Variation In Egg Volume Research Articles

Rejection of Conspecific Eggs Associated with the Appearance of Eggs, in the Azure-Winged Magpie Cyanopica cyanus in Korea

Avian brood parasitism is a reproductive strategy in which a parasitic species lays its eggs in the nests of a host. In response to parasitism, hosts have evolved various defence strategies. One of the host defences against intraspecific and interspecific brood parasitism is to distinguish parasitic eggs based on intraclutch variation in egg appearance. Hosts can improve their ability to discriminate parasitic eggs by lowering the degree of their intraclutch variation in egg appearance. Therefore, intraclutch variation may affect the egg rejection behaviour of hosts. In this study, we conducted experiments to study egg recognition and rejection behavior for mimetic eggs in Azure-winged Magpies Cyanopica cyanus in Korea. We also investigated the level of variation in egg appearance (egg color, spottiness and volume) in order to explore whether the degree of this variation is associated with the rejection decision. We found that there were no differences in egg coloration or spottiness between the rejecter and accepter. However, we found that intraclutch egg volume variation in rejecters was significantly lower than that in accepters, indicating that the Azure-winged Magpie is likely to recognize its own eggs by lowering its intraclutch variation in egg volume as a defensive strategy against brood parasitism. This study suggests that the Azure-winged Magpie use not the differences in egg coloration but egg volume to discriminate and reject closely mimetic conspecific eggs.

The Role of Intra-Clutch Variation of Magpie Clutches in Foreign Egg Rejection Depends on the Egg Trait Considered

The existence of a coevolutionary process between avian brood parasites and their hosts predicts a lower intra-clutch variation in egg appearance of host eggs among rejecters as this would favor egg discrimination of parasite eggs by hosts once parasitic egg mimicry had evolved. So far empirical tests of this prediction have ignored the fact that different aspects of host egg phenotypes may differ in the relative role of environmental vs. genetic determination, and hence that the role of intra-clutch variation in egg rejection within a population cannot be invariant. Here, we estimated whether the intra-clutch variation in several aspects of host eggshell features is consistently associated to rejection of parasitic foreign eggs across years in a magpie host population parasitized by great spotted cuckoos. We innovatively estimated spottiness by means of the fractal dimension of eggs, which considers the homogeneity of spot pattern complexity in eggshells. Our results show that low intra-clutch variation in the blue-green coloration at the middle area of the eggs associated with a high chance of rejection, but only in one of the 3 years we conducted the study. In addition, females that rejected foreign eggs presented more homogenous spot patterns in their clutches as estimated by their fractal dimension than females that accepted experimental eggs, independently of the year of study. Finally, intra-clutch variation in egg volume of host eggs was not associated to rejection. Analyses at the individual level revealed that the relative role of genetic vs. environmental factors that determine egg phenotype would be feature-specific in magpies, females having a characteristic spottiness, but not color or volume, pattern. Our work stresses the importance of considering a holistic approach including several aspects of variation in host egg phenotype (size, color, and homogeneity of spot pattern), as some aspects might be more susceptible to selection through egg rejection than others, presumably because they are less influenced by variation in the environmental conditions. Moreover, our study highlights the importance of replication in studies on the adaptive value of host traits in egg rejection.

Insect egg size and shape evolve with ecology but not developmental rate.

Over the course of evolution, organism size has diversified markedly. Changes in size are thought to have occurred because of developmental, morphological and/or ecological pressures. To perform phylogenetic tests of the potential effects of these pressures, here we generated a dataset of more than ten thousand descriptions of insect eggs, and combined these with genetic and life-history datasets. We show that, across eight orders of magnitude of variation in egg volume, the relationship between size and shape itself evolves, such that previously predicted global patterns of scaling do not adequately explain the diversity in egg shapes. We show that eggsize is not correlated with developmental rate and that, for many insects, egg size is not correlated with adult body size. Instead, we find that the evolution of parasitoidism and aquatic oviposition help to explain the diversification in the size and shape of insect eggs. Our study suggests that where eggs are laid, rather than universal allometric constants, underlies the evolution of insect egg size and shape.

