Consumption and gut evacuation rate of laboratory‐reared spotted seatrout (Sciaenidae) larvae and juveniles

The temperature and mass dependence of maximum consumption rate was measured for larval and early juvenile spotted seatrout Cynoscion nebulosus . Maximum consumption ( C _MAX) estimates were obtained from feeding and gut evacuation experiments on larvae (3·8–19 mm standard length, L _S) at three temperatures (24, 28 and 32° C), and maximum consumption experiments on juveniles at three temperatures (20, 26 and 32° C). Feeding levels were determined for larvae fed live prey ( Brachionus plicatilis and Artemia salina ) ad libitum . The midgut and total evacuation times were estimated for fish feeding continuously and discontinuously using alternate meals of tagged and untagged live prey. Temperature and fish size had significant effects on gut evacuation and consumption. The gut evacuation time increased with increasing fish size, and decreased with increasing temperatures. Mass‐specific midgut contents increased for small larvae <0·156 mg dry mass ( M _D)( c . 4 mm L _S), and decreased for larger larvae and juveniles. Maximum consumption was modelled by fitting a polynomial function to a reduced dataset of individuals feeding at high levels. The C _MAX model predicted an initial increase in specific feeding rate from 70 to 155% M _D day⁻¹ for small larvae, before declining for larger larvae and juveniles.     

An in situ estimate of daily food consumption and alimentary canal evacuation rates of common carp, Cyprinus carpio L.

Daily food consumption and alimentary canal evacuation rates for common carp, Cyprinus carpio L., were estimated at 4-week intervals from April to October 1979. Both the rate of food evacuation and its relationship to temperature were described by an exponential function. Gut evacuation rates ranged from 6.0% of gut contents per hour at 9°C to 32.7% h⁻¹ at 26.5°C. Temperature accounted for 72–91% of the variation in gut evacuation rate among months. Daily food consumption varied from a low of 3.87 mg g⁻¹ of fish wet wt per day in April at 14°C (0.39% of wet body wt) to a high of 40.75 mg g⁻¹ (4.08%) in August at 26.5°C. Although a greater quantity of food appeared to be consumed during the morning in spring and early summer and a greater amount in the evening after July, there was not a statistically significant time of day for peak feeding activity. The field method described here seemed to provide reasonable estimates of food consumption compared with other field and laboratory studies.     

The effects of temperature and hyperoxia on arterial PO2 and acid-base status in Piaractus mesopotamicus

The effects of hyperoxia and change of temperature (range 20–30° C) on blood gases were studied in the teleost fish Piaractus mesopotamicus , native to several major river systems in Brazil. Large hyperoxia-induced increases of arterial P o₂ ( P _ao₂) indicated that true branchial blood shunts are negligible in relation to total gill perfusion. This implies that blood gases will be influenced by ventilation rather than by shunts. Acute variations of temperature ( t ) were accompanied by changes of arterial blood pH (on the average Δ p H_aΔt⁻¹ of — 0·015 units °C⁻¹), due mainly to alterations of P _aco₂: 2·4 mmHg at 20° C, 5·0 mmHg at 30° C. Concomitantly, P _ao₂ declined from 116 mmHg (20° C) to 89 mmHg (30° C). The data suggest that temperature-induced changes of acid-base status depend mainly on gill ventilation and that the decrease of P _ao₂ with higher temperature is a result of this regulation.     

Gut evacuation of walleye pollock larvae in response to feeding conditions

Gut residence times of first-feeding walleye pollock larvae were measured at 6°C in continuous and discontinuous feeding regimes. Larvae fed tagged copepod prey evacuated their guts more quickly in continuous feeding as compared to the discontinuous feeding treatment. The mean gut residence time was estimated to be 5.0 h for larvae feeding continuously. Gut evacuation by larvae fed tagged prey and then isolated without food (discontinuous treatment) was slower and more variable, with an estimated gut residence time exceeding 8.0 h. Field and laboratory observations suggest that the larval fish gut may be modeled as an intermittent plug-flow reactor (PFR) in response to diel feeding patterns. The cyclical nature of gut dynamics has implications for gut content analyses and the estimation of daily food rations.     

