Survival, development and food energy partitioning of nase larvae and early juveniles at different temperatures

Survival was generally high, 94–100%, for newly hatched larvae of the nase Chondrostoma nasus held at 10, 13, 16, 19, 22, 25 and 28° C up to day 66 post-fertilization. The developmental rate decreased with age and increased with temperature. Specific growth rates increased with temperature; within one temperature range growth rate decreased with ontogenetic development. Food consumption and respiration increased with temperature and body size. A temperature increase from 25 to 28° C resulted in slightly reduced survival, minor acceleration of developmental growth and respiration rates, and impeded skeleton formation. Growth efficiency of consumed energy decreased throughout the larval period from 55 to 67% at the first larval stage (L1) to 36–48% at the first juvenile stage (J₁). A similar trend for assimilation efficiency and its utilization for growth was observed. The constant temperatures required by larval nase ranged from a minimum 8–10° C to a maximum 25–28° C. A shift of optimum temperatures, 8–12, 13–16, 15–18, 19 and 22° C for nase spawning, embryonic development, yolk feeding larvae, early externally feeding larvae and, late larvae and juveniles, respectively, paralleled the spring rise in the river water temperature. Larval and juvenile nase show high survival, growth and energy conversion efficiencies compared with other fish species. On the other hand, low survival rates and growth can be attributed to external perturbations; thus, young nase may be considered a good indicator of the environmental and ecological integrity of river systems.     

Effects of different incubation temperatures on the yolk‐feeding stage of Eupallasella percnurus(Pallas)

Embryos and yolk‐feeding larvae of lake minnow Eupallasella percnurus were reared at 13, 16, 19, 22 and 25° C with no access to external food. Time from egg activation to first embryonic movements, hatching, filling of swimbladder and final yolk resorption increased with decreasing temperature. At 13° C, c . 40% of larvae were unable to fill their swimbladder. The predicted lower temperature at which development and growth ceased (biological zero, t ₀) was the same for both processes, c . 7·5–10·5° C. There was no ontogenetic shift in the t ₀ value. Temperature coefficients for development ( Q _10dev.) ranged from 2 to 3 at 19–25° C, but were higher in hatched larvae at lower temperatures. Eggs of E. percnurus had a combination of small size, high hydration and low caloric value of fresh matter. Dry mass of larval tissue on yolk, percentage of dry matter in wet matter, and specific growth rate were maximized at 22 and 25° C. At 19–25° C, energy and matter contained in the initial eggs were converted to body tissue most efficiently. Temperatures from 22 to 25° C are considered optimal for E. percnurus embryos and yolk‐feeding larvae and are recommended for their indoor rearing.     

Phenotypic sex differentiation of blue tilapia under constant and fluctuating thermal regimes and its adaptive and evolutionary implications

Oreochromis aureus exposed during the first 28 days of exogenous feeding to constant 35° C, or fluctuating temperatures (day at 35° C, night at 27° C, and vice versa) showed significantly ( P <0·05) faster growth, least size heterogeneity and better survival rates than siblings under constant 27° C. Constant high temperatures had a strong masculinizing effect (M: F sex ratios of 7·33–19·00: 1·00 v . 0·75–0·82: 1·00 in controls reared at 27° C). Fluctuating temperatures had less masculinizing potential but still produced sex ratios significantly skewed to the detriment of females (M: F sex ratios of 2·33–11·50: 1·00). This suggests that ambient temperature may have represented a sufficient environmental pressure for the selection of thermolabile sex-determinism in this species, and presumably in other Oreochromis spp. The evolutionary advantage of thermosensitivity in Oreochromis spp. is discussed, considering a framework where individual advantages oppose, to some degree, to the population or species interest.     

