Oxygen uptake and heart rate in young Green turtles (Chelonia mydas)

Oxygen uptake. heart rate and breathing frequencies were monitored in yearling Green turtles. Routine fed animals used about 100μ O₂ g live turtle^-1 h^-1 at 25C; this value was not significantly affected by size or short term food deprivation. Starved turtle showed a doubling of oxygen uptake after a satiation meal and heightened uptake persisted for five days. Between 15 and 30C oxygen consumption increased with rising temperature; below 15C there was falling temperature. Vigorous activity increased oxygen uptake to two or three times thr routine fed levels.
Turtles swimming gently at 25C exhibited a heart rate of around 46–48 beats min^-1; this rose to 64–68 beats min^-1 during vigorous and continuous activity. Contrary to expectations profound bradycardia was not seen during diving; even during 10 min dives a rate of 25–28 beats min^-1 was sustained. Significantly lower heart rates were only seen in turtles which were apparently asleep.     

Growth and physiological changes during metamorphosis of Senegal sole reared in the laboratory

The metamorphosis of Solea senegalensis was studied in larvae reared at 20° C and fed four different feeding regimes. A, Artemia (4 nauplii ml⁻¹); B, Artemia (2 nauplii ml⁻¹); C, mixed diet (2 nauplii ml⁻¹ and 3 mg ml⁻¹ microencapsulated diet); and D, microencapsulated diet (3·7 mg ml⁻¹). Rotifers were also supplied in all cases during the first days of feeding. These feeding regimes supported different growth rates during the pre-metamorphosis period (regime A, G=0·376 day⁻¹; regime B, G=0·253 day⁻¹; regime C, G=0·254 day⁻¹; regime D, G=0·162 day⁻¹). Larvae started metamorphosis 9 days after hatching (DAH) when fed the regime A, 13 DAH with regime B, 11 DAH with regime C and 15 DAH with regime D. A minimum 5·6–5·9 mm L_T was required under all feeding regimes to initiate the metamorphosis. Eye translocation was completed when the larvae reached 8·6–8·7 mm L_T (regimes A, B and C), but only 7·3 mm L_T with regime D. 4·4–6·2 days were required to complete eye migration under the regimes A, B and C, and 18·3 days under the regime D. This transformation is concomitant with changes in body reserves, and with the pattern of some digestive enzymes.     

Locomotion in hatchling leatherback turtles Dermochelys coriacea

Hatchling leatherback turtles can only swim forwards, and employ synchronized beating of the forelimbs whether swimming slowly or quickly. The hind limbs make no contribution to propulsion. Effectively, the hatchlings have two swimming speeds; subsurface and fast (30 cm s^-1) or surfaced and slow (8 cm s^-1). Intermediate velocities are transitory; the hatchlings were never seen to rest without movement, nor did they exhibit gliding of the type seen in green turtles. During fast ('vigorous') swimming, power is developed on both the upstroke and downstroke of the limb cycle. During slow swimming, power is only developed during the upstroke—a consequence of the orientation of the axis of limb beat which is opposite in direction to that of cheloniid sea turtles. Terrestrial locomotion is laboured and features an unstable gait which involves simultaneous movement of all four limbs and forward overbalancing during each limb cycle.     

Particulate and filter feeding in threadfin shad, Dorosoma petenense, at different light intensities

Previous workers inferred from stomach analyses that threadfin shad ( Dorosoma petenense ) ate plankton by both filter and particulate feeding. These inferences were confirmed in this study by laboratory experiments in which both types of feeding were observed. Threadfin shad consumed relatively small food particles (≤ 0.39 mm) by filtration, while larger prey (7.5 mm) were eaten individually. The shad were able to filter feed on small foods (brine shrimp nauplii and phytoplankton) at all light intensities from 0 to 9 × 10¹ fL. These data indicate that under natural conditions shad can filter feed at any time of the 24 h period if food conditions are sufficient to trigger feeding. Filter feeding is probably induced by chemoreception rather than vision. The particulate feeding rate decreased as light intensity decreased, reaching a minimum between 9 × 10⁻⁴ and 9 × 10⁻⁵ fL. From these data it is inferred that particulate feeding is a visual process in this species, requiring intensities equivalent to bright moonlight or greater. Filter and particulate feeding abilities allow threadfin shad to consume most of the different types of plankton and to change their diet with seasonal changes in the composition of the plankton.     

