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Egg Masses (egg + mass)

Distribution by Scientific Domains

Life Sciences	81%
Earth and Environmental Science	16%

Distribution within Life Sciences

Entomology	24%
Animal Science & Zoology	13%
Plant Science	11%
Evolution	6%
Animal Science Methods	3%
8 Other Subdomains	31%

Selected Abstracts

Egg mass and incubation period allometry in birds and reptiles: effects of phylogeny

JOURNAL OF ZOOLOGY, Issue 2 2006
D. C. Deeming
Abstract Here we test the hypothesis that the relationship between egg mass at oviposition (IEM) and incubation period (Ip) is a function of the taxonomic relatedness of bird and reptile species. Allometric relationships between IEM and Ip were examined for 1525 bird species and 201 reptilian species. Treating species as independent data revealed the allometric exponent linking Ip to IEM to be 0.234 for birds and 0.138 for reptiles. However, ANCOVA revealed that within both birds and reptiles the elevation and slope of the regression lines were dependent on the taxonomic order studied, indicating that the exponents were confounded by the phylogenetic relatedness of species. Thus, allometric exponents were recalculated based on the method of comparative analysis using independent contrasts. This technique revealed that the allometric exponent in both birds and reptiles was confounded by phylogeny. In birds the allometric relationship between Ip and IEM was almost halved to 0.122, whereas in reptiles the exponent increased to 0.185. Importantly, the results demonstrate that some results of allometric analyses can be artefacts of the method of analysis of the dataset. That for bird eggs Ip is not determined in large part by egg mass allows new questions to be posed regarding the ecological and physiological factors affecting the length of incubation, and hence rates of embryonic growth, for different taxa and habitats. [source]

Synthesis and function of the fibrous layers covering the eggs of Siphlonurus lacustris (Ephemeroptera, Siphlonuridae)

ACTA ZOOLOGICA, Issue 1 2001
Elda Gaino
Abstract Ultrastructural analysis (transmission and electron scanning microscopy) of the eggs of the mayfly Siphlonurus lacustris (Eaton) showed that they are wrapped in a thick coat composed of a network of tightly entwined filaments. Groups of twisted filaments form slightly uplifted buttons that are scattered on the coat surface. After experimentally induced egg deposition, egg,water interaction promotes marked cohesion of the eggs and their firm adhesion to the substrate. Egg masses include numerous gametes; the covering of those located close to the substrate greatly extends to anchor the whole mass. Eggs removed from the coat reveal a slightly punctuated smooth chorion and tagenoform micropyles (three to five). The coat increases egg size by about 20%. The lack of female reproductive accessory glands in Ephemeroptera transfers the synthesis of the adhesive coats to the follicle cells, which are typically competent for insect egg shell deposition (vitelline envelope and chorionic layers). This covering results from electron-dense granules that give rise to filaments progressively organized to form superimposed layers variously orientated around the egg. In addition to egg adhesion to the substrate, a trophic function and protection from shear stress are postulated for this covering. [source]

Effects of the synthetic estrogen ethinylestradiol on early life stages of mink frogs and green frogs in the wild and in situ

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2005
Bradley J. Park
Abstract Estrogenic contaminants are known to disrupt growth and development in amphibians. Field-based research is needed to elucidate their potential impacts on wild populations. Hatch success, larval growth and development rates, and gonad development were examined in native amphibians exposed to low ng/L concentrations of 17,-efhinylestradiol (EE2) in a whole-lake addition experiment at the Experimental Lakes Area, northwestern Ontario, Canada. Egg masses were reared in situ in the EE2-amended lake and in two reference lakes in 2001 and 2002. Hatching success was reduced significantly in green frogs (Rana clamitans) but not in mink frogs (Rana septentrionalis) exposed to EE2. Ethinylestradiol had no consistent effect on mass or development stage of hatchlings in the early larval stages of the caging study. Ethinylestradiol had no effect on sex ratios of either species in situ, and no intersex gonads were observed in exposed or reference green frog tadpoles or in reference mink frog tadpoles. However, 5.6% (total n = 18) and 12.5% (total n = 56) of EE2-exposed mink frog tadpoles were intersex in the 2001 and 2002 caging studies, respectively. Wild mink frog tadpoles also were examined, and EE2 had no effect on sex ratios. No intersex gonads were observed in reference lake tadpoles or in tadpoles from the experimental lake prior to EE2 additions; however, 2.4, 0, and 28.6% of wild EE2-exposed first-year tadpoles had intersex gonads (2001, 2002, and 2003, respectively). These results indicate that exposure to EE2 in the wild and in situ at concentrations comparable to those detected in effluents and, occasionally, in surface waters can impact gonad development and hatch success in native amphibians. [source]

Adverse effect of the chitinolytic enzyme PjCHI-1 in transgenic tomato on egg mass production and embryonic development of Meloidogyne incognita

PLANT PATHOLOGY, Issue 5 2010
Y.-L. Chan
A novel chitinase gene (PjCHI-1) isolated from Paecilomyces javanicus, a non-nematophagous fungus, and driven by a CaMV35S promoter, was delivered into CLN2468D, a heat-tolerant cultivar of tomato (Solanum lycopersicum). T1 tomato plants exhibited high endochitinase activity and reduced numbers of eggs and egg masses when infected with the root-knot nematode (RKN) Meloidogyne incognita. The eggs found in transgenic tomato had lower shell chitin contents than eggs collected from control plants. Egg masses from transgenic plants exhibited higher chitinase activity than those from control plants. Moreover, only 30% of eggs from transgenic plants were able to develop to the multi-cell/J1 stage, compared with more than 96% from control plants. The present study demonstrated that the expression of the PjCHI-1 chitinase gene can effectively reduce the production of egg masses and repress the embryonic development of M. incognita, presenting the possibility of a novel agro-biotechnological strategy for preventing crop damage by RKN. [source]