Variability in egg and jelly-coat size and their contribution to target size for spermatozoa: a review for the Echinodermata

Fertilisation and development in broadcast-spawning marine invertebrates depends on the ability of the egg to attract spermatozoa and provision progeny. Echinoderm eggs have a jelly coat that facilitates sperm–egg collisions. We investigated variation in egg volume and target area for spermatozoa provided by the jelly coat within and between three sea urchin species (Heliocidaris erythrogramma, Heliocidaris tuberculata, Centrostephanus rodgersii), as well as across 22 echinoderm species for which data are available. Egg and jelly-coat size varied within spawns of individual females, between females of a species and between species. The jelly coat increased egg target area by 125–489% for echinoids with planktotrophic development. In general, planktotrophic echinoids (n=16) with larger eggs had thicker jelly coats, as did H. tuberculata females with larger eggs. Variability in egg and jelly-coat size within a species indicates that these traits are prone to maternal effects and may be influenced by factors such as sperm environment and offspring fitness that drive selection on egg investment. The greater variability in jelly-coat size compared with that of the egg has a large potential to affect fertilisation and should be considered in models of fertilisation kinetics. Egg size alone cannot be used as a metric to infer target size for spermatozoa.

Late snowmelt can result in smaller eggs in Arctic shorebirds

Migratory birds often travel long distances between non-breeding and breeding areas. The suitability of weather and foraging conditions they experience upon arrival at their breeding grounds is an essential component explaining the timing and success of reproduction. Climate change has been identified as a major contributor to “mismatches” in resource phenology and timing of reproduction in animal populations. Climate models project a disproportionate degree of warming at high latitudes, thus the potential for marked temperature-related mismatches in polar regions. Timing of breeding for many Arctic species is also governed by snowmelt. Current models project a general increase in winter precipitation for the Arctic, which can lead to years of delayed snowmelt despite the overall warming trend. This delayed snowmelt could affect phenology, or the availability of resources for egg production. We use an unplanned contrast in dates of snowmelt during a two year research program in the Canadian Arctic to explore the hypothesis that, for Arctic-breeding shorebirds with fixed clutch sizes and an income-breeding strategy, adjustment of reproductive effort to delayed snowmelt could result in a reduced egg size. We compared egg volume in clutches of several shorebird species in the two consecutive years. We found significant variation in egg volume between years, with eggs approximately 5% smaller in the year of late snowmelt, suggesting that shorebirds faced with adverse conditions upon arrival to their breeding grounds can respond by decreasing egg-size. A larger sample of years, sites and shorebird species would help to clarify the generality of this response.

Spatial Variation in Clutch Size and Egg Size Within a Colony of Whiskered Terns (Chlidonias hybrida)

Abstract Egg and clutch size of Whiskered Terns (Chlidonias hybrida) in relation to their location within the colony were investigated at Jeziorsko Reservoir, central Poland. All nests (n = 125) in the colony were individually marked and mapped using a Global Positioning System. Four nest clusters were distinguished within the colony based on the patchy distribution of floating vegetation which delineated potential nesting areas. Early breeding Whiskered Terns nested in more central and denser parts of nest clusters and late breeders nested in more peripheral zones of the clusters (trend analysis: F = 20.47, df = 1, P < 0.001). Pairs which nested closer to the centers of clusters had larger clutch sizes (trend analysis: F = 5.70, df = 1, P = 0.019), but there was no relationship between clutch size and distance to the colony center (F = 0.38, df = 2, P = 0.69). Edge clutches had higher coefficient of variation in egg volume in comparison to more central clutches (trend analysis: F = 5....

Temporal covariation of egg volume and breeding conditions in the Common Kestrel (Falco tinnunculus) in the Mediterranean region

Most studies on variation in egg size in the Common Kestrel (Falco tinnunculus) have been carried out in central and northern Europe, whereas less is known about populations in the Mediterranean basin. We investigated the variation in egg volume in a Mediterranean population of Common Kestrel over a six-year period in relation to clutch size, breeding time, hatching success, and weather conditions. Eggs were generally bigger in larger clutches, and egg volume tended to decrease over the breeding season, but these patterns were not consistent among breeding seasons. Egg volume did not significantly vary in relation to weather conditions and did not predict hatching or fledging success. This study showed that (a) the patterns of covariation among laying date, clutch size and egg volume varied inconsistently over multiple years, and (b) egg volume poorly predicted the probabilities of hatching and fledging in the studied population.

Calculating egg volume when shape differs: when are equations appropriate?

