Egg Lipid Content Research Articles

Lipid and fatty acid composition of Antarctic shrimp eggs (Decapoda: Caridea)

Eggs of the decapod shrimps, Chorismus antarcticus, Nematocarcinuslanceopes and Notocrangon antarcticus were taken to analyse their morphometric, lipid and fatty acid composition. Almost all females carried undifferentiated eggs (stage I). The average number of recently extruded eggs was lowest in C. antarcticus with 163 eggs, and highest in Nematocarcinus lanceopes with 1,220 eggs, while Notocrangon antarcticus produced on average 350 eggs. The lipid content (% of dry mass) of the eggs was 18.8% for C. antarcticus, 14.3% for Notocrangon antarcticus and 18.1% for Nematocarcinus lanceopes. Dominant lipid classes in eggs of all species were phospholipids and triacylglycerols. The storage lipid, triacylglycerol, was slightly elevated in the eggs of Nematocarcinus lanceopes (mean of 52.7%) compared to the other two species. The fatty acid compositions of the decapod eggs were similar in the three species. Dominant fatty acids were 20:5(n-3), 18:1(n-9), 16:1(n-7), 16:0 and 18:1(n-7), comprising 75.8–78.4% of total fatty acids. Among the species, the eggs of C. antarcticus had the highest proportions of polyunsaturated fatty acids (39.6%), dominated by 20:5(n-3), and the lowest percentage of monounsaturates (41.8%). The eggs of Nematocarcinuslanceopes and Notocrangonantarcticus contained almost the same proportion of polyunsaturated fatty acids (28.0% and 28.4%, respectively), whereas Nematocarcinus lanceopes had the highest amount of monounsaturates due to the dominance of 18:1(n-9). Based on our findings, we assume that eggs produced by polar decapod crustaceans do not contain substantially more lipids than related species from temperate or tropical regions. However, additional studies are necessary to substantiate any general conclusion about the relationship of egg lipid content and composition with climatic zones.

Differences in the biochemical content of buoyant and non-buoyant eggs of the Japanese eel, Anguilla japonica

Eggs of the Japanese eel, Anguilla japonica, were obtained by hormonally induced maturation and ovulation, and then categorized as buoyant and non-buoyant types in seawater after insemination. The water content of the buoyant eggs, 93.1%, was significantly higher than that of the non-buoyant eggs, 87.5%. Furthermore, the buoyant eggs had 1.5 times more free amino acids (FAA), 573.5 μmol/g dry weight (DW), than the non-buoyant eggs, 385.8 μmol/g DW, while no significant difference in egg lipid content or protein content was found. Compared to other pelagic eggs reported in the literature, the FAA content of the buoyant eggs was relatively low, although the water content was similar. These results suggest that there is a close relation between the quality of Japanese eel eggs obtained by typical hormonal inducement and the FAA content of the eggs, but the roles of FAA in the acquisition of egg buoyancy and fulfilling the early nutritional requirements are comparatively minor.

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 (∼98%), and the dry component was composed of protein (47–51%), ash (19–26%) and lipid (18–21%), but contributed only a small amount (∼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.

Differences in egg quality between wild striped trumpeter ( Latris lineata) and captive striped trumpeter that were fed different diets

This study assessed differences in egg quality between freshly caught striped trumpeter, Latris lineata, and captive striped trumpeter that were fed either chopped fish or commercial salmon pellets. Total lipid content of eggs did not differ between the three groups (average of 20% dry weight). The group fed chopped fish produced eggs with the greatest docosahexaenoic acid (DHA)/eicosapentaenoic acid (EPA) ratio (4:1) and, together with eggs collected from the wild group, contained the highest ratio of ( n−3)/( n−6) polyunsaturated fatty acids (PUFAs) (9:1 and 8:1, respectively). Ascorbic acid levels in eggs from the pellet-fed group (75 μg g −1 wet weight) were higher than eggs from the wild and chopped-fish groups (48 and 40 μg g −1 wet weight, respectively), but there was no difference in α-tocopherol content (average of 4.4 μg g −1 wet weight). The volume of eggs produced, fertilisation rate and length of the larvae at hatch did not differ, but the pellet-fed group produced eggs of greater diameter, which corresponded to a larger yolk volume, and higher hatching success than the wild group. Each group of broodstock produced viable eggs and yolk-sac larvae, but the relatively low DHA/EPA and ( n−3)/( n−6) ratios in the eggs from the pellet-fed fish suggest that this diet may be inferior, when compared to chopped fish, for sustained growth and survival.