Laboratory growth of larval lampreys (Lampetra (Entosphenus) tridentata Richardson) at different food concentrations and animal densities

Lampreys are important research animals. This study investigates some of the Parameters important for culturing the Suspension feeding larvae: food concentration, temperature and crowding. Large larvae ( Lampetra ( Entosphenus ) tridentata Richardson) were used, weigh-ing from l·5 to 3·0 g (wet). Two food types were employed: suspended yeast cells ( Saccharo-myces cerevisiae , 0–20 mg1 – (dry), or, in a few tests, a fine particulate fish food, Liquifry® (Interpet LTD, 0–13 mg l^-1). At both 14 and 4°C, yeast could sustain weight increases comparable to those in nature: >6% month^-1 for up to 6 months, the duration of the study. In a single lest, a vitamin Supplement failed to improve growth on yeast. Growth-was fastest at 14°C (+41% month^-1, max. weight increase), although also substantial at 4°C (+11% month^-1, max). Growth could not be sustained at 20°C, due perhaps to difficulty in removing products of food decay from the aquaria. Food level being constant, growth rate varied inversely with animal density. It is suggested that larval lampreys release a growth-inhibiting substance into the sand which they inhabit. Overall, the best growth was obtained at 14° C, with <0·05g of animal (wet weight) – aquarium water and average daily yeast concentrations between 4 and 13 mg –. Liquifry was associated with lowered growth rates when present continually above 4 mg (dry weight) – (14° C), although growth did occur at lower concentrations.     

Influence of ambient and thoracic temperatures upon sexual behaviour of the gypsy moth, Lymantria dispar

ABSTRACT. In an ambient temperature ( T _a) range of 18–28°C, thoracic temperatures ( T _th) of individual male Lymantria dispar (L.), caught at flight in the field, ranged from 21 to 36.5°C, with a correlation coefficient of 0.63 between T _th and ambient temperature ( T _a). Ambient temperature (and insolation) altered the insect's body temperature and the probabilities, latencies, and durations of preflight responses to pheromone. In a wind tunnel at 16 and 20°C, quiescent males exposed to pheromone raised their T _th by sustained wing fanning from 17 and 21°C, respectively, to c. 24°C before takeoff. At 24 and 28°C ambient, T _th rose by takeoff to 28 and 31°C, respectively. The latencies of male wing fanning in response to pheromone decreased from 1.44 min at 16°C ambient, to 0.58 min at 20°C, to 0.26 min at 24°C, and to 0.16min at 28°C. The components of behaviour (antennal twitch, body jerk, step and wing tremor) that occurred between quiescence and wing fanning were more frequent at ambients of 16 and 20°C than at 24 and 28°C.     

Effects of development, temperature and salinity on metabolism in eggs and yolk-sac larvae of milkfish, Chanos chanos (Forsskål)

Oxygen uptake rates and yolk-inclusive dry weiGhts were measured during the egg and yolk-sac larval stages of milkfish, Chanos chanos (Forsskal). Oxygen uptake by eggs and yolk-sac larvae was measured to assess the effects of four salinities (20,25,30,35 ppt) at 28°C. The effects of three temperatures (23,28,33°C) on oxygen uptake by yolk-sac larvae were determined at a salinity of 35 ppt. Dry weights were measured throughout embryonic development at 28°C and the yolk-sac stage at 23.28 and 33°C.
Oxygen uptake rates of eggs increased more than fivefold during embryogenesis (0.07±0.03 to 0.40 ± 03 μl O₂ egg ⁻¹ h ⁻¹;blastula to prehatch stage). Larval oxygen uptake did not change with age but was affected by rearing temperature (0.33 ± 0.08, 0.44 ± 0.07 and 0.63 ± 0.13 μl O₂ larva ⁻¹ h⁻¹ at 23, 28 and 33°C, respectively; Q₁₀= 1.93). Acute temperature changes from 28 to 33°C caused significant increases in oxygen uptake by embryos (Q ₁₀= 1.69–3.58) and yolk-sac larvae (Q ₁₀=2.55). Salinity did not affect metabolic rates.
Dry weight of eggs incubated at 28°C decreased 13% from fertilization to hatching. Incubation temperatures from 23–33°C did not affect dry weights at hatching. Rearing temperatures significantly affected the rate of larval yolk absorption (Q ₁₀= 2.25).     

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.     

