Early Egg Research Articles

Early egg traits in Cancer setosus (Decapoda, Brachyura): effects of temperature and female size

Previous study on Cancer setosus Molina, 1782 showed that latitudinal changes in temperature control the number of annual egg masses. This study focused on the effects of pre- oviposition temperature and female size on egg traits in C. setosus from northern (Antofagasta, 23° S) and central-southern (Puerto Montt, 41°S) Chile. Blastula eggs produced in nature ranged in dry mass (DM) from 9.1 to 15.1 µg, in carbon (C) from 4.8 to 8.4 µg, in nitrogen (N) from 1.0 to 1.6 µg, in C:N ratio between 4.7 and 5.4, and in volume (V) between 152 and 276 mm 3 × 10 -4 per female. Blastula eggs from females caught early in the reproductive season in Puerto Montt (September 2006) were significantly higher in DM, C, N, and V than those of females caught 2 mo later, reflecting a seasonal increase in water temperature. In Puerto Montt 'early' and 'late' season blastula eggs were higher in DM, C, N, and V than eggs from Antofagasta by about 32 and 20%, respectively. Sub- sequent egg masses produced in captivity in Puerto Montt followed this pattern of smaller eggs with lower DM, C, and N content at higher pre-oviposition temperatures. In Antofagasta no significant difference in DM, C, N, and V between eggs produced in nature and subsequent eggs produced in captivity was found and all egg traits were significantly positively affected by maternal size. Repro- ductive plasticity in C. setosus helps to explain the species wide latitudinal distribution range.

Expression of multiple Src family kinases in sea urchin eggs and their function in Ca 2+ release at fertilization

Egg activation at fertilization in deuterostomes requires a rise in intracellular Ca 2+, which is released from the egg's endoplasmic reticulum. In sea urchins, a Src Family Kinase (SpSFK1) is necessary for the PLCγ-mediated signaling event that initiates this Ca 2+ release (Giusti, A.F., O'Neill, F.J., Yamasu, K., Foltz, K.R. and Jaffe, L.A., 2003. Function of a sea urchin egg Src family kinase in initiating Ca2+ release at fertilization. Dev. Biol. 256, 367–378.). Annotation of the Strongylocentrotus purpuratus genome sequence led to the identification of additional, predicted SFKs (Bradham, C.A., Foltz, D.R., Beane, W.S., Amone, M.I., Rizzo, F., Coffman, J.A., Mushegian, A., Goel, M., Morales, J., Geneviere, A.M., Lapraz, F., Robertson, A.J., Kelkar, H., Loza-Coll, M., Townley, I.K., Raisch, M., Roux, M.M., Lepage, T., Gache, C., McClay, D.R., Manning, G., 2006. The sea urchin kinome: a first look. Dev. Biol. 300, 180–193.; Roux, M.M., Townley, I.K., Raisch, M., Reade, A., Bradham, C., Humphreys, G., Gunaratne, H.J., Killian, C.E., Moy, G., Su, Y.H., Ettensohn, C.A., Wilt, F., Vacquier, V.D., Burke, R.D., Wessel, G. and Foltz, K.R., 2006. A functional genomic and proteomic perspective of sea urchin calcium signaling and egg activation. Dev. Biol. 300, 416–433.). Here, we describe the cloning and characterization of these 4 additional SFKs and test their function during the initial Ca 2+ release at fertilization using the dominant-interfering microinjection method coupled with Ca 2+ recording. While two of the new SFKs (SpFrk and SpSFK3) are necessary for Ca 2+ release, SpSFK5 appears dispensable for early egg to embryo transition events. Interestingly, SpSFK7 may be involved in preventing precocious release of Ca 2+. Binding studies indicate that only SpSFK1 is capable of direct interaction with PLCγ. Immunolocalization studies suggest that one or more SpSFK and PLCγ are localized to the egg cortex and at the site of sperm–egg interaction. Collectively, these data indicate that more than one SFK is involved in the Ca 2+ release pathway at fertilization.