Effects of temperature on developmental performance, survival and growth of sea lamprey embryos

This study assesses the influence of thermal regime on the development, survival rates and early growth of embryos of sea lamprey Petromyzon marinus incubated at five constant temperatures (7, 11, 15, 19 and 23° C). The time from fertilization to 50% hatching and from hatching to 50% burrowing were inversely related to incubation temperature. All the embryos incubated at 7° C died at very early stages, while those maintained at 11° C did not attain the burrowing stage. Survival from fertilization to hatching was 61, 89, 91 and 89% at 11, 15, 19 and 23° C, decreasing to 58, 70 and 70% from hatching to burrowing at 15, 19 and 23° C, respectively. Larvae reared during the first 3 months of exogenous feeding in a common environment at constant 21° C, revealed maximum survival for an incubation temperature of 15° C (43% of burrowed larvae) decreasing strongly at 19° C (16%) and 23° C (one suvivor among 240 larvae). Body length at the burrowing stage was maximum for embryos incubated at 19° C, but body mass increased in the interval 15–23° C. Mean incubation temperatures experienced by 117 broods during the embryonic development in the source river were estimated in 15·3±2·30° C and 16·7±1·76° C (mean±1 s.d .) for the periods fertilization-to-hatching and hatching-to burrowing, respectively.     

Temperature-induced changes of early development and yolk utilization in the African catfish Clarias gariepinus

Artificially fertilized eggs and yolk-sac larvae of a freshwater tropical/subtropical fish Clarias gariepinus receiving no external food were incubated at 22, 25 and 28° C until full yolk resorption. Developmental time, size and matter composition (CHNS-O Analyzer and ashing) were assessed at egg fertilization, hatching and yolk resorption; respiration was measured every 4–5 h. The course of acceleration of C. gariepinus embryonic developmental rate with temperature ( Q_{10 dev}) was compared over the temperature range to those of Cyprinus carpio and Oncorhynchus mykiss ; they differed greatly, but were similar when compared on the basis of effective temperatures specific to each fish. Specific growth rates for energy (88, 150 and 183% per day at 22,25 and 28° C, respectively) as well as the conversion efficiencies of egg energy (64, 71 and 68%, respectively) and protein (71, 78 and 76%, respectively) in C. gariepinus larval tissues were higher than those known for the endogenous feeding period of coldwater and temperate fish species. In C. gariepinus at the end of yolk resorption, the carbon percentage and caloric values of dry weight, size (in terms of dry matter, minerals, protein and energy per larva) and transformation efficiencies were lowest at 22° C, highest at 25° C and had slightly decreased at 28° C. A tentative mechanism which leads to the positive or negative response of body size to temperature over the viable temperature range is defined.     

Heat resistance of Cronobacter species (Enterobacter sakazakii) in milk and special feeding formula

Aim:  To determine D - and z -values of Cronobacter species ( Enterobacter sakazakii ) in different reconstituted milk and special feeding formula and the effect of reconstitution of powdered milk and special feeding formula with hot water on the survival of the micro-organism.
Methods and Results:  Five Cronobacter species (four C. sakazakii isolates and C. muytjensii ) were heated in reconstituted milk or feeding formula pre-equilibrated at 52–58°C for various times or mixed with powdered milk or feeding formula prior to reconstitution with water at 60–100°C. The D -values of Cronobacter at 52–58°C were significantly higher in whole milk (22·10–0·68 min) than in low fat (15·87–0·62 min) or skim milk (15·30–0·51 min) and significantly higher in lactose-free formula (19·57–0·66 min) than in soy protein formula (17·22–0·63 min). The z -values of Cronobacter in reconstituted milk or feeding formula ranged from 4·01°C to 4·39°C. Water heated to ≥70°C and added to powdered milk and formula resulted in a > 4 log₁₀ reduction of Cronobacter .
Conclusions:  The heat resistance of Cronobacter should not allow the survival of the pathogen during normal pasteurization treatment. The use of hot water (≥70°C) during reconstitution appears to be an effective means to reduce the risk of Cronobacter in these products.
Significance and Impact of the Study:  This study supports existing data available to regulatory agencies and milk producers that recommended heat treatments are sufficient to substantially reduce risk from Cronobacter which may be present in these products.     

Thermal dependence of swimming endurance in juvenile brown trout

The maximum swimming stamina of hatchery reared juvenile brown trout Salmo trutta , swimming against a fixed-velocity water flow of 36·6 cm s^-1 (6·97 L s^-1), was achieved at 16·1° C, and a 90% performance level occurred over a breadth of 7·7° C (12·2–19·9° C). The wide range of temperatures at which swimming performance is close to the maximal capacity could be a consequence of the implications for survival of this function.     

