Mean Egg Mass Research Articles

Distinct Genomic Loci Underlie Quantitative Resistance to Meloidogyne enterolobii Galling and Reproduction in Citrullus amarus.

Meloidogyne enterolobii is a virulent species of root-knot nematode that threatens watermelon (Citrullus lanatus) production in the southeastern United States. There are no known sources of root-knot nematode resistance in cultivated C. lanatus. Specific genotypes of a wild watermelon relative, C. amarus, are resistant against M. incognita but the genetics that underly this resistance are still unknown and it is not clear that this same resistance will be effective against M. enterolobii. To identify and characterize new sources of resistance to M. enterolobii, we screened 108 diverse C. amarus lines alongside a susceptible C. lanatus cultivar (Charleston Gray) for resistance against M. enterolobii. Different C. amarus genotypes ranged from resistant to susceptible for the three resistance phenotypes measured; mean percent root system galled ranged from 10 to 73%, mean egg mass counts ranged from 0.3 to 64.5, and mean eggs per gram of root ranged from 326 to 146,160. We used each of these three resistance phenotypes combined with whole-genome resequencing data to conduct a genome-wide association scan that identified significant associations between M. enterolobii resistance and 11 single-nucleotide polymorphisms (SNPs) within the C. amarus genome. Interestingly, SNPs associated with reduced galling and egg masses were located within a single quantitative trait locus (QTL) on chromosome Ca03, while reductions in nematode eggs per gram of root were associated with separate QTL on chromosomes Ca04 and Ca08. The results of this study suggest that multiple genes are involved with M. enterolobii resistance in C. amarus and the SNPs identified will assist with efforts to breed for M. enterolobii resistance in watermelon.

Organic minerals, tributyrin, and blend of organic acids in the diet of commercial laying hens at the end of production

This study aimed to evaluate the responses in performance, egg quality, and health of internal organs of laying hens of Hisex White lineage. The birds were provided with diets supplemented with organic minerals (OM) + tributyrin, associated or not with a mixture of organic acids (benzoic formic, citric, and phosphoric), compared to a control treatment containing zinc bacitracin (28 ppm). In total, 160 laying hens of the commercial Hisex White lineage of 68 w and an average weight of 1.735 ± 0.025 kg were distributed in 40 experimental plots. The study employed a completely randomized design, with five treatments and eight replications/treatment. The experimental period was divided into seven production cycles of 21 days, totalling 147 experimental days. The variables analysed were egg production and loss, feed intake, mean egg weight, egg mass, feed conversion, and internal and external quality variables of eggs. At the end of the experimental period, the final weight of the birds was measured to evaluate the relative weight of liver and kidneys. No significant effect of the treatments on the productive performance and internal and external quality of the eggs was evident. The association of organic minerals with a mixture of organic acids and tributyrin did not influence the productive performance and internal and external quality of the shell of Hisex White laying hens in the period from 68 to 89 weeks of age.

Long‐term increase in female body condition and its effect on reproduction in two European red‐listed species, Common Pochard (Aythya ferina) and Tufted Duck (Aythya fuligula)

Body condition of breeding females is an important driver of an individual's fitness and the consequent dynamics of populations. Long‐term changes in female body condition are likely to be affected by recent shifts in climatic and environmental conditions that can result in changes to population demography. To help explain the drivers shaping body condition during the incubation period and its consequences for reproductive success, we examined the long‐term pattern in the body condition of breeding females of two declining sympatric diving duck species: Common Pochard Aythya ferina and Tufted Duck Aythya fuligula. We analysed the data obtained from 139 females of Common Pochard and 251 females of Tufted Duck breeding on fishponds in South Bohemia, Czechia, between 2004 and 2020. We calculated the body condition index of females during late incubation based on the residuals from the relationship between body mass and tarsus length and used the incubation stage as an additional predictor of body mass. Body condition of both species did not decline over the 17 years of the study. The effect of winter weather conditions (winter temperature), water transparency (a proxy for food availability) and reproductive investment on body condition was not confirmed. Female body condition positively affected mean egg mass and hatchability in both studied species, i.e. females in better body condition laid larger eggs and hatched eggs with a higher hatching probability. We conclude that the population declines of the studied species are probably not connected to decreasing body condition of breeding females, but other reasons such as change in breeding propensity or offspring survival and recruitment should be considered in future studies.

