Individual growth of <Emphasis Type="Italic">Lymnaea stagnalis</Emphasis> (Lymnaeidae,Gastropoda): II. Late postlarval ontogeny

Our investigation on the growth of 14 individuals of the great pond snail Lymnaea stagnalis was performed in an aquatic culture at 18°C beginning from the 10th week after hatching until death. It has been demonstrated that the increase in the mollusk mass follows an S-like curve during the whole studied period. Linear growth (conch height) follows a parabolic (convex) curve until the age of 39 weeks. Both weight and linear growth during studied period significantly approximate to the Bertalanffy equation, while the interrelation between mass and conch height corresponds to the allometric equation. The meanings of the coefficients of these equations do not differ significantly in different individuals. At the age of 38 to 39 weeks, all mollusks demonstrate breakage in the curve of linear growth, then followed with abrupt slowing of growth until stopping or even decreasing in size in some cases. Neither the Bertalanffy equation nor the allometric relation describe the linear growth of individuals with ages exceeding 39 weeks.     

Growth and age determination of African savanna elephants

Understanding the population dynamics of savanna elephants depends on estimating population parameters such as the age at first reproduction, calving interval and age-specific survival rates. The generation of these parameters, however, relies on the ability to accurately determine the age of individuals, but a reliable age estimation technique for free-ranging elephants is presently not available. Shoulder heights of elephants were measured in 10 populations in five countries across southern and eastern Africa. Data included shoulder height measurements from two populations where the age of each individual was known (i.e. Addo Elephant National Park, South Africa and Amboseli National Park, Kenya). From the known-age data, Von Bertalanffy growth functions were constructed for both male and female elephants. Savanna elephants were found to attain similar asymptotic shoulder heights in the 10 populations, while individuals in the two known-age populations grew at the same rate. The Von Bertalanffy growth curves allowed for the accurate age estimation of females up to 15 years of age and males up to 36 years of age. The results indicate that shoulder height can serve as an indicator of chronological age for elephants below 15 years of age for females and 36 years of age for males. Ages derived from these growth curves can then be used to generate age-specific population variables, which will help assess the demographic status of savanna elephant populations across Africa.     

The growth and energy metabolism of <Emphasis Type="Italic">Lymnaea stagnalis</Emphasis> (Lymnaeidae,Gastropoda): I. Early postlarval period

The growth and the oxygen consumption rate of Lymnaea stagnalis were studied during the first ten weeks after hatching. It is shown that these processes are atypical during early ontogenesis in comparison with adult mollusks. The obtained data on linear (height of shell) and weight growth can be equally well approximated with the von Bertalanffy equation or exponential and power equations. Both linear and weight growth are characterized by an approximately constant specific rate associated with synchronous oscillations of a week period. The oscillations were observed also for the oxygen consumption rate, but of another period (about 2.6 weeks). On average the metabolic rate after the initial triple increase during the first three days remains stable. The power coefficient of the allometric dependence of the total weight on the shell height is significantly less than that of the adult.     

Post-natal growth of elephants Loxodonta africana in Etosha National Park, Namibia

Post-natal growth in the African elephant ( Loxodonta africana ) was described using three alternative mathematical models, and two age estimation schedules. Von Bertalanffy, Gompertz and Logistic equations all provided adequate models of post-natal growth in a species for which age estimation methods are largely unsubstantiated. Gompertz and Logistic models overestimated pre-weaning growth and underestimated adult size. Self-accelerating growth is of short duration (one and three years in females and males, respectively), and we found no evidence of a secondary growth spurt in males. Males, nevertheless, continue to grow throughout their lifespan, while females reach asymptotic size at the age of 35–40 years. We found no evidence of differences in growth rate of males and females up to 10 years, and there does not seem to be differential investment in male and female offspring. Growth rates of captive elephants differ substantially from all wild populations studied and may not serve as adequate references for the revision of existing age estimation schedules.     

