Weight Specific Rate Research Articles

Metabolic balance of a marine neritic copepod under chronic and acute warming scenarios

We investigated the impact of sublethal thermal stress on physiological rates of the copepod Paracartia grani, and explored the influence of previous thermal history on this response. The copepods, originally reared at 19 °C, were raised for 23 generations at 22 °C and 25 °C, and posteriorly exposed for 7-d to stress temperature (28 °C). The copepod acclimation capacity was assessed by comparing metabolic balance at 28 °C against their respective rearing temperatures. There was an inverse relationship between rearing temperature and body size and carbon content for the reared copepod lines. Weight-specific rates, except respiration, increased with rearing temperature, whereas per capita rate differences were levelled, partly due to differences in copepod size. Heat stress impact, as weight-specific rate fold-change, appeared inversely related to rearing temperature. Carbon gains were overall sufficient and slightly in excess to account for carbon losses. Gross-growth efficiency across warming scenarios was conserved, emphasizing resilience to environmental change. Our findings underscore the importance of considering the species' thermal history when predicting the response of copepod populations to climate change associated phenomena such as gradual slow ocean warming or heatwave events.

Adaptive responses in uteroplacental metabolism and fetoplacental nutrient shuttling and sensing during placental insufficiency.

Glucose, lactate, and amino acids are major fetal nutrients. During placental insufficiency-induced intrauterine growth restriction (PI-IUGR), uteroplacental weight-specific oxygen consumption rates are maintained, yet fetal glucose and amino acid supply is decreased and fetal lactate concentrations are increased. We hypothesized that uteroplacental metabolism adapts to PI-IUGR by altering nutrient allocation to maintain oxidative metabolism. Here, we measured nutrient flux rates, with a focus on nutrients shuttled between the placenta and fetus (lactate-pyruvate, glutamine-glutamate, and glycine-serine) in a sheep model of PI-IUGR. PI-IUGR fetuses weighed 40% less and had decreased oxygen, glucose, and amino acid concentrations and increased lactate and pyruvate versus control (CON) fetuses. Uteroplacental weight-specific rates of oxygen, glucose, lactate, and pyruvate uptake were similar. In PI-IUGR, fetal glucose uptake was decreased and pyruvate output was increased. In PI-IUGR placental tissue, pyruvate dehydrogenase (PDH) phosphorylation was decreased and PDH activity was increased. Uteroplacental glutamine output to the fetus and expression of genes regulating glutamine-glutamate metabolism were lower in PI-IUGR. Fetal glycine uptake was lower in PI-IUGR, with no differences in uteroplacental glycine or serine flux. These results suggest increased placental utilization of pyruvate from the fetus, without higher maternal glucose utilization, and lower fetoplacental amino acid shuttling during PI-IUGR. Mechanistically, AMP-activated protein kinase (AMPK) activation was higher and associated with thiobarbituric acid-reactive substances (TBARS) content, a marker of oxidative stress, and PDH activity in the PI-IUGR placenta, supporting a potential link between oxidative stress, AMPK, and pyruvate utilization. These differences in fetoplacental nutrient sensing and shuttling may represent adaptive strategies enabling the placenta to maintain oxidative metabolism.NEW & NOTEWORTHY These results suggest increased placental utilization of pyruvate from the fetus, without higher maternal glucose uptake, and lower amino acid shuttling in the placental insufficiency-induced intrauterine growth restriction (PI-IUGR) placenta. AMPK activation was associated with oxidative stress and PDH activity, supporting a putative link between oxidative stress, AMPK, and pyruvate utilization. These differences in fetoplacental nutrient sensing and shuttling may represent adaptive strategies enabling the placenta to maintain oxidative metabolism at the expense of fetal growth.

