Age structure and body size of the Chuanxi Tree Frog Hyla annectans chuanxiensis from two different elevations in Sichuan (China)

Age, body size, and growth patterns in the subtropical anuran Hyla annectans chuanxiensis from high (Dengchigou Protection Station) and low (Lingguan Town) elevations in Baoxing County of Sichuan province (China) were described using skeletochronology. Females were significantly older than males at the low-elevation site, but there was no significant difference between the sexes at the high-elevation site. Age at sexual maturity of both males and females was 2 years at the high-elevation site, whereas males matured at 1 year and females at 2 years at the low-elevation site. Males and females from the low-elevation population reached a maximum age of 3 and 4 years, respectively, whereas males and females from the high-elevation population reached a maximum age of 4 and 5 years, respectively. At both sites, females were significantly larger than males. Females and males from the high-elevation population were larger than individuals from the low-elevation population. When the effect of age was controlled, the differences in body size of the two populations were significant only for females. Von Bertalanffy growth curves indicated that the growth rates in males was greater than in females in both populations. They also showed that the growth of both sexes slowed at an earlier age in the low-elevation population than in the high-elevation population. The findings suggest that age is a major factor underlying body size patterns for both sexes, but that the elevation of the locality affects the body size of females.     

Age, growth and reproduction of the cyprinid Rutilus lemmingii (Steindachner, 1866) in the River Huebra, Central Spain

Age, growth and reproduction of the R. lemmingii population of the River Huebra, Duero basin are analysed. Females dominated older age classes and lived up to 6 years (5+) while males only reached 5 years (4+). The growing season extended from April to September; growth rates were similar for both sexes. 0+ fish condition increased during their first summer and spring. In older fish, condition cycle was related to gonad development and showed some differences between sexes. The number of females reaching maturity at age 1 + almost doubled that of males; females also matured at smaller size. Both fecundity and egg size increased with female length: mean egg counts varied between 974 for 1 + individuals and an estimated 10491 for 5+ fish. Eggs were produced as a single batch, but were released fractionally during April and May.     

Body size, age and reproduction in the leopard toad, Bufo pardalis

Data on the relationships between body size and age were obtained for a sample of leopard toads Bufo pardalis from a breeding population of this species from the Cape Peninsula, South Africa. Age was determined by counting the number of lines of arrested growth in histological sections of a digit clipped from each individual. In males there was a positive, but weak, correlation (explaining only 18% of the variance) between body size and age, and in females no correlation at all existed between these two variables. Males which were successful in obtaining matings were not older than unsuccessful males. Age of males at the breeding site ranged from one to three years, whereas females ranged from two to six years old. This represents both the earliest age of reproduction, as well as the greatest difference in longevity between the sexes, documented for an anuran species.     

Life-history traits of two Mediterranean lizard populations: a possible example of countergradient covariation

The trade-off between clutch and offspring size, which is a central topic in life-history research, is shaped by natural selection to maximize the number of surviving offspring, but it also depends on the resources available for reproduction. Conspecific populations living in different environments may differ in adult body size, clutch mass, clutch size, offspring size, and/or post-natal growth rates, due either to phenotypic plasticity or to local adaptation. Here, we compare these traits and their relationships between two populations of the lizard Psammodromus algirus separated by a 600-m altitudinal gradient. We used a common garden design to control incubation temperature and food availability, with two different feeding treatments. Females were larger at the high-elevation site. Although SVL-adjusted clutch mass did not differ between populations, high-elevation females laid more but smaller eggs than low-elevation ones. Hatchlings were larger at lower elevation. Our common garden experiment revealed that low-elevation hatchlings grew faster than high-elevation hatchlings under both feeding treatments. However, higher food availability at higher altitude allows high-elevation lizards to grow faster and attain larger adult sizes, especially in the case of females. The two key adaptations of low-elevation lizards, large eggs and hatchlings and the ability to grow rapidly after hatching, are likely to enhance survival in low-productivity Mediterranean lowlands. Our data support the hypothesis that the reproductive strategies of these populations provide an example of countergradient variation, because the genotypes that encode for fast growth and large body size occurred in low food availability habitats where juveniles grew slowly and attained small adult sizes.     

