Effect Of Female Size Research Articles

Reproductive strategy of yellow squat lobster (Cervimunida johni Porter, 1903): re-evaluating the maturity criteria

ABSTRACT Studying the basic biology of heavily fished marine species is essential to achieving conservation and sustainable exploitation. Yellow squat lobster (Cervimunida johni) is a demersal crustacean with a long fishing history in the Southeast Pacific. However, knowledge of its reproductive biology is still fragmented, and these traits have never been validated at the gonad level. In this context, we assessed the reproductive traits of this species for the first time based on gonadal development using data from a research survey conducted during 2018 off the Chilean coast. A total of 117 and 376 gonads were assessed based on histological and macroscopic analyses, respectively. The functional and effective criteria (a combination of functional and physiological maturity) were used to estimate the maturity ogives. Using a total of 113 females, fecundity (F) and relative fecundity (RF) at length were estimated using the autodiametric method. We determined that females of yellow squat lobster possess group-synchronous ovary development with indeterminate fecundity. Histological analysis revealed that 59% of non-ovigerous females had mature ovaries and were therefore misclassified as immature based on the functional criterion. Similarly, maturity ogives derived from the effective criterion were displaced to smaller sizes and varied significantly from those estimated using the functional criterion (P < 0.05). In addition, the effects of female size on F and RF were significant (P < 0.05). A warning on the use of functional criteria for assessing maturity status is issued, and the importance of adult females on the per capita contribution to population renewal in this crustacean species is discussed .

Reproductive trade-offs of the estuarine copepod Eurytemora affinis under different thermal and haline regimes

Copepod females invest a quantity of resources in their reproduction. Depending on several biotic and abiotic factors and their evolutionary history a trade-off can be commonly observed between producing a large number of smaller offspring or a small number of larger offspring. In this study, a multi-generational approach was applied to determine whether a trade-off between clutch size and egg size existed in the copepod Eurytemora affinis under different controlled conditions of temperature and salinity. This protocol was based on the follow-up of reproductive (Clutch Size ‘CS’, Egg Diameter ‘ED’) and morphological (Prosome Length ‘PL’) traits during several generations. Copepods were acclimated to cold (7 °C) and warm (20 °C) temperatures, and then their reproductive output was tested at the higher temperature of 24 °C. CS and ED were positively correlated to PL, so as a first step linear regressions between each reproductive trait and female PL were performed. The residuals from the regression lines of CS and ED with PL were calculated to remove the effect of female size. When the normalized data (residuals) of CS and ED plotted together a negative relationship between egg size and egg number revealed the existence of a trade-off. Copepod populations initially acclimated to cold temperature are commonly characterized by relatively smaller CS and larger ED. Conversely, warm temperature adapted females produced relatively larger CS and smaller ED. After transfer to a temperature of 24 °C, the ED did not change but the CS showed high variability indicating stressful conditions and no trade-off was observed. These observations suggest that E. affinis is able to modulate its reproduction depending on the encountered temperature. It seems that this copepod species can shift between a K- and an r-strategy in response to colder or warmer conditions. In a late winter-early spring like cold temperature, copepod females seem to invest more on offspring quality by producing relatively larger eggs. This ecological strategy ensures a high recruitment of the spring generation that is responsible for the strength of the maximum population size usually observed in late spring-early summer (May–June). To the contrary, at summer-like temperature, where the population density decreases significantly in the Seine estuary, copepod females seem to switch from K to r strategy by favoring offspring number compared to offspring size. Finally, the use of a higher temperature of 24 °C seems to disrupt the observed reproductive trade-off even after several generations. These results suggest that a switching between K- or r-strategy of E. affinis depends highly on temperature effects. The effect of salinity increase during a summer-like temperature of 20 °C as well as after transfer to 24 °C decreased PL and CS but the ED did not change significantly.