ABSTRACT Egg volume is often calculated from length and breadth, assuming little variation in egg shape within species. However, egg shape may vary among females, over time, or within clutches. If this variation is not predictable, volume should be estimated using another method. For example, in some species, egg shape changes consistently with laying order and volume can be estimated using laying-order specific equations. We measured the length, breadth, volume, and mass of 249 Magellanic Penguin (Spheniscus magellanicus) eggs and regressed volume on length and breadth for first and second eggs separately. Differences between measured and calculated volume averaged <1% for both eggs. Using linear measurements, we calculated egg volume for 7085 clutches from 1983 to 2006. First and second eggs had similar calculated volumes (P > 0.05) in 19 of 24 yr; when they differed, the second egg was larger. In contrast, using single equations typically employed to compute egg volume, we erroneously concluded that first eggs were usually (20 of 24 yr) significantly larger than second eggs. Our regression equations should be applicable to other Spheniscus penguins because ratios of elongation coefficients (length divided by breadth) of first and second eggs are similar among these species. In other species of birds where egg shape changes with laying order, the volume of a sample of eggs should be measured to develop regression equations specific to the species and laying order. Slight variation in egg volume can have important evolutionary and ecological implications that would be erroneously interpreted without field tests to measure volume. Usualmente el volumen del huevo se calcula basado en el largo y ancho, asumiendo poca variación en la forma del huevo dentro de la especie. Sin embargo, la forma del huevo puede variar entre hembras, a través del tiempo o dentro de la nidada. Si la variación no es predecible, el volumen debería ser estimado con otro método. En algunas especies de aves la forma del huevo cambia consistentemente con el orden de la puesta y el volumen puede ser estimado usando una ecuación específica para el orden de la puesta. Medimos el largo, ancho, volumen y masa en 249 huevos de Spheniscus magellanicus y realizamos una regresión del volumen con el largo y ancho para el primer y segundo huevo por separado. Diferencias entre el volumen medido y calculado promediaron <1% para los dos huevos. Usando medidas lineares, calculamos el volumen del huevo para 7085 nidadas desde 1983 hasta el 2006. El primer y segundo huevo tuvieron volúmenes calculados similares (P > 0.05) en 19 de los 24 años; cuando ocurrieron diferencias el segundo huevo fue más grande. Utilizando una sola ecuación de la literatura para calcular el volumen del huevo obtuvimos conclusiones erróneas en donde el primer huevo (20 de 24 años) fue usualmente significativamente más grande que el segundo huevo. Debido a que las proporciones de los coeficientes de elongación (largo dividido por el ancho) del primer y segundo huevo fueron similares, nuestras ecuacións de la regresión debe ser aplicable a otro pingüinos del genero Spheniscus. En otras especies de aves en donde la forma de los huevos cambian con el orden de la puesta, el volumen de varios huevos debe ser medido para poder obtener una ecuación específica por medio de una regresión, para las especies y el orden de la puesta. Una pequeña variación en el volumen del huevo puede tener implicaciones ecológicas y evolutivas importantes, que pueden ser interpretadas de manera errónea sin medidas previas en el campo del volumen.

Seasonal change in egg-volume variation within a clutch in the Bull-headed Shrike, Lanius bucephalus

I studied the seasonal change in egg volume in Bull-headed Shrikes, Lanius bucephalus, to explore the importance of egg-volume variation within a clutch. The mean egg volume did not change over a season; however, the coefficient of variation in egg volume in six-egg clutches significantly increased in 1994 and 1995 but did not change in 1996. Peaks in arthropod biomass occurred early in the breeding seasons in 1994 and 1995, but late in the season in 1996. Higher food availability was related to a reduction in variation in egg volume within a clutch. A significant difference in egg volume was found within six-egg clutches, and the first egg was the smallest. Nestlings that hatched from small eggs early in the hatching order suffered lower mortality rates than nestlings that hatched from large eggs laid late in the hatching order. The duration of time between settlement of a female in a male territory and clutch initiation decreased with date. Intraclutch variation in egg volume may be caused by a trade-off between the time to develop an egg and the volume of the first egg within a clutch. Because eggs that hatch first do not need to be large for the hatchling to survive, the Bull-headed Shrikes may advance the clutch-initiation date at the cost of reducing the volume of the first egg.

