Eggs Of Similar Size Research Articles

Effect of water temperature on egg incubation time and quality of newly hatched larvae of northern pike (Esox lucius L., 1758)

This study examined the effect of temperature on egg incubation, survival of eggs during embryonic development and quality of newly hatched larvae of northern pike (Esox lucius L.) under laboratory conditions. Eggs of similar size (diameter 2.7 ± 0.16 mm and weight 6.11 ± 0.35 mg) from five females were incubated at 3, 6, 10, 14, and 18°C (groups A, B, C, D, and E, respectively). The lowest fertilization (FR) and hatching rates (HR) were observed in larvae incubated in group A, 44.6 ± 3.2% and 18.26 ± 2.25%, respectively. The highest FR and HR were found in group B (FR, 71.3 ± 4.3%; HR, 56.2 ± 3.21%) and C (FR, 65.6 ± 3.1%; HR, 65.5 ± 5.41%). Time of incubation period varied from 38 ± 0.33 days (120 ± 1.03°d) when 5% larvae were hatched to 46 ± 0.42 days (144 ± 1.31°d) when 95% larvae were hatched in group A and 2.5 ± 0.08 days (44.67 ± 1.42°d) when 5% larvae were hatched to 3.42 ± 0.06 days (61.11 ± 1.07°d) when 95% larvae were hatched in group E. Larvae from groups A, D, and E were characterized by the lowest values of variables such as resistance to osmotic stress after 90 min of exposure of saline solution (OS = 54 ± 3–76 ± 3%), frequency of normally developed larvae (FNL = 23.8 ± 4.14–87. 1 ± 2.42%), and yolk sac volume (YsV = 3.41 ± 0.44–3.89 ± 0.45 μl3). The highest quality larvae were recorded in groups B and C: OS = 92 ± 3% and 80 ± 4%, FNL = 89.7 ± 3.62% and 93.8 ± 3.17, YsV = 3.3 ± 0.66 μl3 and 3.04 ± 0.42 μl3). Fertilization and hatching rates and quality of larvae showed optimal temperature for successful egg incubation and production of high quality larvae to be 6 to 10°C. Relationship of ontogenic rate to temperature showed development of the pike embryo to be hypothetically stopped at 3.3°C.

Older female little penguins Eudyptula minor adjust nutrient allocations to both eggs

How individuals allocate resources to reproduction is a fundamental concept in animal life history theory. While it is crucial to quantify the relative allocation of somatic reserves to reproduction by avian females; variation at the individual and intra-clutch level has generally been neglected. We investigated nutrient allocation to eggs of little penguins (Eudyptula minor, Forster, 1781) using automated body-mass recording and natural δ13C and δ15N values for plasma and blood cells of incubating females, and down feathers of their chicks. Further, we evaluated the role of female age (a proxy for experience or senescence) and condition as drivers of individual strategies within this population. Little penguins increased their body masses during a short period prior the onset of reproduction, suggesting that they were accumulating resources to cope with reproductive requirements. Estimated endogenous contribution to eggs was relatively low (~20%), and female age was revealed as a major factor modulating individual variations in resource allocation strategies. Older females accumulated larger amounts of reserves before laying (up to 40% body mass increases) and relied more on endogenous resources (up to 45%) for clutch production than younger females. Our findings suggest that females were able to adjust their endogenous investment between their two chicks, with somatic reserve inputs to heavier siblings showing a bimodal distribution (mean±SD; 16.7±5.9% and 36.5±4.4%) that contrasted with the unimodal distribution observed for lighter siblings (17.8±8.7%). Here, we provide evidence pointing to age and age-related changes as major factors modulating individual decisions on the amount of somatic reserves allocated to eggs. We additionally identified two distinct allocation strategies at the intra-clutch level that may favour siblings with greater chances to fledge, revealing a novel clutch size reduction strategy in seabirds that produce two eggs of similar size but involving a differential nutrient investment in eggs.

