Somatic Growth Rate Research Articles

Growth of sprat Sprattus sprattus larvae in the German Bight (North Sea) as inferred by otolith microstructure

Growth of sprat larvae was studied in the German Blght of the North Sea and 2 different statlons (stratlfled and mixed water masses) were compared. Sprat larvae were aged using dally growth increments in sagittal otoliths. The daily nature of otolith growth increments was corroborated using the marginal increment technique. The data presented are consistent with the deposition of one complete increment per 24 h period, indicating that at least larvae with lengths greater than 11.0 mm form daily growth increments in their otoliths. There was some evidence that daily growth increments are deposited on the otoliths of sprat larvae only after the onset of exogenous feeding. Integrated somatic growth rate was 0.406 mm d-'. This value is comparable to others obtained for similar pelaglc clupeoid species. There were no significant differences between growth rates at the 2 stations.

Demersal fish populations in the Japan sea from the viewpoint of benthic fish management

First, this paper reviews the main studies so far performed on fishing ground environments and the faunistic peculiarities of demersal animals in the Japan Sea. Next, an examination is made of changes in the catch of demersal populations over a long period. Of the exploited demersal fish populations in the Japan Sea, some have decreased in catch, while others have been relatively stable for a few decades. A comparison of the life history characteristics of flatfishes is carried out on the basis of the above finding. The comparison shows that populations with strong resistance to intensive fishing slow their somatic growth rate and contribute vigorously to reproduction at young ages relative to life span, and vice versa. In addition, a theoretical analysis suggests that the effect of fishing pressure on a population probably depends on the extent of variations in its life history characteristics, which have a genetic basis, in the period when it was little exploited.

Seasonality and the scheduling of life history at different latitudes

For many ectotherms, the annual cycle is partitioned into ‘growing’ (summer) and ‘non‐growing’ (winter) seasons, and the lengths of these seasons are inversely related across a latitudinal gradient. This pattern of variation has the potential to affect diverse life‐history traits profoundly. A key selective agent is size‐dependent winter mortality which, with increasing latitude, places an increasing premium on attainment of large body size before the first winter of life. Winter body size is determined primarily by two factors: (1) birth date, which defines the beginning of the first growing season and (2) somatic growth rate within the first season. Using examples drawn from the Atlantic silverside, Menidia menidia (L.), and other fishes, I show how latitudinal variation in the scheduling of the spawning season, countergradient variation in the capacity for growth and reproduction, and mode of sex determination (environmental v. genetic) represent adaptations to seasonality.

Reproductive investment and somatic growth rates in longear sunfish

Allocation of energy to current reproduction at the expense of other functions, such as growth, can limit future reproductive potential. This cost of reproduction is a central concept of life history theory but has been difficult to verify in comparative field studies. Three levels of comparison of growth rates and reproductive investments were evaluated within and among populations of longear sunfish,Lepomis megalotis. All three demonstrated high levels of reproductive investment associated with reduced somatic growth. Within populations of central longear sunfish there are precociously mature sneaker makes and later maturing parental makes; sneakers have greater gonadosomatic index (GSI) values and slower somatic growth rates than parental makes. Between subspecies of longear sunfish grown under common conditions, there are differences in age at maturity and in the level of physiological reproductive investment that are associated with distinct differences in growth rates. Between populations of central longear sunfish inhabiting different sites, there are differences in the level of reproductive investment that are also associated with differences in somatic growth. Each comparison produced evidence that trade-offs occur between these life history traits, supporting the hypothesis that there is a cost of reproduction among male sunfish and suggesting that differences in strategies of reproductive investment contribute to variation in somatic growth.

Nonlinear and Logistic Growth In Experimental Populations of Guppies

Previous experiments have shown that for a specific experimental system of guppies (Poecilia reticulata), per capita growth rate is linearly related to population biomass. A length—specific population model is developed to examine how the various mechanisms of density dependence (i.e., changes in somatic growth rates, reproductive rates, and cannibalism) act in concert to shape the overall population response to intraspecific competition. Despite many nonlinear components, equilibrium per capita growth in the model is linearly related to population biomass, mimicking the logistic growth seen in the experiment. Using the model, the components of density dependence are varied to determine how each component shapes the overall density—dependent response. Density dependence in somatic growth rates is found to be the most important population—regulating mechanism in this system. In the past, emphasis has been placed on density dependence in birth and death functions. The importance of somatic growth in shaping per capita population growth curves may be underestimated.