SEA TURTLES AS BIOLOGICAL TRANSPORTERS OF NUTRIENTS AND ENERGY FROM MARINE TO TERRESTRIAL ECOSYSTEMS

Our study quantified the nutrients and energy introduced into the nesting beach at Melbourne Beach, Florida, from distant foraging grounds by loggerhead sea turtles, Caretta caretta. The fate of eggs deposited into 97 nests was determined by monitoring nests throughout incubation. The organic matter, energy, lipid, nitrogen, and phosphorus content of fresh eggs, eggs at successive stages of development, hatchlings, and hatching remains were determined. From these analyses, we estimated the flow of energy and nutrients introduced into the 14 305 nests (∼1.6 × 106 eggs) deposited in a 21-km stretch of Melbourne Beach in 1996. We quantified the amount of energy and nutrients incorporated into each of four pathways: ingested by nest predators; consumed by detritivores, decomposers, and plants; lost as metabolic heat or gases during embryological development and hatching; or returned to the ocean as hatchlings. Each nest introduced a mean of 688 g of organic matter, 18 724 kJ of energy, 151 g of lipids, 72 g of nitrogen, and 6.5 g of phosphorus into the beach. Twenty-five percent of the organic matter, 27% of the energy, 34% of the lipids, 29% of the nitrogen, and 39% of the phosphorus introduced into the nests returned to the ocean as hatchlings. Quantities of energy and nutrients transported by the turtles are comparable to quantities moved by other important biological transporters. Human activities have substantially altered the quantity of energy and nutrients transported, and the distribution of those nutrients on the beach. By introducing nutrients into beach ecosystems, sea turtles may help maintain stable dune systems that are critical to their reproductive success.

Egg-production dynamics, biochemical composition and hatching success of the subantarctic copepod Paraeuchaeta antarctica: laboratory studies

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 205:219-227 (2000) - doi:10.3354/meps205219 Egg-production dynamics, biochemical composition and hatching success of the subantarctic copepod Paraeuchaeta antarctica: laboratory studies F. Alonzo1,*, P. Mayzaud1, S. Razouls2 1Observatoire Océanologique, Océanographie Biochimique et Ecologie, LOBEPM, ESA-CNRS 7076, BP 28, 06230 Villefranche-sur-Mer, France 2Laboratoire Arago, Observatoire Océanologique, URA-CNRS 117, 66630 Banyuls Cedex, France *E-mail: alonzo@obs-vlfr.fr ABSTRACT: The reproductive time scale, protein, and lipid contents of eggs and egg hatching success of the predatory calanoid copepod Paraeuchaeta antarctica from the Kerguelen Archipelago was investigated during the winter peak of reproduction, using females in captivity. The mean time taken by females to produce egg sacs was 21.5 d after the appearance of developing eggs in the oviducts. On average, eggs hatched 23.7 d after deposition of the sac, at 2°C. After hatching, females took an average of 9.6 d to produce a second egg sac. These periods did not vary as a function of collection date (August and September) or time in captivity. Egg mortality within the sac averaged 8%, but strongly increased with increased time in captivity. Captivity also induced a strong decrease in maternal lipid and protein contents and in the number of eggs per sac. However, the lipid content of eggs remained constant and the protein content decreased with increasing brood size. This indicated that P. antarctica were limited by available protein rather than lipid. The biochemical composition of the eggs did not change in relation to development, although egg diameter varied from 381 µm at egg deposition to 448 µm after 15 d development. Some females were fed with small copepods. Prey clearance and effect of concentration of prey on the female protein content indicated that predatory feeding occurs during winter in P. antarctica from Kerguelen. The estimation of the fecundity of P. antarctica females led to a production of 175.2 eggs female-1 yr-1, 91% of which took place between July and December. From June to October, winter production of eggs relied equally on maternal reserves accumulated during the summer and on carnivorous feeding at low prey concentrations. KEY WORDS: Paraeuchaeta antarctica · Fecundity · Hatching success · Egg biochemical composition · Energy budget Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 205. Online publication date: October 19, 2000 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2000 Inter-Research.

