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.     

A study on the energy source in the developing embryo of the mangrove horseshoe crab,Carcinoscorpius rotundicauda (Latreille)

The mangrove horseshoe crab, Carcinoscorpius rotundicauda, is an Asian species found in Malaysia. This ancient arthropod has a long incubational period during which it depends on various energy sources for both embryogenesis and organogenesis. This study describes the trend of energy utilization from the endogenous reserves by the developing embryos from 0 to 40 days of incubation (until the hatching of the larvae). The dry weight, insoluble protein, carbohydrate, glycogen and lipid showed a declining trend from 0 to 40 days of incubation, whereas the wet weight, water content, ash content and soluble protein showed an increasing trend. Selected micro-elements such as Cu²⁺, Fe²⁺ and Zn²⁺ also demonstrated an interesting trend in the developing eggs when the egg mass was subjected to inductively coupled plasma mass spectrometry analysis, where these elements showed a high correlation with the moulting stages and egg development. Maximum variations within the micro-elements were observed during the 1st (10 days after fertilization) and 2nd (35–36 days after fertilization) moulting stages within the developing eggs. This study clearly indicated that the moulting cycles of C. rotundicauda during embryonic development influence energy utilization in the form of carbohydrates, lipids, proteins, glycogen and other micro-elements.     

Nutrient Composition of Romanomermis culicivorax in Relation to Egg Production and Metabolism

The nutrient composition of postparasitic females (newly emerged juveniles, newly molted adults, and spent adults) and eggs of Romanomermis culicivorax was studied. Throughout post-parasitic development, proteins increased and lipids decreased progressively as a proportion of the dry weight; the proportion of glycogen within the nematodes remained stable. The greatest decrease in the lipid moiety occurred during egg production. Eggs contained relatively low levels of lipids (12% dry weight), and ca. 20% of the dry weight of the eggs was unaccounted for by lipid, protein, and glycogen determinations. Chitin, mucoproteins, and peptides were present in the eggs. The fatty acid composition of nematodes remained constant during postparasitic development; eggs contained a similar profile of fatty acids as postparasites, with marginally higher content of unsaturated fatty acids. Radiotracer studies showed that the eggs could oxidize glucose and palmitic acid.     

Carbohydrate metabolism of eggs of the whitefish, Coregonus spp. during embryogenesis and its relationship with egg quality

The present study investigated the changes in carbohydrate metabolism of eggs of the whitefish, Coregonus spp. during embryogenesis (unfertilized eggs to embryos in the eyed stage). Occurrence of glycolysis was proved by activities of phosphofructokinase (PFK-1) and pyruvate kinase and by decreasing levels of hexose, pentose phosphate pathway by transaldolase (non-oxidative path) and glucose-6-phosphate dehydrogenase activities (oxidative path) and by increasing ribose levels, fructose synthesis (polyol pathway) by sorbitol dehydrogenase activities, gluconeogenesis by activities of glucose-6-phosphatase. Glycolysis and pentose phosphate pathway had highest activities up to the epiboly stage, gluconeogenesis from epiboly stage to the eyed embryo stage. Coregonus spp. eggs contained hexoses, ketoses, 6-deoxyhexoses, heptoses and uronic acids with hexoses, ketoses, and 6-deoxysugars occurring free and in bound form. Hexoses were found in highest quantities, followed by ketoses, and 6-deoxyhexoses. Levels of these compounds changed in a specific way during embryogenesis. During all investigated stages of embryogenesis, the levels of ribose, heptose, and ketose were correlated with the percentage of eyed stage embryos developing out of the fertilized eggs (egg viability). In distinct embryonic stages, the levels of hexoses and 6-deoxyhexoses and the activities of glucose-6-phosphatase were also correlated with egg quality. This ascertains the importance of carbohydrate metabolism for developing eggs.     

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.     

