Temperature and pCO2 effect on the bioaccumulation of radionuclides and trace elements in the eggs of the common cuttlefish,Sepia officinalis

The increasing release of CO₂ by human activities leads to ocean acidification and global warming. Both those consequences (i.e., increase in seawater pCO₂ and temperature) may drastically affect the physiology of marine organisms. The effects of low pH and elevated temperature on the bioaccumulation of radionuclides (²⁴¹Am, ¹³⁴Cs) and trace elements (⁶⁰Co, ⁵⁴Mn or ⁷⁵Se) were studied during the embryonic development of the common cuttlefish Sepia officinalis. The lowered accumulation of essential ⁶⁰Co and ⁵⁴Mn with decreasing pH was larger at 16 °C than at 19 °C. Se was not detected in the embryo whereas it penetrated through the eggshell, suggesting that an alternative pathway ensures the supply of this essential metal for the embryo. ²⁴¹Am was totally retained by the eggshell irrespective of pH and temperature. Finally, the amount of Cs found in the peri-vitelline fluid increased with decreasing pH likely because of an enhanced swelling of the cuttlefish egg under elevated CO₂.     

The effect of embryonic development on metal and calcium content in eggs and eggshells in a small passerine

Published information relating to changes in the chemical element content of avian eggs caused by embryonic development is extremely scarce, although it may be crucial for understanding both the presence of anthropogenic pollutants as well as physiological levels of micronutrients. We assessed the variation in concentrations of calcium (Ca) and magnesium (Mg) and nine trace elements: seven essential (chromium (Cr), copper (Cu), nickel (Ni), manganese (Mn), iron (Fe), cobalt (Co) and zinc (Zn)) and two non‐essential (lead (Pb) and cadmium (Cd)) in shells and contents (both egg yolk and egg white) of embryonated and non‐embryonated eggs. We investigated the eggs of the Eurasian Reed Warbler Acrocephalus scirpaceus, a large proportion of whose eggs are infertile in our study population (almost 43% of clutches contain unhatched eggs) as well as significant embryo‐induced eggshell thinning at the equator of embryonated eggs. We found significantly higher concentrations (≥ 22.7%) of all the focal elements in the contents of embryonated eggs in comparison with non‐embryonated eggs, and a very pronounced one for Ca (nearly twice as high). The shells of embryonated eggs contained significantly higher concentrations of Zn (104.1%), Fe (56.5%), Pb (32.8%) and Cu (28.0%) but significantly lower ones of Co (8.9%) and Ca (9.3%) than the shells of non‐embryonated eggs. The simultaneous higher concentrations of all elements in the content of thinner‐shelled embryonated eggs suggest the parallel transfer of these elements along with Ca resorption from the shell into the egg interior during embryo formation. The higher concentration of most elements in the thinner shells of embryonated eggs may be indicative of the maternal deposition of some of these elements in a shell layer not subject to embryonic depletion, or in the eggshell membrane. Our results highlight the need for the careful selection of egg samples, which should differentiate between embryonated and non‐embryonated eggs in the analytical treatment of eggs and eggshells.     

Assessment of the exposure pathway in the uptake and distribution of americium and cesium in cuttlefish (Sepia officinalis) at different stages of its life cycle

Laboratory radiotracer experiments were performed to study the uptake, assimilation and retention of americium (²⁴¹Am) and cesium (¹³⁴Cs) by the common cuttlefish Sepia officinalis. Uptake and loss kinetics of the radionuclides were measured following exposure through sediments, seawater and food at different stages of the animal's life cycle. Sediment was found to be a minor uptake pathway for both radionuclides in juveniles. Following a short seawater exposure, cuttlefish accumulated ²⁴¹Am and ¹³⁴Cs, but only to a limited extent (whole-body CF < 2). Among the cuttlefish organs, branchial hearts and their appendages displayed the highest degree of uptake for ²⁴¹Am (CF = 42 and 16, respectively), but these tissues contained low percentage of total ²⁴¹Am due to their relatively small contribution to whole organism weight. The major fraction of incorporated radionuclides was associated with muscular tissues (viz. 65% and 82% of total ²⁴¹Am and ¹³⁴Cs, respectively). Whole-body loss of ²⁴¹Am and ¹³⁴Cs was relatively rapid (T_b½ = 14 and 6 days, respectively). After dietary exposure, around 60% and 30% of ingested ²⁴¹Am was assimilated into the tissues of juvenile and adult cuttlefish, respectively. However, assimilated ²⁴¹Am was more strongly retained in adults than in juveniles (T_b½ = 28 vs. 5 days, respectively), suggesting that different mechanisms govern ²⁴¹Am elimination at both ages. Ingested ¹³⁴Cs was assimilated to a similar extent in juveniles (29%) and adults (23%), but the depuration rate was four times faster in adults. Our results strongly suggest that these two radionuclides follow different excretion pathways and that the mechanisms can vary with age for a given radionuclide.     