Effect of food attractants on appetite and growth rate of gilthead bream, Sparus aurata L.

Appetite and growth rate were measured in Sparus aurata fed ad-libitum a basal diet supplemented with either a synthetic mixture of chemicals based upon the analysis of Mylilus edulis , muscle extract, or newly hatched Artemia saline nauplii. These components were tested for their feeding attraction potency, and were added to the basal diet at three concentrations each; 5, 10 and 20 g kg^-1 dry diet.
Appetite, which was defined as ad-libitum food intake, was significantly affected by the type and concentration of attractant. When the basal diet was supplemented with 10 or 20 g kg^-1 of the synthetic Mytilus edulis muscle extract, it was associated with significantly higher appetite than the basal diet only or the basal diet supplemented with any level of newly hatched Artemia salina nauplii. On the other hand, relative growth rate under the same conditions did not completely conform to the results with appetite. The difference between appetite and growth rate as criteria for the evaluation of food attractants is discussed.     

The accumulation of zinc by O-group plaice, Pleuronectes platessa (L.), from high concentrations in sea water and food

The uptake of zinc by young O-group plaice, Pleuronectes platessa was investigated at levels of high input from sea water and food ( Artemia nauplii). Zinc concentrations in the fish were strongly weight-specific and accumulation effects were distinguished by regression analysis. Sea water was estimated to contribute >10% of the total input up to levels corresponding to high environmental concentrations ( c. 0.1 μg Zn ml⁻¹) and food was the major source of zinc up to sea water concentrations of c. 0.6 μg Zn ml⁻¹. A high degree of regulation obtained along the food pathway to the fish although, in the system studied, most of this regulation was effected by the food organism. Regulation of food input explained the lack of variation in zinc levels previously observed in wild populations.     

In vitro analysis of intestinal absorption of cadmium and calcium in rainbow trout fed with calcium- and cadmium-supplemented diets

The protective effects of dietary Ca²⁺ supplementation against Cd accumulation in rainbow trout Oncorhynchus mykiss fed with Cd-contaminated food were evaluated in relation to chronic changes in intestinal absorption rates. The changes were measured ' in vitro '. The control diet contained c. 20 mg Ca²⁺ g⁻¹ food and 0·25 μg Cd g⁻¹ food; the experimental diets were supplemented with CaCO₃ and Cd(NO₃)₂·4H₂O to levels of 50 mg Ca²⁺ g⁻¹ food and 300 μg Cd g⁻¹ food, alone and in combination. The Ca²⁺ and Cd absorption rates were measured using radiotracers (⁴⁵Ca, ¹⁰⁹Cd) at total Ca²⁺ and Cd concentrations of 3·0 and 0·12 mmol l⁻¹, respectively in the intestinal saline. Chronically elevated dietary Cd caused a significant increase in Cd absorption rate by up to 10-fold at 30 days in the mid-intestine. The high Ca²⁺ diet prevented this up-regulation of Cd transport rate. Conversely, intestinal Ca²⁺ absorption was significantly increased by two- to five-fold by the Ca²⁺-supplemented diet at 30 days in both the mid- and posterior intestine, and this effect was eliminated when Cd was simultaneously elevated in the diet. Ca²⁺ and Cd probably interact at common pathways and transport mechanisms in the intestine, though independent pathways may also exist.     

Changes in in vitro heart performance in rainbow trout, Salmo gairdneri Richardson, infected with Apatemon gracilis (Digenea)

In vitro , perfused, isolated heart preparations were used to determine the effects of a parasitic infection on the performance of the heart. Increase in preload in the uninfected hearts produced an increase in output flow and power, resulting mainly from increase in stroke volume and little change in heart rate. The heart rate of infected hearts (14.3 beats min⁻¹) was slightly, but not significantly, lower than in controls (17.8 beats min⁻¹). The cardiac output of infected hearts was 20–40% of that of the healthy hearts. This reduction will, in turn, lead to reduced oxygen transport to the tissues, and so to a reduction in metabolic scope. It is therefore probable that fish carrying this infection will have low food intakes, low growth rates and low activity levels.     

