Oxygen Consumption Of Larvae Research Articles

Acidification stress effect on umbonate veliger larval development in Panopea globosa

Ocean acidification generates a decrease in calcium carbonate availability essential for biomineralization in organisms such as mollusks. This effect was evaluated on Panopea globosa exposing for 7 days umbonate veliger larvae to two pH treatments: experimental (pH 7.5) and control (pH 8.0). Exposure to pH 7.5 affected growth, reducing larval shell length from 5.15–13.34% compared to the control group. This size reduction was confirmed with electron microscopy, also showing shell damage. The physiological response showed an increase in oxygen consumption in larvae exposed to low pH with a maximum difference of 1.57 nmol O2 h−1 larvae−1 at day 7. The gene expression analyses reported high expression values for nicotinamide adenine dinucleotide (NADH) dehydrogenase and Perlucin in larvae at pH 7.5, suggesting a higher energetic cost in this larval group to maintain homeostasis. In conclusion, this study showed that acidification affected development of P. globosa umbonate veliger larvae.

The effect of abrupt salinity change on oxygen consumption in crab megalopae of Chincoteague Bay, USA

Variability in salinity is an environmental stressor that crab megalopae encounter as they are carried by tides and currents throughout Chincoteague Bay. We exposed blue crab (Callinectes sapidus) and fiddler crab (Uca spp.) megalopae to abrupt salinity changes from 10 to 31 ppt and measured their oxygen usage. It was hypothesized that the megalopae would cope with the changes in a manner reflective of the documented abilities and tolerances of adult crabs. It was also hypothesized that lower salinities would have a particularly detrimental effect on the megalopae reflected by both increased oxygen usage and mortality. The megalopae of both species did exhibit an increase in oxygen use at lower salinities, although the effect was more pronounced during the initial transition and decreased during acclimation. The megalopae mirrored the adult responses, with blue crab larvae consuming more oxygen per mg of wet weight at lower salinities, whereas fiddler crab larval oxygen consumption was relatively uniform at all salinities. Mortality of some blue crab postlarvae was observed at 10 ppt while all larval fiddler crabs survived. Coupled with the introduction of additional fresh water into the global water system, these results indicate that further investigation into this subject is necessary.

Effect of salinity on the metabolism and osmoregulation of selected ontogenetic stages of an Amazon population of Macrobrachium amazonicum shrimp (Decapoda, Palaemonidae).

Probably as a function of their wide geographical distribution, the different population of Macrobrachium amazonicum shrimp may present distinct physiological, biochemical, reproductive, behavioral, and ecological patterns. These differences are so accentuated that the existence of allopatric speciation has been suggested, although initial studies indicate that the genetic variability of populations happen at an intraspecific level. Among the biological responses described for M. amazonicum populations, those regarding osmoregulation and metabolism play a key role for being related to the occupation of diverse habitats. To this effect, we investigated osmoregulation through the role of free amino acids in cell volume control and metabolism, through oxygen consumption in larvae (zoeae I, II, V and IX) and/or post-larvae of a M. amazonicum population from Amazon, kept in aquaculture fish hatcheries in the state of São Paulo. The results add information regarding the existence of distinct physiological responses among M. amazonicum populations and suggest that possible adjustments to metabolism and to the use of free amino acids as osmolytes of the regulation of the larvae and post-larvae cell volume depend on the appearance of structures responsible for hemolymph osmoregulation like, for example, the gills. In this respect, we verified that zoeae I do not alter their metabolism due to the exposition to fresh or brackish water, but they reduce intracellular concentration of free amino acids when exposed to fresh water, what may suggest the inexistence or inefficient performance of the structures responsible for volume regulation and hemolymph composition. On the other hand, in zoeae II and V exposed to fresh and brackish water, metabolism alterations were not followed by changes in free amino acids concentration. Thus it is possible, as the structures responsible for osmoregulation and ionic regulation become functional, that the role of free amino acids gets diminished and oxygen consumption elevated, probably due to greater energy expenditure with the active transportation of salts through epithelial membranes. Osmotic challenges also seem to alter throughout development, given that in zoeae II oxygen consumption is elevated on brackish water of 18, but in zoeae V it happens in fresh water. After M. amazonicum metamorphosis, free amino acids begin to play an important role as intracellular osmolytes, because we verified an increase of up to 40% in post-larvae exposed to brackish water of 18. The main free amino acids involved in cell volume regulation of ontogenetic stages evaluated were the non essential ones: glutamic acid, glycine, alanine, arginine, and proline. Interestingly, larvae from estuarine population studied here survived until the zoeae V stage in fresh water, but in some populations far from the sea, zoeae die right after eclosion in fresh water or they do not reach zoeae III stage. In addition, given that in favorable conditions caridean shrimp larvae shorten their development, we may infer that the cultivation environment, in which larvae developed in the present work, was appropriate, because almost all zoeae VIII kept on brackish water underwent metamorphosis directly to post-larvae and did not go through zoeae IX stage.