Effects of protease enzyme supplementation and varying levels of amino acid inclusion on productive performance, egg quality, and amino acid digestibility in laying hens from 30 to 50 weeks of age

An experiment was conducted to evaluate the effects of protease supplementation and reduced digestible amino acid (dAA)/ crude protein (CP) level on productive performance, AA digestibility, and egg quality parameters in Hy-Line W-36 laying hen from 30 to 50 wk of age. A total of 768 hens (12 replicates of 8 hens per treatment) were equally and randomly allocated into 8 experimental diets in a 4×2 factorial arrangement of dAA/CP level (100, 95, 90, and 85% of breeder recommendation) and protease (exclusion or inclusion). Protease was added at 60 g/metric ton of feed in the inclusion group. Hens were housed in raised-wire cages with a stocking density of 870 cm2/bird. The adequate (100%) diet was based on corn and soybean meal and formulated based on the digestible (d) Lys and dAAs (dMet, dThr, dTrp, dTSAA, dIle, and dVal) to meet 100% of the current management guide recommendation. Variations in dAA/CP (95, 90, and 85% diets) were accomplished by reducing the 100% dAA by 5, 10, and 15%, respectively. All diets were supplemented with phytase at 500 phytase units (FTU)/kg. Data were analyzed using PROC GLM of SAS 9.4. There was a main effect of dAA/CP level on 85% diet where it had a lower mean hen-day egg production (HDEP, P < 0.01), egg mass (EM, P < 0.01), and higher feed conversion ratio (FCR, P < 0.001). Higher egg weight (P < 0.01) was observed in 95 and 100% dAA/CP level diets. However, Haugh unit (P < 0.01) and albumen height (P < 0.01) were higher in 85 and 90% diets. The inclusion of protease reduced the feed consumption (P=0.0247), FCR for dozens of eggs (P=0.0049) from 30 to 49 wk of age without affecting the HDEP or EM. Protease supplementation and dAA/CP level had an effect on the apparent ileal digestibility (AID) of CP (P=0.019), Lys (P < 0.01), Thr (P < 0.01), Trp (P=0.017), and Val (P < 0.01). Addition of protease significantly increased egg income (P=0.033) and return on investment (P=0.00223) from 30 to 37 wk of age. At 38 to 50 wk of age, dAA/CP level had a significant effect on egg income (P < 0.001), feed cost (P < 0.001), and return on investment (P < 0.001). This experiment indicates that the inclusion of protease in 90 and 95% lower dAA/CP diets could help improve the digestibility of CP, and key amino acids and maintain productive performance of corn and soybean meal-based diets in Hy-Line W-36 laying hen from 30 to 50 wk of age.

Effect of body size on the long-term reproductive output of eastern Atlantic loggerhead turtles Caretta caretta

We assessed the relationship between body size and several important life history parameters to understand the demographic significance of interpopulation variability in the body size of loggerhead turtlesCaretta carettanesting on Boa Vista Island (Cabo Verde). The adult growth rate (0.34 ± 0.60 cm yr-1), annual mortality rate (0.13, 95% CI: 0.12-0.15) and remigration interval (3.1 ± 1.2 yr) were independent of curved carapace length (minimum curved carapace length [CCLmin]). Conversely, the body condition index decreased significantly with female CCLmin. The clutch size, mean egg mass, mean hatchling straight carapace length and mean hatchling mass increased significantly with female CCLmin. However, there was no relationship between female size and hatching success. Randomization and bootstrapping were used to incorporate variability when calculating the average individual fecundity over 20 yr, a period that accumulated, on average, 94% of the adult mortality. The overall fecundity during this period increased with carapace length at first maturity (71 cm CCLmin: 815 eggs, 95% CI: 653-863; 80 cm CCLmin: 906 eggs, 95% CI: 822-959; 90 cm CCLmin: 1089 eggs, 95% CI: 926-1415). However, only 8% of the adult females nesting on Boa Vista Island are larger than 90 cm CCLmin, and they produce less than 12% of the total annual egg production. The scarcity of large females might result from a shortage of high-quality foraging grounds where females may reach first sexual maturity at a large carapace length and from the combined effect of a small carapace length at first sexual maturity, low adult somatic growth and high adult mortality.