Maternal Size Determines Clutch Mass, whereas Breeding Timing Influences Clutch and Egg Sizes in the Tropical Lizard,Calotes versicolor(Agamidae)

We studied the correlations between body size parameters (SVL and body condition) and clutch parameters (size and mass) as well as between clutch size and egg parameters (mass, volume, length, and width) in a population of Calotes versicolor, a multiclutched lizard that breeds from May to October in southern India. We also analyzed the relationships between early, mid, and late clutches among lizards of different SVL groups. Clutch size and SVL did not vary among years. Clutch size and clutch mass were positively correlated with body size. Egg mass and volume were negatively correlated with clutch size. Clutch size was larger in early and midbreeders than in late breeders. Interestingly, the eggs of late clutches were larger than those of early breeders. A trade-off between clutch size and egg volume was always obvious. The width of eggs did not vary with SVL or clutch timing, perhaps because the width of the pelvic aperture remained virtually constant after maturity. Thus, variation in egg volume in C. versicolor is because of variation in egg length. A wide range of variation in egg volume even among lizards with similar SVL suggests that there is no optimization of egg volume in this species. In contrast, the clutch mass of early, mid, and late clutches did not vary among lizards of comparable SVL. Apparently, SVL acts as a prime factor determining clutch mass in C. versicolor, and the latter is optimized by natural selection.

Early Life-History Parameters of Japanese Medaka (Oryzias latipes)

Abstract The cause of size differences among developing fish is often not clear. We examined variability in egg size and in incubation time to determine whether either influenced hatching size or initial rates of growth in Japanese Medaka (Oryzias latipes). We also tested the prediction that larger females should produce heavier and/or more eggs. Our results indicated that larger females produce more, but not larger, eggs. Both egg volume and incubation time were positively, although weakly, correlated with the size of fry at hatching. Within-female variation accounted for substantially more variation in both egg size (69.9%) and hatching lengths of fry (79.3%) than did variation among females. Variation in egg volume, hatching size, and size at three-days posthatching (in the absence of feeding) decreased, as indicated by coefficients of variation for each (11.6, 4.8, 4.4). It is unknown whether slight differences in hatching size may contribute to subsequent variation in size when fry must compete for a...

ESTABLISHMENT AND PERSISTENCE OF MASS HIERARCHIES IN BROODS OF THE BROWN PELICAN

I investigated the roles of intraclutch variation in egg volume and hatching asynchrony in the establishment of mass hierarchies in broods of the Brown Pelican (Pelecanus occidentalis). The second egg averaged 2.6% larger than the first and 1.9% larger than the third. In unmanipulated control broods, first eggs hatched an average of 25 h before second eggs, which hatched 40 h before third eggs. On the day the last egg hatched, first chicks averaged 16% heavier than second chicks and 30% heavier than third chicks. Although chick mass at hatching was strongly correlated with egg volume, differences in mass within broods were almost entirely the result of hatching asynchrony. In broods in which I experimentally reduced hatching intervals, initial nestling mass differences were significantly smaller and strongly correlated with differences in egg volume but not with hatching asynchrony. Intrabrood mass differences remained lower in experimental than control broods throughout the first 2 weeks of the nestling period. Furthermore, mass ranks established at hatching were less likely to persist through this period in experimentally synchronized broods than in asynchronous controls. These results indicate that hatching asynchrony promotes the establishment of a more stable size hierarchy. However, the adaptive significance of nestling size hierarchies in Brown Pelicans remains unresolved.

Sources of Variation in Clutch Size, Egg Size and Clutch Completion Dates of Semipalmated Plovers in Churchill, Manitoba

Variation in clutch size, egg size and clutch completion dates was studied in a population of Semipalmated Plovers (Charadrius semipalmatus) over 5 summers in Churchill, Manitoba. Clutch size variation was greatest in 1992, a year of unusually low summer temperatures, with almost 25% of clutches containing less than four eggs. More eggs were left unhatched in the nest in 1992 than in any other year. Clutch completion dates were negatively correlated with the average temperature during the pre-laying period. Synchrony of nesting was greatest in 1994, the warmest year. Egg volume and mass were not reduced as a result of the cold summer, and the variation in egg volume and mass attributable to differences among females was similar and significant in all years. Repeatabilities of all egg measurements were high. Egg volume was moderately correlated with female body mass but not with female wing length nor female condition (mass/wing length), a result consistent with that found in other shorebirds. Egg size did not vary consistently with laying order, suggesting strong selection for uniformity in egg size within a clutch.

