Hatching Synchrony Research Articles

Inter‐specific difference in budburst time and its consequences on egg hatch time and survival of the gall‐making adelgid Adelges japonicus (Monzen) (Hom., Adelgidae)

Abstract: Temporal variation in budburst time of a host plant is important in determining the performance of gall formers. To elucidate whether synchrony of budburst and egg hatch affects the performance of gall‐forming adelgids, the phenology of gallicola egg hatch and its survival were examined in Adelges japonicus (Monzen) on three plants (Picea jezoensis var. jezoensis (Sieb. et Zucc.) Carr., Picea jezoensis var. hondoensis (Mayr) Rehder and Picea sitchensis (Bongard) Carr.) that differed in budburst time. Picea j. jezoensis is native, while P. j. hondoensis and P. sitchensis are introduced plants. Although the date of budburst differed significantly among these plants, neither the date of oviposition nor the date of egg hatch differed significantly among them; most of the eggs hatched after budburst in P. j. jezoensis, while a large portion of eggs hatched before budburst and larval gallicolae waited for the buds to open in P. sitchensis and P. j. hondoensis. To examine the effect of this asynchrony on gallicola survival, the delay of egg mass disappearance with respect to budburst was correlated with the number of gallicolae that colonized each gall. The correlation was significantly positive in P. sitchensis but not significant in P. j. jezoensis. This indicates that in P. sitchensis, gallicola survival decreases with the increasing number of eggs that hatch before budburst, while budburst phenology does not affect gallicola survival in P. j. jezoensis, which is their native host. However, when the number of gallicolae that colonized each gall was compared among the three plants, it did not differ significantly among them. This suggests that lower gallicola survival caused by a greater asynchrony of budburst and egg hatch might be compensated for by other factors (e.g. higher fecundity) that increase the number of gallicolae in the galls.

Stress induced elevation of plasma cortisol in adult female coho salmon (Oncorhynchus kisutch), is reflected in egg cortisol content, but does not appear to affect early development

Circulating levels of cortisol, the major corticosteroid among teleosts, increase in response to environmental Stressors. Cortisol has also been reported to be present in the freshly ovulated eggs of a number of teleost species. Since environmental Stressors have been implicated in the decrease of egg quality in salmonids, this study was conducted to investigate possible connections between egg cortisol content and subsequent viability. A physical Stressor applied to a single group of adult female coho salmon (Oncorhynchus kisutch), during the final two weeks of oogenesis appeared to result in significantly elevated plasma cortisol levels (227.5 ± 61.5 ng/ml) above those observed in a single group of control animals (141.0 ± 42.7 ng/ml), although other factors cannot be ruled out. Mean egg cortisol content (25.3 ± 0.77 ng/g) was significantly higher in the disturbed than in the undisturbed females (9.90 ± 0.94 ng/g), suggesting that cortisol content in eggs of salmonids is reflective of plasma levels during late oogenesis. Gonadosomatic index was unaffected by the treatment, although there was some evidence to suggest that elevated cortisol levels may have hastened ovulation in the experimental group. Paired groups of eggs from single females having either unmanipulated (37.0 ± 5.4 ng/g) or artificially elevated (232.7 ± 13.9 ng/g) levels of cortisol showed no significant differences in terms of time to, or synchrony of hatch, yolk sac to body weight ratio at hatch, growth from hatch to 52 days post fertilization (dpf), or percent mortality. Cortisol was seen to clear rapidly from eggs in both experimental and control groups soon after fertilization, and there was no significant difference observed between groups by 8 dpf, suggesting that maternal cortisol clears from developing embryonic salmon by the late eyed stage and may not be a factor in later development.

Synchronization of Hatching Date with Budburst of Individual Host Trees (Quercus robur) in the Winter Moth (Operophtera brumata) and its Fitness Consequences

1. Due to varying selection pressures among host individuals, herbivorous insects may show local adaptation at the individual level. In the winter moth, synchrony of egg hatching and host tree (Quercus robur L.) budburst may have important fitness consequences and, therefore, may result in a local adaptation to the hosts phenology. However, relatively high gene flow levels may disrupt such a fine-scale adaption. 2. We determined hatching dates of clutches laid by females collected during copulation, and variation in budburst dates of the trees on which these couples were collected. 3. In our study area, budburst date showed substantial variation within years and areas, as the first and last tree to start leafing were separated by up to 26 days. Relative budburst dates of individual trees were constant between years. Average hatching dates differed significantly among clutches and varied over 30 days, a range comparable to that of budburst. 4. Hatching dates were positively associated with budburst of the respective trees indicating individual synchrony, which may be mediated by two mechanisms. First, early active adults are captured more frequently on early trees and late adults on late trees. As adult activity period is positively correlated with date of egg hatch, early clutches will tend to be laid on earlier trees while late clutches will be laid more frequently on late trees. Secondly, a presumed active choice mechanism may additionally increases individual host synchronization. Yet, the latter requires further study. 5. Our data support that synchronization of larval hatching with host budburst is adaptive as it increases adult size and thus expected fitness.

