the lipid was metabolized, with about 65% being transferred to the eggs and the rest oxidized. Feeding [1-14C]-oleic acid to larvae effectively labeled adult lipid stores with about 75% of the label in lipid stores and 16% in proteins and 6% in glycogen. During the first gonotrophic cycle, about 35% of the labeled lipid stores were metabolized, with equal amounts being oxidized and transferred to the eggs. None of the other maternal stores labeled by fatty acid were metabolized during the first gonotrophic cycle. These results show that carbohydrate reserves are a critical source of energy during the first gonotrophic cycle, while lipid reserves are used equally for energy production and provisioning the eggs.     

Comparative larval energetics of an ophiuroid and an echinoid echinoderm

The morphologically convergent larvae of the echinoderm classes Ophiuroidea and Echinoidea have been suggested to be functionally dissimilar when it comes to their capacities to feed, but little is known about whether these larvae are similar in terms of energetics. Here, we compare the energetics of early development of a tropical ophiuroid, Ophiocoma alexandri, and a temperate to tropical echinoid, Arbacia punctulata, two species with similarly sized eggs. Measurements of respiration and constituent analyses were performed on eggs and unfed larvae of both species. Members of both species showed an increase in oxygen consumption during morphogenesis followed by a lower, static rate once morphogenesis was complete (3 d for O. alexandri and 1.3 d for A. punctulata). Compared to the echinoid larvae, the ophiuroid larvae developed more slowly and had peak respiration rates that were 3.1× lower. Eggs of O. alexandri contained significantly more protein and significantly less triacylglycerol than eggs of A. punctulata. Energy utilization, as calculated via respiration measurements, closely matched decreases in energy content from the eggs to larvae as measured with biochemical constituent assays. Larvae of A. punctulata used 1.4× more energy to reach the pluteus stage than larvae of O. alexandri, and used 4× more energy during the first 9 d of larval life. These data suggest that echinoid larvae require more energy to develop to the feeding stage than ophiuroid larvae, and likewise have higher requirements for maintenance metabolism. Ophiuroid larvae may be more tolerant of low food levels due to their very low metabolic rates, but this advantage may be offset by their slower rate of development.     

Effects of reduced salinity on the biochemical composition (lipid, protein) of zoea 1 decapod crustacean larvae

Effects of reduced salinities on dry weight (DW) and biochemical composition (total lipid and protein contents) of zoea 1 larvae were evaluated in four decapod crustacean species differing in salinity tolerance (Cancer pagurus, Homarus gammarus, Carcinus maenas, Chasmagnathus granulata). The larvae were exposed to two different reduced salinities (15‰ and 25‰ in C. granulata, 20‰ and 25‰ in the other species) for a long (ca. 50% of the zoea 1 moulting cycle) or a short period (16 h, starting at ca. 40% of the moulting cycle), while a control group was continually maintained in seawater (32‰).In general, the increments in dry weight, lipid and protein content were lower at the reduced salinities than in the control groups. In the zoea 1 of H. gammarus (stenohaline) and C. pagurus (most probably also stenohaline), the lipid and protein contents varied greatly among treatments: larvae exposed to low salinities exhibited very low lipid and protein contents at the end of the experiments compared to the controls. In some cases, there were negative growth increments, i.e. the larvae had, after the experimental exposure, lower lipid and protein contents than at the beginning of the experiment. C. maenas (moderately euryhaline) showed a lower variation in protein and lipid content than the above species. The zoea 1 of C. granulata (fairly euryhaline) showed the lowest variability in dry weight, protein and lipid content. Since salinity tolerance (eury- v. stenohalinity) is associated with the osmoregulatory capacity, our results suggest a relationship between the capability for osmoregulation and the degree of change in the biochemical composition of larvae exposed to variable salinities.Besides larval growth of these species should be affected by natural reductions of salinity occurring in coastal areas at different time scales. These effects may be potentially important for population dynamics since they should influence the number and quality of larvae reaching metamorphosis.     

The biochemical composition of krill, Euphausia superba Dana,from South Georgia

Krill, Euphausia superba Dana, sampled from waters around South Georgia in 1978 contained 10–11% protein, 2–6% lipid, 0.3–0.6% carbohydrate, 2% chitin, and 3–4% mineral ash (all mean values, % fresh weight).Lipid content varied greatly with sexual maturity: males contained 2–4% lipid, immature animals 4% (both increasing to 5–6% later in the season) and mature females 5–6% (although some contained as much as 9%). Gravid females lost ≈60% of their lipid at spawning, and a biochemical estimate of fecundity gave values in the range 7000 to 15 000.The major lipid classes were phospholipid, triacylglyceropl, and free sterol, and there was 1–2% wax ester. The mean pigment content was 21.5 μg/g fresh weight. Triacylglycerol fatty acids were low in polyenoic acids and contained up to 4% phytanic acid; compositions were variable and showed the probable influence of dietary input. Phospholipids were rich in polyenoic acids, especially 20 : 5ω3 and 22 : 6ω3, and usually had 18 : 1ω7 > 18 : 1ω9. Ovarian triacylglycerol contained almost no polyenoic acids, but ovarian phospholipid was fairly unsaturated.These results are discussed in relation to the Antarctic environment, and compared with the results of previous work on caridean decapods.     