Zooplankton feeding ecology: bacterivory by metazoan microzooplankton

Bacterivory by the rotifer Brachionus plicatilis Müller, nauplii and copepodites of the copepods Centropages Krøyer sp. and Acartia tonsa Dana, and the tintinnid Favella panamensis Kofoid & Campbell was examined using fluorescently labelled bacteria (FLB) and epifluorescence microscopy. FLB were < 1 μm in diameter, and were offered at environmental concentrations (1.47−9.08 × 10⁶ cells·ml⁻¹). FLB were visible within rotifers, nauplii, copepodites, and tintinnids, confirming ingestion. Rotifer clearance rates (32–418 μl·animal⁻¹·h⁻¹) exhibited no relation with FLB concentration. In some cases rates of clearance of FLB by rotifers were different with alternative phytoplankton food (Nanochloris Naumann sp.) than in replicates with FLB alone, whereas in other cases presence of alternative food exhibited no clear effects on rates of ingestion of FLB. Clearance rates for all six naupliar stages of A. tonsa nauplii (0–320 μl·animal⁻¹·h⁻¹) were stage-related, with higher rates by NIII-VI nauplii than NI-II nauplii. Nauplii had higher rates of clearance of FLB in the absence of alternative phytoplankton food (Isochrysis Parke sp.). Clearance rates of FLB by a single stage of Centropages sp. nauplii, A. tonsa CI copepodites and F. panamensis (each obtained at only a single food concentration of either 1.5 or 5.0 × 10⁶ cells·ml⁻¹) were within the range of 85–142 μl·animal⁻¹·h⁻¹. These ranges were similar to those of rotifers and A. tonsa nauplii. This is the first report of FLB ingestion by metazoan marine microzooplankton. Although rotifers and ciliates might be expected to ingest small particles such as FLB using ciliary induced feeding currents, the means by which nauplii and copepodites eat FLB is less clear. We propose that they may “eat” bacteria as they “drink” to osmoregulate.     

Hypometabolism in torpid goldsinny wrasse subjected to rapid reductions in seawater temperature

Goldsinny Ctenolabrus rupestris were subjected to rapid, environmentally realistic, reductions in temperature at 2° C increments from 10 to 4° C over a 3-day period in full-strength sea water. In separate experiments, oxygen uptake measurements and ultrasound recordings of heart rate and opercular motion were carried out at regular intervals over the same temperature regime. Mean oxygen uptake rates fell from 0.042 to 0.028 ml O₂ g⁻¹ h⁻¹ between 10 and 6° C respectively (Q₁₀=2.71). Between 6 and 4° C mean rates decreased from 0.028 to 0.008 ml O₂ g⁻¹ h⁻¹ (Q₁₀=542). Mean opercular motion and heart beat rates decreased from 49.5 and 60.3 beats min⁻¹ respectively at 10° C to 18.7 and 18.0 beats min⁻¹ respectively at 4° C. Most goldsinny subjected to 4° C were observed in a torpid state and would not react to external stimulation. Opercular motion was erratic at 4° C and would at times cease altogether for periods up to 1.3 min duration. Heart movement was diffcult to detect at 4° C and may also have ceased for prolonged periods. Q₁₀ values for opercular motion and heart beat rates recorded between 6 and 4° C were 6.39 and 24.52 respectively compared with values of 2.42 and 2.93 respectively recorded between 10 and 8° C. Such large depressions in metabolism appear not to have been reported previously for a marine fish species. No goldsinny mortalities were recorded at any temperature. The possibility that hypometabolic torpor is an adaptive strategy for goldsinny survival at low environmental temperatures is discussed.     

