Reproductive Life History Research Articles

HAVE MALE AND FEMALE GENITALIA COEVOLVED? A PHYLOGENETIC ANALYSIS OF GENITALIC MORPHOLOGY AND SEXUAL SIZE DIMORPHISM IN WEB-BUILDING SPIDERS (ARANEAE: ARANEOIDEA)

Sexual size dimorphism (SSD) can strongly influence the evolution of reproductive strategies and life history. If SSD is extreme, and other characters (e.g., genitalic size) also increase with size, then functional conflicts may arise between the sexes. Spiders offer an excellent opportunity to investigate this issue because of their wide range of SSD. By using modern phylogenetic methods with 16 species of orb-weaving spiders, we provide strong evidence for the "positive genitalic divergence" model, implying that sexual genitalic dimorphism (SGD) increases as SSD increases. This pattern is supported by an evolutionary mismatch between the absolute sizes of male and female genitalia across species. Indeed, our findings reveal a dramatic reversal from male genitalia that are up to 87x larger than female genitalia in size-monomorphic species to female genitalia that are up to 2.8x larger in extremely size-dimorphic species. We infer that divergence in SGD could limit SSD both in spiders, and potentially in other taxa as well. Further, male and female body size, as well as male and female genitalia size, are decoupled evolutionarily. Finally, we show a negative scaling (hypoallometry) of male and female genitalic morphology within sexes. Evolutionary forces specific to each sex, such as larger female size (increased fecundity) or smaller male size (enhanced mate-searching ability), may be balanced by stabilizing selection on relative genitalic size.

Status of galaxiid fishes in Tasmania, Australia: conservation listings, threats and management issues

Abstract Fish of the family Galaxiidae are restricted to the southern hemisphere where they occupy a diverse array of habitats ranging from over 2000 m in elevation to sea level. Some species are diadromous and, hence, freshwater, estuarine and marine habitats are used during their life‐cycle; other species complete their entire life‐cycles in freshwater environments. Tasmania has a diverse galaxiid fauna that accounts for 64% of native freshwater fish species found on the island. The Tasmanian galaxiid fauna is characterized by high species richness (5 genera and 16 species), endemism (11 species), restricted distributions, and non‐diadromous life histories (11 species). The galaxiid fauna of Tasmania has significant conservation status with 69% of species considered ‘threatened’. The conservation status of the fauna is recognized at State, national and international levels. The key threats to galaxiids in Tasmania are exotic species, hydrological manipulations, restricted distributions, general habitat degradation and exploitation of stocks. Although work has recently been undertaken to conserve and manage Tasmanian galaxiid populations, the fauna is still thought to be imperilled. Knowledge gaps that need to be addressed include the biology and ecology of most species (e.g. reproductive biology, life histories, habitat use and requirements) and impacts of habitat manipulations, as well as mechanisms and impacts of interactions with exotic species. Techniques to monitor accurately the status of galaxiid species and their populations need to be developed and the coexistence of some galaxiids with introduced salmonids should also be examined. Copyright © 2005 John Wiley & Sons, Ltd.

LIFE HISTORY STRATEGIES IN EXTREME ENVIRONMENTS: COMPARATIVE DEMOGRAPHY OF ARCTIC AND ALPINE PTARMIGAN

Arctic and alpine habitats are extreme environments characterized by short breeding seasons, cold temperatures, limited food availability, and potentially high predation rates. Stringent ecological conditions are likely to have important consequences for the evolution of life history traits, but direct empirical tests are few. We compare the demog- raphy of three populations of ptarmigan on an environmental gradient spanning alpine, subalpine, and arctic habitats. Female Willow Ptarmigan (Lagopus lagopus) and White- tailed Ptarmigan (L. leucurus) breeding at subalpine and alpine sites had smaller clutches and lower probabilities of nesting success, fledging success, and renesting than Willow Ptarmigan nesting at a low-elevation arctic site. Annual fecundity, measured as female fledglings per breeding female, did not overlap among the three populations and was ranked: alpine (0.40 6 0.08, mean 6 SE, 95% CI 5 0.26-0.58) , subalpine (1.33 6 0.10, 1.13- 1.54) , arctic (2.04 6 0.18, 1.68-2.39). There was a nonsignificant trend for apparent survival rates (f) of breeding females to vary in the opposite direction: alpine (0.46 6 0.04) . subalpine (0.43 6 0.03) . arctic (0.37 6 0.06). Population growth rates predicted significant declines for the alpine population ( l5 0.65 6 0.07, 95% CI 5 0.52-0.79), but not the subalpine ( l5 1.00 6 0.07, 0.86-1.14) or arctic populations ( l5 1.13 6 0.20, 0.78-1.54). The adjusted estimates of survival necessary to sustain a stationary population indicated that actual variation in female survival was more pronounced than the observed rates: alpine (0.71) . subalpine (0.43) . arctic (0.33). Together, the fecundity and survival values provide evidence that even congeneric populations can exhibit a continuum between high reproductive and survivor life history strategies. Variation in ptarmigan life history traits was consistent with population differences in predation rates on eggs and breeding females, and it was not related to duration of the breeding season, climatic conditions, or food availability. Ptarmigan demography also covaried with body size, but not in the predicted pattern. Overall, the life history strategies of ptarmigan are consistent with our current understanding of the impacts of environmental factors upon life history variation in passerine songbirds.