Effects of Housing System and Age on Early Stage Egg Production and Quality in Commercial Laying Hens

2grazing area per bird). The effect of age on measured traits was investigated with 4 weeks intervals. Four replicates containing each 40 birds were designed for both of free-range and cage systems. The egg production and cracked egg percentage, daily feed intake and feed consumption per produced egg were different between housing systems. Regardless the housing system; daily feed intake and feed intake per produced egg increased, while egg production, cracked egg percentage decreased by the age of layer. Interactions between layer age and housing systems were found significant for egg production, cracked egg percentage, albumen index, albumen pH and haugh unit parameters. Yolk color (P<0.03) was considerably darker and shell thickness was significantly greater (P<0.01) in free-range eggs while albumen pH was significantly higher (P<0.01) in cage group. We concluded that egg production and quality traits were significantly affected by the housing system furthermore, maintaining external and internal egg quality parameters in constant state especially in free-range system appeared to be difficult.

Evaluating the use of the Daily Egg Production Method for stock assessment of blue mackerel, Scomber australasicus

The present study evaluates the suitability of the Daily Egg Production Method (DEPM) for stock assessment of blue mackerel, Scomber australasicus and assesses methodological options for future applications. In southern Australia, estimates of mean daily egg production were higher for Californian Vertical Egg Tow (CalVET) nets than bongo nets, and in eastern Australia, were higher in October 2003 than July 2004. Estimates of spawning area for southern Australia were three times higher for bongo nets than CalVET nets. Similar estimates of spawning area were obtained using standard (manual) gridding and natural neighbour methods. Large samples and reliable estimates of all adult parameters were obtained for southern Australia. Relatively few spawning adults were collected off eastern Australia. Preliminary best estimates of spawning biomass for southern and eastern Australia were 56 228 t and 29 578 t, respectively, with most estimates within the ranges of 45 000–68 000 t and 20 000–40 000 t respectively. The DEPM is suitable for stock assessment of S. australasicus. Several technical refinements are required to enhance future applications, including: genetic techniques for identifying early stage eggs; a temperature–egg development key; improved methods for sampling adults off eastern Australia; and measurements of the degeneration rates of post-ovulatory follicles at several temperatures.

The Effect of Sex Peptide and Calorie Intake on Fecundity in FemaleDrosophila melanogaster

The accessory gland proteins (Acps) of the male Drosophila cause changes in the behavior and physiology of female flies. Sex peptide (SP) is one of the Acps that initiates many changes, including an increase in egg production. The data presented here show that SP overexpression in transgenic (G-10) female flies increases egg production when females are kept on a standard and high-calorie diet, relative to controls that do not express SP. Particularly, a high increase in egg production observed in G-10 females on a high-calorie diet suggests that SP overexpression magnifies the female response to caloric uptake. However, on a calorie-restricted diet, the fecundity of G-10 females overexpressing SP is lower than control females. On a high-calorie diet, mating increases early egg production in G-10 and control females, but lifelong total egg production is only increased in control females, most likely due to the physiological changes set off by substantial initial egg production in G-10 females.

The use of species-specific TaqMan probes for identifying early stage gadoid eggs following formaldehyde fixation

Abstract Goodsir, F., Armstrong, M. J., Witthames, P. R., Maxwell, D. L., and Fox, C. J. 2008. The use of species-specific TaqMan probes for identifying early stage gadoid eggs following formaldehyde fixation. – ICES Journal of Marine Science, 65: 1573–1577. Surveys of fish eggs are increasingly being used to monitor the spawning areas and stock status of commercially important species such as Atlantic cod (Gadus morhua), but early stage cod eggs are visually indistinguishable from those of several other common co-occurring species, including haddock (Melanogrammus aeglefinus) and whiting (Merlangius merlangus). In recent surveys in the Irish and North Seas, a molecular identification technique (TaqMan multiplex real-time polymerase chain-reaction) assay has been used to overcome this problem. The method needs high-quality DNA, so the current protocol requires that individual “cod-like” eggs are “presorted” from plankton hauls on board ship and immediately preserved in ethanol. This increases seagoing staff costs, can be a difficult process at sea, and means that plankton sampling cannot be undertaken from non-specialized vessels such as fishing boats. Successful application of TaqMan probes to DNA from eggs preserved in formalin would overcome these problems, but previous attempts have resulted in poor success. In this study, batches of hatchery-sourced cod, haddock, and whiting eggs were fixed in 4% buffered formalin for up to 3 weeks, then transferred to a formaldehyde-free solution for 1, 2, or 3 months. After these periods they were assessed visually for fixation quality and analysed using species-specific TaqMan probes. Eggs, which had been fixed for up to 3 weeks in formalin, were identified successfully, although the positive rate (84–96%) was slightly lower than samples preserved throughout in ethanol (92–99%). There was no increase in the percentage of eggs misidentified comparing formalin-fixed and ethanol-preserved material. These results suggest that TaqMan probes can be applied successfully to fish eggs fixed in 4% buffered formalin for up to 3 weeks.