Interpopulation variations in life history traits and reproductive tactics in Aedes aegypti: A test on populations 50 km apart

The interpopulation variation in life history traits of a species reflects evolutionary adaptation in response to a local environment regime. We examined the life history traits of Aedes aegypti populations from 2 cities in southern Taiwan separated by 50 km. Results revealed a high level of trait differentiation in immature developmental time and survival of Ae. aegypti between the 2 cities. The Kaohsiung populations exhibited total pupation of 40%–60% on day 8; this was significantly lower than that of the Tainan populations and laboratory-reared KHsm mosquitos, which exhibited a pupation rate of 70%–90%. The slow immature development of the Kaohsiung populations was reflected in the low percentage of adult emergence (22%–26%) on day 10. The prolonged immature development did not select larger adults with longer life spans because the Kaohsiung populations had a shorter life span (≈37 d) than that of the Tainan populations (≈42 d). By contrast, immature development and longevity did not differ between populations within each region, indicating weak local differentiation. Three field populations exhibited male-bias sex ratio because of differential mortality of female immatures. The effect of female size on adult life history was nonsignificant. Two reproduction tactics were detected, representing the balanced-mortality hypothesis and the bet-hedging hypothesis. Despite their differential life history strategies and reproductive tactics, these mosquito populations apparently counterbalanced any shortcomings in traits to produce similar population growth. Maintaining optimal population density is essential for Aedes mosquitos to increase the probability of encountering mates and reduce the Allee effect.

Spermathecal Filling in Aedes aegypti and Aedes albopictus: Effects of Female and Male Body Sizes and Species.

The mosquitoes Aedes aegypti (L.) (Diptera: Culicidae) and Aedes albopictus (Skuse) (Diptera: Culicidae) are ecologically similar species that have evolved independently in their native ranges, Ae. aegypti in Africa and Ae. albopictus in Asia. Where their invasive ranges overlap, interspecific mating is facilitated by both species swarming to mate around bloodmeal hosts during daylight. Here, we test hypotheses to account for variation in spermathecal filling in females of Ae. aegypti and Ae. albopictus, particularly, the effect of mosquito size on the number of spermathecae containing sperm after intraspecific and interspecifc matings of these two species. Results show that significantly more spermathecae contained sperm in large than in small Ae. albopictus females, but there was no effect of Ae. aegypti female body size on the average number of spermathecae filled. Among inseminated females, there was no effect of male size or cross-type on number of spermathecae with sperm. Differences in the effect of female size on the number of spermathecae that store sperm in Ae. aegypti and Ae. albopictus imply differences in the mating biology of these two species.

With our powers combined: integrating behavioral and genetic data to estimate mating success and sexual selection

The analysis of sexual selection classically relies on the regression of individual phenotypes against the marginal sums of a males × females matrix of pairwise reproductive success, assessed by genetic parentage analysis. When the matrix is binarized, the marginal sums give the individual mating success. Because such analysis treats male and female mating/reproductive success independently, it ignores that the success of a male × female sexual interaction can be attributable to the phenotype of both individuals. Also, because it is based on genetic data only, it is oblivious to unproductive matings, which may be documented by behavioral observations. To solve these problems, we propose a statistical approach which combines matrices of offspring numbers and behavioral observations. It models reproduction on each mating occasion of a mating season as three stochastic and interdependent pairwise processes, each potentially affected by the phenotype of both individuals and by random individual effect: visit of a female by a male, concomitant gamete emission, and offspring production. Applied to data from a mating experiment on brown trout, the model yielded different results from the classical regression analysis, with only a negative effect of female body size on the probability of visit and gamete release, while the classical approach based on regression found a positive effect of male size on the number of both visits and offspring, and no effect of female size. Because the general structure of the model can be adapted to other partitioning schemes of the reproductive process, it can be used for a variety of biological systems where behavioral and genetic data are available.

Evolution of life-history traits in geographically isolated populations ofVaejovisscorpions (Scorpiones: Vaejovidae)

Geographical isolation can over time accumulate life-history variation which can eventually lead to speciation. We used five species of Vaejovis scorpions that have been isolated from one another since the Pleistocene glaciation to identify if biogeographical patterns have allowed for the accumulation of life-history variation among species. Gravid females were captured and brought back to the lab until giving birth. Once offspring had begun to disperse, measurements of female size, reproductive investment, offspring size, offspring number, and variation in offspring size were recorded. Differences in how each species allocated energy to these variables were analysed utilizing path analysis and structural equation modelling. Female and offspring size, litter size, and total litter mass differed among species, but relative energetic investment did not. Most significant differences among species were not present after removing the effect of female size, indicating that female size is a major source of life-history variation. Path analyses indicated that there was no size–number trade-off within any species and that each species allocates energy toward total litter mass differently. Additionally, as offspring size increased, the variation in offspring mass decreased. These results show that each species allocates the same relative amount of energy in different ways. The variation seen could be a response to environmental variability or uncertainty, a product of maternal effects, or caused by the sufficient accumulation of genetic differences due to geographical isolation. © 2013 The Linnean Society of London, Biological Journal of the Linnean Society, 2013, 110, 715–727.