Responses of the metabolism of the larvae of Pocillopora damicornis to ocean acidification and warming.

Ocean acidification and warming are expected to threaten the persistence of tropical coral reef ecosystems. As coral reefs face multiple stressors, the distribution and abundance of corals will depend on the successful dispersal and settlement of coral larvae under changing environmental conditions. To explore this scenario, we used metabolic rate, at holobiont and molecular levels, as an index for assessing the physiological plasticity of Pocillopora damicornis larvae from this site to conditions of ocean acidity and warming. Larvae were incubated for 6 hours in seawater containing combinations of CO2 concentration (450 and 950 µatm) and temperature (28 and 30°C). Rates of larval oxygen consumption were higher at elevated temperatures. In contrast, high CO2 levels elicited depressed metabolic rates, especially for larvae released later in the spawning period. Rates of citrate synthase, a rate-limiting enzyme in aerobic metabolism, suggested a biochemical limit for increasing oxidative capacity in coral larvae in a warming, acidifying ocean. Biological responses were also compared between larvae released from adult colonies on the same day (cohorts). The metabolic physiology of Pocillopora damicornis larvae varied significantly by day of release. Additionally, we used environmental data collected on a reef in Moorea, French Polynesia to provide information about what adult corals and larvae may currently experience in the field. An autonomous pH sensor provided a continuous time series of pH on the natal fringing reef. In February/March, 2011, pH values averaged 8.075±0.023. Our results suggest that without adaptation or acclimatization, only a portion of naïve Pocillopora damicornis larvae may have suitable metabolic phenotypes for maintaining function and fitness in an end-of-the century ocean.

Reproduction in Cultured versus Wild Coral Colonies: Fertilization, Larval Oxygen Consumption, and Survival

In the late 1990s, the once prolific populations of the coral Acropora intermedia surrounding Okinawa, Japan, dramatically declined because of thermal stress, bleaching caused by heat stress, and consequent mortality. Before the bleaching event, 72 fragments (about 15 cm in length) were collected and transferred to the Okinawa Churami Aquarium. Through growth and repeated fragmentation, these original fragments developed into about 100 colonies that spawned from 1999 to 2009. In this study, we compared gametogenesis, fertilization, survival, and O(2) consumption in cultured and wild colonies of A. intermedia and their offspring. Cultured A. intermedia had larger oocytes and higher fertilization and survival rates than samples from wild colonies. O(2) consumption of cultured embryos was similar to that of wild embryos. These results suggest that cultured A. intermedia and their offspring are as viable as wild colonies. Aquaria can play a role in the conservation of endangered corals, and their cultured colonies could be used to re-establish devastated species on the Okinawa reefs.

Switching of metabolic-rate scaling between allometry and isometry in colonial ascidians.