A comparison of the breeding biology of the Bornean Whistling-Thrush (Myophonus borneensis) and White-crowned Forktail (Enicurus leschenaulti borneensis)

Advances in understanding geographic patterns of life history variation depend on documentation of life history traits for species in poorly studied regions. In the tropics, most species have not had their life history traits described. We compared the reproductive biology of two closely related Muscicapids, the Bornean Whistling-Thrush (<em>Myophonus borneensis</em>) and the Bornean subspecies of the White-crowned Forktail (<em>Enicurus leschenaulti borneensis</em>), coexisting in Mount Kinabalu Park in Sabah, Malaysia. Both species specialize in riparian habitats, but whistling-thrushes are more adaptable to human presence and can be found nesting on and foraging around buildings, whereas forktails are more wary of humans. We located and monitored 77 forktail nests and 130 whistling-thrush nests from 2009 to 2020. Mean clutch size was 2.00 ± 0.04 for forktails and 1.89 ± 0.04 for whistling-thrushes. Mean egg mass at lay was 4.07 ± 0.04 g for forktails and 11.65 ± 0.12 g for whistling-thrushes. Forktail incubation period (17.0 ± 0.42 d) was slightly shorter than for whistling-thrush (18.6 ± 0.19 d), but both species had similar rates of incubation attentiveness. Nestling periods were much shorter for the forktail (15.89 ± 0.39 d) than the whistling-thrush (24.00 ± 0.20 d). The shorter nestling period was associated with faster growth and higher provisioning rates for forktails than whistling-thrushes. Whistling-thrushes are larger and better able to protect their nests from predation, yielding much lower daily nest predation rates (0.012 ± 0.002) than in forktails (0.042 ± 0.006). Indeed, whistling-thrushes were themselves predators of nestlings and eggs of other passerines, whereas forktails were not. The larger size and lower predation risk may explain the slower growth and development of whistling-thrushes. Both species are vulnerable to climate change and droughts because of their reliance on riparian habitats.

Egg production, fertility, hatchability and immune responses of some chicken strains under high ambient temperatures.

This experiment was designed to investigate and compare the egg production, fertility, hatchability and immune responses of some local developed Egyptian chicken strains under high ambient temperatures. A total of 108 (26weeks old) laying hens of Matrouh, Silver Montazah, Mandarah and Inshas (9 hens×3 replicates×4 strains) were used to evaluate the impact of thermal stress (24-34ºC) during summer season (June, July and August) on egg production, fertility, hatchability and immune responses. The obtained results revealed that final body weight (FBW/g) and body weight change (BWC/g) among different chicken strains were not affected. The daily feed consumption (FC/g) and feed conversion ratio (FCR) for Silver Montazah and Inshas strains were significantly (p≤.05) higher than those of Matrouh and Mandarah strains. The mean egg production (EP/%) and egg mass (EM) for Silver Montazah and Inshas strains were significantly (p≤.05) higher than those of Matrouh and Mandarah strains. The highest percentages of hatchability of total eggs (HTE) and fertile eggs (HFE) were recorded in Inshas chickens, while the lowest value was recorded in Mandarah chickens. Also, the highest embryonic mortalities (p≤.05) and lowest chick weight at hatch (CWH/g) were recorded in Mandarah chickens compared with the other strains. The highest values for antibody titres against phytohemagglutinin-P (PHA-P) were recorded in Mandarah chickens, while the least values were recorded in Inshas chickens.

Study on varietal preferences and seasonal incidence of parasitoids of rice pests

The egg masses of yellow stem borer, larvae of leaf folder and rice horned caterpillar and eggs of ear head bug were collected randomly at fortnightly interval from four different varieties viz., CO 43, CO 50, CO 51 and CR 1009 from the rice field. The data was pooled and per cent parasitization was calculated to find out the varietal preference and seasonal variations of parasitoids. Among the four different varieties tested for the preference of parasitoids, per cent parasitization of stem borer egg mass was found to be more (26.59) in CO 50. The per cent parasitization of leaf folder larvae and rice horned caterpillar was found to be maximum in CO 51(40.29) and CO 43(33.21), respectively. In case of ear head bugs, the egg parasitization was maximum (27.70) in CO 50. The mean egg mass parasitization of stem borer was highest (71.88) in first fortnight of December. The larval parasitization of leaf folder and rice horned caterpillar were found to be maximum during the second fortnight of December (64.3) and the first fortnight of January (71.88), respectively. The parasitism rate of ear head bug eggs was maximum (62.95) during the second fortnight of December. Interestingly, phoresy exhibited by Sceliocerdo sp. an egg parasitoid of Neorthacris sp. was also recorded.

