Growth, size and age at maturity of the agile frog (Rana dalmatina) in an Iberian Peninsula population

The mean age of a population of agile frogs (Rana dalmatina) from the Iberian Peninsula was estimated using mark and recapture and skeletochronology. Life-history parameters, including growth rate, body length, age and size at maturity, sexual dimorphism and longevity, were studied. The regression between age and snout-vent length (SVL) was highly significant in both sexes. Males reached sexual maturity at two years of age, although sometimes they can reach it at only one year of age. The average SVL at maturity was 51.75 mm (standard error (SE) = 0.71; n = 45). Females reached sexual maturity at two years of age with an average SVL of 62.14 mm (SE = 2.20; n = 14). A subset of the female population reached sexual maturity at three years of age. Growth was rapid until sexual maturity was reached. There was an overlap of SVL between different age classes. Growth was continuous, fulfilling the conditions of Von Bertalanffy's model. The growth coefficient (K) was 0.840 in males and 0.625 in females. The maximum SVL was greater in females (73.00 mm) than in males (59.50 mm). Sexual dimorphism was significantly biased towards females in all age classes. The maximum longevity observed was 6 years in females and 8 years in males. Management strategies for agile frogs should take into account factors such as these life-history characteristics.     

Size Matters: Individual Variation in Ectotherm Growth and Asymptotic Size

Body size, and, by extension, growth has impacts on physiology, survival, attainment of sexual maturity, fecundity, generation time, and population dynamics, especially in ectotherm animals that often exhibit extensive growth following attainment of sexual maturity. Frequently, growth is analyzed at the population level, providing useful population mean growth parameters but ignoring individual variation that is also of ecological and evolutionary significance. Our long-term study of Lake Erie Watersnakes, Nerodia sipedon insularum, provides data sufficient for a detailed analysis of population and individual growth. We describe population mean growth separately for males and females based on size of known age individuals (847 captures of 769 males, 748 captures of 684 females) and annual growth increments of individuals of unknown age (1,152 males, 730 females). We characterize individual variation in asymptotic size based on repeated measurements of 69 males and 71 females that were each captured in five to nine different years. The most striking result of our analyses is that asymptotic size varies dramatically among individuals, ranging from 631–820 mm snout-vent length in males and from 835–1125 mm in females. Because female fecundity increases with increasing body size, we explore the impact of individual variation in asymptotic size on lifetime reproductive success using a range of realistic estimates of annual survival. When all females commence reproduction at the same age, lifetime reproductive success is greatest for females with greater asymptotic size regardless of annual survival. But when reproduction is delayed in females with greater asymptotic size, lifetime reproductive success is greatest for females with lower asymptotic size when annual survival is low. Possible causes of individual variation in asymptotic size, including individual- and cohort-specific variation in size at birth and early growth, warrant further investigation.     

Sexual size dimorphism,growth, and maturity of the fluvial eight-barbel loach in the Kako River,Japan

The maturation and growth pattern of the fluvial eight-barbel loach Lefua sp. (Japanese name: nagare-hotoke-dojo), an endangered species, was investigated using an individual identification-recapture method from 1995 to 1998 in an upper reach of a headwater tributary of the Kako River, Hyogo Prefecture, Japan. Based on observations of the gonads through the abdominal skin, the loach was estimated to breed mostly from May to July. All the males matured by age 1⁺, and all the females matured by age 2⁺. Gamete release in all individuals of both males and females was predicted from recaptured loaches during each breeding season. The standard length of mature females was significantly larger than that of males, showing sexual size dimorphism (SSD). The maximum sizes recorded were 75.4 mm SL for females and 61.2 mm SL for males. Both males and females of immature specimens grew mainly from May to November, including the breeding season, with no significant differences in growth rates between them. After sexual maturity, both males and females grew mainly from July to October (or November), after the breeding season, and the females exhibited higher growth rates than males. Therefore, SSD of the species seems to be attributable to the different growth rates after maturity. The longevity of the loach was estimated to exceed ten years based on individual growth patterns of various sizes during the survey period. It is likely that the loach has an iteroparous life history, breeding every year, and moderate growth rates after maturity.     

