The effect of incubation media on the water exchange of snapping turtle (Chelydra serpentina) eggs and hatchlings

Summary The effect of two different incubation media, sand and vermiculite, on the water exchange of eggs and the mass of hatchlings of snapping turtles (Chelydra serpentina) was assessed. The eggs were incubated fully buried in either sand or vermiculite at 30 °C and egg mass was measured periodically throughout incubation. The wet and dry masses of each hatchling and its residual yolk were measured at the end of incubation. The media had similar water potentials () but their thermal conductivities differed 2.8-fold. The eggs experienced a net water gain during incubation. The rates of water uptake between treatments were not statistically different throught the first 36 days of incubation but were statistically different thereafter, with eggs incubating in sand taking up water at about twice the rate of eggs incubating in vermiculite. Hatchling masses were similar to both media but hatchling water contents were significantly different. Hatchlings incubated in sand had lower water contents than hatchlings incubated in vermiculite even though the eggs in sand took up more water. Hatchling mass was correlated with egg water exchange for eggs incubated in vermiculite but not for eggs incubated in sand. The difference in egg water exchange in the two media appears to be attributable to differences in the thermal conductivity of the media. The presence of such a thermal effect supports the hypothesis that the eggs exchanged water with the media as water vapor. Egg water exchange was limited by the shell and shell membranes and not by the media. The shell and shell membranes appear to present an effective barrier to water uptake.Abbreviations M _{H 2 O} water flux (cm³·day^-1) - L _p hydraulic conductivity (cm·day^-1·kPa^-1) - A shell area (cm²) - A _p pore area (cm²) - l shell thickness (cm) - r pore radius (cm) - viscosity (kPa·day) - P _{EH 2 O} egg water potential (kPa) - P _{AH 2 O} medium water potential (kPa) - G _{H 2 O} water vapor conductance (cm³·day^-1·kPa^-1) - D _{H 2 O} diffusion coefficient (cm²·day^-1) - R gas constant (cm³·kPa·K^-1·cm^-3) - T temperature (K) - P _{EH 2 O} egg water vapor pressure (kPa) - P _{AH 2 O} medium water vapor pressure (kPa) - d egg diameter - K soil hydraulic conductivity (cm²·day^-1·kPa^-1) - DHM hatchling dry mass - WHM hatchiling wet mass - WU water uptake - IM initial egg mass     

Carbohydrate metabolism and restricted oxygen supply in the eggs of the silkworm, Bombyx mori

Increased oxygen supply to diapause eggs of the silkworm (O₂-incubation) effectively prevented diapause initiation and induced the same pattern of glycogen, polyol and lactate levels as was observed in normal non-diapause eggs. Sensitivity to oxygen decreased as embryonic development proceeded. After the termination of this sensitive period, accumulation of polyols and lactate followed.Experiments were carried out to test whether changes in the oxygen permeability of the egg membranes are involved in restricting the supply of this gas to eggs at the onset of diapause. Oxygen permeability of the chorion was measured with apparatus especially designed for this purpose. Although the chorion of the diapause egg was less permeable than that of the non-diapause egg, the oxygen permeability of the chorion does not change appreciably during the early developmental stages of the diapause eggs. The changes in rate of water loss through the egg membranes were measured during the early developmental stages of the embryos. The level of water loss decreased gradually as the formation of serosal cuticle proceeded. Moreover, it was observed that the water loss up to the time of formation of serosal cuticle was closely related to the oxygen permeability of the chorion.From these results, we suggest that the formation of the serosal cuticle may be an additional cause of the restricted oxygen supply at the onset of the diapause.     