Drosophila melanogaster larvae make nutritional choices that minimize developmental time

Organisms from slime moulds to humans carefully regulate their macronutrient intake to optimize a wide range of life history characters including survival, stress resistance, and reproductive success. However, life history characters often differ in their response to nutrition, forcing organisms to make foraging decisions while balancing the trade-offs between these effects. To date, we have a limited understanding of how the nutritional environment shapes the relationship between life history characters and foraging decisions. To gain insight into the problem, we used a geometric framework for nutrition to assess how the protein and carbohydrate content of the larval diet affected key life history traits in the fruit fly, Drosophila melanogaster. In no-choice assays, survival from egg to pupae, female and male body size, and ovariole number – a proxy for female fecundity – were maximized at the highest protein to carbohydrate (P:C) ratio (1.5:1). In contrast, development time was minimized at intermediate P:C ratios, around 1:2. Next, we subjected larvae to two-choice tests to determine how they regulated their protein and carbohydrate intake in relation to these life history traits. Our results show that larvae targeted their consumption to P:C ratios that minimized development time. Finally, we examined whether adult females also chose to lay their eggs in the P:C ratios that minimized developmental time. Using a three-choice assay, we found that adult females preferentially laid their eggs in food P:C ratios that were suboptimal for all larval life history traits. Our results demonstrate that D. melanogaster larvae make foraging decisions that trade-off developmental time with body size, ovariole number, and survival. In addition, adult females make oviposition decisions that do not appear to benefit the larvae. We propose that these decisions may reflect the living nature of the larval nutritional environment in rotting fruit. These studies illustrate the interaction between the nutritional environment, life history traits, and foraging choices in D. melanogaster, and lend insight into the ecology of their foraging decisions.     

Egg composition and reproductive investment in aphidophagous ladybird beetles (Coccinellidae: Coccinellini): egg development and interspecific variation

Abstract Most studies of insect reproductive allocation concentrate on propagule size and number and very few consider egg composition, which is likely to be equally important. In the present study, data are provided on changes in egg lipid, glycogen, free carbohydrate and protein during embryonic development of the aphidophagous ladybird Adalia bipunctata (L.) and the compositions of A. bipunctata, Adalia decempunctata and Anisosticta novemdecimpunctata eggs are compared. In A. bipunctata, egg mass, lipid and glycogen decline strongly during development and egg protein declines more weakly. Free carbohydrate declines early in egg development and increases at egg hatching. Lipid is energetically the most important developmental fuel, although approximately half of the initial egg lipid remains in the neonate larva. Across the three species, energy per unit egg mass is lowest in the least specialized species, A. bipunctata, which also has the largest eggs, and is highest in the most specialized, An. novemdecimpunctata, which has the smallest eggs. Two possible explanations for the observed pattern are discussed: (i) species laying smaller eggs may incur higher developmental costs per unit mass than species laying larger eggs and (ii) more specialized species, which reproduce at lower aphid densities, may provision neonate larvae better to facilitate location and capture of aphids.     