Alterations in postnatal intestinal function during chronic hypoxemia.

Growth failure is a major complication of chronic hypoxemia, as seen in infants and children with cyanotic congenital heart disease. To determine whether chronic hypoxemia during infancy affects the gastrointestinal tract, we examined small intestinal growth and digestive enzyme activities in chronically hypoxemic newborn lambs and in age-matched controls. Chronic hypoxemia was produced by placing an inflatable occluder around the main pulmonary artery and performing a balloon atrial septostomy. Aortic oxygen saturation was reduced to 60-74% for 2 wk, after which the small intestine was removed for analysis. During chronic hypoxemia, somatic growth rate was decreased to 60% of control (hypoxemic, 135 +/- 20 versus control, 216 +/- 26 g/d, p less than 0.02). No differences in caloric intake were found (hypoxemic, 129 +/- 4 versus control, 128 +/- 4 kcal/kg/d). Chronic hypoxemia did not alter small intestinal growth, as measured by jejuno-ileal weight, jejuno-ileal length, mucosal weight, or mucosal protein or DNA contents. However, sp act of lactase, the principal disaccharidase of the infant lamb intestine, were significantly decreased (hypoxemic, 0.08 +/- 0.01 versus control, 0.146 +/- 0.03 units of enzyme activity/mg DNA, p less than 0.05), as were the total small intestinal contents of lactase (hypoxemic, 61.7 +/- 7.0 versus control, 120.6 +/- 21.7 units of enzyme activity, p less than 0.01). There also were decreases in specific and total activities of other digestive enzymes such as maltase, amino-oligopeptidase, and alkaline phosphatase in hypoxemic intestine that did not achieve statistical significance.(ABSTRACT TRUNCATED AT 250 WORDS)

Do Otoliths record changes in somatic growth rate? Conflicting evidence form a laboratory and field study of a temperate Reef Fish, Parika scaber

Otolith increment widths in a temperate reef fish, Parika scaber (Pisces:Monacanthidae), have been shown to vary in different months and to correlate with changes in somatic growth rate. This results in the persistence of a constant otolith-size/fish-size relationship. In the present study, the response of otolith growth to laboratory-induced changes in body growth was determined over a 10-day period in December 1985. Juveniles were subjected to two ranges of temperature (19-21�C and 24-26�C) and three feeding levels (fully fed, partially fed, and starved) of a diet consisting of larvae of Opifex fuscus, an endemic mosquito. Fish were individually tagged to ensure that changes in growth rate and any associated changes in otolith microstructure could be accurately determined for any individual. Fully fed fish grew more slowly during treatment than they did prior to treatment, and starved fish did not grow at all. Partially fed fish exhibited a size-hierarchy effect, with larger fish increasing in body size at the expense of smaller individuals. No temperature effect on growth rate was recorded. In contrast to the results from an associated field study, otoliths of fully fed fish continued to increase at the same daily width despite the induced alteration in growth rate. Thus, otoliths were disproportionately large compared with estimates from the field. However, otoliths of starved fish were not as large as predicted from a continual production of daily rings at a constant width. Daily ring deposition may have ceased at different times during the experiment for the starved fish, depending on body size. Alternatively, deposition may have continued, but at a spacing that was not detectable by light microscopy. We conclude that adequate validation of response of otolith growth to changes in somatic growth is necessary before individual growth histories can be back-calculated. This is true even where strong evidence from the field suggests that back-calculation is possible.

