Helminth communities of two green frogs (Rana perezi and Rana saharica) from both shores of the Alboran Sea

The helminth communities of two populations of green frogs from both shores of the Alborón Sea (Western Mediterranean) were studied. Of the 79 frogs examined for helminths, 39 individuals of the species Rano saharica were collected from Bob-Taza (Morocco), and 40 of the species Rona perezi were collected from the Natural Park of the Sierra de Grazalema (Spain). Although the species richness of helminths was identical in the two sampled areas, the differences observed in the structure of the helminth infracommunities were quite important. Statistically, significant differences were found between the species richness and the diversity of the infracommunities of R. perezi female population and the other three studied statistical populations. The helminth component communities of these two green frogs can be considered as depauperate, although their infracommunities present interactive features.     

The physiology of hibernation in Canadian leopard frogs (Rana pipiens) and bullfrogs (Rana catesbeiana)

Canadian northern leopard frogs (Rana pipiens) and bullfrogs (Rana catesbeiana) were acclimated to 3 degrees C and submerged in anoxic (0-5 mmHg) and normoxic (Po(2) approximately 158 mmHg) water. Periodic measurements of blood Po(2), Pco(2), and pH were made on samples taken anaerobically from subsets of each species. Blood plasma was analyzed for [Na(+)], [K(+)], [Cl(-)], [lactate], [glucose], total calcium, total magnesium, and osmolality. Blood hematocrit was determined, and plasma bicarbonate concentration was calculated. Both species died within 4 d of anoxic submergence. Anoxia intolerance would rule out hibernation in mud, which is anoxic. Both species survived long periods of normoxic submergence (R. pipiens, 125 d; R. catesbeiana, 150 d) with minimal changes in acid-base and ionic status. We conclude that ranid frogs require a hibernaculum where the water has a high enough Po(2) to drive cutaneous diffusion, allowing the frogs to extract enough O(2) to maintain aerobic metabolism, but that an ability to tolerate anoxia for several days may still be ecologically meaningful.     

Multiple paternity in the common frog (Rana temporaria): genetic evidence from tadpole kin groups

Very few studies have investigated the occurrence of multiple paternity and sperm competition in amphibians. We studied genetic relatedness within kin groups of tadpoles of an aquatically breeding anuran Rana temporaria using allozymes. We collected samples from 52 naturally fertilized spawn clumps produced by single females at three breeding sites in two populations. We estimated relatedness (r) within kin groups, and compared the observed genotype distributions of the tadpoles (on average 23 individuals in each group) with the expected distributions based on single mating. Average relatedness over five polymorphic loci was 0.44 and 0.43 in the two populations, the latter being significantly smaller than that expected by single mating (0.5). The number of patrilines, calculated from relatedness estimates, was 1.3 in one population and 1.4 in the other. Genotype distributions deviated significantly from the expected in half of the kin groups and at all breeding sites. The results show that egg clutches of R. temporaria commonly contain multiply sired offspring. We suggest that communal breeding may affect paternity patterns in R. temporaria as well as in anurans in general.     

A study on hearing in frogs (Rana pipiens and Rana clamitans)

Zusammenfassung Die relative Reizschwellkurve für die Schallempfindung bei den Fröschen Rana clamitans und R. pipiens wurde in dem Frequenzbereich von 30–15000 Hz bestimmt. Die Kurve ist dieselbe für beide Geschlechter. Versuche zeigten, daß Schälle entweder inhibierend oder stimulierend auf die Atmungsbewegungen wirken können. Diese Wirkung wird nicht von der Frequenz oder der Intensität der Schälle bestimmt, sondern von dem physiologischen Zustand des Tieres.Die Latenzzeit zwischen Reiz und Effekt ist unabhängig von der Tonfrequenz, wird aber von den Intervallen zwischen aufeinanderfolgenden Reizen beeinflußt; sie wird kürzer, wenn die Intervalle verlängert werden.Dressurversuche mit 18 Tieren, unter Anwendung von Strafung durch elektrische Schläge und einem Dressurton von 300 Hz, ergaben positive Erfolge bei zwei Individuen von R. clamitans.

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Contribution No. 67 of the Department of Biology, Hamilton College, McMaster University, Hamilton, Ontario.     