Reproductive cycle,sexual maturity and longevity of Odontophrynus americanus (Anura: Odontophrynidae) in South Brazil

Studies on the reproductive biology and age of amphibians provide primary information about the life history and population demographic parameters of species. Here, we describe the reproductive cycle, size–fecundity relationships, reproductive effort, sexual dimorphism and sexual maturity of Odontophrynus americanus, the flood frog, from South Brazil. A total of 96 individuals were analysed. The reproductive cycles of males and females were described through morphoanatomical analysis of testis and ovary. Age at onset of sexual maturity and estimated longevity were determined by skeletochronology. Individuals of O. americanus presented a potentially continuous reproductive cycle with a peak of reproductive activity in the warmer months. Females presented a higher reproductive investment than males. Sexual maturity was reached at around one year of age for both sexes while longevity differed between the sexes, with females living up to six years and males up to ten years. No evidence of sexual size dimorphism was found. This study is among the few that have assessed age at sexual maturity and longevity in a Neotropical anuran. Basic aspects of life history are of paramount importance because they allow comparisons and test of hypotheses to be made, which can help to build generalizations about the evolutionary meaning of ecological strategies.     

Postmetamorphic growth,survival, and age at first reproduction of the salamander,hynobius nebulosus tokyoensis Tago in relation to a consideration on the optimal timing of first reproduction

The postmetamorphic growth and survival of the salamander Hynobius nebulosus tokyoentisTago were surveyed in the study site located in Habu village of Hinodemachi, a suburb of Tokyo City, during 1975–1981. A laboratory experiment on the growth rate of juveniles was conducted in parallel with the field survey. The result indicated that this salamander grew at the rate of 8,mm in s.v.l. per year during the juvenile stage, but its growth rate decreased markedly as low as 1.8 mm for males and 1.1 mm for females, once it had attained sexual maturity. According to the “capture-recapture” procedure the annual survival rate after metamorphosis was found to be quite high; that is, approximately 0.7. By using the growth rate of juveniles and the difference between the sizes at metamorphosis and sexual maturity, the age at first reproduction was estimated to be 4 year for males and 5 year for females. From the data obtained in this study, the intrinsic rates of increase (r) were calculated for various values of age at first reproduction under different survival schedules, and the relationship between the age at first reproduction and fitness as measured by r was examined. The result indicated that an optimal age maximizing fitness always existed under respective survival schedules, and the observed age at first reproduction of this salamandei was found to coincide well with the predicted optimal age.     

Influence of age at mating on the reproductive performance of Parthenium beetle,Zygogramma bicolorata (Coleoptera: Chrysomelidae)

Abstract Age-specific mating incidence, sexual maturation and effect of age at mating on reproductive performance of the Parthenium beetle, Zygogramma bicolorata Pallister, was studied. Based on 50% mating incidence the calculated age of sexual maturation of males and females was 10.5 and 11.1 days, respectively, which was not statistically significant. However, on the basis of age at first mating, that is, sexual maturity, females matured 2 days earlier than males. Fecundity, pre-oviposition, oviposition and post-oviposition period and female longevity appear to be influenced by female age at mating with reproductive performance peaking at 30 days. On the other hand, egg viability was influenced by male age and was highest when males mated at the age of 40 days. To summarise, egg production and timing of egg deposition was female age-dependent, whereas egg fertility was male age-dependent. It was also observed that females mated at a later age and laid a higher number of eggs immediately after mating than did earlier mated females. This was ostensibly in a bid to increase fitness by maximizing reproductive output in the reduced life span available. This is the first investigation on the effect of age of females at mating on reproduction in this beetle.     

Breeding rate is associated with pheomelanism in male and with eumelanism in female barn owls

Melanin-based coloration exists in 2 types: black eumelanismand reddish-brown pheomelanism, which both have a strong heritablecomponent. To test whether these 2 types of melanism are associatedwith alternative adaptations, we carried out a correlative studyover 8 years and an experiment in a Swiss population of barnowls, Tyto alba. This species varies in coloration from reddish-brownto white and from lightly to heavily marked with black spots.Based on the fact that plumage coloration and spottiness aremale- and female-specific secondary sexual characters, respectively,we examined whether the probability of breeding is associatedwith the degree of pheomelanism in males and of eumelanism infemales. In males, recruited nestlings were significantly lessreddish-brown than their nonrecruited nest mates. In females,individuals displaying larger black spots started to breed ata younger age and had a higher survival, and females with experimentallyreduced plumage spottiness bred less often than control females.Therefore, in the barn owl, the degree of male pheomelanismis associated with the probability of being recruited in thelocal population, whereas the degree of female eumelanism correlateswith age at sexual maturity, survival probability, and alsothe probability of skipping reproduction.     