The metabolic rate and its scaling relationship to colony size were studied in the colonial ascidian Botrylloides simodensis. The colonial metabolic rate, measured by the oxygen consumption rate (V(O2) in millilitres of O(2) per hour) and the colony mass (wet weight M(w) in grams) showed the allometric relationship (V(O2) = 0.0412 M(w)(0.799). The power coefficient was statistically not different from 0.75, the value for unitary organisms. The size of the zooids and the tunic volume fraction in a colony were kept constant irrespective of the colonial size. These results, together with the two-dimensional colonial shape, excluded shape factors and colonial composition as possible causes of allometry. Botryllid ascidians show a takeover state in which all the zooids of the parent generation in a colony degenerate and zooids of a new generation develop in unison. The media for connection between zooids such as a common drainage system and connecting vessels to the common vascular system experienced reconstruction. The metabolic rate during the takeover state was halved and was directly proportional to the colonial mass. The scaling thus changed from being allometric to isometric. The alteration in the scaling that was associated with the loss of the connection between the zooids strongly support the hypothesis that the allometry was derived from mutual interaction among the zooids. The applicability of this hypothesis to unitary organisms is discussed.

Effects of UV‐A and UV‐B on oxygen consumption in common toad (Bufo bufo) tadpoles

AbstractThe effects of UV‐A and UV‐B (Cracow District, Poland, 50°04′N, 19°57′E; 220 m a.s.l.) on oxygen consumption were studied in common toad Bufo bufo (L.) tadpoles (Gosner stage 27). Ecologically relevant chronic doses of UV were simulated in the laboratory. Larvae separated for experiment were derived from UV‐exposed or not exposed embryos. After hatching, tadpoles in stages 24–27 were treated with UV‐A or UV‐B. UV‐A caused significant increases in oxygen consumption in larvae grown from untreated embryos, whereas no changes occurred in tadpoles irradiated with UV‐A during embryonic and larval development. UV‐B caused significant decreases in oxygen consumption in all exposed tadpoles. The changes were larger in larvae derived from eggs not exposed to UV‐B than in tadpoles grown from UV‐B‐treated embryos. Our results suggest that ambient levels of UV‐A and especially UV‐B may affect the metabolic rate of common toad larvae living in shallow habitats. Affected respiration may retard development as well as increase the susceptibility of tadpoles to ecologically relevant pathogens. On the other hand, it seems that UV‐irradiation induces some adaptive processes during embryonic development, which increase the resistance of the larval respiratory system to solar UV radiation.

Energy metabolism in eggs and larvae of the Senegal sole

Oxygen consumption in Solea senegalensis increased during the egg stage reaching values close to 4 nmol O2 ind−1 at hatching. After hatching, larval oxygen consumption continued to increase, reaching a maximum rate of 9.97−1±87 nmol O2 ind−1 h−1 2 days after the opening of the mouth. Body nitrogen content decreased mainly after exhaustion of yolk reserves. Carbon content decreased during the whole endogenous feeding phase, although it decreased twice as quickly after yolk‐sac absorption. The free amino acid (FAA) depletion rate was higher during egg development and the yolk‐sac period. Complete yolk absorption coincided with the consumption of the 90% of initial FAA content in the eggs and the remaining FAA were consumed at a lower rate. Based on stoichiometrical calculations, FAA appears to be the most important energy substrate during the egg stage (86%) in the Senegal sole. During the period from hatching to the mouth opening, contributions of FAA and lipids as metabolic fuels were similar (41 and 47%, respectively). The decrease in larval protein content during starvation indicates that amino acids from body protein are used as energy substrates under food deprivation.

