Egg Size Distribution Research Articles

Evo‐devo in the ophiuroid family Ophiocomidae

AbstractThe Ophiuroidea, the most diverse echinoderm class, exhibits an array of life history patterns and larval forms, the evolution of which is poorly understood. With a robust phylogeny available for the major family, the Ophiocomidae, we undertook an assessment of the evolution of development in these ophiuroids. We spawned 15 species and documented larval development in 14 of these. In total, data on egg size or larval development were available for 27 species across the four recognized genera (Breviturma, Ophiocoma, Ophiocomella, and Ophiomastix). Ophiocomids have a bimodal egg size distribution. Species with small eggs (x̄ = 82 μm diameter, range 55–100 μm diameter) and large eggs (x̄ = 424 μm diameter, range 335–550 μm diameter) have planktotrophic ophioplutei and lecithotrophic vitellariae, respectively. The advanced ophiopluteus transforms into an armless vitellaria prior to metamorphosis through resorption of the larval arms and rearrangement of the ciliary tracts into series of transverse bands. Thus, the Type II pattern of development (which includes both the ophiopluteus and vitellaria) may be characteristic of the Ophiocomidae. This is not seen in other ophiuroid families. Evolution of nonfeeding (lecithotrophic) development through a vitellaria larva appears to have occurred only once in this family, in the genus Ophiomastix. Several traits appear to be specific to some species or genera, including an ornate fertilization envelope (Ophiocoma species), the presence of an early barrel‐shaped larva (Breviturma species), and the presence of vibratile lobes in advanced ophioplutei (Breviturma, Ophiocomella). In species with lecithotrophic development, the vitellaria is distinct, with prominent ciliated lobes around the developing juvenile rudiment. Larval form may assist with identification of ophiocomid larvae in plankton samples.

Effects of Strain and Stocking Density on Performance, Egg Size Distribution, Egg Quality, and Welfare in Laying Hens Housed in Enriched Cage System

Effects of Strain and Stocking Density on Performance, Egg Size Distribution, Egg Quality, and Welfare in Laying Hens Housed in Enriched Cage System

Reproductive Dynamics of Coryphaena hippurus (Linnaeus, 1758) Recorded from the Bay of Bengal, India

Ghosh, S.; Satishkumar, M.; Manas, H.M.; Rohit, P.; Abdussamad, E.M., and Gopalakrishnan, A., 2022. Reproductive dynamics of Coryphaena hippurus (Linnaeus, 1758) recorded from the Bay of Bengal, India. Journal of Coastal Research, 38(2), 369–376. Coconut Creek (Florida), ISSN 0749-0208. Coryphaena hippurus, one among the large pelagic species landed from Bay of Bengal, forms an important bycatch in drift gillnets and hook and lines. The present study, first from the region, is aimed at elucidating the reproductive biology from 1150 fishes from 2017 to 2019. Fork length of sampled fishes ranged from 25 cm to 110 cm and females contributed to the catch only up to a length of 88 cm. Growth was negatively allometric and length composition varied between sexes. Sex ratio was 1M:2.04F, significantly favouring females in most months, and more so in fishes measuring below 60.0 cm. Size at sexual maturity for females and males was 54.57 cm and 59.97 cm. Monthly percent contribution of spawning females and males ranged between 20.00 to 60.61 and 29.17 to 53.57. Monthly gonadosomatic index for females and males varied between 1.48 to 3.82 and 0.89 to 1.94. The values differed significantly; higher values during August to November indicated a peak in spawning. However, spawning occurred round the year, as evident by the presence of spawners and moderate values of the gonadosomatic index. Absolute fecundity ranged from 115,200 eggs to 1,501,808 eggs, with an average of 434,688 eggs. Egg size distribution demonstrated asynchronous gonadal development and batch spawning. Egg diameter of most abundant oocytes ranged from 0.60 mm to 0.69 mm, followed by another peak at 0.80 mm to 0.89 mm. Present study, first from region, provides detailed insights on reproductive biology, some of which are maiden information from Indian Ocean and knowledge generated would contribute significantly to stock management.

