The energetics of starvation and growth after refeeding in juveniles of three cyprinid species

Synopsis Experiments were conducted to monitor changes in body mass and metabolic energy expenditure before, during, and after periods of starvation in juveniles of three species of cyprinids: Leuciscus cephalus, Chalcalburnus chalcoides mento, and Scardinius erythrophthalmus. During the starvation period all fish lost weight at about the same rate and the total amount of oxygen consumed during an experimental period of 20 h was about 40% lower in the starved than in the fed groups. Upon refeeding, both mass specific maintenance; and routine rates of metabolism as well as relative growth rates increased rapidly, the peaks of these increases being directly proportional to the length of the starvation period. Maximum compensatory growth was observed after four weeks of starvation in C. chalcoides and S. erythrophthalmus, with relative growth rates reaching 30% d^-1 during the first measuring interval after refeeding. The pattern of time-dependent compensatory growth displayed by these fish is similar to the responses of a colonial hydroid in which the rate of catch-up growth increased with the amount of stress to which the animals had been exposed. The exact cost of compensatory growth cannot be calculated because oxygen consumption and growth were not measured simultaneously. However, on the basis of data and calculations reported by Wieser & Medgyesy (1990) it appears that compensatory growth, if fuelled by the metabolic power indicated by our measurements of oxygen consumption, would have to be about twice as efficient as normal growth in the related species Rutilus rutilus.     

Food consumption and growth of larvae and juveniles of three cyprinid species at different food levels

Synopsis The relationships between food availability, consumption and growth were analyzed from the onset of feeding to an age of 90 days in three cyprinid species. Fish were held at 20 ± 0.5° C and given two (three) constant rations of approximately 30, (40) or 100% dry body weight (dbw) ind^-1 day^-1. Food consisted of living zooplankton, the size of which correlated with fish size. At high food densities consumption rates decreased rapidly with fish size in all three species. At reduced rations, fish consumed most of the food offered until they were larger than 10 mg dbw. In all species and at each feeding level daily rations consumed increased allometrically with body size. Respiration rate, expressed as routine metabolic rate differed insignificantly between the three species. At high ration levels, growth rates of small bleak, Alburnus alburnus, were distinctly lower than those of roach, Rutilus rutilus, and blue bream, Abramis ballerus. At low food supply all three species grew at similar rates. Assimilation efficiency at low food conditions was approximately twice that of the well-fed groups. If the caloric equivalents of oxygen consumption as measured in well-fed fish are applied to fish fed at low rations their energy budgets do not balance. This indicates the limitations of fish larvae in the partitioning of energy for growth or activity at such conditions.     

Ontogenetic changes in the critical swimming speed of Gadus morhua (Atlantic cod) and Myoxocephalus scorpius (shorthorn sculpin) larvae and the role of temperature

Most studies on behavioural contributions to dispersal and recruitment during early life history stages of fishes have focused on coral reef species. For cold ocean environments, high variation in seasonal temperature and development times suggest that parallel studies on active behaviour are needed for cold-water species. Thus, we examined the critical swimming speed (U_crit) of marine fish larvae from 2 contrasting species: Gadus morhua (Atlantic cod) and Myoxocephalus scorpius (shorthorn sculpin), a pelagic and bottom spawner respectively. Within-species comparisons showed that sculpin reared at 6 °C had lower initial U_crit values, but a faster U_crit increase through development compared with 3 °C conspecifics, ultimately resulting in faster critical swimming speeds at metamorphosis (10.5 vs. 9.1 cm·s^− 1). In contrast, although cod larvae reared at 10 °C were faster swimmers at first feeding than 6 °C fish, temperature differences were absent after the first week. These results show that temperature influences the trajectory of larval critical swimming speed development, but that the relationship is species-specific. Although 6 °C sculpin and cod of similar length had equivalent U_crit values, the smaller size of cod at hatch (5.3 vs. 10.8 mm for sculpin) resulted in much lower age-specific U_crit values for cod. These data have significant implications for how swimming activity of the two species might affect dispersal, particularly in the first few weeks post-hatch. Overall, our data suggest that temperature during larval development influences the swimming capacity of cold-water marine fishes, and has important ramifications for biophysical models of dispersal.     