Identifying sources of variation in reproductive and life-history traits among five populations of a Chinese lizard (Takydromus septentrionalis, Lacertidae)

Research on life-history traits of squamate reptiles has focused on North American species, while Asian taxa have been virtually ignored. In order to understand general patterns in reptile life histories, we need a broader data base. Our study on the slender-bodied lacertid lizard Takydromus septentrionalis provides the first detailed information on factors responsible for intraspecific variation in reproductive output and life history in a Chinese reptile. Clutches of recently collected lizards from five widely separated localities in China revealed major divergences in female body size at maturation, mean adult female body size, body condition after oviposition, size-adjusted fecundity, relative clutch mass, and mass and shape of eggs. Most of these geographical differences persisted when the same groups of females were maintained in identical conditions in captivity. Additionally, reproductive frequency during maintenance under laboratory conditions differed according to the animals’ place of origin. Thus, the extensive geographical variation in reproductive and life-history traits that occurs within T. septentrionalis is exhibited even in long-term captives, suggesting that proximate factors that vary among localities (local conditions of weather and food supply) are less important determinants of life-history variation than are intrinsic (presumably genetic) influences. The maternal abdominal volume available to hold the clutch may be one such factor, based on low levels of variation in Relative Clutch Mass among populations, and geographical variation in the position of trade-off lines linking offspring size to fecundity. © 2005 The Linnean Society of London, Biological Journal of the Linnean Society, 2005, 85, 443–453.

Stalk-eyed flies

Stalk-eyed flies

Fish Stocks in the Southern Scotia Arc Region—A Review and Prospects for Future Research

We provide a summary of biological aspects and population trends of demersal finfish stocks in the southern Scotia Arc region of Antarctica. Information presented here, drawn largely from recent scientific research surveys, includes aspects of species composition, biomass and stock structure, reproduction and early life history, age, growth, and natural mortality, and diet. Although Antarctic fish faunal groups overlap in the southern Scotia Arc, the region is dominated by species of low-Antarctic origin both in terms of biomass and number of species. Several basic biological parameters of the abundant fish species in the southern Scotia Arc are comparatively well known, though less so in the South Orkney Islands than the South Shetland Islands. These stocks suffered substantial declines as a result of commercial exploitation of mackerel ice fish, Champsocephalus gunnari, and marbled notothenia, Notothenia rossii, in the late 1970s and mid 1980s. This led to a moratorium on directed fishing in 1989–90 which remains in effect. At present, several stocks, with the exception of these two species, appear to have recovered. A number of important biological features, such as age, growth, mortality, and the early life history of most species are still poorly understood. Key biological research needs are identified.

Recent biological invasion may hasten invasional meltdown by accelerating historical introductions

Biological invasions are rapidly producing planet-wide changes in biodiversity and ecosystem function. In coastal waters of the U.S., >500 invaders have become established, and new introductions continue at an increasing rate. Although most species have little impact on native communities, some initially benign introductions may occasionally turn into damaging invasions, although such introductions are rarely documented. Here, I demonstrate that a recently introduced crab has resulted in the rapid spread and increase of an introduced bivalve that had been rare in the system for nearly 50 yr. This increase has occurred through the positive indirect effects of predation by the introduced crab on native bivalves. I used field and laboratory experiments to show that the mechanism is size-specific predation interacting with the different reproductive life histories of the native (protandrous hermaphrodite) and the introduced (dioecious) bivalves. These results suggest that positive interactions among the hundreds of introduced species that are accumulating in coastal systems could result in the rapid transformation of previously benign introductions into aggressively expanding invasions. Even if future management efforts reduce the number of new introductions, given the large number of species already present, there is a high potential for positive interactions to produce many future management problems. Given that invasional meltdown is now being documented in natural systems, I suggest that coastal systems may be closer to this threshold than currently believed.