Intraclutch Variation in Egg Volume of Great Crested Grebes

Journal Article Intraclutch Variation in Egg Volume of Great Crested Grebes Get access Keld Henriksen Keld Henriksen Kervej 17, DK-8230 Abyhoj, Denmark Search for other works by this author on: Oxford Academic Google Scholar The Condor, Volume 97, Issue 3, 1 August 1995, Pages 826–828, https://doi.org/10.2307/1369194 Published: 01 August 1995 Article history Received: 27 October 1994 Accepted: 31 January 1995 Published: 01 August 1995

Avian Egg Morphometrics - Allometric Models of Egg Volume, Clutch Volume and Shape

This paper describes three comprehensive new models of the allometric relationships between egg volume, clutch volume and shape, and body weight. Mean egg dimensions, clutch sizes and adult body weights were obtained for 326 species, mainly of four bird types: raptors (including owls), shorebirds, frogmouths (including nightjars), and storks (including the New World vultures). These are groups in which there is a wide range of body sizes and of sexual dimorphism in body size (in direction and degree). Female body weight alone accounted for 92% of the variation in egg volume. Sexual dimorphism in body size, phylogenetic relationship, and clutch size were significant contributors to the model of egg volume; their addition increased the explained variance to over 98%. The model was curvilinear (quadratic) in form, rather than linear as assumed in previous models. Larger species laid smaller eggs than expected under a simple power function. For the fitted model, within bird types, generic groupings had parallel curvilinear slopes but differing intercepts. Between bird types, the slopes differed. Clutch volume was scaled to body weight; all the bird types had a common slope, which was curvilinear. Body weight and dimorphism accounted for 89.5% of the variation in clutch volume. For all bird types, eggs became proportionally longer in shape as body weight increased, according to a simple power law. The relevance of these relationships to hypotheses on the evolution and adaptive significance of sexual dimorphism and to the trade-off between egg size and clutch size is discussed briefly.

Temporal and spatial variation in egg size of 13 Panamanian echinoids

Though egg size of marine invertebrates has received a great deal of theoretical attention, and though sea urchin eggs have been studied for nearly a century, practically no data on intraspecific variation of echinoid egg size exist. This study examines temporal variation in egg size of 10 species of regular and three species of irregular echinoids from either side of the Isthmus of Panama. Data on spatial variation in egg volume are also presented for eight of these species. In all species mean size of eggs from different females collected from the same locality on the same day were significantly different. Daily (within-month) variation in egg size was significant in three out of the five species for which sufficiently large samples were collected: Eucidaris tribuloides (Lamarck), Diadema antillarum Philippi, and Lytechinus variegatus (Lamarck). No significant differences between daily means of egg volume were evident in D. mexicanum A. Agassiz and in Echinometra viridis A. Agassiz. Monthly means of egg volume were significantly different in seven out of the 13 species studied: Lytechinus variegatus, L. williamsi Chesher, Tripneustes ventricosus (Lamarck), Echinometra viridis, E. vanbrunti A. Agassiz, Clypeaster rosaceus (Linnaeus), and C. subdepressus (Gray). Between-year variation was also significant in all of these species, except Lytechinus variegatus. All Caribbean species with significant monthly variation show a decline in egg size after September, but no obvious environmental fluctuation can be linked to this change. Echinometra lucunter (Linnaeus) showed no significant variation between months of the same year, but exhibited differences between years. No significant monthly or annual variation was observed in Eucidaris tribuloides, E. thouarsi (Valenciennes), Diadema antillarum, D. mexicanum, or Leodia sexiesperforata (Leske). When temporal variation at each locality was taken into account, only one species out of eight, Clypeaster subdepressus, showed spatial variation. Correlations between size of eggs collected at a particular time and the intensity of spawning by the population at that time were generally not significant, suggesting that size of mature eggs is not determined by reproductive state of the parental population. Correlations were also attempted (in three species of Echinometra) between egg size and body weight, gonadal content, and number of eggs carried by the mother. None of these variables was a good predictor of egg size. Only in E. viridis was there a significant correlation between egg size and gonadal content. Though its causes remain obscure, intraspecific variation in egg size found in these echinoids could be exploited to study the possible effects of this parameter on larval life history.