Changes in biomass and chemical composition during lecithotrophic larval development of the southern king crab, Lithodes santolla (Molina)

Changes in biomass and elemental composition (dry mass, W; carbon, C; nitrogen, N; hydrogen, H) were studied in the laboratory during complete larval and early juvenile development of the southern king crab, Lithodes santolla (Molina), formerly known as Lithodes antarcticus (Jacquinot). At 6±0.5 °C, total larval development from hatching to metamorphosis lasted about 10 weeks, comprising three demersal zoeal stages and a benthic megalopa, with mean stage durations of 4, 7, 11 and 47 days, respectively. No differences in development duration or mortality were observed in larvae either fed with Artemia sp. nauplii or unfed, indicating that all larval stages of L. santolla are lecithotrophic. First feeding and growth were consistently observed immediately after metamorphosis to the first juvenile crab stage. Regardless of the presence or absence of food, W, C, N and H decreased throughout larval development. Also the C:N mass ratio decreased significantly, from 7.7 at hatching to 4.1 at metamorphosis, indicating that a large initial lipid store remaining from the egg yolk was gradually utilized as an internal energy source, while proteins played a minor role as a metabolic substrate. In total, 56-58% of the initial quantities of C and H present at hatching, and 20% of N were lost during nonfeeding larval development to metamorphosis. Nine to ten percent of the initially present C, N and H were lost with larval exuviae, half of these losses occurring in the three zoeal stages combined and another half in the megalopa stage alone. Metabolic biomass degradation accounted for losses of about 47-50% in C and H but for only 10% in N. Hence, most of the losses in C and H reflected metabolic energy consumption (primarily lipid degradation), while about half of the losses in N and two thirds of those in W were due to larval exuviation. Complete independence from food throughout larval development is based on an enhanced maternal energy investment per offspring and on energy-saving mechanisms such as low larval locomotory activity and low exuvial losses. These traits are interpreted as bioenergetic adaptations to food-limited conditions in Subantarctic regions, where a pronounced seasonality of day length limits the period of primary production, while low temperatures enforce a long duration of pelagic development.     

Lipid and fatty acid composition of striped bass (Morone saxatilis) larvae during development

Changes in lipid class, fatty acid composition, protein, and dry and wet weights of fertilized eggs and developing larvae of striped bass (Morone saxatilis) fed with the live food, Artemia, were investigated. A decrease of wet and dry weights and moisture was observed at the beginning of the larval stage. Larvae regained the original moisture level, and wet and dry weights increased steadily after feeding. Total lipids decreased from 190 μg/egg in fertilized eggs to 151 μg/egg during hatching and increased after feeding. When total lipid contents were expressed as a percentage of larval dry weight, a decline of lipid did not occur until after feeding. Total protein, on the other hand, increased right after feeding, but there was some variation between days. Polar lipids increased significantly from 20 μg/egg at the egg stage to 199 μg/larva at 26 days post-hatching (DPH), 2 days before the onset of metamorphosis, while neutral lipids declined from 175 μg/egg to 80 μg/larva during the same time period. Wax/steryl esters decreased from 150 μg/egg in fertilized eggs to 32 μg/larva at 26 DPH. Triacylglycerols dropped from 21 μg/egg to 15 μg/larva before feeding and increased gradually after feeding. In contrast, the level of cholesterol increased 2–3-fold. There was a significant increase of phospholipids, particularly phosphatidylcholine in larvae after feeding. The fatty acid composition of fish larvae was significantly influenced by the diet, Artemia. There was an indication of catabolism of endogenous eicosapentaenoic and docosahexaenoic acids during metamorphosis.     

Patterns of protein synthesis in salivary glands ofDrosophila melanogaster during larval and prepupal development

Summary Patterns of protein synthesis in the salivary glands ofDrosophila melanogaster have been studied throughout late larval and prepupal development by pulse labelling the tissues with³⁵S-methionine. Specific changes to the pattern of proteins synthesized during development are found and the significance of these changes is discussed in view of the known changes in gene (puffing) activity which occur at the same times. We review the problem of salivary gland function in prepupalDrosophila.     