Reproductive Investment of a Lacertid Lizard in Fragmented Habitat

CONSERVATION BIOLOGY, Issue 5 2005
JOSÉ A. DÍAZ
calidad de hábitat; fragmentación de bosque; Psammodromus; tamaño de puesta; tamaño de huevo Abstract:,We studied the effect of habitat fragmentation on female reproductive investment in a widespread lacertid lizard ( Psammodromus algirus) in a mixed-forest archipelago of deciduous and evergreen oak woods in northern Spain. We captured gravid females in fragments (,10 ha) and forests (, 200 ha) and brought them to the laboratory, where they laid their eggs. We incubated the eggs and released the first cohort of juveniles into the wild to monitor their survival. Females from fragments produced a smaller clutch mass and laid fewer eggs (relative to mean egg mass) than females of similar body size from forests. Lizards did not trade larger clutches for larger offspring, however, because females from fragments did not lay larger eggs (relative to their number) than females from forests. Among the first cohort of juveniles, larger egg mass and body size increased the probability of recapture the next year. Thus, fragmentation decreased the relative fecundity of lizards without increasing the quality of their offspring. Reduced energy availability, increased predation risk, and demographic stochasticity could decrease the fitness of lizards in fragmented habitats, which could contribute to the regional scarcity of this species in agricultural areas sprinkled with small patches of otherwise suitable forest. Our results show that predictable reduction of reproductive output with decreasing size of habitat patches can be added to the already known processes that cause inverse density dependence at low population numbers. Resumen:,Estudiamos el efecto de la fragmentación sobre la inversión reproductiva de hembras en una lagartija lacértida ( Psammodromus algirus) ampliamente distribuida en un archipiélago mixto de bosques deciduos y siempre verdes de roble en el norte de España. Capturamos hembras grávidas en fragmentos (, 10 ha) y en bosques (, 200 ha) y las trasladamos al laboratorio, donde pusieron sus huevos. Incubamos los huevos y liberamos a la primera cohorte de juveniles para monitorear su supervivencia. Las hembras de fragmentos produjeron una puesta de menor masa y pusieron menos huevos (en relación con la masa promedio de los huevos) que hembras con talla corporal similar provenientes de bosques. Sin embargo, las lagartijas no cambiaron puestas mayores por crías más grandes porque las hembras de fragmentos no pusieron huevos más grandes (en relación con su número) que las hembras de bosques. Entre las primeras cohortes de juveniles, la mayor masa de los huevos incrementó la probabilidad de recaptura en el siguiente año. Por lo tanto, la fragmentación redujo la fecundidad relativa de las lagartijas sin aumentar la calidad de sus crías. La disponibilidad reducida de energía, el incremento en el riesgo de depredación y la estocasticidad demográfica podrían disminuir la adaptabilidad de lagartijas en hábitats fragmentados, lo que podría contribuir a la escasez regional de esta especie en áreas agrícolas salpicadas de pequeños parches de bosque por lo demás adecuado. Nuestros resultados muestran que la reducción predecible en la reproducción al disminuir el tamaño de los parches de hábitat se puede agregar a los procesos ya conocidos que causan la inversión de la denso dependencia en tamaños poblacionales pequeños. [source]

Post-gall induction performance of Adelges Abietis (L.) (Homoptera: Adelgidae) is influenced by clone, shoot length, and density of colonising gallicolae

ECOLOGICAL ENTOMOLOGY, Issue 1 2010
LEAH FLAHERTY
1. We evaluated the effect of clone (one susceptible and one resistant clone), shoot length, crown level, and gallicola density on post-gall induction performance of Adelges abietis. Galls that had been successfully induced by one fundatrix on a range of shoot sizes were selected, and the number of gallicolae that could colonise the gall was manipulated. 2. Post-induction gall development success was inversely related to shoot length and was higher on the susceptible clone than on the resistant clone. As gallicola density did not influence the proportion of galls that successfully completed development, reduced post-induction gall development on large shoots was not likely to be result of an insufficient stimulus from gallicolae. 3. Clone was the only factor that significantly influenced gall volume and galls were larger on the susceptible clone than on the resistant clone. As gall volume did not increase when more gallicolae attempted to colonise a gall, competition within a gall increased. Gallicola survival was inversely related to the number of colonising gallicolae. Our results suggest that gall size may be limiting at natural densities. 4. Previous studies report positive relationships between gall induction success and fundatrix density, and between gall size and fundatrix density. As each fundatrix produces one egg mass of gallicolae, this study suggests that there may be a trade-off between the successful induction of a large gall and subsequent survival of gallicolae. 5. In the present study, clone influenced all measures of post-gall induction performance. Performance was always higher on the susceptible than on the resistant clone. [source]

Brochosome influence on parasitisation efficiency of Homalodisca coagulata (Say) (Hemiptera: Cicadellidae) egg masses by Gonatocerus ashmeadi Girault (Hymenoptera: Mymaridae)