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.     

The brown alga Lobophora variegata, a bioindicator species for surveying metal contamination in tropical marine environments

Uptake and depuration kinetics of Cd, Co, Cr, Mn, Ni and Zn were determined in the brown alga Lobophora variegata exposed to realistic concentrations of these metals, using highly sensitive radiotracer techniques. The experiments were designed to assess the possible influence of varying dissolved metal concentrations on the capacity of metal bioconcentration and retention in the alga. Results indicate that the alga takes up Cd, Co, Cr, Ni, and Zn in direct proportion to their ambient dissolved concentrations over the entire range of concentrations tested (three orders of magnitude). In contrast, Mn was taken up in proportion to its dissolved concentration only over a concentration range of 2 orders of magnitude (up to 250 ng Mn L^− 1, i.e. 4.55 nM), then at higher concentrations its accumulation efficiency slightly decreased. Overall, L. variegata appears to be a reliable bioindicator species that shows a rapid response time in metal uptake (uptake rate constants ranging from 60 to 1,023 d^− 1) and has a suitable potential to furnish valuable information on the bioavailable contamination levels occurring in New Caledonian areas affected by land-based mining activities. Furthermore, due to its wide geographical distribution, L. variegata could be considered as a useful bioindicator species for surveying metal contamination in many other tropical areas.     

Bemerkenswerte endogene Farbveränderung der Eischale von Chioninia delalandii (Duméril & Bibron, 1839) (Reptilia: Sauria: Scincidae)

The paper describes an unusual endogenous eggshell colouration observed in an egg of the Cap Verde skink Chioninia delalandii.A female specimen, kept in a terrarium, laid three eggs. Two of them were considered as fertilized (oval germ-disk, weakly pink). They were embedded 1 cm deep in a layer of moistened clay granules (substrate/water 2:1) and kept under different temperatures (egg 1 “cool”, 26-27 °C; egg 2 “warm”, 29-30 °C). There was a normal embryonic development in both eggs from their volume-enlargement and characteristic allometric growth (egg wide > egg length). The young hatch after 51 and 56 days.A change in eggshell colour, however, occurred in the “warm” kept egg during the last third of its incubation period. It started with a small spot (2-3 mm) in the outer area of the animal egg pole and spread into a dark-violet colouration over the whole eggshell within 15 days. After hatching of the young the shells of both eggs were examined. In the non-coloured egg there was no great difference in colour between the inner and outer egg layer, while in the coloured egg there was a distinct difference between the inner part, which was dark violet-gray, and the pale gray calcareous deck-layer. From the macroscopic view along the edge of the eggshell it was not identifiable, if the colour pigment was infiltrated into protein fibrils of the condensed surface layer.A possible explanation for the eggshell colouration could be an unusual embryonic pigmentation. This assumption is based on the first appearance of a restricted, point-like coloured area and its further regular extension. It might be that dark pigments (melanophores?) reached the eggshell (membrana testacea) and infiltrated the border-area to the condensed surface layer.     