Oxygen consumption rates and respiratory carbon losses in three species of copepods(Acartia clausi, Calanus helgolandicus and Limnocalanus macrurus) during starvation

Calanoid copepods with different life cycle strategies demonstrate varied velocity in the utilization of energy resources during starvation. This study analyzes the influence of multiday starvation on the rate of total, basal and active energy metabolism in adult females of two Marmara Sea and one Baltic Sea species of copepods; epiplanktonic Acartia clausi unable to accumulate lipid reserves and mesoplanktonic Calanus helgolandicus with minor lipid reserves in the oil sac (approximately 7% of body volume) and the Baltic Sea copepod Limnocalanus macrurus in quasi-diapausing state with large lipid reserves in the oil sac (approximately 19% of body volume). Initially, total weight specific respiration rates were about 0.12 μg C per μg C body weight per day (d$^{-1}$) for both Marmara Sea species at 20 °C and 0.079 d$^{-1}$ in the Baltic L. macrurus at 14 °C, decreasing significantly by 1.6-2.5 times with starvation, while basal metabolic rates, measured in the same anesthetized individuals, was nearly constant during starvation. In this regard, the active metabolic rates, defined as the difference between the respiration rate of active and anesthetized individuals, decreased during starvation by 1.7 times in C. helgolandicus and by 4.7 and 6 times in A. clausi and L. macrurus, respectively. In A. clausi and C. helgolandicus with minimal lipid reserves, total daily energy expenditure (5.1% of initial body carbon content) was twice as high as in L. macrurus (2.2% of initial body carbon content daily), which has a large oil sac. Overall, the trend demonstrates that despite different energy reserves, a decrease in the total energy metabolism in copepods occurs due to a reduction in energy expenditure for locomotor activity.

Diets and Seasonal Ingestion Rates of Aurelia coerulea (Cnidaria: Scyphozoa) Polyps by in situ Feeding Experiments in Jiaozhou Bay, China

The benthic scyphopolyp population is an important stage in the scyphozoan lifecycle. Nevertheless, few studies have detailed the natural feeding and quantified the energy flux of polyps based on field research. To better understand the scyphopolyp natural diet and seasonal variation patterns in the ingestion rate, in situ feeding experiments were conducted on Aurelia coerulea polyps in Jiaozhou Bay, China from August 2018 to April 2019. The diet of A. coerulea polyps was determined by gut content analysis. Digestion rates were also measured. Ingestion rates, based on the gut contents and digestion rates, were assessed monthly. Copepods, copepod nauplii, and ciliates were identified in the guts of A. coerulea polyps. Copepods with the bulk of total prey intake in number are an important source of nutrition for A. coerulea polyps in Jiaozhou Bay. Prey capture of A. coerulea polyps (prey polyp–1) varied among months, and was highly dependent upon the abundance of planktonic prey in the habitat. Copepods and copepod nauplii were digested more rapidly as temperature increased. Carbon weight-specific ingestion rate exhibited an obvious seasonal change, with the mean value of 0.13 ± 0.12 μg C μg C–1 d–1. More rapid digestion of prey at higher temperatures and larger prey availability would cause a higher ingestion rate in polyps. Scyphopolyps are widely distributed predators in littoral ecosystems and they may play an important role in plankton–benthos coupling by transferring energy from the water column to the benthos. Massive scyphopolyps blooms may influence pelagic ecosystems.

Effects of temperature and phytoplankton community composition on subitaneous and resting egg production rates of Acartia omorii in Tokyo Bay

To clarify the effects of temperature and phytoplankton community composition on Acartia omorii (Copepoda: Calanoida) egg production, its abundance and egg production rates were investigated from 2016 to 2018 in Tokyo Bay, Japan. Abundance was high from March to May (> 3.0 × 104 individuals m−3) and low or undetected from late June to December (≤ 0.4 × 104 individuals m−3). In 2018, most eggs were subitaneous until April; diapause eggs appeared in May when the water temperature exceeded 20 °C. The weight-specific egg production rate (SEPR, Cegg Cfemale−1 day−1) had two peaks. In the first peak in January, > 90% of eggs were subitaneous; in contrast, in the second peak in May, 60% of eggs were unhatched, including diapause eggs. The first peak of subitaneous eggs may contribute to planktonic population development from March to May. In contrast the second peak of diapause eggs probably enhances their recurrence in the next winter. Multiple regression analysis revealed that subitaneous SEPR showed a negative response, whereas diapause SEPR showed a positive response to temperature. Subitaneous SEPR positively correlated with the proportion of small diatoms in phytoplankton carbon biomass, whereas unhatched SEPR positively correlated with the proportion of inedible preys in large diatoms and dinoflagellates. Edible diatoms may induce subitaneous egg production, whereas low-food availability may induce diapause egg production. These results suggest that phytoplankton composition and water temperature have strong impacts on the dynamics of A. omorii via egg production.