Cell culture models of fatty acid overload: Problems and solutions

High plasma levels of fatty acids occur in a variety of metabolic diseases. Cellular effects of fatty acid overload resulting in negative cellular responses (lipotoxicity) are often studied in vitro, in an attempt to understand mechanisms involved in these diseases. Fatty acids are poorly soluble, and thus usually studied when complexed to albumins such as bovine serum albumin (BSA). The conjugation of fatty acids to albumin requires care pertaining to preparation of the solutions, effective free fatty acid concentrations, use of different fatty acid species, types of BSA, appropriate controls and ensuring cellular fatty acid uptake. This review discusses lipotoxicity models, the potential problems encountered when using these cellular models, as well as practical solutions for difficulties encountered.     

Ontogenetic changes in biochemical composition during larval and early postlarval development of Lepidophthalmus louisianensis, a ghost shrimp with abbreviated development

Changes in growth and biochemical composition during the transition from egg through zoea to decapodid in the ghost shrimp, Lepidophthalmus louisianensis (Schmitt, 1935), were documented in terms of dry weight, lipid classes, fatty acid composition, and carbon to nitrogen (C:N) ratios. Larvae of the ghost shrimp were mass-reared in the laboratory (28°C; 20‰ S) from hatching to the decapodid stage. Iatroscan lipid class analysis revealed that major lipid classes in recently produced eggs were phospholipids (80.8±1.3%) and triglycerides (16.0±1.1%), which decreased during the incubation period. Polar lipids (zoea I: 77.4±1.7%; zoea II: 77.5±2.1%; decapodid: 80.0±1.7%) and neutral lipids, of which free fatty acids (zoea I: 10.5±2.7%; zoea II: 13.1±5.2%; decapodid: 7.8±2.1%) were dominant, represented the major lipid classes in the zoeal and decapodid stages. Triglycerides were present in small amounts. The predominant fatty acids of L. louisianensis eggs, zoeae and decapodids were palmitic (16:0), stearic (18:0), eicosapentaenoic (20:5ω3), oleic (18:1ω9), and arachidonic (20:4ω6). Elemental composition of eggs, larvae, and the decapodid stage revealed conspicuous changes in the C:N ratio, with N being relatively stable during larval development but C decreasing during the decapodid stage. These data suggest independence of newly hatched L. louisianensis on external energy resources. This combined with the ability to incorporate saturated fatty acids into polar lipids provides a selective advantage for fast development of new tissue and growth, characteristic of decapod crustacean larvae with lecithotrophic development.     

Main phospholipids and their fatty acid composition in muscle and cephalothorax of the edible Mediterranean crustacean Palinurus vulgaris (spiny lobster)

The total lipids of muscle and cephalothorax of Mediterranean lobster Palinurus vulgaris were found to be 1.0% and 2.4% of the wet tissue of which the phospholipids represented 66.5% and 47.5%, respectively. The main PhL saturated, monounsaturated and polyunsaturated fatty acids in muscle and cephalothorax were C16:0, C18:0, C18:1ω-9, C18:1ω-7, C20:4ω-6, C20:5ω-3 and C22:6ω-3. 2-OH C14:0 and cyclo-17:0 fatty acids were also identified though in low percentages. The main individual PhL in muscle were found to be phosphatidylcholine (53.5%), 72.0% of which corresponded to the structure of 1,2-diacyl-glycerocholine while the rest 28.0% to 1-O-alkyl-2-acyl-glycerocholine or 1-O-(1-alkenyl)-2-acyl-glycerocholine and phosphatidylethanolamine (19.3%), 75.0% of which corresponded to the structure of 1,2-diacyl-glyceroethanolamine and 25% to 1-O-alkyl-2-acyl-glyceroethanolamine or 1-O-(1-alkenyl)-2-acyl-glyceroethanolamine. Cephalothorax main PhL were found to be PC and PE (66.4% and 18.8%, respectively). In muscle and cephalothorax PC ω-3 fatty acids amounted 7.78% and 8.60%, while in PE amounted 30.77% and 23.65% respectively. Furthermore, in both tissues PhL, cardiolipine phosphatidylserine, phosphatidylinositol, sphingomyelin and lysophosphatidylcholine, were also found.     

