Identification of the hatching factor of the barnacle Balanus balanoides as the novel eicosanoid 10,11,12-trihydroxy-5,8,14,17-eicosatetraenoic acid

Barnacle egg hatching factor which is released into the mantle cavity where the egg masses are brooded and stimulates embryonic musculature resulting in hatching and liberation of the larvae into the sea has been isolated in a purified form from a common barnacle Balanus balanoides. Derivatised hatching factor has been analysed by GC-MS and identified as 10,11,12-trihydroxy-5,8,14,12-eicosatetraenoic acid, a novel eicosanoid probably formed from endogenous eicosapentaenoic acid (20:5w3). Hatching factor activity is the first specific physiological function to be established for this type of compound.     

Phase-related body-color polyphenism in hatchlings of the desert locust, Schistocerca gregaria: re-examination of the maternal and crowding effects

The mechanism controlling the body color of hatchlings was studied for the desert locust, Schistocerca gregaria. A pheromonal factor secreted by gregarious female adults into the foam plugs of egg pods has been suggested to cause darkening in their progeny. We re-examined the role of this maternal factor by washing or separating eggs at deposition. Eggs produced by crowd-reared female adults were washed with saline or separated individually without being washed immediately after deposition and the body color of the hatchlings from them was compared with that from the eggs unwashed and kept in the egg pod until hatching. Most hatchlings were dark and no significant difference was found in the proportions of dark- and light-colored hatchlings between the treatments and controls. Likewise, eggs separated before the foam plug deposition produced dark-colored hatchlings as in the un-separated controls. These results demonstrated that neither washing nor separation of eggs at deposition affected the hatchling body coloration. The variation in hatchling body color was correlated closely to the body weight at hatching, indicating that hatchling body color had been determined maternally. Green hatchlings reared under crowded conditions remained green until the second stadium at which black patterns were induced. It was concluded that body color at hatching has been determined maternally and crowding during the first nymphal stadium influences nymphal body color but its effect is not manifested until the second stadium. The present study casts doubts on the presence of a recently suggested pheromonal factor on the color of the hatchlings.     

Identification and egg hatching activity of monohydroxy fatty acid eicosanoids in the barnacle Balanus balanoides.

Monohydroxy fatty acids (MHFAs) were isolated from homogenates of the barnacle Balanus balanoides and identified by gas chromatography-mass spectrometry (GC-MS) as 14- and 17-hydroxy docosahexaenoic acids, 8-, 11-, 12-, 15- and 18-hydroxy eicosapentaenoic acids, 13- and 16-hydroxyoctadecatrienoic acids and 9-, 13- and 15-hydroxyoctadecadienoic acids. Each monohydroxy fatty acid was tested for egg hatching activity in a bioassay using Elminius modestus egg masses, but 8-hydroxy-5, 9, 11, 14, 17-eicosapentaenoic acid (8-HEPE) was the only MHFA with barnacle egg hatching activity. Studies on the egg hatching activity of MHFAs prepared from the oxidation of polyunsaturated fatty acids showed that activity was confined to the 8-hydroxy isomer of eicosapentaenoic acid and arachidonic acid, and that unsaturation at C5 and C14, but not C17, was essential for activity. In addition, the 8(R) conformation is necessary for activity, as 8(R)-HEPE caused egg hatching at 10(-7) M whereas the enantiomer 8(S)-HEPE was inactive.     

THE EMERGENCE OF LARVAE FROM FREE EGGS OF THE POTATO-ROOT EELWORM HETERODERA ROSTOCHIENSIS (WOLL.)

A technique for conducting hatching experiments on eggs freed from cysts is described. The form of the hatching response was found to be similar to that of eggs contained within cysts, but the response of the free eggs to the hatching stimulus was slightly more rapid. Investigations into factors affecting free egg hatching showed that it was necessary to presoak cysts before extracting the eggs from them for hatching. Eggs taken from dry cysts or from cysts that had been opened or cracked before presoaking did not respond to diffusate. When free eggs and whole cysts were exposed to the same graded series of dilutions of diffusate, the L.A. values (i.e. log concentrations of hatching factor) derived from plotting the hatching curves were in very close agreement.     