Does the vicinity of the Black-Headed Gull colony (Chroicocephalus ridibundus) increase the breeding success of the Common Tern (Sterna hirundo) on the islands of the middle Vistula?

We conducted our study in the Common Tern colony (STH) located on an island in the middle Vistula River course, at the height of the city of Dęblin (km 393–394 of the waterway), in 2017. Our goal was to investigate some aspects of the biology and reproductive ecology of this species. Due to the fact that STH breeds both in single-species as well as in two- or multi-species colonies, in associations with Little Terns (Sternula albifrons), Black-Headed Gulls (Chroicocephalus ridibundus) (LAR) and/or Mew Gulls (Larus canus), we wanted to investigate whether the neighborhood of other species (in this case LAR) affected hatching success and chick survival in STH. Our results clearly show that the presence of breeding terns in the neighborhood of the LAR colony was not accidental and/or caused by the lack of space on the island and/or the possibility of nesting elsewhere. The height of nesting site, type of nesting habitat, clutch size, mean egg volume and mean egg mass of these STH pairs did not differ significantly from those that formed a single species colony, on the same island but several hundred meters away. However, STH nests in the neighborhood of the LAR colony were established much earlier and both the hatching success and chick survival of STH during the early-chick stage were twice as high. Thus, we can conclude that the LAR colony could provide an effective protection against predation of crows, magpies and gulls, dangers which accounted for the vast majority of STH nest failures in the year of our study.

Interacting effects of identity, size, and winter severity determine temporal consistency of offspring phenotype

Offspring size can strongly influence offspring fitness; however, the importance of female identity to offspring size determination is poorly understood, despite the potential for identity effects to drive offspring size adaptation and population dynamics. We tracked reproductive investment (skein mass) and mean egg diameter, mass, and density produced by individual female yellow perch (Perca flavescens) over four spawning years to determine the influences of maternal identity, size, and winter severity to reproductive trait variation. Individual identity significantly influenced egg diameter and mass, but did not affect egg density or skein mass. All egg traits were negatively influenced by winter severity prior to spawning, and egg mass and diameter were also negatively related to maternal size. Our results suggest that individual effects can comprise a large amount of the intrapopulation variation in reproductive traits in populations, which may be unaccounted for in studies examining only environmental or phenotypic effects. Accounting for potential identity effects would likely improve our understanding of constraints on offspring size plasticity and potential responses of offspring size in populations experiencing environmental change.

Performances of Nageswari duck of Bangladesh under intensive management condition

The present study was conducted to know the production and reproduction potentials, and egg quality characteristics of Nageswari duck under intensive management condition. Data were collected from a nucleus flock of Nageswari ducks that have been maintained from day old to 72 weeks of age at AI center, Bangladesh Agricultural University, Mymensingh, from May 2015 to October 2016. Irrespective of sex, the average live weight of ducklings at day old, 1st, 3rd, 5th, 7thand 9thweeks of age were observed to be 38.85±1.40, 99.06±2.93, 373.29±8.73, 650.31±11.26, 867.74±11.79 and 1076.11±16.34 g, respectively. There was a steady increasing trend observed in live weights for both drakes and ducks from 17thto 72 weeks of age. The average age of sexual maturity and weight were found 130±1.83 days and 1400.84±12.68g respectively. The average egg weight and annual egg production were 58.20±1.50g and 204.23±14.19 no’s, respectively. Hen day egg production was found 55.67±2.74% while the peak production was observed at 26th week of age. The estimated mean egg mass production (g/b/day), feed intake(g) during laying, feed conversion efficiency and performance efficiency index of Nageswari duck were 32.40±2.29, 154.85±2.27, 4.63±0.21 and 20.92±1.37, respectively in Nageswari duck. The external egg quality characteristics like shape index, egg breaking strength, shell thickness and membrane thickness were observed to be 74.59±0.61, 2.00±0.03 kg/cm2, 3.99±0.06 mm and 0.50 ± 0.02 mm respectively whereas, internal quality attributes such as albumen index, yolk index, yolk color score and Haugh unit were 8.89±0.29, 34.36±0.61, 8.42±0.28 and 86.29±1.06, respectively. In conclusion, the studied parameters of Nageswari duck provided some breed specific baseline information and year round actual production potentials of this genetic resource under intensive management condition that could be utilized for future conservation and breeding programs in Bangladesh.Bang. J. Anim. Sci. 2017. 46 (3): 198-205

