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Egg Batches (egg + batch)
Selected AbstractsTeratogenicity of elevated egg incubation temperature and egg vitamin A status in Atlantic salmon, Salmo salar L.JOURNAL OF FISH DISEASES, Issue 4 2004R Ørnsrud Abstract The present study was undertaken to investigate the possibility that high egg vitamin A (VA) status in combination with elevated egg incubation temperatures may cause deformities in Atlantic salmon, Salmo salar L. Egg batches selected for their total VA concentration were exposed to low (normal, 8 °C) or elevated (14 °C) egg incubation temperatures. Temperature was the main factor causing bone deformities such as warped gill opercula, fin and jaw deformities, but not for the development of spinal deformities where all groups displayed a ,baseline' occurrence of mild deformity (decreased vertebral size in the cephalic region) and no systematic variation in the occurrence of serious spinal deformities (fused vertebrae). A possible effect of egg incubation temperature fluctuation was found for the groups reared at low temperatures. An indication of a negative effect of elevated egg VA status for the development of organ deformities such as missing septum transversum and situs inversus was found in addition to temperature effects, however, no firm conclusions could be drawn from the present data. The phenotypes for temperature-induced deformities resembled the phenotype of VA-induced deformities, but no clear conclusions on the causality of the deformities found in the present study could be drawn. Egg incubation temperatures, both absolute temperature and temperature variations, should therefore be strictly controlled. [source] Yellow belly as honest signal of female quality in Knipowitschia panizzae(Gobiidae)JOURNAL OF FISH BIOLOGY, Issue 2003C. Mazzoldi Sexually dimorphic traits are common in fish species, and examples from both males and females have been described. The function of these traits has been widely investigated in males. On the contrary, female ornaments have been studied mainly in sex role reversed species, such as pipefish, while their role in species with ,conventional' sex roles remain to be investigated. This study focused on the presence, function, and possible role as indicator of female quality of a sexually dimorphic nuptial trait in the lagoon goby, Knipowitschia panizzae. In this species, that present conventional sex roles, females show a yellow spot on the belly. Aquarium spawning experiments demonstrated that the coloration on the belly is due to dermal pigments, is displayed only when female is ready to spawn and is switched off within few minutes from the end of egg deposition. This sexual trait presents variability in size among females and indicates female fecundity relatively to her own body size. As a consequence, female yellow belly appears to be an honest signal of female quality. Field data on natural nests highlighted that males perform parental cares mostly only on one egg batch at a time and the modality of egg deposition suggested that males are limited in their potential reproductive rates by environmental factors. Male limitation in egg care could constitute the basis for a female biased operational sex ratio, favouring male choosiness and the evolution of female nuptial displays. [source] Field and laboratory studies in a Neotropical population of the spinose ear tick, Otobius megniniMEDICAL AND VETERINARY ENTOMOLOGY, Issue 1 2009S. NAVA Abstract One ear of each of five cows on a property close to Dean Funes, province of Córdoba, Argentina, was inspected monthly from December 2004 to November 2006 to determine the presence of Otobius megnini (Dugès) and to ascertain its seasonality. Ticks were collected to study the biological parameters of larvae, nymphs and adult ticks. Groups of nymphs were also maintained at three different photoperiods at 25 °C. The abundance of immature stages was greatest during January,April and August,October in the first and second years of the study, respectively. No larvae successfully moulted. Nymphs weighing < 17 mg also failed to moult, but 89% of heavier nymphs moulted into adults. Nymphs moulting to males weighed less (49.5 ± 16.09 mg) than nymphs moulting to females (98.1 ± 34.08 mg). The pre-moult period was similar for nymphs moulting to either sex and significantly longer (P < 0.01) for female nymphs maintained at 25 °C compared with nymphs kept at 27 °C. No effect of photoperiod on the pre-moult periods of nymphs was detected. Female ticks produced a mean of 7.0 ± 1.94 egg batches after a preoviposition period of 16.4 ± 8.41 days for the first batch. The mean oviposition period was 61 ± 20.8 days and the duration of oviposition for each batch varied from 1 to 6 days. The mean number of eggs per batch was 93.1 ± 87.53. The minimum incubation period for the first egg batch was 13.6 ± 2.77 days. The total number of eggs laid by each female was 651.6 ± 288.90. Parthenogenesis was not observed. The reproductive efficiency index (REI) (number of eggs laid/weight of female in mg) was 5.5 ± 1.26. Pearson's correlations showed a significant direct relationship between the weight of the female and number of eggs laid (P < 0.01) and