Effect of Drosophila melanogaster Female Size on Male Mating Success

In this study, we examined the influence of female size on mating success in Drosophila melanogaster. The results that were obtained from experiments performed in mating chambers allowed us to confirm the results of previous studies, demonstrating higher mating success of larger D. melanogaster males, and to conclude that female size also affects mating success, either when considering a single male or two competing males. We observed that the advantage for larger males depends on their size relative to that of the female, demonstrating a previously unknown role for female size in mating behavior studies. This effect of female size on mating success depends on various factors: males take longer to initiate courtship toward larger females, large females receive more wing vibrations from males prior to mating, and large females tend to keep moving for longer periods during male courtship. The importance of this finding is discussed in the context of recent reports on sexual conflict in D. melanogaster, in which males were observed to depress fitness in females as a result of intercourse.

The effect of flight on reproduction in an outbreaking forest lepidopteran

Post‐flight reproductive investment by female insects may be limited as a result of a trade‐off in resource allocation between flight and reproduction. Outbreaking forest pests reduce their habitat quality as a result of severe defoliation when population densities are high. Female relocation to better‐quality habitats can increase offspring survival but reduce their reproductive fitness through flight. In the present study, the effect of flight on the capacity of female Choristoneura conflictana (Walker) (Lepidoptera: Tortricidae) to mate and produce eggs is examined. Females are flown on flight mills, and the subsequent reproductive capacity of each moth is assessed through measures of mating success and egg production. There is no effect of flight on commencement or the duration of mating. Although flight does not affect egg production directly, energy expenditure as a result of flight (as measured by weight loss) shows a negative correlation to potential fecundity, possibly indicating the resorption of eggs in some females. The effect of female size on fecundity is dependent on mating status, suggesting that energy allocated to reproduction is not dependent on flight treatment. Female moth longevity also has a significant effect on egg production but is dependent on flight and mating treatments. There is a relationship between energy expenditure to flight and reproduction in C. conflictana. Females that fly away from dense populations may produce fewer offspring, although this cost may be mitigated by improved offspring survivorship in less defoliated habitats.

Size-assortative mating and effect of maternal body size on the reproductive output of the nassariid Buccinanops globulosus

Size- assortative mating is usually present in populations where there is a positive relationship between female size and reproductive output. In this study, we tested for the presence of sexual size dimorphism, size-assortative mating and the effects of female size on reproductive output in a wild population of Buccinanops globulosus, an endemic nassariid of the Southwestern Atlantic Ocean with direct development. The results showed that: 1) females were larger than males, indicating sexual size dimorphism; 2) mate sizes were significantly correlated, indicating a component of size-assortative mating; 3) males of medium and large size classes were paired with larger females than small-sized males; 4) larger females were paired with large males; 5) maternal body size was positively related to some proxies of reproductive success (number of nurse eggs per egg capsule, egg capsular area and total length at hatching). Our results suggest that larger females may be favored as mates over smaller ones owing to their higher investment per offspring and consequently a larger initial juvenile size as juvenile.

Effect of female size on host selection by a koinobiont insect parasitoid (Hymenoptera: Braconidae: Aphidiinae)

Body size is a main fitness component of insect parasitoids. We assessed the potential influence of maternal size of the parasitoid wasp Aphidius colemani Viereck (Hymenoptera: Braconidae: Aphidiinae) on its ability to parasitize the different instars of Aphis gossypii Glover (Hemiptera: Aphididae) on eggplant and cucumber. In the experiments vs parasitoid females were used. Females oviposited in all instars but more of the smaller hosts were parasitized. Host selection was affected by female size and the larger hosts were more frequently mummified by the large than the small females. Thus, parasitoid female size influ- enced host selection. This could affect the potential of the parasitoid to exploit populations of aphids that differ in their size structure. The importance of these results in terms of the ecological adaptations of the parasitoid and their implication for biological control are discussed.

