Appendicular skeletal morphology in minute salamanders,genus Thorius (amphibia: Plethodontidae): Growth regulation,adult size determination,and natural variation

Patterns of growth and variation of the appendicular skeleton were examined in Thorius, a speciose genus of minute terrestrial plethodontid salamanders from southern Mexico. Observations were based primarily on ontogenetic series of each of five species that collectively span the range of adult body size in the genus; samples of adults of each of seven additional species provided supplemental estimates of the full range of variation of limb skeletal morphology. Limbs are generally reduced, i.e., pedomorphic, in both overall size and development, and they are characterized by a pattern of extreme variation in the composition of the limb skeleton, especially mesopodial elements, both within and between species. Fifteen different combinations of fused carpal or tarsal elements are variably present in the genus, producing at least 18 different overall carpal or tarsal arrangements, many of which occur in no other plethodontid genus. As many as four carpal or tarsal arrangements were observed in single population samples of each of several; five tarsal arrangements were observed in one population of T. minutissimus. Left-right asymmetry of mesopodial arrangement in a given specimen is also common. In contrast, several unique, nonpedomorphic features of the limb skeleton, including ossification of the typically cartilaginous adult mesopodial elements and ontogenetic increase in the degree of ossification of long bones, are characteristic of all species and distinguish Thorius from most related genera. They form part of a mechanism of determinate skeletal growth that restricts skeletal growth after sexual maturity. Interspecific differences in the timing of the processes of appendicular skeletal maturation relative to body size are well correlated with interspecific differences in mean adult size and size at sexual maturity, suggesting that shifts in the timing of skeletal maturation provide a mechanism of achieving adult size differentiation among species. Processes of skeletal maturation that confer determinate skeletal growth in Thorius are analogous to those typical of most amniotes – both groups exhibit ontogenetic reduction and eventual disappearance of the complex of stratified layers of proliferating and maturing cartilage in long bone epiphyses – but, unlike most amniotes, Thorius lacks secondary ossification centers. Thus, the presence of secondary ossification centers cannot be used as a criterion for establishing determinate skeletal growth in all vertebrates.     

Phenotypic plasticity in age and size at maturity and its effects on the integrated phenotypic expressions of life history traits of Cardamine flexuosa (Cruciferae)

We analyzed variation in phenotypic plasticity of life history traits between two Cardamine flexuosa populations based on differences in plasticity of age and size at maturity. C. flexuosa (Cruciferae) is a facultative, vernalization-sensitive, long-day annual, and its phenology and the phenotypic expressions of many life history traits are largely controlled by photoperiod and vernalization in natural populations. We used plants from two populations which differed in their responses to chilling and photoperiod treatments. The timing of developmental processes was changed by controlling temperature and photoperiod regimes in growth chambers. Plasticity in size at maturity was analyzed as changes in a growth trajectory using two parameters, age at maturity (Δt) and growth rate (k). Both traits showed plasticity, but differences between the populations were found mostly for Δt. Distinctive differences in size at maturity of individuals in the two populations were mainly due to different amounts of plasticity in Δt. Variations in plasticity of nine other life history traits and their associations to age and size at maturity were also analyzed. Variation for eight of the traits can be described, at least in part, as a function of age and size at maturity for both populations, and most of the variation in the total number of seeds was explained by age and size at maturity. Only age at maturity had any effect on changes in resource allocation. The nine life history traits were integrated through associated character expressions with age and size at maturity. Changes in the association between a trait and age and/or size at maturity were rather conservative compared to changes in the plasticity of a trait between the two populations. Associations with age and size at maturity are mostly explicable in terms of inherent relationships in the developmental processes, and they may limit the ecological range expansion and the adaptive evolution of plasticity in C. flexuosa. The negative correlation between reproductive allocation and age at maturity can be a cost of delaying maturation in C. flexuosa.     

