Energy flow from spider eggs through dipteran parasite and hymenopteran hyperparasite populations

Summary The incidence of the parasites in the egg sacs of the spider Argiope pulchella was 100% for Sarcophaga banksi and 25% for Tachinobia repanda. In 1976, 237 spider eggs equivalent to 131 gcal/m² were present. Of these, 212 eggs/m² (=117 gcal) were consumed by S. banksi larvae, leaving 25 spiderlings/m² (=14 gcal) to emerge. The density of S. banksi larvae was l/m² (=87 gcal), of which 0.7/m² S. banksi (=41 gcal) successfully emerged; as few as 0.3 S. banksi/m ² (=25 gcal) were infected by T. repanda; only 14 T. repanda/m² (=8 gcal) successfully emerged. Exploitation efficiency was 89% for S. banksi and 29% for T. repanda. Ecological efficiency was 66% for S. banksi and only 9% for T. repanda. The egg sac area of A. pulchella holds a straight line relationship to the energy content of the eggs; the sacs were grouped into 8 different sizes and each one further into groups containing 1, 2, and 3 S. banksi larvae per sac. Analysis of the sacs at the appropriate time revealed that an S. banksi larva consumed a minimum of 114 eggs (=70 gcal), when present as one of a pair in the smallest sac (0.6 cm² area), and a maximum of 476 eggs (=234 gcal), when present alone in the largest sac (1.3 cm²). Despite this wide difference in food intake, all S. banksi (barring those infected by T. repanda) successfully emerged. The energy content of a pharate pupa, which was 125, 92, and 68 gcal in a sac with 1 cm² area containing 1, 2, or 3 S. banksi, depended on the size of the sac and the number of S. banksi per sac. The corresponding values for the imago were 82, 61, and 45 gcal. The efficiency of S. banksi ranged between 60 and 80% for food conversion and between 35 and 56% for pupation.This work was completed at our Palni Centre     

A jumping spider that lays eggs like an insect

The South East Asian salticid, Asemonea tenuipes, lay its eggs like an insect: as individuated capsules in geometrically precise rows. The occurrence of this behaviour is described in a population from Thailand that lays eggs on the underside of mango tree (Mangifera indica) leaves. The rows were vertically arranged at a 90° angle that was parallel to, and varied in relation to the angle of the central leaf rib, indicating that the rib serves as the primary visual cue for orienting the row. Analysis of within-egg row symmetry found evidence that micro-topography – in particular, vertical ‘stepping’ produced by leaf sub-ribs – of the leaf surface plane was responsible for 97% of variability in the relative symmetry of egg placement. Three strategies were identified: (1) crossing the sub-rib and producing localized asymmetry in the egg row; (2) introducing a gap at the sub-rib to maintain symmetry; and (3) ‘compressing’ the egg row into the gap between sub-ribs. The incidence of asymmetry showed a highly significant linear relationship with egg load. It is hypothesized that the use of rows probably represents a solution to the problem of how to surveil temporally staggered clutches of eggs and newly hatched spiderlings simultaneously.     

Energy density of marine pelagic fish eggs

Analysis of the literature on pelagic fish eggs enabled generalizations to be made of their energy densities, because the property of being buoyant in sea water appears to constrain the proximate composition of the eggs and thus to minimize interspecific variation. An energy density of 1.34 J μl⁻¹ of total egg volume is derived for most species spawning eggs without visible oil globules. The energy density of eggs with oil globules is predicted by     x (J μ1¹) where x is the fractional volume of the oil globule.     

Energy metabolism in developing Ascaris lumbricoides eggs. II, The steady state content of intermediary metabolites.

The steady state levels of intermediary metabolites were measured in freeze clamped, developing, dormant, and activated infective Ascaris lumbricoides eggs. The $\text{[ATP]}\text{[ADP]}$ ratio is low in the developmental stages and rises sharply in the dormant egg; on activation of the dormant egg the $\text{[ATP]}\text{[ADP]}$ ratio falls. The levels of the phosphorylated glycolytic intermediates of acetyl-CoA and of isocitrate do not change markedly during development, but the levels of lactate, citrate, 2-oxoglutarate, glutamate, succinate, and malate all show significant changes in the developing, dormant, and activated egg. The dormant egg also appears to be characterized by a low cytoplasmic redox potential.     