Illuminance, sexual maturation, and early egg production in female broiler breeders

1. Broiler breeders were reared at an initial illuminance of 13, 21 or 44 lux and transferred at 20 weeks and a mean body weight of 2.06 kg to floor pens at 25, 55 or 71 lux, or to individual cages at various intensities between 3 and 138 lux. 2. Rate of sexual maturation was not significantly affected by the light intensity experienced during the rearing period, but was progressively accelerated by the provision of a brighter illuminance after 20 weeks, up to a ceiling of about 14 lux. There was no interaction between the pre- and post-20-week illuminance. 3. Cumulative egg numbers to 39 weeks were unaffected by illuminance in the rearing period, positively correlated with illuminance post 20 weeks up to an asymptote at about 8 lux, and highly correlated with age at sexual maturity. Peak rate of lay was both delayed and depressed at 3 lux. 4. It is concluded that the minimum light intensity required at bird-head height to achieve satisfactory photostimulation and an optimal peak rate of lay in broiler breeders is 10 lux, but that a higher illuminance would be prudent for broiler breeders kept in floor pen facilities to maximise nest-box usage.

New method to deliver exogenous material into developing planarian embryos

The ability to report or modify the embryological processes in living embryos is pivotal for developmental biology research. Planarian embryology has experienced renewed interest as the genetic pathways that drive adult regeneration were found to be involved in the development of embryos. The major drawback to the study of planarian embryology is the absence of methods that give access to the embryos and enable their manipulation. Herein, we report on a novel method for delivering external material into developing embryos using nanosecond laser pulses. When focused on the eggshell surface under optimal parameters, laser pulses ablate the protective case and open a pathway throughout which foreign material can be delivered. In this study, we used egg capsules from Schmidtea polychroa (Schmidt, 1861) to microinject 1 microm fluorescein isothiocyanate fluorescent beads into the live embryos. We obtained viability values ranging from 15% in early egg capsules to 100% in late developmental stages. Moreover, we measured the delivery effectiveness as the number of hatchlings containing fluorescent beads per microinjected egg capsule, reaching 100% in early stages and almost 40% in late stages. This is the first time that planarian embryos have been modified without compromising normal development. We consider that this technique will be of extreme value to future work on planarian developmental biology and regeneration, enabling the application of modern functional tools to the study of this Lophotrochozoan.

Differential Egg Mortality of Georges Bank Cod and Haddock Inferred from Two Independent Estimates of Seasonal Egg Production

Georges Bank Atlantic cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) stocks have undergone significant changes over the last 40 years with the reduction of older spawners and increased incidence of young mature fish. Captive studies, from other investigations, have noted that firstand second-time spawners exhibit lower egg hatching success, and especially for haddock compared to cod. Spawning stock biomass (SSB), derived from virtual population analysis (VPA), has been considered as an overestimate of a stock’s spawning potential since it does not fully account for differences in age or size of spawners. The Northeast Fisheries Science Center’s (NEFSC) ichthyoplankton Surveys (1979–1999) have provided an independent estimate of seasonal egg production to compare with a VPA-fecundity based estimate. Since the early stage eggs of the two species are indistinguishable, their numbers were estimated by apportioning the total egg abundance (cod plus haddock) at a station by the late stage abundance ratio, assuming equal mortality for the two species. For cod, the Surveys overestimated the VPA-derived egg production in many years by as much as an order of magnitude. However, for haddock, the VPA-derived egg production estimates were mostly higher than those from the Surveys. Comparing the ratio of the two egg production estimates versus the total combined VPA egg production of cod and haddock, the cod ratios were high when haddock was abundant, especially during the years 1995–1999, and closer to one when cod comprised the greater part of the total. The corresponding analysis for haddock was the reverse to that of cod further supporting the hypothesis that the higher egg mortality of the reduced age population of haddock biased the seasonal egg production estimates of both haddock and cod. These ratios appear to explain 60–70% of the variability in the ratio of Survey to VPA seasonal egg production, while other factors might be related to fecundity and age-class composition of the SSB, or changes in egg mortality rates over the time series. Our Survey estimates also suggest that haddock egg mortality is greater than cod. Thus, the seasonal egg production estimates from egg Surveys based on constant egg mortality are probably inaccurate, especially since the mid-1990s. Cod egg production may have been overestimated and haddock’s underestimated.