Swimming efficiency and the influence of morphology on swimming costs in fishes

Swimming performance is considered a main character determining survival in many aquatic animals. Body morphology highly influences the energetic costs and efficiency of swimming and sets general limits on a species capacity to use habitats and foods. For two cyprinid fishes with different morphological characteristics, carp (Cyprinus carpio L.) and roach (Rutilus rutilus (L.)), optimum swimming speeds (U _mc) as well as total and net costs of transport (COT, NCOT) were determined to evaluate differences in their swimming efficiency. Costs of transport and optimum speeds proved to be allometric functions of fish mass. NCOT was higher but U _mc was lower in carp, indicating a lower swimming efficiency compared to roach. The differences in swimming costs are attributed to the different ecological demands of the species and could partly be explained by their morphological characteristics. Body fineness ratios were used to quantify the influence of body shape on activity costs. This factor proved to be significantly different between the species, indicating a better streamlining in roach with values closer to the optimum body form for efficient swimming. Net swimming costs were directly related to fish morphology.     

Swimming response of goldfish,Carassius auratus,and the tetra,Hemigrammus caudovittatus,larvae to individual food items and patches

Synopsis Swimming speed and swimming path of goldfish and tetra larvae were studied in aquaria containing food patches composed of decapsulated cysts and immobilized nauplii of Artemia salina or sparsely distributed prey. The mean swimming speed of starved larvae in the medium without food was about four times higher than the speed of larvae feeding in a patch. Satiated larvae swam about 1.5 times slower than hungry fish. Consumption of single prey items by starved larvae caused the following sequence of swimming responses: handling pause (cessation of swimming), slow swimming in a restricted area, and fast swimming (approximately twice as fast as hungry larvae before encountering food) accompanied by a widening of the area searched (area increased searching). Mean swimming speed was constant over a broad range (10¹–10³ ind·1^–1 of food density, although at extreme (high or low) values of food density it depended on swimming responses of the predator. Frequency of visits to the different parts of the aquarium strongly depended on encounters of hungry fish with food particles or patches.     

Diet spectra and resource partitioning in the larvae and juveniles of three species and six cohorts of cyprinids from a subalpine lake

Summary Diet composition based on gut analyses was studied in larvae and juveniles belonging to six (out of eight) age groups (cohorts) of three species of cyprinids (Rutilus rutilus L., Leuciscus cephalus L., Scardinius erythrophthalmus L.) from a small meso-oligotrophic lake in Tyrol, Austria.A basic pattern of ontogenetic shifts of resource use is postulated for the first weeks after hatching, consisting of the sequence: phytoplankton-rotifers-crustaceans-chironomid larvae. However, there are several variations to this general theme.Diet overlap is of about the same magnitude between representatives of different species or different cohorts, and between members of schools belonging to one cohort. This points to the importance of random food selection in all larvae and juveniles during this phase of life.Prey size is a very poor predictor of food choice by young cyprinids, but there is greater similarity in diet between the larger juveniles than between the smaller larvae, irrespective of whether the fish compared represent different species, different cohorts or are members of homogeneous groups.The lack of correlation between prey size and predator size may be explained by assuming that out of a limited range of available prey size the fish always try to include in their diet also the largest items they are able to swallow. This would be a good strategy considering that growth rates are positively correlated with food size.One clearcut interspecific difference in resource use may be noted: The larvae of L. cephalus are distinguished from those of the other two species by the absence of rotifers and nauplii in their diet, and by their greater ability to handle both adult copepods and chironomid larvae.     

