Larger Females Research Articles

Faster juvenile growth promotes earlier sex change in a protandrous hermaphrodite (barramundi Lates calcarifer)

The relationship between growth and sexual maturation is central to understanding the dynamics of animal populations which exhibit indeterminate growth. In sequential hermaphrodites, which undergo post-maturation sex change, the size and age at which sex change occurs directly affects reproductive output and hence population productivity. However, these traits are often labile, and may be strongly influenced by heterogenous growth and mortality rates. We analysed otolith microstructure of a protandrous (i.e., male-to-female) fish (barramundi Lates calcarifer) to examine growth in relation to individual variation in the timing of sex change. Growth trajectories of individuals with contrasting life histories were examined to elucidate the direction and extent to which growth rate influences the size and age individuals change sex. Then, the relationships between growth rate, maturation schedules and asymptotic maximum size were explored to identify potential trade-offs between age at female maturity and growth potential. Rapid growth was strongly associated with decreased age at sex change, but this was not accompanied by a decrease in size at sex change. Individuals that were caught as large females grew faster than those caught as males, suggesting that fast-growing individuals ultimately obtain higher fitness and therefore make a disproportionate contribution to population fecundity. These results indicate that individual-level variation in maturation schedules is not reflective of trade-offs between growth and reproduction. Rather, we suggest that conditions experienced during the juvenile phase are likely to be a key determinant of post-maturation fitness. These findings highlight the vulnerability of sex-changing species to future environmental change and harvest.

Size‐based differences in isotopic niche width (δ13C and δ15N) of green turtles (Chelonia mydas) nesting on Príncipe Island, Gulf of Guinea

AbstractWithin the same population, nesting green turtles (Chelonia mydas) might exploit different niches by exhibiting polymorphic foraging strategies and/or inhabiting geographically distinct foraging areas. This is crucial information for the conservation of this species. Here, we used stable carbon and nitrogen isotope ratios (δ13C and δ15N) to test for differences in a population of green turtles nesting on Príncipe Island (1°37′N; 7°24҆′E), Central Africa. A total of 60 nesting females were sampled on the two main nesting beaches of the island in December 2012. Minimum curved carapace length (CCL) was recorded, and δ13C and δ15N values were measured in the epidermis of each individual. Overall, CCL varied from 87.0 to 108.0 cm (mean ± SD =100.0 ± 5.1), δ13C values from −19.4 to −8.6‰ (−17.3 ± 1.8) and δ15N values from 7.9 to 17.3‰ (13.6 ± 1.5). Despite the large variation in both isotopic ratios, their distributions were unimodal, showing an absence of polymorphic foraging strategies and isotopically distinct foraging areas. However, smaller females (< median, 100.8 cm) occupied a much larger isotopic niche (i.e., four times greater) than larger females. These results suggest that nesting green turtles may forage opportunistically on the resources available in each of their foraging home ranges, with smaller females venturing to more isotopic‐diversified areas and/or exhibiting broader foraging strategies than larger females. In addition, and in accordance with other studies, findings suggest that the foraging grounds used by the Príncipe green turtle nesting females are distributed mainly throughout the Gulf of Guinea.

Effects of the upwelling system on the assessment of reproductive parameters of the caridean shrimp Nematopalaemonschmitti (Holthuis, 1950) in the Western Atlantic

AbstractCostal upwelling and other oceanographic features exert important effects on neritic and benthic communities, causing variations in the reproduction and survival of organisms. Here, we assessed the population structure, sex ratio, recruitment, and reproduction of the caridean shrimp Nematopalaemon schmitti near the Cabo Frio upwelling area in southeastern Brazil. In total, 759 individuals were captured. N. schmitti exhibited a unimodal size–frequency distribution pattern with larger females, and the binomial test indicated a significantly female‐biased sex ratio. The time‐series analysis showed synchrony between ovigerous females and juveniles that revealed continuous reproduction and the possible existence of recruitment areas. Our findings indicate that reproductive parameters are influenced by the environmental factors of the region studied here. We advocate that the influence of the sedimentary composition of the soft bottom and upwelling system of Cabo Frio is the predominant factors influencing the reproductive parameters in N. schmitti.