Comparative energetics and life cycle of the opossum shrimp (Mysis relicta) in native and non‐native environments

Summary1. Life history, fecundity and energy ingestion were compared for non‐native Mysis relicta in Flathead Lake, Montana, and in Waterton Lake, Montana/Alberta, where the mysid is native.2. Based on estimates from stomach contents, M. relicta in Flathead Lake consumed three to four times more energy per hour while foraging than M. relicta from Waterton Lake. The primary prey of M. relicta in Flathead Lake was Daphnia thorata. Diaptomus sicilis was the primary prey for M. relicta in Waterton Lake.3. Mysis relicta in Flathead Lake had a 1‐year life history. It took 2 years for M. relicta in Waterton Lake to complete a generation. Mysis relicta from Flathead Lake produced significantly (P &lt; 0.05) more eggs per female (19.9 ± 4.7) compared to M. relicta in Waterton Lake (13.7 ± 3.6). The lipid content in eggs from M. relicta in Flathead Lake was also significantly (P &lt; 0.05) higher than eggs from M. relicta in Waterton Lake.4. In Flathead Lake, M. relicta is able effectively to exploit Daphnia thorata, consuming greater biomass than M. relicta in Waterton Lake. Mysis relicta efficiently assimilates the greater biomass, which reduces generation time, increases fecundity, and increases lipid reserves of offspring. These results provide evidence of energetic mechanisms that enable M. relicta to colonize and affect foodwebs when introduced into lakes.

The Effect of Different Ratios of n-6/n-3 Fatty Acids in Broodstock Diets on Egg Quality of Catfish, Clarias batrachus

This experiment was conducted to acquire biochemical information on the quality of catfish eggs in relation to different n-6/n-3 ratios of fatty acids in the broodstock diet. Five experimental diets, which were isonitrogenous and isoenergy, but containing different levels of n-G and n-3 fatty acids (diet A: essential fatty acid (EF A)-deficient diet containing 0.21%n-6 fatty acid, 0.03% n-3 fatty acid; diet B: 0.67%, 2.09%; diet C: 2.24%,0.07%; diet D: 1.85%, 0.56%; and diet E: 0.26%, 1.68%) were used in the experiment. Five-month-old fish were fed the experimental diets for 10 months. Samples of the eggs produced by the respective broodstock were fertilized by the sperms. Samples of eggs during embryogenesis were analyzed for total lipid (TL), polar lipid (PL) and nonpolar lipid (NL) content as well as fatty acid (FA) composition. The hatching rate of the eggs and the percentage of abnormal larvae were determined. Results showed that the lipid content of the eggs decreased from the first hour after fertilization. The lipid content of the EF A-deficient eggs (diet A) and the n-3 fatty acid deficient eggs (diet C) decreased significantly during embryogenesis compared to the lipid content of the eggs from the other diets. Also, in general, the NL of eggs was much lower than PL during embryogenesis. The NL of diet A and diet C eggs was also much lower during embryogenesis compared to the NL of the eggs from the other diets. The n-6 and n-3 fatty acid levels of unfertilized eggs were influenced by the fatty acid level in the broodstock diet. The n-6 and n-3 fatty acids of NL were much lower than those of PL, especially in the organogenesis stage of the larvae. The n-6 and n-3 fatty acids of NL from diets A, B and C were also much lower compared to those of diets D and E. Hatching rates of eggs produced by the broodstock fed diets and D and E were also higher than those fed diets A, B and C.