Respiration of individual honeybee larvae in relation to age and ambient temperature

The CO₂ production of individual larvae of Apis mellifera carnica, which were incubated within their cells at a natural air humidity of 60–80%, was determined by an open-flow gas analyzer in relation to larval age and ambient temperature. In larvae incubated at 34 °C the amount of CO₂ produced appeared to fall only moderately from 3.89±1.57 µl mg^–1 h^–1 in 0.5-day-old larvae to 2.98±0.57 µl mg^–1 h^–1 in 3.5-day-old larvae. The decline was steeper up to an age of 5.5 days (0.95±1.15 µl mg^–1 h^–1). Our measurements show that the respiration and energy turnover of larvae younger than about 80 h is considerably lower (up to 35%) than expected from extrapolations of data determined in older larvae. The temperature dependency of CO₂ production was determined in 3.5-day-old larvae, which were incubated at temperatures varying from 18 to 38 °C in steps of 4 °C. The larvae generated 0.48±0.03 µl mg^–1 h^–1 CO₂ at 18 °C, and 3.97±0.50 µl mg^–1 h^–1 CO₂ at 38 °C. The temperature-dependent respiration rate was fitted to a logistic curve. We found that the inflection point of this curve (32.5 °C) is below the normal brood nest temperature (33–36 °C). The average Q₁₀ was 3.13, which is higher than in freshly emerged resting honeybees but similar to adult bees. This strong temperature dependency enables the bees to speed up brood development by achieving high temperatures. On the other hand, the results suggest that the strong temperature dependency forces the bees to maintain thermal homeostasis of the brood nest to avoid delayed brood development during periods of low temperature.Abbreviations m body mass - R rate of development or respiration - T_I inflexion point of a logistic (sigmoid) curve - T_L lethal temperature - T_O temperature of optimum (maximum) developmentCommunicated by G. Heldmaier     

Ontogeny of prey attack behaviour in larvae and juveniles of three European cyprinids

Synopsis The ontogenetic change in time costs of prey attacks as well as the change in capture efficiency for representative cladoceran and cyclopoid prey was investigated in roach, Rutilus rutilus, bleak, Alburnus alburnus, and blue bream, Abramis ballerus. Video recordings were used for measuring the timing of attacks, whereas capture efficiencies were determined by direct observation. Decreases in the time cost of attacks reflect the decreasing importance of prey fixation during growth of the fish. No differences in capture efficiencies were found among the three cyprinid species, indicating that attack behaviour is unlikely to function as a basic mechanism leading to differences in prey selectivity among the investigated species. Increasing capture efficiency during early development may lead to increasing selectivity for cyclopoid prey in the field.     

Influence of temperature and food availability on the ecological energetics of the giant scallop Placopecten magellanicus

Summary Gonad output, reproductive effort and residual reproductive value are greater in scallops (Placopecten magellanicus) from shallow water, where conditions are more favourable, than in scallops from deep water. Variation between years in these fitness correlates is also greater in shallow water scallops. High reproductive effort is associated with a greater reproductive cost, although in general reproduction in this species appears to be restrained, and only in older individuals from shallow water is there evidence of reckless reproductive behaviour. Reproductive effort increases as the animal grows older, but residual reproductive value is a maximum at age 4 years, after which it decreases with age owing to greater mortality. Localities vary in their suitability for scallop growth and reproduction, and at one Newfoundland site conditions in shallow water (10 m) are better than those in deep water (31 m). Scallops from the former have a greater fitness than those from the latter. The energy costs of reproduction have implications for life history variability in P. magellanicus, although for a considerable part of its lifetime the scallop is able to maximise gamete production in response to environmental factors (especially the food supply) without trading off reproduction against growth or maintenance.     

Nesting,eggs and larvae of triggerfishes (Balistidae)

Synopsis Triggerfishes construct nests by excavating depressions in sand. Eggs are laid in an adhesive mass and anchored with rubble. A photograph of a newly-hatched embryo is included.     