The Relationship of Rapid Weight Gain in Infancy to Obesity and Skeletal Maturity in Childhood

Objective: Children with birth weight appropriate for gestational age (AGA) who also demonstrate rapid weight gain in infancy have a greater risk of being overweight or obese during childhood. A concurrent advancement in skeletal maturity would account for their greater size and would, therefore, not necessarily pose a threat of greater risk during adolescence and early adulthood. This study aims to determine whether children with rapid weight gain during infancy have advanced skeletal maturity during childhood. Research Methods and Procedures: One hundred and ninety‐three African children (boys = 108; girls = 85) of normal birth weight and gestational age were assessed from birth to 9 years. Body composition was assessed at 9 years of age by whole‐body DXA, and skeletal maturity was assessed using the Tanner‐Whitehouse II technique. Rapid weight gain in infancy was defined as a +0.67 change in weight‐for‐age Z‐score between birth and 2 years. Results: Rapid weight gain was experienced by over 20% of the sample. Children with rapid weight gain were significantly lighter at birth and significantly taller, heavier, and fatter throughout childhood. Chronological age and Tanner‐Whitehouse II technique skeletal ages at 9 years were not significantly different between groups or between sexes within groups. Discussion: Because AGA children with rapid weight gain have a greater risk of overweight and obesity but are not advanced in skeletal maturity, later adolescent adjustments toward average weight and fatness values are unlikely. The identification and monitoring of such children is of importance in reducing their risk of morbidity.     

Associations between the rates of maturation and growth in the short bones of the hand

Serial radiographs of the hand-wrist were used to analyze the associations within bones between the rates of change in skeletal maturity, diaphyseal and epiphyseal lengths and diaphyseal width. In previous studies of these children, it has been shown that these rates are linear in relation to chronological age. The associations between the rates of change in these parameters were analyzed using the slopes (b values) for regression lines flitted to the data in each child. In individual bones, most of the correlation coefficients were moderate to low; some were negative. For most associations in each sex they were relatively high for metacarpal II. The rates of skeletal maturation and diaphyseal elongation were correlated more highly in the girls than in the boys but the rates of skeletal maturation and epiphyseal elongation were correlated more highly in the boys. When bones were considered in groups, relatively high correlations were noted for the metacarpals and ray II, lower correlations were common for the middle and distal phalanges. There was no evidence of real neighborhood effects but marginal effects were present.     

Life history and initial assessment of fishing impacts on the by‐catch species Dules auriga (Teleostei: Serranidae) in southern Brazil

The life history of Dules auriga, a small hermaphrodite serranid species inhabiting deep waters and a frequent component of the discarded catch of bottom trawling in southern Brazil, was studied to assess the fishery effects on the stock through the estimation of the remaining spawning‐potential ratio. Sampling was conducted throughout a year and included specimens to determine sex, maturity and age. Age was validated by the edge type and marginal‐increment analysis. The oldest and the largest individuals were 9 years and 195 mm total length. Growth parameters fitted to the von Bertalanffy equation were L_∞ = 178·34 mm, k = 0·641 year^?1 and t₀ = ?0·341 years. Length and age at first maturity were 140·72 mm and 2 years, respectively. The reproductive season was throughout the austral spring and summer. The assessment of the effects of fishing showed that it may have resulted in a loss of 50% of the spawning potential. This loss may be higher when taking into account the uncertainty in the life‐history parameters and could be considered of concern for the population. Fast growth, moderate longevity, long spawning season, small size and age at maturity make D. auriga relatively resilient to the removal of biomass by fishing. When considering the uncertainty, however, the losses of the spawning potential have been severely reducing the population resilience in the face of ecosystem changes.     