Effects of food availability on larval development in the slipper limpet Crepidula onyx (Sowerby)

Effects of food availability on the larval survival and development of Crepidula onyx were studied in four experiments by feeding the larvae with different concentrations of the chrysophyte Isochrysis galbana and by starving the larvae for different periods of time. Food concentration had a clear impact on the survival, growth and development time of C. onyx veligers. Larval development occurred only at 10⁴ cells ml⁻¹ and higher algal concentrations. No shell increment was detected in the veligers cultured for 12 days at 10² cells ml⁻¹I. galbana or the blank control. At 10³ cells ml⁻¹, there was only a slight increase in shell length over 12 days. At 10⁴ cells ml⁻¹, about 40% of the larvae became competent in 18 days. At 10⁵ and 10⁶ cells ml⁻¹, more than 90% of the larvae reached competence in 7 days. Initial starvation negatively affected the larval development, but the sensitivity differed among parameters measured on day 5: lower survivorship was detected only for larvae that had suffered 3 days or longer initial starvation, whereas one-day initial starvation caused shorter shells and lower percentage of competent larvae. Three days of continuous feeding was required for 50% of the larvae to reach competence. After feeding for 3 days, most larvae could become competent to metamorphose even under starvation. The time of starvation was also critical: larvae that suffered 1-day food deprivation in the first 2 days of larval release had shorter shells and lowered percent competent larvae than those that suffered the same length of food deprivation in later stages of development. Our study thus indicates that both food concentration and short-term starvation have detrimental effects on the larval development of this species, and that once the larva has consumed certain amount of food, starvation may induce metamorphosis.     

Adipocyte-specific inactivation of Acyl-CoA synthetase fatty acid transport protein 4 (Fatp4) in mice causes adipose hypertrophy and alterations in metabolism of complex lipids under high fat diet

Fatp4 exhibits acyl-CoA synthetase activity and is thereby able to catalyze the activation of fatty acids for further metabolism. However, its actual function in most tissues remains unresolved, and its role in cellular fatty acid uptake is still controversial. To characterize Fatp4 functions in adipocytes in vivo, we generated a mouse line with adipocyte-specific inactivation of the Fatp4 gene (Fatp4(A-/-)). Under standard conditions mutant mice showed no phenotypical aberrance. Uptake of radiolabeled palmitic and lignoceric acid into adipose tissue of Fatp4(A-/-) mice was unchanged. When exposed to a diet enriched in long chain fatty acids, Fatp4(A-/-) mice gained more body weight compared with control mice, although they were not consuming more food. Pronounced obesity was accompanied by a thicker layer of subcutaneous fat and greater adipocyte circumference, although expression of genes involved in de novo lipogenesis was not changed. However, the increase in total fat mass was contrasted by a significant decrease in various phospholipids, sphingomyelin, and cholesteryl esters in adipocytes. Livers of Fatp4-deficient animals under a high fat diet exhibited a higher degree of fatty degeneration. Nonetheless, no evidence for changes in insulin sensitivity and adipose inflammation was found. In summary, the results of this study confirm that Fatp4 is not crucial for fatty acid uptake into adipocytes. Instead, under the condition of a diet enriched in long chain fatty acids, adipocyte-specific Fatp4 deficiency results in adipose hypertrophy and profound alterations in the metabolism of complex lipids.     

