Fatty acid variations in symbiotic dinoflagellates from Okinawan corals

The fatty acid composition of polar lipids and triacylglycerols was determined in different morphophysiological types of symbiotic dinoflagellates (SD) isolated from the hydrocoral Millepora intricata and the scleractinian corals Pocillopora damicornis, Seriatopora caliendrum, Seriatopora hystrix and Stylophora pistillata from a fringing reef of Sesoko Island, Okinawa, Japan. The distribution of the fatty acids among the morphophysiologically distinct types of SD reported in these corals makes it possible to readily distinguish one type of SD from the other. Moreover, differences were found both in polar lipids and triacylglycerols. The polar lipids of SD from M. intricata showed a very distinctive fatty acid profile. A combination of large proportions of 18:4 (n-3), 18:5 (n-3), 22:5 (n-6), and 22:6 (n-3) and negligible amounts of 20:4 (n-6), and 20:5 (n-3) in SD from M. intricata was particularly noteworthy. The fatty acid profiles of SD from P. damicornis and SD isolated from S. caliendrum and S. hystrix differed in the proportion of 18:4 (n-3) and 22:6 (n-3). It is suggested that fatty acids might provide useful information on possible taxonomic differences among symbiotic dinoflagellates. It is assumed that biochemical differences can reflect the genetic diversity of the morphophysiological types of SD associated with several species of hermatypic corals from this region.     

Changes in the fatty acid composition of symbiotic dinoflagellates from the hermatypic coral <Emphasis Type="Italic">Echinopora lamellosa</Emphasis> during adaptation to the irradiance level

The composition of fatty acids (FAs) of symbiotic dinoflagellates isolated from the hermatypic coral Echinoporal lamellosa adapted to the irradiance of 95, 30, 8, and 2% PAR was studied. Polar lipids and triacylglycerols (TAG) differed between them in FA composition. Polar lipids were enriched in unsaturated FAs, whereas TAG, in saturated FAs. Light exerted a substantial influence on the FA composition in both polar lipids and TAG. The elevation of irradiance resulted in the accumulation of 16:0 acid in both lipid groups and 16:1(n-7) acid in TAG. It seems likely that de novo synthesis of 16:0 acid occurred actively in the cells of symbiotic dinoflagellates in high light. Since these processes are energy-consuming ones, they utilize excessive energy. When light intensity declined, 18:4(n-3) and 20:5(n-3) acids accumulated in polar lipids, which was accompanied by the increase in the content of chlorophyll a in the cells of zooxanthellae, whereas the levels of 22:6(n-3) and 20:4(n-6) acids reduced. Although the relative content of particular FAs varied substantially in dependence of irradiance, the balance between the sum of saturated and unsaturated FAs changed insignificantly. We concluded that the role of photoadaptation could not be limited only to changes in the degree of lipid unsaturation and membrane fluidity. It is supposed that light-induced changes in the FA composition reflect the interrelation between photosynthesis and FA biosynthesis.     

Mono- and digalactosyldiacylglycerol composition of dinoflagellates. III. Four cold-adapted,peridinin-containing taxa and the presence of trigalactosyldiacylglycerol as an additional glycolipid

Despite their importance in marine and freshwater microalgal assemblages, cold-adapted dinoflagellates have been the subject of few comprehensive lipid studies, particularly with respect to those lipids that comprise plastid membranes. In an effort to understand the differences between warm- and cold-adapted dinoflagellate glycolipid composition, four peridinin-containing, cold-adapted dinoflagellates were surveyed for intact forms of monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG), two common plastid lipids, using positive-ion electrospray ionization/mass spectrometry (ESI/MS) and electrospray ionization/mass spectrometry/mass spectrometry (ESI/MS/MS). It was determined that the dominant forms of MGDG and DGDG in these cold-adapted, peridinin-containing dinoflagellates possessed C₁₈ fatty acids and did not, with the exception of a 20:5/18:5 form of DGDG in a cold-adapted Gymnodinium sp. from the Baltic Sea, have C₂₀ fatty acids. This finding is in contrast to an earlier study of 35 peridinin-containing, warm-adapted dinoflagellates, which discovered a cluster dominated by C₁₈ fatty acids and a cluster dominated by both C₂₀ and C₁₈ fatty acids. The key difference in MGDG and DGDG production between the former group and the cold-adapted dinoflagellates examined in this study is that the cold-adapted species’ DGDG fatty acids were less saturated. Each cold-adapted dinoflagellate possessed both 18:5/18:5 and 18:5/18:4 DGDG, while most of the warm-adapted dinoflagellates contained only 18:5/18:4 DGDG. This survey also revealed the presence of a putative 18:1/14:0 trigalactosyldiacylglycerol (TGDG) as a dominant glycolipid in Gymnodinium sp. TGDG, previously unreported in dinoflagellates, was also discovered in Gymnodinium sp. in the forms of 18:1/16:0 and 18:1/18:1 TGDG, as minor lipids. Since the fatty acids associated with TGDG are not those found with dominant forms of MGDG or DGDG, TGDG may be produced by a different biosynthetic pathway.     