Egg size is a good predictor of parental care behaviour among bony fishes

AbstractParental care is a major feature in the evolution of life‐history traits and appears highly associated with the trade‐off between egg number and size. It has been a controversial issue in studies about reproductive strategy and is deemed to have evolved multiple times, both in aquatic and terrestrial taxa. To explore relationships between parental care and egg size, we examined 313 species of bony fishes, including 152 species with parental care and 161 species without parental care. We mapped parental care onto a maximum likelihood (ML) unrooted phylogeny and analysed egg size and numbers data set using a logistic regression. The phylogenetically controlled analyses revealed that parental care is dispersed along with the retrieved phylogeny and that at least four distinct lineages parallel evolved from non‐parental care lineages to parental care ones. The results of the logistic regression highlighted that egg size can be used as a good predictor of parental care and that there is a strong and consistent threshold in egg size transition between parental and non‐parental care fishes. We conclude that egg size predicts parental care in bony fish and that egg size distribution is polymodal within parental care species probably reflecting the variation in the amount of energy used for care. To advance the knowledge about the hypotheses raised in this study, it would be important to gather information about more species and their respective number and size of eggs and the presence/absence of parental care.

Dual-purpose production of eggs and meat\u2014part 2: hens of crosses between layer and meat breeds show moderate laying performance but choose feed with less protein than a layer hybrid, indicating the potential to reduce protein in diets

The use of modern chicken genotypes with high egg or meat performance results in the ethically unacceptable practice of culling day-old male layer chicks because of their inefficient fattening performance. Dual-purpose genotypes with a balanced performance profile for eggs and meat are one option to avoid this practice. In this study, the performance of four crosses of a layer breed (White Rock or New Hampshire) and the meat breed Bresse Gauloise, purebred Bresse Gauloise and the layer hybrid Lohmann Sandy was compared under organic husbandry conditions. Part 2 focuses on the laying performance of the hens until the age of 72 weeks and their feed choices when offered energy-rich and protein-rich feed mixtures. Feed consumption was generally high (133–143 g day−1), but the crosses consumed less protein feed than Lohmann Sandy, indicating a potential to reduce the proportion of high-protein components. Bresse Gauloise × White Rock showed severe plumage loss due to feather pecking, which was most likely caused by their low consumption of protein feed. Apparently, free-choice feeding did not agree with this genotype. Average laying performance of the crosses was 68–73% total eggs per average hen, which can be considered moderate. Average egg weights and egg size distribution were comparable with Lohmann Sandy, while slaughter performance of the senior hens was comparable with purebred Bresse Gauloise. Based on these findings, egg production with dual-purpose laying hens can be an ethically desirable alternative to high-performance genotypes, but will require further research on optimal feeding strategies and animal behaviour.Trial registered on July 7, 2017 (reference number V 241-26532/2017)

The reproductive ecology of the Antarctic bivalve Aequiyoldia eightsii (Protobranchia: Sareptidae) follows neither Antarctic nor taxonomic patterns

The accepted paradigm for reproduction in Antarctic marine species is one where oogenesis takes 18 months to 2 years, and a bimodal egg-size distribution where two cohorts of eggs are present in female gonads throughout the year. These slow gametogenic traits are driven by low temperature and/or the restriction of resource availability because of extreme seasonality in the marine environment. Here we present data on the reproductive ecology of the common Antarctic bivalve Aequiyoldia eightsii (Jay, 1839) (Protobranchia: Sarepidae) from monthly samples collected between January 2013 and May 2014 at Hangar Cove, Rothera Point on the West Antarctic Peninsula. These data show that A. eightsii is unusual because it does not follow the typical pattern expected for reproduction in Antarctic marine invertebrates, and differs also from closely related nuculanid protobranch bivalves with respect to gametogenic duration and reproductive periodicity. Continuous oogenesis, evidenced by the year-round occurrence of previtellogenic, vitellogenic, and ripe oocytes in female gonads, is supplemented by a seasonal increase in reproductive intensity and spawning in Austral winter (April–May), evidenced by the loss of mature spermatozoa and ripe oocytes from males and females, respectively. The simultaneous occurrence of these contrasting traits in individuals is attributed to a flexible feeding strategy (suspension and deposit feeding) in response to seasonal changes in food supply characteristic of the Antarctic marine environment. Asynchrony between individual females is also notable. We hypothesise that the variability may represent a trade-off between somatic and reproductive growth, and previously reported internal interannual cycles in shell growth.