Lipid Composition of the Brain in the Vitamin B12-Deficient Fruit Bat (Rousettus aegyptiacus) with Neurological Impairment

Abstract: The Egyptian fruit bat Rousettus aegyptiacus develops severe vitamin B₁₂ deficiency when fed a diet of fresh peeled fruit and water. In a group of bats fed this diet, B₁₂ concentrations in the serum and brain were low, and neurological impairment, evidenced by deficient or absent hindlimb groping or grasping ability and climbing difficulties, was manifest. Control bats fed the identical diet supplemented with B₁₂ showed no such changes. Fatty acid analysis of whole brain homogenates showed a higher level of 20:4 in the deficient group. Phosphatidylcholine showed a marginally higher percentage of 18:3. The total percentage of branched chain fatty acids of phos-phatidylethanolamine was four times higher in deficient brains, comprising 2% of the total. Sphingomyelin showed a slightly higher percentage of 15:0, and a significantly lower percentage of long chain fatty acids C-24 and longer ( p < 0.01). The compositions of nonhydroxy fatty acids in cerebroside were unchanged. Examination of phospholipids showed that 8.9 ± 0.4% of total phosphorus was present as sphingomyelin in deficient bats, compared with 11.9 ± 1.2% in control animals (p < 0.05). There were no statistically significant differences in the concentrations of total brain lipid, protein, phospholipid, glycosphingolipid, cholesterol and plasmalogen between B₁₂-deficient and control bats.     

Individual variation of human plantar stratum corneum lipids, determined by automated multiple development of high-performance thin-layer chromatography plates

The stratum corneum lipids are unique in composition and have been used frequently as a model system of the skin's lipid barrier. Automated multiple development (AMD) of high-performance thin-layer chromatography plates in combination with a 25-step gradient, based on methanol, diethyl ether and n-hexane separated the six major human plantar stratum corneum lipids. Post-chromatographic staining of these lipids with a solution of MnCl₂H₂SO₄ at 130°C or a solution of CuSO₄H₃PO₄ at 140°C allowed visualization of the lipids and quantification. The MnCl₂H₂SO₄ solution stained saturated fatty acids less intensity. Therefore, the CuSO₄H₃PO₄ solution was used for quantification and we found, on average, 2.06% (w/w) cholesterol 3-sulphate, 20.16% (w/w) free fatty acids, 20.25% (w/w) ceramides, 43.53% (w/w) non-esterified sterols, 4.56% (w/w) triacylglycerols and 9.4% (w/w) sterolesters in the human plantar stratum corneum extracts. The concentration of phospholipids was less than 1% (w/w). In addition, the lipid composition of twenty different human plantar stratum corneum extracts was determined. Statistics revealed a correlation between the ratio of free fatty acids and non-esterified sterols (r=0.832, p<0.01, n=20). Several control experiments proved that this correlation is not due to the extraction method, the post-chromatographic staining procedure or bacterial contamination of the stratum corneum.     

Lipid peroxidation and antioxidant defence status during larval development and metamorphosis of giant prawn,Macrobrachium rosenbergii

In the present communication we studied the involvement of reactive oxygen species and alteration in antioxidant defence status during larval development and metamorphosis of giant prawn, Macrobrachium rosenbergii. Overall results indicate that there was a decline in endogenous lipid peroxidation level during larval development. Activity of superoxide dismutase was the lowest in early larval stages (Zoea-I and II) and thereafter increased in V and VI stages, followed by a decrease in the subsequent larval stages. Catalase and glutathione peroxidase did not exhibit specific pattern of changes during development. Reduced glutathione content exhibited an incremental increase during larval progression until metamorphosis. Ascorbic acid content of the larval tissue remained unaltered during development but a sharp fall was marked in its content in the post-larvae. Hence it is concluded that early larvae face high oxidative stress as evident from the high content of thiobarbituric acid reactive substances. This may be due to direct exposure of larvae to ambient oxygen of the water as well as their low antioxidant potential. However, during development with the augmentation in antioxidant reserve of the larval tissues a diminution in the oxidative stress was recorded. Thus it is presumed that antioxidant defences play an important role in providing protection to the developing larvae from oxidative assault during larval progression and metamorphosis.     