Seed Longevity of Rice Cultivars and Strategies for their Conservation in Genebanks

Changes in seed quality during ripening were studied in sixteencultivars of rice, representing the three ecogeographic racesofOryza sativa, and one cultivar ofO. glaberrima, grown duringone dry season (Nov. –May) 1992 –1993 at Los Baños, Philippines. Mass maturity (defined as the end ofseed filling period) among the cultivars was attained between18.5 and 21.6d after anthesis (DAA). The seed moisture contentat mass maturity varied between 24 and 40%. Germination abilityof seeds in the early stages of development varied significantly,but as mass maturity approached, germination increased to themaximum and no significant differences were found among cultivars.The seeds were stored hermetically at 35 °C with 15±0.2%moisture content and the resultant seed survival data were analysedby probit analysis. Potential longevity (quantified by the valueof seed lot constantK_iof the seed viability equation) was greatestbetween 33 and 37 DAA, i.e. about 2 weeks after mass maturity.The stage during development at which seeds achieve maximumpotential longevity is described by the term storage maturity.Lowlandjaponicacultivars, large seeded accessions (seed mass40mg) andO. glaberrimahad shorter storage longevity ( , standarddeviation of the frequency of seed deaths in time=1.47 weeks)while cultivars with purple pericarp survived longer than othercultivars ( =2.33 weeks). The initial germination of thejaponicacultivarsat storage maturity was high (99 –100%) and the estimatesof maximum potential longevity (K_i) which ranged between 3.3(Shuang cheng nuo) and 4.4 (Minehikare) were close to thoseof theindicacultivars. This research suggests that seed production environment betweenNov. and May at Los Ba ños is benign for the temperatejaponicacultivars.The implications of these results on management of rice geneticresources are discussed. Oryza sativaL.; rice; germplasm conservation; seed production environment; seed development; seed longevity     

Seed Production Environment, Time of Harvest, and the Potential Longevity of Seeds of Three Cultivars of Rice (Oryza sativa L.)

Changes in seed quality (assessed by potential longevity, i.e.the value of the seed lot constant K₁ of the seed viabilityequation) in three contrasting cultivars of rice (Oryza sativaL.) were monitored during seed development and maturation intwo temperature regimes, viz 28/20°C and 32/24°C (12/12h), provided by controlled environments. Mass maturity (definedas the end of the seed-filling phase) varied only between 18and 20 d after 50% anthesis. In five of the six treatment combinationsmaximum potential longevity was not achieved until 12-19 d aftermass maturity. In contrast, the maximum potential longevityof seeds of a japonica rice cultivar produced in the warmerregime was obtained in the first harvest after mass maturity.After mass maturity, the potential longevity of the japonicarice seed lots produced in the warmer environment was much lessthan that for the cooler environments. Maximum potential longevitywas also consistently greater in the cooler than the warmerregime for the two indica cultivars, although the differencein K₁ was small (0·3-0·5). The deleterious effectof increase in temperature on seed quality development was notdetected until after mass maturity. Maximum potential longevityin the cooler regime was greatest in the glutinous indica (K₁= 3·9) and least in the japonica cultivar (K₁ = 3·1).It is concluded that the japonica cultivar is not as well adaptedto warm seed production regimes as the indica cultivars. Consequently,subject to confirmation, this research suggest that the seedproduction of japonica cultivars for long-term genetic conservationshould be undertaken, whenever possible, in warm temperate environments.Copyright1993, 1999 Academic Press Oryza sativa L., rice, genebanks, seed development, seed storage, seed longevity, temperature     

SEXUAL SIZE DIMORPHISM AND SELECTION IN THE WILD IN THE WATERSTRIDER AQUARIUS REMIGIS: LIFETIME FECUNDITY SELECTION ON FEMALE TOTAL LENGTH AND ITS COMPONENTS