Variability in oocyte size and batch fecundity in anchoveta (&lt;i&gt;Engraulis ringens&lt;/i&gt;, Jenyns 1842) from two spawning areas off the Chilean coast

Utilising histological preparations of ovaries from Engraulis ringens females collected in two contrasting spawning habitats along the Chilean coast, we assess the variability in oocyte size and batch fecundity during the peak spawning seasons in three years. The effects of female size (length and weight), batch fecundity and mean sea surface temperature on oocyte size were also examined. Results showed larger oocytes and lower batch fecundity in females from the southern area. Oocyte volume differences persisted inter-annually and were not explained by differences in female sizes. Since ovary weight was similar between areas, the cost of producing larger oocytes in the south population seems to be a fecundity reduction. The latitudinal variations in oocyte number and size seem to be determined by the predominant environmental conditions in each habitat. Hence, female E. ringens seem to adapt their reproductive tactics by producing eggs sizes and quantities that favour survival of their offspring under the environmental conditions in which they are to develop.

No evidence for strategic male mating effort in response to female weight in a bushcricket

AbstractTheoretical models predict that males should allocate sperm in response to female quality and empirical studies have shown that fecundity traits including age, mass and mating status can influence male sperm allocation strategies. We tested whether female size has an influence on sperm allocation in the bushcricket Poecilimon jonicus jonicus (Orthoptera: Phaneropterinae). Contrary to other studies, we found neither evidence of strategic sperm allocation in response to female size nor an effect of female size on spermatophore size. Male age and mating history was positively related to sperm number during sequential matings, but had no effect on spermatophylax or ampulla weight. Spermatophore weight, but not sperm number, was positively correlated with male body weight. Ampulla weight was positively correlated with spermatophylax weight.

An Investigation of the Sources of Variability in American Lobster (Homarus Americanus) Eggs and Larvae: Female Size and Reproductive Status, and Interannual and Interpopulation Comparisons

Abstract From 1997 to 2001, the effects of female size (cephalothorax length [CL]) and reproductive status on egg size (diameter, dry weight) and larva CL at hatching were investigated in two Homarus americanus populations in the Gulf of St. Lawrence (Iles-de-la-Madeleine, Anticosti) and one at Grand Manan (Bay of Fundy), Canada. The estimated size at 50% maturity was used to identify small (likely primiparous) females for each population. Multifactor, mixed-hierarchical ANOVA models were used to investigate the variability of eggs and stage I CL among years and populations. In all comparisons, the main source of variability in the egg and stage I larva size was females (within and among). Nevertheless, for the Iles-de-la-Madeleine population in each year except 2001, the mean stage I larva sizes from small (CL < 79 mm), probably primiparous females were significantly smaller (P < 0.0085) than the mean larva sizes from larger females. However, female CL per se explained very little of the variance in mean...

Optimal copula duration in yellow dung flies: effects of female size and egg content

We examine data on copula duration in dung flies,Scatophaga stercoraria, in relation to female phenotype. We use a marginal value theorem approach based on the plausible mechanisms of sperm competition to predict the effect of female variation on optimal copula duration,t*, from the male perspective. Future fertilizations are expected to have a trivial effect ont* with fully gravid females, but an increasing relative effect ont* towards completion of oviposition.t* is expected to be affected by female size because of variation in (1) a female’s egg content, which increases the maximum egg gain available from a mating, and (2) the female reproductive tract, which affects the rate at which sperm are displaced. In fully gravid females,t* was not dependent on egg number variation, but showed a positive relation with egg content in females that had laid a varying proportion of their mature egg load at the time of mating, and were therefore not fully gravid. Our models predict that if a male can estimate egg content only by the distension of a female’s abdomen,t* should increase in a similar way to that seen with ‘take-over’ females. We predictt* for fully gravid females by assuming that males can monitor female size. The data showed that sperm displacement rate decreased, and average egg content increased, with female size. Under two models for a sperm displacement mechanism, one (which assumes indirect displacement at a rate proportional to the increase in spermathecal volume) predicts the observed relation betweent* and female size almost exactly. Small males copulated for longer than large males (as predicted and reported previously).