Short-term adult exposure to estradiol feminizes the male pattern of spontaneous and growth hormone-releasing factor-stimulated growth hormone secretion in the rat

Experimental evidence indicates that the neonatal gonadal steroid environment is an important determinant of the sexual dimorphism of GH secretion and body growth. However, the influence of the sex steroids in GH control during adult life and their mechanism/site of action are largely unknown. In the present study we examined the effects of adult gonadectomy (GNX) and short term adult exposure to 17 beta-estradiol (E2) on both spontaneous and GRF-stimulated GH release in free-moving adult male rats. The rate of body weight gain was also monitored. GNX (3 weeks postoperatively) resulted in a 2-fold reduction in GH pulse amplitude compared to that in sham-operated control rats, but did not significantly alter the GH nadir or the interpeak interval. Exposure to E2 (sc implants) for 4 days markedly disrupted the spontaneous GH secretory profile of both sham-operated and GNX rats; E2-treated animals exhibited a striking elevation (4- to 20-fold) of GH trough levels and a significant decrease in GH interpeak interval, remarkably similar to the typical female rat GH secretory profile. The augmentation in both GH nadir and GH pulse frequency was evident as early as 12 h after a single sc injection of E2 valerate. In sham and GNX rats bearing control implants, the GH response to 1 micrograms rat GRF-(1-29)NH2, iv, was significantly greater when GRF was administered at peak (1100 h) than at trough (1300 h) times of GH secretion; the latter is known to be due to antagonism by the cyclical increased release of endogenous somatostatin (SRIF) in the male rat. Treatment with E2 abolished this time-dependent difference in both groups and produced a regular pattern of GH responsiveness to GRF similar to that typically observed in the female rat, thus suggesting that E2 has altered the pattern of hypothalamic SRIF secretion from a cyclic to a more continuous mode of release. Chronic exposure to E2 for 2 weeks resulted in an almost 6-fold inhibition of the rate of body weight gain in sham-operated male rats to levels comparable to those in normal adult female rats. Taken together, these results demonstrate that short term exposure to E2 during adult life can profoundly feminize the male pattern of spontaneous and GRF-stimulated GH secretion, as well as rate of somatic growth.(ABSTRACT TRUNCATED AT 400 WORDS)

Short-term adult exposure to estradiol feminizes the male pattern of spontaneous and growth hormone-releasing factor-stimulated growth hormone secretion in the rat.

Experimental evidence indicates that the neonatal gonadal steroid environment is an important determinant of the sexual dimorphism of GH secretion and body growth. However, the influence of the sex steroids in GH control during adult life and their mechanism/site of action are largely unknown. In the present study we examined the effects of adult gonadectomy (GNX) and short term adult exposure to 17 beta-estradiol (E2) on both spontaneous and GRF-stimulated GH release in free-moving adult male rats. The rate of body weight gain was also monitored. GNX (3 weeks postoperatively) resulted in a 2-fold reduction in GH pulse amplitude compared to that in sham-operated control rats, but did not significantly alter the GH nadir or the interpeak interval. Exposure to E2 (sc implants) for 4 days markedly disrupted the spontaneous GH secretory profile of both sham-operated and GNX rats; E2-treated animals exhibited a striking elevation (4- to 20-fold) of GH trough levels and a significant decrease in GH interpeak interval, remarkably similar to the typical female rat GH secretory profile. The augmentation in both GH nadir and GH pulse frequency was evident as early as 12 h after a single sc injection of E2 valerate. In sham and GNX rats bearing control implants, the GH response to 1 micrograms rat GRF-(1-29)NH2, iv, was significantly greater when GRF was administered at peak (1100 h) than at trough (1300 h) times of GH secretion; the latter is known to be due to antagonism by the cyclical increased release of endogenous somatostatin (SRIF) in the male rat. Treatment with E2 abolished this time-dependent difference in both groups and produced a regular pattern of GH responsiveness to GRF similar to that typically observed in the female rat, thus suggesting that E2 has altered the pattern of hypothalamic SRIF secretion from a cyclic to a more continuous mode of release. Chronic exposure to E2 for 2 weeks resulted in an almost 6-fold inhibition of the rate of body weight gain in sham-operated male rats to levels comparable to those in normal adult female rats. Taken together, these results demonstrate that short term exposure to E2 during adult life can profoundly feminize the male pattern of spontaneous and GRF-stimulated GH secretion, as well as rate of somatic growth.(ABSTRACT TRUNCATED AT 400 WORDS)

Differences in somatic and organ growth rates in infants who died of sudden infant death syndrome.

The aim of present investigation was to study the changes in weight and external measurements and the rates of growth of the internal organs and to compare these findings in infants who died of the sudden infant death syndrome (SIDS). The subjects were 165 infants (100 males and 65 females) who died in Leningrad in 1983-1989 in the first five months of life. Relative growth rates for each month were calculated for weight, external measurements and organ growth, and their ratio was also calculated. Apparent discordance in growth rates was revealed when contrasting the rates for weight, length, head and chest circumference to the growth rates of internal organs and when compared them with each other. The present data show the relation of specific growth patterns to SIDS.