Age, growth, and sexual maturity of the yellownose skate Dipturus chilensis in the south‐eastern Pacific

The age and growth parameters of Dipturus chilensis were estimated by counting growth rings from thin sections of vertebral centra from 400 fish (246 females and 154 males), ranging from 23 to 124 cm total length (L_T), and backcalculating fish lengths at previous ages. Marginal increment analysis lent support to the hypothesis of annual deposition of band‐pairs, which formed during the winter months. The oldest female D. chilensis aged in this study was 21 years and 117 cm L_T, whereas the oldest male was 18 years and 93 cm L_T. A 4·7% index of average per cent error (I_APE) suggested that this is a precise method for calculating the age of D. chilensis. Observed L_T were lower than backcalculated L_T, which implies the influence of Lee's phenomenon. The von Bertalanffy growth equations, based on mean length‐at‐age data, were estimated as L_t = 128·3 (1 ? e^{?0·112 (t + 0·514)}) for females and L_t = 107·8 (1 ? e^{?0·134 (t + 0·862)}) for males where t is age (years). Growth was significantly different between sexes: females reached a larger adult size. Ages and lengths at 50% maturity were estimated at 14 years of age and 106 cm L_T for females and 11 years of age and 86 cm L_T for males. At c. 14 years, there was a decline in growth rates in females. The factor most likely responsible for this was sexual maturity, which caused a discontinuity in growth of female fish. These results show that this species is slow‐growing, long‐lived, relatively large and of delayed maturity, characteristics that make it vulnerable to exploitation.     

Accuracy of dental age estimation charts: Schour and Massler,Ubelaker and the London Atlas

Dental age estimation charts are frequently used to assess maturity and estimate age. The aim of this study was to assess the accuracy of estimating age of three dental development charts (Schour and Massler, Ubelaker, and the London Atlas). The test sample was skeletal remains and dental radiographs of known‐age individuals (N = 1,506, prenatal to 23.94 years). Dental age was estimated using charts of Schour and Massler, Ubelaker, and The London Atlas. Dental and chronological ages were compared using a paired t‐test for the three methods. The absolute mean difference between dental and chronological age was calculated. Results show that all three methods under‐estimated age but the London Atlas performed better than Schour and Massler and Ubelaker in all measures. The mean difference for Schour and Massler and Ubelaker was ?0.76 and ?0.80 years (SD 1.27 year, N = 1,227) respectively and for the London Atlas was ?0.10 year (SD 0.97 year, N = 1,429). Further analysis by age category showed similar accuracy for all three methods for individuals younger than 1 year. For ages 1–18, the mean difference between dental and chronological ages was significant (P < 0.05) for Schour and Massler and Ubelaker and not significant (P > 0.05) for the London Atlas for most age categories. These findings show that the London Atlas performs better than Schour and Massler and Ubelaker and represents a substantial improvement in accuracy of dental age estimation from developing teeth. Am J Phys Anthropol 154:70–78, 2014. © 2014 Wiley Periodicals, Inc.     

Life-history traits of the lizard Sceloporus undulatus from two populations raised in a common laboratory environment

Hatchling Sceloporus undulatus elongatus from Washington Co., Utah and S. u. garmani from Woods Co., Oklahoma were raised to maturity and reproduction under identical laboratory conditions with ad libitum food availability. Growth, allometry, age and size of maturity, clutch size and egg mass were compared among lab-raised cohorts from the two populations, among lab-raised and field-caught animals (including their field-caught mothers) and, for growth, with values obtained by previously published field studies on the same or nearby populations. For all traits population differences observed in previous field studies and current field samples resulted from both a plastic response to proximate environmental conditions and intrinsic (possibly genetic) difference. The most plastic traits were growth and age of maturity. Cohorts from both populations expressed the ability to mature in less than 6 months in the laboratory but only the S.u. garmani express early maturity in the field. Allometric differences generated during growth in the lab were not observed in field samples but may reflect an adaptive physiological difference. The least plastic trait was egg mass. The only trait for which the rank order of the difference in the field was reversed in the lab was growth rate. S.u. elongatus grew significantly faster than S.u. garmani in the lab but much slower in the field. The tendency of S.u. garmani females to breed at minimum size of maturity may be greater than that of S.u. elongatus.     