Effect of salinity reduction on oxygen consumption by larval estuarine invertebrates

Unpredictable events can cause rapid sizable changes in environmental conditions. Storm events are an example of an unpredictable event; in estuarine habitats, storms can bring about drastic changes in salinity levels within several hours. This study focused on the effect of salinity reduction on larval oxygen consumption. Two species of larval invertebrates were exposed to salinity reduction, the marine polychaete Arenicola cristata Stimpson and the mud snail Ilyanassa obsoleta (Say). In experimental treatments, salinity was reduced to 10 or 15‰; control individuals were maintained at 30‰. Salinity was reduced for 3 d when larvae were between the ages of 1 and 4 d, post-hatch. Oxygen consumption was the same among treatments during salinity reduction for I. obsoleta larvae. The oxygen consumption of A. cristata larvae was significantly lower at 10‰S compared with controls and with salinity reduction to 15‰; larvae eventually died at 10‰. After salinity reduction ceased, larvae exposed to a salinity reduction to 15‰ consumed more (A. cristata) or the same (I. obsoleta) amount of oxygen as individuals maintained at 30‰. We have shown in previous experiments that salinity reduction results in significant reductions in larval growth in A. cristata and I. obsoleta larvae as well as in changes in developmental rates of A. cristata (but not I. obsoleta) larvae. Taken in conjunction with the results of our present study on larval oxygen consumption, the results suggest that salinity reduction has a large impact on estuarine invertebrates.

Metabolic importance of Na+/K+-ATPase activity during sea urchin development.

Early stages of animal development have high mass-specific rates of metabolism. The biochemical processes that establish metabolic rate and how these processes change during development are not understood. In this study, changes in Na+/K+-ATPase activity (the sodium pump) and rate of oxygen consumption were measured during embryonic and early larval development for two species of sea urchin, Strongylocentrotus purpuratus and Lytechinus pictus. Total (in vitro) Na+/K+-ATPase activity increased during development and could potentially account for up to 77 % of larval oxygen consumption in Strongylocentrotus purpuratus (pluteus stage) and 80 % in Lytechinus pictus (prism stage). The critical issue was addressed of what percentage of total enzyme activity is physiologically active in living embryos and larvae and thus what percentage of metabolism is established by the activity of the sodium pump during development. Early developmental stages of sea urchins are ideal for understanding the in vivo metabolic importance of Na+/K+-ATPase because of their small size and high permeability to radioactive tracers (86Rb+) added to sea water. A comparison of total and in vivo Na+/K+-ATPase activities revealed that approximately half of the total activity was utilized in vivo. The remainder represented a functionally active reserve that was subject to regulation, as verified by stimulation of in vivo Na+/K+-ATPase activity in the presence of the ionophore monensin. In the presence of monensin, in vivo Na+/K+-ATPase activities in embryos of S. purpuratus increased to 94 % of the maximum enzyme activity measured in vitro. Stimulation of in vivo Na+/K+-ATPase activity was also observed in the presence of dissolved alanine, presumably due to the requirement to remove the additional intracellular Na+ that was cotransported with alanine from sea water. The metabolic cost of maintaining the ionic balance was found to be high, with this process alone accounting for 40 % of the metabolic rate of sea urchin larvae (based on the measured fraction of total Na+/K+-ATPase that is physiologically active in larvae of S. purpuratus). Ontogenetic changes in pump activity and environmentally induced regulation of reserve Na+/K+-ATPase activity are important factors that determine a major proportion of the metabolic costs of sea urchin development.

Effects of temperature on oxygen consumption, growth, and development of embryos and yolk-sac larvae of Siganus randalli (Pisces: Siganidae)