Ocular morphology of the sweep Scorpis lineolatus and the spotty Notolabrus celidotus (Pisces: Teleostei) grown in low intensity light.

Adults of two species of teleost fishes, the New Zealand sweep (Scorpis lineolatus) and the spotty (Notolabrus [formerly Pseudolabrus] celidotus), were recovered from dark, sealed sea water storage tanks after an extended period of residence (physical constraints meant that fish could only have entered the system as larvae or small juveniles). Individuals of both species had proportionately larger eyes than normal fishes of similar body size. Age estimation, based on unvalidated annual increments in otoliths indicated that fishes from the water tanks were all older (i.e. slower-growing) than normal fishes of similar size. This suggests that the increase in relative eye size in tank fishes may have been the result of maintenance of ocular growth, in the face of reduced rates of somatic growth, and raises the question as to whether eye growth in fishes generally, is a temporal function. In addition to ocular enlargement, sweeps from the water tanks also showed reduced densities of cones, rods, ganglion cells and, in some cases bipolar cells compared to normal fishes of similar body size. Cone, rod and bipolar cell densities of tank fishes were not different when compared with normal fishes of similar eye size; however, ganglion cell numbers were still lower than in normal fishes. This suggests that changes in cone, rod and bipolar cell densities in tank fishes resulted from the normal changes that occur with ocular growth, whereas low ganglion cell densities were a direct result of the abnormal photic environment. In contrast to the sweeps, most of the spotties from the water tanks did not show differences in retinal cell densities relative to normal fishes.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of temperature on hatchability, development and growth of eggs and yolksac fry of Oreochromis mossambicus (Peters) under artificial incubation

. The eggs and yolk sac fry of the mouth brooding tilapia. Oreochromis mossambicus (Peters), were artificially reared in an experimental hatchery system at different temperatures. The hatchability, embryonic development of eggs and growth of yolk sac fry were studied under controlled conditions. It was shown that the upper lethal temperature for O. mossambicus eggs was above 40°C and the lower lethal temperature between 11°C and 17°C. For yolk sac fry these values lay between 34 and 40°C and 17 and 20°C respectively. Fry survival between 24·3 and 34·0°C was near to 100% while al 20°C it was less than 60%. The somatic growth rates of fry at temperature between 20 and 34·5°C up to 10 days post hatch are presented and were found to differ significantly. At 34·6°C a negative SGR was recorded during the period 6–9 days post hatching, but, during the first 6 days, the SGR at this temperature was more than four times higher than at 20°C. At the elevated temperatures, the utilization of yolk is faster and the loss of weight observed was due to starvation. This should be taken into account when incubating under artificial rearing condition so that initiation of exogenous feeding is timed most appropriately.

Otolith Development, Increment Formation, and an Uncoupling of Otolith to Somatic Growth Rates in Larval and Juvenile Goldfish.

Otolith Development, Increment Formation, and an Uncoupling of Otolith to Somatic Growth Rates in Larval and Juvenile Goldfish.

Growth dynamics of the red, pink and white fibres in the caudal fin muscle in relation to the somatic growth in few marine fish

The growth patterns of red, pink and white fibres in the caudal fin muscle of five marine fishes, in relation to their somatic growth rate, are discussed in the present article. The results show that the fast growing species showed continuous recruitment of small new fibres and the slow growing species showed an increase in the fibre diameter of existing fibres instead of recruitment of new fibres. While the moderate growing species possessed both the processes equally. The results indicate that the growth dynamics of all the fibre types are related to the same found in the myotomal muscle and paralleled with the somatic growth rate. Studying the relationship between cessation fork length (x) and ultimate size (y) by regression equation of y = —0.2557 + 1.90x, it is revealed that when the fish acquires 53% of its ultimate size, the recruitment of small fibres stops and further growth occurs by an increase in the diameter to reach the ultimate size of the species.