Gastric evacuation in horse mackerel. I. The effects of meal size, temperature and predator weight

Gastric evacuation experiments were performed on horse mackerel Trachurus trachurus. A nearly full matrix experimental design with respect to the variables predator weight (<10–400 g) meal size (up to 7·8% body weight) and temperature (10–20°) was covered with 0-group smelt Osmerus eperlanus as prey. A general evacuation model without meal size as a variable was fitted to the data on wet weights as well as on dry weights by means of non-linear regression technique. Two methods of data transformation, relative data and square root transformation, were applied to improve variance homogeneity. The most reliable model fit was achieved on dry weight data applying the square root transformation technique: where S_t=stomach content (g wet weight) at time t after ingestion, S₀=the initial meal size, W =predator (g wet weight), and T =temperature. The estimated coefficient of the exponential temperature function, δ=00·032, corresponds to a Q ₁₀ value of 1·4 which is outstandingly low in comparison with results on other species. However additional experiments to determine maximum daily food rations indicated that appetite in contrast to gastric evacuation is strongly temperature dependent.     

Respiratory Q10 of marigold (Tagetes patula) in response to long-term temperature differences and its relationship to growth and maintenance respiration

Acclimation of respiration to temperature is not well understood. To determine whether whole plant respiration responses to long-term temperature treatments can be described using the Q₁₀ concept, the CO₂ exchange rate of marigolds ( Tagetes patula L. 'Queen Sophia'), grown at 20°C or 30°C, was measured for 62 days. When plants of the same age were compared, plants grown at 20°C consistently had a higher specific respiration (R_spc) than plants grown at 30°C (long-term Q₁₀= 0.71–0.97). This was due to a combination of greater dry mass at 30°C and a decrease in R_spc with increasing mass. When plants of the same dry mass were compared, the long-term Q₁₀ was 1.35–1.55; i.e. R_spc was higher at 30°C than at 20°C. Whole plant respiration could be accurately described by dividing respiration into growth and maintenance components. The maintenance respiration coefficient was higher at 30°C than at 20°C, while the growth respiration coefficient was lower at 30°C, partly because of temperature-dependent changes in plant composition. These results suggest difficulties with interpreting temperature effects on whole plant respiration, because conclusions depend greatly on whether plants of the same age or mass are compared. These difficulties can be minimized by describing whole plant respiration on the basis of growth and maintenance components.     

Growth and maintenance respiratory costs of cucumber fruits as affected by temperature, and ontogeny and size of the fruits

The rates of dry weight increase and respiration of fruits were measured throughout fruit ontogeny at 20, 25 and 30°C in cucumber ( Cucumis sativus L. cv. Corona). By maintaining one or five fruits per plant, which strongly affected fruit dry weight but not ontogeny, the effects of fruit size and ontogeny on respiration could be studied separately. The respiration rate per fruit followed a sigmoid curve during fruit ontogeny, while the specific respiration rate (respiration rate per unit dry weight) declined with time after anthesis. The specific respiration rate was almost linearly related to the relative growth rate. The specific respiratory costs for both growth and maintenance were highest in young fruits, but were not affected by fruit size. The average specific respiratory costs for growth and maintenance at 25°C were 3.3–3.9 mmol CO₂ g⁻¹ and 4.0 nmol CO₂ g⁻¹ s⁻¹, respectively. An increase in temperature had no effect on the specific respiratory costs for growth, while the costs for maintenance increased with a Q₁₀ of about 2. The costs for growth agreed reasonably well with theoretical estimates based on the chemical composition of the fruits but not with estimates based on only the carbon and ash content. The respiratory losses as a fraction of the total carbon requirement of a fruit changed during fruit ontogeny, but were independent of temperature and were similar for slow- and fast-growing fruits. The cumulative respiratory losses accounted for 13–15% of the total carbon requirement.     

Insights into torpor and behavioural thermoregulation of the endangered Juliana's golden mole

The cryptic, subterranean ways of golden moles (Chrysochloridae) hamper studies of their biology in the field. Ten species appear on the IUCN red list, but the dearth of information available for most inhibits effective conservation planning. New techniques are consequently required to further our understanding and facilitate informed conservation management decisions. We studied the endangered Juliana's golden mole Neamblysomus julianae and aimed to evaluate the feasibility of using implantable temperature sensing transmitters to remotely acquire physiological and behavioural data. We also aimed to assess potential body temperature ( T _b) fluctuations in relation to ambient soil temperature ( T _a) in order to assess the potential use of torpor. Hourly observations revealed that T _b was remarkably changeable, ranging from 27 to 33 °C. In several instances T _b declined during periods of low T _a. Such 'shallow torpor' may result in a daily energy saving of c . 20%. Behavioural thermoregulation was used during periods of high T _a by selecting cooler microclimates, while passive heating was used to raise T _b early morning when T _a was increasing. In contrast to anecdotal reports of nocturnal patterns of activity, our results suggest that activity is flexible, being primarily dependent on T _a. These results exemplify how behavioural patterns and microclimatic conditions can be examined in this and other subterranean mammal species, the results of which can be used in the urgently required conservation planning of endangered Chrysochlorid species.     