Comparison of phospholipid and fatty acid composition of wild and cultured striped bass eggs

The dominant fatty acids in all neutral lipid fractions of non‐water hardened eggs from two wild and one cultured stock of striped bass Morone saxatilis were the monoenes, 18 : 1n9/n7&gt;16 : 1n7&gt;17 : 1. The dominant fatty acids in the phospholipid fraction of all eggs, regardless of origin, were 22 : 6n3&gt;18 : 1n9/n7&gt;20 : 5n3&gt;16 : 1n7&gt;16 : 0&gt;18 : 0. Arachadonic acid (AA, 20 : 4n6) was significantly lower (2·0%) in cultured fish eggs compared to either wild stock (5·8–6·1%). Fatty acids from the liver and eggs of wild Shubenacadie fish were similar to one another with respect to both neutral and phospholipid fractions. However, the AA and eicosapentaenoic acid (EPA, 20 : 5n3) content of the phospholipid fraction varied according to the hypothesized migration behaviour of Shubenacadie fish. The total lipid content of wild fish eggs was significantly greater than that of cultured fish. The total phospholipid content of Shubenacadie eggs was significantly higher than either Roanoke or cultured fish eggs. Phosphotidylinositol (PI) was the dominant phospholipid found ins all egg samples from all origins as opposed to phosphotidylcholine, which is usually the dominant phospholipid. These data indicate that PI and AA may have important and as yet unidentified roles in fertilization and embryonic development in these fish.

Egg Components and Hatchling Lipid Reserves: Parental Investment in Kinosternid Turtles from the Southeastern United States

We measured egg components and pre-ovulatory parental investment in kinosternid turtles ( Kinosternon baurii, Kinosternon subrubrum, Sternotherus minor, and Sternotherus odoratus) from the southeastern USA. Allocation patterns were determined by comparing lipid content of eggs and hatchlings, to determine whether females of species with hatchlings that exhibit a delayed nest-emergence strategy: (1) allocate higher proportions of energy storage lipids to eggs, (2) produce hatchlings with higher levels of storage lipids, and (3) have higher levels of pre-ovulatory parental investment in comparison to species whose hatchlings exhibit immediate emergence. Whereas total non-polar lipid (NPL) proportions by dry mass of eggs varied significantly among species, NPL proportions of hatchlings were not significantly different. Pre-ovulatory parental investment in care (proportion of hatchling NPL to egg NPL) was 40, 50, and 55% for K. subrubrum, S. minor, and S. odoratus, respectively. Lipid class composition of eggs and hatchlings was studied to distinguish lipids allocated for energy storage from those allocated to other functions. For both eggs and hatchlings, individual lipid classes (triacylglycerol, triacylglycerol fatty acid, cholesterol, cholesterol ester, and phospholipid) as proportions of total lipid, were similar among species. The major lipid class component of eggs and hatchlings of all species was triacylglycerol (>83%), an energy storage lipid. Substantial changes in lipid classes during embryogenesis were similar among species and included: (1) depletion of triacylglycerol, (2) increase in cholesterol esters, and (3) changes in phospholipid composition. Incubation time varied significantly among species, and appeared to be responsible for differential energy utilization during embryogenesis. Our results are inconsistent with the previously observed pattern that hatchlings exhibiting a delayed nest-emergence strategy are allocated higher proportions of energy storage lipids than those that exhibit immediate emergence. However, because the species that overwinters in the nest ( K. subrubrum) hatches approximately 40 days later than the species that typically does not ( S. odoratus), hatchling K. subrubrum may contain higher non-polar lipid proportions than hatchling S. odoratus during similar winter time periods. Kinosternid hatchlings contain enough stored lipids to support basal maintenance costs for substantial time periods. We suggest that such reserves may be critical to hatchling survival during a period of negative energy balance, regardless of nest emergence strategy.