The effect of oxygen tension on the production of Bacillus thuringiensis subsp. israelensis toxin active against Aedes aegypti larvae

An optimized batch production of Bacillus thuringiensis subsp. israelensis was made in a stirred Bioflo III reactor using a previously selected medium, and operating conditions in the range of 100–500 rev/min stirrer speeds and 0.2–1 air flow/culture medium volume/minute (v/v/m) aeration rates, including five combinations; at the end of fermentation, dry powders were recovered and evaluated against Aedes aegypti larvae at 0.05 mg/l. Later, the lethal concentration inducing 50% mortality (LC₅₀) was determined for the two most toxic powders. The bioinsecticide yields varied from 9.1 to 15.7 g/l and the total fermentation times ranged between 18 and 30.3 h. The toxicity varied for two powders much more than for the others. These were for combinations with 300 rev/min:1 v/v/m and 500 rev/min:0.6 v/v/m, giving mortality percentages of 47.2 and 59.7, with LC₅₀ values of 0.2675 and 0.0685 mg/l, respectively. A t test showed no significant difference. However, the larvicidal powder produced with 300 rev/min:1 v/v/m gave more variable toxicity than the powder obtained with 500 rev/min:0.6 v/v/m.     

Demersal schooling prior to settlement by larvae of the naked goby

Synopsis Field observations and collections indicate that the naked goby, Gobiosoma bosci, undergoes a near-bottom schooling phase prior to settlement. The size of these demersal larvae was intermediate between the sizes of larvae collected in plankton tows and of metamorphosed juveniles collected from the benthos. Two larvae that were captured unharmed quickly settled and metamorphosed. Otoliths of demersal larvae contained 20–41 daily increments. Most larvae were in schools made up of at least 25 individuals although single larvae were also seen. The dispersion pattern of demersal larvae was far more aggregated than that of recently settled juveniles indicating that larvae in schools probably do not settle to the benthos en masse.     

Effect of temperature on the oxygen consumption in the larvae of dineutes indicus aube (gyrinidae,coleoptera)

Oxygen uptake of the larvae of Dineutes indicus Aube has been measured at different temperatures. It has been observed that the oxygen uptake increases with the rise in the temperature but falls sharply after 34°C.The data obtained corresponds to a straight line when plotted on an Arrhenius graph.Q₁₀ values decrease with the increase in weight and it has been observed that the smallest individual has the highest Q₁₀ value. Nevertheless, the calculated energies of activation reported here apply only to the limited temperature range studied.     

Influence of proximal stimuli on swimming in the sea hare Aplysia brasiliana

Although the neurobiology and physiology of sea hares are extensively studied, comparatively little is known about their behaviour or ecology. Several species of sea hares swim, but the function of swimming is unclear. In this paper, we tested the hypotheses that swimming in Aplysia brasiliana serves to find food and mates, and to escape predators. Our data strongly support the hypothesis that swimming in A. brasiliana is related to feeding. Sea hares deprived of food overnight swam 12 times longer than ones that had been fed. When sea hares contacted food while swimming they invariably stopped, while those contacting a plastic algal mimic mostly continued to swim. Our experiments provided no evidence to support the hypothesis that swimming in sea hares is related to social behaviour. Sea hares deprived of copulatory mates for 3 days did not swim longer than ones held in copulating groups. Moreover, swimming sea hares never stopped swimming upon encountering a conspecific. Our experiments also supported the hypothesis that swimming in sea hares is related to predation. Sea hares stimulated with a standardised tail pinch and exposed to ink of conspecifics swam four times longer than control individuals, and tail-pinched sea hares that released ink swam five times longer than ones that did not release ink. However, because predators of adult sea hares are mostly lacking and because sea hares often swim spontaneously without predators being present, we conclude that swimming behaviour in A. brasiliana is primarily related to food-finding.     