Age estimation,growth and maturity of the Argentine hake (Merluccius hubbsi Marini, 1933) along the northernmost limit of its distribution in the south-western Atlantic

Age, growth and length-at-maturity of the Argentine hake (Merluccius hubbsi) were studied in the northernmost limit of the species distribution in the south-western Atlantic. A total of 351 otoliths and information from 1610 specimens sampled from the industrial double-rig trawl landings between May 2013 and April 2014 were used. Age and growth were estimated by counting and measuring increments in sectioned sagittae otoliths, and length at maturity was estimated based on macroscopic gonadal analysis. For both sexes, hepatosomatic index and condition index increased mainly during spring, reaching a maximum at the end of summer before the subsequent spawning season began. Gonadosomatic index was highest in April, believed to correspond with peak spawning. The annual periodicity of alternate opaque and translucent zones was validated by marginal increment analysis. Growth curves were fitted to back-calculated size at age by fitting the three-parameters von Bertalanffy growth function. The maximum age was 5 years in fish of either sex. Females attained larger sizes than males. The parameters of the von Bertalanffy growth equations were: L∞?=?533?mm, k?=?0.231 year^?1 and t₀?=??0.935 year for females; L∞?=?394?mm, k?=?0.405 year^?1 and t₀?=??0.463 year for males. The mean length and age at first maturity was 273?mm at 1.9 years for males and 274?mm at 2.0 years for females.     

Growth and mortality of bigeye tuna <Emphasis Type="Italic">Thunnus obesus</Emphasis> (Scombridae) in the eastern and central tropical Pacific Ocean

Biological parameters such as age, growth and age (or size) at maturity are vital for stock assessment and management. Aging is essential in yielding such information. However, limited aging studies have been conducted for large tropical pelagic species in the eastern and central tropical Pacific Ocean. The objective of this study is to conduct a length frequency analysis for estimating growth and mortality of bigeye tuna in the eastern and central tropical Pacific Ocean using samples from the Chinese longline fishery during February to November 2006. The von Bertalanffy growth parameters of asymptotic fork length L _∞ and growth coefficient k were estimated at L _∞ = 207.4 cm fork length, k = 0.23 year^-1, and theoretical age at zero length t ₀ = −0.40 year. The total mortality rate (Z) was estimated to be 0.60; the fishing mortality rate (F) and the natural mortality rate (M) were 0.25 year^-1 and 0.35 year^-1, respectively. The exploitation rate (E) was 0.16. This study provides the estimates of growth and mortality rate for bigeye tuna in the eastern and central tropical Pacific Ocean, which can be used as biological input parameters in further stock evaluations in this region. However, age analysis, further validation of the age composition and stock structure are needed for future studies.     

Age,growth and sexual development of solenette,Buglossidium luteum (Risso, 1810), in the central Aegean Sea

Age, growth, spawning period and maturity of the solenette (Buglossidium luteum Risso, 1810) were studied in the central Aegean Sea to provide fisheries managers with essential data for science‐based management. A total of 1220 samples were collected by trawl hauls from July 2004 to June 2007 in ?zmir Bay (Turkey). Sample sizes ranging from 5.3 to 11.6 cm total length were composed of 46% females, 32% males and 22% immature individuals, with a female to male ratio of 1 : 0.7. Age composition stages of the females were from I to IV, and males between I and III. The length–weight relationship was calculated as W = 0.0101L^3.008 for all samples. Estimated von Bertalanffy growth parameters were L = 13.30 cm, t_o = ?0.440 year and k = 0.481 year^?1, with a growth performance index of 1.93 (?’). The spawning period began in April and continued until July. Lengths at first maturity of females and males were 8.1 and 7.9 cm total length, respectively. Both sexes matured at the age of 2 years.     

Age and growth of the tiger shark Galeocerdo cuvier off the east coast of Australia

Total lengths (L_T) at age and growth rates for south‐west Pacific Galeocerdo cuvier were estimated from vertebral growth‐band counts of 202 sagitally sectioned centra from 112 females (71–430 cm L_T), 79 males (72–351 cm L_T) and 11 of unknown sex. Captive growth data were also examined to complement vertebral age estimations. The sexes combined modelled growth coefficient (k = 0·08) was smaller than previously reported for G. cuvier populations elsewhere. Split‐band and narrow banding patterns were identified as potential sources of age underestimation in this species.     