Lipid Composition of the Arthrospores, Yeastlike Cells, and Mycelium of the Fungus Mucor hiemalis

The fungus Mucor hiemalisF-1156, which is believed to be monomorphic, was found to be able to grow dimorphically in a liquid medium that is free of chemical agents influencing morphogenesis. The growing mycelium produced arthrospores in large amounts. The lipids of the mycelium, yeastlike budding cells, and arthrospores differed in the contents of saturated and unsaturated fatty acids and in the proportion of polar and neutral lipids. The arthrospores contained more monoenoic fatty acids in the total lipids, more triacylglycerides and sterol esters in the neutral lipids, and more phosphatidylcholine and phosphatidylethanolamine in the polar lipids than the yeastlike cells. These differences in the lipid composition of different types of fungal cells should be taken into account in the studies of the lipogenesis of M. hiemalis.     

Fatty‐Acid Profile of Total and Polar Lipids in Cultured Rainbow Trout (Oncorhynchus mykiss) Raised in Freshwater and Seawater (Croatia) Determined by Transmethylation Method

Fatty acids from total lipids and polar lipids in cultured rainbow trout (Oncorhynchus mykiss) raised in seawater (SW) and freshwater (FW) were identified and quantified from the muscle samples in January, April, and July. The highest total lipid and polar lipid amounts were found in April. July contents of total lipids were low, but percent of the polyunsaturated fatty acids (PUFAs) was high in SW and FW environment (particularly n‐3 PUFAs). Variety of 17 fatty acids was identified by GC‐FID after transmethylation. The predominant fatty acids in rainbow trout from SW and FW were: docosahexaenoic acid among n‐3 PUFAs, palmitic acid among saturated fatty acids (SFAs), and oleic acid among monounsaturated fatty acids (MUFAs). Appreciably higher n‐3/n‐6 ratio was found in total lipids in April (6.40, FW fish) and in polar lipids in July (18.76; SW fish). High n‐3/n‐6 ratio in total lipids and polar lipids of rainbow trout from SW and FW, besides beneficial n‐3/n‐6 ratio in the commercial fish food, could be characteristic for the local environmental conditions (Croatia).     

Comparison of fatty acid contents and composition in major lipid classes of larvae and adults of mosquitoes (Diptera: Culicidae) from a steppe region

Emerging aquatic insects, including mosquitoes, are known to transfer to terrestrial ecosystems specific essential biochemicals, such as polyunsaturated fatty acids (PUFA). We studied fatty acid (FA) composition and contents of dominant mosquito populations (Diptera: Culicidae), that is, Anopheles messeae, Ochlerotatus caspius, Oc. flavescens, Oc. euedes, Oc. subdiversus, Oc. cataphylla, and Aedes cinereus, inhabited a steppe wetland of a temperate climate zone to fill up the gap in their lipid knowledge. The polar lipid and triacylglycerol fractions of larvae and adults were compared. In most studied mosquito species, we first found and identified a number of short‐chain PUFA, for example, prominent 14:2n‐6 and 14:3n‐3, which were not earlier documented in living organisms. These PUFA, although occurred in low levels in adult mosquitoes, can be potentially used as markers of mosquito biomass in terrestrial food webs. We hypothesize that these acids might be synthesized (or retroconverted) by the mosquitoes. Using FA trophic markers accumulated in triacylglycerols, trophic relations of the mosquitoes were accessed. The larval diet comprised green algae, cryptophytes, and dinoflagellates and provided the mosquitoes with essential n‐3 PUFA, linolenic, and eicosapentaenoic acids. As a result, both larvae and adults of the studied mosquitoes had comparatively high content of the essential PUFA. Comparison of FA proportions in polar lipids versus storage lipids shown that during mosquito metamorphosis transfer of essential eicosapentaenoic and arachidonic acids from the reserve in storage lipids of larvae to functional polar lipids in adults occurred.     