GENETIC INCOMPATIBILITIES IN KILLIFISH AND THE ROLE OF ENVIRONMENT

Measuring reproductive isolation across multiple generations and environments is a key endeavor in speciation research because it indicates which isolating barriers currently prevent introgression and the extent to which they are intrinsic versus environmentally dependent. Here, I present data from several crosses (parental crosses, F1s, F2s, back-crosses) between two species of killifish (Lucania goodei and L. parva) that have diverged along a salinity gradient (L. goodei--freshwater, L. parva--euryhaline). Offspring were raised under high and low salinity to test for (1) extrinsic isolation, (2) intrinsic isolation manifested through genetic incompatibilities, and (3) environmentally dependent genetic incompatibilities. I found evidence for both intrinsic and extrinsic isolation, but no evidence for environmentally dependent genetic incompatibilities. The presence of extrinsic and intrinsic isolation varied among fitness measures, and all forms of reproductive isolation were asymmetric. Early egg survival was independent of salinity, but demonstrated pronounced intrinsic isolation. Both extrinsic and intrinsic isolation existed for egg hatching and survival of fry to the eating stage. Unfortunately, the order in which extrinsic and intrinsic isolation arose is unresolved. Understanding the extent to which adaptation to salinity creates multiple forms of reproductive isolation is critical for understanding diversification in many fish taxa.

TIME BUDGETS OF COMMON MURRES VARY IN RELATION TO CHANGES IN INSHORE CAPELIN AVAILABILITY

Changes in capelin (Mallotus villosus) biology since the 1990s have directly or indirectly induced variable breeding conditions for many seabirds in the Northwest Atlantic. Time budgets of the same individual Common Murres (Uria aalge) were examined in relation to annual variations in the arrival of inshore spawning capelin during three consecutive chick-rearing periods (1998–2000) on Great Island in the Witless Bay Ecological Reserve, Newfoundland, Canada. Despite high foraging effort (longer provisioning trips, lower co-attendance time, and faster colony departure after a brooding bout), chick-feeding rates were low during early chick rearing in 2000 due to a mismatch between early egg hatching and the later inshore arrival of spawning capelin. Time budgets of murres breeding on Great Island were examined in relation to those of murres in other nearby colonies and to long-term changes in capelin spawning behavior across decades (1982–1985 versus 1998–2000). Recent overall provisioning rates on Great Island were comparable to those of other nearby colonies during the same time period (with the exception of Funk Island) and to those reported during the 1980s. However, murres breeding in recent years in the reserve exhibited higher foraging effort, which is likely linked to recent changes in the availability of capelin as a result of later spawning, changes in capelin distribution, and their overall smaller size. Murres currently may be constrained to timing their egg laying such that hatching coincides with the arrival of inshore capelin rather than peak capelin abundance and, thus, are vulnerable to sudden changes in the ecosystem.

The Influence of an Exogenous Microbial Enzyme Supplement on Feed Consumption, Body Growth and Follicular Development of Pre-Lay Pullets on Maize-Soy Diets

2 Abstract: An experiment was conducted to examine the benefits of supplementing maize-soy diets with a composite microbial enzyme, Allzyme SSF, for laying hens at the pullet stage. Seven hundred and twenty 12- week old Isa Brown pullets were used in the different level of protein content diets. Feed intake from 12 to 16 weeks of age was unaffected by the enzyme supplement, except at the lowest protein content (P<0.05). Feed intake was, however, affected by the enzyme supplement between 16 and 20 weeks (P<0.001) and over the entire trial period (P<0.05). Body weight at 16 weeks of age was reduced (P<0.05) on the control low- protein diet. Feed conversion ratio was not affected by dietary protein content or through supplementation with the microbial enzyme. The relative weight of the ovary was reduced (P<0.01) on the low protein control diet, but the weight of visceral organs associated with digestion was not affected. The pullets in all groups failed to come into lay at 17 weeks of age, mainly due to very severe winter, as the experiment was conducted in a house that was not completely temperature-controlled. Onset of lay occurred from about 23 weeks of age, after the hens were already on a commercial diet but effects of previous dietary treatments on early egg production were noticeable.