Impact of fowlpox-vectored Mycoplasma gallisepticum vaccine Vectormune FP MG on layer hen egg production and egg quality parameters

This study was conducted to determine the impact of vaccination with Vectormune FP MG on egg production and egg quality characteristics of Single Comb White Leghorn hens. Due to questions of the efficacy of this vaccine in preventing Mycoplasma gallisepticum-mediated pathology, the ability of this vaccine to protect against postproduction-peak egg losses associated with F-strain M. gallisepticum (FMG) vaccination was also investigated. Vaccination with Vectormune FP MG did not result in any significant change in egg production or egg quality parameters compared with control (unvaccinated) hens. Subsequent revaccination with FMG at 45 wk of age (woa) yielded no impact on egg production or egg quality parameters of Vectormune FP MG vaccinated hens, unlike prior results for postproduction-peak vaccination of M. gallisepticum-clean hens with FMG, which exhibited a drop in egg production of approximately 6%. No difference in egg size distribution was observed for any of the treatment groups before or after FMG revaccination. These results suggest that hens can be safely vaccinated with Vectormune FP MG as pullets and can be revaccinated with a live M. gallisepticum vaccine such as FMG at a later date with no deleterious effects on egg production or egg or eggshell quality parameters.

What do egg size distributions in marine invertebrates tell us about validity of fecundity-time models?

An early mathematical model of egg size evolution in marine invertebrates (American Naturalist, 1973a, 107, 353) traded fecundity against development time and resulted in a U-shaped optimality curve suggesting that only extremes of egg sizes should be evolutionary stable. It was later suggested that the model predicts a bimodal distribution of egg sizes and therefore can be tested by examining histograms of egg sizes. More recent fecundity-time models (American Naturalist, 1997, 150, 48; American Naturalist, 2000, 156, 175) came up with predictions of intermediate optimal egg sizes; however, comparisons of optimality curves with histograms of egg sizes remained central to model testing. Here the question whether the bimodality assumption has any basis has been addressed theoretically. Simulation modeling and analysis show that egg size distributions generally do not match the optimality curves produced by fecundity-time models and that the shape of predicted frequency distributions depends on both the optimality curve and other model parameters. Therefore, egg size frequency distributions alone cannot be used for model testing.

Effects of Predation and Trophic Conditions on the Reproduction of Tylototriton verrucosus (Caudata: Salamandridae) in Darjeeling

The facts that small hatchlings emerged from small eggs laid under high predation levels prevailing at the lower altitudes of distribution of this species in Darjeeling while larger hatchlings emerged from larger eggs laid under lower levels of predation at higher altitudes, show that predation is not selected for large egg and initial hatchling size in this salamandrid species. Metamorphic size was small under high predation rates because this species relied on crypsis for evading predators. Egg and hatchling size are related inversely to levels of primary productivity and zooplankton abundance in lentic habitats. Hatchling sizes are related positively to egg size and size frequency distribution of zooplankton. Small egg and small hatchling size have been selected for at the lower altitudes of distribution of this salamandrid in Darjeeling because predation rates increased in step with improvement in trophic conditions at the lower altitudes.

Effect of Rearing Dietary Regimen, Feeder Space and Density on Egg Production, Quality and Size Distribution in Two Strains of Brown Egg Layers

Step-Up Protein (SUP) rearing regimens can reduce Feed Consumption (FC) and Body Weight (BW), while still resulting in pullets with equal or superior egg production and egg mass to pullets grown on a Step-Down Protein (SDP) program. Egg weight has been reduced due to SUP programs, presumably due to the reduced BW at sexual maturity. Because BW is reduced by SUP regimens and a slight lowering of FC, BW and EW may be economically advantageous. Therefore, the objective of this experiment was to evaluate the impact of SUP regimens on brown-egg layer rearing program on subsequent productivity and the effect of feeder space and density on performance. Two brown-egg strains, Hy-Line (HB) and the H and N Brown Nick (BN) were grown on three different dietary regimens, i.e. a normal SDP regimen, a SU P regimen: low energy starter for 9 wk (SUP9) and a SUP regimen: low energy starter for 12 wk (SUP12). The SUP9 and SUP12 feeding regimens resulted in significantly lower BW and feed conversion and shorter sternum length, than the SDP regimen. Egg production was not significantly different among the 3 regimens, but feed conversion was lower while livability was highest in the SUP12 reared hens. Feeder space of 13.6 cm resulted in poorer feed conversion for the SUP12 reared hens. Density per hen of 482 cm resulted in 2