Effect of in-situ simulated light levels on respiration rate of <italic>Euphausia superba</italic> in winter

As the key species in the Southern Ocean, how Antarctic krill (<italic>Euphausia superba</italic>, hereafter krill) survives through the extremely severe winter time is always one of the key issues for krill ecology. Krill can utilize different strategies to tackle the long winter time, and in which the most effective pattern is to decrease the metabolism and subsequently to reduce the energy consumption. The studies available indicate that the lighting condition could be the key of low energy consumption pattern; however, the in situ data are extremely limited. The oxygen consumption rate usually reflects the metabolic rate of organisms. Therefore, in order to explore the effect of in situ lighting conditions on the metabolism of krill, this study measured the oxygen consumption of krill during the successive 11 days under dark and lighting conditions based on the in situ aquarium experiment. In the experiment, the krill was placed in a closed bottle, and the respiration rate of the krill over a period of time was obtained by measuring the difference in the oxygen concentration of the seawater in the bottle before and after the experiment. A robust linear simulation method was used to eliminate the influence of outliers on the trend of daily variation in respiration rate of krill. Results showed that the average weight specific respiration rate of krill under light conditions was (0.270 4 ± 0.074 0) μL · (mg·h) ^-1, and the average weight specific respiration rate under dark conditions was (0.267 3±0.084 0) μL ·mg (·h) ^-1. In this study, in a period close to a natural day, the experimental group of krill was repeatedly tested by changing the conditions of darkness and 100 lx light intensity. The experimental results showed that the oxygen consumption level of krill did not show significant fluctuation. The comparative analysis demonstrated that the oxygen consumption of krill in the winter was significantly lower than that in the summer. The change of lighting condition within a natural day did not impact significantly on oxygen consumption of krill, but the stability of respiration rate of krill was impacted. The study supported the observation that krill was on low metabolism pattern during the winter time, and the stability of such pattern was also proved. The conclusion in the study will provide important basic data for revealing the overwintering mechanism of krill.

Routine metabolism of Antarctic krill (Euphausia superba) in South Georgia waters: absence of metabolic compensation at its range edge

Routine respiration rates in the South Georgia stock of Antarctic krill (Euphausia superba) were measured to compare with previously published measurements on stocks from colder locations further south. Within the natural temperature range of this species (− 1.8° to 5.5 °C), respiration rate data from both the present and previous studies were adequately fitted by a single Arrhenius regression (Q10 of 2.8), although South Georgia krill showed an upward deviation from this regression between 0° and 2 °C (the lower temperature range at South Georgia). Metabolic compensation (i.e. the comparative lowering of respiration rate) at the high temperatures experienced at South Georgia was not apparent, although the higher than predicted metabolic rates at low temperatures suggests acclimation of South Georgia krill to a warm water lifestyle. Weight-specific respiration rate was significantly higher in sub-adults and adults compared to juveniles, highlighting the metabolic burden of reproduction. South Georgia krill showed no further increase in respiration rate when exposed to acute temperatures (5.5–12.2 °C), indicating that they were already at the limit of aerobic capacity by 5.5 °C. Overall, this study shows that even small degrees of additional warming to South Georgia waters are likely to make conditions there metabolically unsustainable for Antarctic krill.