Formation of (n-9) and (n-7) cis-monounsaturated fatty acids in seeds of higher plants

The relative abundance of (n-9) and (n-7) isomers in the monounsaturated fatty acids of seed lipids has been determined for selected plants in order to assess the biosynthetic reactions involved in their formation. 9 Desaturation of stearic acid to (n-9) octadecenoic acid is almost exclusively operative in the formation of monounsaturated fatty acids in the seeds of Helianthus annuus, Glycine max and Brassica napus, cv. Quinta and Erglu, in which chain elongation of monounsaturated fatty acids terminates at the level of an 18 carbon chain. 9 Desaturation of palmitic acid is a minor yet significant pathway in the seeds of Sinapis alba and Brassica napus, cv. Rapol and Tira, in which chain elongation of monounsaturated fatty acids occurs extensively beyond the 18 carbon chain. In each of these seeds, both (n-9) and (n-7) octadecenoic acids formed are subsequently elongated to icosenoic acids. However, elongation of the (n-7) isomer is terminated at the level of a 20 carbon chain, whereas the (n-9) icosenoic acid is selectively elongated to docosenoic acid and even up to tetracosenoic acid in Sinapis alba. 9 Desaturation of palmitic acid followed by elongation to (n-7) octadecenoic acid occurs to a minor extent in the seeds of Tropaeolum majus. Only the (n-9) octadecenoic acid, and not its (n-7) isomer, is elongated to icosenoic and docosenoic acids.     

Comparative evaluation and selection of a method for lipid and fatty acid extraction from macroalgae

A comparative evaluation of Bligh and Dyer, Folch, and Cequier-Sánchez methods for quantitative determination of total lipids (TLs) and fatty acids (FAs) was accomplished in selective green (Ulva fasciata), red (Gracilaria corticata), and brown algae (Sargassum tenerrimum) using a full factorial categorical design. Applications of sonication and buffer individually on lipid extraction solvent systems were also evaluated. The FA recoveries obtained from the aforementioned methods were compared with those of direct transesterification (DT) methods to identify the best extraction methods. The experimental design showed that macroalgal matrix, extraction method, and buffer were key determinants for TL and FA recoveries (P ? 0.05), exhibiting significant interactions. But sonication gave erratic results with no interaction with any of the factors investigated. The buffered solvent system of Folch rendered the highest TL yield in U. fasciata and G. corticata while the buffered system of Bligh and Dyer gave the highest yield in S. tenerrimum. DT methods were more convenient and accurate for FA quantification and rendered 1.5–2 times higher yields when compared with the best conventional method, minimizing the use of chlorinated solvents, their cost of analysis, and disposal. The buffered solvent system was found to be the most appropriate for lipid research in macroalgae.     

Relative importance of parental and larval nutrition on larval development and metamorphosis of the sea urchin Strongylocentrotus droebachiensis

We examined the relative importance of parental nutritional condition and larval food ration on the rates of development, growth and metamorphosis of larvae of Strongylocentrotus droebachiensis (Müller) in a laboratory experiment. Parents were reared for 22 months on either a high ration of kelp (Laminaria spp., 6 days week⁻¹) supplemented with mussel flesh (Mytilus spp., 1 day week⁻¹) (KM), or a low ration of kelp (1 day week⁻¹) (KL). Larvae were fed either a high ration (5000 cells ml⁻¹) or a low ration (500 cells ml⁻¹) of microalgae (Dunaliella tertiolecta). Larval food ration had a strong effect on the rates of development, growth, and metamorphosis, which were all significantly greater in larvae fed the high ration. Test diameter of settlers also was significantly greater in the high than the low ration. Parental nutritional condition had little or no effect on the rates of development and growth, and no effect on settler size. The rate of metamorphosis was significantly higher in larvae from the KM than the KL treatment in the high but not the low ration (where rates of metamorphosis were similar). Although parental condition generally had a small effect on larval development, our results suggest that when planktonic food is abundant, larvae of adults from nutritionally rich habitats (such as kelp beds) may metamorphose sooner than those of adults from nutritionally poor habitats (such as barrens).     