The growth of the freshwater murrel,Ophicephalus punctatus Bloch

Summary The growth of O. punctatus has been studied from the zones on the opercular bones and scales. Size estimates obtained from the opercular bones and scales were further substantiated by length frequency distribution and back-calculations. A close agreement in length-age relationship was obtained by various methods. These observations provide adequate evidence towards the validity of age determination in O. punctatus.Growth rate differs markedly in the two sexes. Males grow faster than the females. To study the changes in length with age, von Bertalanffy growth equation and Gompertz curve were used. The theoretical lengths obtained from the von Bertalanffy equation agreed very closely with the observed lengths.There is sexual difference in the weight-length relationship of O. punctatus. Modal weight of each year class obtained according to age reading showed that growth in weight is faster in males. The theoretical growth equation gives a good fit for weight-age data. O. punctatus is generally a fish of the impounded waters. The interrelationship between pond environment and growth characteristics has been discussed.     

Patterns of reproductive strategy parameters in some marine teleost fishes

The development of ideas and methods in the quantitative study of the patterns of growth, maturation and longevity in fish is reviewed. Earlier studies on length and age at maturity, von Bertalanffy growth formula parameters, natural mortality and maximum age for clupeiformes, pleuronectiformes, gadiformes and Sebastes spp. are up-dated and extended. The concept of the Growth-Maturity-Longevity (GML) plot is developed and applied. GML plots for the gadiformes and pleuronectiformes occupy the same two-dimensional space, but those for clupeiformes and Sebastes are located differently from them and from each other. The GML parameter suite for long-lived Sebastes spp. is similar to that of certain higher vertebrates of comparable longevity (minke whale and African elephant). It is suggested that the conventional distinction between the growth of fish being indeterminate and that for higher vertebrates determinate is inappropriate; the main difference is whether the approach to the characteristic maximum size is asymptotic , as in fish and some higher vertebrates, or abrupt as in others, including man.     

Variation in clones of the sperm-dependent parthenogenetic Carassius gibelio (Bloch) in Lake Pamvotis (north-west Greece)

Variation in three different clones of the invasive sperm-dependent, cyprinid fish Carassius gibelio were examined in Lake Pamvotis (north-west Greece). Differences between the clones were found in their proportion in the population, in their age structure, in the time of arrival to their spawning grounds and in the coefficients of the von Bertalanffy growth equation.     

Modelling the growth of Japanese eel Anguilla japonica in the lower reach of the Kao-Ping River, southern Taiwan: an information theory approach

Information theory was applied to select the best model fitting total length ( L _T)-at-age data and calculate the averaged model for Japanese eel Anguilla japonica compiled from published literature and the differences in growth between sexes were examined. Five candidate growth models were the von Bertalanffy, generalized von Bertalanffy, Gompertz, logistic and power models. The von Bertalanffy growth model with sex-specific coefficients was best supported by the data and nearly overlapped the averaged growth model based on Akaike weights, indicating a similar fit to the data. The Gompertz, generalized von Bertalanffy and power growth models were also substantially supported by the data. The L _T at age of A. japonica were larger in females than in males according to the averaged growth mode, suggesting a sexual dimorphism in growth. Model inferences based on information theory, which deal with uncertainty in model selection and robust parameter estimates, are recommended for modelling the growth of A. japonica .     

Growth curves of body weight changes in laboratory-bred female African green monkeys (Cercopithecus aethiops)

Nonlinear growth models having three or four parameter family were applied to individual weight data of female African green monkeys for estimating their growth pattern. The body weight was measured continuously from birth to six years of age with five female laboratory-bred monkeys. A total of 95 weight data were collected from each monkey. The average body weight was 330 g with the standard deviation of +/- 15 g at birth, and 2.71 +/- 0.33 kg at four years of age. The body weight of female African green monkeys was judged to reach a plateau after about four years of age. Five growth models (Gompertz, Logistic, Richards, Bertalanffy, Brody) were applied to these weight to age data. The most suitable coefficient of determination between growth data and growth model was obtained by the application of Gompertz equation. Three parameters of Gompertz equation, mature size (A), rate of maturing (K) and inflexion point (e-1 A) were analyzed in relation to age of menarche. Strong correlations between age of menarche and maturing rate, as well as between age of menarche and inflexion point were observed.     