ECOLOGICAL ENTOMOLOGY, Issue 5 2005
Hans-Paul Velema
Abstract., 1.,Many cicadellid females in the tribe Proconiini (Hemiptera: Cicadellidae) cover their egg masses with specialised, usually rod-shaped, brochosomes as the eggs are being laid. The brochosomes are produced in Golgi complexes in the Malpighian tubules of Cicadellidae. In contrast to the gravid females, adult males, pre-reproductive adult females, and nymphal males and females produce specialised, usually spherically shaped brochosomes. Brochosomes are also used to cover the external surfaces of nymphs and newly moulted adult males and females. 2.,The function of the brochosome covering the egg masses is unknown but various hypotheses have been suggested, including protecting the eggs against pathogens, predators, and parasitoids. Based on preliminary observations of Gonatocerus ashmeadi Girault (Hymenoptera: Mymaridae) parasitising the eggs of the cicadellid, Homalodisca coagulata (Say), it is speculated here that brochosomes covering an egg mass hinder parasitisation of eggs by G. ashmeadi. This hypothesis was tested by observing G. ashmeadi females foraging on leaves with H. coagulata egg masses heavily covered with rod-shaped brochosomes vs. those lacking brochosomes. 3.,Cox's proportional hazards model was used to evaluate the probability, per unit time, that a female G. ashmeadi displayed the sequence of behaviours that ended in successful oviposition as influenced by five variables: (a) presence or absence of brochosomes on an egg mass, (b) the leaf surface, upper or lower, being searched by the parasitoid (the egg masses are laid in the parenchyma on the lower leaf surface), (c) the parasitoid's previous ovipositional experience, (d) egg mass size, and (e) the parasitoid's age. 4.,Brochosomes significantly decreased oviposition efficacy of G. ashmeadi females. Scanning electron microscopy showed that females exposed to brochosome-covered egg masses had brochosomes adhering to their tarsi, legs, antennae, and eyes, all of which prompted extensive bouts of grooming. [source]

Effects of an organophosphorous insecticide on survival, fecundity, and development of Hylyphantes graminicola (Sundevall) (Araneae: Linyphiidae)

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 11 2006
Lingling Deng
Abstract The effects of an organophosphorous insecticide, methamidophos, on fecundity and development of the spider Hylyphantes graminicola (Sundevall) (Araneae: Linyphiidae) were assessed under laboratory conditions. Susceptibility of adults of both sexes to the insecticide and its influence on fecundity of females and development of offspring were investigated. At 48 h after topical application in adults, the median lethal dose (LD50) and 10% lethal dose (LD10) were 0.35 and 0.12 ,g/spider, respectively, for males and 0.52 and 0.16 ,g/spider, respectively, for females. Methamidophos had detrimental effects on fecundity of females; number of eggs per clutch, total egg mass, and clutch size decreased significantly. The hatching rate of eggs from LD10-treated females was slightly higher than the rate in the controls, but the hatching rate of eggs from LD50-treated females was lower than the rate in the controls. However, no significant differences were observed in hatching time and development time across treatments. Development time of spiderlings from LD50-treated females was significantly longer than the time in the controls, and body sizes of the first spiderlings from insecticide-treated females were larger than those in the controls. However, matured offspring were smaller than those in the controls. It was concluded that methamidophos has long-term effects on H. graminicola, and that this may affect the development of spider populations in the field. [source]

Trophic Egg Production in a Subsocial Shield Bug, Parastrachia japonensis Scott (Heteroptera: Parastrachiidae), and its Functional Value

ETHOLOGY, Issue 12 2005
Mantaro Hironaka
Females of the gregarious shield bug, Parastrachia japonensis Scott (Heteroptera: Parastrachiidae) engage in extensive parental care behaviors that include egg and nymph guarding and progressive provisioning of drupes of the solitary host tree, Schoepfia jasminodora (Olacaceae: Rosidae: Santales). We noted that some eggs in every egg mass failed to turn pink and develop eye-spots indicative of developing embryos, suggesting that they are infertile, and therefore non-viable. We also observed newly hatched nymphs probing, and presumably feeding, on the egg mass remains. In the present report, through field observations and experiments involving removal of these non-viable eggs in the laboratory, we demonstrate that their presence is correlated with significant increases in nymphal weight, developmental rate and survival in the absence of other food. Thus, we conclude that an additional manifestation of the parental care behaviors that P. japonensis females use to increase their reproductive success is the production of trophic eggs. Some physical traits of the trophic eggs and their functional role in this system are discussed in the context of our current theoretical understanding of extended parental care. [source]

Egg carotenoids in passerine birds introduced to New Zealand: relations to ecological factors, integument coloration and phylogeny

FUNCTIONAL ECOLOGY, Issue 4 2005
P. CASSEY
Summary 1Carotenoids are a diverse group of organic compounds that function as important antioxidants and immunostimulants and are of particular importance to developing embryos and young birds. In addition, they constitute the majority of yellow to red hues in the integumentary pigments of birds. 2We investigated the maternally derived carotenoid concentrations and balances in the yolks of eight European passerine species successfully introduced and abundant in New Zealand. Specifically, we addressed whether variation in maternally derived yolk carotenoids were related to phylogeny, integument coloration, native vs introduced distribution, breeding habitat and laying sequence. 3Across species, the concentration and balance of carotenoids deposited in yolks varied significantly. Egg carotenoid concentration was positively associated with the occurrence of male carotenoid pigmented body regions. Carotenoid concentrations differed between agricultural habitat types within New Zealand but not between samples from New Zealand and Europe. Controlling for the differences among species, and among clutches within species, increased egg carotenoid concentrations were significantly associated with decreasing fresh egg mass and eggs laid earlier in the laying sequence. 4We conclude that variability in the concentration and balance of carotenoids deposited in the egg yolk imply different relative roles for ecological and phylogenetic factors that warrant further investigation, both within and across species. [source]

Density effects on life-history traits in a wild population of the great tit Parus major: analyses of long-term data with GIS techniques