Bone surface texture as an ontogenetic indicator in long bones of the Canada goose Branta canadensis (Anseriformes: Anatidae)

Growth series of femora, tibiotarsi, and humeri of the Canada goose Branta canadensis were examined to evaluate whether bone surface textures are reliable indicators of relative age and skeletal maturity in this taxon. The relationship between surface texture and skeletal maturity was analysed by comparing element texture types with both size-based and size-independent maturity estimates. A subsample of hindlimb elements was thin sectioned to observe histological structures underlying various surface textures. Three relative age classes of elements are identifiable based on surface texture. Juvenile and subadult bone textures have fibrous and/or porous areas on the bone shaft and are distinguished by the presence (in juveniles) or absence (in subadults) of coarse longitudinal striations in proximal and/or distal regions. Adult bone texture lacks surface porosity. Immature textures are caused by channels in fibrolamellar bone intersecting the bone surface; the presence or absence of striations is determined by channel orientation. Mature textures may be underlain by fibrolamellar bone with little to no surface exposure of channels, or by lamellar bone deposited after rapid growth ceases. The utility of the textural ageing method appears intimately related to the uninterrupted determinate growth regime of Branta . This suggests that bone surface textures may prove useful as skeletal maturity indicators in both modern and fossil taxa with similar growth regimes, but may not necessarily be reliable for taxa with interrupted and/or indeterminate growth.  © 2006 The Linnean Society of London, Zoological Journal of the Linnean Society , 2006, 148 , 133–168.     

Settlement and population dynamics of the alien invasive Branchiomma bairdi (Annelida: Sabellidae) in the Mediterranean Sea: two years of observations in the Gulf of Taranto (Italy)

Since the first discovery along the Italian coasts in 2004 of the polychaete Branchiomma bairdi, it has spread very quickly, reaching some localities in very high densities. In order to monitor its colonization, recruitment was investigated by means of PVC panels immersed in the Mar Grande of Taranto (Ionian Sea). Panels were monitored every three months from April 2013 to January 2015. The species showed the ability to settle on bare panels as well as on panels with a developed fouling community. Two years of monitoring identified two different cohorts, with recruits appearing in both years on panels submersed from July to October. Based on these observations B. bairdi is a short-lived species (no more than one year), reproducing at a temperature ranging from 20 to 29°C and reaching sexual maturity three months after recruitment. Oocytes were found in the coelom only in the warmest months and oogenesis was not synchronous either within each individual or within the population. Total annual secondary production was estimated at 43.42?g?m^?2?year^?1. Annual mean biomass was 20.03?g?m^?2. The corresponding P/B ratio was 2.1678. This study may explain the invasiveness of B. bairdi; indeed, a rapid generation turnover coupled with a short lifespan, rapid growth and early maturity are common traits in most invasive species.     

Relative growth and size at onset of sexual maturity of the brown crab,Cancer pagurus in the Isle of Man,Irish Sea

In this study, the relative growth, size–weight relationships and size at onset of maturity of the brown crab Cancer pagurus were investigated in the Isle of Man. For the analyses of relative growth and size at onset of maturity, the samples were collected seasonally between autumn 2012 and spring 2013 using several methods: pot surveys, dredge and trawl surveys, market surveys and shore surveys. Results showed that allometric growth occurred in the chelipeds of males (n?=?87) and in the abdomen of females (n?=?222). Four different measures of maturity (behavioural, functional, morphometric and physiological) were examined. With respect to the behavioural maturity, the smallest female crab found with a sperm plug measured 110?mm CW, whereas in terms of functional maturity the smallest ovigerous female had a CW of 134?mm. Based on direct observations of gonad maturity, 50% of females were mature at 108?mm CW, whereas 50% of males were mature at 89?mm CW. The size at the onset of maturity measurements of female and male C. pagurus based on gonad development is smaller than the current minimum landing size (130?mm), and therefore this suggests that the current minimum landing size is an adequate management measure.     