The effect of the systemic fungicide benomyl on survival and reproduction of the bird cherry aphid (Rhopalosiphum padi)

Weight gain and intrinsic rate of population increase (r_m) of Rhopalosiphum padi were measured on wheat plants given soil drenches of benomyl at various concentrations. Reduced weight gain occurred with concentrations as low as 3.125 ppm. Mortality of aphids significantly exceeded control mortality at 25 ppm, and no aphids survived concentrations above 50 ppm. Development time was extended at 12.5 ppm and above. Reductions in fecundity and r_m became statistically significant by 25 ppm. Topical application of benomyl at 100 ppm or above increased aphid mortality, which reached 97% at 400 ppm. Weight gain of aphids was also reduced by topical application at 100 ppm. A factorial experiment showed absence of interaction between the effects on aphid weight of soil drench application to plants and topical application to aphids.     

A structure-based site-directed mutagenesis study on the neurolysin (EC 3.4.24.16) and thimet oligopeptidase (EC 3.4.24.15) catalysis

Neurolysin (EP24.16) and thimet oligopeptidase (EP24.15) are closely related metalloendopeptidases. Site-directed mutagenesis of Tyr(613) (EP24.16) or Tyr(612) (EP24.15) to either Phe or Ala promoted a strong reduction of k(cat)/K(M) for both enzymes. These data suggest the importance of both hydroxyl group and aromatic ring at this specific position during substrate hydrolysis by these peptidases. Furthermore, the EP24.15 A607G mutant showed a k(cat)/K(M) of 2x10(5) M(-1) s(-1) for the Abz-GFSIFRQ-EDDnp substrate, similar to that of EP24.16 (k(cat)/K(M)=3x10(5) M(-1) s(-1)) which contains Gly at the corresponding position; the wild type EP24.15 has a k(cat)/K(M) of 2.5x10(4) M(-1) s(-1) for this substrate.     

The influence of dietary fatty acid composition on the respiratory and cardiovascular physiology of Adriatic sturgeon (Acipenser naccarii): a review

This paper reviews evidence that the fatty acid composition of dietary lipids influences the respiratory and cardiovascular physiology of Adriatic sturgeon {Acipenser naccarii) and, thereby, their tolerance of the stress of hypoxia. Sturgeon fed a commercial diet enriched in fish oil (menhaden oil as 15% of dry feed weight), with an elevated content of highly unsaturated fatty acids of the co3 series (ω3 HUFA), had a significantly lower standard metabolic rate (SMR) and routine oxygen consumption (Mo₂) than those fed a diet enriched with the same quantity of hydrogenated coconut oil, with an elevated content of saturated fatty acids (SFA). Both groups grew equally well. As a result of this difference in aerobic metabolism, sturgeon fed the w3 HUFA and SFA responded differently when exposed to hypoxic challenges. Sturgeon fed w3 HUFA exhibited no significant reflex hyperventilation when exposed to mild, moderate or deep hypoxia (30 min at water 0₂ partial pressures of 10.8, 6.6 and 4.6 kPa, respectively), no hypoxic depression of spontaneous activity during 3h in mild hypoxia, and no depression of Mo₂ during 3h in moderate hypoxia, unlike sturgeon fed SFA. The diets also influenced the performance of isolated hearts in vitro. Hearts from fish fed o3 HUFA maintained maximum in vitro cardiac power output unchanged when oxygen supply was reduced (O₂ content from 2.3 to 0.7 vol.%), unlike hearts from sturgeon fed SFA. Overall, the results indicate that dietary fatty acid composition can influence tolerance of hypoxia in sturgeon, through effects on SMR. When compared to sturgeon fed SFA, those fed co3 HUFA had lower SMR and were more tolerant of hypoxia, with effects both on the whole animal and on the isolated heart.     

The metabolism of ethanol-derived acetaldehyde by alcohol dehydrogenase (EC 1.1.1.1) and aldehyde dehydrogenase (EC 1.2.1.3) in Drosophila melanogaster larvae.

Both aldehyde dehydrogenase (ALDH, EC 1.2.1.3) and the aldehyde dehydrogenase activity of alcohol dehydrogenase (ADH, EC 1.1.1.1) were found to coexist in Drosophila melanogaster larvae. The enzymes, however, showed different inhibition patterns with respect to pyrazole, cyanamide and disulphiram. ALDH-1 and ALDH-2 isoenzymes were detected in larvae by electrophoretic methods. Nonetheless, in tracer studies in vivo, more than 75% of the acetaldehyde converted to acetate by the ADH ethanol-degrading pathway appeared to be also catalysed by the ADH enzyme. The larval fat body probably was the major site of this pathway.     