Influence of water temperature and feeding regime on otolith growth in Anguilla japonica glass eels and elvers: does otolith growth cease at low temperatures?

The influences of water temperature and feeding regime on otolith growth in Anguilla japonica glass eels and elvers were investigated using individuals reared at 5, 10, 15, 20, 25 and 30° C and in fed or unfed conditions at salinity 32 after their otoliths were marked with alizarin complexone (ALC). To eliminate the difficulty of observing the edges of otoliths with optical (OM) or scanning electron (SEM) microscopes, three to 10 individuals were sampled from each tank at 10, 20 and 30 days during the experiment and reared for an additional 10 days at 25° C after their otoliths were marked a second time. Otolith growth and the number of increments were measured using both OM and SEM. Most A. japonica commenced feeding after 10 days at 20–30° C or after 20 days at 15° C, but no feeding occurred at 5 and 10° C. No otolith growth occurred at 5 and 10° C except in two individuals with minimal increment deposition at 10° C. Otolith growth was proportional to water temperature within 15–25° C and not different between 25 and 30° C. At 15, 25 and 30° C, the mean otolith growth rate in fed conditions was higher than in unfed conditions. The number of increments per day was significantly different among water temperatures (0·00–0·01 day⁻¹ at 5 and 10° C, 0·43–0·48 day⁻¹ at 15° C and 0·94–1·07 day⁻¹ at 20–30° C). These results indicated that otolith growth in A. japonica glass eels and elvers was affected by temperature and ceased at ≤10° C under experimental conditions. Hence, future studies analysing the otoliths of wild-caught A. japonica glass eels and elvers need to carefully consider the water temperatures potentially experienced by the juveniles in the wild.     

Upper thermal limits for feeding and growth of 0+ Arctic charr

When Arctic charr Salvelinus alpinus from two diVerent stocks were fed live Neomysis integer , the upper thermal limits for feeding and growth were established in the range 21·5–21·8° C. These critical temperatures might have been underestimates, because fish tend to show increased sensitivity to handling at high experimental temperatures. In the second experiment, the proportion of feeding undisturbed charr from four stocks decreased initially as temperature was raised in steps from 18 to 22° C. At the lower temperatures, 18 and 20) C, almost all fish resumed feeding, but the recovery time was longer and more fish ceased to feed at 20) C than at 18° C. When the temperature was increased to 21° C, 50% of the fish ceased feeding permanently, and all fish ceased feeding within 2 days at 22° C. It is concluded that 0+ charr cease to feed and grow at c .21·5) C and that the critical temperatures for feeding and growth coincide.     

Effects of temperature and delayed initial feeding on the survival and growth of Japanese flounder larvae

The effects of the timing of initial feeding (0, 1, 2, 3 and 4 days after yolk exhaustion) and temperature (15, 18 and 21° C) on the point‐of‐no‐return (PNR), survival and growth of laboratory‐reared Japanese flounder Paralichthys olivaceus larvae were studied under controlled conditions. The larvae reached PNR on 7·7, 5·2 and 4·2 days‐post‐hatching (dph) at 15, 18 and 21° C, respectively. At each temperature, larval growth did not differ significantly among the delayed initial feedings 1 day before PNR but decreased significantly in larvae first fed after that. In the treatments where initial feeding was equally delayed, larvae grew significantly faster at 18 and 21° C than at 15° C. The larvae survived apparently better at 15 and 18° C than at 21° C when initial feeding was equally delayed. At each temperature, survival of the larvae first fed before PNR did not differ noticeably, while delayed initial feeding after that apparently reduced their survival. These results indicated that there existed a negatively temperature‐dependent PNR in the Japanese flounder larvae. Survival and growth of the larvae strongly depended on temperature as well as the timing of initial feeding. High temperature accelerated the yolk exhaustion and growth of the larvae and thus reduced their starvation tolerance and survival. To avoid potential starvation mortality and obtain good growth, the Japanese flounder larvae must establish successful initial feeding within 2 days after yolk exhaustion at 15° C and within 1 day at both 18 and 21° C.     