Evidence for embryo–embryo interactions in controlling hatching time and synchronization in the brown marmorated stink bug,Halyomorpha halys (Hemiptera: Pentatomidae)

The mechanisms controlling egg diapause and circadian rhythms of hatching activity have been extensively studied in insects. However, relatively little attention has been paid to the mechanisms controlling synchronized hatching from an egg mass. In this study, we examined the possible involvement of embryo–embryo interaction in controlling hatching time in Halyomorpha halys (Stål). Eggs tended to hatch earlier as the egg mass size increased. Egg separation and clumping of separated eggs at various times showed that hatching synchrony was largely determined shortly before hatching. However, whether eggs were kept in a mass or separated until several hours before hatching also influenced the hatching time, indicating the presence of embryo–embryo interactions. Eggs derived from different masses and kept in physical contact with one another hatched synchronously if their ages were within approximately 8 h. In this case, both younger and older eggs advanced only in hatching time, in contrast to a case of locusts reported by others. Eggs separated by more than 7 mm hatched as synchronously as those kept in a mass when glued to the same substrate, suggesting an important role of the egg substrate in transmitting the vibrational hatching signals to neighboring sibling eggs to synchronize hatching.     

琥珀蚕孵化酶基因AaHE的克隆及启动子活性分析

[目的]琥珀蚕Antheroea assama具有典型的野蚕特征,蚕卵孵化不齐,严重影响琥珀蚕的室内规模化饲养.本研究旨在探究对琥珀蚕卵孵化起关键作用的孵化酶(hatching enzyme)基因及其启动子序列特征,为进一步选择合适的抑制剂或促进剂调节琥珀蚕卵的孵化奠定基础.[方法]采用RACE技术克隆琥珀蚕孵化酶基因...     

Studies on the hatching of miracidia of Dicrocoelium dendriticum (author's transl)]

The eggs of Dicrocoelium dendriticum were induced to open by solutions of formic acid and caproic acid (Table 1). The miracidia hatched in O2-free water after the eggs had been dried with N2 or in vacuum. The miracidia were able to live for 3 hours if water contained 20 mM NaCl, 10 mM KCl, and 1 mM CaCl2. Ca++-ions are obviously necessary for the mobility of miracidia. The experimental use of intestinal juice of the Roman snail Helix pomatia gave hatching results which were dependent on the absence of O2 (exposure to N2) and the presence of bacteria with a still unknown function. The dependence on pH seems to be indirect (Abb. 2). Studies on the permeabilities of the egg shell and the embryonic membrane ("vitelline membrane"), the evidence of an oligosaccharide (Abb. 3) liberated from the "spaltraum" (Abb. 1) during egg-opening, and the determination of the osmotic pressure of the hatching process (50% hatching in 1.2--14. Osmols sucrose/1000 ml H2O; Abb. 4) led to the following hypothesis of hatching mechanism: After the activation of the granular gland of the miracidium an enzyme is released into the extra-embryonic "spaltraum". A polysaccharide is digested to an oligosaccharide which cannot permeate the egg shell and the embryonic membrane. The rising osmotic pressure bursts off the operculum.     

Necator americanus: Activity patterns in the egg and the mechanism of hatching

Necator americanus developed normally in distilled water and in solutions of up to 4% NaCl, hatching however, occurred only in the lower tonicities. Together with other observations, this led to the conclusion that, as with many other nematodes, osmotic changes were critical for emergence. Behavioural movements of the larva within the egg have been described, and it has been suggested that the larva ‘feeds’ within the egg, and this involves head waving and oesophageal pumping into the intestine. Enzymes are thus flushed into the egg, causing membrane changes, an influx of water, and a considerable distention of the egg. The pressure is finally released by the rotary movements of the stoma against the egg membranes, causing a break in the egg through which the larva immediately passes.     

The hatching time of Locusta migratoria under outdoor conditions: role of temperature and adaptive significance

The present study investigates the time of hatching of the migratory locust Locusta migratoria using egg pods that are artificially buried in the soil under outdoor conditions. Most eggs hatch in the mid‐morning, with a peak between 11.00 and 12.00 h, and none hatch before 09.00 or after 16.00 h. Furthermore, most egg pods complete hatching within a day, although some take 2 or 3 days, and egg hatching is interrupted by rain. There are no large differences in hatching time from May to September. Laboratory experiments in which the eggs are exposed to temperatures simulating outdoor conditions show that soil temperature is the main factor controlling hatching activity. The increase in temperature in the morning appears to trigger egg hatching, as confirmed by laboratory experiments, which may explain the similar hatching times between seasons. The seasonal patterns of temperature variation and hatching time suggest that the hatching time of L. migratoria eggs may be adjusted to allow the hatchlings to be exposed to high temperatures in the afternoon so that they can harden their bodies quickly.     