Effect of Diets Supplemented with Different Levels of Manganese,Zinc, and Copper from their Organic or Inorganic Sources on Egg Production and Quality Characteristics in Laying Hens

This experiment was conducted to evaluate the effect of zinc, manganese, and copper sources (inorganic vs. organic) in the diet on laying performance and eggshell quality characteristics. One hundred and eighty Hy-Line W-36 layers at 38 weeks of age were allocated to 36-layer cages of five hens each. Each six cages were randomly assigned to one of the six experimental diets fed from 38 to 53 week of age. In three experimental treatments, the basal diet was supplemented with 65–75–7 or 65–75–7 or 40–40–7 mg/kg of Zn, Mn, and Cu, respectively, from their oxide or sulfate sources. Three other groups were fed diets supplemented with 20–20–3.5 or 40–40–7.5 or 60–60–10.5 mg/kg of organic forms of Zn, Mn, and Cu, respectively. Dietary treatments significantly did affect feed intake (P < 0.001), feed conversion ratio (P < 0.001) and percentage of broken eggs (P < 0.05). Substitution of Zn and Mn oxides (65 and 75 mg kg⁻¹, respectively) with equal amounts of their sulfate forms significantly improved feed intake, feed conversion ratio, percentage of broken eggs, and Haugh Unit (P < 0.05). In addition, laying hens maintained their performance when substitution of Zn and Mn oxides and Cu sulfate (65, 75, and 7 mg kg⁻¹, respectively) reduced up to 20, 20, and 3.5 mg kg⁻¹ by amino acid complexes of the microelements. The results showed that a corn–soybean diet supplemented with the organic forms of Zn, Mn, and Cu at a dosage 50% to 75% lower than NRC recommendation is sufficient to maintain laying performance and can improve eggshell and albumen qualities of the egg in laying hens.     

Uterine and eggshell structure and histochemistry in a lizard with prolonged uterine egg retention (Lacertilia,Scincidae, Saiphos)

The eggshell of lizards is a complex structure composed of organic and inorganic molecules secreted by the oviduct, which protects the embryo by providing a barrier to the external environment and also allows the exchange of respiratory gases and water for life support. Calcium deposited on the surface of the eggshell provides an important nutrient source for the embryo. Variation in physical conditions encountered by eggs results in a tradeoff among these functions and influences eggshell structure. Evolution of prolonged uterine egg retention results in a significant change in the incubation environment, notably reduction in efficiency of gas exchange, and selection should favor a concomitant reduction in eggshell thickness. This model is supported by studies that demonstrate an inverse correlation between eggshell thickness and length of uterine egg retention. One mechanism leading to thinning of the eggshell is reduction in size of uterine shell glands. Saiphos equalis is an Australian scincid lizard with an unusual pattern of geographic variation in reproductive mode. All populations retain eggs in the uterus beyond the embryonic stage at oviposition typical for lizards, and some are viviparous. We compared structure and histochemistry of the uterus and eggshell of two populations of S. equalis, prolonged egg retention, and viviparous to test the hypotheses: 1) eggshell thickness is inversely correlated with length of egg retention and 2) eggshell thickness is positively correlated with size of shell glands. We found support for the first hypothesis but also found that eggshells of both populations are surprisingly thick compared with other lizards. Our histochemical data support prior conclusions that uterine shell glands are the source of protein fiber matrix of the eggshell, but we did not find a correlation between size of shell glands and eggshell thickness. Eggshell thickness is likely determined by density of uterine shell glands in this species. J. Morphol., 2010. © 2010 Wiley‐Liss, Inc.     

Comparison of eggshell porosity and estimated gas flux between the brown‐headed cowbird and two common hosts

The brown‐headed cowbird Molothrus ater is a brood‐parasite that lays eggs in nests of a wide range of host species, including the closely‐related red‐winged blackbird Agelaius phoeniceus and the dickcissel Spiza americana. Although cowbird eggs have accelerated development and hatch sooner than similar‐sized host eggs, this development takes place within a thickened eggshell that could impede gas flux to the developing embryo. We tested the hypothesis that the accelerated development of the cowbird embryo relative to hosts is enabled by an increase in eggshell porosity that allows increased fluxes of respiratory gases to and from the developing embryo. We found cowbird eggshell thickness was significantly greater than the eggshells of these two common hosts. Although the number of pores per egg was similar among all three species, the total pore area per egg in cowbirds was significantly greater than that of either host, despite having a smaller eggshell surface area than the red‐winged blackbird. Cowbird egg pore area was 1.9×larger than that of the red‐winged blackbird. Cowbird eggshells had a significantly greater gas flux than those of the red‐winged blackbird and the dickcissel. When conductance was normalized to published values of egg mass, cowbird eggs had a higher mass‐specific conductance than red‐winged blackbird or dickcissel eggs. These results are consistent with the hypothesis that the rapid development of brown‐headed cowbird embryos is facilitated by increased eggshell porosity, and that changes in eggshell porosity represent an adaptation that enables cowbird eggs to hatch earlier than equivalently‐sized host eggs.     