Changes in lipid class and fatty acid composition during development in pike (Esox lucius L) eggs and larvae

To establish the changes which occur during embryogenesis and early larval development, eggs, yolk sac larvae and swim-up larvae of pike were examined for lipid class and fatty acid composition. At a water temperature of 15.5°C, the embryonic phase was short (6 days) and characterized by a 41.3% decline in the lipid content of eggs, accompanied by large reductions in the amount of phosphatidylcholine (41.4% decrease), sterol esters and triacylglycerols (respectively a 41.2% decrease and a 58.1% decrease), but not phosphatidylethanolamine which increased markedly (35.6%). By the time of yolk sac absorption (7 to 11 days after fertilization) the larvae remained inactive and a limited utilization of lipids was observed. Yolk sac phosphatidylcholine was selectively incorporated into larval bodies while the levels of other lipid classes remained unchanged in the yolk. When the swim bladder was filled and the swimming stage was reached (11 days to 13 days af), the yolk was completely depleted and yolk phosphatidylcholine together with yolk triacylglycerols were catabolised. Yolk phosphatidylethanolamine and yolk sterol esters were partly incorporated into the body lipids. In the subsequent swim-up larval stage (13 to 15 days af), a steady decrease in lipids was observed (41.6%). Fluctuations in the levels of polyunsaturated fatty acids, monounsaturated fatty acids or saturated fatty acids examined from eggs or larvae were consistent with changes in lipid classes during pike development. During yolk sac absorption, pike incorporated yolk PUFA released on hydrolysis of phosphatidylcholine into the larval body. The results are discussed with reference to water temperature and in relation to the ontogenic and ecological context of pike development.

Trade-Offs in Body Weights, Egg Loads, and Fat Reserves of Field-Collected Podisus maculiventris (Heteroptera: Pentatomidae)

The spined soldier bug, Podisus maculiventris (Say), was collected in 8 field sites in Indiana during the summers of 1987-1989. The insects were collected using both pheromone traps and sweep nets. Insect weights were recorded for all 3 yrs, and egg loads and lipid content in the fat body were recorded for 1988 and 1989. Analysis of the weights revealed that females were heavier than males. Female body weight, egg load, and lipid content were compared against corresponding measurements of predators subjected to different prey regimens in the laboratory. These comparisons indicate that field populations often had measurements similar to predators provided 1 prey item every 3-9 d. Predators collected during the summer of 1988 revealed higher mean lipid content, smaller egg loads, and lower weights than those collected in 1989. These traits, together with the relative scarcity of predators found in 1988, suggest that the predators were responding to greater food stress by conserving energy reserves in the fat body and diverting them away from reproduction. We discuss possible implications of these observations.

Maximizing lobster, Homarus gammarus (L.), egg and larval viability

The viability of batches of larvae reared to produce lobsters, Homarus gammarus (L.), for stock-supplementation experiments varied widely and rendered the timing and numbers of juveniles available for release unpredictable. Egg lipid reserves, time of hatching, exposure to low salinity during incubation and the influence of feeding regimes on water quality during larval culture were among the factors judged most likely to have affected viability. There was considerable variation in the lipid content of eggs from different females captured in 1989 and 1990. The proportion of lipid in eggs from females caught in 1990 was higher (10-20%) than that in eggs from females caught in 1989 (6-11%). The fatty acid content of eggs declined 72-80% during development although the overall proportions of fatty acids remained similar. Analysis of eggs and larvae from a single brood showed that rapidly developing eggs and the larvae that hatched from them contained greater triacylglyceride lipid reserves (by 49% and 15% respectively) than those which developed more slowly and hatched later. Exposure to reduced salinity (below 29 psu) prolonged development (by 30%), increased losses (to > 50%) and reduced the ratio of n-3:n-6 fatty acids (from 35-48 to 18-29) of eggs being incubated by captive, wild-caught, female lobsters. Larvae hatching from eggs held in reduced salinity (23 psu) survived less well (3% compared with 15%) than those incubated in sea water of 29 psu. The rate and degree to which fouling organisms became attached to larvae was related to feeding regime but not to development rate. A diet of mysids supplemented with mussel produced most fouling, generally poorer growth and a higher incidence of moulting abnormalities than a diet of mysids supplemented with Artemia nauplii. Among larvae fed Artemia, those developing early were significantly larger at instar 4 than late developers (56.4 mg cf. 49.8 mg, P < 0.05), but such differences in weight were not maintained by juveniles during the following 31 days of culture. The ecological and aquacultural implications of the results are discussed.