REI (P < 0.05). Several of the biological values presented above for the tick population from the Neotropical zoogeographic region showed marked differences to equivalent values for O. megnini populations from the U.S.A. (Nearctic) and India (Oriental). Nevertheless, the only two sequences of 16S rDNA deposited in GenBank from ticks originating in Argentina and allegedly in the U.S.A. indicate that they are conspecific (99.8% agreement). We tentatively consider the biological differences among populations of this tick species to represent adaptations for survival at different conditions. [source] Surface morphology of eggs of Euproctis chrysorrhoea (Linnaeus, 1758)ACTA ZOOLOGICA, Issue 2 2008Selami Candan Abstract Candan, S., Suludere, Z. and Bayrakdar, F. 2007. Surface morphology of eggs of Euproctis chrysorrhoea (Linnaeus, 1758). ,Acta Zoologica (Stockholm) 88: 000,000. Filaments covering the egg batches and chorion structure were studied both by light and scanning electron microscopy in the brown-tailed moth Euproctis chrysorrhoea (Linnaeus, 1758). Females lay eggs in masses on the underside of apple leaves. The egg batches are covered with brown hairs derived from the bodies of the female. Each female lays about 200,400 eggs. The spherical eggs are about 0.84 mm long and 0.47 mm wide. Newly deposited eggs are golden-yellow and darken after the onset of embryonic development. The micropylar area appears somewhat depressed and has a circular outline. The region is surrounded by a rosette of 10,12 petal-shaped primary cells, which are completely surrounded by a series of secondary and tertiary cells. The remainder of the egg is largely smooth, but shows aeropyles. These are located in the corners of ill-defined polygons. [source] Fishery-induced demographic changes in the timing of spawning: consequences for reproductive success,FISH AND FISHERIES, Issue 3 2009Peter J. Wright Abstract Demography can have a significant effect on reproductive timing and the magnitude of such an effect can be comparable to environmentally induced variability. This effect arises because the individuals of many fish species spawn progressively earlier within a season and may produce more egg batches over a longer period as they get older, thus extending their lifetime spawning duration. Inter-annual variation in spawning time is a critical factor in reproductive success because it affects the early environmental conditions experienced by progeny and the period they have to complete phases of development. By reducing the average lifetime spawning duration within a fish stock, fishing pressure could be increasing the variability in reproductive success and reducing long-term stock reproductive potential. Empirical estimates of selection on birth date, from experiments and using otolith microstructure, demonstrate that there is considerable variation in selection on birth date both within a spawning season and between years. The few multi-year studies that have linked egg production with the survival of progeny to the juvenile stage further highlight the uncertainty that adults face in timing their spawning to optimize offspring survival. The production of many small batches of eggs over a long period of time within a season and over a lifetime is therefore likely to decrease variance and increase mean progeny survival. Quantifying this effect of demography on variability in survival requires a focus on lifetime reproductive success rather than year specific relationships between recruitment and stock reproductive potential. Modelling approaches are suggested that can better quantify the likely impact of changing spawning times on year-class strength and lifetime reproductive potential. The evidence presented strengthens the need to avoid fishing severely age truncated fish stocks. [source] Parametric intensity and the spatial arrangement of the terrestrial mollusc herbivores Deroceras reticulatum and Arion intermediusJOURNAL OF ANIMAL ECOLOGY, Issue 6 2000David A. Bohan Summary 1. Parametric intensity and spatial arrangement analyses were used to investigate the spatial pattern of the slugs Arion intermedius and Deroceras reticulatum. 2. The spatial lag of sampling (distance between sampling points) was shown to be unimportant in the intensity analyses. Rather, the 0·25 m grain scale was imposed on the whole sampling. The observed slope of the variance to mean relationships was common to both species, possibly determined by egg laying in batches at 0·25 m. However, the variance of the sample, for a given mean, was lower in summer. This corresponded with a reduction in the proportion of zero counts, which could be due to slug movement, possibly increased by predator activity, acting at the 0·25 m scale. 3. By contrast with the intensity analyses, the lag scale was important for spatial arrangement. At 0·25 m, in March 1997, the A. intermedius and D. reticulatum juveniles were aggregated, presumably about where egg batches were laid. At higher scales, the arrangements of D. reticulatum became spatially random, and A. intermedius resolved to a patch arrangement at the 16 m scale. 