Recombination in the proximal region of X/X. YL or SDrosophila melanogaster females during temperature shocks in three stages of the life cycle

The specific brood patterns of recombination in the f-centromere region, the centromere marked by an attached BSYL-arm, in the inbred lines of Drosophila metanogaster were further investigated according to effects of the brood from which the females were sampled (early broods-pupal egg development; late broods-egg development present in adults). The effect on recombination by another BSYL or a y+YS-arm was studied in six successive broods from females given temperature treatment in various stages of the life cycle. Temperature treatment enhanced the recombination in affected broods, resulting in fairly uniform level in the three series. In unaffected broods there were differences between the three attachments. The data indicate a diversity between females from early and late broods in the y+YS series but not in the two BS YL series. The consequences of temperature shock are discussed as well as the influence of different Y-heterochromatin from YS and YL arms. In the light of the variation of recombination over broods the possible “centromere effect” is scrutinized.

Reproductive Biology and Functional Maturity in Females of Aegla Franca (Decapoda: Anomura: Aeglidae)

Abstract We describe the reproductive period, fecundity, and average size at the onset of functional maturity of female Aegla franca, the northernmost distributed aeglid species. The reproductive period is markedly seasonal and takes place from May (austral mid-autumn) to August (late winter). Ovigerous females appear quite abruptly in the population by May, and this condition is observed in all adult females sampled regardless of their size. The average size at the onset of functional maturity in females, at which 50% of the females sampled during the reproductive period were considered adults, was 12.75 mm CL. The smallest post-ovigerous female measured 12.06 mm carapace length (CL). Mean fecundity (±S.D.) from 41 females bearing early and intermediate eggs was 129.1 ± 32.2 and corresponded to a mean female CL of 14.11 mm. The elliptical-shaped eggs exhibited significant increase in size along the development stages. The third pair of pleopods bore higher number of eggs than the others. Compiled informa...

Reproductive Efficiency and Metabolism of Female Broiler Breeders as Affected by Genotype, Feed Allocation, and Age at Photostimulation. 3. Reproductive Efficiency

A 3 × 4 × 2 factorial trial was performed to test the effect of 3 broiler breeder strains, 4 target BW profiles, and 2 photostimulation ages on egg and chick production. Hubbard Hi-Y, Ross 508, and Ross 708 pullets were reared on BW profiles that separated at 4 wk and converged at 32 wk: standard (approximate mean target BW profile of the 3 strains used), low (12-wk BW target = 25% lower than standard followed by rapid gain to 32 wk), moderate (12-wk BW target = 150% of standard followed by lower rate of gain to 32 wk), and high (12-wk BW target = 200% of standard followed by minimal growth to 32 wk). Birds were photostimulated at 18 (18WK) or 22 wk (22WK). Twelve birds per interaction (n = 288) were individually caged at 17 wk and monitored for egg and chick production to 58 wk of age. The low BW profile delayed onset of lay, particularly in 18WK hens. Low and standard birds had a greater initial egg weight than moderate birds. The 18WK photostimulation age resulted in production of 31 small eggs (<52 g) compared with 15 in 22-wk birds. A settable (52 g) egg weight was reached earliest by standard birds (187 d of age). Average prime sequence length was reduced by 7.0 eggs in moderate and high birds compared with other profiles. The 18WK hens laid 9 more eggs (174) than 22WK birds, with no effect on unsettable eggs. The 22WK birds laid 7 more settable eggs due to increased early egg size. Total egg output was similar among BW profile treatments, although Ross 708-high hens under-performed compared with the other 708 profiles. The Ross 508-high birds laid the same number of eggs as Ross 508-standard birds (mean = 178.7). Feeding profiles affected egg production traits differently among strains. Feed intake had more effect on egg size and early production traits than BW profile or BW.