黄蜻幼虫肠道真菌QTYC-51的鉴定及其除草活性成分

【目的】鉴定黄蜻幼虫肠道中具有除草活性的真菌,并分析其除草活性成分。【方法】通过形态学观察和分子生物学5.8S r DNA-ITS序列分析,明确菌株QTYC-51的分类地位。结合培养皿生物分析法测定菌株发酵液和单体化合物的除草活性,采用色谱方法从该菌乙酸乙酯粗提物中分离活性成分,并利用质谱和核磁共振谱鉴定活性物质。【结果】菌株QTYC-51被鉴定为拟盾壳霉属菌(Paraconiothyrium sp.),其发酵液对稗草和反枝苋幼根生长有较好的抑制作用,抑制率分别为76.9%和56.5%。从QTYC-51发酵产物中分离到5个单体化合物,分别为1,8-dihydroxyanthraquinone,1-hydroxy-10-methoxy-dibenz[b,e]oxepin-6,11-dione,hydroxyvertixanthone,globosuxanthone和1,3,6,8-tetrahydroxyanthraquinone。在供试浓度为100μg/m L时,化合物globosuxanthone对稗草和反枝苋幼根生长有明显的抑制作用,抑制率分别为94.1%和79.0%,与阳性对照2,4-二氯苯氧乙酸效果相当;化合物1-hydroxy-10-methoxy-dibenz[b,e]oxepin-6,11-dione具有较好的除草活性,对稗草和反枝苋幼根的生长抑制率分别为50.3%和58.6%。【结论】菌株QTYC-51具有开发为微生物源除草剂的潜能。     

Influence of the concentration of oxygen on the swimming path of Brachionus plicatilis (Rotifera)

Brachionus plicatilis females were maintained for > 24 hours in water where the concentration of oxygen was precisely controlled (spherical flasks with 6 mg l^–1 or < 0.5 mg l^–1; food = dead Tetraselmis sp.). Each female was randomly taken from one flask and quickly placed in an observation chamber containing the same experimental conditions. The swimming path was videotaped (5 minutes); then the size of the female was measured. The tape was analyzed by automatic tracking (25 x,y coordinates of the center of the animal, in a 512 × 512 pixels space). The swimming path was analyzed for 45 females in both treatments. The speed (mm s^–1 body length^–1) was calculated for all trajectories, or only for those segments where females swam in a horizontal plane. This relative speed significantly decreased when the concentration of oxygen was very low. There was a negative correlation between the linear speed and the angular speed. The spatial sinuosity (S of Bovet & Benhamou, 1988) was calculated. The trajectories were significantly more sinuous when the concentration of oxygen was very low. These results could explain the accumulation of some rotifers in the oxycline; rotifers may spend more time in very low concentrations of oxygen by slowing and by turning more.     

Effects of temperature,swimming speed and body mass on standard and active metabolic rate in vendace (<Emphasis Type="Italic">Coregonus albula</Emphasis>)

This study gives an integrated analysis of the effects of temperature, swimming speed and body mass on standard metabolism and aerobic swimming performance in vendace (Coregonus albula (L.)). The metabolic rate was investigated at 4, 8 and 15°C using one flow-through respirometer and two intermittent-flow swim tunnels. We found that the standard metabolic rate (SMR), which increased significantly with temperature, accounted for up to 2/3 of the total swimming costs at optimum speed (U _opt), although mean U _opt was high, ranging from 2.0 to 2.8 body lengths per second. Net swimming costs increased with swimming speed, but showed no clear trend with temperature. The influence of body mass on the metabolic rate varied with temperature and activity level resulting in scaling exponents (b) of 0.71–0.94. A multivariate regression analysis was performed to integrate the effects of temperature, speed and mass (AMR = 0.82M ^0.93 exp(0.07T) + 0.43M ^0.93 U ^2.03). The regression analysis showed that temperature affects standard but not net active metabolic costs in this species. Further, we conclude that a low speed exponent, high optimum speeds and high ratios of standard to activity costs suggest a remarkably efficient swimming performance in vendace.     