Seasonal changes in the biochemistry of lake seston

1. The quantity of seston was measured and the elemental carbon, nitrogen and phosphorus (C, N, P) and biochemical composition (carbohydrate, protein, lipid) of the < 53 μm size fraction in three temperate lakes during one year was analysed. The lakes differed in nutrient concentration and were characterized as oligotrophic, mesotrophic and eutrophic. Linear regression analyses defined associations between seston composition and either lake trophic status, depth or season. 2. The concentration of particulate organic seston was greatest during spring and autumn and lowest during the clear water period in early summer. Seasonal patterns in seston elemental and biochemical percentage composition (quality) were observed to be independent of differences in seston quantity. 3. Concentrations of seston C, N and P were high in most cases in the spring and autumn and low in summer. Concentrations of P were particularly high during late summer and early autumn in the metalimnion, perhaps because of recovery of P from anaerobic sediments and hypolimnetic waters. Because seston C and N did not increase as markedly as P, C : P and N : P ratios both declined in the autumn. Primary production was thought to be co-limited by N and P in all three of these lakes; however, the data suggested that N might be more important as a major limiting nutrient in the eutrophic lake as the metalimnion increased in depth in late summer and autumn. 4. Concentrations of protein, carbohydrate, polar lipid and triglyceride generally increased with lake type as expected (greatest in the eutrophic lake), but showed no relationship with water depth. As the year progressed, no significant changes were measured in protein and carbohydrate concentrations; however, the concentration of polar lipid decreased and triglyceride increased significantly with time of year. 5. The biochemical composition of seston varied during the year and among lakes; for example, in Lake Waynewood the proportion of protein composing the seston (percentage protein by weight) varied from < 10% to > 40%. No statistically significant patterns in the percentage protein or carbohydrate were found. However, the proportion of seston comprised of triglyceride decreased with lake type and increased during the year; whereas the proportion of seston as polar lipid increased with lake type and decreased during the year. Triglyceride comprised most of the lipid. Both protein : lipid and protein : carbohydrate ratios tended to be greatest in summer and lowest in the spring and autumn. 6. Relationships between samples and biochemical composition analysed by Canonical Correspondence Analysis (Canoco) indicated similar patterns in seasonal changes in seston biochemistry for the three lakes, with samples separated primarily by vectors for lake type (oligotrophic to eutrophic) and the percentage polar lipid (proportion of total lipid) and secondarily by vectors for date and water depth (epilimnion or metalimnion). 7. These seasonal biochemical changes in the seston food base were compared with biochemical changes known to occur in algae grown under N-or P-limited conditions in the laboratory, and the resultant quality of this algal food for suspension-feeding consumers (zooplankton). It was concluded that zooplankton were likely to be physiologically challenged by these distinct seasonal shifts in the quality of lake seston.     

Metabolic dynamics across prolonged diapause development in larvae of the sawfly,Cephalcia chuxiongica (Hymenoptera: Pamphiliidae)

Nutrient metabolism is crucial for the survival of insects through the diapause. However, little is known about the metabolic mechanism of prolonged diapause. The sawfly, Cephalcia chuxiongica (Hymenoptera: Pamphiliidae), is a notorious defoliator of pine trees in southwest China. One of the distinguishing biological characteristics of this pest is the prolonged diapause of about 1.5 years. In this study, the body lipid, carbohydrate (total body sugar, glycogen, trehalose, and glucose), protein, and glycerol contents were measured in diapausing larvae of C. chuxiongica. The results showed that the changes of biochemical composition in C. chuxiongica are associated with the diapause initiation, maintenance, and termination phases. During the initiation phase, trehalose, glucose, and glycerol increased significantly, but glycogen decreased sharply. In general, the lipid, carbohydrate, and glycerol levels decreased gradually across the maintenance phase. At termination phase, the contents of glycogen and lipid persistently decreased, while an increase of trehalose, glucose, and glycerol contents were detected. The protein level was significantly higher at maintenance phase than at initiation and termination phases. It was also found that elevation of trehalose, glucose, and glycerol contents occurred in winter. These implies that the metabolites with altered levels in diapausing larvae of C. chuxiongica are responsible for maintaining a prolonged development and overwintering.     

Composition and energy density of eggs from two species of freshwater turtle with twofold ranges in egg size

Lipid, protein, ash, carbohydrate and water content and energy density of eggs were measured from different clutches over a range of egg size in two species of freshwater turtle. Dry egg contents consisted of protein (54-60%), lipid (25-31%) and ash (5-6%) while carbohydrate was found to be negligible (<1%). Albumen consisted principally of water ( approximately 98%), and the dry component was composed of protein (47-51%), ash (19-26%) and lipid (18-21%), but contributed only a small amount ( approximately 2%) to overall dry egg contents. Energy density of dry albumen (15-17 kJ/g) was significantly lower than for dry yolk (26-27 kJ/g). Yolk consisted of 62-70% water, and the dry component was composed of protein (54-61%), lipid (25-31%) and ash (5-6%). Fractional concentrations of water, lipid, protein and ash and energy density remained constant over the range of egg size in Emydura signata eggs. In contrast, an increase in the yolk to albumen ratio and a decrease in water content of yolk as egg size increased caused the composition and energy density of Chelodina expansa eggs to vary systematically with egg size.     

Energy source utilization by embryos and larvae of the muricid snail Chorus giganteus (Lesson, 1829)

The muricacean snail Chorus giganteus presents intracapsular development and the occurrence of nurse eggs that are ingested by the early encapsulated embryos indicate both that these snails develop through a lecitotrophic type of development and that reserves would be sufficient to support settlement and metamorphosis. In order to get more information about the use of energy resources, the dynamics of biochemical components throughout development at three temperatures (9, 12 and 15 °C) and the energetic cost of free-swimming life and metamorphosis are described. The uptake of ³H-alanine, as representative of dissolved organic matter, by embryo and larval stages is also investigated. While protein levels increased at all temperature conditions after ingestion of nurse eggs, lipids only increased when embryo and larvae were reared at 15 °C, and no change in carbohydrate levels was detected at any of the temperatures. The RNA/DNA indexes showed no significant differences with temperature at any stage of development but decreased along with the development of individuals. After hatching, organic matter and energy content of juveniles steadily decreased. Individuals at any of the developmental stage showed to be able to uptake alanine from seawater; the aminoacid uptake capacity increased along with intracapsular development. Uptake of alanine showed to be an active process and to follow Michaelis-Menten kinetics. This would be the first report about dissolved organic matter uptake by encapsulated development stages of any marine invertebrate species and let conclude that these larvae have the ability to obtain exogenous food in a dissolved form and to incorporate it into metabolizable compounds.     