Early development of the skull of Sander lucioperca (L.) (Teleostei: Percidae) relating to growth and mortality

The early osteological development of the skull (chondrocranium and osteocranium) of the pikeperch Sander lucioperca was studied. Specimens were reared at two temperatures, 15·5 and 18·0° C, from hatching until 47 and 43 days after fertilization (DAF), respectively. The skeletal elements characteristic for the different developmental stages were the same at both rearing temperatures, but pikeperch reared at 15·5° C reached the developmental stages later. The formation of the functional complexes, the neurocranium, jaws and suspensorium, branchial basket and hyoid arch, was evaluated chronologically. The focus was on skull development during several functional changes: at hatching, at the shift from endogenous to mixed feeding, the shift to exclusively exogenous feeding and upon reaching the final prey-capture mechanism. Growth in total length differed between fishes reared at the two temperatures, except during a phase of very slow growth from the end of the embryonic stage until the second larval stage. The latter phase, in which most of the bony elements of the viscerocranium started to form, was marked by high mortality. When exogenous feeding began, the growth rates at both temperatures increased distinctly and the first bony elements were formed in the neurocranium. Specimens reared at 18·0° C grew continuously, but those at 15·5° C showed a second period of slow growth and high mortality. Fish reared at 18·0° C reached the successive larval stages distinctly earlier than fish reared at 15·5° C.     

Dynamics of chemical composition of the Black Sea gray mullet <Emphasis Type="Italic">Mugil cephalus</Emphasis> in the period of early ontogenesis and its dependence on temperature and salinity

Results of experiments on the study of the effect of temperature and salinity on dynamics of the chemical composition of gray mullet Mugil cephalus in the embryonic-larval period of development are presented. During the period of endogenous feeding (from the beginning of egg cleavage to transition of larvae to active feeding), lipids are spent with a greater rate than protein. After transition of larvae to exogenous feeding, an increase in the absolute concentration of proteins compared to lipids begins earlier and proceeds more intensively. The stage of irreversible starvation in larvae of gray mullet starts at a loss of 39–44% of protein and of the same amount of lipids of their initial content at the moment of hatching. Minimal protein losses over the period of embryonic development of gray mullet, as well as of protein and lipids towards the moment of termination of resorption of yolk sac, are observed in the range of temperatures of 21–25°C. Under conditions of low salinity (13–15‰) in the process of resorption of the yolk sac, lipids are spent more economically than at a higher salinity (17–19‰) at the expense of an increase in protein losses. Thus, a decrease in specific weight promoting the retention of buoyancy of larvae in water of low density is achieved.     

Temperature-dependent development rates of cod Gadus morhua eggs

Temperature development relationships were determined for batches of Irish Sea cod Gadus morhua eggs incubated in flow-through incubators. Hatching began 16·4 days after fertilization (DAF) at 6° C, 10·3 DAF at 8° C, 9·4 DAF at 10° C and 7·4 DAF at 12° C. Egg mortality increased at the higher temperatures, but survival was >80%. Results were compared with published data at four comparable stage end points: the end of blastula, the end of gastrula, the point of growth of the embryo completely surrounding the yolk and the point when 50% of the eggs were hatched. All the studies showed a curvilinear relationship between age at stage and temperature. There was a 12 day inter-study difference in time to 50% hatch at 2° C and 4 day difference at 10° C. There were no consistent trends that differentiated eastern v. western, or northern v. southern populations. A single model for cod egg incubation time from fertilization to 50% hatch was derived based on data from six cod populations, but it is recommended that individual stock relationships should be used where possible.     

Immersion heat treatments for inactivation of Salmonella enteritidis with intact eggs

The effects of water-bath immersion heat treatments on the inactivation of Salmonellaenteritidis within intact shell eggs were evaluated. Six pooled strains of Salm. enteritidis ( ca 3×10⁸ cfu, inoculated near the centre of the yolk) were completelyinactivated within 50–57·5 min at a bath temperature of 58°C and within 65–75min at 57°C (an 8·4 to 8·5- D process per egg). Following the initial 24 to35-min come-up period, semilogarithmic survivor curves obtained at 58 and 57°C yieldedapparent decimal reduction times ( D -values) of 4·5 and 6·0 min, respectively.Haugh unit values increased during heating, while yolk index and albumen pH values wereunaffected. Albumen clarity and functionality were affected by the thermal treatments; therefore,extended whip times would be required for meringue preparation using immersion-heated eggwhites. Immersion-heated shell eggs could provide Salmonella -free ingredients for thepreparation of a variety of minimally-cooked foods of interest to consumers and foodserviceoperators.     