Wear performance of titanium reinforced biocompatible TPU

ABSTRACT The potential of this work is based on consideration of wear performance for the evaluation of abrasive wear of titanium micro particles reinforced thermoplastic polyurethane (TPU) composites. The particulates used in the composite are 1, 2 and 4 wt%. The influence of filler material on weight loss, wear index and specific wear rate on abrasive wear performance were studied and evaluated. The ploughing of particles from the specimen surface shows the higher wt% of titanium micro particles increases the wear rate in comparison with lower wt% with respect to the shore hardness of the composite.

English

AbstractVariable crayfish, Cambarus latimanus (LeConte), were collected and acclimated to four temperatures, 15, 20, 25, and 30°C. Following a two-week acclimation period, mean standard metabolic rates (SMR), as determined using oxygen consumption rates, were measured using an intermittent-flow, closed-loop respirometer. For ~10g mean weight C. latimanus, mean weight specific oxygen consumption rates (MO2) at 15, 20, 25, and 30°C were 73.4 ± 0.18, 81.6 ± 0.10, 103 ± 0.11, and 205 ± 0.12 mg O2·kg-1·h-1 (±SE), respectively. Calculated Q10 values of 1.25, 1.61, and 3.92 for the change in metabolic rate from 15 – 20°C, 20 – 25°C, and 25 – 30°C suggest the crayfish were responding normally to temperature increases and were metabolically stressed when temperatures increased above 25°C. Daily caloric energy budgets of 58 (15°C), 65 (20°C), 82 (25°C), and 164 (30°C) calories·day-1 were estimated for crayfishes using SMR data and suggested that crayfish standard (resting) energy requirements nearly tripled when acclimated to 15 versus 30°C. Overall, these data suggest that increased temperatures have substantial effects on C. latimanus energy demands which may reduce potential growth and reproduction.

Born too small: who survives in the public hospitals in Lilongwe, Malawi?

ObjectiveMalawi has the highest estimated preterm birth rate in the world. The survival rate of these babies is not known. The main objective of this study was to demonstrate the...

Estimation of the minimum food requirement using the respiration rate of medusa of Aurelia aurita in Sihwa Lake

We examined the respiration rate of Aurelia aurita medusae at 20 °C and 28 °C to evaluate minimum metabolic demands of medusae population in Sihwa Lake, Korea during summer. While weight specific respiration rates of medusae were constant and irrespective to the wet weight (8–220 g), they significantly varied in respect to temperatures (p<0.001, 0.11±0.03 mg C g−1 of medusa d−1 at 20°C and 0.28±0.11 mg C g−1 of medusa d−1 at 28 °C in average, where Q 10 value was 2.62). The respiration rate of medusae was defined as a function of temperature (T, °C) and body weight (W, g) according to the equation, R=0.13×2.62(T-20)/10 W 0.93. Population minimum food requirement (PMFR) was estimated from the respiration rate as 15.06 and 4.86 mg C m−3 d−1 in June and July, respectively. During this period, increase in bell diameter and wet weight was not significant (p=1 in the both), suggesting that the estimated PMFR closely represented the actual food consumption in the field. From July to August, medusae grew significantly at 0.052 d-1, thus the amount of food ingested by medusae population in situ was likely to exceed the PMFR (1.27 mg C m−3 d−1) during the period. In conclusion, the medusae population of higher density during June and July had limited amount of food, while those of lower in July and August ingested enough food for growth.

The effects of birth weight and gender on neonatal mortality in north central Nigeria