Darwin's fecundity advantage model is often cited as the cause of female biased size dimorphism, however, the empirical studies of lifetime selection on male and female body size that would be required to demonstrate this are few. As a component of a study relating sexual size dimorphism to lifetime selection in natural populations of the female size-biased waterstrider Aquarius remigis (Hemiptera: Gerridae), we estimated coefficients for daily fecundity selection, longevity selection, and lifetime fecundity selection acting on female body size and components of body size for two consecutive generations. Daily fecundity was estimated using females confined in field enclosures and reproductive survival was estimated by twice-weekly recaptures. We found that daily fecundity selection favored females with longer total length through direct selection acting on abdomen length. Longevity selection favored females with smaller total length. When daily fecundity and reproductive longevity were combined to estimate lifetime fecundity we found significant balancing selection acting on total length in both years. The relationship between daily fecundity and reproductive longevity also reveals a significant cost of reproduction in one of two years. We relate these selection estimates to previous estimates of sexual selection on male body size and consider the relationship between contemporary selection and sexual size dimorphism.     

Sex ratio and sexual dimorphism in the dioecious Borderea pyrenaica (Dioscoreaceae)

Sex ratio and sexual dimorphism of Borderea pyrenaica, a long-lived dioecious geophyte endemic to the Pyrenees (north-east Iberian Peninsula), were examined in three alpine populations. In this species, age can be estimated and the sex of nonreproductive adult plants identified. Male plants attain sexual maturity earlier, flower more frequently and grow faster than female plants, whereas females allocate a higher biomass to reproduction than males. These results support the hypothesis that female plants incur a higher cost of sexual reproduction and that this higher cost is measurable as reduced vegetative growth and lower flowering frequency. Variation of sex ratio among young, intermediate and old adults within populations suggests, however, that this higher female reproductive investment does not result in sexual differences in mortality. The overall male-biased sex ratio in B. pyrenaica is mainly a consequence of the tendency of males to reproduce at an earlier age and more frequently than females.     

Age and size at sexual maturity of the smooth skate Malacoraja senta from the western Gulf of Maine

Age and size at sexual maturity was determined for 185 male and 96 female smooth skates Malacoraja senta (ranging in size from 370 to 680 mm total length L_T), collected from the western Gulf of Maine. Maturity ogives for males, based on clasper length, testis mass and the proportion of mature spermatocysts in the testes, suggest that 50% maturity occurs between 9 and 10 years and 560 mm L_T. Maturity ogives for females, based on ovary mass, shell‐gland mass and maximum follicle size, suggest that 50% maturity occurs at age 9 years and 540 mm L_T.     

Evolutionary genetics of Drosophila ananassae: evidence for trade-offs among several fitness traits

Correlated responses to bi‐directional selection on thorax length, examined on several life‐history traits and chromosome inversion polymorphisms, have revealed apparent novel trade‐offs in Drosophila ananassae. We provide evidence of trade‐offs between hatching time and pupal period, pupal period and egg‐pupa development time, and pupal period and larval development time (LDT). Body size shows positive correlations with ovariole number, LDT and DT (egg–fly). We provide evidence of sexual dimorphism for trade‐offs between longevity and body size and starvation and longevity in females only. Trade‐offs between wing/thorax (W/T) ratio and longevity, W/T ratio and starvation, and DT (egg‐ fly) and longevity are evident in males only. Sexual dimorphism is also evident for inversion polymorphism with body size and longevity. A longevity assay suggests that low line females outlived high line females whereas high line males outlived low line males. The mean longevity in males is negatively correlated with the 2L‐ST and 3R‐ST arrangement frequencies whereas the 3L‐ST arrangement frequency is positively correlated with the mean longevity in males but opposite arrangements are found in females. Absolute starvation resistance is negatively correlated with 2L‐ST and 3R‐ST chromosome arrangements and results in a trade‐off between longevity and absolute starvation resistance in females. Analyses of fecundity, hatchability, and viabilities based on age intervals in both G₁₀ and G₁₃ suggest that the early reproduction is favoured in D. ananassae. The productivity percentage is highest in the high line and there is no effect of late reproduction on it. Overall, we provide some unravelled trade‐offs and striking sex differences, which may help in understanding the life‐history evolution of the species. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 90 , 669–685.     