Purine nucleotide content of developing Ascaris lumbricoides eggs

Farland W. H. &; Macinnis A. J. 1978. Purine nucleotide content cf developing Ascaris lumbricoides eggs. International Journal for Parasitology8: 177–186. Populations of Ascaris lumbricoides eggs obtained from the terminal portion of the uteri of mature females were shown to develop synchronously, allowing the detection of quantitative and qualitative changes in nucleotide content during development. Application of a method for the preparation of perchloric acid-soluble fractions from Ascaris eggs utilizing Alamine 336S in chloroform is described. This method was useful in neutralizing the extract and for removal of interfering lipids.Guanine nucleotides were found in high concentration in ovarian tissue of adult female worms, and comprise more than 80% of the total acid-soluble nucleotides in 0-day eggs. Muscle tissue contained a predominance of adenine nucleotides.To determine the fate of large concentrations of guanine nucleotides present in 0-day eggs, perchloric acid-soluble fractions were prepared from embryonating eggs on various days of development. Nucleotide content was determined after fractionation on DEAE-cellulose columns,A dramatic decrease (6·2 fold) in guanine nucleotides between 5 and 8 days' embryonation was seen; [GMP] and [GDP] showed the greatest change. ATP concentration increases 3·3 fold through 21 days' embryonation. The total acid-soluble nucleotide content decreased 60% during this time. Uric acid, an end product of purine metabolism, was detectable in 5-day eggs and accumulated through the course of embryonation. The decrease of guanine nucleotides correlates temporally with the increase in DNA content during embryonation. The methodology and results of this study provide a basis for additional study of nucleic acid metabolism during development of Ascaris eggs.     

Parthenogenetic activation decreases the polyphosphoinositide content of frog eggs

Polyphosphoinositides were quantified in metaphase II-arrested eggs of the amphibian Xenopus laevis and 8-10 min later in eggs activated by pricking. The content of phosphatidylinositol 4,5-biphosphate (PIP2) was remarkably high in metaphase II-arrested eggs with respect to that of phosphatidylinositol 4-phosphate (PIP). It was found to drop dramatically at activation. In contrast PIP content did not change significantly.     

Energy metabolism in eggs and larvae of the Senegal sole

Oxygen consumption in Solea senegalensis increased during the egg stage reaching values close to 4 nmol O₂ ind⁻¹ at hatching. After hatching, larval oxygen consumption continued to increase, reaching a maximum rate of 9.97⁻¹±87 nmol O₂ ind⁻¹ h⁻¹ 2 days after the opening of the mouth. Body nitrogen content decreased mainly after exhaustion of yolk reserves. Carbon content decreased during the whole endogenous feeding phase, although it decreased twice as quickly after yolk-sac absorption. The free amino acid (FAA) depletion rate was higher during egg development and the yolk-sac period. Complete yolk absorption coincided with the consumption of the 90% of initial FAA content in the eggs and the remaining FAA were consumed at a lower rate. Based on stoichiometrical calculations, FAA appears to be the most important energy substrate during the egg stage (86%) in the Senegal sole. During the period from hatching to the mouth opening, contributions of FAA and lipids as metabolic fuels were similar (41 and 47%, respectively). The decrease in larval protein content during starvation indicates that amino acids from body protein are used as energy substrates under food deprivation.     

Fatty acid content of eggs determines antipredator performance of fish larvae

Recent work has suggested that provisioning of eggs with certain critical nutrients could be a more meaningful measure of maternal investment and correlate of offspring fitness than traditional measures of egg size. The aim of our study was to assess variability in egg quality and larva quality and to identify connections between them and the implications for larval survival. Egg size, proximate composition, and fatty acid composition were measured for 40 batches of eggs from 8 captive pairs of red drum (Osteichthyes: Sciaenops ocellatus). We reared larvae from these batches of eggs to a common size (10 mm total length, 2-3 weeks posthatching) and assessed routine activity and escape response performance of 671 individuals. Egg fatty acid composition varied more than egg size or proximate composition. Concentrations of certain long chain, highly unsaturated essential fatty acids (e.g., arachidonic acid and docosahexaenoic acid) were the only egg traits that were significantly related to larva quality (measured as escape performance). Reduced escape performance of larvae from eggs with low fatty acid concentrations was not compensated by 3 weeks of feeding on a diet enriched with fatty acids, suggesting irreversible developmental effects. Since fatty acids in eggs originate from the maternal diet, offspring survival may be determined in part by availability of nutrient-rich prey to pre-spawning adults. Migrations, regime shifts, and exploitation of marine communities could operate through this mechanism to influence recruitment in fish populations. Our findings underscore the importance of non-genetic maternal contributions to egg quality and the linkage between environmental conditions experienced by adult females and offspring fitness.     

Hatching of the winter eggs of the fruit-tree red spider mite (Panonychus ulmi (Koch))

Observations on the hatching of winter eggs of Panonychus ulmi (Koch) from apple orchards in England over the 5 years 1962-6 are described. Differences of 2–3 weeks between orchards in the date at which 50% hatch was reached were quite common and this was out of step with petal fall in the majority of orchards. There was a continuous range between early and late hatching populations and a tendency for the populations to hatch in the same order every year. In 1966 populations on Cox's Orange Pippin hatched earlier than those on Worcester Pearmain but the difference was unlikely to be of practical importance. Neither recording accumulated day degrees for populations hatched out-of-doors nor hatching in an incubator after chilling was considered to give a sufficiently reliable forecast of 50% hatch but observations in 1966 suggested that this might be predicted from the total eggs hatched in an incubator expressed as a percentage of total healthy eggs.     