Field-based body temperatures reveal behavioral thermoregulation strategies of the Atlantic marsh fiddler crab Minuca pugnax.

Behavioral thermoregulation is an important defense against the negative impacts of climate change for ectotherms. In this study we examined the use of burrows by a common intertidal crab, Minuca pugnax, to control body temperature. To understand how body temperatures respond to changes in the surface temperature and explore how efficiently crabs exploit the cooling potential of burrows to thermoregulate, we measured body, surface, and burrow temperatures during low tide on Sapelo Island, GA in March, May, August, and September of 2019. We found that an increase in 1°C in the surface temperature led to a 0.70-0.71°C increase in body temperature for females and an increase in 0.75-0.77°C in body temperature for males. Body temperatures of small females were 0.3°C warmer than large females for the same surface temperature. Female crabs used burrows more efficiently for thermoregulation compared to the males. Specifically, an increase of 1°C in the cooling capacity (the difference between the burrow temperature and the surface temperature) led to an increase of 0.42-0.50°C for females and 0.34-0.35°C for males in the thermoregulation capacity (the difference between body temperature and surface temperature). The body temperature that crabs began to use burrows to thermoregulate was estimated to be around 24°C, which is far below the critical body temperatures that could lead to death. Many crabs experience body temperatures of 24°C early in the reproductive season, several months before the hottest days of the year. Because the use of burrows involves fitness trade-offs, these results suggest that warming temperatures could begin to impact crabs far earlier in the year than expected.

Males can’t afford to be choosy: Male reproductive investment does not influence preference for female size in Limia (Poeciliidae)

Reproductive investment was initially thought to be the key selective force behind male mate preference for female characters, like size or ornamentation (i.e., the preference by males for certain females). Yet, evidence of polygynous species, where male reproductive investments are often inexpensive compared to those of females, have also been described to possess male preference. Our study aims to understand how reproductive investment influences the selection of choosy males in polygynous systems using two species of livebearing fishes varying in reproductive investment: Limia perugiae, in which males invest heavily into reproduction, and L. zonata in which males invest minimally into reproduction. We hypothesized that male reproductive investment when combined with fecundity selection will favour the evolution of male mate preference and thereby lead to males that invest heavily into reproduction being choosier than males that invest minimally. When male Limia were exposed to two females simultaneously, one from the small size class and one from the large size class, L. zonata chose large females over small ones, whereas L. perugiae allocated the same amount of time regardless of female size class. Although we fail to find support for our original hypotheses, our study highlights the need for a more thorough examination of non-model species like Limia. We suggest future studies analyse reproductive investment as it interacts with cryptic choice, multiple sensory cues as well as expand comparisons to multiple Limia species, especially those endemic to Cuba, Grand Cayman, and Jamaica.

Increased and sex-selective avian predation of desert locusts Schistocerca gregaria treated with Metarhizium acridum.

The entomopathogenic fungus Metarhizium acridum in oil-based formulations (Green Muscle® (GM)) is a biopesticide for locust control lacking side-effects on biodiversity, unlike chemical insecticides. Under controlled conditions, GM-treated locusts and grasshoppers attract predators, a complementary advantage in locust control. We assessed avian predation on a population of desert locusts in northern Niger aerially sprayed operationally with GM with 107 g viable conidia ha-1. Populations of adult locusts and birds and vegetation greenness were assessed simultaneously along two transects from 12 days before until 23 days after treatment. Common kestrels Falco tinnunculus and lanners F. biarmicus were the predominant avian predators. Regurgitated pellets and prey remains were collected daily beneath "plucking posts" of kestrels. Locusts started dying five days post-spray and GM had its maximum effect one-two weeks after the spray, with 80% efficacy at day 21. After spraying, bird numbers increased significantly (P<0.05) concurrent with decreasing desert locust densities. Locust numbers decreased significantly (P<0.001) with both time since spraying and decreasing greenness. Before spraying, kestrel food remains under plucking posts accounted for 34.3 ±13.4 prey items day-1, of which 31.0 ±11.9 were adult desert locusts (90.3%), reducing post-spray to 21.1 ±7.3 prey items day-1, of which19.5 ±6.7 were adult desert locusts (92.5%), attributable to decreased use of the plucking-posts by the kestrels rather than an effect of the spray. After spraying, kestrels took significantly (P<0.05) more larger female (75-80%) than smaller male (20-25%) locusts. Avian predation probably enhanced the impact of the GM on the desert locust population, especially by removing large adult females. No direct or indirect adverse side-effects were observed on non-target organisms including locust predators such as ants and birds. These substantial ecological advantages should also be considered when choosing between conventional chemical and biopesticide-based locust control.