Comparative Characterization of the Microbial Community in Two Species of Sponges from Sea of Japan Using Fatty Acid Markers

The fatty acid composition of total lipids in two species of sponges (Halichondria panicea and Clathria pennata) inhabiting the same biotope in the Sea of Japan was examined. More than 80 fatty acids (FAs) were found for each species of sponges. Of them, 61 fatty acids were identified for H. panicea and 54 for C. pennata. The relative content of most FAs was less than 1%. The contribution of symbiotic microorganisms to the total fatty acids was higher in H. panicea than in C. pennata. Bacterial symbionts and microeukaryotes were found among the microorganisms associated with the sponges. The contribution of prokaryotic organisms was equal (7.8%) for both species of sponges, but the fatty acids were characteristic of different taxonomic groups of bacteria. The proportion of microeukaryotic fatty acids in the total lipids of H. panicea (19.6%) was two times that of C. pennata (10.1%).     

Lipids and fatty acids of two pelagic cottoid fishes (Comephorus spp) endemic to Lake Baikal

Matured females of two Lake Baikal endemic fish species, Comephorus baicalensis and Comephorus dybowski, have been investigated for lipid of the whole body and specific tissues (liver, muscles, ovaries), phospholipid classes and fatty acids of neutral and polar lipids. Total lipid in the body (38.9% fresh weight), liver (23.5%) and muscles (14.5%) of C. baicalensis were greater than those of C. dybowski (4.7, 8.7 and 2.6%, respectively); only their ovaries were similar (5.3 and 5.6% lipid, respectively). In both species, phosphatidylcholine and phosphatidylethanolamine were the major phospholipids, ranging from 60.7 to 75.1% of total phospholipid and 14.5–25.7%, respectively. In most cases, monounsaturated fatty acids (MUFA) were the major fatty acid group in C. baicalensis, whereas polyunsaturated fatty acids (PUFA) were the major group in C. dybowski. The MUFA 18:1(n-9) prevailed over other fatty acids in C. baicalensis and varied from 19% in polar lipids of muscles to 56.1% in neutral lipids of muscles. In polar lipid of C. dybowski, the PUFA 22:6(n-3) prevailed over other fatty acids in muscles and ovaries, while 16:0 dominated polar liver lipids and neutral lipids of all tissues. Other major fatty acids included 16:1(n-7), 18:1(n-7), and 20:5(n-3). Values of the (n-3)/(n-6) fatty acid ratio for neutral lipids of C. baicalensis (0.5–0.9) are well below the range of values characteristic either for marine or freshwater fish, while these values for polar lipids (1.6–1.8) are in the range typical of freshwater fish. Neutral lipid fatty acid ratios in C. dybowski (2.5–3.1) allow it to be assigned to freshwater fish, but polar lipids (2.8–3.7) leave it intermediary between freshwater and marine fish.     

Betaine lipids of Symbiodiniaceae hosted by Indo-Pacific corals

The total pool of coral lipids consists of lipids produced by both the coral host and its symbiotic dinoflagellates of the family Symbiodiniaceae. Betaine lipids (BL) are characteristic of plasma membranes of microalgae. Composition of such BL as 1,2-diacylglyceryl-3-O-carboxy-(hydroxymethyl)-choline (DGCC) that occur in coral symbionts may depend on either Symbiodiniaceae species or coral species. Membrane-forming lipids DGCC have a zwitterion structure similar to that of phosphatidylcholine (PC). They can substitute for each other to a substantial extent, certainly in relation to membrane functions. In the present study, the profiles of DGCC and diacyl PC molecular species of symbiotic dinoflagellates from Acropora sp., Millepora platyphylla and Sinularia flexibilis were determined by high-performance liquid chromatography with high-resolution mass-spectrometry. Colonies of Acropora sp. were characterized by higher contents of DGCC with eicosapentaenoic acid (20:5n-3) and C₂₈ polyunsaturated fatty acids; S. flexibilis, by a higher content of DGCC with palmitic acid (16:0); and M. platyphylla, by a higher content of DGCC with docosahexaenoic acid (22:6n-3). Although the DGCC profile of the corals under study has distinctive features, it shows both similarities with and differences from the DGCC profiles of previously studied corals. Probably, each coral symbiont species has its own specific DGCC molecular species profile that is additionally modified in a certain way depending on environmental conditions created by the coral host. Molecular species DGCC and PC profiles were different. The most abundant PC molecular species were 16:0/22:5 and 38:4 in Acropora sp.; 39:5 and 38:4 in S. flexibilis; and 38:6, 16:0/22:5 and 18:0/22:6 in M. platyphylla. Thus, there is no clear evidence for any compensation or interchangeability between PC and DGCC.     