The ability of Baltic cod eggs to maintain neutral buoyancy and the opportunity for survival in fluctuating conditions in the Baltic Sea

In the brackish water of the Baltic Sea successful spawning of Baltic cod Gadus morhua is restricted to the Bornholm, Gdansk and Gotland basins below the halocline, occurring at 50–80 m depth. Due to irregular mixing of the deep water, stagnant conditions occur regularly accompanied with unfavourable oxygen conditions. In avoiding stressful oxygen conditions maintenance of egg buoyancy is considered a major limiting factor for successful spawning of Baltic cod. Batches of eggs were incubated experimentally in a density gradient column. Egg specific gravity changed during development, decreasing from the time of gastrulation, then increasing prior to hatching. The changes in specific gravity varied among egg batches from different females and were related to egg quality, egg size and ambient salinity. Eggs achieve different specific gravity depending on incubation salinity. Initial egg specific gravity together with the ability of eggs to gain and maintain buoyancy up to hatching, determine larval specific gravity and the depth where hatching will occur, and thus opportunities for larval survival, avoiding stressful oxygen conditions and developing at favourable feeding conditions.     

Conservation of the egg envelope digestion mechanism of hatching enzyme in euteleostean fishes

We purified two hatching enzymes, namely high choriolytic enzyme (HCE; EC 3.4.24.67) and low choriolytic enzyme (LCE; EC 3.4.24.66), from the hatching liquid of Fundulus heteroclitus, which were named Fundulus HCE (FHCE) and Fundulus LCE (FLCE). FHCE swelled the inner layer of egg envelope, and FLCE completely digested the FHCE-swollen envelope. In addition, we cloned three Fundulus cDNAs orthologous to cDNAs for the medaka precursors of egg envelope subunit proteins (i.e. choriogenins H, H minor and L) from the female liver. Cleavage sites of FHCE and FLCE on egg envelope subunit proteins were determined by comparing the N-terminal amino acid sequences of digests with the sequences deduced from the cDNAs for egg envelope subunit proteins. FHCE and FLCE cleaved different sites of the subunit proteins. FHCE efficiently cleaved the Pro-X-Y repeat regions into tripeptides to dodecapeptides to swell the envelope, whereas FLCE cleaved the inside of the zona pellucida domain, the core structure of egg envelope subunit protein, to completely digest the FHCE-swollen envelope. A comparison showed that the positions of hatching enzyme cleavage sites on egg envelope subunit proteins were strictly conserved between Fundulus and medaka. Finally, we extended such a comparison to three other euteleosts (i.e. three-spined stickleback, spotted halibut and rainbow trout) and found that the egg envelope digestion mechanism was well conserved among them. During evolution, the egg envelope digestion by HCE and LCE orthologs was established in the lineage of euteleosts, and the mechanism is suggested to be conserved.     

Ovigerous-hair stripping substance (OHSS) in an estuarine crab: purification, preliminary characterization, and appearance of the activity in the developing embryos

Ovigerous-hair stripping substance (OHSS) is an active factor in crab hatch water (i.e., filtered medium into which zoea larvae have been released). This factor participates in stripping off the egg attachment structures (i.e., egg case, funiculus, and the coat investing ovigerous hairs) that remain attached to the female's ovigerous hairs after larval release. Thus this activity prepares the hairs for the next clutch of embryos. OHSS activity of an estuarine crab, Sesarma haematocheir, eluted as a single peak on molecular-sieve chromatography, but this peak still showed two protein bands at 32 kDa and 30 kDa on SDS-PAGE. The two protein bands stained with a polyclonal antiserum raised to the active fractions from molecular-sieve chromatography. Moreover, antibodies purified from this polyclonal OHSS antiserum also recognized both the 32-kDa and 30-kDa bands. OHSS immunoreactivity and biological activity were associated with the attachment structures that remained connected to the ovigerous hairs after hatching. In developing embryos, both protein bands could be stained immunochemically at least 10 days before hatching. But OHSS biological activity appeared only 3 days before hatching. The immunoreactive protein bands were not observed in the zoea, but OHSS bioreactivity was present, though greatly reduced. The 32-kDa protein, at least, is probably an active OHSS, and the 30-kDa protein band may also be OHSS-related. The OHSS appears to be produced and stored by the developing embryo. Upon hatching, most of the material may be trapped by the remnant structures, and the remainder is released into the ambient water.     