Lipid fatty acid and protein pattern of equine prostasome-like vesicles

The semen of several mammals contains vesicles of different composition and origin. We have recently reported on the presence of lipoprotein vesicles in stallion semen. To a certain extent, these resemble human prostasomes, but differ from them in amount and composition. These horse-semen prostasome-like vesicles may be important, not only in horse reproductive physiology, but also in view of stallion semen cryopreservation. In this paper, we have studied horse-semen prostasome-like vesicles and found that they possess less saturated fatty acid than human prostasomes. Moreover, their protein pattern (SDS-PAGE electrophoresis) shows that the 30–50-kDa fraction is less abundant in stallion vesicles. In addition, fluidity (measured as fluorescence anisotropy of diphenylhexatriene) is higher in horse prostasome-like vesicles than in human prostasomes, albeit being much lower than that of most membranes. These findings may be connected to some species-related differences in reproductive physiology: the vaginal milieu of the mare is not acidic and the deposition of semen is intrauterine in the horse but vaginal in humans.     

Oviposition deterrents in larval frass of the cotton boll worm, Helicoverpa armigera (Lepidoptera: Noctuidae): chemical identification and electroantennography analysis

Oviposition deterrents in the frass of cotton bollworm (CBW), Helicoverpa armigera larvae fed on an artificial diet (FA) and on cotton Gossypium hirsutum leaves (FC) were investigated by behavioral bioassays and electroantennography analyses in the laboratory. It was found that a water suspension or a hexane extract of the frass FA or FC, in contrast to the corresponding foods, significantly deterred oviposition of conspecifics. When hexane extracts of the frass FA and FC were further partitioned into polar and neutral lipid fractions, two polar fractions significantly reduced oviposition. The neutral fraction from frass FC also exhibited significant deterrence, although the activity was much lower than that of the corresponding polar fraction. The polar lipid fractions contained several fatty acids, mainly palmitic and oleic acid at the ratio nearly 1:1. A blend of authentic fatty acids of the same composition found in frass FA or FC mimicked the deterring effect. Moreover, these fatty acids and their blend at the ratio found in frass FA or FC elicited significant electroantennogram responses and typical dose-response curves. Thus, it is suggested that CBW larvae may deploy two types of oviposition deterrents: a non-specific and a specific one. The former is a blend of fatty acids, independent of food and plays an important role in oviposition deterrence, whereas the latter may be produced only when the larvae feed on cotton leaves. The possible explanations of this deployment have also been discussed.     

Synthesis and secretion of salivary gland proteins in Drosophila gibberosa during larval and prepupal development

Summary The late larvae of Drosophila gibberosa Patterson and Mainland choose different pupariation sites than the larvae of Drosophila melanogaster Meigen. Since the larvae of D. gibberosa do not attach themselves to the substratum, the salivary glands contain only a small amount of the glue proteins before pupariation. Proteins comprising the salivary gland secretions of late larvae of these two species were compared and found to be qualitatively quite different. Only five polypeptides with the same molecular masses were identified in both species. The rate of protein synthesis in the salivary glands of D. gibberosa continued to increase through the late larval stage and pupariation. As a consequence, the total amount of protein contained in the salivary glands also continued to increase after pupariation. To demonstrate temporal changes in protein synthesis from 48 h before pupariation to 28 h after pupariation, newly synthesized polypeptides were pulse labeled by culturing salivary glands in vitro. The patterns of polypeptide synthesis fell into four major groups depending upon whether the synthesis of a protein stopped shortly after pupariation, stopped during late pupariation, increased at pupariation, or was initiated after pupariation. Changing patterns of protein synthesis are correlated with the known changes in gene puffing during this developmental period.     