Growth, survival, and starvation resistance of Colorado squawfish larvae

Synopsis Growth and survival of Colorado squawfish, Ptychocheilus lucius, larvae under fluctuating 18, 22, and 26° C (5° C diel fluctuations) and constant 18, 22, 26° C, and 30° C temperature conditions and ration size corresponding to 12.5, 28,64,142, 320 brine shrimp nauplii fish^–1 day^–1 determined from laboratory experiments. Growth was optimal at 31° C and high at temperatures of 26° C to 30° C, at the highest food abundance. Lowest growth was under lowest food rations and highest temperatures. Growth of Colorado squawfish larvae declined substantially at temperatures < 22° C. Neither growth nor survival was significantly different between fluctuating or constant regimes. Survival of Colorado squawfish larvae was highest (95%) at 26.2° C and 235 nauplii fish^–1 day^–1 and high at temperatures of 20 to 30° C with food abundance > 180 nauplii fish^–1 day^–1. Survival was lowest when food abundance was low and temperature was high. Highest mortality occurred more than 20 days after experiments began and mortalities occurred sooner in higher than lower temperatures. Colorado squawfish larvae denied food for 5, 10, or 15 d after first feeding could have begun (6 d), had survival greater than 87 % which was equivalent to continuously fed controls. Survival of fish denied food for 17.5 d after feeding could have begun declined from 84% before feeding to 57% after feeding. Point of no return was estimated between 17.5 and 20 d. Colorado squawfish have relatively high starvation resistance. Low, stable flows that simulate natural hydrographs may enhance growth, survival, and recruitment of early life stages of Colorado squawfish by increasing water temperature and food abundance in regulated rivers of the Colorado River basin.     

Factors promoting the establishment of primary cultures of liver cells fromXenopus larvae

Summary The requirements for establishment and survival of primary cultures of larval amphibian liver cells were investigated.Plating efficiency was found to be enhanced by a collagen substrate, by diluted conditioned medium from an adultXenopus kidney cell line and by high initial cell densities. Plating efficiency was highest at a tonicity of 165–220 mOsm/kg. In cultures with undiluted conditioned medium the increase in cell number was 50–60% greater than in controls, where it was about 2-fold between day 3 and 6 of culture. Conditioned medium from theXenopus kidney cell line is assumed to contain at least two components, which are effective at different concentrations and stimulate either plating efficiency and cell aggregation or cell proliferation.In cultures without collagen sheets, cell flattening is greatly reduced, indicating that cell shape is also dependent upon the substrate.     

黄蜻幼虫肠道菌QTYC01除草活性代谢产物的分离和鉴定

【目的】从黄蜻幼虫肠道中分离出具有除草活性的真菌,并在其代谢产物中寻找具有除草活性的先导化合物。【方法】采用涂布平板法对黄蜻幼虫肠道共生真菌进行分离,通过形态学观察和5.8S r RNA序列分析初步确定目标菌株QTYC01的分类地位。利用离体的方法测定菌株发酵液及其乙酸乙酯提取物的除草活性以及粗提物对常见农作物的安全性;利用盆栽方法测定发酵液对稗草幼苗的活性。运用重结晶的方法对发酵产物进行分离、纯化,利用质谱和核磁共振谱分析鉴定出化合物的结构。【结果】菌株QTYC01被鉴定为Curvularia crepinii。离体活性测试发现QTYC01发酵液可显著抑制稗草和反枝苋幼根的生长,其抑制率分别可达95.0%和90.1%,并可使经喷施发酵液的稗草幼苗的受害率达到71.1%。发酵液的乙酸乙酯提取物对稗草和反枝苋幼根具有很好的抑制效果,在100μg/m L的浓度条件下,粗提物对稗草和反枝苋的抑制活性分别为56.8%和71.2%,且在该浓度条件下对一些常见农作物具有很好的安全性,其抑制率均低于32.6%。进一步从其乙酸乙酯提取物中分离得到化合物(5Z)-7-oxozeaenol,活性测试表明化合物具有较好的抑制反枝苋活性,其IC_(50)为4.8μg/m L。【结论】菌株QTYC01具有开发为新型微生物除草剂的潜力。