Hydraulic resistance to radial water flow in growing hypocotyl of soybean measured by a new pressure-perfusion technique

Hydraulic resistances to water flow have been determined in the cortex of hypocotyls of growing seedlings of soybean (Glycine max L. Merr. cv. Wayne). Data at the cell level (hydraulic conductivity, Lp; half-time of water exchange, T _1/2; elastic modulus, ; diffusivity for the cell-to-cell pathway, D _c) were obtained by the pressure probe, diffusivities for the tissue (D _t) by sorption experiments and the hydraulic conductivity of the entire cortex (Lp_r) by a new pressure-perfusion technique. For cortical cells in the elongating and mature regions of the hypocotyls T _1/2=0.4–15.1 s, Lp=0.2·10^-5–10.0·10^-5 cm s^-1 bar^-1 and D _c=0.1·10^-6–5.5·10^-6 cm² s^-1. Sorption kinetics yielded a tissue diffusivity D _t=0.2·10^-6–0.8·10^-6 cm² s^-1. The sorption kinetics include both cell-wall and cell-to-cell pathways for water transport. By comparing D _c and D _t, it was concluded that during swelling or shrinking of the tissue and during growth a substantial amount of water moves from cell to cell. The pressure-perfusion technique imposed hydrostatic gradients across the cortex either by manipulating the hydrostatic pressure in the xylem of hypocotyl segments or by forcing water from outside into the xylem. In segments with intact cuticle, the hydraulic conductance of the radial path (Lp_r) was a function of the rate of water flow and also of flow direction. In segments without cuticle, Lp_r was large (Lp_r=2·10^-5–20·10^-5 cm s^-1 bar^-1) and exceeded the corticla cell Lp. The results of the pressure-perfusion experiments are not compatible with a cell-to-cell transport and can only the explained by a preferred apoplasmic water movement. A tentative explanation for the differences found in the different types of experiments is that during hydrostatic perfusion the apoplasmic path dominates because of the high hydraulic conductivity of the cell wall or a preferred water movement by film flow in the intercellular space system. For shrinking and swelling experiments and during growth, the films are small and the cell-to-cell path dominates. This could lead to larger gradients in water potential in the tissue than expected from Lp_r. It is suggested that the reason for the preference of the cell-to-cell path during swelling and growth is that the solute contribution to the driving force in the apoplast is small, and tensions normally present in the wall prevent sufficiently thick water films from forming. The solute contribution is not very effective because the reflection coefficient of the cell-wall material should be very small for small solutes. The results demonstrate that in plant tissues the relative magnitude of cell-wall versus cell-to-cell transport could dependent on the physical nature of the driving forces (hydrostatic, osmotic) involved.Abbreviations and symbols D _c diffusivity of the cell-to-cell pathway - D _t diffusivity of the tissue - radial flow rate per cm² of segment surface - Lp hydraulic conductivity of plasma-membrane - Lp_r radial hydraulic conductance of the cortex - T _1/2 half-time of water exchange between cell and surroundings - volumetric elastic modulus     

Effects of the Storage in an Atomosphere of Carbon Dioxide on Ovomucin

The yolk index of newly laid egg was 0.50, while that of the egg stored at 30°C for 15 days in an atmosphere of carbon dioxide at a pressure of 2 kg/cm² and in air was 0.43 and 0.25, respectively.

The carbohydrate content of ovomucin gel (B) obtained from the eggs stored in an atmosphere of carbon dioxide was higher than that of ovomucin gel (B) obtained from the eggs stored in air.

The free boundary electrophoretic pattern of ovomucin gel (B) obtained from the eggs stored in an atmosphere of carbon dioxide consisted of two peaks, and the relative mobility of each peak showed the same value as that of the corresponding each peak of ovomucin gel (B) obtained from newly laid egg white.

The fractionation pattern obtained by density gradient column electrophoresis of ovomucin gel (B) obtained from the eggs stored in an atmosphere of carbon dioxide showed two peaks, peak-F and peak-S, while that of the eggs stored in air showed a considerable diminution in peak-F.

From these results, discussion was made about the occurrence and mechanism of egg white thinning when eggs were stored in an atmosphere of carbon dioxide.     