Regionalisation of the mouse visceral endoderm as the blastocyst transforms into the egg cylinder

BackgroundReciprocal interactions between two extra-embryonic tissues, the extra-embryonic ectoderm and the visceral endoderm, and the pluripotent epiblast, are required for the establishment of anterior-posterior polarity in the mouse. After implantation, two visceral endoderm cell types can be distinguished, in the embryonic and extra-embryonic regions of the egg cylinder. In the embryonic region, the specification of the anterior visceral endoderm (AVE) is central to the process of anterior-posterior patterning. Despite recent advances in our understanding of the molecular interactions underlying the differentiation of the visceral endoderm, little is known about how cells colonise the three regions of the tissue.ResultsAs a first step, we performed morphological observations to understand how the extra-embryonic region of the egg cylinder forms from the blastocyst. Our analysis suggests a new model for the formation of this region involving cell rearrangements such as folding of the extra-embryonic ectoderm at the early egg cylinder stage. To trace visceral endoderm cells, we microinjected mRNAs encoding fluorescent proteins into single surface cells of the inner cell mass of the blastocyst and analysed the distribution of labelled cells at E5.0, E5.5 and E6.5. We found that at E5.0 the embryonic and extra-embryonic regions of the visceral endoderm do not correspond to distinct cellular compartments. Clusters of labelled cells may span the junction between the two regions even after the appearance of histological and molecular differences at E5.5. We show that in the embryonic region cell dispersion increases after the migration of the AVE. At this time, visceral endoderm cell clusters tend to become oriented parallel to the junction between the embryonic and extra-embryonic regions. Finally we investigated the origin of the AVE and demonstrated that this anterior signalling centre arises from more than a single precursor between E3.5 and E5.5.ConclusionWe propose a new model for the formation of the extra-embryonic region of the egg cylinder involving a folding of the extra-embryonic ectoderm. Our analyses of the pattern of labelled visceral endoderm cells indicate that distinct cell behaviour in the embryonic and extra-embryonic regions is most apparent upon AVE migration. We also demonstrate the polyclonal origin of the AVE. Taken together, these studies lead to further insights into the formation of the extra-embryonic tissues as they first develop after implantation.

Early is better: seasonal egg fitness and timing of reproduction in a zooplankton life‐history model

Timing of reproduction influences future prospects of offspring and therefore the reproductive value of parents. Early offspring are often more valuable than later ones when food availability and predation risk fluctuate seasonally. Marine zooplankton have evolved a diversity of life history strategies in response to seasonality. We present a state‐dependent life history model for the annual and herbivorous high‐latitude copepodCalanoides acutus. Individuals are characterised by four states; developmental stage, structural size, energy reserves and vertical location. There are two habitats, a surface habitat with seasonal predation risk and food availability, and a safer deep habitat with no food and low metabolism (diapause). Optimal life histories (diapause and energy allocation strategies) are found by dynamic programming. Seasonal egg fitness (reproductive value) emerges from the model and peak values are typically before the feeding season. Disentangling the fitness components, we conclude that seasonality in egg fitness is caused both by environmental seasonality in food and predation risk and by time‐constraints on development and diapause preparation. Realised egg production, as predicted from population simulations, does not match the seasonal peak in offspring fitness but is delayed relative to peak egg fitness. We term this an ‘internal life history mismatch’ as constraints and tradeoffs cause sub‐optimal birth dates for most eggs whereas mothers maximise their reproductive value by high number of eggs rather than few and optimally timed eggs. The earliest eggs have a disproportionately high contribution to population recruitment, emphasising the importance of early eggs and the need to understand seasonal patterns in offspring fitness.

Early release of eggs and embryos in a brooding ancient asexual ostracod: brood selection or a gambling strategy to increase fecundity?