Preimaginal caste-related bias in the paper wasp Polistes jokahamae is limited to the first brood

Whether the caste fate of social insects is determined before or after emergence is a key question for understanding the evolution of eusociality. Paper wasps are a suitable model for answering this question because there are no critical morphological differences between queens and workers in paper wasps, and these animals appear to represent an early stage of eusociality. We explored the above question by determining the effects of photoperiod during the adult stage on caste-fate determination in the paper wasp Polistes jokahamae. We collected colonies at different stages in the field and exposed emerging adults individually to long or short days. Under these isolated conditions, gyne-destined (diapausing) females were expected to exhibit large lipid stores without mature eggs, while the reverse was expected to be true for worker-destined (nondiapausing) females. The proportion of wasps with mature eggs was higher under long days in the second and subsequent broods, but not in the first brood. Lipid stores were larger among large females and under short days, and smaller for the first brood. These findings together suggest that the first brood emerges with a strong preimaginal bias toward workers (nondiapausing form), whereas the other broods emerge with no bias or an easily reversible bias. However, it is difficult to conclude whether the bias came from body size or the season of emergence. We discuss the possibility that the ancestor of paper wasps had workers with and without preimaginal bias toward becoming workers at emergence.

Flight tone characterisation of the South American malaria vector Anopheles darlingi (Diptera: Culicidae).

BACKGROUND Flight tones play important roles in mosquito reproduction. Several mosquito species utilise flight tones for mate localisation and attraction. Typically, the female wingbeat frequency (WBF) is lower than males, and stereotypic acoustic behaviors are instrumental for successful copulation. Mosquito WBFs are usually an important species characteristic, with female flight tones used as male attractants in surveillance traps for species identification. Anopheles darlingi is an important Latin American malaria vector, but we know little about its mating behaviors.OBJECTIVES We characterised An. darlingi WBFs and examined male acoustic responses to immobilised females.METHODS Tethered and free flying male and female An. darlingi were recorded individually to determine their WBF distributions. Male-female acoustic interactions were analysed using tethered females and free flying males.FINDINGS Contrary to most mosquito species, An. darlingi females are smaller than males. However, the male’s WBF is ~1.5 times higher than the females, a common ratio in species with larger females. When in proximity to a female, males displayed rapid frequency modulations that decreased upon genitalia engagement. Tethered females also modulated their frequency upon male approach, being distinct if the interaction ended in copulation or only contact.MAIN CONCLUSIONS This is the first report of An. darlingi flight acoustics, showing that its precopulatory acoustics are similar to other mosquitoes despite the uncommon male:female size ratio, suggesting that WBF ratios are common communication strategies rather than a physical constraint imposed by size.

Seasonal Changes in the Sexual Size Dimorphisms of the Chelipeds and Pleons of the Porcellanid Crab Petrolisthes japonicus.