JOURNAL OF ANIMAL ECOLOGY, Issue 2 2006
TEDDY A. WILKIN
Summary 1Population density often has strong effects on the population dynamics and reproductive processes of territorial animals. However, most estimates of density-dependent effects use the number of breeding pairs per unit area in a given season and look for correlations across seasons, a technique that assigns the same density score to each breeding pair, irrespective of local spatial variation. 2In this study, we employed GIS techniques to estimate individual breeding densities for great tits breeding in Wytham Woods UK, between 1965 and 1996. We then used linear mixed modelling to analyse the effect of density on reproductive processes. 3The areas of Thiessen polygons formed around occupied nestboxes were used to approximate territory size (necessarily inverse of breeding density). There were significant, independent and positive relationships between clutch size, fledging mass and the number of offspring recruited to the population, and territory size (all P < 0·001), but no effect of territory size on lay-date or egg mass. 4Thiessen polygons are contiguous and cover all of the available area. Therefore, at low nest densities territory polygons were excessively oversized. Using a novel procedure to address this limitation, territory sizes were systematically capped through a range of maxima, with the greatest effect in the models when territories were capped at 0·9,2·3 ha. This figure approximates to the maximum effective territory size in our population and is in close agreement with several field-based studies. This capping refinement also revealed a significant negative relationship between lay-date and territory size capped at 0·9 ha (P < 0·001). 5These density-dependent effects were also detected when analyses were restricted to changes within individual females, suggesting that density effects do not merely result from either increased proportions of low-quality individuals, or increased occupation of poor sites, when population density is high. 6Overall, these results suggest that, in the current population, great tits with territories smaller than c. 2 ha independently lay smaller and later clutches, have lighter fledglings, and recruit fewer offspring to the breeding population. These analyses thus suggest a pervasive and causal role of local population density in explaining individual reproductive processes. [source]

Butterfly life history and temperature adaptations; dry open habitats select for increased fecundity and longevity

JOURNAL OF ANIMAL ECOLOGY, Issue 1 2005
BENGT KARLSSON
Summary 1Evidence suggests that changes of temperature-related performance curves can trigger a selective response in life-history traits. Hence, it should be expected that insects adapted to different temperature regimes should exhibit optimal performance at the temperature to which they are adapted. 2To test this idea we investigated how fecundity and longevity are influenced by ambient temperatures in a set of satyrine butterflies adapted to live in dry open landscapes or in closed forest landscapes, respectively, by keeping egg-laying adult females at five different constant temperatures ranging between 20 and 40 °C. 3We studied four species, two of which are confined to dry and hot open habitats, namely the grayling (Hipparchia semele) and the small heath (Coenonympha pamphilus), and two of which are shade dwelling, namely the ringlet (Aphantopus hyperantus) and the speckled wood butterfly (Pararge aegeria). 4As predicted, the results showed that lifetime fecundity exhibited bell-shaped curves in relation to temperature with the open landscape group peaking at a higher temperature, 30 °C, compared with the shade-dwelling group that peaked at 25 °C. Longevity decreased with increasing temperatures among all species, but the open landscape living species survived better at higher temperatures. Moreover, although the magnitude of reproductive effort measured as lifetime egg mass did not differ between the two ecological groups, lifetime fecundity did with open landscape species laying more and smaller eggs than the shade-dwelling species. 5This difference in life-history character traits suggests either that dry and relatively warm open habitats open life-history opportunities in terms of higher fecundity and longevity that remain closed to butterflies adapted to cooler temperatures, or that life in dry open habitats actively selects for higher fecundity and survival as a result of increased offspring mortality. [source]

Intrapopulation variation in reproduction by female eastern kingbirds Tyrannus tyrannus: the impacts of age, individual performance, and breeding site

JOURNAL OF AVIAN BIOLOGY, Issue 3 2004
Michael T. Murphy
I used data from a 13-year study of eastern kingbirds Tyrannus tyrannus from central New York, USA, to evaluate the relative impact of female age and body size on reproduction. I also calculated repeatabilities of reproductive traits for both females and the sites where they bred in an attempt to evaluate the relative contribution of each to intrapopulation variation in reproduction. Female age had a strong influence on timing of breeding (breeding date advanced by one day for each year of life), but was not a significant source of variation for clutch size, egg mass, number of young to hatch or fledge, or total seasonal production. Repeatabilities of breeding date for females and sites were both significant (0.284 and 0.181, respectively), but the only other significant repeatabilities were for female clutch size (0.282) and female egg mass (0.746). Among-year repeatabilities of breeding date for females who bred at two or more sites over their lifetime were as high as those for females that were site faithful. Thus, breeding date was probably affected independently by the female and site. No measure of productivity exhibited a repeatable pattern in comparisons made among females or sites. All reproductive traits were entered as dependent variables in a series of stepwise multiple regression analyses in an attempt to identify female properties (size, lifespan and condition) that might be linked proximately to differences in breeding statistics. I found that (a) large birds tended to breed the earliest, (b) clutch size was independent of female size, condition and lifespan, (c) female body size and egg size were correlated positively, but (d) production of young was independent of all measured female properties. Reproduction appears to be linked more closely to the female than to the site. Body size accounts for a portion of the repeatable portion of breeding date and egg mass, but most of the intrapopulation variation in these and other traits remained unexplained. [source]

Multiple pathways of maternal effects in black-headed gull eggs: constraint and adaptive compensatory adjustment