Preparation ofN-acetylneuraminic acid from delipidated egg yolk

Egg yolk, a large proportion of the egg, was studied for the preparation ofN-acetylneuraminic acid (Neu5Ac). The delipidated hen egg yolk (DEY; 500 kg containing 0.2% w/w, Neu5Ac) was hydrolysed with HCl (pH 1.4) at 80 °C and neutralized with NaOH (pH 6.0). The mixture was filtered and electrodialysed until the conductivity was 240 µS cm^–1. The filtrate was applied on a column of Dowex HCR-W2 (20–50 mesh), followed by a column of Dowex 1-X8 (200–400 mesh). The latter column was washed with water, and then eluted with a linear gradient of HCO₂H (0–2m). The eluates containing Neu5Ac were concentrated using a reverse osmosis membrane and, finally, rotary evaporated at 40 °C. The residue was then lyophilized to yield 500 g Neu5Ac. The purity of Neu5Ac was >98% (TBA method). HPLC, NMR spectroscopy and TLC chromatography of the product obtained from the DEY showed that Neu5Ac was the sole derivative present in egg yolk. The DEY, a byproduct from egg processing plants, was found to be an excellent source for the large-scale preparation of Neu5Ac.Abbreviations Neu5Ac N-acetylneuraminic acid - Neu5Gc N-glycolylneuraminic acid - DEY delipidated egg yolk - HPLC high performance liquid chromatography - TLC thin layer chromatography - NMR nuclear magnetic resonance - IR infrared spectroscopy Presented at the 11th International Symposium on Glycoconjugates, Toronto, Canada.     

Changes in elemental composition of fertilized and unfertilized northern pike (Esox lucius) eggs incubated in buffer with and without dimethyl sulfoxide: An X-ray microanalysis study

Fertilized and unfertilized eggs from the northern pike (Esox lucius) were incubated 2 hr in buffer with 0 and 10% (v/v) dimethyl sulfoxide and then quickly frozen in the wells of aluminum blocks submerged in liquid nitrogen. Control eggs and ovarian fluid were similarly frozen immediately after collection. The frozen eggs were sectioned, freeze dried, mounted on stubs, and carbon coated. X-ray microanalysis was used to determine changes in element levels and dimethyl sulfoxide (Me₂SO) penetration in the zona radiata, cytoplasm, cortical alveoli, and egg yolk. Unfertilized eggs incubated without Me₂SO showed decreased levels of Na, Cl, and K in the zona radiata; fertilized eggs, incubated without Me₂SO showed decreased levels of Na, P, and Cl in the zona radiata and increased levels of K in the cytoplasm; unfertilized eggs, incubated with 10% Me₂SO showed decreased Na and Cl in the zona radiata, decreased K in the cytoplasm and increased K in the cortical alveoli; fertilized eggs incubated in buffer with 10% Me₂SO showed decreased levels of Na, P, Cl, and K (zona radiata), P, Cl, and K (cytoplasm), Na (yolk), and increased Cl in the yolk (all P<.01). Me₂SO (v/v) levels reached 1.5-3.1% in the zona radiata, 0-3.2% in cytoplasm, 2.3-8.7% in cortical alveoli, and 0-1.6% in the yolk. Unfertilized eggs showed more Me₂SO penetration than fertilized eggs.     

Nondormanz-Entwicklung prospektiver Diapause-Eier vonBombyx mori mit oder ohne Chorion unter Paraffinöl

Summary Prospective diapause eggs ofBombyx mori become permeable to water in or after contact with paraffin, and they die before reaching diapause. If the eggs are hindered from drying up, their germ anlagen develop to diapausing germ bands. Prospective diapause eggs opened in paraffin, always develop without egg diapause, but their degree of organogenesis depends on the chorion: When eggs are completely dechorionized most of them develop to hatching or nearly hatching larvae; when eggs are completely dechorionized, but their chorion remains in the paraffin, the degree of organogenes is issignificantly lower; and when the opened eggs keep 1/2–3/4 of the chorion, their organogenesis is significantly lower than in the two previous experiments.It is discussed that nondormancy development ofprospective diapause eggs in vitro is not a specific effect of culture media containing water but is possible in paraffin oil too. It is not only possible to stop but also to prevent egg diapause. Nothing, as yet, can be said about the prospective significance of the chorion's reducing factor in organogenesis.     