Variation in Incubation Periods and Egg Metabolism in Mallards: Intrinsic Mechanisms to Promote Hatch Synchrony

We investigated factors affecting incubation time and metabolic rates of Mallard (Anas platyrhynchos) eggs incubated under constant environmental conditions. Time required to reach the starpipped stage of hatch varied significantly among females, but not with laying sequence or egg size. Metabolic rate of eggs varied positively with position in the laying sequence and tended to vary among females. Metabolic rate did not vary with egg volume or incubation length. Our results indicate metabolic rate may act as one synchronization mechanism for hatch. The role of maternal effects in development time should be considered in subsequent studies of incubation time in ducks.

Control of Hatching in an Estuarine Terrestrial Crab I. Hatching of Embryos Detached From the Female and Emergence of Mature Larvae.

Embryos of the terrestrial crab Sesarma haematocheir hatch simultaneously just prior to their release into water. Larval hatching occurs synchronously when the embryos are attached to a female, and the role of the female in this synchrony has been investigated. Clusters of embryos (200-2000 berries in each cluster) were detached from ovigerous females, and their hatching was compared with that of embryos attached to the females. Of the detached embryos in a cluster, either all hatched, or none hatched. A remarkable feature was that the success of hatching of these detached eggs depended upon the time of hatching of the eggs still attached to the female. Clusters of embryos that were detached from the female within 48-49.5 h of the projected time of larval release all hatched successfully, and swimming zoeas appeared. But embryos that had been detached from the female for longer periods did not hatch at all, though they were obviously alive. These results suggest a hatching process different from the embryonic development process. The female may trigger this process. In addition, detached eggs hatched later than eggs attached to the female, and their hatching was less synchronized. These observations suggest that the female not only initiates hatching, but also enhances the synchrony of hatching.

Winter moth on Sitka spruce: synchrony of egg hatch and budburst, and its effect on larval survival

Winter moth on Sitka spruce: synchrony of egg hatch and budburst, and its effect on larval survival

Effects of sibling contact on hatch timing in an asynchronously hatching bird

Previous laboratory studies have shown that embryonic acoustic cues enable some precocial birds to effect tight within-brood hatching synchrony. Embryos of these species therefore can exert partial control over their own hatch timing. In many other avian taxa, substantial asynchrony characterizes hatching. Hatching asynchrony traditionally has been interpreted as being controlled purely by parents. Yet because asynchrony often influences the outcome of subsequent nestling competitions, offspring control over hatch timing could be beneficial, particularly for the youngest brood members. To explore whether chicks of the asynchronously hatching glaucous-winged gull, Larus glaucescens, modify their hatch timing in response to sibling priximity, laboratory and field experiments were performed in which physical contact with sibling eggs was manipulated. As in earlier studies of precocial species, a clear effect was found under laboratory conditions: sibling eggs incubated in contact with each other had significantly shorter hatching spreads than those spaced just 10 cm apart. Under field conditions, by contrast, there was no effect: sibling eggs incubated in separate nests (with two plaster companions each) hatched with the same spread as siblings sharing a common nest. Thus, in this species, the synchronization effect of sibling contact is apparently restricted to the laboratory context. With artificial incubation, eggs in physical contact may receive sufficient stimulation (from siblings) to hatch on schedule, but those separated by even a few centimetres experience retarded hatch, perhaps as a result of acoustic deprivation. In the field, however, levels of stimulation above some threshold may be readily available (from parents, colony milieu and other ambient sources), thereby permitting eggs without siblings to hatch at the ‘normal’ time.

Patterns of metabolism in embryonic reptiles

VdotO2 of eggs of the turtleEmydura macquarii, the crocodilianAlligator mississipiensis, and the tuataraSphenodon punctatus, were measured throughout incubation.E. macquarii andA. mississipiensis, species in which hatching synchrony may be important, show a decline inVdotO2 prior to hatching (‘peaked’ pattern). This is similar to the pattern shown by ratite birds, where the decline period may be variable and facilitates hatching synchrony. The same interpretation is used here for reptiles. Hatching synchrony seems unimportant inS. puntatus, no decline inVdotO2 is observed, and the pattern ofVdotO2 is similar to that shown by most precocial birds. Developmental asynchrony in reptilian nests,e.g., E. macquarii, probably results from temperature differences within the nest. Turtles with nests that are unlikely to experience developmental asynchrony, show truncation of the ‘peaked’ pattern, similar to the usual avian precocial pattern, or even extreme truncation approaching that of altricial birds. A pattern of ontogeneticVdotO2 in snakes (which have precocious young) similar to that in birds with altricial young may indicate a basic developmental differences in snakes.