Eggs from laboratory spawnings of the coralreef fish Siganus randalli Woodland were incubated at two temperatures (27 and 30 °C). Eggs and larvae were sampled until larval starvation, while changes in oxygen consumption, growth, yolk utilization, and development were monitored. Oxygen consumption, which peaked at hatching, was higher for embryos incubated at 30 °C than at 27 °C. Rates of oxygen consumption (nl h-1 individual-1) at hatching were similar to those for other temperate and tropical species. Rates of oxygen consumption by yolk-sac larvae were highly variable, and these data suggest that larval oxygen consumption prior to yolk-sac absorption may not be significantly influenced by temperature. Rates of yolk depletion were higher for larvae at the higher temperature. After an initial rapid increase in length, length of larvae at 30 °C decreased with age. Egg size, egg weight, and maximum notochord length of larvae differed significantly between spawns. Age-specific oxygen consumption rates by the embryos varied between spawns, but regressions describing oxygen consumption as a function of age did not differ significantly. The initiation and completion of eye pigmentation were used as developmental markers to calculate the amount of yolk remaining for larvae at the different temperatures. Larvae maintained at 30 °C completed eye pigmentation approximately 3 h sooner than those maintained at 27 °C, but had less endogenous reserves. This finding indicates a trade-off between rapid development and efficient utilization of the endogenous reserves. The completion of eye pigmentation in larvae incubated at the higher temperature occurred at midnight and, depending on the amount of time that the larvae have to initiate feeding prior to the “point-of-no-return”, the timing of completion of eye pigmentation could influence larval survival.

Effects of temperature and salinity stress on osmoionic regulation in adults and on oxygen consumption in larvae and adults of Macrobrachium amazonicum (decapoda, palaemonidae)

1. 1. The effects of temperature (17, 24 or 31C) and salinity (0, 5, 10, 15 or 25%.) on the ionic, osmotic or respiratory responses were investigated in larvae (zoeae I and II) and adults of the freshwater shrimp Macrobrachium amazonicum. 2. 2. In adults, the blood levels of Na + and Cl − were kept hyperionic in salinities from 0 to 15%. and isoionic (Na +) or slightly hypoionic (Cl −) in 25%. 3. 3. The blood levels of K + and Ca 2+ were regulated hyperionically (and those of Mg 2+ hypoionically) at all salinities tested. 4. 4. Hyperosmotic regulation of the blood at low salinities broke down above 15%. and blood and medium were isosmotic in 25%. At the same time, the blood total-solids content decreased markedly with increasing salinity, especially at 24 and 31C. 5. 5. The oxygen consumption ( VO 2) of larvae and adults rose only slightly with temperature, whereas increasing salinities brought about a pronounced reduction of VO 2 in the larvae but not in adults.

Oxygen consumption by eggs and larvae of striped mullet, Mugil cephalus, in relation to development, salinity and temperature

Oxygen consumption rates during embryonic and the first 38 days of larval development of the striped mullet were measured at 24° C by differential respirometry. Measurements were obtained at the blastula, gastrula and four embryonic stages, and at the yolk‐sac, preflexion, flexion and post‐flexion larval stages.Oxygen uptake rates of eggs increased linearly from 0.024 μl O2 per egg h‐1 (0·323 μl O2 mg‐1 dry wt h‐1) by blastulae to 0·177 μlO2 per egg h‐1 (2·516 μlO2mg 1dry wth‐1) by embryos prior to hatching. Respiration rates did not vary significantly among four salinities (20,25, 30, 35%0).Larval oxygen consumption increased in a curvilinear manner from 0·243 μl O2 per larva h‐1 shortly after hatching to 18·880 μl O2 per larva h‐1 on day 38. Oxygen consumption varied in direct proportion to dry weight. Mass‐specific oxygen consumption rates of preflexion, flexion, and postflexion larvae did not change with age (10·838 μl O2 mg 1dry wt h‐1).Larval oxygen consumption rates did not vary significantly among salinities 10–35%. Acute temperature increases elicited significant increases in oxygen consumption, these being relatively greater in yolk‐sac larvae (Q10= 2·75) than in postflexion larvae (Q10= 1·40).