Hydropy and ultrastructure of egg envelopes in Aleochara bilineata (Coleoptera, Staphylinidae)

Aleochara bilineata oviposits in soil microhabitats likely to contain the dipteran pupae that are hosts of its ectoparasitoid first instar larvae. The eggs of A. bilineata have a rigid chorion but they are nonetheless hydropic and, after 30 h of development, start to increase in volume and do so until 50 h. This increase in volume is due to absorption of water. The eggs increase their initial volume by a factor of 1.68 that corresponds to an increase of 44.44% of initial weight. To explain this augmentation in volume, we describe the modifications occurring in the egg chorion during hydropy. The increase in volume in such a rigid egg is made possible through the fragmentation of the chorion which, initially dense and regular, becomes fragmented. Such adaptation enables female A. bilineata to oviposit hydropic eggs in habitats where mechanical resistance is needed. Accepted: 29 October 2000     

Adhesion mechanisms in European whitefish Coregonus lavaretus eggs: is this a survival mechanism for high‐energy spawning grounds?

This study examined the potential biochemical and mechanical structures that may contribute to egg adhesion in European whitefish Coregonus lavaretus. Experiments showed that eggs from a population of C. lavaretus from Loch Eck remained non‐adhesive in a solution chemically similar to ovarian fluid but became adhesive seconds after contact with water. Examination of the ultrastructure of the chorion showed that the morphology changed significantly after contact with water, with nodule‐like protuberances attached to connective filaments on the surface present in water‐hardened but not non‐water hardened eggs. Biochemical analysis showed the presence of Chain A, RNase ZF‐3e proteins in the chorion of water‐hardened but not non‐water hardened eggs. Histochemical staining of the chorion of C. lavaretus eggs showed that the externa, but not the interna, stained positively for the presence of glycoproteins. From these results, it was concluded that C. lavaretus from Loch Eck possess both anatomical and biochemical adhesive mechanisms that have been undocumented in this species so far.     

Ultrastructure de l'œuf de Triatoma infestans Klug

Summary The thick rigid chorion of the egg of Triatoma secreted by the follicle cells shows two porous layers: an aerial layer in the exochorion, an alveolar one in the endochorion. The anterior part of the eggshell is closed up by an operculum which is heaved up by the hatching larva. The operculum has no alveolar layer. The air enters through the numerous holes of the shell surface into the aerial layer and through the micropyles into the alveolar layer. The egg has no respiratory plastron.The follicle cells produce also a vitelline envelope whose structure shows a rapid condensation at fertilization time. During its development the embryo secretes two layers: serosal and embryonic cuticle.At high humidities, at low temperatures the egg is able to increase its weight during the early stages of embryogenesis, and this increase stops when the serosal cuticle is secreted. In a dry atmosphere the egg loses water but can develop if the temperature is higher than 20°C.The little permeability of the egg is related to the structure of its envelopes. The chorion and the vitelline envelope prevent the water from getting out of the egg. The serosal cuticle seems to be opposed to the penetration of the water into the egg. The role of the embryonic cuticle is probably limited in the transit of water.

Nous remercions Messieurs les Professeurs Maillet et Folliot qui ont mis le microscope R.C.A. à notre disposition, Madame Allo et Mademoiselle Le Gac, technicienne au microscope à balayage J.S.M. S1, pour leur collaboration technique.     