BackgroundWorldwide 15.5% of neonates are born with low birth weight, 95.6% of them in the developing countries. Prematurity accounts for 10% of neonatal mortality globally. The purpose of this study was to evaluate the effects of birth weight and gender on neonatal outcome.FindingsThe data of 278 neonates managed in the Special Care Baby Unit (SCBU) of Jos University Teaching Hospital (JUTH) over a 2 year period from July 2006 to June 2008 were analyzed.One hundred and fifty nine (57.2%) were males and 119(42.8%) females. There were 87(31.3%) preterm and 191 (68.7%) term babies. Twelve of the babies died. Seven (2.52%) and 5 (1.80%) being males and females respectively. The neonatal mortality rate by gender was not significant (p > 0.05). The neonatal mortality was 25.2 deaths per 1000 live births for boys and 18.0 for girls. The mean birth weights of the preterm and term babies were 1.88 ± 0.47 kg and 3.02 ± 0.50 kg respectively, with a mean gestational age of 30.62 ± 3.65 weeks and 38.29 ± 0.99 weeks respectively.Eighty seven (31.3%) of the babies were of low birth weight, 188(67.6%) were of normal birth weight and 3(1.1%) high birth weight. Of the low birth weight babies, 6(2.2%) were term small for gestational age. Six (2.2%) of the preterm infants had normal birth weight.Eleven of the babies that died were preterm low birth weight. The overall mortality rate was 4.32%. The birth weight specific mortality rate was 126 per 1000 for the preterm low birth weight and 5 per 1000 for the term babies. Birth weight unlike gender is a significant predictor of mortality, mortality being higher in neonates of <2.5 kg (OR = 0.04; 95% Cl 0.005-0.310, p = 0.002) (p = 0.453). Seven (58.3%) and 4(33.3%) of the pre-terms that died were appropriate and large for gestational age respectively. Gestational age is not a significant predictor of neonatal mortality (p = 0.595). Babies delivered at less than 37 weeks of gestation recorded a higher rate of mortality than those of 37 weeks and above (p = 0.000).The subjects showed one or more major clinical indications for admission. The major clinical indications for the preterm and term babies were respectively as follows: neonatal sepsis 63(22.7%) and 124(44.6%); neonatal jaundice 32(11.1%) and 71(24.7%); malaria 9(3.1%) and 13(4.5%); birth asphyxia 3(1.0%) and 7(2.4%). Neonatal sepsis was a common denominator among the babies that died.ConclusionBirth weight unlike gender is a significant predictor of neonatal outcome

The link between metabolic rate and body temperature in galliform birds in thermoneutral and heat exposure conditions: The classical and phylogenetically corrected approach

Three galliform species (grey partridges, ring-necked pheasants, and king quail) were involved in body temperature and resting metabolic rate measurements over a broad range of ambient temperatures (20–45 °C). At thermoneutrality, inter-species differences in colonic temperature, as well as in metabolic rate, were observed. During heat exposure, all species reacted by elevating their body temperatures above 44 °C, thereby inducing temporary hyperthermia. Heat-stressing birds resulted in a slightly increased metabolic rate in king quail, but not in partridges and pheasants. Based on data of body temperature and weight specific (per body mass unit) basal metabolic rate among ten species of Galliformes order, classical and phylogenetically corrected analyses of covariation between these two physiological traits were performed. The scaling of body temperature to body mass, revealed a significant exponent of: −0.0062 and −0.0080 for conventional and phylogenetical methods, respectively. In the analyzed species, a strong positive relationship between residuals of body mass values between body temperature and metabolic rate were found. The results obtained may show a plausible evolutionary link between these traits in galliform birds.

EFFECT OF HYDROGEN ION AND OXYGEN CONCENTRATIONON RESPIRATION PHYSIOLOGY ON SEAWATER SNAILPLANAXIS SULCATUS

The effect of some exogenous factors such as oxygen concentration and hydrogen ions concentration on the rate of oxygen consumption of seawater snail Planaxis sulcatus . This study was designed in Marine Sciences station (Aqaba) during the period September 2000 to October 2001 . High weight specific oxygen consumption rate was observed at pH range 7 to 8 (135.245_ 119.717μl. gˉ¹ . hrˉ ¹) respectively. The results showed that Any deviation from this range toward more acidic or alkaline pH reduced the oxygen consumption rate. The intertidal snail were oxygen conformers since their oxygen consumption rate was oxygen concentration dependent at least at high oxygen concentration thus, the weight specific oxygen consumption rate was increasing from as a result of increasing the oxygen concentration from 20 to 100% oxygen saturation .