Male Reproductive Timing in Rhesus Macaques Is Influenced by the 5HTTLPR Promoter Polymorphism of the Serotonin Transporter Gene1

The 5HTTLPR polymorphism in the promoter region of the human serotonin transporter (SLC6A4) gene is known to be associated with various stress-related psychological and psychiatric phenomena. We observed that a similar diallelic polymorphism in the orthologous gene of rhesus macaques (Macaca mulatta) was related to the reproductive life history of 580 males residing in the free-ranging colony of Cayo Santiago, Puerto Rico, between 1985 and 1998. At first glance, the polymorphism appeared to be selectively neutral because no difference in total reproductive output was noted between males of different 5HTTLPR genotypes. However, whereas heterozygotes were significantly more reproductive than homozygotes at intermediate age (10-13 yr), the opposite held true before and after this period (n = 682 offspring; randomization P = 0.014). This association, which explains approximately 7% of the observed variation in sire age, most likely reflects different natal dispersal patterns and represents the first reported instance of a genetic influence on reproductive timing in mammals.

Selected Life-History Observations on the Cayman Gambusia, Gambusia xanthosoma Greenfield, 1983 (Poeciliidae)

The Cayman gambusia (Gambusia xanthosoma Greenfield, 1983) is an uncommon species within the G. punctata species group, endemic to North Sound, Grand Cayman Island, BWI. Since the original description (Greenfield 1983) only phylogenetic information has been published and little is known of its habitat, feeding ecology, or reproductive life history (Wildrick and Greenfield 1985, Rauchenberger 1988). Originally described from a brackish-water (30 psu) mosquito control ditch, the species also occurred throughout marine mangrove habitat and inland saline ponds adjacent to North Sound, Grand Cayman Island. Here we present information on the habitat, diet, reproduction, life history, and parasites of the Cayman gambusia.

HAVE MALE AND FEMALE GENITALIA COEVOLVED? A PHYLOGENETIC ANALYSIS OF GENITALIC MORPHOLOGY AND SEXUAL SIZE DIMORPHISM IN WEB-BUILDING SPIDERS (ARANEAE: ARANEOIDEA)

Sexual size dimorphism (SSD) can strongly influence the evolution of reproductive strategies and life history. If SSD is extreme, and other characters (e.g., genitalic size) also increase with size, then functional conflicts may arise between the sexes. Spiders offer an excellent opportunity to investigate this issue because of their wide range of SSD. By using modern phylogenetic methods with 16 species of orb-weaving spiders, we provide strong evidence for the "positive genitalic divergence" model, implying that sexual genitalic dimorphism (SGD) increases as SSD increases. This pattern is supported by an evolutionary mismatch between the absolute sizes of male and female genitalia across species. Indeed, our findings reveal a dramatic reversal from male genitalia that are up to 87x larger than female genitalia in size-monomorphic species to female genitalia that are up to 2.8x larger in extremely size-dimorphic species. We infer that divergence in SGD could limit SSD both in spiders, and potentially in other taxa as well. Further, male and female body size, as well as male and female genitalia size, are decoupled evolutionarily. Finally, we show a negative scaling (hypoallometry) of male and female genitalic morphology within sexes. Evolutionary forces specific to each sex, such as larger female size (increased fecundity) or smaller male size (enhanced mate-searching ability), may be balanced by stabilizing selection on relative genitalic size.