Effect of ration size on growth and gross conversion efficiency of young lemon sharks, Negaprion brevirostris

Young lemon sharks, Negaprion brevirostris , were kept under controlled conditions in an aquarium and fed blue runner, Caranx crysos , at different ration levels. The relationship between feeding rate and growth rate was best described by a von Bertalanffy growth curve, which predicted a maximum growth rate of 140 kJ kg⁻¹ day⁻¹ (0·66% b.w. day⁻¹), a maintenance ration of 199 kJ kg⁻¹ day⁻¹ (1·06% b.w. day⁻¹), and losses due to starvation of -236kJ kg⁻¹ day⁻¹ (1·11% b.w. day⁻¹). The relationship between gross conversion efficiency ( K ₁) and feeding rate was also examined. K₁ ranged from - 64 to 25% and did not drop at high ration levels. Activity levels of both starved sharks and sharks fed at maintenance were not significantly different (0·2 body lengths s⁻¹). K ₁ values generated from both laboratory and field data suggest that young lemon sharks can convert food to new tissue as efficiently as teleosts.     

Schooling affects growth in the three-spined stickleback, Gasterosteus aculeatus

Three-spined stickleback fry (mean length 20 mm, mean weight 14 mg) were reared for 14 days alone and in groups of six in a constant per capita water volume. The fish originated from two habitats (rock-pools, sea) of different predation pressure. The fry were fed nauplii of Artemia and commercial aquarium fish food ad libitum. Specific growth rates of solitary and schooling fry differed and were also affected by their origin. The specific growth rates of solitary fry from the sea averaged 1.0% day⁻¹ (length) and 6.0% day⁻¹ (weight) and those of solitary rock-pool fry 1.1 and 6.7%, respectively. For group-reared fish the corresponding values were 1.2% (length) and 6.6% (weight), and 1.3% (length) and 7.6% (weight). The finding that schooling sticklebacks grow faster than solitary ones implies that grouping enhances fitness in stickleback fry under the conditions of our experiments.     

Population growth rates of two closely related rotifer species: effects of food quantity, particle size, and nutritional quality

SUMMARY. 1. The relationship between population growth rates and the concentrations of several algal species was determined in laboratory experiments with the rotifers Brachionus rubens and B. calyciflorus .
2. The effects of food quantity were well described by a modified Monod model with a threshold for zero population growth. The model parameters depended on particle size and nutritional quality of the food algae. Differences between the rotifer species were significant and reflected their varying food-size preferences.
3. For each rotifer species, thresholds were lowest for algae in the most readily ingested size range. The lowest thresholds were 0.07–0.09 mgC 1⁻¹ with algae of about 5 μm equivalent spherical diameter (ESD) for B. rubens , and 0.19 mgC 1⁻¹ with algae of about 10 μm ESD for B. calyciflorus .
4. Maximal growth rates ( r _max) were slightly below 0.8 day⁻¹ for both rotifers with most algal species. The highest r _max values for both rotifers were observed when Cyclotella meneghiniana was provided as food. With this alga, B. calyciflorus had a significantly higher r_max (1.02 day⁻¹) than B. rubens (0.838 day⁻¹).
5. From a comparison of the relationship between growth rates and ingestion rates, Chlamydomonas reinhardii appeared to be of low nutritional quality for B. rubens .
6. Egg ratios were related to growth rate and were not influenced by the algal food used. Egg development times and average mortality rates were estimated from the relationship between egg ratio and growth rate. B. calyciflorus appeared to have a high average mortality rate (0.383 day⁻¹) compared to B. rubens (0.083 day⁻¹).     

Longevity of the freshwater anostracan Streptocephalus mackini (Crustacean: Anostraca) in relation to food (Chlorella vulgaris) concentration