4. Over time, the D. reticulatum spatial arrangements remained random and independent of the previous sampling date. From March to July 1997, the A. intermedius patch persisted. A crash in abundance of both species, between July and October 1997, appeared to destroy the patch, but subsequent association suggested that the patch persisted until March 1998. The arrangements of the species were independent of one another on all sampling dates. 5. These species-specific spatial arrangements were independent of all measured environmental factors and consistent with differences in the local reproduction, survival and migration of A. intermedius and D. reticulatum. 6. This comparative study indicates that the terms aggregated, random and regular should have separate definitions for parametric intensity and spatial arrangement. Furthermore, spatial scale has different meaning in intensity and arrangement analyses. Spatial arrangements are not described by parametric intensity. Spatial arrangements change with spatial scale. Temporal changes in intensity need not manifest as changes in spatial arrangement. [source] Bt -maize as a potential trap crop for management of Eldana saccharina Walker (Lep., Pyralidae) in sugarcaneJOURNAL OF APPLIED ENTOMOLOGY, Issue 4 2007M. G. Keeping Abstract:, Notwithstanding the introduction of several pest management tactics, the stalk borer Eldana saccharina Walker (Lep., Pyralidae) remains the most serious pest in South African sugarcane. A novel tactic for managing this pest in sugarcane would be the use of a dead-end trap crop that attracts moths for oviposition and curtails subsequent larval development, thereby reducing pest population size. Glasshouse bioassays, in which moths chose to oviposit on maize producing Bacillus thuringiensis Cry1Ab toxin (Bt -maize), non- Bt -maize or sugarcane of two cultivars (borer-resistant and -susceptible), showed that E. saccharina laid significantly more eggs and egg batches per dry leaf and unit mass of dry leaf on maize (Bt or non- Bt) than on either of the cane cultivars. When moths had a choice of ovipositing on 2-, 3-, 4- or 5-month-old maize (Bt and non- Bt), dry leaf number and mass of dry leaf material was significantly correlated with number of eggs and egg batches, indicating that older plants, which carried larger amounts of dry leaf matter, were more attractive for oviposition. Finally, glasshouse assays in which hatching larvae fed on 2.5-, 3.5- and 4.5-month-old Bt and non- Bt -maize plants, showed that the Cry1Ab toxin was effective in killing E. saccharina larvae in all Bt -maize plant growth stages, confirming that Bt -maize fulfilled the third requirement (curtailing larval development) of a dead-end trap crop for this pest. We argue that Bt -maize warrants further testing in the field as a trap crop, both alone and as a component of a ,push,pull' or habitat management system for E. saccharina in sugarcane. [source] Frass sampling and baiting indicate European earwig (Forficula auricularia) foraging in orchardsJOURNAL OF APPLIED ENTOMOLOGY, Issue 5 2006D. M. Suckling Abstract:, Earwigs are significant generalist predators of a range of orchard pests, but quantitative assessment of earwig density and beneficial impact is difficult. A sampling system was designed and tested, based on field placement of polycarbonate tubes in apple trees as scotophase arboreal refugia. Tubes containing artificial diet and provided with a black plastic sleeve had the highest earwig counts. Tubes with diet or the black sleeve alone were less preferred. Presence of distinctive frass was also evident in polycarbonate tubes containing artificial diet, and earwig frass was recorded at a higher frequency than earwig presence, indicating foraging and detection of the tubes at a higher rate than their use as shelters. At the tree level, there was a weak correlation between frass abundance and predation rates on leafroller egg batches placed as baits in the canopy, but not with earwig density measured by corrugated cardboard rolls or diet tubes. Diet tubes have the potential to offer new insights into earwig foraging behaviour in orchards. [source] Interactions between the stem-mining weevils Ceutorhynchus napi Gyll. and Ceutorhynchus pallidactylus (Marsh.) (Coleoptera: Curculionidae) in oilseed rapeAGRICULTURAL AND FOREST ENTOMOLOGY, Issue 3 2004Georg Dechert Abstract 1,The rape stem weevil Ceutorhynchus napi Gyll. and the cabbage stem weevil Ceutorhynchus pallidactylus (Marsh.) share the same habitat and food resource within the stems of oilseed rape, Brassica napus L. var. oleifera. Interactions occurring between these two sympatric species on this host were studied under both field and laboratory conditions. 2,The oviposition preference of C. pallidactylus and the within-plant distribution of eggs and larvae were examined in field plots of oilseed rape. Female C. pallidactylus tended to lay their eggs in plants already infested by eggs and larvae of C. napi rather than in uninfested plants. The within-plant distribution of the egg batches of C. pallidactylus did not differ significantly between uninfested plants and those preinfested by C. napi. Ovipositing females of C. napi and C. pallidactylus generally showed a significant preference for plants with larger stem diameter. 