Structure and function of the hydropyle of the egg of the bug, Sphaerodema molestum

Changes in the wet weight, dry weight, and volume of the egg of Sphaerodema molestum during embryonic development have been studied. Also, experiments have been carried out to ascertain the route of entry of water from the environment into the egg.During development the eggs considerably increase their volume and wet weight while their dry weight progressively decreases. When the eggs of S. molestum are incubated in dye solutions, the latter penetrate through the chorionic hydropyle and reach the outer surface of the serosal hydropyle. This indicates that water enters in significant quantity through the chorionic and serosal hydropyles. The behaviour of 48-hr-old experimental eggs of S. molestum, in which the entry of water is blocked, further confirms that the intake of water is effected only through the hydropyles. The significance of the uptake of water in the eggs is discussed in relation to protein metabolism during embryogenesis.     

Utilisation of lipids, protein, ions and energy during embryonic development of Australian oviparous skinks in the genus Lampropholis.

The contents of eggs and neonates of the Australian skinks, Lampropholis guichenoti and L. delicata, are described and compared to allow interpretation of nutrient utilisation by the developing embryo. Even though the females are the same size, L. guichenoti lay smaller clutches of larger eggs (egg contents=41.6+/-1.2 mg dry mass) than L. delicata (26.6+/-2.8 mg). The energy density is the same for eggs (30.5+/-0.9 J/g ash-free dry mass for L. guichenoti and 29.9+/-1.1 J/mg for L. delicata) and neonates (22.5+/-1.3 J/mg for L. guichenoti and 23.5+/-0.4 J/mg for L. delicata) between species. The amount of nitrogen (protein) in neonates is only slightly lower than that in eggs, whereas there is a large and significant decline in total lipids. Thus, like some other skinks, protein is a source of metabolic energy during embryogenesis, although not as important as lipid. Triacylglycerol is the major lipid component of the eggs (80% of total lipid), with phospholipid forming only approximately 10% of the total lipid. The fatty acid profile of the phospholipid is distinguished by a high proportion of arachidonic acid (8%), a significant proportion of eicosapentaenoic acid (2-4%) and a relatively low proportion of docosahexaenoic acid (2-3%) compared to chickens. Eggs of both species have remarkably low concentrations of free cholesterol compared to other amniote eggs (0.7% for L. guichenoti and 1.3% for L. delicata). The loss of lipid during embryonic development is almost entirely due to the selective utilisation of yolk triacylglycerol, presumably for energy. By contrast, the amount of phospholipid recovered from the neonates was the same as that originally in the eggs. Moreover, significantly more total cholesterol was present in the neonates than in the eggs, suggesting that biosynthesis of additional cholesterol occurred during development. The phospholipids of the neonates contain higher proportions of arachidonic (11-12%) and docosahexaenoic (8%) acids than the phospholipids of the eggs. Eicosapentaenoic acid is less prevalent in phospholipids in neonates than in eggs. Neonates of both species contain significantly more calcium than the fresh egg contents (L. guichenoti, eggs 0.303+/-0.051 mg, neonates 0.641+/-0.047 mg; L. delicata, eggs 0.187+/-0.013 mg, neonates 0.435+/-0.033 mg), presumably as a result of resorption of calcium from the eggshell. Interestingly, there is also significantly more sodium in neonates than in the contents of fresh eggs (L. guichenoti, eggs 0.094+/-0.010 mg, neonates 0.184+/-0.011 mg; L. delicata, eggs 0.084+/-0.011 mg, neonates 0.151+/-0.010 mg). There is no significant difference in the content of potassium and magnesium in eggs and neonates of either species. Although the fresh eggs of L. delicata have a significantly higher sodium concentration than L. guichenoti, there is no difference in the concentrations of calcium, magnesium, potassium or sodium in the neonates of the two species.     

Repair of a genetically-caused defect in oogenesis in Drosophila melanogaster by transplantation of cytoplasm from wild-type eggs and by injection of pyrimidine nucleosides

Eggs produced by homozygous mutant rudimentary (r⁹, 154.5) females of Drosophila melanogaster die during embryogenesis, apparently because the mutant female fails to incorporate certain substances into the egg during oogenesis. These eggs can be rescued by injecting them at the preblastoderm stage with wild-type nuclei and cytoplasm or wild-type cytoplasm alone from unfertilized eggs. Some preblastoderm eggs injected with 1.5% of egg volume of cytoplasm from unfertilized wild-type eggs were able to complete both embryonic and postembryonic development and emerged as adults, whereas not a single uninjected control egg was able to complete embryonic development. The eggs of rudimentary mothers can also be rescued by injecting each egg at the blastoderm stage with 0.01 μg of pyrimidine nucleosides. The results demonstrate that a pyrimidine deficiency is the cause of abortive embryogenesis, and confirm the previous finding that the rudimentary mutation leads to pyrimidine auxotrophy.     