Effects of vaccination with F-strain Mycoplasma gallisepticum on egg production and quality parameters of commercial layer hens previously vaccinated with 6/85-strain Mycoplasma gallisepticum

This study was conducted to determine the effect of overlaying (revaccinating) F-strain Mycoplasma gallisepticum at 22 or 45 wk of age on commercial leghorn hens previously vaccinated with 6/85-strain M. gallisepticum at 10 wk of age. The treatment groups included unvaccinated hens (group 1), hens receiving 6/85-strain M. gallisepticum only (group 2), and hens receiving 6/85-strain M. gallisepticum followed by F-strain M. gallisepticum at either 22 (group 3) or 45 (group 4) wk of age. There was no significant effect on egg production or egg size distribution between any of the treatment groups, unlike previous studies looking at F-strain vaccination only. Egg quality parameters, including eggshell strength, Haugh unit score, and blood-meat spot were similar between the different treatment groups. There was a difference in the rate of pimpling at postpeak production for the treatment group receiving F-strain M. gallisepticum at 22 wk of age, consistent with previously published results. This work suggests that hens previously vaccinated with 6/85-strain M. gallisepticum can be safely revaccinated with F-strain M. gallisepticum to increase protection from field strains while ameliorating the adverse effects associated with F-strain M. gallisepticum vaccination in layers post onset of lay.

Reproductive and population parameters of discus fish Symphysodon aequifasciatus Pellegrin, 1904 (Perciformes: Cichlidae) from Piagaçu-Purus Sustainable Development Reserve (RDS-PP), lower Purus River, Amazonas, Brazil

The ornamental discus fish Symphysodon aequifasciatus Pellegrin, 1904, is a popular endemic cichlid species from the Amazon basin, however scientific information concerning biology and ecology in its natural habitat is scarce despite its importance on the international aquarium trade. In this study we evaluated reproductive parameters of S. aequifasciatus in natural habitat in Piagaçu-Purus Sustainable Development Reserve (RDS-PP), lower Purus River, Brazilian Amazon. Males are more frequent in the larger size classes and this might be related to the complex breeding behavior known for S. aequifasciatus. Values of L50 for both sexes corresponded to more than 60% of the maximum attained length which may indicate that energy allocation for somatic growth takes longer in S. aequifasciatus than in other species. Average fecundity for female discus was 1490, ranging from 950 to 1892 oocytes and its correlations with standard length and total weight were very low, probably due to the highly compressed discus' body shape. Egg size distribution showed four types of patterns, indicating one to four modes besides the reserve oocytes group. Our results indicate that S. aequifasciatus shows total spawning, in the beginning of flooding period, with the peculiar capacity of releasing multiple egg batches as a strategy that potentially enhances reproductive success.

Reproductive biology of a population of Gymnotus aff.carapo (Teleostei: Gymnotidae) from southern Brazil

The reproductive period and its relation with somatic and abiotic factors, the relative and absolute fecundity, spawning type, length of first maturation and sex ratio is describe for Gymnotus aff.carapo from a small lake at Itapuã State Park, Rio Grande do Sul, Brazil. Gymnotus aff. carapo presents a relatively long reproductive cycle extending from November/2003 to March/2004. Decreases in water conductivity and increases in dissolved oxygen are correlated with increased gonadal development in males. In females, seasonal increases in temperature and photoperiod and decreases in dissolved oxygen are correlated with increased gonadal development. The mean absolute fecundity was 915.3 oocytes, and mean relative fecundity 0.20 oocytes/mg body weight. Egg size distributions indicate multiple spawning. The size of first maturation was 141 mm in females and 146 mm in males. The sex ratio was 1:1, with a male bias only in smaller size classes.

Does within‐population variation in egg size reduce intraspecific competition in Atlantic Salmon, Salmo salar?