Significance of temperature and preincubation temperature on survival of Listeriamonocytogenes at pH 4·8

Listeria monocytogenes is a food-borne pathogenic bacterium that can be found in softcheese. At the beginning of cheese ripening, the pH is about 4·85–4·90. The aimof this work was to study the influence of temperature, preincubation temperature (temperature atwhich the inoculum was cultivated) and initial bacterial concentration on the survival of L.monocytogenes (strain Scott A) at pH 4·8. It was demonstrated in an earlier study thatthese factors did influence growth kinetics. Survival studies of L. monocytogenes weredone in a laboratory broth simulating cheese composition. Four test temperatures (2, 6, 10 and14°C) and two preincubation temperatures were studied (30°C or the test temperature). Listeria monocytogenes (strain Scott A) was unable to grow at pH 4·8 under allconditions tested. The time for 10% survival was about 11 and 2 d, at 2°C with preincubationat 2°C and 30°C, respectively; 9 d at 6°C with preincubation at 6°C; 4 d at 6°Cwith preincubation at 30°C; and 1 d at 14°C with preincubation at 14°C or at 30°C.The results show that survival of L. monocytogenes (strain Scott A) at pH 4·8 is notdependent on initial bacterial concentration but on both the test and preincubation temperatures.     

The combined effect of sub-optimal temperature and sub-optimal pH on growth and toxin formation from spores of Clostridium botulinum

Low-acid foods (pH ≥ 4.5) are not sufficiently acidic to prevent growth of Clostridium botulinum in otherwise optimal conditions. The combination of sub-optimal pH and sub-optimal temperature may, however, result in a very significant reduction in the risk of growth of this bacterium compared with the risk in optimal conditions. The combined effect of incubation temperatures of 12° and 16°C and pH values between 5·2 and 5·5 on growth and toxin production from spores of Cl. botulinum during incubation for 28 d has been investigated. Growth and formation of toxin (type B) were detected only in medium at pH 5·5 and incubated at 16°C, corresponding to a probability of growth from a single spore within 14 d of 1·6 × 10^-5. The probability of growth in 28 d in the remaining conditions was <9 × 10^-6. After transfer of inoculated media from 12° to 30°C growth occurred at pH 5·2–5·5 within 19 d. After transfer of inoculated media from 12° to 20°C growth occurred at pH 5·5 and 5·4 but not at pH 5·3 or 5·2 in 40 d. Growth at pH 5·2–5·5 was accompanied by formation of toxin, in most cases of types A or B. In addition to the effect of sub-optimal temperature and pH, chelation of divalent metal ions by citrate may have contributed to inhibition.     

Thermal tolerance of a northern population of striped bass Morone saxatilis

Thermal tolerance of age 0+ year Shubenacadie River (Nova Scotia, Canada) striped bass Morone saxatilis juveniles (mean ± s . e . fork length, L _F, 19·2 ± 0·2 cm) acclimated in fresh water to six temperatures from 5 to 30° C was measured by both the incipient lethal technique (72 h assay), and the critical thermal method ( C _m). The lower incipient lethal temperature ranged from 2·4 to 11·3° C, and the upper incipient lethal temperature ( I _U) from 24·4 to 33·9° C. The area of thermal tolerance was 618° C². In a separate experiment, the I _U of large age 2+ year fish (34·4 ± 0·5 cm L _F) was 1·2 and 0·6° C lower ( P < 0·01) than smaller age 1+ year fish (21·8 ± 0·5 cm L _F) at acclimation temperatures of 16 and 23° C. Using the C _m, loss of equilibrium occurred at 27·4–37·7° C, loss of righting response at 28·1–38·4° C and onset of spasms at 28·5–38·8° C, depending on acclimation temperature. The linear regression slopes for these three responses were statistically similar (0·41; P > 0·05), but the intercepts differed (25·3, 26·0 and 26·5° C; P < 0·01). The thermal tolerance of this northern population appears to be broader than southern populations.     