Chemical composition of the wound plug and entire plants for species of the coenocytic green alga, Caulerpa

Levels of ash, NaOH-soluble protein, lipid, and TCA-soluble carbohydrate were determined tor seven species of the green alga Caulerpa, for both the entire plant and wound plugs produced by cutting the rhizomes or blades. Insoluble carbohydrate was estimated by subtraction. Wound plugs had higher ash levels and a distinctly higher level of total carbohydrate. Both entire plants and wound plugs had low levels of lipid and protein. Carbohydrate is the major component of the wound plug in Caulerpa in contrast to protein reported for Bryopsis.     

Subcellular Metabolite and Lipid Analysis of Xenopus laevis Eggs by LAESI Mass Spectrometry

Xenopus laevis eggs are used as a biological model system for studying fertilization and early embryonic development in vertebrates. Most methods used for their molecular analysis require elaborate sample preparation including separate protocols for the water soluble and lipid components. In this study, laser ablation electrospray ionization (LAESI), an ambient ionization technique, was used for direct mass spectrometric analysis of X. laevis eggs and early stage embryos up to five cleavage cycles. Single unfertilized and fertilized eggs, their animal and vegetal poles, and embryos through the 32-cell stage were analyzed. Fifty two small metabolite ions, including glutathione, GABA and amino acids, as well as numerous lipids including 14 fatty acids, 13 lysophosphatidylcholines, 36 phosphatidylcholines and 29 triacylglycerols were putatively identified. Additionally, some proteins, for example thymosin β4 (Xen), were also detected. On the subcellular level, the lipid profiles were found to differ between the animal and vegetal poles of the eggs. Radial profiling revealed profound compositional differences between the jelly coat vitelline/plasma membrane and egg cytoplasm. Changes in the metabolic profile of the egg following fertilization, e.g., the decline of polyamine content with the development of the embryo were observed using LAESI-MS. This approach enables the exploration of metabolic and lipid changes during the early stages of embryogenesis.     

Analysis of protein,carbohydrate and lipid in rotifers

Protein, carbohydrate and lipid amounts were determined for several rotifer species collected directly from the field. Brachionus calyciflorus was the most abundant species; therefore making possible more data for it. An increase in protein content of this species occurred when its concentration in food (µg protein/ml) also increased. Keratella tropica showed a similar pattern, but Asplanchna brightwelli did not.Carbohydrate proved to be the main form of storage in rotifers. In Brachionus calyciflorus females bearing no egg, 8% of the total biomass was carbohydrate; in females bearing one egg, 15% carbohydrate was found. Lipid does not appear to be used for storage since no increase in the amount of lipid was detected in females bearing eggs or embryos. This suggests that lipid has a structural function. Finally, a relationship between rotifer body volume and protein content at a given food concentration was obtained. The cladoceran Daphnia magna follows the same pattern.     

STUDIES ON CELL METABOLISM AND CELL DIVISION : VI. OBSERVATIONS ON THE GLYCOGEN CONTENT,CARBOHYDRATE CONSUMPTION,LACTIC ACID PRODUCTION,AND AMMONIA PRODUCTION OF EGGS OF ARBACIA PUNCTULATA