Differential stability of photosynthetic membranes and fatty acid composition at elevated temperature in Symbiodinium

Coral reefs are threatened by increasing surface seawater temperatures resulting from climate change. Reef-building corals symbiotic with dinoflagellates in the genus Symbiodinium experience dramatic reductions in algal densities when exposed to temperatures above the long-term local summer average, leading to a phenomenon called coral bleaching. Although the temperature-dependent loss in photosynthetic function of the algal symbionts has been widely recognized as one of the early events leading to coral bleaching, there is considerable debate regarding the actual damage site. We have tested the relative thermal stability and composition of membranes in Symbiodinium exposed to high temperature. Our results show that melting curves of photosynthetic membranes from different symbiotic dinoflagellates substantiate a species-specific sensitivity to high temperature, while variations in fatty acid composition under high temperature rather suggest a complex process in which various modifications in lipid composition may be involved. Our results do not support the role of unsaturation of fatty acids of the thylakoid membrane as being mechanistically involved in bleaching nor as being a dependable tool for the diagnosis of thermal susceptibility of symbiotic reef corals.     

Lipid composition of positively buoyant eggs of reef building corals

Lipid composition of the eggs of three reef building corals, Acropora millepora, A. tenuis and Montipora digitata, were determined. Sixty to 70% of the egg dry weight was lipid, which consisted of wax esters (69.5–81.8%), triacylglycerols (1.1–8.4%) and polar lipids c/mainly phospholipids (11.9–13.2%). Montipora digitata also contained some polar lipids typical of the thylakoid membrane in chloroplasts, probably due to the presence of symbiotic zooxanthellae in the eggs. The wax esters appeared to be the major contributor to positive buoyancy of the eggs, and specific gravity of wax esters in A. millepora was estimated to be 0.92. Among the fatty acids of the wax esters, 34.9–51.3% was hexadecanoic acid (16:0) while the major fatty acids in polar lipids were octadecenoic acid (18:1), hexadecanoic acid (16:0), eicosapentaenoic acid (20:5) and eicosatetraenoic acid (20:4). The wax ester appears to be the main component of the 4.5 6.0 m diameter lipid droplets which fill most of the central mass of the coral eggs.     

Lipids of the Green Alga BotryococcusCultured in a Batch Mode

The lipid fraction of the green alga Botryococcuscultured in a batch mode was found to contain polar lipids (more than 50% of the total lipids), di- and triacylglycerols, sterols and their esters, free fatty acids, and hydrocarbons. In aging culture, the content of polar lipids somewhat decreased and that of triacylglycerols increased by more than four times. The content of hydrocarbons in the algal biomass did not exceed 0.9% and depended little on the culture age. Intracellular lipids contained saturated and unsaturated (mono-, di-, and trienoic) fatty acids. The maximum content of C_{16 : 3}and -C_{18 : 3}fatty acids (up to 35% of the total fatty acids) was detected in the phase of active growth. The extracellular and intracellular lipids of the alga differed in the proportion of particular lipids and in the fatty acid pattern.     

Dynamics of lipid and fatty acid composition of shallow-water corals under thermal stress: an experimental approach

Coral bleaching induces changes in lipid and fatty acid composition that result in low lipid content, reducing the likelihood of coral survival. Species-specific differences in the metabolism of lipid reserves may contribute to the differential resistance of corals under acute heat exposures. Here, we examined the dynamics of lipids and fatty acid abundance in corals subjected to short-term heat stress. The stony corals Acropora intermedia, Montipora digitata, and the soft coral Sinularia capitalis all showed a 60–75% decline in both storage and structural lipids. However, S. capitalis and M. digitata exhibited no significant change in the percentages of structural lipids (i.e., polar lipids and sterols) until they had lost 90–95% of their endosymbionts, whereas A. intermedia showed a rapid decline in structural lipids after a 50% loss of symbionts. After a 90–95% loss of symbionts under heat stress, all three corals showed a relative depletion of polyunsaturated fatty acids that had symbiont biomarkers, suggesting that polyunsaturated fatty acids were translocated from the symbiont to the coral host tissue.     