Comparing the glucose kinetics of adolescent girls and adult women during pregnancy

Fetal energy demands are met mostly from oxidation of maternally supplied glucose. In pregnant adults this increased glucose requirement is met by an increase in gluconeogenesis. It is not known, however, whether, like their adult counterparts, pregnant adolescent girls can increase gluconeogenesis-hence, glucose production. Our objective was to measure glucose kinetics in 8 pregnant adolescents and 8 adult women. We measured glucose kinetics after an overnight fast by using a primed-constant 6-h U-(13)C-glucose infusion at the end of trimester 1 and early trimester 3. From trimester 1 to trimester 3, whole-body glucose production increased significantly in both groups (P < 0.01). However, whereas the weight-specific rate in adults increased by 18.2%, it increased by only 14.3% in adolescents. In adults, the increase in whole-body glucose production was largely due to a significant increase (P < 0.01) in the rate of gluconeogenesis, but in adolescents there was no change in whole-body gluconeogenesis, and weight-specific gluconeogenesis actually decreased by 11.7%. In both groups, the rate of whole-body glycogenolysis increased significantly (P < 0.05) in trimester 3, and in adolescents, it increased by 95%. These findings suggest that, in the fasted state in late pregnancy, pregnant adolescents cannot increase weight-specific glucose production by the same magnitude as their adult counterparts. Furthermore, whereas adult women increase glucose production primarily through gluconeogenesis, adolescents do so through glycogenolysis.

Oxygen consumption of doliolids (Tunicata, Thaliacea)

The goal of our study was to determine the oxygen consumption of gonozooids of the doliolid Dolioletta gegenbauri at near-environmental conditions. Time-series experiments included three different food concentrations and having the gonozooids suspended during the entire study periods while recording oxygen concentrations in the experimental vessels continuously with integrated planar optodes. Hourly oxygen consumption increased evenly with increasing body weight implying that weight-specific oxygen consumption rates did not change with increasing weight i.e. they were weight-independent. Weight-specific oxygen consumption rates at 218C resulted in average daily metabolic expenditures of 32.0% of body carbon. These rates were in the range of those of salps which had been collected in situ, and of non-feeding ephyrae of Aurelia aurita which were of similar weight as our gonozooids. No significant differences in oxygen consumption rates and metabolic expenditures among zooids feeding at different food levels were observed. Factors probably masking differences in oxygen rates were: (i) ingestion of the animal’s own fecal pellets, (ii) experimental time of 5 h being too short to detect food-related changes in the respiration level and (iii) increase in O2 consumption due to increased motion in small experimental vessels.

Glycine and urea kinetics in nonalcoholic steatohepatitis in human: effect of intralipid infusion

The rates of oxidation of glycine and ureagenesis were quantified in the basal state and in response to an intravenous infusion of intralipid with heparin (IL) in healthy subjects (n = 8) and in subjects with nonalcoholic steatohepatitis (NASH) (n = 6). During fasting, no significant difference in weight-specific rate of appearance (R(a)) of glycine, glycine oxidation, and urea synthesis was observed. Intralipid infusion resulted in a significant increase in plasma beta-hydroxybutyrate in both groups. The correlation between free fatty acids and beta-hydroxybutyrate concentration in plasma was 0.94 in NASH compared with 0.4 in controls, indicating greater hepatic fatty acid oxidation in NASH. Intralipid infusion resulted in a significant decrease in urea synthesis and glycine R(a) in both groups and did not impact glycine oxidation. The fractional contribution of glycine carbon to serine was lower in subjects with NASH before and after IL infusion. In contrast, the fractional contribution of serine carbon to cystathionine was higher in NASH before and following IL infusion. These results suggest that hepatic fatty acid oxidation is higher in NASH compared with controls and that glycine oxidation and urea synthesis are not altered. An increase in oxidative stress, induced by a higher rate of fatty acid oxidation in NASH, may have caused an increase in the contribution of serine to cystathionine to meet the higher demands for glutathione.