1. Under the present conditions of experiment, Arbacia eggs were found to contain an average of 110 mg. of acid-hydrolyzable carbohydrate (calculated as glucose) per gm. of egg protein. This carbohydrate was almost all in the egg proper, little or none being found in the jelly. To permit conversion of the data to other bases of reference the relation of nitrogen content to wet and dry weight and to egg number were determined. The eggs were found to contain 23.9 per cent solids, 0.10 mg. nitrogen per mg. dry weight, and 5.93 mg. nitrogen per 10⁶ cells. From these results, about 7 per cent of the egg dry weight is acid-hydrolyzable carbohydrate and about 65 per cent is protein. 2. Approximately one-half of the total acid-hydrolyzable carbohydrate was isolated in the form of an alkali-stable, alcohol-precipitable carbohydrate. This substance gave a typical glycogen color test with iodine, yielded glucose on acid hydrolysis, and had, within the limits of experimental error, the same optical rotation as glycogen from other animal sources. Since known amounts of glycogen were completely recovered when carried through the isolation process, the nature of one-half of the acid-hydrolyzable carbohydrate of Arbacia eggs remains undetermined. 3. In order to gain some estimate of the extent to which Arbacia eggs utilize their total carbohydrate for development, determinations of the oxygen consumption, respiratory quotient, carbohydrate consumption, lactic acid production, and ammonia production were made. While all samples of eggs were found to utilize carbohydrate from the 15th to the 24th hours of development at 20°C., certain samples of eggs consumed little or no carbohydrate from the 1st to the 6th hours, the period during which cell division proceeds most rapidly. In a number of instances where carbohydrate breakdown was lacking, a substantial proportion of the oxygen consumption could be accounted for on the basis of processes involving oxidation of protein or protein breakdown products.     

Assessment of biochemical composition and energy reserves in larvae of the scallop Patinopecten yessoensis

Larvae of Patinopecten yessoensis increased in dry weight from ≈ 150 to 1000 ng per larva during the larval development period of 28 days. Microanalytical procedures were developed to determine the lipid, protein, carbohydrate, and ash contents from which energy levels and condition indices were derived. Replicate analyses of two sizes of P. yessoensis larvae gave coefficients of variation at or <5% for the biochemical analyses. Lipid and protein were identified as major components, and carbohydrate as a minor component providing 56.6,37.6, and 5.8 %, respectively, of the calculated energy content. The energy content of the eggs of P. yessoensis was 2.4 and 3.1 times higher than the larvae of P. yessoensis and Crassostrea gigas, respectively, derived from 20.6% lipid, 54.6% protein, and 7.2% carbohydrate. The carbohydrate in the eggs was stored principally as a glucan, considered to be glycogen, which was absent in the developing larvae. Changes in biochemical composition of P. yessoensis larvae during development showed that lipid and protein reserves were lost for ≈ 20 days and then lipid accumulated as the larvae reached premetamorphic condition.     

The biochemical and energetic composition of somatic body components of echinoderms from the northern Gulf of Mexico

• 1.1. The biochemical and energetic compositions of the somatic body components of seven species of asteroids, one ophiuroid, and four echinoids from the northern Gulf of Mexico (30–95 m depth) were ascertained.
• 2.2. Levels of ash were high (68.5–90.8% dry wt) in all body-wall tissues, with the exception of the asteroid Echinaster modestus (51.6% dry wt). Levels of ash were low in the pyloric cecae (nutrient storage organ) of asteroids (4.6–30.8% dry wt).
• 3.3. Levels of lipid (8.1–34.5% dry wt), soluble protein (15.9–28.7% dry wt), and insoluble protein (18.1–48.6%, dry wt) were high in the pyloric cecae of all asteroids, but generally low in ophiuroid and echinoid body-wall tissues. High protein levels (28.5–44.5% dry wt) in the body-wall of the asteroids Echinaster modestus and Anthenoides pierceisuggest it may play a role in nutrient storage.
• 4.4. All somatic tissues contained low levels of carbohydrate (0.2–1.4% dry wt).
• 5.5. Levels of energy in pyloric cecal tissues (12.99–26.05 kJ/g dry wt) were 4–8 times higher than in echinoderm body-wall tissues (2.92–11.91 kJ/g dry wt).
• 6.6. The biochemical and energetic compositions of echinoderms from the northern Gulf of Mexico are similar to those of species from other latitudes and depths.