Development and Effect of Female Size on Egg and Juvenile Production in the Neogastropod Buccinum cyaneum from the Saguenay Fjord

The size at sexual maturity, the developmental timing and biology, and the biochemical (protein, glycogen, and lipid) content of eggs and juveniles were determined in two female size groups of the buccinid Buccinum cyaneum. Males reach sexual maturity at a smaller size (27 mm in shell length) than females (37 mm). A total of 33 females spawned in the laboratory starting in November 1991. The egg capsules were concave, measured 6.3 mm in diameter, and contained between 300 and 1000 eggs measuring 240 μm in diameter. Between 1 and 10 embryos developed. The others underwent chromatin degeneration within 3–4 wk and became nurse eggs. Between 1 and 10 crawling juveniles emerged 9 mo later in July and August and measured 2.5 ± 0.3 mm in shell length. The number of eggs and developing embryos within egg capsules increased with the size of the female. However, the quality of the juvenile at hatching, both in size and in biochemical content, did not vary significantly with female size.

Lipid, carbohydrate and nitrogen content of long- and short-winged Gryllus firmus: Implications for the physiological cost of flight capability

Concentrations of total lipid, triglyceride, soluble carbohydrate, total nitrogen and water were measured in the long-winged (LW) and short-winged (SW) morphs of the cricket, Gryllus firmus. In addition, the weights and composition of wings and oviposited eggs were compared between morphs. This was done to obtain information on the energetic cost of flight capability in the LW morph. Whole-cricket content (% dry mass) of triglyceride was significantly higher in LW vs SW individuals of both sexes. Since triglyceride is a likely flight fuel in G. firmus, the biosynthesis of elevated levels of this high energy substance in the LW morph may represent an important energetic cost of flight capability. The existence of such a cost is consistent with the elevated respiratory metabolism previously observed in LW vs SW G. firmus. A highly significant negative correlation was observed between triglycerides and non-triglycerides in LW but not SW crickets. This suggests that lipid biosynthesis may be operating under some constraint in the LW morph. Increased triglyceride biosynthesis may require a concomitant decreased biosynthesis of non-triglycerides. In contrast to the elevated triglyceride level in the LW morph, carbohydrate concentration was higher in the SW morph during early adulthood. Carbohydrate content also decreased with age in the SW but not in the LW adults. No differences were observed between morphs in (1) the total nitrogen or water contents of whole crickets, (2) the nitrogen content of wings or (3) the wet weight, dry weight, lipid content, or total nitrogen content of oviposited eggs.

Egg production and lipid content of Calanus glacialis in spring: indication of a food-dependent and food-independent reproductive mode

Female Calanus glacialis were collected in early May 1989 in the pack ice region of the western Barents Sea and were fed or starved over 11 wk. Both groups laid eggs continuously during this period, however, fed females laid up to six times more eggs. During the first 10 d after collection, both groups spawned at low rates. There-after, fed females strongly increased spawning rates and maintained high egg production levels over 11 wk, while the rates of starved females decreased. During starvation they lost 70% body carbon, 50% body nitrogen and 70% lipids. The wax ester portion decreased from 86 to ca. 60% of total lipids. Three phases of gonad development and lipid metabolism were distinguished: early gonad development; gonad maturation with a rapid decrease in lipids, especially wax esters; and spawning under fed and starved conditions, where in fed females food provided most of the energy, whereas in starved females the lipid content strongly decreased.