241Am dating of lake sediments

²⁴¹Am derived from decay of fallout ²⁴¹Pu is now frequently detected in analyses of lake sediments by low-background gamma assay, and offers an alternative to weapons test ¹³⁷Cs in dating recent sediments at those sites where the ¹³⁷Cs record has been degraded by post-depositional mobility or obliterated by Chernobyl fallout. Calculations of the in-growth of ²⁴¹Am from ²⁴¹Pu indicate a nominal distribution broadly similar to that of ¹³⁷Cs, with the maximum ²⁴¹Am activity occuring in fallout dating from 1963. Results from a number of sites suggest that ²⁴¹Am is significantly less mobile in lake sediments than ¹³⁷Cs, and that its distribution in cores reflects more closely the fallout record. Since further decay of existing weapons debris will increase ²⁴¹Am concentrations by about 24% over the next 40 years, ²⁴¹Am is likely to play an increasingly important role in assessing the validity of ²¹⁰Pb dates at sites with varying sediment accumulation rates.     

Solubility of airborne radioactive fuel particles from the Chernobyl reactor and implication to dose

Airborne particles of nuclear fuel from the Chernobyl reactor that had been collected on air filters and stored, were characterised using in vitro dissolution tests to assess effective doses after their inhalation. As solvent, the Gamble biological fluid was used to simulate lung fluid. The solubility of the measured radionuclides decreased in the order ¹³⁷Cs>⁹⁰Sr>>²⁴¹Am^239+240Pu in the simulated lung fluid. The dissolution rate constant of e.g. ^239+249Pu ranged from 0.72 to 5.4×10^–6 g·cm^–2 d^–1 and decreased (for all nuclides) with increasing particle size as predicted from theoretical considerations. Considering the inhalation dose, decreasing dose with size and increasing doses with lower solubility may partly counterbalance each other for ¹³⁷Cs and ⁹⁰Sr. On the other hand, for ²³⁹Pu and ²⁴¹Am larger particles and associated lower solubility both change the resulting dose in the same direction towards lower values. The comparison of the experimentally determined dose coefficients with ICRP values indicates that nuclear fuel particles closely resemble type M material characteristics for ¹³⁷Cs and ⁹⁰Sr and type S material characteristics for ²³⁹Pu and ²⁴¹Am.     

Bemerkenswerte endogene Farbveränderung der Eischale von Chioninia delalandii (Duméril & Bibron, 1839) (Reptilia: Sauria: Scincidae)

The paper describes an unusual endogenous eggshell colouration observed in an egg of the Cap Verde skink Chioninia delalandii.A female specimen, kept in a terrarium, laid three eggs. Two of them were considered as fertilized (oval germ-disk, weakly pink). They were embedded 1 cm deep in a layer of moistened clay granules (substrate/water 2:1) and kept under different temperatures (egg 1 “cool”, 26–27 °C; egg 2 “warm”, 29–30 °C). There was a normal embryonic development in both eggs from their volume-enlargement and characteristic allometric growth (egg wide > egg length). The young hatch after 51 and 56 days.A change in eggshell colour, however, occurred in the “warm” kept egg during the last third of its incubation period. It started with a small spot (2–3 mm) in the outer area of the animal egg pole and spread into a dark-violet colouration over the whole eggshell within 15 days. After hatching of the young the shells of both eggs were examined. In the non-coloured egg there was no great difference in colour between the inner and outer egg layer, while in the coloured egg there was a distinct difference between the inner part, which was dark violet-gray, and the pale gray calcareous deck-layer. From the macroscopic view along the edge of the eggshell it was not identifiable, if the colour pigment was infiltrated into protein fibrils of the condensed surface layer.A possible explanation for the eggshell colouration could be an unusual embryonic pigmentation. This assumption is based on the first appearance of a restricted, point-like coloured area and its further regular extension. It might be that dark pigments (melanophores?) reached the eggshell (membrana testacea) and infiltrated the border-area to the condensed surface layer.     