Roles of endothermy in niche differentiation for ball-rolling dung beetles (Coleoptera: Scarabaeidae) along an altitudinal gradient

Abstract.  1. An analysis of whether niche differentiation in ball-rolling dung beetles can be explained by the way in which they regulate their body temperature was conducted.
2.  A priori assumptions were: (i) if thermoregulation affects niche partitioning, sympatric species must have different endothermic strategies that minimise encounters; or, alternatively (ii) if two co-occurring species show the same thermoregulation pattern and their flight periods overlap, they might be avoiding competition by exhibiting different resource preferences or different food relocation behaviour.
3. The ball-rolling dung beetles studied showed a hierarchical structure based on the species' endothermic capacity, measured as temperature excess [ T _ex= difference between body temperature ( T _b) and ambient temperature ( T _a)]. Those with a high T _ex (10–15 °C) were located exclusively at altitudes >1000 m a.s.l. On the coastal plains, species with a high T _ex were restricted to flying at night when the T _a was lower. Species with a lower T _ex (less than 10 °C higher than T _a) were found in the coastal plains zone.
4. Where there was sympatry with similar trophic habits, the species involved showed very different thermal niches, and where there was significant overlap of thermal niches between sympatric species, trophic habits of species were very different.
5. The results suggest that it is possible to use the concept of the thermal niche as a tool to explain interspecific interactions and the spatial distribution of species.     

Consumption, growth and evacuation in the Pacific cod, Gadus macrocephalus

Growth of Pacific cod was related to energy consumption (cal g⁻¹ day⁻¹) and was well described by linear equations. Maintenance ration was 11 and 12 cal g⁻¹ day⁻¹ at 4.5 and 6.5° C, respectively. Cod between 200 and 5000 g had similar growth rates when growth was expressed as a function of consumption (cal g⁻¹ day⁻¹). Laboratory consumption of food averaged 0.9 and 1.3% body weight per day at 4.5 and 6.5° C, respectively. At these temperatures growth was 0.34–0.38% body weight day⁻¹.
Maximum stomach volumes equated to approximately 4.7% of body weight with shrimp as prey. At this meal size Pacific cod did not feed the next day. A multiple meal evacuation experiment was used to verify the consumption estimates. A return-to-hunger estimate of the meal size evacuated was 1.5% body weight day⁻¹ at 6.5° C, similar to the 1.3% consumption estimate. For Pacific cod fed a single meal of 1% body weight the estimated instantaneous evacuation rate was 0.63 body weight day⁻¹ at 6.5° C. Meal size markedly affected the evacuation rate.
Measured consumption and growth rates are similar to those of Atlantic cod, Gadus morhua .     

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.     

Daily ration and prey size of juvenile piscivore Japanese Spanish mackerel

Daily ration of juvenile Japanese Spanish mackerel Scomberomorus niphonius (32·1–33·1 mm standard length, L _S) was estimated at three temperatures (18·6, 19·5 and 21·2° C) in the laboratory. Gastric evacuation rate ranged between 0·398 (18·6° C) and 0·431 (21·2° C). Diel change in instantaneous consumption rate indicated that juvenile Japanese Spanish mackerel are daylight feeders. The estimated values of the daily ration ranged between 66·1%(18·6° C) and 82·6%(21·2° C) of body mass. These per cent values of daily ration were converted to daily consumption in mg (28 mg at 18·6° C to 34 mg at 21·2° C) using the mean dry body mass of juvenile Japanese Spanish mackerel of 30 mm (42·1 mg). Stomach content analysis of wild specimens collected in the Seto Inland Sea, south‐western Japan, revealed that the majority of wild Japanese Spanish mackerel larvae and juveniles ingested fish larvae with a body size >50% of the predator L _S. Based on the predator‐prey size relationship, the daily consumption of a Japanese Spanish mackerel juvenile of 30 mm was equivalent to 5·1 (18·6° C) to 6·4 (21·2° C) Japanese anchovy Engraulis japonicus larvae which was the dominant prey organism in stomachs of the wild Japanese Spanish mackerel.     