Nest design and the abundance of parasitic Protocalliphora blow flies in two hole-nesting passerines

:Ectoparasites dwelling in bird nests regularly reduce reproductive success and condition of breeding birds. Thus, establishing the factors that determine the abundance of ectoparasites is important for better understanding of reproductive trade-offs and life history evolution in birds. A recent hypothesis states that interspecific differences in the abundance of ectoparasites may be caused by nest composition. For example, great tits (Parus major) have nests made of mosses and fur, whereas Ficedula flycatchers have nests made of grasses, bast, and bark, and tits are more infested by nest-dwelling ectoparasites than flycatchers. We swapped nests between pairs of great tits and collared flycatchers (F. albicollis) during egg-laying or early incubation and counted parasitic Protocalliphora blow flies at the end of breeding to test this hypothesis experimentally. We controlled statistically for habitat (oak versus spruce forest), brood size, season, year, and mean nestling weight before fledging. We found a significant effect of bird species (tit > flycatcher), habitat (oak > spruce), and year. There was no effect of nest type. Consequently, the hypothesis ascribing the different abundance of ectoparasites in great tits and collared flycatchers to different nest composition was not supported by our study.

Age-related differences in serum gonadotropin (FSH and LH), salivary testosterone, and 17-? estradiol levels among Ache Amerindian males of Paraguay

Age-related differences in serum luteinizing hormone (LH), follicle-stimulating hormone (FSH), salivary testosterone, and 17-beta estradiol levels are reported for Ache Amerindian males (n = 17; mean age, 37.1 +/- 14.2 SD) of Paraguay in order to explore population variation in patterns of male reproductive senescence in a foraging/agricultural community. Hormone associations were examined to test various hypotheses for age-related differences in hypothalamic-pituitary function. Significant increases in FSH (r = 0.75, P < 0.0005) and LH (r = 0.65, P < 0.01) were noted in association with aging. No significant correlation was observed between morning or evening testosterone and age. Morning and evening estradiol levels were associated with morning and evening testosterone, respectively (morning, r = 0.53, P = 0.05; evening, r = 0.63, P = 0.02). Evening estradiol was also positively associated with LH (r = 0.66, P = 0.02), suggesting testicular production to be an important source of circulating estradiol. Morning estradiol tended to rise with age, but was not significant (r = 0.39, P = 0.15). Anthropometric measurements of height, weight, body mass index, and fat percent did not change significantly with age. In contrast to testosterone, age-related differences in gonadotropin levels may be independent of energetic status, less variant, and more universal among male populations. Implications for gonadotropin function and aging on human male reproductive senescence and life histories are discussed.

Reproductive bionomics and life history traits of three gammaridean amphipods, Cymadusa filosa Savigny, Ampithoe laxipodus Appadoo and Myers and Mallacoota schellenbergi Ledoyer from the tropical Indian Ocean (Mauritius)

The reproductive bionomics and life history traits of two corophiid amphipods (Ampithoe laxipodus, Cymadusa filosa) and one melitid (Mallacoota schellenbergi) were studied in Mauritius (Indian Ocean) for the period March 1999 to February 2000. Results on the population structure, monthly size class variations, sex ratio, female reproductive states and fecundity are presented. The study demonstrates multivoltinism and continuous reproduction in the three species. Increase in number of juveniles was observed in warmer months for C. filosa and A. laxipodus. Sexual maturity was attained at smaller sizes in warmer months in the three species. Linear relationship on body length and number of eggs in brood pouch are presented. Size-independent analysis of egg number revealed a decrease in number of eggs in cooler months. Sex ratio is male skewed in M. schellenbergi and female skewed in C. filosa and A. laxipodus. Some of the plausible explanations for the reproductive strategies adopted by these three species in a tropical system are discussed.

Women's Autonomy and Demographic Behaviour

Women's status is a multidimensional concept. A growing body of literature strongly suggests that gender inequality has a significant impact on the demographic transition and on the socio-economic development of countries. The aim of this paper is to investigate the relationships between fertility and women's autonomy in different cultural contexts. Data collected through three surveys conducted in Botswana, South Africa and Rajasthan are analysed. Women, aged 15-49, were interviewed to obtain information about their reproductive life histories and educational and work status. Regression models and causal log-linear models are applied to describe the role of different aspects of women's autonomy on fertility. The results of the analysis carried out show some similarities and also very large differences. In particular, the women of Rajasthan have less autonomy (in terms of women's status) than do the women of Botswana and South Africa.