The breeding biology of endemic Spectacled Parrotbill (Sinosuthora conspicillatus) in Lianhuashan National Nature Reserve, Gansu Province, China

BackgroundLife history traits play critical roles in population survival and evolution. Breeding information should be particularly detailed in order to provide significant insights into the population status and the evolution of other traits. To our knowledge, there is still no information about the breeding biology of Spectacled Parrotbill (Sinosuthora conspicillatus), an endemic parrotbill in China.MethodsWe searched the nests, checked all nests found and recorded the information of eggs, nestlings and nest sites of the Spectacled Parrotbill from 2013 to 2015 at Lianhuashan National Nature Reserve in Gansu Province, China.ResultsA total of 16 nests were found. Nest trees were artificial young spruces and honeysuckles. Mean nest height was 0.89 ± 0.47 m (n = 16) above the ground level. All nests were cup-shaped and constructed using leaves, fine strips of barks and grasses by both parents. The mean clutch size was 4.42 ± 0.79 (n = 12). The eggs were oval in pale blue without speckles, and the mean egg mass was 1.25 ± 0.07 g (n = 27). The egg length was 15.56 ± 0.46 mm (n = 27) and the width was 12.46 ± 0.29 mm (n = 27). Incubation period was 13 days and nestling period was 13–14 days. The breeding success rate was 46%, and among those failed nest, 71% were depredated and 29% were deserted.ConclusionDetailed life history information about parrotbill is still limited. The breeding biology of Spectacled Parrotbill reported in the present study should be helpful for further research about population, breeding behavior and conservation of this bird.

Intraclutch egg size variation is independent of ecological context among years in the European Starling Sturnus vulgaris

Female birds can potentially utilise various mechanisms, such as intraclutch egg size variation (ICESV), to modulate offspring quality. If this represents an ‘adaptive’ strategy allowing females to adjust reproductive effort after laying of the first egg, as information on resources becomes more predictable later in the laying sequence, then we would predict that ICESV would vary with ecological context, e.g. in ‘good’ versus ‘bad’ years. Here, in European Starlings (Sturnus vulgaris), we tested specific predictions that (1) females would lay relatively small last laid eggs in ‘poor’ years (with early laying and below-average breeding productivity); and (2) that ICESV would be lower in good years (late laying, above-average productivity) so that late-hatched chicks would not be disadvantaged. At the individual level we predicted (3) that repeatability of ICESV would be low if females adjusted this in relation to the environment in different years; and (4) that within-individual variation in ICESV should correlate with the number, and timing, of loss of chicks. Mean ICESV averaged −1.9% (measured as last egg mass relative to mean egg mass), typical of other hole-nesting passerines. However, our results did not support any of our hypotheses: (1) although there was annual variation in ICESV, in all years egg mass decreased through the laying sequence; (2) annual variation in ICESV was not consistent with variation in phenology or breeding productivity among years; (3) marked individual variation in ICESV (last laid egg varied from −20 to +10% relative to mean egg mass within clutches) was repeatable, i.e. individual females did not adjust ICESV in subsequent breeding attempts; and (4) variation in the magnitude of ICESV, alone and combined with hatching asynchrony, did not predict early brood loss. Our study suggests that ICESV is a relatively inflexible component of an individual female’s phenotype that might contribute to variation in individual quality.