     

Changes in the biochemical composition of Euphausia superba Dana embryos during early development

Summary The biochemical composition of developing Euphausia superba Dana embryos has been examined at three stages: fresh spawned, gastrula, and limb bud. Fresh spawn embryos had 31% lipid, 1.0% carbohydrate, and 57% protein on a gram dry weight basis. Throughout development lipids were utilized more slowly than in other crustacean embryos for a total utilization of 37.5%. Overall, 35.6% of the starting protein was utilized. On a weight basis, twice as much protein than lipid was used during development, and it appeared that, energetically, protein and lipid contributed equally to the energetics of the developing embryo. Carbohydrate was evidently a minor substrate in early development, although the level increased 38% during development. Average water content was 86% in fresh spawned embryos and 88% in the gastrula stage. The average dry weight of the embryos throughout development was 30 g. The features of planktonic embryos are contrasted with demersal embryos and the atypical metabolic pattern of krill embryos is discussed.MOA dedicates this paper to the memory of Dr. Mary Alice McWhinnie, for her encouragement during my years at DePaul University and for the opportunity to participate in her research     

Placental transfer of nutrients during gestation in the viviparous lizard, Pseudemoia spenceri

Energy, ionic, protein and lipid contents and fatty acid profiles for the major lipid classes of freshly ovulated eggs and neonates of the viviparous lizard, Pseudemoia spenceri, were measured. Litter size is 1.7 ± 0.1, with larger females producing larger neonates. Placentotrophy results in approximately 23% more dry matter in the neonates than in the fresh egg. The increase in the quantity of protein and lipid during development is not significant and is reflected in the similarity of energy densities of eggs and neonates. As a percentage of dry matter, neonates have slightly lower proportions of lipid and protein than eggs because of significant uptake of ash, calcium, potassium and sodium, but not of magnesium, across the placenta. The amounts of triacylglycerol and phospholipid are not significantly different between the egg and the neonate, but neonates contain significantly more cholesterol and cholesteryl ester. The amounts of the major fatty acids, palmitic and oleic acids, recovered from the total lipids of the neonate do not differ significantly from the amounts present in the egg lipids, but the neonates contain significantly less linoleic and α-linolenic acids and more palmitoleic, stearic and arachidonic acids than the eggs. The amount of docosahexaenoic acid recovered from the lipids of the neonate is 2.6-times greater than the amount initially present in the egg. P. spenceri has a relatively larger egg and a smaller reliance on placentotrophy than other species in the same genus, all of which have a similar placental morphology. Nevertheless, the pattern of embryonic nutrition includes both obligative and facultative placentotrophy. All the major components of yolk of oviparous species are present in eggs of P. spenceri, but most are augmented during development by placental transfer. Accepted: 8 April 1999     

Chemical allatectomy of late Locusta embryos by a synthetic precocene and its effect on hopper morphogenesis

The anti-allatin substance, 7-ethoxy-precocene II (= “precocene III”) was topically applied to eggs of Locusta migratoria migratorioides with fully grown embryos in stage XX (about 64 ± 4% of the whole period of egg development). A day after precocene application the eggs were washed for 10–15 s in acetone and then transferred to clean containers for removing precocene residues and for preventing contamination at hatching. The treatment induced prothetelic morphogenetic disturbances which became overt in the subsequent hoppers; the effect was dose dependent and the ED₅₀ (= effective anti-allatin dose 50%) was low, 20.5 μg precocene III per g fresh egg weight (= 0.37 μg per egg). Quite similar results were obtained following application of precocene III to eggs with embryos in stage XXI (73 ± 4% of the egg development). These findings and direct examination of histological sections of the embryonic corpora allata demonstrated that precocene chemically allatectomizes late Locusta embryos. The lethal effect of precocene III was dependent on the washing. When the eggs were washed in acetone a day after application, mortality did not occur in a dose-dependent way; even the highest dose applied, 256 μg precocene III per egg (= 14405 μg per g fresh weight), was less than the LD₅₀ (lethal dose 50%). In contrast, without washing mortality was dose dependent, but it occurred later, at or after hatching; the LD₅₀ was 1334.9 μg per g (= 22.7 μg/egg). The results show that the late embryos are highly susceptible to the anti-allatin effect of the precocene, but are extremely insusceptible to its lethal effect; toward hatching, however, susceptibility to the lethal effect becomes marked.With doses between 45–14405 μg precocene III per g fresh egg weight, the anti-allatin effect became overt by a quite-uniform belated morphogenetic response. All hoppers which hatched from precocenetreated eggs were morphogenetically normal in the 1st instar and in the beginning of the 2nd instar, but the duration of the 2nd instar was almost doubled and at the end of this instar over 96% of the locusts died in the moult, being unable to shed the exuvia. Artificial removal of the apolyzed old cuticle revealed 3rd instar prothetelic adultiforms. These results and some data in the literature indicate that allatectomy of the embryo does not result in prothetelic morphogenetic disturbances in the 1st and early 2nd instar larvae and may impose the question what is the role of the juvenile hormone in late embryos and early larvae.     