Organic carbon fluxes through the mesozooplankton and their variability at different time-scales in the Gullmarsfjord, Sweden

Study of rate process responses and carbon transfer rates in the plankton is a well developed field, but attention has focused on seasonal or longer scales and knowledge on variability patterns and modulating mechanisms at shorter scales is very limited. Here we investigated variability in pelagic carbon transfer rates on daily and seasonal scales in the Gullmar Fjord, Sweden. Hierarchical sampling was carried out in five campaigns in different seasons each of which consisted of 8–12 d with sampling every other day. Algal ingestion, copepod egg and pellet production and vertical flux measured as pigments and pellets varied significantly between days as well as between seasons. Algal ingestion was highest in autumn (weight-specific rate: 0.3–1 d −1) and at the start of the spring bloom (0.3–1.5 d −1), while egg production was highest in summer–autumn (0.1–0.5 d −1). Vertical flux peaked in summer with 4–6 mg pigment m −2 d −1 and up to 150 mg pellet Cm −2 d −1. Consonant responses between species were observed indicating a common food source for the mesozooplankton. Changes in trophic functions occurred on scales of days and the coupling between pelagic processes and vertical flux was strong. There were, however, both positive and negative responses which could not be explained by simple predator–prey interactions. The food quality in terms of prey type and biochemical composition are suggested as crucial factors for the variability both within the pelagic environment as well as for the vertical flux out of the upper layers in the ocean.

Methane release from millipedes and other soil invertebrates in Central Europe

The potential for methane production was investigated in 47 species of soil invertebrates. No detectable methane production was found in slugs, earthworms, potworms, oribatid mites, woodlices, springtails, centipedes, ants and soil diptera larvae. However, significant methane production was found in several temperate millipedes including some species from the order Julida ( Leptoiulus trilobatus, Megaphyllum projectum, Megaphyllum unilineatum, Unciger transsilvanicus, Unciger foetidus, Leptoiulus proximus and Julus scandinavius). On the other hand, methane production was not confirmed in Cylindroiulus boleti which belongs to the same family. Members of the other orders (Glomerida and Polydesmida) did not release methane with the exception of one questionable recorded release in Polydesmus complanatus (Polydesmida, Polydesmidae). Methane producing species of millipedes showed significantly lower weight-specific rates of methane release than the cockroach Periplaneta americana and termite Prorhinotermes simplex. Methane release from millipedes was temperature-dependent; for the temperature range 5–25 °C, a Q 10 between 1.55 and 2.17 was calculated and the relationship between methane release and temperature was described by an exponential curve. Our results suggest that although overall methane fluxes from soil invertebrates under study cannot substantially influence a methane budget in most ecosystems, methane production is significant at least in some millipedes and therefore can impact mesoenvironments and microenvironments inhabited by these invertebrates. This work also confirms that methane production is not only supported by tropic soil invertebrates, but also by temperate species.

Effect of body weight and acclimated temperature on the respiration physiology on seawater snail Planaxis sulcatus

This study was designed in Marine Sciences station (Aqaba) during the period September 2000 to October 2001 . The study of the effect of body weight on the metabolic rate revealed the presence of a proportional relationship between the metabolic and body weight and the presence of inverse relationship between the metabolic and body weigh.In snails acclimated to 10 ºC, 20 ºC, and 30 ºC, the Weight specific metabolic rate was influenced by both acclimation as well as experimental temperature. Thus, the oxygen consumption rate increased 1n 10 ºC acclimated snail from 44 µl O2. gˉ¹ . hrˉ ¹ to 105 µl O2. gˉ¹ . hrˉ ¹ As a result of increasing the experimental temperature from 10 ºC to 30. ºC In 20 and 30 ºC acclimated snail, and as a result of increasing the experimental temperature from 10 to 30, the weight specific oxygen consumption rates increased (20 ºC and 30 ºC ) from 40 µl O2. gˉ¹ . hrˉ ¹ to 88 and 35 to 85 µl O2. gˉ¹ . hrˉ ¹ Respectively. Snails acclimated to 10 ºC ,20 ºC and 30 ºC showed Precht s type 3 normal the(partial) compensation in weight specific oxygen consumption rate , since at all experiment temperatures , the highest oxygen consumption rate was observed in 10 ºC Acclimated animals, whereas the lowest rate was observed in 30 ºC acclimated snails.