Lipids in eggs from first-time and repeat spawning Atlantic halibut, Hippoglossus hippoglossus (L.)

The production of viable larvae is critical to any aquaculture venture. Since lipids are important components of fish eggs, the amount and nature of the lipid may be crucial to the survival of the larvae. In this study the lipid content of unfertilized eggs from first-time and repeat spawning Atlantic halibut females was compared. The egg lipid content for the first-time spawner ranged from 0·18 to 0·41mg/egg; the range for the repeat spawner was 0·27 to 0·38mg/egg. However, the mean total lipid per egg values were similar for both fish at ca. 0·31mg/egg. The repeat spawner prodticed more eggs than the first-time spawner, thus allocating more lipid to egg production. In the eggs from the two fish 62–84% of the lipids was phospholipid.

Effects of egg composition and prey density on the larval growth and survival of lake whitefish (Coregonus clupeaformis Mitchill)

Eggs were collected from two stocks of lake whitefish, Coregonus clupeaformis, in Lakes Michigan and Huron to assess the effect of egg composition and prey density on larval growth and survival. Egg composition parameters including wet weight (mg egg−1), dry weight (mg egg−1), percent water, total caloric content (cal egg−1), caloric density (cal egg−1), percent lipid content, and total lipidcontent (mg egg−1) were measured. Fish hatched from six parental females in each stock were fed one of four rations (0, 18, 24, 50 brine shrimp larva−1 day−1) after yolk sac absorption. Length at hatch, endogenous growth, exogenous growth, and survival were measured during a 42‐day laboratory experiment. Length at hatch of larvae was positively related to egg caloric content (r2=0.780). Endogenous growth for lake whitefish larvae was positively related to percent lipid content (r2=0.896) and total egg lipid content (r2=0.876) of parental females. Exogenous growth and survival of larval lake whitefish was positively related to prey availability. Larval fish growth was accurately modelled (r2=0.973) as a function of prey abundance using a threshold‐corrected hyperbolic equation. These results indicate that both egg composition and prey availability have the potential to influence the growth and survival dynamics of larval lake whitefish significantly.

Acute temperature and oxygen stress among genotypes of Daphnia pulex and Simocephalus vetulus (Cladocera, Daphniidae) in relation to environmental conditions

The interactions among the genetics, physiology, and ecology of Daphnia pulex and Simocephalus vetulus inhabiting an ephemeral pond were studied. Electrophoretic analysis of four loci revealed high genetic diversity and genotypic coexistence within each species. In a total of 227 D. pulex individuals, 92 unique genotypes were found, and for 112 S. vetulus individuals, there were 18 unique genotypes. Daphnis pulex inhabited the pond early in the summer, but later there was a shift to S. vetulus as the primary cladoceran inhabitant. Biweekly sampling through the open water period allowed us to monitor environmental parameters such as water temperature and oxygen saturation, as well as the condition of the animals under study by assessing egg number, lipid content and ovary development, carapace length, and haemoglobin content. In laboratory experiments, S. vetulus was found to be more tolerant of both high temperature and low oxygen saturation than D. pulex. In addition to these interspecific tolerance differences, there were genotypic differences within each species in temperature tolerance. We have related these laboratory-determined genetic and physiological differences within and between species to the temporal variation in environmental conditions experienced directly in the pond. Thus, the rapid changes in pond conditions appear to play a large role in determining the species and genotypes able to exist in such an unpredictable environment.

Population differences in egg quality of Arbacia lixula (Echinodermata: Echinoidea): proximate composition of eggs and larval development

Differences in egg quality within and between populations of Arbacia lixula were investigated in the laboratory. Individuals from Cap Ferrat, Mediterranean, France, produced eggs with a higher protein and lipid contt than individuals from Villefranche, Mediterranean, France. This led to faster growth and development and greater survival in larvae from individuals from Cap Ferrat. The low protein and lipid content of eggs from individuals from Villefranche compared to those from Cap Ferrat. may have bn due to differences in the abundance of different algal species in the two localities and consequently the diet of sea urchins.