JOURNAL OF EVOLUTIONARY BIOLOGY, Issue 4 2006
T. G. G. GROOTHUIS
Abstract We investigated in the black-headed gull whether female deposition of antioxidants and immunoglobulins (enhancing early immune function), and testosterone (suppressing immune function and increasing early competitive skills) correlate suggesting that evolution has favoured the mutual adjustment of different pathways for maternal effects. We also took egg mass, the position of the egg in the laying sequence and offspring sex into account, as these affect offspring survival. Yolk antioxidant and immunoglobulin concentrations decreased across the laying order, while yolk testosterone concentrations increased. This may substantially handicap the immune defence of last-hatched chicks. The decrease in antioxidant levels was greater when mothers had a low body mass and when the increase in testosterone concentrations was relatively large. This suggests that female black-headed gulls are constrained in the deposition of antioxidants in last-laid eggs and compensate for this by enhanced testosterone deposition. The latter may be adaptive since it re-allocates the chick's investment from costly immune function to growth and competitive skills, necessary to overcome the consequences of hatching late from an egg of reduced quality. [source]

Using net sacks to examine the relationship between egg size and young size in Common Pochards

JOURNAL OF FIELD ORNITHOLOGY, Issue 3 2007
David Ho
ABSTRACT Investigators studying the relationship between egg size and young size often face difficulties in assigning particular young to particular eggs. We present a new method based on the use of separate net sacks for each egg that allowed us to study this phenomenon in Common Pochards (Aythya ferina) without excessive disturbance of breeding birds. We found a positive isometric relationship between duckling body mass and estimated fresh egg mass (P < 0.001). However, we found no relationship between estimated fresh egg mass and structural measurements of ducklings (tarsus and bill length, both P > 0.29). In addition, we found a weak positive relationship between estimated egg mass and the size of ducklings (P= 0.049). Greater hatchling mass typically means a larger yolk supply, and more yolk may provide energy crucial for survival during the first few days after hatching. In addition, ducklings with longer tarsi may be better swimmers and better at finding food and escaping from predators. Although our method has certain limitations and investigators should consider risks when applying it in over-water nests or in nests with large clutches, we believe it is a reliable way to assign young to particular eggs in waterfowl and possibly other bird species. SINOPSIS Los investigadores que estudian la relación entre el tamaño del huevo y el tamaño de los pichones se han encontrado con la dificultad de asignar un pichón a un huevo en particular. Presentamos un nuevo método basado en el uso individual de sacos de redes (para cada huevo), que nos ha permitido estudiar el fenómeno en Aythya ferina, sin causar gran disturbio a la reproducción de las aves. Encontramos una relación isométrica positiva entre la masa del patito y el estimado de la masa del huevo fresco (P < 0.001). Sin embargo, no encontramos una relación apropiada, entre la masa fresca del huevo y medidas estructurales en los patitos (ej. longitud del tarso y el pico, ambos con P > 0.29). Además, encontramos una relación positiva, pero débil, entre el estimado de la masa del huevo y el tamaño del patito (P= 0.049). Al eclosionar, una mayor masa del patito, significa una mayor cantidad de yema. Una mayor cantidad de esta pudiera proveer de mayor cantidad de energía la que a su vez pudiera ser crucial para la sobrevicencia durante los primeros dias. En adición, patitos con tarsos de mayor tamaño pudieran ser mejores nadadores, y más capaces de encontrar alimento y escapar de depredadores. Aunque nuestro método tiene limitaciones (y los investigadores debieran considerar el riesgo de aplicar el método en nidos sobre agua o en nidos con grandes camadas), creemos que es una forma confiable de asignar un neonato a un huevo particular, tanto a aves acuática como posiblemente a otras especies. [source]

Effect of dietary cortisol administration on growth and reproductive success of channel catfish

JOURNAL OF FISH BIOLOGY, Issue 3 2004
B. C. Small
The effect of cortisol administration on reproductive performance was investigated in channel catfish Ictalurus punctatus broodfish. Cortisol was added to a commercial catfish feed by dissolving in ethanol and spraying the feed to yield a dietary concentration of 150 mg kg,1 feed. The cortisol diet and the control (no cortisol) diet were offered at a rate of 1% of biomass to three replicate ponds each containing 28 female and 14 male broodfish, respectively, three times per week for 11 weeks. Spawning began 10 days after the start of the experiment, and continued for 10 weeks. In fish fed cortisol, body mass and the hepato-somatic index were reduced (P , 0·02) and concentrations of plasma cortisol and glucose were significantly higher (P , 0·0003) compared to those of controls. The relative frequency of spawning was similar between the two treatments; however, cortisol-fed channel catfish had an average of 47·1% more spawns than the control-fed fish. On average, there were 25·5 spawns per pond in the treated groups compared to 12·3 spawns per control pond (P = 0·10). No effect was observed on egg production, with individual egg mass, fecundity, and hatching success being similar (P , 0·27) for both treatments. Despite the observed negative effects of cortisol on somatic and hepatic growth, the increased reproductive output coupled with no observable effects on the eggs or hatching success demonstrates that cortisol does not suppress channel catfish reproduction. [source]

Resistance of perch eggs to attack by aquatic fungi

JOURNAL OF FISH BIOLOGY, Issue 3 2000
C. G. M. Paxton
In the distinctive gelatinous Perca fluviatilis egg mass, limited fungal growth by Aphanomyces and Saprolegnia spp. especially S. diclina, occurred within dead eggs but did not spread to adjacent live eggs. Perch eggs exposed to parasitic challenge by Saprolegnia parasitica, S. dieclina (type III) and S. ferax, under fluctuating temperature regimes replicating spring water temperatures, did not have significantly greater mortality than did unchallenged controls. The observations suggest that perch eggs have some anti-fungal properties which usually prevent the spread of fungus throughout the egg mass and that under normal spring temperatures there should be negligible ecological consequences of fungal infection in perch egg masses. [source]

Egg mass and incubation period allometry in birds and reptiles: effects of phylogeny

The odour of pyrazine increases the egg mass of domestic chickens (Gallus gallus domesticus L.)