Characterization of lipovitellin in eggs of the polychaete Neanthes arenaceodentata

The ooplasm of mature oocytes of the polychaete Neanthes arenaceodentata is characteristically filled with yolk platelets. A major component of these structures is lipovitellin, which provides energy and materials required by newly hatched larvae. The lipovitellin isolated and purified from the fertilized eggs of this polychaete was a high-density lipoprotein composed of protein (57%), lipid (42%) and carbohydrate (1%). The lipid component included phospholipids (92% of lipid), triacylglycerol (3% of lipid) and cholesterol (3% of lipid), while sodium dodecyl sulfate-gel electrophoresis showed the major protein component was a 120-kDa peptide. Microscopically, mature oocytes were present in the coelom along with phagocytic eleocytes. The presence of muscle fragments and oil droplets in eleocytes suggests that eleocytes play an important role in providing the protein and lipid needed for the assembly of lipovitellin in the oocytes.     

Studies in the biochemistry of cirripede eggs. V. Changes in the general biochemical composition during development of Chthamalus stellatus (Poli)

The biochemical composition of the eggs of Chthamulus stellatus (Poli) during their development has been investigated. The eggs are incubated within the mantle cavity of the adult but no substrates are contributed by the latter. Carbohydrates, protein, and lipid are all utilized. In contrast to two cold-water species, Balanus balanoides and B. balanus perviously investigated lipid rather than protein is consumed during the early stages. Possible explanations for this are considered.     

Biochemical changes during embryonic development in the aquatic hemipteran bug Laccotrephes griseus

Protein, carbohydrate, free amino acid, lipid, RNA levels, and electrophoretic changes in the protein profile were determined in the eggs of the water scorpion, Laccotrephes griseus, during normal embryonic development. The protein levels remain lower and relatively constant in the eggs of 0, 1 and 2 days of age, while in the eggs of older groups, i.e. between 2 and 6 days, a marked increase in the protein level occurs. Then its level declines. The RNA content shows a rise up to the day 6 stage, later it declines sharply, indicating an increase in the degree of synthetic activity that takes place during such period of embryonic development. Electrophoretic and densitometric analysis show the qualitative and quantitative changes of yolk protein reflecting the utilization of already existing proteins as well as the appearance of new proteins.Water content increases gradually as development proceeds. There is a steady depletion of carbohydrate and lipid during the course of embryonic development. The nature of yolk components as well as their preferential utilization during embryogenesis has been discussed in relation to the generally accepted view that protein serves as the source for the embryonic metabolism in aquatic insects does not hold good for L. griseus and other freshwater insects.     

The significance of diet in the growth and development of larvae of the blue crab,Callinectes sapidus rathbun,under laboratory conditions

The following protistan diets were tested on blue crab larvae: the algae Isochrisis galbana Parke, Monochrisis lutheri Droop, Dunaliella sp., and an unknown mixture; and the ciliated protozoans Euplotes vannus Muller and Parauronema virginianum(2/1) Thompson. None of these diets resulted in development past the first zoea stage, although some apparently were ingested and delayed mortality as compared to unfed controls.The rotifer Brachionus plicatilis Müller sustained good survival through early zoea development; however, rotifer-fed larvae did not metamorphose to the megalopa. Larvae of the polychaete Hydroides dianthus (Verrill) sustained crab larvae throughout zoea development, resulting in 17% survival to metamorphosis. The percentage mortality per stage was significantly lower in polychaete-fed larvae when compared with rotifer-fed larvae during zoea stages III, VI, and VII. Mean intermolt duration varied between diet treatments during the first three stages, but showed no differences during later zoea development. In tests on groups of late stage sibling larvae, Artemia salina L. nauplii gave development to metamorphosis, whereas rotifers did not.All the diets so far tested on blue crab larvae are classified according to their ability to sustain development. It is demonstrated that the two diets which allow completed development, Hydroides dianthus larvae and Artemia salina nauplii, contain 2–3 times as much lipid per dry weight as do rotifers. A metabolic requirement for lipid late in development may be indicated. Invertebrate larvae derived from yolky telolecithal and centrolecithal eggs may be an important dietary component for brachyuran larvae.