Life history of the orange-striped emperor <Emphasis Type="Italic">Lethrinus obsoletus</Emphasis> from the Mariana Islands

The present study investigated the age-based demography of the orange-striped emperor, Lethrinus obsoletus, from commercial samples in the Commonwealth of the Northern Mariana Islands (CNMI), spanning a 24-month market sampling period. Information on growth, life span, mortality, and reproduction was derived through analysis of sectioned sagittal otoliths and gonad material. The species had a moderate longevity of 13 years while females and males reached 50% sexual maturity at 3.8 years (22.9 cm fork length) and 2.8 years (19.9 cm fork length), respectively. Histological examination of gonads and sex-specific age frequency distributions suggest the sexual ontogeny of the species conforms to juvenile hermaphroditism, whereby sexual transition from female to male occurred prior to maturation. No annual spawning periods were identified, but the ubiquitous presence of post-ovulatory follicles in females and spermatogenic material in males coupled with a consistent lunar trend in gonadosomatic index patterns suggests the species spawns every lunar cycle throughout the year with spawning activity potentially increasing around the new moon. Ratios of natural to fishing mortality indicate a moderate level of exploitation (0.37); however, a large portion of harvested females had not reached reproductive maturity, suggesting that formal assessments of stock status are warranted to ensure the sustainable harvest of the species in CNMI.     

Influence of temperature on growth, reproduction and longevity of Moina salina Daday, 1888 (Cladocera, Moinidae)

This paper presents the results of a study of the effects oftemperature on the growth, reproduction and longevity of thecladoceran Moina salina, a species of potential use as livefood in marine aquaculture. The growth rate of M.salina increasedwith increasing temperature. Some parameters of development,such as length at death and the number of adult instars, werealso positively related to temperature. Other parameters (durationof juvenile and adult instars) decreased with increasing temperature,while the number of juvenile instars was unaffected. An increasein temperature resulted in a reduction in age at maturity anda decrease in the number of days between broods. The numberof young per female, the number of broods per female, the numberof youngper day of reproductive life, and the number of youngper brood, increased up to a temperature of 25°C. At 15and 20°C. substantial degeneration of eggs and/or embryosoccurred. Likewise, temperature affected the type of reproductioncarried out by sexual females. Temperature and longevity wereinversely correlated. It was concluded that temperature actsas a very important factor regulating the life cycle of M.salina.Temperature >30°C may correspond to sublethal levels,while a temperature of 15°C is considered to impose stress.The range 20–25°C is optimal for the development andreproduction of this species.     

The influence of different aphid prey species on the biology and life table parameters of Propylaea japonica

The influence of three aphid prey species – Aphis craccivora Koch, Megoura viciae Buckton and Rhopalosiphum maidis (Fitch) – on the biology of Propylaea japonica (Thunberg) was studied under laboratory conditions. The development, survivorship, longevity, reproduction and life table parameters of P. japonica differed significantly among different treatments. The shortest developmental period of P. japonica (from first-instar larvae to adult) was observed on A. craccivora, whereas the longest was observed on M. viciae. The highest survivorship was observed on A. craccivora, and the lowest survivorship was observed on M. viciae. The highest sex ratio, fecundity and the shortest pre-oviposition period were observed when A. craccivora was used as prey. The longevities of P. japonica females and males did not differ significantly when reared on different aphid species. The highest values of net reproductive rate, intrinsic rate of increase and finite rate of increase were observed on A. craccivora. The results suggest that A. craccivora is a suitable prey for P. japonica among the three aphid species tested and can serve as a diet for the mass rearing of P. japonica under laboratory conditions for possible use in integrated pest management.     

Relative Growth and Sexual Maturity of the Hermit Crab Paguristes erythrops (Anomura, Diogenidae) from South Atlantic

Some morphometric relationships were studied in the hermit crab Paguristes erythrops to describe its relative growth and the size at which sexual maturity is reached, as well as the shell influence on this process. Individuals were collected monthly from January to December/1999, by SCUBA diving and 12 different characters were measured on males and females. Sexual size dimorphism was observed in length and width of left cheliped. Size at sexual maturity was estimated between 2.8 and 3.5 mm shield length based on the left cheliped relations of the males and on the endopod and exopod of the second pleopod of the females. Differences in the allometry of individuals occupying different shell species were observed. The present work demonstrated the importance of characterizing the type of growth of some parts (pleopods) not yet used in other studies on relative growth of hermit crabs that may correspond to indicators of the size at sexual maturity.     