Lipid Composition of the Yeastlike and Mycelial Mucor hiemalis Cells Grown in the Presence of 4-Chloroaniline

The fungus Mucor hiemalis F-1156, which is commonly thought to be monomorphic, produced two types of cells, yeastlike and mycelial, during growth in a medium containing 4-chloroaniline. Among the polar lipids of yeastlike cells, diphosphatidylglycerol was dominant, while phosphatidylcholine and phosphatidylethanolamine were present in minor amounts. Conversely, mycelial cells mainly contained phosphatidylcholine and phosphatidylethanolamine, whereas the content of diphosphatidylglycerol was low. The neutral lipids of yeastlike cells were dominated by diacylglycerides, sterols, and fatty acids. The content of triacylglycerides and sterol esters was low. Yeastlike cells contained higher amounts of saturated fatty acids and lower amounts of unsaturated fatty acids than the mycelium. The content of stearic acid in the fatty acids of the mycelium grown in the presence of 4-chloroaniline was as high as 25.3–29.9%.     

Adaptational changes in cellular phospholipids and fatty acid composition of the food pathogen Listeria monocytogenes as a stress response to disinfectant sanitizer benzalkonium chloride

Aims: This study provides a first approach to observing the alterations of the cell membrane lipids in the adaptation response of Listeria monocytogenes to the sanitizer benzalkonium chloride. Methods and Results: A thorough investigation of the composition of polar and neutral lipids from L. monocytogenes grown when exposed to benzalkonium chloride is compared to cells optimally grown. The adaptation mechanism of L. monocytogenes in the presence of benzalkonium chloride caused (i) an increase in saturated‐chain fatty acids (mainly C_16:0 and C_18:0) and unsaturated fatty acids (mainly C_16:1 and C_18:1) at the expense of branched‐chain fatty acids (mainly C_a‐15:0 and C_a‐17:0) mainly because of neutral fatty acids; (ii) no alteration in the percentage of neutral and polar lipid content among total lipids; (iii) a decrease in lipid phosphorus and (iv) an obvious increase in the anionic phospholipids and a decrease in the amphiphilic phosphoaminolipid. Conclusions: These lipid changes could lead to decreased membrane fluidity and also to modifications of physicochemical properties of cell surface and thus changes in bacterial adhesion to abiotic surfaces. Significance and Impact of the Study: The adaptation and resistance of L. monocytogenes to disinfectants is able to change its physiology to allow growth in food‐processing plants. Understanding microbial stress response mechanisms would improve the effective use of disinfectants.     

Ontogenetic change in the lipid and fatty acid composition of scleractinian coral larvae

Some scleractinian coral larvae have an extraordinary capacity to delay metamorphosis, and this is reflected in the large geographic range of many species. Coral eggs typically contain a high proportion of wax esters, which have been hypothesized to provide a source of energy for long-distance dispersal. To better understand the role of lipids in the dispersal of broadcast spawning coral larvae, ontogenetic changes in the lipid and fatty acid composition of Goniastrea retiformis were measured from the eggs until larvae were 30 days old. Egg biomass was 78.8 ± 0.5% lipids, 86.3 ± 0.2% of which were wax esters, 9.3 ± 0.0% polar lipids, 4.1 ± 0.2% sterols, and 0.3 ± 0.1% triacylglycerols. The biomass of wax esters declined significantly through time, while polar lipids, sterols and triacylglycerols remained relatively constant, suggesting that wax esters are the prime source of energy for development. The most prevalent fatty acid in the eggs was palmitic acid, a marker of the dinoflagellate Symbiodinium, highlighting the importance of symbiosis in coral reproductive ecology. The proportion of polyunsaturated fatty acids declined through time, suggesting that they are essential for larval development. Interestingly, triacylglycerols are only abundant in the propagules that contain Symbiodinium, suggesting important differences in the energetic of dispersal among species with vertical and horizontal transmission of symbionts.     