Egg temperature and initial brood patch area determine hatching asynchrony in Magellanic penguin Spheniscus magellanicus

In birds, the adaptive significance of hatching asynchrony has been under debate for many years and the parental effects on hatching asynchrony have been largely assumed but not often tested. Some authors suggest that hatching asynchrony depends on the incubation onset and many factors have been shown to influence hatching asynchrony in different species. Our objective was to analyze the exact timing of the onset of incubation and if this affects hatching asynchrony; and, in addition, which other factors (brood patch development, incubation position, adult body condition, intra‐clutch egg dimorphism, laying date and year) affect hatching asynchrony in Magellanic penguins Spheniscus magellanicus. We first estimated the eggshell temperature at which embryo development starts, with a non‐destructive and novel method. We then recorded individual egg temperatures in 61 nests during incubation, and related them, and other breeding parameters, to hatching asynchrony. We also observed incubation positions in 307 nests. We found a significant positive relationship between hatching asynchrony and the temperature that the first‐laid egg experienced during egg laying and between hatching asynchrony and the initial brood patch area. We also found a negative relationship between hatching asynchrony and the difference in temperature between second and first‐laid eggs within a clutch, measured after the egg‐laying period was finished. We ruled out position of the eggs during incubation, adult body condition, egg volume, laying date, and study year as factors influencing hatching asynchrony. The egg temperature during laying and the difference in temperature between eggs of a clutch are determinants of hatching asynchrony in Magellanic penguins.     

Seasonal declines in reproductive success of the common tern Sterna hirundo: timing or parental quality?

Reproductive success declines over the course of the breeding season in many bird species. Two categories of hypothesis have been evoked to explain this decline. The “timing” hypothesis suggests that seasonal declines in breeding success are attributable to the date of laying. The “parental quality” hypothesis suggests that seasonal declines result from the fact that young, inexperienced, or low quality birds breed later in the season. To evaluate the relative importance of timing and parental quality, egg exchanges and removals were used to manipulate hatching dates of common terns Sterna hirundo. Indices of quality, attendance, provisioning rates, and reproductive success of birds in three experimental groups (delayed hatch pairs, advanced hatch pairs, and pairs induced to relay) were compared to those of date‐matched controls. Pairs that hatched chicks early raised more chicks than pairs hatching chicks late in the season, regardless of initial laying date. This suggests that hatching chicks early is advantageous in itself. Our results, however, also support the parental quality hypothesis. There was a significant negative relationship between natural laying date and fledging success, independent of hatching date. Differences in chick growth and survival suggest that higher quality adults may be able to compensate for the disadvantages of late hatching dates and achieve similar reproductive success to that of pairs hatching chicks early. We found that pairs hatching chicks late in the season were subject to more incidents of kleptoparasitism than those hatching chicks early. This may be a proximate factor contributing to seasonal declines in reproductive success for common terns, although such a mechanism would not be likely in non‐colonial species. Failure to control for egg quality may have biased the results of some prior egg exchange experiments. Additionally, altered cost of incubation may be an unavoidable confounding factor in studies designed to manipulate timing of breeding.     