Biology and life table parameters of the mushroom pest, Pediculaster fletchmanni （Acari： Siteroptidae）, at three constant temperatures

This paper is concerned with the bionomics and demography of Pediculaster fletchmanni Wicht （Acari： Siteroptidae） under controlled conditions （20 ± l, 22 ± 1 and 25 ± 1℃, 70% ± 5% relative humidity and a photoperiod of 16L ： 8D hours）. Glass Petri dishes inoculated with Trichoderma sp. mycelia were used as substrate and food source. The mean developmental time of the egg and the active larva did not differ significantly at the various constant temperatures, but these periods were significantly different for the quiescent larval stage. The preoviposition period ranged from 2.3 to 2.8 days, the ovipositional period increased with temperature increase, and all females died immediately after oviposition. The development of active larvae was the fastest of all life stages. The developmental threshold ranged between 5.25-14.22℃ the highest value being observed for the quiescent larval development. For immature development required 89.29 degree-days. Values of rm （intrinsic rate of increase） were 0.229, 0.398 and 0.386 for 20, 22 and 25℃ respectively. Finite rates of increase （λ） increased along with increasing temperature from 20-25℃ consequently the population doubling time （D） and mean generation time （T） showed significant differences with increasing temperature.     

Correlation between digestion rate and feeding frequency in the stomachless teleost, Blennius pholis L.

Foregut emptying in Blennius pholis at 16–18°C is exponential ( S_t = S_o e^-Rt; R=0.006 when t is in min and s in mg dry weight). In consequence, the time for the foregut to empty completely varies in proportion to ln (meal size) in a chosen size of fish or to ln (body weight) in different sized fish fed to the same relative amount (% body weight). Appetite returns rapidly in comparison with other species (4–15 h for fish of 0.5−30 g) and, because of the tidal constraints imposed on this littoral fish, voluntarily ingested meals are large (14–9% body weight depending on fish size). Studies on digestion in small, stomachless fish are not adequately made using X-radiography and must be supported by sequential gut samples after a meal.     

Redistribution of Imipramine from Regions of the Brain Under the Influence of Circulating Specific Antibodies

Abstract: The kinetics of brain-to-blood redistribution of imipramine (IMI) was assessed in nine brain regions of control rats and rats given anti-tricyclic antidepressant (anti-TCA) antibody. Two antibodies were given intravenously 6 min after intravenous [³H]IMI (1 nmol/kg). One was a murine monoclonal IgG₁ ( K _a = 3.8 × 10⁷ M ⁻¹) at an IgG/IMI molar ratio of 1,000 (IgG1,000), and the other was a sheep polyclonal IgG (TAb; K _a = 1.3 × 10¹⁰ M ⁻¹) at IgG/IMI molar ratios of 1, 10, and 100 (TAb1, TAb10, and TAb100). In the control rats, IMI was rapidly taken up by the brain ( C _max at 5 min) with no significant differences among the brain regions (4.1 ± 0.4 to 5.4 ± 0.6 pmol/g), and brain IMI then declined monoexponentially with a half-life of 44.2 min (cerebellum) to 77.3 min (hippocampus). The greatest IMI content was in the frontal cortex and the lowest in the cerebellum. The antibodies (except TAb1) stimulated the extent and rate of IMI redistribution from all the brain regions depending on the immunoreactive capacity ( NK _a) of the antibody. The antibody with the highest NK _a (TAb100) had the greatest effect. The fraction of IMI removed from the brain was 58–74%, and the redistribution half-life was 7.9–15.6 min; the mean residence time was reduced by 66–75% (11.8–23.9 min). These results demonstrate that circulating anti-TCA IgG rapidly and reliably removes IMI from the brain, indicating that immunotoxicotherapy could be an efficient procedure for accelerating the removal of TCA from the brain.     

A radiographic estimation of the effect of temperature on gastric emptying time in Sarotherodon niloticus (L) × S. aureus (Steindachner) hybrids

A radiographic technique was used to determine temperature effects on gastric emptying time in S. niloticus/aureus hybrids. Stomach evacuation times for 30 g fish fed 3% of their body weight were 8.5 h at 30° C, 10.8 h at 25° C and 16.4 h at 20° C. Hence, there was a negative correlation between stomach evacuation time and temperature. The Q ₁₀ between 20 and 30° C was calculated to be 1.92. Similar relationships were found for intestinal evacuation and total evacuation.
The data were used to estimate maximum daily feed intake levels of fish within the size range studied. Levels for 30 g fish were 8.5% body weight at 30° C, 6.6% at 25° C and 4.4% at 20° C. However, the optimum feeding regime should take account of the feeding behaviour of the animals.