Growth and body size in populations of mink frogs Rana septentrionalis from two latitudes

Age, longevity, and growth in mink frogs Rana septentrionalis from two latitudes in Quebec, Canada, were assessed by skeletochronological and back-calculation methods in order to document proximate causes for intraspecific variations in adult body size. In both study sites, females grew faster and were on average 11% larger than males. Mean age and maximal longevity were significantly higher in females than in males only in the southern populations. There was thus an interpopulation difference in the relative contribution of age and growth to sexual size dimorphisms. Sex-ratio also favored females (males sulfering higher mortality) only in the southern populations. Specimens from the northern population had higher mean ages (but not higher longevities) and were 17% larger than specimens from the southern populations. Annual growth rate appeared similar at the two study sites despite a shorter growing season at the northern locality. Maturity was reached by both sexes after 1 yr of post-metamorphic life (PML) in the southern populations but after 2 yr of PML in the northern population. There are indications that tadpoles metamorphose at larger body size at the northern locality after a prolonged larval period. It is concluded that growth rate, delayed maturity, greater mean ages, and eventually size at transformation, all contribute to the larger size of adult mink frogs at northern localities.     

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.     

Sex differences in age structure, growth rate and body size of common frogs Rana temporaria in the subarctic

The thermal environment and length of the activity season are important factors in shaping life-history trait variation in ectotherms. Many ectothermic vertebrates living at high latitudes or altitudes tend to be larger and older than their conspecifics living at lower latitudes or altitudes. However, detailed data on age, body size and growth variation—and how they may differ between males and females—are still scarce, especially from extreme high-latitude environments. We studied growth (body length increment), age and size structure of common frogs (Rana temporaria) in subarctic Finland (69°04′N) by applying skeletochronological methods to individually marked adults (n?=?169) captured and recaptured between 1999 and 2003. We found that breeding males were on average younger (mean?=?8.5?years) than females (11.9?years) and that males started reproducing earlier (≥3–4?years of age) than females (>4–5?years). The oldest encountered individual was an 18-year-old female, which to our knowledge is the oldest wild common frog ever reported. Females were on average larger (mean body length?=?76.6?mm) than males (70.7?mm), and this appeared to be mainly due to their older age as compared to males. While body length increased and growth rate decreased with age in both sexes, growth rate declined significantly faster with age in males than in females. The latter finding provides a proximate explanation for the observation that even after accounting for age differences among sexes (females?>?males), females were longer than males.     

Asymmetric size effect of sexes on reproductive fitness in an aphid parasitoid Aphidius ervi (Hymenoptera: Aphidiidae)

Most studies on size–fitness relationships focus on females and neglect males. Here, we investigated how body size of both sexes of an aphid parasitoid, Aphidius ervi Haliday, affected the reproductive fitness. Reproductive fitness was generally positively correlated with body size for both sexes in this species. Large individuals of both sexes had greater longevity, large males fathered more progeny, and large females had higher fecundity, parasitism, and greater ability in host searching and handling. We demonstrated in this study that size effects of males and females were asymmetric on different reproductive fitness parameters. With increasing body size females gained more than males in longevity and fecundity while males gained more than females in the number of female progeny. Regardless of female size, large males sustained a female-biased population longer than small males. These results suggest that male body size should also be considered in the quality control of mass-rearing programs and the evaluation of parasitoid population growth.     