Life history variation in cupuladriid bryozoans from either side of the Isthmus of Panama

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 280:145-161 (2004) - doi:10.3354/meps280145 Life history variation in cupuladriid bryozoans from either side of the Isthmus of Panama Aaron O¹Dea1,2,*, Amalia Herrera-Cubilla1, Helena Fortunato1, Jeremy B. C. Jackson1,2 1Center for Tropical Paleoecology and Archeology, Smithsonian Tropical Research Institute, Box 2072, Balboa, Ancon, Republic of Panama 2Geosciences Research Division, Scripps Institution of Oceanography University of California, San Diego La Jolla, California 92093-0244, USA *Email: odeaa@si.edu ABSTRACT: Cupuladriid bryozoans are able to produce new colonies both sexually through the production of larvae and asexually via fragmentation. The prevalence of asexual propagation and the physical and biological processes of fragmentation in cupuladriid species are currently little understood. In a large survey comprising collections of nearly 32000 cupuladriids from either side of the Isthmus of Panama, patterns of cupuladriid species richness, occurrence and abundance were measured together with levels of asexual propagation, fragmentation and regeneration. The Caribbean side is characterised by greater cupuladriid diversity and dominance of the genus Cupuladria over Discoporella while the eastern Pacific coast is characterised by lower cupuladriid diversity and complete dominance of Discoporella. Life history variation was not found to be constrained by phylogeny and no systematic differences were found in life history or morphologies between Cupuladria and Discoporella to explain the patterns in generic dominance across the isthmus. Nonetheless, striking differences occur in life history strategies across the isthmus. Eastern Pacific species tend to be large, flat and lightly calcified, resulting in high levels of fragmentation and hence asexual propagation. Conversely, Caribbean species produce a wider range of morphologies, including small, highly domed and highly calcified colonies that protect from fragmentation. By correlating colony morphologies with reproductive life histories within species, we show that morphologies, particularly colony strength and size, control levels of fragmentation and thus mode of propagation in cupuladriids. Life history strategies that promote asexual propagation are found to track levels of primary productivity both between oceans across the isthmus and between regions within oceans. KEY WORDS: Asexual · Sexual · Life history · Cupuladriid · Bryozoa · Reproduction · Panama Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 280. Online publication date: October 14, 2004 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2004 Inter-Research.

Prevalence of menstrual pain in relation to the reproductive life history of women from the Mayan rural community

Background: The prevalence of menstrual pain in Western societies is relatively high and has been shown to be related to many factors (e.g. age, menarche age, parity, menstrual cycle regularity, cigarette smoking, dietary habits). However, less data are available for traditional societies, within which there are, presumably, not as many potentially disturbing factors that could influence menstrual symptoms as in Western societies.Aim: The study seeks to determine the prevalence of dysmenorrhoea, and the factors related to menstrual pains in women with natural fertility (i.e. without hormonal forms of contraception).Subjects and methods: 177 non-smoking women between 18 and 45 years of age living in one Mayan village (Yaxcaba, Yucatan, Mexico) were the subjects of this study. The method of logistic regression was used with the dichotomous dependent variable being the presence or absence of menstrual pain together with such independent variables as age, age at menarche, number of pregnancies, age when giving birth to the first child, the weight at interview and BMI.Results: The general prevalence of the menstrual pains was 28%. There was only one variable influencing dysmenorrhoea, namely the age at which women give birth to their first children. Those mothers who gave birth to their first child at an earlier age (at mean age of 19.4 vs 21.1 years) had a lower prevalence of dysmenorrhoea.Conclusion: In the studied traditional society the main factor related to menstrual pain was the age at which woman first gave birth. It is hypothesized that an earlier start to reproductive life in some way decreases the sensitivity of the uterus to prostaglandins.

Reproductive Biology of Palaemon Gravieri (Decapoda: Caridea: Palaemonidae)

Breeding and recruitment patterns were described and analyzed in a population of Palaemon gravieri inhabiting warm-temperate waters of southern Korea. Breeding period was seasonal, beginning in March, peaking (89% ovigerous females) in May, and then ending by August. Females with embryos near hatching had ovaries filled with vitellogenic oocytes ready for new spawning, indicating successive spawning. Laboratory observations on females incubating embryos confirmed that they spawn again after incubated embryos hatch; the female then underwent a post-hatching molt and then never had further ovarian development and spawning, indicating that the female has just two broods per year. Breeding period was constrained by temperature, and release of larvae coincided with a plankton bloom in the sampling area. Females reached sexual maturity and produced a brood in their first year, overwintered, and produced a brood again the following summer. Reproductive output (effort) of the female was rather high. No significant relationship was found between female size and embryo size. Embryo volume was relatively small, indicative of small amount of energy allocation to each embryo. Embryo loss during incubation was not high. Recruitment of juveniles was closely linked to the breeding period, beginning in July and ending in September. Reproductive life history traits for P. gravieri seem to be closer to stochastic (bet-hedging) models in which adults live in stable environments but in which juvenile (= larval) mortality is variable.