Population dynamics of the African elephant (Loxodonta africana)

Recent studies on elephant populations from East Africa and from Zambia have suggested that as population density increases, so does the mean age at puberty and the mean calving interval. At the same time there is also an increase in the proportion of old females that are reproductively inactive. By constructing elephant population models, it is possible to investigate the extent to which these "homeostatic mechanisms" will regulate an elephant population. The models indicate that a change in the duration of the calving interval is more important as a population regulating mechanism than a change in the age at puberty, and that the proportion of old reproductively inactive females is of little significance. The importance of neonatal mortality in controlling population growth is emphasised by the models, and they also show that an annual population increase of 4% would be close to the maximum value.     

Growth, condition and reproduction in the Impala ram (Aepyceros melampus)

The relationship between reproductive activity, body growth and condition in the male Impala is examined. Body growth is described by the use of the von Bertalanffy equation, and asymptotic values for each parameter are given together with the age at which these are attained. Seasonal changes in body condition are determined by the use of the kidney index and the fat content of the bone marrow, and this is related to body weight and the time of the rut. Growth and development of the reproductive organs with age and season are described in relation to reproductive activity.     

Determination of the unknown age at first capture of western rock lobsters (Panulirus cygnus) by random effects model

We propose a method for fitting growth curves to multiple recapture data of lobsters when the age at first capture is unknown. The von Bertalanffy growth curve is used to model the growth. To account for individual variability, the unknown age in logarithmic scale of a lobster at first capture, the individual asymptotic size, and the individual growth coefficient of its carapace length are modeled as random effects with a trivariate normal distribution. Unlike previously suggested models, the present model permits correlation between the growth coefficient and the age at first capture and can be fitted readily using existing software. The error structures between consecutive recaptures of a lobster are assumed to be a first-order autoregressive process with unequally spaced time points. A comparison between this model and the Fabens growth equation is given. The proposed method is a flexible method and can be applied to fit different growth equations when the age at first capture is unknown.     

Equations describing changes in weight and mass-specific rate of oxygen consumption in animals during postembryonic development

Equations describing growth and respiration rate of animals during postembryonic development have been derived on the basis of thermodynamics of linear irreversible processes. The conditions for equation application are specified as well as the conditions when growth equation can be reduced to the von Bertalanffy equation and when the relationship between the mass-specific rate of oxygen consumption and body weight becomes an allometric relationship.     

Pre- and postnatal growth of the Cape porcupine Hystrix africaeaustratis

Pre- and postnatal growth of the Cape porcupine Hystrix africaeaustralis is evaluated by means of the Huggett & Widdas equation, a modification thereof, and the von Bertalanffy equation. Specific foetal growth velocity for the Cape porcupine is higher than that recorded for most other hystricomorph rodents, but similar to that recorded for large-bodied rodents of the same group. Relatively high foetal growth velocity in porcupines is ascribed to their relatively short gestation period, the latter being longer than expected for mammals of equal size, but shorter than expected for a hystricomorph rodent.
Postnatal growth is nearly linear up to the age of 20 weeks and asymptotic body weight is attained at an age of 52 weeks, this coinciding with the observed age at sexual maturity. Growth rates of males and females are similar. Their high rate of postnatal growth and development results in an extended reproductive period, thereby enhancing individual reproductive values by counteracting the effects of seasonal breeding and small litter size.     

Age determination by back length for African savanna elephants: extending age assessment techniques for aerial-based surveys