Gas exchange and energy metabolism of the ostrich (Struthio camelus) embryo

We measured oxygen consumption ( ) and carbon dioxide emission ( ) rates, air-cell gas partial pressures of oxygen (P_AO₂) and CO₂ (P_ACO₂), eggshell water vapour conductance and energy content of the ostrich (Struthio camelus) egg, ‘true hatchling’ and residual yolk, and calculated RQ and total oxygen consumption ( ) for ostrich eggs incubated at 36.5°C and 25% relative humidity. The pattern showed a drop of approximately 5% before internal pipping. just prior to internal pipping agrees with allometric calculations. Despite the higher incubation temperature compared to other studies, and the resultant shorter incubation duration (42 days), (91.7 l kg⁻¹) was similar to a previously reported value. RQ values during the second half of incubation (approx. 0.68) were lower than expected for lipid catabolism. Prior to internal pipping, P_AO₂ and P_ACO₂ were 98 and 48.3 torr (13.1 and 6.4 kPa), respectively. The growth pattern of the ostrich embryo is different from the typical precocial pattern, showing a time delay in the rapid growth phase. As a result, the lowered overall energy expenditure for tissue maintenance, as compared to other species, is reflected in the low yolk utilization and high residual yolk fraction of the whole hatchling dry mass. These could also result from the relatively short incubation period of the ostrich egg, thereby evading desiccation by excess water loss.     

Uptake and distribution of cadmium in the egg of the teleost, Oryzias latipes

Eggs of Oryzius latipes in the blastula stage were exposed to M/100 artificial sea water which contained cadmium at the concentrations of 0.1, 1.0, 10.0, 20.0 or 50.0 mg 1⁻¹. The 96 h TL₅₀, value for cadmium was estimated to be 20 5 mg 1⁻¹. When the eggs were incubated for 24 h in the M/100 sea water with 10.0 mg Cd 1⁻¹ and then rinsed in glycine buffer solution (pH; 2.0), the cadmium content of the egg decreased markedly. Cadmium levels were determined in parts of the embryonic body, the chorion and the yolk sac. The most cadmium was detected in the chorion (94.6%). Prolonged cadmium exposure revealed that most of the cadmium was absorbed by the chorion and little was detected in the embryonic body and the yolk sac.     

Drought tolerance in eggs and juveniles of the Iberian slug, <Emphasis Type="Italic">Arion lusitanicus</Emphasis>

The spread of invasive species is an increasing problem world wide. The invasive slug Arion lusitanicus has spread to most parts of Europe, where it often is considered as a serious pest. There is a need for better knowledge of its ecophysiology to be able to predict the effect of climatic factors, such as temperature and humidity on the population dynamics and abundance. The aim of the present study was to assemble data on the water balance and drought tolerance of eggs and juveniles of A. lusitanicus. Both eggs and juveniles had little capacity to prevent evaporative water loss and lost water when the ambient humidity fell below 99.8 and 99.5%, respectively. The water conductance of the cuticle of juveniles was 242 μg cm⁻² h⁻¹ mmHg⁻¹ and resembles that of other slug species. Both eggs and juveniles of A. lusitanicus tolerate a substantial water loss. There was no difference in water loss resistance between eggs and juveniles, but the eggs were slightly more tolerant to water loss than the juveniles. The percent water loss causing 50% mortality was 72% for the juveniles and 81% for the eggs. Despite A. lusitanicus’ tolerance of substantial water loss, its survival depends on humid habitats.     

Experimental Parameterisation of Principal Physics in Buoyancy Variations of Marine Teleost Eggs

It is generally accepted that the high buoyancy of pelagic marine eggs is due to substantial influx of water across the cell membrane just before ovulation. Here we further develop the theoretical basis by applying laboratory observations of the various components of the fertilized egg in first-principle equations for egg specific gravity (ρ_egg) followed by statistical validation. We selected Atlantic cod as a model animal due to the affluent amount of literature on this species, but also undertook additional dedicated experimental works. We found that specific gravity of yolk plus embryo is central in influencing ρ_egg and thereby the buoyancy. However, our established framework documents the effect on ρ_egg of the initial deposition of the heavy chorion material in the gonad prior to spawning. Thereafter, we describe the temporal changes in ρ_egg during incubation: Generally, the eggs showed a slight rise in ρ_egg from fertilization to mid-gastrulation followed by a gradual decrease until full development of main embryonic organs just before hatching. Ontogenetic changes in ρ_egg were significantly associated with volume and mass changes of yolk plus embryo. The initial ρ_egg at fertilization appeared significantly influenced by the chorion volume fraction which is determined by the combination of the final chorion volume of the oocyte and of the degree of swelling (hydrolyzation) prior to spawning. The outlined principles and algorithms are universal in nature and should therefore be applicable to fish eggs in general.     