Plutonium,241Am,90sr,and137cs concentrations in some antarctic matrices

A radioecological survey in Antarctica shows that the^239+240Pu,²³⁸Pu,²⁴¹Am,⁹⁰Sr, and¹³⁷Cs activities were detectable in nearly all the samples. The activity level of^239+240Pu,²⁴¹Am, and¹³⁷Cs in antarctic sediments was about 5–20 times lower than in the northern Adriatic Sea sediments, but the²³⁸Pu activities were relatively high. It was interesting to note that the⁹⁰Sr concentrations in all the sediments tended to be low, which could be the result of the easier exchangeable behavior of⁹⁰Sr in water. High concentrations were detected in mosses and lichens and their activity levels were comparable to those in central Italy. The radionuclide ratio analyses show that the major part of^239+240Pu,²⁴¹Am,⁹⁰Sr, and¹³⁷Cs was a result of nuclear weapon tests. The higher²⁴¹Am/^239+240Pu ratio was observed and it could perhaps be the result of fallout of nuclear weapon tests prior to 1962. The²³⁸Pu/^239+240Pu ratio in the antarctic matrices was about seven times higher than in the Northern hemisphere and it could be inferred that the major part of²³⁸Pu was originating from the SNAP-9A satellite accident.     

Avian eggshell thickness in relation to egg morphometrics,embryonic development,and mercury contamination

Eggshell thickness is important for physiological, ecological, and ecotoxicological studies on birds; however, empirical eggshell thickness measurements for many species and regions are limited. We measured eggshell thickness at the equator and the egg poles for 12 avian species and related eggshell thickness to egg morphometrics, embryonic development, egg status, and mercury contamination. Within an egg, eggshells were approximately 5.1% thicker at the equator than the sharp pole of the egg, although this difference varied among species (0.6%–9.8%). Within Forster's tern (Sterna forsteri), where eggshell thickness was measured at 5 equally spaced positions along the longitude of the egg, eggshell thickness changed more rapidly near the sharp pole of the egg compared to near the blunt pole of the egg. Within species, eggshell thickness was related to egg width and egg volume for six of the 12 species but was not related to egg length for any species. Among species, mean eggshell thickness was strongly related to species mean egg width, egg length, egg volume, and bird body mass, although species mean body mass was the strongest predictor of species mean eggshell thickness. Using three species (American avocet [Recurvirostra americana], black‐necked stilt [Himantopus mexicanus], and Forster's tern), whose nests were carefully monitored, eggshell thickness (including the eggshell membrane) did not differ among viable, naturally abandoned, dead, or failed‐to‐hatch eggs; was not related to total mercury concentrations of the egg content; and did not decrease with embryonic age. Our study also provides a review of all existing eggshell thickness data for these 12 species.     

Determination of heavy metals in eggs of Little Grebe (Tachybaptus ruficollis) around the wastewater treatment ponds,Khon Kaen University

Bird eggs can often be used as a bioindicator of potential effects in environment pollutions. Little Grebe (Tachybaptus ruficollis) lays the eggs around wastewater treatment ponds, Khon Kaen University. The aim of this study is to determine the contamination level of Hg, Pb, Cd, Cr, and Cu in egg content, eggshell and to relate hatching success. Fifteen eggs, four sludge samples, and wastewater samples were collected during September 2016 to April 2017 and were digested and determined using ICP-MS. Clutch size was 1–6 eggs and the weight, width, and length of eggs (mean ± SD) were 11.64 ± 0.91 g., 24.96 ± 0.85 mm, 35.05 ± 1.32 mm, respectively. Hatching success (n = 15) was 96.7%. Cu and Pb were detected at low level in wastewater, and five heavy metals were contaminated in sludge samples. Cu> Cr> Pb> Hg were detected in egg samples (n = 15), and all concentrations in egg content were more than in eggshell. Cr, Cu, Pb, and Hg concentration were not correlated between eggshell and egg content. This study indicated that the heavy metals can be contaminated in sediment, wastewater and can be transferred to egg of Little Grebes. These suggest the ecological risk of heavy metals on other long-living vertebrates living in the area.     