Variability of breeding resource partitioning in a lacertid lizard at field scale

Human activities cause increasingly deep alterations to natural environments. Yet, the effects on vertebrates with low dispersal capacity are still poorly investigated, especially at field scale. Life history variation represents one means by which species can adapt to a changing environment. Among vertebrates, lizards exhibit a high degree of variation in life-history traits, often associated with environmental variability. We examined the female breeding output ofPodarcissiculus(Lacertidae) inside agricultural habitats, to test whether different cultivation and management influence the life-history traits of this species. Interestingly, we recorded variability of female breeding output at a very fine scale, namely among adjacent vineyards and olive orchards under different management levels. Lizards displayed the lowest breeding effort in the almost unmanaged sites, while clutch mass, relative fecundity and mean egg mass slightly increased in more intensively managed sites. However, in the most intensive cultivations we detected a life-history trade-off, where eggs from larger clutches tended to be relatively smaller than eggs from smaller clutches. This pattern suggests that agriculture can influence lizard reproductive output, partly favouring it in the presence of medium intensity cultivation but causing, in the most intensively managed sites, some environmental constraints that require a peculiar partitioning of the breeding resources. Even though further studies are needed to clarify the mechanisms driving the observed pattern, our results can be considered a starting point for evaluating the analysis of lizard breeding features as a tool to assess the impact of human activities, at least in agricultural environments.

Notes on the reproductive ecology of the rough-footed mud turtle (Kinosternon hirtipes) in Texas, USA

Kinosternon hirtipes is among the least-studied North American turtles and little is known concerning reproduction. In the United States, K. hirtipes occurs at < 10 sites within a single creek drainage in Presidio County, Texas where it is considered a threatened species. We investigated the reproductive ecology of one of these populations at Plata Wetland Complex in 2007. We captured nine female K. hirtipes in wire mesh traps and hoop nets baited with fish. Eggs were obtained by injecting females with oxytocin. We recovered 19 eggs from six females captured in May and June. The smallest female that produced eggs was about 7.1 years old. Mean (± 1SD) clutch size, egg length, egg width, egg mass, and clutch mass were 3.1 ± 1.4 eggs, 28.7 ± 1.4 mm, 17.5 ± 0.9, 5.3 ± 0.6 g, and 17.5 ± 0.8 g, respectively. Relative egg mass and relative clutch mass were 0.035 and 0.011, respectively. There was a significant, positive linear relationship between female carapace length (CL) and egg width. The relationship between CL and relative egg mass was negative, and approached statistical significance. Relationships between CL and clutch size, egg length, and egg mass were not significant. Reproductive attributes of K. hirtipes in Texas are similar to those reported from a population in Mexico.

Reproduction of Captive Asian Giant Softshell Turtles,Pelochelys cantorii

Abstract The Asian giant softshell turtle, Pelochelys cantorii, is endangered and has been designated as a first-grade protected animal in China. This article reports the results of a study on the reproductive biology of Asian giant softshell turtles. Two individuals, a male and a female from the Suijiang River in Guangning County, Guangdong Province, were introduced into captivity 8 yrs ago. The 2 turtles have engaged in mating activity since April 2014, and the female laid a total of 66 eggs in 2014 (25 eggs on 15 June, 22 eggs on 30 June, and 19 eggs on 14 July). The egg laying took an average of 50.6 min. Egg shape was spherical, and mean (± SD) egg mass was 13.27 ± 0.97 g, with mean diameter 2.90 ± 0.12 cm. The viability rate was 46% and the hatching rate 33%, and only 10 neonates successfully hatched. Hatchling body weight averaged 10.0 ± 0.56 g, carapace length averaged 42.25 ± 3.69 mm, carapace width averaged 40.25 ± 1.58 mm, and carapace height averaged 12.54 ± 0.91 mm. The juvenile turtles diffe...

The breeding biology of Red-Whiskered Bulbul (Pycnonotus jocosus) in Xishuangbanna, southwest China.

To fill the gap in breeding biology information about the Red-Whiskered Bulbul (Pycnonotus jocosus), in 2013, we studied the breeding biology of this species in Xishuangbanna, southwest China. The breeding began from February and continued until early August. The breeding strategy of P. jocosus was more flexible and their nests were only built in cultivated landscapes, whereas, no nest building in native tropical rain forest was found. Small open cup nests were built on 50 different plant species, and at heights ranging from 2.1±0.6 m above the ground (n=102). The mean clutch size was 2.53±0.51 eggs (n=40) and the mean egg mass was 2.81±0.25 g (n=60). The average incubation period was 11.1±0.5 days (n=14), and the average nestling period was 11.0±0.8 days (n=31). The overall nest success was 34.22%.The hatching and fledging showed either asynchrony or synchrony. Invertebrate food decreased with nestling age, whereas, plant food increased with nestling age. Moreover, distinct parental roles of the parents in nestling period were found. Compared with other passerine species, P. jocosus spent less time in incubating (58%). The clutch size, incubation and nestling period of the P. jocosus in southwest China were different from those of the P. jocosus in India.