Decapod crustaceans develop secondary sexual structures, such as large chelipeds for weaponry and/or display in males and a wider pleon for incubating eggs in females. These structures should be costly to produce and maintain; hence, the crustacean reproductive strategy might have adapted to conserve energy for developing secondary sexual characteristics during the reproductive season. However, little is known about seasonal changes in the sexual size dimorphisms of the chelipeds and pleons of decapod crustaceans. Anomuran crabs from the family Porcellanidae exhibit a true crab-like body shape, with relatively large chelipeds for their body size and a well-developed pleon. They also show sexual size dimorphism (i.e., males with larger chelipeds and females with wider pleons); therefore, it was expected that seasonal changes in the sexual size dimorphisms of these organs would occur in porcellanid crabs. We tested this expectation using Petrolisthes japonicus, which is common on the intertidal cobble and boulder shores of the temperate and tropical regions of Japan. We employed allometric growth analyses of the cheliped and pleon dimensions of P. japonicus females and males collected over a year. Our analyses supported our expectation regarding the seasonal changes in the sexual size dimorphisms of the chelipeds and pleons in P. japonicus. Intersexual size dimorphism of the chelipeds and pleons was evident during the breeding season: females allocated more energy to pleon growth, while reducing cheliped growth, and investment in the pleon increased with increasing female body size, whereas males invested their energy in cheliped growth, and the investment in chelipeds increased with increasing male body size. During the nonbreeding season, females and males conserved energy by reducing the size of pleons and chelipeds relative to their respective body sizes. Our results highlighted the sex-specific and season-dependent resource allocation and reproductive strategies of porcellanid crabs.

High rates of consecutive spawning and precise homing in Sakhalin taimen (Parahucho perryi)

The frequency of reproduction and homing success are crucial in determining the lifetime reproductive fitness of iteroparous salmonids. We examined consecutive spawning and homing by Sakhalin taimen (Parahucho perryi), one of the least-studied iteroparous salmonids. The average consecutive return rate was 69.5%, the highest ever reported for an iteroparous salmonid. The consecutive return rates were highest for large spawners, females, and individuals with active inter-tributary movements in the preceding year. We estimated tributary-scale repeat homing rates to be 50–87%, which was significantly higher than expected by chance alone. The repeat homing rates were higher for spawners that entered tributaries with more abundant spawners in the preceding year, which is consistent with the pheromone hypothesis because the abundance of spawners in a tributary is expected to correlate to the concentration of chemical homing cues emanating from offspring in the following year. These extremely high consecutive return and homing rates likely facilitated local adaptation over evolutionary time scales and have contributed to population stability in this river system. These same traits, however, may impede species recovery following habitat restoration efforts within the species historic range (e.g. dam barrier removal or improved passage) due to their limited rate of dispersal.

Influencia del tamaño, variedad y relación hembra macho en la producción de huevos de tilapias (Oreochromis spp.) en tanques de concreto en el pie de monte andino venezolano

The aim of this study was examine the effect of the variety, size and male female ratio in the egg production of tilapia Chitralada (CH: Oreochromis niloticus) and Taiwanese Red (TR: O. mossambicus x O. niloticus) reared in tanks of concrete. The study was conducted in a fish farm located at the Venezuelan Andean foothill of Trujillo state, Venezuela. A 2x2x3 factorial arrangement was applied: two varieties (CH and TR), two sizes (small and large) and three sexual relations (1♀ : 1♂; 2♀: 1♂; 3♀: 1♂). The data were processed by analysis of variance using the general linear model of the SAS. The CH females produced 1.5 times more eggs, which weighed 1.6 times more and had a fecundity 1.6 greater than the TR (P 0.05), while large CH females produced a greater egg volume (8.91 ± 0.79 versus 6, 20 ± 0.79; P<0.01) and egg mass (7.99 ± 0.67 versus 5.65 ± 0.67; P<0.01), and were more fertile (1210.5 ± 113,4 versus 911.4 ± 113.5; P<0.10) than the smaller ones. In addition, large CH tilapia were reproductively more efficient than the same category of TR. In CH females the sex ratios did not affect most of the variables studied, with the exception of relative fecundity that was greater in the 2:1 ratio than in the 1:1 and 2:1 (154.4 ± 21, 4 versus 129.9 ± 18.1 and 133.1 ± 14.6 respectively; P<0.01). In contrast, in the TR females that were in a 3:1 sex proportion, the reproductive performance was considerably lower than those that were in a 1:1 or 2:1 sex ratio, and even, their performance was significantly lower than CH females of the same proportion (P<0.01). In conclusion, CH tilapias and females of larger size and weight were reproductively more efficient than those of the variety TR and those of smaller size; whereas the reproductive activity was not affected by the sex ratios considered in the study.

Sexual selection increased offspring production via evolution of male and female traits.