Characteristics of the larval diapause in Ctenucha virginica (Lepidoptera: Arctiidae)

Ctenucha virginica (Esp.), a univoltine species in Québec, overwinters as a late-instar larva. Larvae brought into the laboratory between October and February and placed at 25°C under 16 h light-8 h dark, showed reduced feeding, diurnal movement, diurnal oxygen consumption, and developmental rates when compared to larvae collected in the spring. However, C. virginica displayed no seasonal variation in nocturnal metabolic rates or activity levels. Furthermore, the oxygen consumption of larvae in diapause was temperature dependent, with Q 10s varying from 2.7 (nocturnal) to 4.0 (diurnal). The ability to overwinter in any one of three larval instars may help C. virginica to synchronize its diapause initiation with the onset of low temperatures. This is especially important for C. virginica, as larvae held at 25°C under 16 h light-8 h dark during diapause died, probably due to a high metabolic rate coupled with a reduced food intake.

87:6531 Effects of water temperature and hypoxia on the oxygen consumption of larvae and post-larvae of king crab: Nakanishi, Takashi, 1987. Bull. japan. Soc. scient. Fish., 53(2):235–237. (In Japanese, English abstract.) Japan Sea Reg. Fish. Res. Lab., Suidocho, Niigata 951, Japan

87:6531 Effects of water temperature and hypoxia on the oxygen consumption of larvae and post-larvae of king crab: Nakanishi, Takashi, 1987. Bull. japan. Soc. scient. Fish., 53(2):235–237. (In Japanese, English abstract.) Japan Sea Reg. Fish. Res. Lab., Suidocho, Niigata 951, Japan

Physiological and biochemical energetics of larvae of Teredo navalis L. and Bankia gouldi (Bartsch) (Bivalvia : Teredinidae)

The biochemical composition of larvae of Teredo navalis L. and Bankia gouldi (Bartsch) (Bivalvia: Teredinidae) was examined throughout larval development at 23°C and 30–32%. salinity in the presence of the phytoplankton food Isochrysis aff. galbana (clone T-ISO), during a delay of metamorphosis in the presence of food but absence of a wood substratum and during periods of enforced starvation. Newly released Teredo navalis larvae had a mean length ( L) and height ( H) of 89.3 and 76.1 μm respectively. The first appearance of pediveliger larvae at 212.1 μm L and 230.0 μm H occurred 27 days after release. Larval dry weight increased from 0.29 μg to 1.96 μg during this period. Newly formed straight hinge larvae of Bankia gouldi had dimensions of 62.8 μm L and 49.8 μm H. Metamorphically competent B. gouldi larvae had dimensions of 230.0 μm L and 282.9 μm H and were first observed 20 days after fertilization. Larval dry weight increased from 0.06 μg to 2.20 μg during this period. During enforced delay of metamorphosis the ash-free dry weight of Teredo navalis larvae decreased whereas the ash free dry weight of Bankia gouldi larvae increased. During the early period of shelled larval development both species showed similar decreases in lipid, protein and carbohydrate levels (μg·mg dry weight −1); however, this was reflected in a decrease in biochemical content (μg·larva −1) only in Teredo navalis. During enforced starvation the major proportion of both the weight and caloric losses were due to protein. Lipid also contributes significantly to these losses whereas the contribution of carbohydrate was small. Larval oxygen consumption rates were determined directly by manometry and indirectly by estimates of decrease in caloric content during periods of enforced starvation. Direct and indirect determinations for T. navalis are described by the relationships R = 1.16 W 1.05 and R = 0.98 W 1.24 respectively where R is the respiration rate in nl O 2 · larva −1 · h −1 and W is dry weight inclusive of shell in μg. Direct and indirect determinations for Bankia gouldi are described by the relationships R = 1.37 W 1.25 and R = 1.81 W 1.25 respectively. When data for both assay procedures are combined for each species the relationships R = 1.10 W 1.07 and R = 1.44 W 1.18 are obtained for Teredo navalis and Bankia gouldi respectively.