Breeding Synchrony in the Lesser Snow Goose (Anser caerulescens caerulescens). I. Genetic and Environmental Components of Hatch Date Variability and their Effects on Hatch Synchrony

Breeding Synchrony in the Lesser Snow Goose (Anser caerulescens caerulescens). I. Genetic and Environmental Components of Hatch Date Variability and their Effects on Hatch Synchrony

Variations in measurements among white pelican eggs and their use as a hatch date predictor

Incubated bird eggs tend to lose weight linearly, and it is therefore possible to predict hatch dates from egg measurements taken during incubation. From 30 white pelican eggs measured in the laboratory, we found that egg volume (V) was estimated by V = 0.500 LB2 (L = length, B = maximum width). Specific gravity (SG) was then obtained as W/V (W = weight in air). A regression line of SG against days of incubation based on values for naturally incubated eggs was used to predict hatch dates for additional samples of 10 eggs from each of 55 subcolonies on five islands in Manitoba in 1978. Mean SG of 21 freshly laid eggs was 1.1009 ± 0.0033 g∙cm−3. The regression line for naturally incubated eggs was SG = 1.1081 g∙cm−3 – (0.0042 g∙cm−3∙egg−1∙day−1∙days). Actual hatch dates of 17 subcolonies were strongly correlated with predicted dates (r = 0.95). Hatch synchrony was independent of subcolony size. Mean error for subcolony predictions was 0.4 days, but was 2.8 days for individual eggs.Only width and consequently volume differed significantly among the colonies. Within subcolonies, variability in linear dimensions was mainly due to interclutch differences.Observations of vocalizations and pipping of eggs during visits are also useful for predicting hatch dates.

Contribution to the Life History and Dynamics of the Pine Needle Scale, Phenacaspis pinifoliae,1 in Central New York2

Mugho, Scots, and red pine were sampled intensively to study the population dynamics of Phenacaspis pinifoliae (Fitch). Change in population intensity in 1 year (2 generations) ranged from a decrease of 50% on 1 red pine to a 3- to 5-fold increase on 2 Scots pines and a 4- to 20-fold increase on 2 Mugho pines. Survival of scales in the spring and summer generations was strikingly different, spring crawler survival being much lower than in summer. Hatch synchrony and weather explain this difference. Host species also was an important factor in spring scale survival. Populations increased markedly on Mugho pine, remained static on Scots pine, and crashed on red pine in the spring of 1969. Survival of summer scales was not different on different pine species. Chilocorus stigma (Say) (Coleoptera: Coccinellidae) consumed many scales in all stages of development and contributed to scale population decline. But this beetle was not important in the dynamics of all scale populations that were studied. One eulophid parasite, Prospaltella bella Gahan, was a variable and important scale-mortality factor. Parasitized female scales failed to oviposit, and percent parasitism increased as scale density increased. Though parasites and predators were associated with all scale populations studied, their impact was not significant until after the economic injury level was reached.

On the hatching of Nematodirus battus, with some remarks on N. filicollis

1. The hatching of N. battus under laboratory conditions was investigated. A high hatch of ripe eggs was obtained on exposure to constant temperatures in the approximate range 8–15° C., and very little hatching took place at temperatures outside this range.2. These, and other published results can be explained in terms of a hypothesis transferred from the study of the breaking of insect diapause. This hypothesis supposes that two processes underly the completion of hatching—a cold process with low temperature optimum and a warm process with a higher temperature optimum and which can only proceed as the cold process is completed.3. It is not easy to apply these findings directly to field events, but the attempt to do so leads to the suggestion that the apparent synchrony of hatching and the presence of susceptible lamb hosts in the north-east of the British Isles may be partly fortuitous, and that in slightly different climatic circumstances many eggs might hatch in the autumn or during the winter.I wish to thank Mr A. V. Cunningham of Threepwood, Galashiels, and Mr J. M. M. Cunningham of the Edinburgh School of Agriculture for their generous help in making sampling of their flocks possible, and Dr J. T. Stamp for advice on the presentation of this paper.