JOURNAL OF ZOOLOGY, Issue 3 2002
Anat Barnea
Abstract Forty leghorn chickens at the commencement of egg laying, were divided into two groups, each with 10 females and 10 males. One group was exposed to the odour of synthetic pyrazine (2-methoxy-3-isobutylpyrazine) for 16 weeks while the other acted as a control. During the first 4 weeks the hens exposed to pyrazine odour laid significantly fewer eggs (unfertilized) than the controls, but thereafter both groups laid a similar number. Mean egg mass of the pyrazine exposed hens was significantly (P= 0.012) greater (5.5%) than that of the control group. No significant difference was found in body mass or eggshell thickness. Similarly, there were no consistent significant differences between groups in oestrogen and testosterone concentrations in the blood of females and males, respectively. No pyrazine could be detected in cloacal extracts. The experiment shows that an external odour can affect the internal reproductive system of the chicken. It is suggested that the pyrazine-engendered increase in egg mass involves neuroendocrine regulation within the hypothalamus rather than hormonal interactions ,downstream' of the brain. [source]

Competition and intraguild egg predation among freshwater snails: re-examining the mechanism of interspecific interactions

OIKOS, Issue 11 2007
Andrew M. Turner
Experimental and field studies suggest that freshwater snail species have negative effects on each other's population growth rates. Because snails share similar diets, these interactions have been interpreted as the result of exploitative competition, but they could also result from intraguild predation. Here we present three experiments aimed at testing the hypothesis that interspecific interactions among three species of freshwater gastropod (Helisoma trivolvis, Physa acuta and Stagnicola elodes) are mediated by intraguild egg predation. Foraging trials, conducted in a laboratory, showed that some snails readily prey on eggs, but the extent of egg predation depended on both the identity of the snail predator and the identity of the egg mass. Of the three species considered, Stagnicola had the largest effect on egg mortality and Physa had no effect on egg mortality. Foraging trials also showed that the eggs of Physa were the most vulnerable to predators and that the eggs of Stagnicola were largely invulnerable. A study conducted in large outdoor mesocosms assessed the occurrence of egg mortality in an environment of more extensive spatial scale and complexity. The results largely mirrored those of the laboratory study, with Stagnicola being the most voracious predator and the eggs of Physa being most vulnerable to predation. The reproductive success of Physa and Stagnicola raised in sympatry and allopatry was assessed in a mesocosm study conducted over three months. Recruitment of both species was depressed in sympatry, but patterns of growth in the survivors suggest contrasting mechanisms of suppression: Physa suppressed Stagnicola via exploitative competition, but Stagnicola suppressed Physa via egg predation. These experiments support the hypothesis that freshwater snail assemblages are structured by strong interspecific interactions and that a rich interplay of egg predation and interspecific competition underlie interactions among the members of this guild. [source]

Comparison of ion transportation before and after egg hatching in Amphinemura sp. (Plecoptera)

PHYSIOLOGICAL ENTOMOLOGY, Issue 4 2006
MAYUMI YOSHIMURA
Abstract An increase in egg size with embryonic development in stoneflies is believed to result from the uptake of water by osmosis. The present study aims to investigate whether a selective ion transport through egg membranes exists before hatching, and whether ions are released after hatching. Viable and nonviable egg masses are incubated in Petri dishes filled with water, and the concentrations of the ions F,, Cl,, SO42,, NO3,, Na+, K,, Mg2+ and Ca2+ in the water are determined. The ion transport of an egg mass before and after hatching and a nonviable egg mass is then calculated. Before hatching, Cl,, SO42,, NO3,, Na+, Mg2+ and Ca2+ are taken up from the surrounding water into the inner egg. These ions are selectively taken into the egg. After hatching, Cl,, SO42,, Na+, Mg2+ and Ca2+ are released into the surrounding water. The amount of these ions released after hatching is lower than the amount taken up before hatching. Ions that are not released after hatching are considered to be used in embryonic development. [source]

Effects of feeding fermented fish on egg cholesterol content in hens

ANIMAL SCIENCE JOURNAL, Issue 1 2009
Teck-Chwen LOH
ABSTRACT This study was conducted to investigate the effects of feeding fermented fish (FF) to layers on laying performance, and polyunsaturated fatty acid and cholesterol levels in eggs and plasma. A total of 96, 13-week-old Babcock B380 pullets were used in this study. They were randomly assigned to four numerically equal groups with eight replicates per treatment, three birds per replicate. All the birds were housed in individual cages. The dietary treatments were: Control diet, without FF; FF3 diet containing 3% (w/w) FF, FF6 diet containing 6% (w/w) FF and FF9 diet containing 9% (w/w) FF. The study was carried out for 16 weeks inclusive of two weeks of adjustment. Weekly feed intake and egg production were recorded. Blood plasma cholesterol and fatty acid profiles were assayed at the end of the experiment. FF did not enhance (P > 0.05) egg mass but (P < 0.05) decreased egg weight slightly. However, egg yolk cholesterol and plasma cholesterol concentrations were reduced (P < 0.05) by FF. The n-6:n-3 fatty acids ratio in the egg yolk (Control = 7.9, FF9 = 6.2) and plasma (Control = 10.6, FF9 = 6.2) were decreased by feeding FF. Moreover, FF was able to increase (P < 0.05) the docosahexaenoic acid (DHA) concentrations in egg yolk and plasma. In conclusion, this study demonstrated that FF increased DHA and reduced egg yolk cholesterol in poultry eggs. [source]