Thermal effects on growth and time to starvation during the yolk-sac larval period of Atlantic mackerel Scomber scombrus L.

The effect of incubation temperature (8·6, 11·1, 13·2, 15·1 and 16·8° C) on north-east Atlantic mackerel Scomber scombrus development, growth and age at starvation during the yolk-sac larval period was investigated. Standard length at hatch was found to be inversely proportional to incubation temperatures within the natural thermal ranges of this species; it ranged from 3·76 mm at 11·1° C to 3·30 mm at 17·8° C. Following hatch, however, larval growth rate was positively related to temperature. Individual logistic models, as a function of temperature and age, were fitted to the development processes of gape, eye pigmentation, jaw mobility and yolk exhaustion. Thereafter, development was classified into different ordered stages and an extended continuation model was fitted to the multinomial ordered stage classification. In all cases, there was a difference of >23 h between the first and the last individual developing in certain stage. The probability of survival decreased with age and was inversely related to temperature. Yolk utilization varied from 4·5 to 8·6 days and individuals died between 7·9 and 12·2 days from 17·8 to 11·1° C. The study demonstrated the significant impact that temperature has on development, growth and survival rates, during the early life history.     

Fine structure of spermatozoa of Chondrostoma nasus and Rutilus meidingerii (Teleostei, Cyprinidae), as revealed by scanning and transmission electron microscopy

Fürböck, S., Patzner, R.A. and Lahnsteiner, F. 2008. Fine structure of spermatozoa of Chondrostoma nasus and Rutilus meidingerii (Teleostei, Cyprinidae), as revealed by scanning and transmission electron microscopy. — Acta Zoologica (Stockholm) 91 : 88–95
The fine structure of spermatozoa of sneep or nase, Chondrostoma nasus , and lake chub, Rutilus meidingerii , was investigated by means of scanning and transmission electron microscopy. The uniflagellate spermatozoa of C. nasus lacked an acrosome. The flagellum contained the conventional nine peripheral doublets and one central pair of microtubules (9 + 2 pattern) and lacked lateral fins. The uniflagellate spermatozoa of R. meidingerii were made up of a head, also without an acrosome. For both species the sperm tail was covered by a plasma membrane. The midpiece of C. nasus contained five or six mitochondria on average, vesicles and glycogen granules, whereas the midpiece of R. meidingerii had seven mitochondria of a spherical or ovoid shape. The centriolar complex was located caudolaterally with respect to the nucleus. In C. nasus , the centrioles were orientated at an angle of 125° to each other, whereas the centrioles of R. meidingerii were at an angle of 110°. The fine structure of C. nasus and R. meidingerii spermatozoa showed species-specific differences in the position of the proximal centriole relative to the distal centriole, the position and number of mitochondria, size of the head and the length of the flagellum. (Correction added on 11 June 2009, after first online publication: The word 'axoneme' was deleted from the sentence 'The flagellum contained the conventional nine peripheral doublets and one central pair of microtubules (9 + 2 pattern) axoneme and lacked lateral fins.')     

Early survival and growth in populations of grayling with recent common ancestors—field experiments

Among eight populations of grayling Thymallus thymallus that shared common ancestors 8–28 generations earlier, mean egg mortality ranged between 1·2 and 59·8%; mortality during yolk sac absorption was low (0middot;0–8middot;0%) and mean survival to swim-up was high (90–97%), with two exceptions (20% and 50%). Survival probabilities differed significantly among populations, even after statistically adjusting for size at swim-up and water depth, water velocity, gravel size and temperature. Development time from fertilization to first observed swim-up was significantly different among populations, ranging between 27 to 40 days, or 264 to 280 degree-days. Mean specific growth rates during the first external feeding period varied between 1·2 and 2·0% day^-1 among populations. Population-specific growth rates were independent of temperature. Rates of divergence were of the same order as in other salmonid studies showing rapid evolution. The phenotypic differences may be due partly to genetic differentiation among the populations.