Elevational variation in adult body size and growth rate but not in metabolic rate in the tree weta Hemideina crassidens

Populations of the same species inhabiting distinct localities experience different ecological and climatic pressures that might result in differentiation in traits, particularly those related to temperature. We compared metabolic rate (and its thermal sensitivity), growth rate, and body size among nine high- and low-elevation populations of the Wellington tree weta, Hemideina crassidens, distributed from 9 to 1171 m a.s.l across New Zealand. Our results did not indicate elevational compensation in metabolic rates (metabolic cold adaptation). Cold acclimation decreased metabolic rate compared to warm-acclimated individuals from both high- and low-elevation populations. However, we did find countergradient variation in growth rates, with individuals from high-elevation populations growing faster and to a larger final size than individuals from low-elevation populations. Females grew faster to a larger size than males, although as adults their metabolic rates did not differ significantly. The combined physiological and morphological data suggest that high-elevation individuals grow quickly and achieve larger size while maintaining metabolic rates at levels not significantly different from low-elevation individuals. Thus, morphological differentiation among tree weta populations, in concert with genetic variation, might provide the material required for adaptation to changing conditions.     

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.     

The evolution of sexual size dimorphism in the house finch. IV. Population divergence in ontogeny

Differences among taxa in sexual size dimorphism of adults can be produced by changes in distinct developmental processes and thus may reflect different evolutionary histories. Here we examine whether divergence in sexual dimorphism of adults between recently established Montana and Alabama populations of the house finch (Carpodacus mexicanus) can be attributed to population differences in growth of males and females. In both populations, males and females were similar at hatching, but as a result of sex-specific growth attained sexual size dimorphism by the time of independence. Timing and extent of growth varied between the sexes: Females maintained maximum rates of growth for a longer time than males, whereas males had higher initial growth rates and achieved maximum growth earlier and at smaller sizes than females. Ontogeny of sexual dimorphism differed between populations, but in each population, sexual dimorphism in growth parameters and sexual dimorphism at the time of nest leaving were similar to sexual dimorphism of adults. Variation in growth of females contributed more to population divergence than did growth of males. In each population, we found close correspondence between patterns of sexual dimorphism in growth and population divergence in morphology of adults: Traits that were the most sexually dimorphic in growth in each population contributed the most to population divergence in both sexes. We suggest that sex-specific expression of phenotypic and genetic variation throughout the ontogeny of house finches can result in different responses to selection between males and females of the same age, and thus produce fast population divergence in the sexual size dimorphism.     

Age and growth of the ajime-loach,niwaella delicata, in the yura river, kyoto, japan

The age of the Ajime-loach,Niwaella delicata (a species endemic to Japan), was determined from the number of concentric rings appearing on the cross-sectional surface of the erectile spine (peculiar to Cobitidae). The ages of loaches caught in the Yura River, Kyoto, were determined and growth rates for each sex estimated. It was found that size dimorphism in this species was due to different growth patterns between the sexes, 2.5 years old males being larger than females and usually sexually mature, unlike the latter. Females older than 3.5 years were sexually mature and larger than males of equivalent age.     

A skeletochronological study of age, growth and longevity in a population of the frog Rana ridibunda from southern Europe

Age at sexual maturity and longevity in a population of Rana ridibunda from north-eastern Greece were studied by skeletochronology performed on the phalanges. Analysis of the age structure was based on counting the lines of arrested growth (LAGs). Sexual maturity for both sexes arises during the first year or after the first hibernation. Ages ranged from 1 to 5 years (mean=2.96) among 52 males and from 1 to 5 years (mean=3.73) among 56 females. The mean snout-vent length was 69.03+/-12.6mm in males and 82.38+/-13.27 mm in females. The difference between the sexes in age and size was significant. Growth of individuals was fitted on? The von Bertalanffy model. The growth coefficient (K) was 0.57 in males and 0.54 in females, mainly due to faster male growth between metamorphosis and maturation.     