Association of Egg Mass and Egg Sex: Gene Expression Analysis from Maternal RNA in the Germinal Disc Region of Layer Hens (Gallus gallus).

Female birds have been shown to manipulate offspring sex ratio. However, mechanisms of sex ratio bias are not well understood. Reduced feed availability and change in body condition can affect the mass of eggs in birds that could lead to a skew in sex ratio. We employed feed restriction in laying chickens (Gallus gallus) to induce a decrease in body condition and egg mass using 45 chicken hens in treatment and control groups. Feed restriction led to an overall decline of egg mass. In the second period of treatment (Days 9-18) with more severe feed restriction and a steeper decline of egg mass, the sex ratio per hen (proportion of male eggs) had a significant negative association with mean egg mass per hen. Based on this association, two groups of hens were selected from feed restriction group, that is, hens producing male bias with low egg mass and hens producing female bias with high egg mass with overall sex ratios of 0.71 and 0.44 respectively. Genomewide transcriptome analysis on the germinal disks of F1 preovulatory follicles collected at the time of occurrence of meiosis-I was performed. We did not find significantly differentially expressed genes in these two groups of hens. However, gene set enrichment analysis showed that a number of cellular processes related to cell cycle progression, mitotic/meiotic apparatus, and chromosomal movement were enriched in female-biased hens or high mean egg mass as compared with male-biased hens or low mean egg mass. The differentially expressed gene sets may be involved in meiotic drive regulating sex ratio in the chicken.

Reproductive demography of two closely related Emydine Turtles in a spring fed system

Freshwater turtles are appropriate organisms for studying maternal investment in offspring because, unlike most long-lived vertebrates, turtles show high fecundities and most provide no parental care. We studied reproductive patterns of two emydine freshwater turtle species, the Texas river cooter (Pseudemys texana) and the red-eared slider (Trachemys scripta elegans) at Spring Lake, Hays County, Texas during the 2009 nesting season. Forty-six percent of all nesting Texas river cooters and 25% of all nesting red-eared sliders nested twice, with some Texas river cooters nesting more than twice. Mean egg mass, egg length, and egg width decreased in subsequent clutches in Texas river cooters. However, there was an insufficient sample size of subsequent clutches (n = 6) to draw conclusions for red-eared sliders. Red-eared sliders did not show a positive relationship between clutch size and body size. We found that in both species there was a positive relationship between egg width and egg mass in relation to maternal body size. However, only Texas river cooters showed a positive relationship between clutch size and maternal size, while only red-eared sliders showed a positive relationship between egg length and maternal size. By comparing reproductive parameters of these two coexisting populations, we concluded that the members of these two species allocate resources differently for reproduction.

Geographic variation in hatchling size in an oviparous skink: effects of maternal investment and incubation thermal environment

Geographic variation in offspring size can be viewed as an adaptive response to local environmental conditions, but the causes of such variation remain unclear. Here, we compared the size and composition of eggs laid by female Chinese skinks (Plestiodon chinensis) from six geographically distinct populations in southeastern China to evaluate geographic variation in hatchling size. We also incubated eggs from these six populations at three constant temperatures (24, 28 and 32 °C) to evaluate the combined effects of incubation temperature and population source on hatchling size. Egg mass and composition varied among populations, and interpopulation differences in yolk dry mass and energy content were still evident after accounting for egg mass. Population mean egg mass and thus hatchling mass were greater in the colder localities. Females from three northern populations increased offspring size by laying larger eggs relative to their own size. Females from an inland population in Rongjiang could increase offspring size by investing relatively more dry materials and thus more energy into individual eggs without enlarging the size of their eggs. The degree of embryonic development at oviposition was almost the same across the six populations, so was the rate of embryonic development and thus incubation length at any given temperature. Both incubation temperature and population source affected hatchling traits examined, but the relative importance of these two factors varied between traits. Our data show that in P. chinensis hatchling traits reflecting overall body size (body mass, snout-vent length and tail length) are more profoundly affected by population source. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 113, 283–296.