Phenotypic evolution driven by sexual selection can impact the fitness of individuals and thus population performance through multiple mechanisms, but it is unresolved how and when sexual selection affects offspring production by females. We examined the effects of sexual selection on offspring production by females using replicated experimental evolutionary lines of Callosobruchus chinensis that were kept under polygamy (with sexual selection) or monogamy (without sexual selection) for 21 generations. We found that polygamous-line pairs produced more offspring than monogamous-line pairs, because polygamous-line beetles evolved to be larger than monogamous-line beetles, and larger females were more fecund. Egg hatchability did not differ between polygamous- and monogamous-line pairs, as a result of the positive and negative effects of sexual selection cancelling out. When mated with an individual from a common tester line, both polygamous-line females and males showed higher hatchability in resultant eggs than monogamous ones. Further, cohabitation with a male reduced egg hatchability, and this effect was more pronounced in polygamous-line than in monogamous-line males. These results demonstrate multiple mechanisms by which sexual selection affects female fitness, with the net effect being positive. Analyses of how development time, body size and male genital morphology were influenced by selection regime suggest that these results arose from both evolution via good-gene processes and sexually antagonistic selection. Our results are also consistent with the hypothesis that the fitness consequences of sexual selection for females are dependent on the evolutionary history of the population.

Reproductive patterns and energy management strategies of females of the fiddler crabLeptuca uruguayensiswith short reproductive seasons

Reproduction is a costly process that depends on the management of available resources. Here, we aimed to understand the energetic strategies of females of the fiddler crab Leptuca uruguayensis (Nobili, 1901) in a population with short reproductive seasons. For this, we developed an integrated approach to recognize the brooding time, spawning pattern modulated by female size, number of spawns per female, and content of reserves in the ovary and hepatopancreas. Based on the condition of the ovary and hepatopancreas, the reproductive season was divided into three periods. In each of these periods, it was possible to record a spawning event, which was mainly represented by large females. Most of the females had one spawn during the breeding season, and only large females had two spawns, with an interval of approximately 2 months. We propose that L. uruguayensis presents a mixed capital–income breeding strategy associated with the female size and period of the reproductive season. We conclude that large females make the greatest reproductive effort for the population because they can have two spawns, whereas medium-sized and small females make a low contribution because they are still investing energy in somatic growth to increase fecundity in the next reproductive season.

Sex differences in diastolic blood pressure changes with age using 24-hour ABPM in 30,513 patients

Abstract Background We have previously shown, using 24-hour ABPM monitoring, that diastolic blood pressure (DBP) in a large referral population, containing both males and females, increases until age 42 years, following which DBP falls progressively. This occurs in the hypertensive population some 13 years sooner than previous general population studies. There is conflicting emerging data on sex differences in the lifelong trajectory of both systolic and diastolic blood pressure. Purpose To examine sex-specific patterns of diastolic blood pressure throughout the lifespan of patients referred for 24-hour ABPMs. Methods Our database was searched for all 24-hour ABPMs. We used the average 24-hour SBP and DBP for this analysis. Scatter grams were produced for age versus systolic BP (SBP) and DBP for both males and females. Second order polynomial regression was performed on the DBP scatter grams for both genders and their inflection points calculated. The inflection point is the age at which the DBP on the polynomial curve where the slope changes from positive to negative. This, inflection point, corresponds to the age at which DBP begins to decrease. The DBP polynomial curves for males and females were then superimposed to show any gender differences. Results There were 30,513 24-hour analysable ABPMs over 24 years, representing 97% of all ABPMs. There were 15,913 females aged 60.8±14.6 years (range 15–97 years) and 14,600 males aged 58.8±14.2 years (range 15–100 years). As can be seen from the charts below, in females DBP begins to fall at a very early age of 22.3 years, whereas in males the diastolic BP begins to fall at 46.5 years. Conclusions There are significant sex differences in the changes in DBP with increasing age. For the first 35 years DBP is higher in women, thereafter DBP is lower in females and only intersects again much later in life at 95 years. The significance of this sex difference is unclear but may explain the increased prevalence of systolic hypertension in elderly females. Figure 1 Funding Acknowledgement Type of funding source: None