Developmental patterns of larval growth in the edible spider crab, Maja brachydactyla (Decapoda: Majidae)

The large edible spider crab Maja brachydactyla Balss, 1922, an overexploited coastal fishery resource in Galicia (NW Spain), is considered as a potential aquaculture candidate. Patterns of its larval growth were studied under controlled laboratory conditions (constant 18 ± 1 °C; 36‰ salinity; photoperiod ca. 12:12 h; lipid-enriched Artemia metanauplii provided as food). From hatching through complete larval development and metamorphosis to the first juvenile crab instar, changes in carapace size, dry weight (DW), ash content, elemental composition (carbon, hydrogen, nitrogen; CHN), and proximate biochemical composition (total proteins, lipids, carbohydrates; Pr, L, Ch) were measured in successive stages (zoea I, II, megalopa, crab I). Body size may be described as a linear function of the number of molting cycles, whereas the amounts of DW, CHN, Pr, L, and Ch per individual increased exponentially (3 to 9 fold). The highest growth rates were observed in L, C and H, the lowest in DW, Pr and N. As a consequence of these patterns, the C:N mass ratio as well as the fractions of L, C and H (in % of DW) increased significantly, while those of Pr and N decreased from 26% to 16% of DW. Throughout development, however, Pr remained the principal biochemical component of total DW. Positive correlations between biochemical and CHN data allow for estimates of Pr from N and of L from C values per individual. The patterns of larval growth observed in M. brachydactyla are, in general, similar to those previously described for other brachyuran crabs with a planktotrophic mode of larval development.     

Egg production and early development of Thysanoessa inermis and Euphausia pacifica (Crustacea: Euphausiacea) in the northern Gulf of Alaska

Early life history patterns were studied in the dominant euphausiids from the northern Gulf of Alaska (GOA) in 2001-2004. Gravid females of Thysanoessa inermis were observed in April and May. Brood size varied from 10 to 1021 eggs with an average of 138 ± 19 (95% CI) eggs female^− 1. Most gravid females started to release eggs within the first 2 days of incubation. The average number of eggs released per female was similar in incubation Day 1 and 2, but significantly smaller on Day 3 and 4. About 25% of the females were continuously releasing eggs over 3 days rather than producing a single distinctive brood. In contrast, gravid females of Euphausia pacifica were observed from early July through October. Most gravid females released eggs on the first day of observation, while only 2% of females produced eggs repeatedly. Brood size varied from 20 to 246 eggs with an average of 102 ± 12 (95% CI) eggs female^− 1. The relationship between E. pacifica brood size and ambient chlorophyll-a concentration was sigmoidal (r² = 0.73), with food saturated brood size of 144 ± 14(SE, P < 0.001) eggs, and half-saturation occurring at 0.46 ± 0.02(SE, P < 0.001) mg chlorophyll-a m^− 3. The average interbrood interval of E. pacifica reared at 12 °C and satiated food conditions in the laboratory was ∼ 8 days, suggesting their potential individual fecundity in the GOA was 1148-1530 eggs per spawning season. Hatching and early development (from egg to furcilia stage) was studied under 5 °C, 8 °C and 12 °C. Hatching was nearly synchronous and lasted 3-6 h, depending on incubation temperature. Development times from egg to the first furcilia stage ranged between 20 and 33 days for T. inermis, and 15 and 45 days for E. pacifica at 12 °C and 5 °C, respectively.     

Combined effects of temperature and salinity on larval development and attachment of the subtidal barnacle Balanus trigonus Darwin

The combined effects of temperature and salinity on larval development and attachment of Balanus trigonus Darwin (Cirripedia, Balanidae) was examined under controlled laboratory conditions. Whilst larval survivorship was not affected (>70%), the duration of larval development was significantly affected by temperature and salinity. The effect of temperature was comparatively stronger than that of salinity. The majority of nauplius II larvae metamorphosed into cypris stage after 4-5 and 10-11 days at 28 °C (22-34‰) and 18 °C (22-34‰), respectively. Temperature, salinity and the duration of assay had a significant effect on cypris attachment with significant interaction among these main effects. Maximum (>80% in 6 days) and minimum percent attachment (0% in 6 days) on polystyrene surfaces were observed at 24 °C (34‰) and 18 °C (22‰), respectively. At high temperature (28 °C) and low salinity (22-26‰), larvae rapidly (4 days) developed into cyprids, but less than 33% attached. These results suggest that low larval attachment rates may lead to the low recruitment of B. trigonus in Hong Kong waters during summer when the water temperature is high (about 28 °C) and salinity is low (<26‰).