Summary If phenotypes differ in habitat preferences there may be a decrease in intraspecific competition with increasing phenotypic variation, causing heterogeneous populations to perform better than homogeneous ones. Furthermore, if the relative performance of different phenotypes depends on environmental conditions, population heterogeneity may buffer populations against temporal environmental variation. Here these hypotheses are tested using 10 experimental populations of juvenile Atlantic Salmon (Salmo salar L.) reared across a range of five different water discharges. Each population consisted of fish of identical parental origins to control for genetic differences among populations, but differed in body size heterogeneity owing to differences in egg size distributions. No effect of population heterogeneity on final body size or dispersal rates was detected. Thus, egg size heterogeneity does not appear to influence the average level of intraspecific competition in Atlantic Salmon. There was a strong positive effect of water discharge on body size, but no effects of phenotypic heterogeneity on variation in final body size among discharge levels. Thus, the relative growth performance of juveniles arising from different egg sizes may not change sufficiently with environmental changes for egg size variation to create a strong buffering effect against year‐to‐year variation in environmental conditions.

The effects of 6/85 live Mycoplasma gallisepticum vaccine in commercial layer hens over a 43-week laying cycle on egg production, selected egg quality parameters, and egg size distribution when challenged before beginning of lay.

In each of two trials, 80 commercial leghorn-type pullets were separated into two treatments with four replicates of 10 chickens in each treatment. Forty pullets were designated as controls and received no inoculation, whereas the remaining 40 pullets received the 6/85 vaccine strain of Mycoplasma gallisepticum (MG) at 10 wk of age. Hen-day egg production, egg weight, eggshell strength, Haugh unit score, pimpling incidence, and blood/meat spot incidence were monitored and recorded weekly in each trial through an entire laying cycle of 43 wk. Further, eggs from all treatments were collected daily, Monday-Thursday, and individually weighed. No significant difference was observed between the treatments for 43-wk means for hen-day egg production, for any of the monitored egg or eggshell quality parameters, or for the number of extra large, large, medium, small, pee wee, or undergrade egg sizes. A significant (P < or = 0.05) difference was observed for the number of jumbo-sized eggs between the two treatments. Results of this study suggest that vaccination of commercial layer chickens at 10 wk of age with 6/85 strain MG does not detrimentally impact egg production, egg size distribution, or ovary/oviduct function as evidenced by selected egg parameters monitored in this study.

The Effects of ts-11 Strain Mycoplasma gallisepticum Vaccination in Commercial Layers on Egg Production and Selected Egg Quality Parameters

Live Mycoplasma gallisepticum (MG) vaccines have been USDA approved and licensed for use in commercial layer chickens since 1988; however, egg production and egg quality data exist only for the F strain of MG. Information pertinent to the effects of ts-11 MG on egg and eggshell quality parameters, as well as egg size distribution, is lacking. In this study, pullets were inoculated at 10 wk of age with ts-11 strain MG and placed in biological isolation units at 10 birds/unit. Hen-day egg production, eggshell strength, Haugh unit score, pimpling incidence, and blood/meat spot incidence were monitored and recorded in each trial through a 45-wk production cycle. Further, eggs from all treatments were collected daily, Monday-Thursday, and individually weighed. Results of this study indicate that no significant difference was observed between the treatments for the parameters measured or for egg size distribution. Therefore, these data should lessen producers' concerns pertaining to the impact of ts-11 strain MG on egg production, egg and eggshell quality parameters, and egg size distribution.

The Effects of F Strain Mycoplasma gallisepticum, Mycoplasma synoviae, and the Dual Infection in Commercial Layer Hens over a 44-Week Laying Cycle When Challenged before Beginning of Lay. II. Egg Size Distribution

In each of two trials, 160 commercial pullets were separated into four treatments with four replicates of 10 chickens in each treatment. Forty pullets were designated as controls and received no inoculation; 40 pullets received F strain Mycoplasma gallisepticum (FMG); an additional 40 pullets received Mycoplasma synoviae (MS); and the final 40 pullets were inoculated with both FMG and MS (dual). All inoculations occurred at 10 wk of age. Eggs from all treatments were collected daily, Monday-Thursday, and individually weighed. No significant difference was observed among the treatments for percentages of jumbo, extra-large, medium, small, peewee, or undergrade eggs. As a percentage of eggs laid for the 4 days of each week over the 44-wk laying cycle of each trial, the FMG hens laid significantly fewer large size eggs (43.2%) as compared with either controls (51.17%) or dual-infected hens (49.95%). No significant difference was found in percentage of large eggs laid by FMG hens when compared with MS hens.