Reproductive compensation in broad-nosed pipefish females

The differential allocation hypothesis assumes that animals should weigh costs and benefits of investing into reproduction with a current mate against the expected quality of future mates, and predicts that they should invest more into reproduction when pairing with a high-quality mate. In the broad-nosed pipefish (Syngnathus typhle), males care for the embryos in a brood pouch and females compete for access to male mating partners. Both sexes prefer mating with large partners. In the present study, we show that the same female provides both large and small mating partners with eggs of similar size, weight and lipid content when mated to two males in succession. Importantly, however, eggs provided to small males (less preferred) had higher egg protein content (11% more) than those provided to large males (preferred). Thus, contrary to the differential allocation hypothesis, eggs did not contain more resources when females mated with a larger male. Instead, the pattern observed in our results is consistent with a compensatory reproductive strategy.

Effects of Eggshell Temperature and Oxygen Concentration on Embryo Growth and Metabolism During Incubation

Embryo development and heat production (HP) were studied in eggs of similar size (60 to 65 g) that were incubated at normal (37.8°C) or high (38.9°C) eggshell temperature (EST) and exposed to low (17%), normal (21%), or high (25%) O2 concentration from d 9 through 19. High EST initially increased HP, but gradually O2 became more important for HP than EST. Finally,HP was highest for the combination of high EST with high O2 and lowest for the combination of high EST with low O2. High EST decreased hatch time, BW, yolk free BW, and relative heart weight. The EST had no effect on residual yolk weight, chick length, or relative liver weight. Increased O2 increased yolk free BW and chick length and decreased residual yolk weight at hatch. No interactions between EST and O2 were observed with regard to embryo development and hatchling characteristics. If embryo development is reflected by HP, it can be concluded that high EST primarily increased embryonic development until the second week of incubation. During the third week of incubation, O2 had a greater effect in determining embryo development than EST.

How to hatch from an egg of great structural strength. A study of the Common Cuckoo

Brood parasitism represents a unique mode of avian reproduction that requires a number of adaptations. For example, to reduce chances of puncture ejection of their eggs by small hosts, brood parasites may have been selected for laying eggs of unusually great structural strength. However, great structural strength of eggshells should hinder hatching. The goals of our study were to establish if chicks of the Common Cuckoo Cuculus canorus have more difficulty with hatching out of their strong eggs than chicks of species with eggs of similar size, and whether they possess any mechanisms facilitating hatching. To achieve these goals, we compared hatching pattern and selected body characteristics of chicks of the Common Cuckoo with those of another altricial species with eggs of a similar size, the Great Reed Warbler Acrocephalus arundinaceus. Although the rate of pecking was similar in the two species, the Common Cuckoo chicks started pecking earlier in relation to their emergence and consequently required more time and a greater cumulative number of pecks for breaking open their eggs than did young Great Reed Warblers. The two species also differed with respect to the pattern of opening their shells; in contrast to the warbler chicks, which enlarged the original pip circularly, the cuckoo chicks opened the egg by systematically creating a long narrow slit until they emerged. Finally, our study of hatched young revealed several differences; the Cuckoo hatchlings were significantly heavier, had a longer forearm, and their egg tooth was located significantly farther from the tip of the beak. The edge used for cutting through the shell was also significantly longer than that of hatchling Great Reed Warblers. To conclude, our data suggest that hatching is more difficult for a Cuckoo than for a Great Reed Warbler and that Cuckoos possess several mechanisms to overcome the problems of hatching from a structurally strong egg.