Determining the age of individuals in a population can lead to a better understanding of population dynamics through age structure analysis and estimation of age-specific fecundity and survival rates. Shoulder height has been used to accurately assign age to free-ranging African savanna elephants. However, back length may provide an analog measurable in aerial-based surveys. We assessed the relationship between back length and age for known-age elephants in Amboseli National Park, Kenya, and Addo Elephant National Park, South Africa. We also compared age- and sex-specific back lengths between these populations and compared adult female back lengths across 11 widely dispersed populations in five African countries. Sex-specific Von Bertalanffy growth curves provided a good fit to the back length data of known-age individuals. Based on back length, accurate ages could be assigned relatively precisely for females up to 23 years of age and males up to 17. The female back length curve allowed more precise age assignment to older females than the curve for shoulder height does, probably because of divergence between the respective growth curves. However, this did not appear to be the case for males, but the sample of known-age males was limited to ≤27 years. Age- and sex-specific back lengths were similar in Amboseli National Park and Addo Elephant National Park. Furthermore, while adult female back lengths in the three Zambian populations were generally shorter than in other populations, back lengths in the remaining eight populations did not differ significantly, in support of claims that growth patterns of African savanna elephants are similar over wide geographic regions. Thus, the growth curves presented here should allow researchers to use aerial-based surveys to assign ages to elephants with greater precision than previously possible and, therefore, to estimate population variables.     

Some biological characteristics of Hemigrammocapoeta kemali (Hanko, 1924) in Işıklı Lake (Denizli-Turkey)

Totals of 284 Hemigrammocapoeta kemali specimens were caught during 1998 in the I??kl? Lake, Turkey. Their ages, lengths and weights were determined to estimate length–weight relationships and age composition. Fecundity and oocyte diameter were also determined. The sex ratio was 1 : 1.29. Fork length and total weight of specimens ranged from 3.4 to 8.2 cm and from 0.5 to 6.9 g, respectively. Maximum age observed was 4 years. The length–weight relationship for all fish was best described by the equation W = 0.0121*L^3.06; the von Bertalanffy growth equations for length and weight were Lt = 8.73[1?e^{?0.401(t + 0.947)}]; Wt = 9.17[1?e^{?0.401(t + 0.947)}]^3.06. Oocyte numbers varied from 220 to 1159 and oocyte diameters ranged between 450 and 900 μm.     

Defaecation by African elephants (Loxodonta africana africana (Blumenbach))

A study of defaecation in the African elephant was carried out at the Voi headquarters of the Tsavo (East) National Park. Four orphaned animals aged between 1 and 10 years were observed for 4 days and 3 nights. During the day the time and weight of each individual's defaecation was recorded while at night only the time of defaecation. Details of all the records are presented. Analysis has shown that the amount of dung produced with each defaecation bears a similar characteristic to that of the growth curve of these animals. The rate of defaecation does not vary significantly with age. Records of defaecation arranged by time demonstrate an apparent periodicity with a low peak mid-morning and a high peak mid-afternoon. The potential use of this information in feeding and population studies is discussed.     

Chick growth in albatrosses: curve fitting with a twist

We present a new type of equation to describe the growth patterns of procellariiform seabirds and other species whose chicks characteristically lose mass towards the end of the rearing period. Our equation is based on the Gompertz curve; our principles are also applicable to logistic and von Bertalanffy curves. From our model, five coefficients can be derived to characterise the patterns of growth. These are: growth rate, peak mass and age at which it is attained, loss rate and an index describing the overall shape of the curve. We illustrate the use of this new equation with data collected, using automated weighing platforms, on six years of chick growth of Black-browed Diomedea melanophris and Grey-headed D. chrysostoma albatrosses at Bird Island, South Georgia. In comparison with Grey-headed Albatross, Black-browed Albatross chicks grow at a faster rate and to a higher peak mass; they also reach their peak mass at an earlier age, and lose mass at a faster rate in the mass recession period. However, in both species, chicks reached peak mass when 72% of the rearing period had elapsed; within species, only this did not vary between years. This new equation not only enables the period of mass recession to be incorporated into growth analysis, but, because it does not require assumptions about asymptotic mass, greatly facilitates inter-species comparisons.     

Growth Characteristics of the Common Mussel Mytilus edulis from the White Sea

We studied the following growth indices of the White Sea mussels Mytilus edulis: shell length, total weight, soft tissue weight, and shell weight. The coefficients of allometric relationships between the indices were determined. Age-related changes in the indices could be approximated by the Bertalanffy equation. The maximum age of mollusks in the studied population equaled 13 years (with the maximum shell length of 66.2 mm). Growth rate of littoral mussels in the region of Umba Settlement (Northern Kandalaksha Bay) was lower as compared to those published for other littoral White Sea populations (Chupa Bay).