Sodium balance in eggs and dechorionated embryos of the Atlantic salmon Salmo salar L. exposed to zinc, aluminium and acid waters

Ionic regulation of eyed eggs of Atlantic salmon was studied using intact eggs and embryos from which the chorion and perivitelline fluid had been removed, a preparation which remained in good condition for at least 2 weeks. Both intact eggs and embryos in freshwater showed similar Na+ influx rates (0.0064 and 0.01 microM g-1 hr-1, respectively) but Na+ efflux rates (0.0024 and 0.0064 microM g-1 hr-1, respectively) were greater in embryos, suggesting that the perivitelline fluid which is known to bind cations has an important function in preventing Na+ loss from the yolk and embryo. Over 90% of the egg Na+ is located in the yolk and embryo but only about 10% is exchangeable while the chorion contains about 8% Na+ which is non-exchangeable. Both eggs and embryos in acid water at pH 4, in Zn2+ 5 mM l-1 and in aluminium 1 mM l-1 showed greatly reduced Na+ uptake but eggs in 10 microM l-1 aluminium or 100 microM l-1 Zn2+ showed normal Na+ balance while embryos were normal in 10 microM l-1 aluminium but showed reduced Na+ uptake in 100 microM l-1 Zn2+. It is concluded that the chorion and perivitelline fluid have a capacity to protect the embryo from metal ions and acid water.     

Fine structure and formation of eggshells in marine Gastrotricha

Summary The fine structure of the gastrotrich eggshell in the hermaphroditic species Turbanella ocellata (Hummon 1974) and the parthenogenetic species Aspidiophorus sp. is described using transmission electron microscopy. The presented evidence strongly suggests that the shell is produced by the egg itself prior to oviposition in both species. The layed egg in Aspidiophorus sp. is provided with a special attachment stalk that is also preformed in the mother animal. Freshly layed eggs of T. ocellata are adhesive all around their surface and lack any specialized structures for attachment. Formation of the spiny eggshell of Aspidiophorus sp. appears to begin with a sudden release of special vesicles containing the preformed spines of the outer eggshell covering. Additional material appears to be secreted by the egg in a more gradual process after the initial vesicle release. The formation of the two fibrous layers in the eggshell of T. ocellata is less well understood and deposition of eggshell material could be seen either as a continuous process or as two separate steps, similar to the events observed for Aspidiophorus sp. For T. ocellata, Tetranchyroderma sp. and Aspidiophorus sp. it is demonstrated that formation of the cuticle occurs as an independent process from that of eggshell formation. This is significantly different from the basic mode of cuticle formation in the annelid line of evolution. The paper argues further that the data support earlier claims of a pronounced difference between the Gastrotricha-Macrodasyida and the Gastrotricha-Paucitubulatina and agree well with the postulated ties of the Gastrotricha and Nematoda. The phylogenetic importance of the eggshell fine-structure is discussed in the framework of present theories on aschelminth phylogeny.Abbreviations cus cuticular spines - cut cuticle - cov coated vesicles - cv cup-shaped vesicles - dp dense particles - ep epidermis - emb embryo - erl lacunae of smooth ER - fgb fibrous and granular bodies - fl fibrous layer - ga Golgi apparatus - gc gut cell - gv Golgi vesicles - im intercellular matrix - isp intercellular space - isl inner shell layer - ld lipid droplet - mdb medium-dense bodies - mvb multivesicular bodies - oc oocyte - od oviduct - osl outer shell layer - o egg - sv spiny vesicles - sh eggshell - st egg-stalk - sl spiny layer - sub substrate - trm trilaminate membrane - yb yolk bodies - yg yolk granule - yoc young oocyte This work was supported by NSF Grant # GB-42211 to R.M. Rieger     