3,Laboratory choice tests provided further evidence for the oviposition preference of C. pallidactylus. Females laid significantly more eggs in leaves of plants that had been previously infested by C. napi than in leaves of previously uninfested plants. 4,Larvae of C. pallidactylus showed a significant shift of their feeding niche towards the stem base when feeding in individual plants attacked by both species. This possibly indicates ressource partitioning between C. pallidactylus and C. napi. The within-plant distribution of C. napi larvae was not affected by the simultaneous attack of C. pallidactylus. 5,The size of the head capsule of full-grown larvae of C. napi and C. pallidactylus was not significantly correlated with the diameter of the stem of their host plant or with the number of conspecific larvae within individual plants. [source] Field and laboratory studies in a Neotropical population of the spinose ear tick, Otobius megniniMEDICAL AND VETERINARY ENTOMOLOGY, Issue 1 2009S. NAVA Abstract One ear of each of five cows on a property close to Dean Funes, province of Córdoba, Argentina, was inspected monthly from December 2004 to November 2006 to determine the presence of Otobius megnini (Dugès) and to ascertain its seasonality. Ticks were collected to study the biological parameters of larvae, nymphs and adult ticks. Groups of nymphs were also maintained at three different photoperiods at 25 °C. The abundance of immature stages was greatest during January,April and August,October in the first and second years of the study, respectively. No larvae successfully moulted. Nymphs weighing < 17 mg also failed to moult, but 89% of heavier nymphs moulted into adults. Nymphs moulting to males weighed less (49.5 ± 16.09 mg) than nymphs moulting to females (98.1 ± 34.08 mg). The pre-moult period was similar for nymphs moulting to either sex and significantly longer (P < 0.01) for female nymphs maintained at 25 °C compared with nymphs kept at 27 °C. No effect of photoperiod on the pre-moult periods of nymphs was detected. Female ticks produced a mean of 7.0 ± 1.94 egg batches after a preoviposition period of 16.4 ± 8.41 days for the first batch. The mean oviposition period was 61 ± 20.8 days and the duration of oviposition for each batch varied from 1 to 6 days. The mean number of eggs per batch was 93.1 ± 87.53. The minimum incubation period for the first egg batch was 13.6 ± 2.77 days. The total number of eggs laid by each female was 651.6 ± 288.90. Parthenogenesis was not observed. The reproductive efficiency index (REI) (number of eggs laid/weight of female in mg) was 5.5 ± 1.26. Pearson's correlations showed a significant direct relationship between the weight of the female and number of eggs laid (P < 0.01) and REI (P < 0.05). Several of the biological values presented above for the tick population from the Neotropical zoogeographic region showed marked differences to equivalent values for O. megnini populations from the U.S.A. (Nearctic) and India (Oriental). Nevertheless, the only two sequences of 16S rDNA deposited in GenBank from ticks originating in Argentina and allegedly in the U.S.A. indicate that they are conspecific (99.8% agreement). We tentatively consider the biological differences among populations of this tick species to represent adaptations for survival at different conditions. [source] Lifetime reproductive output of Calliphora vicina and Lucilia sericata in outdoor caged and field populations; flight vs. egg production?MEDICAL AND VETERINARY ENTOMOLOGY, Issue 4 2006LEWIS DAVIES Abstract Females of the blowflies Calliphora vicina (Robineau-Desvoidy) and Lucilia sericata (Meigen) (Diptera: Calliphoridae) maintained in sheltered outdoor cages and supplied with excess food, oviposited later than would have been expected from the temperature-sum. The survival rates of the caged flies was high and the isolation of flies from predation, extreme temperatures and food shortages is likely to have contributed to this. Despite good survival rates, subsequent egg production over the greater part of the adult life span was reduced to ,24% for C. vicina and ,55% for L. sericata, of the potential expected from the published temperature-sums required for the maturation of successive egg batches. The data suggest that under field-cage conditions there is a considerable variation in egg development between individuals of the same age and that this variation should not be overlooked, since it may have significant implications in ecological and forensic investigations; however, the cause of this variability remains unclear. While lower than expected, the reproductive outputs recorded in the cages were nevertheless considerably greater than those that have been estimated for blowflies in the field and illustrate the potential for population increase in these species under favourable conditions. The possibility of a greater energy investment in flight activity relative to reproductive output in C. vicina compared to L. sericata is proposed. [source] Assessing the spawning season in common dentex (Dentex dentex) using microsatellitesAQUACULTURE RESEARCH, Issue 12 2008Yaisel J Borrell Abstract A set of five variable microsatellite markers was used for the genetic characterization of two common dentex (Dentex