Sexual size dimorphism, growth and maturity of the Japanese fluvial sculpin,Cottus pollux (large egg type), in the Inabe River, Mie prefecture, central Japan

The population structure of the Japanese fluvial sculpin,Cottus pollux (large egg type), in the upper reaches of the Inabe River, Mie Prefecture, central Japan, was investigated by a mark-and-recapture method from July 1989 to January 1991. Breeding of the species occurred from mid February to early May, peaking from mid February to late March. The mean size of mature males observed in March 1990 was significantly larger than that of females, showing apparent sexual size dimorphism. Data analysis of the growth of 1658 marked individuals revealed that the species matured at 2 years of age in both sexes. Whereas 1 year old males reached ca. 50–70 mm SL, females were less than 50 mm SL at the same age, size dimorphism already being apparent. Immature males exhibited higher growth rates than females during their first and second years, some of the former outstripping mature males of the preceding year class in total length. After attaining sexual maturity, both males and females grew mainly from July to December, with no significant differences in mean growth rate between them. Sexual size dimorphism of the species seems to be attributable to different growth rates between the sexes during their immature stage.     

Sexual Selection of Zorion guttigerum Westwood (Coleoptera: Cerambycidae: Cerambycinae) in Relation to Body Size and Color

Zorion guttigerum is a flower-visiting longhorned beetle endemic to New Zealand. Sexual selection of this species in relation to the body size and color form of different sexes was investigated in the field. The population sex ratio, based on censuses of feeding and mating sites (flowers), is male-biased. Females are significantly larger than males. Both sexes have antennae of similar length but the antennal length relative to the elytral length is greater in males than in females, and the antennal length of males increases more with an increase in body size than that of females. Both sexes have dark blue (DB) and yellowish-brown (YB) individuals. Both pair-bonded and solitary males are similar in elytral and antennal length. In pair-bonded males, DB individuals are significantly more numerous than YB ones, but in solitary males, the number of both color forms is similar. Males tend to have territory protection behavior, fighting with and chasing away rival males from feeding and mating sites. Larger males usually win the fight but the size-dependent fighting advantage does not translate into mating success. Male color plays an important role in mating success, with DB males having a significantly better chance to mate than YB males. Furthermore, male body size and color also have interactions in mating success: males of DB color morph obtain a greater mating advantage according to body size. Pair-bonded females are significantly larger and have longer antennae than solitary females, suggesting that males prefer larger females for mating. In addition, females of DB color morph with longer antennae are also preferred by males for mating. The significance of these findings is discussed.     

Territorial behavior of both sexes in the water striderMetrocoris histrio (Hemiptera: Gerridae) during the mating season

Territorial behavior of overwintered individuals of Metrocoris histriowas observed in an upstream area. Adults of both sexes held territories, but male territories were larger than those of females. Severe competition occurred among males for territories which give them access to receptive females. The effects of male body length and midleg length on establishment of territories were not significant. The effect of female midleg length on activity of females entering preferred foraging sites was equally not significant. Instead, territorial behavior increased with male age and males stayed longer at prime sites. Females of intermediate age were likely to occupy prime sites. Females had longer territory residence time than males. The sexes were dimorphic with respect to midleg length, and dimorphism in M. histriomay be related to a difference in life history, in that sexual selection may be relaxed due to asynchronous adult emergence patterns.     

Development of epiphyseal union in Japanese macaques of known chronological age

Forty epiphyseal unions were studied in the two subspecies of the Japanese macaque at known chronological ages. The age standards of the beginning and completion of epiphyseal union were estimated. The total score of the ratings of the unions revealed significant correlations with chronological age before 9 years of age. The linear regressions were calculated in each group of different sex and different subspecies in order to enable predictions to be made of the chronological age from the total score. Although males and females generally showed the same pattern of sequences, the unions of the females united earlier than those of the males in both subspecies before 9 years of age. The Yaku subspecies demonstrated an earlier union than the common Japanese macaque in both sexes before the age of 9 years old. The epiphyseal union of the Japanese macaque usually developed earlier than the reported union in the rhesus macaque. A large number of epiphyseal unions united at least partially and the total score deviated widely during the range from around 4 to 6 years of age. This period was in accordance with the adolescent growth period, especially in males, with rapid growth of body size as observed based on by somatometrical measurements. The skeletal growth of the trunk was generally late compared with that of the limbs. During the range after 8 years of age, some unions of the trunk united earlier in males than in females. The epiphyseal union could allow a more precise age estimation than the body mass or dental eruption during a certain range of ages. However, developmental estimations obtained from animals fed artificially, as the present samples were, must be applied with caution to wild animals.     