Biodegradation of solar by Candida guilliermondii strain 1

Summary Candida guilliermondii strain 1 was grown on solar as a sole carbon source for 14 days, and the lipid classes were investigated. The yeast showed high affinity towards hydrocarbons of short chain length, and within 6 days the cellular lipid classes represented 39.69%, 27.50%, 15.35%, 2.23%, 16.20% of hydrocarbons, neutral lipids, free fatty acids, sterols and polar lipids respectively. Undecanoic and hexadecanoic acids were the major fatty acids of the cellular neutral lipids and oleic acid was the major component of the polar lipids.     

The Lotus japonicus acyl‐acyl carrier protein thioesterase FatM is required for mycorrhiza formation and lipid accumulation of Rhizophagus irregularis

Arbuscular mycorrhiza (AM) fungi establish symbiotic interactions with plants, providing the host plant with minerals, i.e. phosphate, in exchange for organic carbon. Arbuscular mycorrhiza fungi of the order Glomerales produce vesicles which store lipids as an energy and carbon source. Acyl‐acyl carrier protein (ACP) thioesterases (Fat) are essential components of the plant plastid‐localized fatty acid synthase and determine the chain length of de novo synthesized fatty acids. In addition to the ubiquitous FatA and FatB thioesterases, AM‐competent plants contain an additional, AM‐specific, FatM gene. Here, we characterize FatM from Lotus japonicus by phenotypically analyzing fatm mutant lines and by studying the biochemical function of the recombinant FatM protein. Reduced shoot phosphate content in fatm indicates compromised symbiotic phosphate uptake due to reduced arbuscule branching, and the fungus shows reduced lipid accumulation accompanied by the occurrence of smaller and less frequent vesicles. Lipid profiling reveals a decrease in mycorrhiza‐specific phospholipid forms, AM fungal signature fatty acids (e.g. 16:1ω5, 18:1ω7 and 20:3) and storage lipids. Recombinant FatM shows preference for palmitoyl (16:0)‐ACP, indicating that large amounts of 16:0 fatty acid are exported from the plastids of arbuscule‐containing cells. Stable isotope labeling with [¹³C₂]acetate showed reduced incorporation into mycorrhiza‐specific fatty acids in the fatm mutant. Therefore, colonized cells reprogram plastidial de novo fatty acid synthesis towards the production of extra amounts of 16:0, which is in agreement with previous results that fatty acid‐containing lipids are transported from the plant to the fungus.     

Composition, accumulation and utilization of yolk lipids in teleost fish

Lipid reserves in teleost eggs are stored in lipoprotein yolk and, in some species, a discrete oil globule. Lipoprotein yolk lipids are primarily polar lipids, especially phosphatidylcholine and phosphatidylethanolamine (PE), and are rich in (n–3) polyunsaturated fatty acids, especially 22:6(n–3) (docosahexaenoic acid, DHA). Oil consists of neutral lipids and is rich in monounsaturated fatty acids (MUFA). Egg lipids are derived from dietary fatty acid, fatty acid mobilized from reserves and possibly fatty acid synthesized de novo. There is selective incorporation of essential fatty acids, particularly DHA, into yolk lipids and discrimination against incorporation of 22:1(n–11). Lipid is delivered to the oocyte by vitellogenin, which is rich in polar lipids, and likely also by other lipoproteins, especially very low density lipoprotein, which is rich in triacylglycerol (TAG). All classes of lipid may be used as fuel during embryonic and larval development and MUFA are preferred fatty acids for catabolism by embryos. Catabolism of oil globules is frequently delayed until latter stages of development. In some species, DHA derived from hydrolysis of phospholipid may be conserved by transfer to the neutral lipid. Recent work has expanded knowledge of the role of DHA in membrane structure, especially in neural tissue, and molecular species analysis has indicated that PE containing sn-1 oleic acid is a prime contributor to membrane fluidity. The results of this type of study provide an explanation for the selection pressures that influence yolk lipid composition. Future work ought to expand knowledge of specific roles of individual fatty acids in embryos along with knowledge of the ecological physiology of ovarian recrudescence, environmental influences on vitellogenin and yolk lipid composition, and the control of yolk lipid accumulation and utilization.