Effect of female size on fecundity and egg size in white-spotted charr: comparison between sea-run and resident forms

Effect of female size on fecundity and egg size in white-spotted charr: comparison between sea-run and resident forms

Effect of female size on fecundity and egg size in white‐spotted charr: comparison between sea‐run and resident forms

The relationships between fecundity, egg size and female size of sea‐run form were compared with resident form, using white‐spotted charr,Salvelinus leucomaenis. Both fecundity and egg size increase with female size. However, the relationship between egg size and female size differed significantly between the resident and sea‐run forms. Egg sizes of sea‐run and resident were similar even though sea‐run fish were much larger. ? 1998 The Fisheries Society of the British Isles

Development and Effect of Female Size on Egg and Juvenile Production in the Neogastropod Buccinum cyaneum from the Saguenay Fjord

The size at sexual maturity, the developmental timing and biology, and the biochemical (protein, glycogen, and lipid) content of eggs and juveniles were determined in two female size groups of the buccinid Buccinum cyaneum. Males reach sexual maturity at a smaller size (27 mm in shell length) than females (37 mm). A total of 33 females spawned in the laboratory starting in November 1991. The egg capsules were concave, measured 6.3 mm in diameter, and contained between 300 and 1000 eggs measuring 240 μm in diameter. Between 1 and 10 embryos developed. The others underwent chromatin degeneration within 3–4 wk and became nurse eggs. Between 1 and 10 crawling juveniles emerged 9 mo later in July and August and measured 2.5 ± 0.3 mm in shell length. The number of eggs and developing embryos within egg capsules increased with the size of the female. However, the quality of the juvenile at hatching, both in size and in biochemical content, did not vary significantly with female size.

Effect of Female Size and Propagation Methods on Larval Production at a South Carolina Striped Bass (Morone saxatilis) Hatchery

Larval production as a function of female size and hatchery propagation methods was examined for a South Carolina striped bass (Morone saxatilis) hatchery from 1988 to 1990. Female weight was not related to egg size or embryo survival among years or between source rivers of females. However, female weight was strongly related to number of hatched embryos due to its collinearity with fecundity. In 1988 and 1990, the offspring of 14 females contributed to 50% of hatchery production. In 1989, only six females contributed to 50% of larval production. In 1990, changes in propagation methods associated with improved female response to hormone injection resulted in more consistent rates of larval production among broods. While the deleterious effects of inbreeding on striped bass populations remain unknown, results indicate that extensive use of large females by hatcheries in fishery recovery programs could decrease effective population size.

Effects of Female Size, Mate Size, and Number of Copulations on Fecundity, Fertility, and Longevity of Nezara viridula (Hemiptera: Pentatomidae)

For once-mated female Nezara viridula L., size (width across the pronotum at the humeral angles) was positively correlated with fecundity (total lifetime egg production), size of the largest egg mass (number of eggs), and longevity (days as adult). Mate size was positively correlated with fecundity since females mating larger males lived longer and laid egg masses at a higher rate. Females mating larger males were less likely to lay infertile egg masses (all eggs unfertilized). Mate effects suggest size-dependent sperm and nutrient transfer to the female during copulation or reduced risk of contagion for females mating larger males. For multiply mated females, fecundity was positively correlated with both longevity and the number of matings. Thus, in the wild, females may be selected to mate with larger males and to mate repeatedly, patterns observed in previous field studies.

Patterns of Reproduction of Pontocaspian Relict Paramysis lacustris within Distribution Area

AbstractReproduction has been studied of Paramysis lacustris, pontocaspian relict, in the centre of its natural area, and in southern and northern zones of acclimatisation. Life cycles of the animals are identical in the distribution area. The effect of female size on fecundity is only slightly expressed within each generation. Significant correlations of these indices were obtained in seasonal aspect. Specific fecundity is represented by maximum values in the centre of the area and declines in the north‐western direction of introduction. The relation of fecundity to egg weight reflecting correlation of K‐r reproduction strategy is reduced in the regions of introduction. Reproduction effort, i.e. ratio of eggs weight to female weight, is the most stable index within the distribution area. Cumulative potential growth, including soma as well as generative products, was nearer in spite of considerable temperature difference in animal growth.