δ18O‐derived incubation temperatures of oviraptorosaur eggs

In order to determine the incubation temperature of eggs laid by non‐avian dinosaurs, we analysed the oxygen isotope compositions of both eggshell carbonate (δ¹⁸O_c) and embryo bone phosphate (δ¹⁸O_p) from seven oviraptorosaur eggs with preserved in ovo embryo bones. These eggs come from the Upper Cretaceous Nanxiong Formation of Jiangxi Province, China. Oviraptorosaur theropods were selected because of their known brooding behaviour as evidenced by preserved adult specimens fossilized in brooding posture on their clutch. Incubation temperature of these embryos was estimated based on the following considerations: eggshell δ¹⁸O_c value reflects the oxygen isotope composition of egg water fluid; embryo bones precipitate from the same egg fluid; and oxygen isotope fractionation between phosphate and water is controlled by the egg temperature. A time‐dependent model predicting the δ¹⁸O_p evolution of the embryo skeleton during incubation as a function of egg temperature was built, and measured δ¹⁸O_c and δ¹⁸O_p values used as boundary conditions. According to the model outputs, oviraptorosaurs incubated their eggs within a 35–40°C range, similar to extant birds and compatible with the known active brooding behaviour of these theropod dinosaurs. Provided that both eggshell and embryo bones preserved their original oxygen isotope compositions, this method could be extended to investigate some reproductive traits of other extinct groups of oviparous amniotes.     

Oil droplets and yolk spheres during development of Medaka embryos

The sizes of oil droplets (globules) and the yolk sphere in the Medaka Oryzias latipes egg were measured in the developmental period from fertilization to hatching. Oil droplets coalesced with one another in the process of shifting toward the vegetal pole, and a single large oil droplet was finally located at the vegetal pole region in most eggs 2 days post-fertilization. The volume of the yolk sphere steeply decreased in the period from 2 to 8 days post-fertilization. The volume of oil droplets also declined linearly from 4 to 10 days post-fertilization. Lipid components exhibited no distinct change during embryogenesis. In order to verify whether oil droplets were required for development of Medaka embryos, oil droplets were artificially removed from the early developing embryos without the chorion (egg envelope). Naked embryos without the oil droplet developed normally to fry in the sterilized incubation medium and grew to the same mature fry as those grown from the control embryos.     

Water loss and metabolic activity in bed bug eggs (Cimex lectularius)

Few studies have evaluated water loss and respiratory activity of insect eggs, particularly insects that are known to live within indoor environments. The present study quantifies water loss and respiratory activity for the eggs of a re‐emerging indoor pest of human environments Cimex lectularius (L.). Water loss is measured gravimetrically and calculated as a function of chorion permeability. For these studies, bed bug eggs are placed at 0% relative humidity and repeatedly weighed over 48 h. Temperature effects and bed bug strain differences on the standard metabolic rate (SMR) and respiratory quotient are measured using closed system respirometry. The SMR (; mL g^?1 h^?1) is measured for two field strain bed bugs and compared with a laboratory strain held at one temperature (25 °C). The standard metabolic rate is measured for Harlan (laboratory) strain bed bug eggs at six different temperatures (15, 20, 25, 30, 35 and 39 °C). Total water loss is not significantly different between all three strains. However, water loss across the chorion (chorion permeability) is significantly different between the Harlan laboratory strain and the two field collected strains. Standard metabolic rates for Harlan (laboratory) strain bed bug eggs increase with temperatures from 15 to 35 °C but decline at 39 °C. Overall, the Harlan bed bug eggs have the largest standard metabolic rates (0.18 ± 0.05 mL g^?1 h^?1) compared with the Epic Center strain eggs (0.14 ± 0.03 mL g^?1 h^?1) and Richmond strain eggs (0.16 ± 0.04 mL g^?1 h^?1), although this difference is not significant.