Asexual lineages lack the means to purge their genomes of (deleterious) mutations through recombination. Evolutionary theory thus predicts that such lineages will be prone to early extinction. In brooding animals, brood selection might provide a mechanism to counter the accumulation of mutations. Of the three putative ancient asexual animal groups, only the darwinulid ostracods are brooders. Here, we test the incidence of egg and juvenile abortion in a darwinulid species, Penthesilenula brasiliensis, under two temperature treatments. Part of the offspring is released without brooding (close to 30% in one treatment). The majority of these aborted eggs hatches and develops. As it is unlikely that females are such bad judges of offspring quality, either the surviving animals will present deficiencies later on in development (brood selection) or early egg release can be a (bet-hedging) strategy to increase fecundity in favourable conditions.

Reproductive Performance of Broiler Breeders as Affected by Age at Initiation of Laying Cycle Lighting Program

The control of lighting for broiler breeders is an extremely important aspect of controlling their reproductive performance. The length of light available to broiler breeder hens significantly effects the age at which they begin producing eggs and their subsequent peak egg production levels. Although most broiler breeders in the U.S. are grown in light-tight houses, in many areas of the world they are not and these producers must rely on natural daylight supplemented by artificial lighting. Therefore, it is important to understand the effects of delaying the age of initiation of artificial lighting programs when birds are grown under natural lighting conditions. In this experiment, June-hatched broiler breeders were grown under natural day length and artificial photostimulation was begun at either 18, 20 or 22 weeks of age. The results of this experiment showed that early egg production is decreased significantly in birds in which photostimulation has been delayed until 22 weeks of age. However, this significant decrease did not affect the overall egg production. This study indicated that delaying the artificial photostimulation of June-hatched broiler breeders until 22 weeks of age was not detrimental to their overall performance.

Comparison of surface microfouling and bacterial attachment on the egg capsules of two molluscan species representing Cephalopoda and Neogastropoda

AME Aquatic Microbial Ecology Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials AME 47:275-287 (2007) - doi:10.3354/ame047275 Comparison of surface microfouling and bacterial attachment on the egg capsules of two molluscan species representing Cephalopoda and Neogastropoda Norman S. H. Lim, Kim J. Everuss, Amanda E. Goodman, Kirsten Benkendorff* School of Biological Sciences, Flinders University of South Australia, GPO Box 2100, Adelaide, South Australia 5001, Australia *Corresponding author.Email: kirsten.benkendorff@flinders.edu.au ABSTRACT: Many organisms naturally defend themselves against microbial attachment and biofouling in the marine environment. In this study, we investigated microbial fouling on 2 molluscan egg capsules using scanning electron microscopy (SEM), two-photon laser scanning microscopy (TPLSM) with bacterial viability staining and bacterial attachment experiments with the biofilm-forming Pseudoalteromonas sp. S91 in flow chambers. Results indicated that early stage egg capsules of Dicathais orbita (Neogastropoda) are relatively free of surface microorganisms. Egg capsules during the trocophore stage had a regularly ridged microtexture, but as capsules matured, shedding of the outer wall was observed, followed by the extrusion of unidentified droplets, which then accumulated on the capsule surface in association with bacteria. By comparison, the egg capsules of Sepioteuthis australis (Cephalopoda) were found to have an irregular surface with many hills and valleys that accommodate colonization by a variety of microorganisms. At the later stages of development these squid egg capsules become heavily colonized by algal spores. Cross sections of egg capsules revealed that S. australis capsule walls were about 12 times thicker than D. orbita egg capsules. Staining the egg capsules with BacLight™ also revealed a significantly thicker biofilm, with more live and dead bacteria on S. australis capsules than on those of D. orbita (p < 0.05). Flow chamber experiments indicated that the surface of S. australis capsules provided a suitable substrate for colonization by Pseudoalteromonas sp. S91, whereas colonization was significantly less on D. orbita egg capsules after 24 and 72 h (p < 0.01). These experiments indicated that D. orbita egg capsules are better defended against fouling microbes than are the eggs of S. australis. D. orbita appears to use a combination of physical, mechanical and possibly chemical defense mechanisms to reduce fouling on their egg capsules. KEY WORDS: Biofilm · Egg capsules · Mollusc · Scanning electron microscopy · Two-photon laser scanning microscopy · Bacterial attachment Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in AME Vol. 47, No. 3. Online publication date: May 30, 2007 Print ISSN: 0948-3055; Online ISSN: 1616-1564 Copyright © 2007 Inter-Research.