Population growth rate of the parasitic rotifer Proales gigantea,and susceptibility to parasitization in the snail Lymnaea acuminata at different stages of embryonic development

Developing eggs of the host snail Lymnaea acuminata were experimentally parasitized with the parasitic rotifer Proales gigantea to study the population growth rate of the parasite within the snail egg capsule and the susceptibility of the host eggs at different stages of embryonic development. The population growth rate of P. gigantea was 0.46 ± 0.07 individual^–1 day^–1 at the ambient temperature of 18–22 °C. Snail eggs were most susceptible to rotifer attack during the initial stages of development, becoming progressively more resistant after the hippo stage. Yet, regardless of the stage of development, the host embryo was doomed to die without hatching even if one individual rotifer gained entry inside the egg capsule. The presence of P. gigantea within the parasitized egg capsules or in the mucilage had no effect on the developmental rates and hatching success of non-parasitized eggs within the same egg mass.     

Adsorption of Radionuclides (134Cs, 85Sr, 226Ra, 241Am) by Extracted Biomasses of Cyanobacteria (Nostoc Carneum, N. Insulare, Oscillatoria Geminata and Spirulina Laxis-Sima) and Phaeophyceae (Laminaria Digitata and L. Japonica; Waste Products from Alginate Production) at Different pH

The extracted biomasses of four cyanobacteria (Nostoc carneum, Nostoc insulare, Oscillatoria geminata, and Spirulina laxissima) grown in axenic mass cultures, and of four samples of Laminaria obtained from different locations (L. digitata I and II, France; L. japonica I and II, China; all waste products from alginate production) were tested for their ability to adsorb four radionuclides (¹³⁴Cs, ⁸⁵Sr, ²²⁶Ra, and ²⁴¹Am) under different pH regimes. In addition, two of the cyanobacterial biomasses (N. carneum. and O. geminata) and the four Laminaria biomasses were phosphorylated before being tested as radionuclide adsorbers. The non-phosphorylated cyanobacterial biomasses showed very low adsorption of ¹³⁴Cs but substantially higher removal of ⁸⁵Sr and ²²⁶Ra, which increased with increasing pH. ²⁴¹Am was almost completely removed from the solution at low pH, but less at higher pH. After phosphorylation, removal of ¹³⁴Cs, ⁸⁵Sr and ²²⁶Ra by the cyanobacterial biomasses was improved, particularly at lower pH, but there was almost no adsorption of ²⁴¹Am. The non-phosphorylated Laminaria biomasses showed good removal of ¹³⁴Cs and very good adsorption of ⁸⁵Sr and ²²⁶Ra. Removal of ²⁴¹Am was high at low pH but decreased with increasing pH. After phosphorylation, adsorption of ¹³⁴Cs by Laminaria samples was slightly improved; removal of ⁸⁵Sr and ²²⁶Ra was increased at low pH with a tendency towards decrease in adsorption with increasing pH; but almost no ²⁴¹Am was adsorbed. The origin of the cyanobacterial and Laminaria materials appeared to have little effect on the adsorption of the radionuclides.     

Differential transport of Zn, Me and sucrose along the longitudinal axis of developing wheat grains