Crystalline calcium phosphate and magnetic mineral content of Daphnia resting eggs

Daphnia is a key crustacean zooplankton of freshwater food chains. One factor that ensures successful propagation is the Daphnia resting eggs, which are able to retain structural integrity under extreme conditions. Until recently little was known about the chemical composition, microanatomy, and physical properties of the egg itself. The current study demonstrates that the resting eggs: (1) have shells that are made up of crystalline calcium phosphate and include a honeycombed structure, and (2) contain magnetic material having properties consistent with magnetite. These properties of the resting eggs may ensure Daphnia survival in harsh environments.     

Changes in the potassium content of sea urchin eggs on fertilization

In the eggs of Arbacia lixula and Paracentrotus lividus an uptake of K occurs during the first 10 minutes following fertilization. Between 10 and 40 minutes K is then released. Both in Arbacia and in Paracentrotus the minimum point of the curve coincides with the nuclear streak stage. A maximum loss of 25 per cent in Arbacia and 20 per cent in Paracentrotus with respect to the amount present in the unfertilized eggs has been found. From 40 minutes up to 1 hour K undergoes a further increase and when the first cleavage sets in the same amount of K is present as in the unfertilized eggs. By treating the eggs with K-free artificial sea water it has been established that about 60 per cent of the K content of the eggs is in a non-diffusible condition. Also under such conditions the eggs when fertilized are able to take up even the very small amount of K present in the medium that was released by them prior to fertilization.     

Variation in the intensity of diapause in winter eggs of fruit tree red spider mite, Panonychus ultni

Winter eggs of Panonychus ulmi from six orchards in Kent showed a range of 3 weeks in the dates of 50 % hatch at field temperatures. From the effects of the duration and temperature of chilling, and the temperature of incubation, it was concluded that samples varied in their chilling requirement, and not in threshold temperatures for development. Diapause was terminated most effectively by chilling initially at o ^oC (for late-hatching strains) or 5 followed by 9 for the last month or two. Heritable variation in diapause intensity is discussed in relation to heat sums and the forecasting of hatch, and to phenology.     

Isolation and characterization of two vitellins from eggs of the spider Polybetes pythagoricus (Araneae: Sparassidae)

Despite vitellins being essential yolk proteins, their presence in spiders remains almost unknown. Two vitellins from the spider Polybetes pythagoricus, named LV1 and LV2, were isolated and their size, shape, lipids, fatty acids, proteins and carbohydrates moieties were determined. LV1 has a density similar to that of HDL with 49.3% lipids, and LV2 has a density similar to that of VHDL with 9.7% lipids. The major neutral lipid present in both vitellins was found to be esterified cholesterol, 16% for LV1 and 24% for LV2. The major fatty acid was 18:1n-9 in LV1 and LV2. Results from native PAGE showed a lipoprotein of 550 kDa for LV1 and three lipoproteins of 571, 400 and 257 kDa for LV2. SDS-PAGE evidenced two major apolipoproteins of 64 and 25 kDa in LV1. The three lipoproteins of LV2 were electroeluted and analyzed by SDS-PAGE, showing different proportions of the same apolipoproteins (181, 67 and 60 kDa). LVs were analyzed by spectrophotometry, immunochemical and electron microscopy, showing that the respiratory pigment hemocyanin was not present as apolipoprotein. This fact evidenced that these LVs were not related to hemolymphatic lipoproteins.     

Influence of temperature on hatching of winter eggs of fruit-tree red spider mite, Panonychus ulmi (Koch)

The effects of the duration and degree of chilling, and the temperature of incubation, on hatching of winter eggs of Panonychus ulmi (Koch) were investigated. For chilling, 0°C and 5°C were more effective than — 5° and 9°, and the limits for the reaction were close to — 10° and 15°. As the chilling period was increased from 60 to 200 days, the percentage hatch on incubation at 21° increased, and the mean incubation time and its variance decreased. Before the maximum effect of chilling was achieved, percentage hatch on incubation at 9° and 15° was higher than at 21°; 27° was lethal to most winter eggs though not to summer eggs. After chilling, the later stages of diapause development could occur at temperatures from 0° to 21°₎ i.e. above and below the threshold temperature for morphogenesis, 6–7° in both winter and summer eggs. Diapause development cannot, therefore, be a unitary process. The significance of the results is discussed in relation to forecasting the time of hatch in the field, and to the phenological aspects of hatching in the spring.