A Review of Size at Maturity in Male Tanner (Chionoecetes bairdi) and King (Paralithodes camtschaticus) Crabs and the Methods Used to Determine Maturity

This paper reviews existing studies on the size of sexual maturityfor male Tanner or snow crab (Chionoecetes bairdi), a brachyuran,and the anomuran red king crab (Paralithodes camtschaticus).In this report the term sexual maturity is denned as the abilityto reproduce. A variety of indirect and direct methods thathave been used to determine maturity are reviewed. Examiningthe vas deferens for the presence of spermatophores was usefulin determining the size at which males first become mature.Breeding experiments in the laboratory demonstrated that mostmales, from both species, that produced spermatophores couldbreed with soft-shelled mates. Males of both species can breedat smaller sizes than do females. Morphometric techniques basedon reproductive tract weights and chela morphometry overestimatedthe sizes at which males mature in both species. Previous experimentsfor Tanner crab, which have internal fertilization, suggestsmall mature males can fertilize two to five females. Breedingexperiments showed recently matured red king crab do not appearto be able to fertilize more than one female per breeding season,while males nearing harvestable size can fertilize more thanone female. Breeding experiments and in situ observations of grasping pairsappear to be the most feasible methods for identifying malesize at maturity for these species. The value of morphometricestimations for determining when males mature is questionable.     

Maternal Investment in the Swordtail Fish Xiphophorus multilineatus: Support for the Differential Allocation Hypothesis

The differential allocation hypothesis predicts that reproductive investment will be influenced by mate attractiveness, given a cost to reproduction and a tradeoff between current and future reproduction. We tested the differential allocation hypothesis in the swordtail fish Xiphophorus multilineatus, where males have genetically influenced (patroclinous inheritance) alternative mating tactics (ARTs) maintained by a tradeoff between being more attractive to females (mature later as larger courting males) and a higher probability of reaching sexual maturity (mature earlier as smaller sneaker males). Males in X. multilineatus do not provide parental care or other resources to the offspring. Allelic variation and copy number of the Mc4R gene on the Y-chromosome influences the size differences between males, however there is no variation in this gene on the X-chromosome. Therefore, to determine if mothers invested more in offspring of the larger courter males, we examined age to sexual maturity for daughters. We confirmed a tradeoff between number of offspring and female offspring’s age to sexual maturity, corroborating that there is a cost to reproduction. In addition, the ART of their fathers significantly influenced the age at which daughters reached sexual maturity, suggesting increased maternal investment to daughters of courter males. The differential allocation we detected was influenced by how long the wild-caught mother had been in the laboratory, as there was a brood order by father genotype (ART) interaction. These results suggest that females can adjust their reproductive investment strategy, and that differential allocation is context specific. We hypothesize that one of two aspects of laboratory conditions produced this shift: increased female condition due to higher quality diet, and/or assessment of future mating opportunities due to isolation from males.     

Longevity costs of same‐sex interactions: first evidence from a parasitic wasp

Costs of sexual interactions play a key role in life‐history evolution. Although the costs of reproduction have been investigated in both sexes of many insects, the costs of same‐sex interactions have been examined in few species. In parasitic wasps, very little has been reported about the longevity costs of heterosexual interactions, and nothing is known about longevity costs of same‐sex interactions. In this study, the effects of heterosexual and homosexual activities on longevity were evaluated in Psyttalia concolor (Hymenoptera: Braconidae), a synovigenic koinobiont larval‐pupal endoparasitoid of tephritid flies. When compared with individually housed virgin wasps, male longevity was strongly reduced both in males kept with females, and in males kept with other males. When females were kept with males, their longevity was reduced compared with the virgin females and females kept with other females. Overall, the costs of male–female interactions were considerable in both sexes of P. concolor, while same‐sex activities were found to be costly only among males, suggesting that they may have implications for the evolution of the P. concolor mating system.