The hypothesis that Zn and Mn are transported within the grain in a similar manner to sucrose was investigated in the developing wheat grain. Detached ears were cultured in solution containing ⁶⁵Zn, ⁵⁴Mn and [¹⁴C]-sucrose for 10 to 120 min at 18–22 days post-anthesis. At different times the grain was cut transversely into 1-mm sections and the radioactivity in each section determined The embryo region was damaged in some grains to investigate the effect of reduced accumulation rate on the transport of ⁶⁵Za, ⁵⁴Mn and [¹⁴C]-sucrose to the embryo. The distribution of ⁶⁵Zn. ⁵⁴Mn and [¹⁴C]-sucrose between the endosperm cavity sap. endosperm, embryo and pericarp in grains labelled for 2.5 and 6 h at 18–22 days post-anthesis was also determined. [¹⁴C]-su-crose was initially high in the first, embryo-containing section of the grain but decreased progressively to the distal end of the grain. The amount of ⁶⁵Zn along the longitudinal axis of the grain was distributed evenly in each 1-mm section, whilst ⁵⁴Mn accumulated exponentially in the first proximal 1-mm section of the grain and was distributed evenly in the remaining sections. Damaging the embryo had no effect on ⁶⁵Zn and ⁵⁴Mn transport to the section containing the embryo. The pericarp contained almost all of the grain ⁶⁵Za and ⁵⁴Mn, with small amounts found in the embryo, endosperm and endosperm cavity sap. Increasing amounts of [¹⁴C]-sucrose were found in the endosperm as time progressed. The rate of accumulation of ⁶⁵Zn, ⁵⁴Mn and [¹⁴C]-sucrose was much higher in the embiyo than the endosperm: the difference between the embryo and endosperm was especially large for ⁶⁵Zn and ⁵⁴Mn. It is suggested that ⁶⁵Zn and ⁵⁴Mn are not transported within the grain in the same way as [¹⁴C]-sucrose. [¹⁴C]-sucrose moves laterally out of the vascular system of the crease into the endosperm cavity and is subsequently taken up and stored in the endosperm. In contrast, ⁶⁵Zn and ⁵⁴Mn appear to be retained within the vascular system of the crease and may be transported more slowly to grain parts such as the embryo and pericarp tissue.     

Physical features and chitin content of eggs from the mosquito vectors Aedes aegypti,Anopheles aquasalis and Culex quinquefasciatus: Connection with distinct levels of resistance to desiccation

Mosquito eggs are laid in water but freshly laid eggs are susceptible to dehydration, if their surroundings dry out at the first hours of development. During embryogenesis of different mosquito vectors the serosal cuticle, an extracellular matrix, is produced; it wraps the whole embryo and becomes part of the eggshell. This cuticle is an essential component of the egg resistance to desiccation (ERD). However, ERD is variable among species, sustaining egg viability for different periods of time. While Aedes aegypti eggs can survive for months in a dry environment (high ERD), those of Anopheles aquasalis and Culex quinquefasciatus in the same condition last, respectively, for one day (medium ERD) or a few hours (low ERD). Resistance to desiccation is determined by the rate of water loss, dehydration tolerance and total amount of water of a given organism. The ERD variability observed among mosquitoes probably derives from diverse traits. We quantified several attributes of whole eggs, potentially correlated with the rate of water loss: length, width, area, volume, area/volume ratio and weight. In addition, some eggshell aspects were also evaluated, such as absolute and relative weight, weight/area relationship (herein called surface density) and chitin content. Presence of chitin specifically in the serosal cuticle as well as aspects of endochorion external surface were also investigated. Three features could be related to differences on ERD levels: chitin content, directly related to ERD, the increase in the egg volume during embryogenesis and the eggshell surface density, which were both inversely related to ERD. Although data suggest that the amount of chitin in the eggshell is relevant for egg impermeability, the participation of other yet unidentified eggshell attributes must be considered in order to account for the differences in the ERD levels observed among Ae. aegypti, An. aquasalis and Cx. quinquefasciatus.     

Metabolism of the Fe, Cu, Zn, Mg, MN and Co in the ovum of Cancer irroratus (decapod crustacean)]

The concentrations of Fe, Cu, Zn, Mn and Co in the eggs of Cancer irroratus show variations in relation with time running out after laying, that is to say with embryogenesis. The increase of the rates of Fe, Mn and Mg is independant of the variations of the water content. Inversely, the decrease of Cu and Zn concentrations is in close relation with the increase of water content during the same period. The increase of Fe, Mn and Mg concentrations seems to be essentially under the dependance of physico-chemical, rather than biochemical, process in connection with the chitinous nature of the membranes surrounding the egg.