Systemic mechanisms of individual reproductive life history in female Medflies

This paper is the second one in a series of two papers hypothesizing and testing systemic grounds of reproductive life history in the female fruit fly. In the first paper, we analyzed mechanisms of individual fecundity scheduling and have drawn the following conclusions. 1. Individual fecundity in female flies is endowed as a flat pattern with a steady-state period of a constant rate of egg-laying. An individual female reveals three stages in her adult life history: maturation, maturity, and senescence. The first stage is a transient period of achieving a steady state at maturity, which can be maintained until the senescence stage. 2. Thus, an individual fecundity pattern has no maximum. The maximums observed experimentally are averaging-caused artifacts. 3. Two natural causes of deaths exist in flies, senescence-caused ones and premature deaths, probably due to a reproductive overload. In this paper, to confirm these findings, we use individual daily scores of egg-laying in four populations of Mediterranean fruit flies. Based on fecundity scores, we divide each Medfly population into four classes, namely zero-egg, short-, medium- and long-lived egg-layers. We demonstrate that, indeed, the three above findings definitely exist in Medflies. Our procedure allows the efficient storage of individual fecundity in parametric form, with only five numbers for each fly. Finally, this protocol will allow a more precise analysis of fecundity-energy trade-offs in flies carrying appropriate longevity mutations.

Antimicrobial egg cleaning by the fringed darter (Perciformes: Percidae:Etheostoma crossopterum): implications of a novel component of parental care in fishes

Broad-spectrum antimicrobial compounds have recently been identified in the epidermal mucus of fishes and probably serve as a first line of defence against microbial pathogens. Because of the ubiquitous nature of fungi and bacteria in aquatic systems, defence against these pathogens should be required throughout the lifespan of fishes, including the egg stage. We conducted experiments on Etheostoma crossopterum (Percidae: Catonotus), the fringed darter, to determine if the presence of a guarding male inhibits microbial colonization of eggs. Based on results from a combination of in-stream experiments, in vitro microbial assays, and morphological characteristics and behaviour of breeding males, we propose that antimicrobial egg cleaning by the guarding male is an effective component of parental care in these fish. Although innate antimicrobial compounds have been identified in a variety of organisms ranging from insects to vertebrates, integration of these compounds into a species's reproductive life history has been identified only in a small number of insect species. The results from this study not only indicate that E. crossopterum males provide a novel form of vertebrate parental care, but also have implications regarding the evolution of parental care in fishes and transitional evolutionary stages from no parental care to male parental care.

Reproductive biology of the common shrimp Crangon crangon (Decapoda: Crangonidae) in the central Irish Sea

Aspects of the reproductive biology of the common shrimp Crangon crangon (L.) were studied in Port Erin Bay, Isle of Man, Irish Sea. Size at sexual maturity was determined from the proportions of ovigerous females and of females with maturing ovaries. The size at which 50% of females are mature is estimated (±95% confidence intervals) as 12.5±0.48 mm carapace length. Based on the proportions of ovigerous females and of mature females, the main breeding season was from January to June. Mean ovarian dry weights indicated two broods (winter and summer), with females bearing winter broods (WB) having higher gonad indices than those with summer broods (SB). WB females with non-eyed eggs and with eyed eggs differed in the regression of ovarian dry weight on carapace length, indicating preparation for laying a second brood. In both broods the moult stages of berried females were related to egg stage. Moulting will occur following the release of the brood. During embryonic development, mean egg length and egg volume were larger in all stages, and the mean dry weight of individual eggs of all stages heavier, in WB than in SB; there was no difference in egg number, however. Consequently, reproductive investment, the proportion of female weight devoted to egg production, was 67% higher in WB (0.20±0.04) than in SB (0.12±0.03). There is a significant effect of egg volume on brood weight, but not on egg number. In both broods, egg number was a negatively allometric function of female body size in non-eyed eggs and an isometric function of female body size in eyed eggs. Brood mortality during incubation was higher in SB (17%) than WB (10%). Differences in the reproductive variables and investment between the two broods of C. crangon are discussed in the light of reproductive strategies and life history.