A Model Relating Egg Weight and Distribution to Age of Hen and Season

Economic models for table egg layer flocks require determination of egg value, which is a function of mean egg weight, distribution of individual egg weights, and egg prices for weight categories. Age of flock and season of lay, two major factors affecting egg size and egg weight distribution, were examined in this study of 112 commercial flocks. Individual egg weights for 100-egg samples were obtained at 24, 30, 40, 50, 60, 80, and 100 wk of age. Mean egg weight, excluding outliers, was significantly related to age of hen, season of sexual maturity, and season eggs were laid. The standard deviation of egg weight, excluding outliers, had a significant curvilinear relationship to mean egg weight. Equations were also obtained for mean weights and percentage of under- and oversized eggs (outliers). These equations and integration of the normal distribution can be used to calculate the percentage of eggs in various weight classes over the life of a particular flock.

ASPECTS OF THE BIOLOGY OF THE GIANT FORM OF STHENOTEUTHIS OUALANIENSIS CEPHALOPODA: OMMASTREPHIDAE) FROM THE ARABIAN SEA

An investigation was carried out on the recently discovered ‘giant’ extra large (XL) form of the squid Sthenoteuthis oualaniensis from the Arabian Sea. The sample consisted of 2 males, which have not been previously described, and 13 females. Diet composition, parasite loading, sucker ring dentition, biolumi-nescence and sexual dimorphism were examined and compared to known parameters of the medium (M) form. Reproductive strategy, potential fecundity, egg size distribution in the ovary and oviducts were examined in mature XL females. Evidence of multiple spawning in the giant form was also investigated. Overall body shape, bioluminescent structures and coloration of the giant form were similar to the M form, though the XL form had a smaller fin angle than the M form. The mature female XL form has a dorsal mantle length about twice that of a mature female M form. Adult females of the XL form have a dorsal mantle length about twice that of adult males of the same form. Differences between males and females were found in arm sucker ring dentition and parasite load, suggesting a difference in diet. This could be linked to size differences between the sexes. A strong correlation between ovary mass and mantle length was found (r2 = 0.64). Poor correlation was found between mantle length and oviduct mass (r2 = 0.128) and potential fecundity (r2 = 0.07). Potential fecundity ranged between 2–5 million eggs and the holding capacity of the oviducts was approximately 300, 000 eggs. This combined with the presence of spermatangia and the presence of food in the stomach suggest that the XL form is a multiple spawner. S. oualaniensis appears to have a plastic phenotype and has adapted to the Arabian Sea conditions by evolving the capacity to grow to a giant size.

Are Echinoderm Egg Size Distributions Bimodal?

Marine invertebrates can be categorized into species that reproduce by producing either large numbers of small, energetically inexpensive eggs that become planktotrophic larvae, or fewer, larger eggs with more yolk and lecithotrophic development (1). The selective advantages of these alternative strategies were considered in a series of simple mathematical models by Vance (2, 3). These models predicted that intermediate egg sizes should have lower reproductive efficiency, and that only extreme egg sizes should be evolutionarily stable (2, 3). Specifytally, Vance's models (2, 3) and later modifications (4-7), predict that eggs of marine invertebrates should have bimodal size distributions, rejecting the contrast between small egg/feeding and large egg/nonfeeding modes of development and the selection against intermediate egg sizes. Evidence for bimodality in egg size distributions is, however, equivocal, with unimodal distributions seen in the majority of comparative studies that are appropriate tests of the hypothesis (8-13). Bimodal distributions have been described only in a few groups of molluscs (4) and asteroid and echinoid echinoderms (14). Here we test the prediction of bimodality in the holothuroid and ophiuroid echinoderms and show that although the natural log-transformed egg size distributions are visually unimodal, the holothurian egg size distribution is statistically composed of two discrete modes. Moreover, reexamination of the asteroid and echinoid egg size distributions (14) with the addition of data from more recent literature confirms that there are two statistical modes in the egg size distributions of these classes. Thus, in the phylum Echinodermata, there is a bimodal egg size distribution three of the four classes in which this prediction can tested.