Microtubule proteins in axolotl eggs and developing embryos

Tubulin from eggs and embryos of the Mexican axolotl was characterized by electrophoresis and colchicine binding. In urea-polyacrylamide gel electrophoresis, soluble axolotl egg tubulin migrated as two bands, identical to tubulins from sea urchin sperm and Drosophila eggs. However, in SDS-containing gels, on which the α and β subunits of standard tubulins were well resolved, axolotl egg tubulin migrated as a single band with an apparent molecular weight of 53,500. The method of disruption of the eggs affected both yield of tubulin from vinblastine sulfate precipitates and stability of the colchicine binding activity. The colchicine binding activity of soluble tubulin from gently disrupted eggs was specific and of high affinity, with properties similar to those reported for other tubulins. The tubulin pool in unfertilized eggs was determined to be approximately 2 μg/egg; the level decreased 20% after initiation of cleavage and then remained constant through development to postneurula stages. The colchicine binding activity of soluble tubulin from embryos was much less stable than that of unfertilized eggs and decreased further during development. No differences were found in properties of tubulin from eggs of several strains of normally pigmented axolotls; however, tubulin from albino eggs showed slightly different properties in both electrophoresis and colchicine binding. The colchicine binding activity of soluble tubulin accounts for only half the total activity in axolotl eggs; they possess, in addition, a particulate nontubulin colchicine binding activity.     

Temporal variability in egg production rates of Acartia tonsa Dana in Long Island Sound

The relationship between week-by-week variations in the in situ egg production rates of Acartia tonsa Dana and changes in chlorophyll concentration in several size fractions was investigated by incubating adult females in natural sea water for 24-h periods. Our results indicate that the egg production of A. tonsa in Long Island Sound was better related to the 10 μm chlorophyll size fraction than to the total chlorophyll concentration. The < 10 μm size fraction comprised the greatest percentage of the chlorophyll during July and August when the water column was stratified. Egg production rates were lowest (8.7 eggs · female⁻¹ · day⁻¹) in early August when less than 0.5 μg chlorophyll 1 ⁻¹ was observed in the 10 μm chlorophyll a size fraction. Following destratification in late August, the “fall” diatom bloom occurred and egg production rates increased to the maximum observed rate of 56.6 eggs · female⁻¹ · day⁻¹. At this time, the concentration of the 10μm chlorophyll size fraction was 5.5 μg 1⁻¹. Maximum egg production rates were observed at chlorophyll concentrations as low as 0.8 μg 1⁻¹ in the 10 μm size fraction.     

Sex‐biased resource allocation in ovo in a sexually size‐dimorphic species

Sex‐biased resource allocation in eggs is increasingly recognized as one strategy oviparous mothers can employ to invest differentially in one sex, depending on nutritional requirements. Previous studies have used egg size as an index of nutrient allocation, but few have examined egg contents directly. We used molecular sexing of early‐stage ring‐billed gull Larus delawarensis embryos, a species with sexual size dimorphism, to test whether sex‐specific nutrient allocation occurs in ovo. Despite no sex difference in size, eggs with male embryos contained more albumen, while eggs with female embryos contained more yolk, lipid and non‐lipid (protein and carbohydrate). It is unclear why such sex‐biased resource allocation in ovo is utilized by ring‐billed gulls. However, our data indicate that a cursive examination of egg mass or size may not necessarily reflect nutrient allocation strategies mothers use in ovo, and that sex‐biased investment in ovo may be more widespread than currently appreciated.