Evolutionary significance of fecundity reduction in threespine stickleback infected by the diphyllobothriidean cestode Schistocephalus solidus

BIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 4 2010
DAVID C. HEINS
Parasites may cause fecundity reduction in their hosts via life-history strategies involving simple nutrient theft or manipulation of host energy allocation. Simple theft of nutrients incidentally reduces host energy allocation to reproduction, whereas manipulation is a parasite-driven diversion of energy away from host reproduction. We aimed to determine whether the diphyllobothriidean cestode parasite Schistocephalus solidus causes loss of fecundity in the threespine stickleback fish (Gasterosteus aculeatus) through simple nutrient theft or the manipulation of host energy allocation. In one stickleback population (Walby Lake, Matanuska-Susitna Valley, Alaska), there was no difference in the sizes and ages of infected and uninfected reproducing females. Lightly- and heavily-infected females produced clutches of eggs, but increasingly smaller percentages of infected females produced clutches as the parasite-to-host biomass ratio (PI) increased. Infected, clutch-bearing sticklebacks showed reductions in clutch size, egg mass, and clutch mass, which were related to increases in PI and reflected a reduction in reproductive parameters as growth in parasite mass occurs. The findings obtained for this population are consistent with the hypothesis of simple nutrient theft; however, populations of S. solidus in other regions may manipulate host energy allocation. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 835,846. [source]

Brochosome influence on parasitisation efficiency of Homalodisca coagulata (Say) (Hemiptera: Cicadellidae) egg masses by Gonatocerus ashmeadi Girault (Hymenoptera: Mymaridae)

Dispersal capacity in the Mediterranean corn borer, Sesamia nonagrioides

ENTOMOLOGIA EXPERIMENTALIS ET APPLICATA, Issue 1 2004
M. Eizaguirre
Abstract Corn (Zea mays L.) borers are the primary target of Bacillus thuringiensis Berliner (Bt) transgenic maize. Management of corn borer resistance to Bt requires information on larval and adult dispersal capacities, a feature that is particularly unknown in Sesamia nonagrioides Lefèbvre (Lepidoptera: Noctuidae), the most damaging corn borer in Spain. Larval dispersal was studied over a 3 year period by infesting plants with egg masses and dissecting the neighbouring plants 7, 14, and 32 days later to measure larval dispersal at several ages. The number and age of larvae were recorded in the dissected plants. Only mature larvae dispersed in significant numbers; they moved at least to rows adjacent to those containing the infested plant, and down the row five plants. The percentage of larvae that dispersed from the infested plant was density-dependent. Adult dispersal was studied with directional light and pheromone uni-traps over 5 and 3 year periods, respectively. Directional light traps were placed in the margins between Bt and non-Bt maize fields, half oriented towards each of the two kinds of maize field. Pheromone traps were placed in the Bt and non-Bt fields at increasing distances (0,100 m) from the border. The numbers of males and females caught in directional light traps were not different in traps oriented towards Bt or non-Bt fields, but the number of males caught in the third flight in Bt fields was lower than in non-Bt fields. These results suggest that males from adjacent Bt and non-Bt fields mate indiscriminately with females emerging in any of the two kinds of maize fields. However, male movement in the third flight may not be sufficient to randomly distribute males between the two fields. [source]

Effect of Plant Factors, Sugar Contents, and Control Methods on the Top Borer (Scirpophaga nivella F.) Infestation in Selected Varieties of Sugarcane

ENTOMOLOGICAL RESEARCH, Issue 3 2005
Abdul KHALIQ
ABSTRACT Sugarcane (Saccharum officinarum L.) varieties CP-43/33 and L-118 susceptible, BF-162 and SPSG-26 resistant while CP-72/2086 as intermediate were screened for studies on top borer, Scirpophaga nivella Fabricus (Pyralidae: Lepidoptera). Morpho-physio chemical plant factors as well as quality of sugar were examined to elucidate the relationship between pest infestations. The observations on leaf thickness 0.735* and moisture contents 0.771* showed positive and significant correlation with the pest infestation at tillering stage. Total minerals, manganese and copper contents did not show significant correlation with the pest infestation, whereas nitrogen, potassium, calcium, magnesium and ferrous contents manifested positive and significant correlation with the pest infestation. Phosphorous, carbohydrates, fats and zinc produced significant and adverse effect on the pest infestation at tillering stage. Zinc contents with contrasting behaviors appeared to be the most important character with co-efficient value of 0.764 followed by ferrous with positive sign. The effect of borer infestation was significantly negative on pol (sucrose), Brix contents (total soluble solids), and CCS (commercial cane sugar). The coefficient of determination value was 0.821, obtained by computing fiber content, pol, Brix and CCS factors together for multivariate regression models. Application of trash mulching at the time of sowing proved to be the most effective treatment with minimum infestation (3.91%) of borer and maximum protection level (62.87%) followed by Furadan®, removal of dead hearts + spike thrust, hand collection of egg masses, and cutting of shoots at 15 days interval. [source]