AN ACCOUNT OF THE HATCHING STRATEGIES OF BIRDS

1. Three basic hatching methods are described together with one subsidiary method. The symmetrical method is characterized by rotation of the chick in the egg during hatching climax; a line of damage around the circumference of the egg is evident at the beginning of a pushing phase which causes a fairly symmetrical cap to be broken from the shell. The asymmetrical method is used by a few long-billed species; it involves little or no rotation of the chick in the egg, and produces asymmetrical shell remains. The megapodes have developed a unique hatching method in response to their unusual incubation conditions. Parental assistance has been observed in some species, but only as an auxiliary to either the symmetrical or asymmetrical method. Approximately 150 species have been categorized according to the hatching method(s) they use. 2. Among those species adopting the symmetrical method, there is considerable variability as to how far the chick turns in the egg during hatching climax. On this basis, a spectrum of behaviour, expressed in terms of angle of rotation (θ), has been proposed. At one end lie species such as the bobwhite quail and little owl (θ≥ 360°), and at the other, the ostrich and rhea (θ≤ 90°). 3. The theory that, with the exception of the megapodes, there is only one basic hatching method is examined. The tenets of this theory are found to be inconsistent with recent observations of species differences in hatching behaviour. It is concluded that hatching behaviour is governed by an intrinsic species-specific programme, in turn influenced by mechanical or other external factors. 4. The literature contains several suggestions as to the external factors that might influence hatching technique, but only one detailed investigation. It is proposed that interspecific differences in the mechanical properties of the egg integument (the shell and its underlying membranes) can be regarded as forming a spectrum from very brittle to comparatively tough. The amount of climax rotation by the chick is seen as an adaptive response to brittleness or toughness of the egg integument. The hatching technique of the chick is further modified as a response to the effect of moisture content on the integument. 5. The selective pressures leading to the evolution of the symmetrical and asymmetrical hatching methods are discussed. The previous model for the development of the asymmetrical method is amended to account for those species of gull which may adopt either method.     

Penguin Chicks Benefit from Elevated Yolk Androgen Levels under Sibling Competition

Crested penguins (genus Eudyptes) have a peculiar hatching pattern, with the first-laid egg (A-egg) hatching after the second-laid egg (B-egg) and chicks from A-eggs typically having a much lower survival probability. Maternal yolk androgens have been suggested to contribute to the competitive superiority of the B-chick in southern rockhopper penguins Eudyptes chrysocome, given their important role in mediating sibling competition in other species. We therefore increased the yolk androgen levels in freshly-laid eggs and examined the consequences for sibling competition - via effects on embryonic developmental times, chick growth and early survival. We placed one androgen-treated egg and one control egg into each foster nest, matching them for mass, laying date and laying order. The androgen treatment did not significantly affect embryonic developmental times or chick measurements at hatching. However, elevated yolk androgen levels benefitted chick growth in interaction with the number of siblings in a brood. Chicks from androgen-treated eggs had faster growth in the presence of a sibling than chicks from control eggs. Under these circumstances they also had a higher survival probability. Thus maternal androgens appear to reinforce the observed hatching pattern, facilitating brood reduction. This contrasts to most previous studies in other species where yolk androgens have been shown to compensate for the negative consequences of delayed hatching within the brood hierarchy.     

Comparison of ion transportation before and after egg hatching in Amphinemura sp. (Plecoptera)

Abstract.  An increase in egg size with embryonic development in stoneflies is believed to result from the uptake of water by osmosis. The present study aims to investigate whether a selective ion transport through egg membranes exists before hatching, and whether ions are released after hatching. Viable and nonviable egg masses are incubated in Petri dishes filled with water, and the concentrations of the ions F⁻, Cl⁻, SO₄²⁻, NO₃⁻, Na⁺, K⁻, Mg²⁺ and Ca²⁺ in the water are determined. The ion transport of an egg mass before and after hatching and a nonviable egg mass is then calculated. Before hatching, Cl⁻, SO₄²⁻, NO₃⁻, Na⁺, Mg²⁺ and Ca²⁺ are taken up from the surrounding water into the inner egg. These ions are selectively taken into the egg. After hatching, Cl⁻, SO₄²⁻, Na⁺, Mg²⁺ and Ca²⁺ are released into the surrounding water. The amount of these ions released after hatching is lower than the amount taken up before hatching. Ions that are not released after hatching are considered to be used in embryonic development.     

Schistosoma mansoni: factors affecting hatching of eggs

The effect of light, oxygen tension, reducing conditions and thermal shock on egg hatching in Schistosoma mansoni were examined. Hatching was found to be unaffected by light or dark conditions or aerobic or anaerobic conditions. Cold shock from 15 to 120 sec was also ineffective in stimulating hatching. The reducing agents ascorbic acid and cysteine inhibited egg hatching. However, the oxidized forms of these compounds inhibited hatching as well, indicating that the reducing conditions they provided were not responsible for the inhibition.