SUMMARY 1. Temporary ponds are inhabited by a variety of invertebrates, of which anostracans are an important group. We studied the lifetables of male and female anostracan Streptocephalus mackini at 3 algal concentrations (0.5 × 10⁶, 1.0 × 10⁶ and 1.5 × 10⁶ cells mL⁻¹).
2. Regardless of sex, S. mackini showed better survivorship at lower food levels. The longest average lifespan observed was 85 ± 2 days for males fed Chlorella at 0.5 × 10⁶ cells mL⁻¹.
3. Both net reproductive rate and generation time decreased with increasing food level. The highest net reproductive rate was about 120 cysts per female. The longest generation time of about 40 days, observed at 0.5 × 10⁶ cells mL⁻¹, was more than three times that at 1.5 × 10⁶ cells mL⁻¹.
4. The rate of population increase ( r ) was nearly the same (0.31 ± 0.06) at high (1.5 × 10⁶ cells mL⁻¹) and intermediate (1.0 × 10⁶ cells mL⁻¹) food levels. The r -value at low food level (0.5 × 10⁶ cells mL⁻¹ of Chlorella ) was 0.20 ± 0.01 per day.     

Heart rate as an indicator of activity, metabolic rate, food intake and digestion in pike, Esox lucius

For pike in the laboratory, the relationship between heart rate (f_H) and oxygen consumption ( VO₂ , mg h⁻¹ standardized to a 500-g fish weight) can be described by a significant linear regression valid for heart rates below 55 beats min⁻¹. Heart rate increases during activity and feeding, accurately reflecting fluctuations in metabolic rate; so it can be used as a measure of metabolic rate in the field, using heart beat telemetry techniques. Post-prandial heart rates are elevated, and closely correlated with the calorific value of the food taken in the preceding meal. Meal size can be estimated from the heart rate record with an error of less than 10%.     

The arrangement of the heart chambers and associated blood vessels in the Devonian osteostracan Norselaspis glacialis. A reinterpretation based on recent studies of the circulatory system in lampreys

Food intake and digestion were investigated at four stages in the first 218 days of lactation in tammar wallabies ( Macropus eugenii ) carrying litters of one, and in non-lactating females as a control. This period of lactation in tammars, which includes the phase of exponential growth of the young, is comparable to gestation plus early lactation in ruminant placentals. Food and energy intakes by mothers remained at the non-lactating level while rate of growth of young was slow (up to Day 105 of lactation) but then rose as the growth rate of young increased, keeping pace with the predicted requirements for milk synthesis and export. There was no indication of the energy deficit seen in late gestation and early lactation in many herbivorous placental mammals. The gross efficiency of utilization of ME for growth of offspring was estimated as 13–15%, which is at least as high as values for placentals during gestation. The mean intake of metabolizable energy (ME) at 218 days was 603 kJ.kg^-0.75.d^-1, which represented 136% of ME intake by nonlactating females, or an increment of 159 kJ.kg^-0.75.d^-1. It was estimated that ME intake may rise to 773 kJ.kg^-0.75.d^-1 at peak lactation, which would be 174% of the non-lactating level or an increment of 329 kJ.kg^-0.75. d^-1. This allometrically-scaled increment is similar to values for some ruminants that use body reserves extensively to offset peak lactational food requirements. These and previously-reported trends suggest that ecologically comparable herbivorous marsupials and placentals utilize different physiological strategies to minimize demands on food resources during reproduction, but that both daily and overall demands can be similar.     

The swimming endurance of threespine sticklebacks, Gasterosteus aculeatus L., from the Afon Rheidol, Wales

The endurance of threespine sticklebacks, Gasterosteus aculeatus , swimming with pectoral fin locomotion at 20° C in a laboratory flume was measured. Each trial lasted a maximum of 480 min. At a speed of 4 body lengths per sec (L s⁻¹) all fish were still swimming at the end of the trial, but endurance decreased at higher speeds. At speeds of 5 or 6 L s⁻¹ (20–30 cm s⁻¹) a few fish still maintained labriform locomotion for the 480 min. However, at a speed of 7 L s⁻¹ all fish furled their pectoral fins and used body and caudal fin propulsion but fatigued rapidly. During sustained swimming, fish could cover distances of 6 km or more. No significant differences between males and females were found.     