Maternal body size and age govern reproduction and offspring phenotype in the zig-zag ladybird beetle (Menochilus sexmaculatus)

Maternal effects are possible channels through which mothers provision their offspring differentially, thereby affecting offspring phenotype. We investigated maternal effects in the zig-zag ladybird beetle (Menochilus sexmaculatus (Fabricius, 1781) = Cheilomenes sexmaculata (Fabricius, 1781)) in response to body size (induced by different feeding regimes during larval development) and their age within the reproductive cycle. Different-sized females were permitted to mate and were provided with daily-replenished ad libitum prey. After mating, reproductive output and developmental duration of offspring from different oviposition days were recorded. We hypothesized that small females would lay smaller and fewer eggs than larger females, and that egg mass would also reduce with increased maternal age. In our study, the larger mothers laid more eggs per day. Small and large mothers oviposited maximally at middle age. Maternal age did not influence the egg mass, although it was slightly higher in the case of older, larger females. Offspring from old, small and large mothers developed rapidly. This nimble development could be an adaptive strategy for the use of ephemeral aphid patches. The results of the study are indicative of this ladybird species’ ability to adjust their offspring’s life-history traits, a feature more prominent in larger females.

Effects of adult body size on mating success of the black soldier fly, Hermetia illucens (L.) (Diptera: Stratiomyidae)

Body size is a recognised factor impacting mating success of a number of insect species. The black soldier fly, Hermetia illucens (L.) (Diptera: Stratiomyidae), which is mass produced to convert organic waste to protein, exhibits a lekking behaviour necessary for mating. However, it is not known if adult body size impacts mating success and subsequent fertile egg production. In this study, larvae were raised at two densities to produce two size classes of adults (i.e. large and small). Hourly mating observations were recorded in the following studies: (1) homogenous populations of large or small adults; (2) 50% heterogenous populations (equal number of large males with small females and vice versa); and (3) 25% heterogenous (i.e. equal number of large and small adults for both sexes). Adult weight, morphometrics of resulting adults, total number of mating pairs and failed mating attempts, multiple matings, as well as eggs produced and associated hatch rate were recorded for each experiment. Morphometrics and weights in large adults were 21 and 50% greater than small adult males and females by size and weight, respectively. The first experiment of homogenous populations (i.e. large or small) showed no significant differences across other variables measured. However, when populations of different sized adults were mixed equally based on sex (i.e. 50% heterogenous populations), mating success increased 50 to 100% for small males with large females and large males with small females, respectively. Total number of multiple matings increased two to three times. Egg production decreased 15-20% and hatch rate declined approximately 10%. In the 25% heterogenous populations, data were more complex. Number of successful mating pairs across male size was 280% greater than in the homogenous populations. Number of failed mating attempts was also two to three times greater. Multiple matings overall were low (10%) for the homogenous and heterogenous populations. Large males demonstrated two times more aggression in general than small males in the heterogenous than the homogenous populations. Approximately 48 to 343% more eggs were produced in the 25% heterogenous population than large or small homogenous populations, respectively, while hatch rate did not differ among heterogenous and homogenous populations, with an average of 70%. However, the variability in egg hatch was forty times greater than the large homogenous and 40% greater than the small homogenous. While increased egg production is desired, high variability in egg hatch impedes fertile egg production and predictability at an industrial scale.

Reproductive ecology and growth of marine catfishes (Ariidae) supporting sustainable fisheries in Banc d’Arguin National Park, Mauritania

ABSTRACT Marine fish stocks are increasingly being exploited to unsustainable levels. Yet, knowledge of basic biological and ecological traits of species, required to sustain fisheries management at a local scale, remains scarce. We investigated the reproductive biology and growth of two marine catfishes: rough-head sea catfish (Arius latiscutatus) and Guinean sea catfish (Carlarius parkii). Both species showed one spawning season between May and June. Nevertheless, as these are mouth brooding species, we have considered that the reproduction season may be underway until August. Mean fork length of females at first maturity was ∼40 cm for A. latiscutatus and 35 cm for C. parkii, corresponding to 4–5 years for both species. Higher fecundity was found in larger females, with a mean of 45 and 26 eggs for A. latiscutatus and C. parkii, respectively. Differences recorded in sex ratio throughout the year suggest that females can leave the study area after the spawning season or that differences in behaviour may lead to differential sex catchability. The two species showed similar growth curves, despite A. latiscutatus reaching larger lengths at the same age. Estimated length–weight relationships suggest that both species present a positive isometric growth pattern. Our results highlight the slow life-history strategy of the two studied catfish species, thus emphasizing their vulnerability to fishing activities. We suggest that a short-term fishing closure during the spawning period (May–June) in the PNBA may be an important management measure to ensure reproduction opportunities for both species and, therefore, guarantee fishing sustainability.