Differences in life-history traits in two clonal strains of the self-fertilizing fish, <Emphasis Type="BoldItalic">Rivulus marmoratus</Emphasis>

Synopsis We compared life-history traits such as fecundity, sex ratio, reproductive cycle, age at sexual maturity, embryonic period, egg size, early growth and morphology in two clonal strains (PAN-RS and DAN) of the mangrove killifish, Rivulus marmoratus, under constant rearing conditions. We found a positive relationship between growth and reproductive effort. Fecundity was significantly higher in the PAN-RS strain than in the DAN strain. The sex ratio was significantly different, with DAN producing more primary males than PAN-RS. Spawning and ovulation cycle did not clearly differ between the strains. PAN-RS showed a significantly higher growth rate than DAN from 0 to 100 days after hatching, however, age at sexual maturity, embryonic period, egg size, and morphometric and meristic characteristics (vertebral and fin-ray counts) did not differ between the two strains. The high fecundity of PAN-RS may provide an increased chance of offspring survival, while the attainment of sexual maturity at a smaller size in DAN may allow them to invest earlier in reproduction to increase breeding success. Variations in the life-history traits of PAN-RS and DAN may be adaptive strategies for life in their natural habitat, which consists of mangrove estuaries with a highly variable environment.     

Asynchronous dentofacial development and dental crowding: a cross-sectional study in a contemporary sample of children in France

Background

The causes of dental crowding are not fully understood, but it may result from an evolutionary trend towards reduced facial volume, without a proportional reduction in tooth sizes. Most previous studies conducted among modern humans have revealed a very low or non-existent correlation between tooth size and jaw size. Cross-comparison between dental age and facial skeletal age could help to provide better knowledge of the dynamic process of dental crowding. The primary objective of this research was to study the synchronism of dental maturation and skeletal facial growth in a sample of modern children living in France. The secondary objective was to assess the link between dentofacial asynchronism and dental crowding.

Results

The random sample comprised 28 subjects (16 girls, 12 boys). Mean chronological age was 13.5 years (±2.1; range 9.2–17.6). Mean dental age was 14.2 years (±2.8; range 7.5–17) and mean facial skeletal age was 12.8 years (±2.6, range 7–22). In the estimations of dental age and facial skeletal age, there was no evidence of systematic bias. There were 10 subjects (9 girls, 1 boy) with asynchronous dentofacial development. Finally, there were 13 subjects (8 girls, 5 boys) with dental crowding. A significant association was found between delayed facial skeletal growth/advanced dental maturation and dental crowding (P = 0.01).

Conclusions

Dental maturation and facial growth are not necessarily synchronous. Further understanding of the interactions between dental maturation and facial growth could have crucial implications in biological anthropology, as well as for the clinical practice of orthodontists. From an anthropological perspective, this study suggests that asynchronous dentofacial development could, at least partially, explain the frequency of dental crowding in modern populations.     

Relationships of reproductive traits and body size with attainment of sexual maturity and age in Blanding's turtles (Emydoidea blandingi)

To place associations among body size, age at maturity, age, and reproductive traits of a long-lived organism in the context of current life history models based on the concept of norms of reaction, we examined data from a mark-recapture study of Blanding's turtles (Emydoidea blandingi) in southeastern Michigan during 24 of the years between 1953 and 1988. Females matured between 14 and 20 years of age. Both the smallest and largest adult females in the population were reproducing for the first time in their lives. This result suggests that a combination of differences in juvenile growth rates and ages at maturity, and not indeterminate growth, are the primary cause of variation in body size among adults. Body size variation among individuals was not related to age at sexual maturity. Females that had slower growth rates as juveniles matured later at similar mean body size compared to those with more rapid growth that matured at an earlier age. As a result, a linear model of age at sexual maturity with growth rates of primiparous females between hatching and maturity was significant and negative (R² = 0.76). Frequency of reproduction of the largest and smallest females was not significantly different. Clutch size did not vary significantly with age among either primiparous or multiparous females. Clutch sizes of primiparous females and multiparous females were not significantly different. However, older females (>55 years minimum age) reproduced more frequently than did younger females (minimum age <36 y).