Interpretation of Otolith Microstructure in Juvenile Winter Flounder (Pseudopleuronectes americanus): Ontogenetic Development, Daily Increment Validation, and Somatic Growth Relationships

In winter flounder (Pseudopleuronectes americanus), sagittae developed secondary origins of calcium carbonate deposition during metamorphosis just prior to completion of eye migration. Sagittae and lapilli of larvae were bilaterally symmetrical, but those of postmetamorphic individuals showed increasing morphological asymmetry between the left and right side. In juveniles marked with oxytetracycline and maintained in field enclosures for 10 d, increment deposition on sagittae was daily if somatic growth following marking was good (> 0.25 mm∙d−1), but less than daily in individuals with poor or negative somatic growth (< 0.25 mm∙d−1). Narrowly spaced increments or divergence of otolith growth from the main rostral–postrostral growth axis, where counts were made, may have limited detection of daily deposition. Lack of detectable daily increments occurred primarily in larger juveniles (> 50 mm total length), which had lower absolute growth rates than newly settled juveniles. In oxytetracycline-marked fish there was a significant correspondence between otolith growth and somatic growth in both length and weight. The strength of this relationship, which varied with the specific radius used, was highest (r = 0.854) for the rostral radius of the left sagitta; increment widths along this radius are reliable estimators of prior somatic growth rates.

Sexual Dimorphism of Somatostatin and Growth Hormone-Releasing Factor Signaling in the Control of Pulsatile Growth Hormone Secretion in the Rat*

A striking sexual dimorphism exists in the pattern of GH secretion and rate of somatic growth; however, the mechanism(s) mediating this sex difference is unknown. To elucidate the physiological roles of the hypothalamic neuropeptides, somatostatin (SRIF) and GRF, and their interrelation, in generating the sexually dimorphic GH secretory pattern we examined: 1) GH responsiveness to exogenous GRF and 2) the effects of immunoneutralization of endogenous SRIF and GRF on GH secretory dynamics, in free-moving male and female rats. In males, the GH response to 1 microgram rat(r)GRF(1-29)NH2 iv was significantly greater at peak compared to trough times of GH secretion (925.2 +/- 250.8 vs. 95.6 +/- 27.8 ng/ml; P less than 0.02), the latter known to be due to antagonization by the cyclic increased release of endogenous SRIF. In contrast, females failed to exhibit a time-dependent difference in GH responsiveness to GRF. Passive immunization with a specific antiserum to SRIF in males resulted in significant elevation of GH nadir levels but had no effect on GH peak amplitude. In contrast, immunoneutralization of endogenous SRIF in females caused a marked augmentation of plasma GH levels at all time points; there was a significant increase in GH peak amplitude (171.3 +/- 39.9 vs. 67.5 +/- 11.3 ng/ml; P less than 0.05), GH nadir (18.3 +/- 2.7 vs. 5.8 +/- 1.1 ng/ml; P less than 0.01) and mean 6-h plasma GH level (78.7 +/- 4.1 vs. 33.1 +/- 5.8 ng/ml; P less than 0.001), compared to normal sheep serum-treated controls. These results indicate that the pattern of hypothalamic SRIF secretion in females does not follow the male-like ultradian rhythm. Passive immunization with a specific antiserum to GRF obliterated spontaneous GH pulses in both sexes. Moreover, in females, anti-GRF serum attenuated GH nadir levels (4.3 +/- 1.7 vs. 21.4 +/- 3.5 ng/ml; P less than 0.01) indicating a physiological role for GRF in maintaining the elevated basal GH level of females, in addition to its important role in generating the episodic GH pulses. Taken together, these findings provide support for the hypothesis that, in female rats, the pattern of hypothalamic SRIF secretion into hypophyseal portal blood is continuous, rather than cyclical, as in the male; whereas in the case of GRF secretion, in addition to steady-state release which occurs at a higher level in females than males, there is also episodic GRF bursting which does not follow a specific rhythm, as in the male.(ABSTRACT TRUNCATED AT 400 WORDS)