Effects of oil exposure on oxygen consumption of cod eggs and larvae

The oxygen consumption reflects the aerobic energy production of an animal. For fish eggs and larvae the normal oxygen consumption represents the optimal conditions for growth and development. Under the stress of environmental pollution gross deviation in oxygen uptake rate of the developing fish embryo may reflect metabolic disturbances and impede the development. Since the eggs and larvae of cod ( Gadus morhua L.) are likely to be exposed to oil pollution from offshore installations in the North Sea we decided to investigate the effects of the water-soluble fraction (WSF) of North Sea crude oil on the oxygen consumption of cod eggs and larvae. The results showed that oxygen consumption of the larvae at the time of final yolk absorption (5–7 days post hatching at 5°C) is strongly suppressed by oil exposure at concentrations down to 50 ppb. No effect on the oxygen uptake, however, was found during the egg stage.

The Pacific oyster Crassostrea gigas: Part II. Oxygen consumption of larvae and adults

The effects of body size and season on oxygen consumption of C. gigas were studied. During larval development, oxygen consumption increased from 0.4 nl O 2 h −1 larva −1 (larvae with mean dry tissue weight of 70 ng) to 6.1 nl O 2 h −1 larva −1 (mean dry tissue weight of 1 360 ng). Oxygen uptake of larvae (ml O 2 h −1 larva −1) as a function of body size is described by the allometric equation VO 2=0.00282W 0.96 In adult oysters (0.03−1 741 mg dry tissue weight), the relationship between oxygen consumption — expressed as ml O 2 h −1 individual −1 — and body size is described by the allometric equation VO 2=0.00316W 0.77 Comparison of different trials showed a marked seasonal effect on oxygen uptake, with greater consumption rates in summer than in winter.

Oxygen Consumption During the Metamorphosis of the Parasitic Lamprey, Lampetra Fluviatilis (L.) and Its Non-Parasitic Derivative, Lampetra Planeri (Bloch)

ABSTRACT Standard oxygen consumption has been measured during the six stages of metamorphosis in both the anadromous parasitic lamprey, Lam-petra fluviatilis, and in its non-parasitic derivative, Lampetra planeri. At 10 °C, the standard rates in larval L. planeri and L. fluviatilis of metamorphosing size were 20·3 and 29·3 μl g−1 h−1 respectively. After a slow rise in oxygen consumption during the initial stages of metamorphosis, the rates reached 50·5 and 60·4 μl g−1 h−1 at stage of 6 of L. planeri and L. fluviatilis respectively. Following the completion of metamorphosis in L. planeri and the development of secondary sexual characters, the mean rate in males rose to 73·3 μ g−1 h−1, compared with a decline in females to 44·1 μ g−1 h−1. Although no circadian rhythm was detectable in the oxygen consumption of larvae, an elevation in the metabolic rate was present during darkness in L. fluviatilis at the end of metamorphosis. Standard oxygen consumption and ventilatory frequency were influenced greatly by temperature, e.g. values for stage 6 of L. fluviatilis rose from 24·3 μl g−1 h−1 and 33·0 beats min−1 at 5 °C to 103·8 μl g−1 h−1 and 98·2 beats min−1 at 15 °C. The results are discussed in the context of the radical changes taking place during metamorphosis and in terms of the differences between larvae and adult and between the life cycles of parasitic and non-parasitic lampreys.

The Influence of Temperature on Oxygen Consumption in the Larvae of Toxorhynchites Splendens (Wiedemann) (Diptera: Culicidae)

It is known that the metabolism of insects varies with environmental temperature and the respiratory rate is frequently used as a criterion of metabolic effect. Though some work has been done with mosquitoes on the changes in oxygen uptake during development (Sen, 1915, Ind. J. Med. Res. 2: 681–87; Olifan, 1947, Dokl. Acad. Nauk SSSR 55: 169–72; Christophers, 1960, Aedes aegypti, the yellow fever mosquito, 739 p.), studies on acclimation to temperature have been neglected. Therefore the changes in metabolism in relation to temperature as reflected by the rate of oxygen consumption in larvae of Toxorhynchites splendens has been determined.