The association between non-biting midges and Vibrio cholerae

ENVIRONMENTAL MICROBIOLOGY, Issue 12 2008
Meir Broza
Summary Vibrio cholerae is a natural inhabitant of aquatic ecosystems, yet its interactions within this habitat are poorly understood. Here we describe the current knowledge on the interaction of V. cholerae with one group of co-inhabitants, the chironomids. Chironomids, non-biting midges (Chironomidae, Diptera), are an abundant macroinvertebrate group encountered in freshwater aquatic habitats. As holometabolous insects, chironomids start life when their larvae hatch from eggs laid at the water/air interface; through various feeding strategies, the larvae grow and pupate to become short-lived, non-feeding, adult flying insects. The discovery of the connection between V. cholerae and chironomids was accidental. While working with Chironomus transavaalensis, we observed the disintegration of its egg masses and searched for a possible microbial agent. We identified V. cholerae as the primary cause of this phenomenon. Haemagglutinin/protease, a secreted extracellular enzyme, degraded the gelatinous matrix surrounding the eggs, enabling bacterial growth. Observation of chironomids in relation to V. cholerae continuously for 7 years in various types of water bodies in Israel, India, and Africa revealed that environmental V. cholerae adhere to egg-mass surfaces of various Chironomini (,bloodworms'). The flying adults' potential to serve as mechanical vectors of V. cholerae from one water body to another was established. This, in turn, suggested that these insects play a role in the ecology of V. cholerae and possibly take part in the dissemination of the pathogenic serogroups during, and especially between, epidemics. [source]

Induction of morphological deformities in Chironomus tentans exposed to zinc- and lead-spiked sediments

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 11 2001
Edward A. Martinez
Abstract Laboratory experiments were used to assess morphological responses of Chironomus tentans larvae exposed to three levels of zinc and lead. Chironomus tentans egg masses were placed into triplicate control and metal-spiked aquaria containing the measured concentrations 1,442, 3,383, and 5,562 ,g/g Pb dry weight and 1,723, 3,743, and 5,252 ,g/g Zn dry weight. Larvae were collected at 10-d intervals after egg masses were placed in aquaria until final emergence. Larvae were screened formouthpart deformities and metal body burdens. Deformities increased with time of exposure in both Zn and Pb tanks. Deformity rates between the three Zn concentrations differed statistically, with low and medium Zn levels containing the highest overall deformity rates of 12%. Deformity rates for larvae held in the Pb aquaria were found to differ significantly. Larvae in the low-Pb tanks had a deformity rate of 9%. Larvae and water from both the Zn and Pb aquaria had increasing metal concentrations with increasing sediment metal concentration. Results demonstrate that Zn and Pb each induce chironomid mouthpart deformities at various concentrations. However, a clear dose-related response was not demonstrated. Our research provides more support for the potential use of chironomid deformities as a tool for the assessment of heavy metal pollution in aquatic systems. [source]

Dependent population dynamics between chironomids (nonbiting midges) and Vibrio cholerae

FEMS MICROBIOLOGY ECOLOGY, Issue 1 2006
Malka Halpern
Abstract Vibrio cholerae, the causative agent of cholera, is a natural inhabitant of the aquatic ecosystem. Chironomid (nonbiting midges) egg masses were recently found to harbour V. cholerae non-O1 and non-O139, providing a natural reservoir for the cholera bacterium. Chironomid populations and the presence of V. cholerae in chironomid egg masses were monitored. All V. cholerae isolates were able to degrade chironomid egg masses. The following virulence associated genes were detected in the bacterial isolates: hapA (100%), toxR (100%), hlyA (72%) and ompU (28%). The chironomid populations and the V. cholerae in their egg masses followed the phenological succession and interaction of host,pathogen population dynamics. A peak in the chironomid population was followed by a peak in the V. cholerae population. If such a connection is further substantiated for the pathogenic serogroups of V. cholerae in endemic areas of the disease, it may lead to a better understanding of the role of chironomids as a host for the cholera bacterium. [source]

Insects in a warmer world: ecological, physiological and life-history responses of true bugs (Heteroptera) to climate change

GLOBAL CHANGE BIOLOGY, Issue 8 2007
DMITRY L. MUSOLIN
Abstract Focusing on the southern green stink bug, Nezara viridula (Pentatomidae), in central Japan the effects of climate change on true bugs (Insecta: Heteroptera) are reviewed. In the early 1960s, the northern edge of the species's distribution was in Wakayama Prefecture (34.1°N) and distribution was limited by the +5°C coldest month (January) mean temperature isothermal line. By 2000, N. viridula was recorded 70 km further north (in Osaka, 34.7°N). Historical climate data were used to reveal possible causes of the northward range expansion. The increase of mean and lowest winter month temperatures by 1,2°C in Osaka from the 1950s to the 1990s improved potential overwintering conditions for N. viridula. This promoted northward range expansion of the species. In Osaka, adult diapause in N. viridula is induced after mid-September, much later than in other local seed-feeding heteropterans. This late diapause induction results in late-season ineffective reproduction: some females start oviposition in autumn when the progeny have no chance of attaining adulthood and surviving winter. Both reproductive adults and the progeny die. A period from mid-September to early November represents a phenological mismatch: diapause is not yet induced in all adults, but it is already too late to start reproduction. Females that do not start reproduction but enter diapause in September have reduced postdiapause reproductive performance: they live for a shorter period, have a shorter period of oviposition and produce fewer eggs in smaller egg masses compared with females that emerge and enter diapause later in autumn. To some extent, N. viridula remains maladapted to Osaka environmental conditions. Ecological perspectives on establishment in recently colonized areas are discussed. A review of available data suggests that terrestrial and aquatic Heteroptera species respond to climate change by shifting their distribution ranges, changing abundance, phenology, voltinism, physiology, behaviour, and community structure. Expected responses of Heteroptera to further climate warming are discussed under scenarios of slight (<2°C) and substantial (>2°C) temperature increase. [source]