Life History Covariation in Intestinal Nematodes of Mammals

Using data on 66 species from 18 families and 6 orders, we examine patterns of interspecific covariation in female size, egg size, time from infection to production of infective stages (prepatency period), duration of reproduction (patency period), and fecundity in mammalian intestinal nematodes. Nematode species with shorter prepatency periods are smaller, have lower rates of somatic growth, lower fecundity and shorter reproductive periods; those with longer prepatency periods have the opposite suite of characters. These patterns are very different from that found in interspecific analyses of life history variation in other taxa. This may be a consequence of the energy-rich environment intestinal nematodes exploit, though comparable studies of free-living nematodes or other soft-bodied invertebrate phyla have not yet been done. The advantages of delaying reproduction, with the subsequent increase in fecundity and reproductive lifespan, depend on a number of factors, such as the relative importance of prepatency in the determination of parasite generation times, and adult mortality rates. Contrary to previous claims, nematode egg size is shown to be highly variable (as variable as female size), yet this variation is not associated with

Muscle growth in the Antarctic teleost, Notothenia neglecta (Nybelin)

A histochemical and electron microscopy study was carried out on muscle growth in demersal stages of the Antarctic teleost Notothenia neglecta Nybelin. The total number of myotomal muscle fibres was similar in fish ranging in body mass from 11.9g to 889g. Post-anal myotomes contained around 17,000 slow muscle fibres and 70,000 fast muscle fibres. Myosatellite cells were extremely rare. The diameter of fast fibres varied from <10μm to 130μm in the smallest, and from >40μm to 450μm in the largest fish studied. Slow muscle fibre diameters in the largest fish ranged from >30μm to 260μm. Even the largest diameter slow fibres contained significant numbers of mitochondria, which suggests that the diffusion of oxygen does not limit metabolism. The results confirm that muscle fibre hyperplasia ceases prior to the demersal stages of the life history, and that subsequent muscle growth is entirely via the hypertrophy of existing fibres. Comparative studies suggest that this may be one of the factors contributing to the relatively slow rate of somatic growth in this species.

Oxygen and carbon stable isotopes in the otoliths of wild and laboratory-reared Australian salmon (Arripis trutta)

Australian salmon,Arripis trutta, collected from the east coast of Tasmania, Australia, in 1987, were weighed and measured and their otoliths marked by immersing fish in an oxytetracycline hydrochloride/seawater solution before placement in constant-temperature aquaria. Individual somatic and otolith growth rates were determined for input into mass balance models. Mass balance models were used to determine the oxygen and carbon isotopic composition of otolith material produced during captivity. There was a significant relationship betweenδ 18O measured in the otolith aragonite and ambient temperature (r 2 = 0.77). The linear relationship between these data, whereδ 18O = 6.69 − 0.326 (T, °C), was not significantly different from a relationship indicative of equilibrium deposition of oxygen isotopes in aragonite. Otolith carbon was significantly depleted in13C relative to equilibrium deposition, with depletions >6.0‰ at all temperatures. There was no relationship betweenδ 13C and temperature. It was estimated that >30% of the otolith carbon was from metabolically derived sources. Significant differences in otolith carbon isotopes among wild juvenile Australian salmon were hypothesised to be attributable to differences in diet. Levels of variability for both oxygen and carbon isotopes in laboratory-maintained and wild fish were similar to that found by other researchers for foraminifera and these results highlight the importance of large sample sizes when estimating environmental temperatures from oxygen isotopes measured in fish otoliths.

How Reliable are Growth Back-Calculations Based on Otoliths?

Growth back-calculations from otoliths assume that the relationship between fish and otolith length is linear through time. The final (or observed) individual fish-otolith ratios are then combined to prepare a fish-otolith regression for the population, upon which the subsequent back-calculations are based. However, recent studies have demonstrated that the fish:otolith size ratio varies systematically with somatic growth rate, resulting in relatively large otoliths in slow-growing fish. Such a growth effect will result in a fitted fish-otolith regression which differs significantly from that of the mean of the individual fish-otolith slopes. Fraser–Lee growth back-calculations made from such a regression consistently underestimate previous lengths at age. The bias may explain the apparent ubiquity of Lee's phenomenon. Back-calculation bias was eliminated through use of an algorithm defining individual fish-otolith trajectories and a biologically determined, rather than a statistically estimated, intercept. Adaptations of the biological intercept back-calculations procedure accurately predicted previous lengths in the presence of both stochastic error and time-varying growth rates. When used to reevaluate some published back-calculations, the biological intercept procedure resulted in more accurate values than those previously estimated, and reduced or eliminated the presence of Lee's phenomenon.