Early-life effects on body size in each sex interact to determine reproductive success in the burying beetle Nicrophorus vespilloides.

Early-life conditions have been shown to have a profound effect on an animal's body size and fecundity across diverse taxa. However, less is known about how early-life effects on fecundity within each sex interact to determine reproductive success. We used experiments with burying beetles Nicrophorus vespilloides to analyse this problem. The nutritional conditions experienced by burying beetles in early life are a key determinant of adult body size in both sexes, and adult body size in turn influences male reproductive tactics. In previous work, we showed that smaller males are more effective than larger males at stimulating virgin female fecundity. In this study, we manipulated male and female body size by restricting access to food in early development. We then conducted breeding assays, in which small and large females were mated sequentially with small and large males, and then allowed to raise offspring without paternal care. We tested whether large females, which are potentially more fecund, laid even more eggs when mated with small males. We found no evidence to support this prediction. Instead, we detected only a weak non-significant trend in the predicted direction and no equivalent trend in the number of larvae produced. However, we did find that larvae attained a greater mass by the end of development when their mother was large and mated with a small male first. We suggest that large females might have evolved counter-measures that prevent exploitation by small fecundity-stimulating males, including partial filial cannibalism. By eating surplus larvae during reproduction, larger females would leave more of the carrion for their offspring to consume. This could explain why their surviving larvae are able to attain a greater mass by the time they complete their development.

Life history of the river goby Glossogobius callidus (Teleostei: Gobiidae).

The river goby Glossogobius callidus is native to freshwater and estuarine habitats in South Africa. Individuals [21.1-144.4 mm total length (LT )] were sampled from impoundments in the Sundays River Valley, Eastern Cape, from February 2014 to March 2015. The largest female was 137.2 mm LT , and the largest male was 144.4 mm LT . Length-at-50% maturity was 75.2 ± 2.1 mm LT for males and 76.2 ± 2.0 mm LT for females. Absolute fecundity was 1028.2 ± 131.7 oocytes per fish, and relative fecundity was 50.1 ± 18.1 oocytes per gram. The spawning season extended from October to December. Fish were aged using sectioned sagittal otoliths. The growth zone periodicity was validated using edge analysis. Longevity was more than 7 years for females and more than 6 years for males. Length-at-age was similar for the two sexes and was best described using the von Bertalanffy growth model as Lt = 74.7(1 - e-1.0(t + 0.1) ) mm LT for the entire population. Using the population age structure, the mortality rate was estimated at 1.3 per year.

Size and shape assortative mating in Japanese beetles (Popilliajaponica)

Assortative mating is hypothesized to be a product of sexual selection, mating constraints, or temporal autocorrelation. I test these hypotheses in the Japanese beetle (Popillia japonica Newman, 1841), a sexually size dimorphic invasive insect pest in North America, by measuring the size and shape of bodies and wings of pair members in a wild population. Because male P. japonica prefer to mate with larger females and larger males outcompete rivals for mating opportunities, sexual selection is expected to produce size-related assortative mating. The current study did not support this hypothesis. The mating constraints hypothesis was also not supported because beetle pairs did not have similar body shapes. I, however, did find support for the temporal autocorrelation hypothesis as the wing size and shape of pair members were significantly correlated. This mating pattern likely arises due to individuals with larger and more slender wings arriving earlier at aggregation sites and pairing according to their arrival sequence. Although I found less support for the sexual selection hypothesis, I argue that mate choice might play an important, but secondary, role to temporal autocorrelation in explaining assortative mating in Japanese beetles.