Life history of Eulemur fulvus rufus from 1988-1998 in southeastern Madagascar

In this study, we compare the life-history patterns of male and female Eulemur fulvus rufus based on longitudinal data collected on individuals from two study groups from 1988-1998 in southeastern Madagascar. Mean group size was 9.5 individuals, and groups either contained more adult males than females or equal numbers of both sexes. Females reproduced for the first time between 2 and 4 years of age and reproduced each year, although the mean interbirth interval between surviving offspring was 2.1 years. An average of two adult females reproduced annually in each social group, and age and body weight may positively influence reproductive success. Females also appear to be philopatric but not female-bonded. Young natal males immigrated between 3 and 4.5 years of age and may join a new group within 612 months based on the age of emigrants. Once in a social group, they remained until old age, although a male's spatial position in the social group varied with age. Young nonnatal males were members of the social core and had the first opportunity to mate with all estrous females. Older males were peripheral to the social group and mated with females later in their cycle. We hypothesize that group size, the number of females in the group, and individual variation in reproductive success is influenced by several ecological conditions at this site: extreme variability in food availability during reproductive periods, the lack of large food patches, low plant species diversity, and small numbers of important aseasonal food sources such as Ficus species.     

Life‐history traits of the leatherjacket Meuschenia scaber,a long‐lived monacanthid

The present study describes the age and growth of the leatherjacket Meuschenia scaber, a common Australasian monacanthid and valued by‐catch of the inshore bottom trawl fishery in New Zealand. Age was determined from the sagittal otoliths of 651 individuals collected between July 2014 and March 2016 in the Hauraki Gulf of New Zealand. Otolith sections revealed alternating opaque and translucent zones and edge‐type analysis demonstrated that these are deposited annually. Meuschenia scaber displayed rapid initial growth, with both males and females reaching maturity in 1–2 years and 50% of both sexes matured at 1·5 years. Maximum age differed substantially between the sexes, at 9·8 years for males and 17·1 years for females. Growth rate was similar between sexes, although males reached greater mass at age than females in the early part of the lifespan. The length–mass relationship differed significantly between the sexes, with males displaying negative allometric growth and females isometric growth. Female condition was highest in July, declined in August with the onset of spawning and showed a slight peak in January and February, immediately following the spawning season. This study substantially extends the maximum longevity recorded for monacanthids, although males had much shorter lifespans and higher mortality, than females.     

Age Structure of Two Species of Odorous Frogs(Odorrana margaretae and Odorrana grahami)

Variation in age structure and body size benefits are identified to understand the evolution of life history. Here, we estimated the age structure and body size of two species of odorous frogs(Odorrana margaretae and Odorrana grahami) by using skeletochronology. The ages at sexual maturity of O. grahami and O. margaretae in both sexes were 1 and 2 years, respectively. For both sexes, the maximum age observed in O. margaretae was six years. For O. grahami, the maximum age observed in males and females were 4 and 5 years, respectively. Males and females did not differ in mean age in the two species.The average body size of both species considerably differed between sexes, with females being larger than males. The body size of females was also larger than that of males when the effect of age was removed. We also found positive correlations between body size and age within each sex in O. margaretae, but only for female in O. grahami. The female-biased sexual size dimorphism of the two species suggested that fecundity selection for larger female size may increase the reproductive output.