dentex) broodstocks from an experimental hatchery and for the screening of the egg batches spawned during the complete spawn season in 2006. After parentage assignment, simulations were performed for the hatchery 1 broodstocks; the microsatellite set correctly assigned over 93% of descendants to parents when one parent was known and 80% when neither parent was known. Of the 261 eggs that the DNA was correctly amplified from, 254 were successfully assigned to a parental couple. More than one female or male took part (at the same point in time) in the spawning season. However, we observed ,dominant' individuals that produced high proportions of the descendants (unequal reproductive success) in all the sampling periods, although the contributions of these dominant individuals could change over time. This phenomenon reduces the effective breeding numbers, and could lead to inbreeding if this factor is not taken into account when the next parental generation is obtained. This factor should also be considered in aquaculture selection programmes because the dominant breeders may not be the most interesting individuals for commercial or productive schemes. [source] Effects of incubation temperature on development and yolk sac conversion efficiencies of spotted wolffish (Anarhichas minor Olafsen) embryos until hatchAQUACULTURE RESEARCH, Issue 11 2005Terje Sund Abstract Two egg batches of spotted wolffish, Anarhichas minor Olafsen, were incubated at 4, 6 and 8°C. Embryo samples were fixed and compared on each 100th daydegree until hatching (up to 1000 daydegrees). Embryos, yolk sacs and chorions were dissected and the sizes, wet and dry weights were recorded separately. Comparisons of gross morphologies and measured parameters showed increasing and generally significant differences with time between the incubation temperatures. Lower temperatures produced longer and more differentiated larvae at hatch with a smaller yolk sac. Even though some unexpected deviations were registered among batches and experimental groups, it was clear that temperature affected embryo survival and time of hatching. Overall survival was best at 6°C, in agreement with results from earlier studies. Yolk conversion efficiencies measured around the hatching point were generally high, ranging from 60% to 78%, varied between the two batches and probably reflected the developmental variations between embryos and larvae at the respective ages (daydegrees). The hatching process was apparently an energy-demanding period; yolk conversion efficiencies of unhatched embryos of similar age at each temperature were always higher. Temperature is one environmental factor that can be manipulated in hatcheries to induce hatching of viable larvae at an optimal stage of differentiation with respect to first-feeding success and early survival. [source] Incidence of conjoined twins in tilapia after thermal shock induction of polyploidyAQUACULTURE RESEARCH, Issue 5 2000M Owusu-Frimpong Conjoined twins (polyembryonic fish) were observed in batches of blue tilapia Oreochromis aureus (Steindachner) and Nile tilapia O. niloticus (L.) embryos incubated at 28 °C. Heat shock (41.8 °C) treatment of fertilized eggs for 3,4 min applied between 4 min and 27 min after fertilization increased the twinning rate by three or four times over that of unshocked eggs. Two basic morphological variations , ventrally or laterally conjoined twins , were observed. Twins did not survive beyond 21 days after hatching. The proportion of twins in heat-shocked egg batches of both species combined ranged from 0.32% to 0.40%. [source] Differences in egg parasitism of Chrysophtharta agricola (Chapuis) (Coleoptera: Chrysomelidae) by Enoggera nassaui Girault (Hymenoptera: Pteromalidae) in relation to host and parasitoid originAUSTRALIAN JOURNAL OF ENTOMOLOGY, Issue 3 2002Helen F Nahrung Abstract The first instances of egg parasitism of Chrysophtharta agricola, a pest of eucalypt plantations, are recorded. Enoggera nassaui was found parasitising C. agricola egg batches in Tasmania, the Australian Capital Territory (ACT), New South Wales and Victoria: this is the first record of this parasitoid species from Victoria. One instance of Neopolycystus sp. parasitising C. agricola eggs in Victoria was also recorded. Parasitism of egg batches by E. nassaui ranged from 0 to 55% between five geographical populations collected in mainland Australia (n = 45), and from 0 to 2% between two populations collected in Tasmania (n = 300). For mainland sites at which parasitism was recorded, parasitism rates within sites differed significantly from either population in Tasmania. Reciprocal exposure experiments using one Tasmanian (Florentine Valley) and one parasitised mainland (Picadilly Circus, ACT) population were conducted in the laboratory to examine whether these different parasitism rates were attributable to egg or parasitoid origin. Parasitoids from the ACT parasitised C. agricola eggs of both origins more successfully than parasitoids from Tasmania, with up to 65% wasp emergence compared with 33% from Tasmania. Parasitoid origin significantly affected the number of wasps that emerged from exposed batches, but not the total loss from parasitism. [source] | |||||||||||||