Life History Variation in a Population of the Australian Frog Ranidella signifera: Egg Size and Early Development

We examined the proposition that, in a population, large egg size confers greater fitness than small egg size. Within clutches of the frog Ranidella signifera from near Bridgewater, South Australia, larger eggs tended to hatch into larger tadpoles, but there was no consistent relationship between egg size and development time to hatching and to first feeding. Among clutches, those with larger mean egg size tended to have faster development times and to hatch into larger tadpoles. However, there was also a significant effect of clutch on these two parameters which was as great or greater than the effect of egg size. That is, two eggs of similar size could develop at quite different rates, and have quite different sizes as early stage tadpoles, if they came from different clutches. In certain environments, the fitness of free living tadpoles may be directly related to their size. Our data show that, after development to independent feeding, the largest tadpole need not have arisen from the largest egg.

Variation in Egg Size of the Hooded Crow Corvus corone cornix

Variation in egg size of a population of the Hooded Crow Corvus corone cornix was studied at Trondheim in Central Norway, during the period 1979-1982. No significant differences in egg volume were found neither from one year to another nor within different sized clutches, nor with laying date. The hatchability of small sized eggs and of eggs laid late in the laying order was lower than that of large sized eggs and of eggs laid early in the laying order. For all clutch sizes, a decrease in egg volume was found with increasing order of laying. All the last laid eggs (n = 39) had a smaller volume than the mean for the same clutch. The relative size of the first laid eggs (deviation from the mean for the same clutch) decreased with increasing clutch size. A significant positive correlation existed between the body weight of the hatchling and the volume of the egg from which it hatched. Both male and female hatchlings hatched from eggs of similar size, and had roughly the same body weights at hatching.

Why Some Birds Take so Long to Hatch

In general, incubation periods of bird eggs are positively correlated with egg weights. The eggs of some birds take much longer to hatch than expected. Highly variable and long incubation periods are explained using fork-tailed storm petrels as an example. Their eggs take two to three times as long to hatch as eggs of similar size. Egg neglect causes the extreme variability in incubation periods within a species. Low incubation temperatures prolong incubation, but long incubation periods may also be a result of selective forces that favor hatching well-developed young that can be attended infrequently. Past terminology has obscured the importance of the relationship between incubation periods and the maturity of chicks at hatching. Selection has produced a continuum between cheap eggs and expensive care for the relatively helpless (altricial) young or expensive eggs and inexpensive care for the relatively independent (precocial) young. The distant foraging habits of the Procellariiformes have favored independent hatchlings.

Reproduction , Spawning and Development of the Starfish Patiriella exigua (Lamarck) (Asteroidea : Asterinidae) and Some Comparisons with P. calcar (Lamarck)

P. exigua adults are mature throughout the year. The species can breed in any month of the year, though spawning is most active in the late winter and spring. P. calcar has a definite breeding season in the late spring and summer. P. exigua lays an egg mass through oral gonopores. The 400-�m eggs develop directly, through a yolky brachiolaria stage to a juvenile star, before leaving the egg mass at 22-23 days. P. calcar, with eggs of similar size laid through oral gonopores, has a planktonic lecithotrophic larva. The development of P. exigua is compared with that of other yolky asteroid embryos. Modes of development in the genus Patiriella are discussed.

Observations on the embryonic development of some deep-living decapod crustaceans, with particular reference to species of Acanthephyra

Eggs of meso- and bathypelagic decapod crustaceans were removed from gravid females and allowed to develop in vitro. The time course of embryonic development, as indicated by the appearance of certain morphological and physiological features, was determined for most species at a constant temperature of 12°C. The embryonic period, and the time between the appearance of certain key features such as naupliar and compound eyes and heartbeats, showed little variation in any one species. Significant differences were observed in the development times of different species. In general, species with large eggs have a longer embryonic period than those with small eggs, but there also variations between species with eggs of similar size. During the development of Acanthephyra eggs there is an approximate doubling of the egg volume, correlated with a decrease in egg density and an increase in the water content. The increase in the water content and egg volume is similar to that of other decapod eggs. It is concluded that those species with small eggs could have several broods in 1 year, whereas those species with large eggs are likely to be restricted to one, or in some cases possibly two, broods.