Differing effects of suspended sediments on the performance of native and exotic Daphnia

1. Although large cladocerans are usually uncommon in large rivers, Daphnia lumholtzi (an exotic species in North America) is widespread and occasionally abundant. We collected zooplankton on the Illinois River (Illinois, U.S.A.) in 1995 and 1996 and found that the peak density of D. lumholtzi (25 L⁻¹) typically exceeded that of all native species combined. Maximum density occurred during warm periods (up to 27 °C) when concentrations of inorganic suspended sediments were high (>50 mg L⁻¹).
2. Using a life table experiment, we examined the effects of variation in suspended sediment (0 and 80 mg L⁻¹) and food (10⁴ and 10⁵ Ankistrodesmus cells mL⁻¹) on fitness of D. lumholtzi and the native Daphnia parvula. Daphnia lumholtzi had greater survivorship than D. parvula in most treatments and higher life-time fertility than D. parvula in all treatments. Both species achieved their fastest intrinsic rates of growth in treatments with high food, but their responses to suspended solids differed. The growth rate of D. lumholtzi in high food was slightly increased by higher turbidity, whereas that of D. parvula was depressed.
3. Results suggest that the ability of D. lumholtzi to tolerate suspended solids is an important factor contributing to its success in invading North American rivers.     

Nutritional estimate of populations of some wild free-ranging African ungulates in grassland (Nechisar national park, Ethiopia) in dry season

The amount and nutritive value of forage plants, diet composition, digestibility of dry matter and nutrients were recorded for zebra. Grant's gazelle, Swayne's hartebeest and hippopotamus in November-December 1991 Besides, daily egest of feces, the level of food and nutrient consumption, energy and protein requirements were recorded for zebra and Grant's gazelle The digestibility of pasture forage was determined as a ratio of lignin concentration in food to the concentration m feces (lignin tracer technique), a daily intake was calculated on the basis of the daily feces egest Protein percentage m the diet of zebra and hartebeest consuming dry parts of grasses did not exceed 5% Gazelle diet consists of green parts of plants and included 18% of protein The digestibility of dry matter in nonruminants (zebra, hippopotamus) was 40-45%, in hartebeest - 50%, in gazelle - 60% Due to the abundance of dry grasses (3 7 ton ha^-1) the daily food consumption of zebra was high - 7 2 kg ind^-1 (dry weight), the metabolizable energy intake (ME) being 51 MJ Adult gazelles consumed 15-25 kg ind^-1 of food and 14-24 MJ of ME The energy requirements of adult males and non-lactating females of zebras and gazelles (48 and 13 MJ respectively) were met, the energy balance berig negative for lactating animals The daily protein requirement was not met in zebra (392-704 g md^-1 vs 134 g ind^-1 of intake) and in lactating gazelles (250 g ind^-1 vs 197 g md^-1) Non-lactating gazelles consume sufficient amount of both energy and protein due to the high feeding selectivity of the species and thanks to the abundance of burnt areas with young green after-grass m the dry period     

Role of benthic insect feces in a Rocky Mountain stream: fecal production and support of consumer growth

The feces of stream insects may be a major component of fine particulate organic matter (FPOM) available to collector organisms. In Mink Creek, Idaho, winter defecation rates for 9 species ranged from 86 mg dry feces (g dry body wt)⁻¹ d⁻¹ (Ephemerella spinifera) to 154 mg g⁻¹ d⁻¹ (Paraleptophlebia heteronea) . Detailed studies of 3 species in summer revealed that rates were much greater than in winter and exhibited high between-individual variation (e.g., 695 ± 184.8 mg (g body wt)⁻¹ d⁻¹ for Baetis tricaudatus ). By combining measured and literature values, it is estimated that the benthic insect community egests approximately 3.4 kg feces m⁻² yr⁻¹. This value lies within the range of FPOM estimated to be derived from degradation of leaf litter input (0.7–9.9 kg m⁻² yr⁻¹, depending upon assimilation efficiency of the organisms).
Short-term winter growth experiments showed that, with two exceptions, collectors fed on fecal detritus will grow as well as on other food resources; relative growth rates depend upon the species. Because fecal detritus is abundant throughout the year, and is treated by many species as a source of food, it could be a major mechanism by which seasonal fluctuation in availability of allochthonous litter input is minimized and homeostasis of structure and function maintained.