Effects of maturation and acidosis on the chaos-like complexity of the neural respiratory output in the isolated brainstem of the tadpole, Rana esculenta

Human ventilation at rest exhibits mathematical chaos-like complexity that can be described as long-term unpredictability mediated (in whole or in part) by some low-dimensional nonlinear deterministic process. Although various physiological and pathological situations can affect respiratory complexity, the underlying mechanisms remain incompletely elucidated. If such chaos-like complexity is an intrinsic property of central respiratory generators, it should appear or increase when these structures mature or are stimulated. To test this hypothesis, we employed the isolated tadpole brainstem model [Rana (Pelophylax) esculenta] and recorded the neural respiratory output (buccal and lung rhythms) of pre- (n = 8) and postmetamorphic tadpoles (n = 8), at physiologic (7.8) and acidic pH (7.4). We analyzed the root mean square of the cranial nerve V or VII neurograms. Development and acidosis had no effect on buccal period. Lung frequency increased with development (P < 0.0001). It also increased with acidosis, but in postmetamorphic tadpoles only (P < 0.05). The noise-titration technique evidenced low-dimensional nonlinearities in all the postmetamorphic brainstems, at both pH. Chaos-like complexity, assessed through the noise limit, increased from pH 7.8 to pH 7.4 (P < 0.01). In contrast, linear models best fitted the ventilatory rhythm in all but one of the premetamorphic preparations at pH 7.8 (P < 0.005 vs. postmetamorphic) and in four at pH 7.4 (not significant vs. postmetamorphic). Therefore, in a lower vertebrate model, the brainstem respiratory central rhythm generator accounts for ventilatory chaos-like complexity, especially in the postmetamorphic stage and at low pH. According to the ventilatory generators homology theory, this may also be the case in mammals.     

Hepatic respiratory compensation and blood volume in the frog (Rana esculenta)

In the frog, Rana esculenta (L.), the liver can change in volume by over 25%, depending on the respiratory conditions of the animal: in well-oxygenated specimens the organ can hoard about half of the total amount of erythrocytes in its sinusoids, and release them into the bloodstream under conditions of hypoxia. This phenomenon can be observed at a temperature of 6°C by comparing the liver volumes and haematic values of chlorobutanol-anaesthetized animals exposed to the air or submerged in still water (a condition which induces hypoxia): the blood volume remains constant, at about 5 ml per 100g of body weight, but red blood cell count and haematocrit value differ by as much as 50%. At 18°C there is an increase in oxygen demand and in anaesthetized animals, which rely totally on cutaneous respiration, the compensatory liver mechanism can no longer be observed, since all the available erythrocytes are already circulating in a blood volume which, depending on respiratory conditions, can vary between about 7 and 8ml/100g. At 30°C, cutaneous respiration alone does not allow the anaesthetized animals to survive long enough to stabilize their haematic parameters.     

The role of the liver in the cutaneous respiratory compensation of the frog (Rana esculenta)

Experiments on anaesthetized specimens of Rana esculenta (L.) demonstrate that at low temperatures (6°C) the liver of the frog-like the spleen of the newt-regulates cutaneous respiration, storing red blood cells when the animal is well oxygenated and releasing these into circulation under conditions of hypoxia. During the shift from the congested to decongested state, the liver is reduced to about two-thirds of its weight, while the erythrocyte concentration and correlated parameters in the bloodstream can increase by more than 50%. At higher temperatures (18°C) this compensatory mechanism becomes inefficient and the liver oversees the survival of the hypoxic organism for a fairly long period of time (about 5 hours) by releasing glucose for anaerobic glycolysis.     

Daily variations in the effects of disturbance on growth, fattening, and metamorphosis in the bullfrog (Rana catesbeiana) tadpole.

Bullfrog tadpoles subjected to the daily disturbance of water replacement demonstrated differences in the rates of growth and metamorphosis and in fatbody weights which depended on the time of day when water replacement occurred. Early daily disturbances stimulated larval growth whereas midday disturbances stimulated metamorphosis. The time when the daily disturbances caused fattening changed during metamorphosis so that younger tadpoles fattened when disturbed early in the photoperiod and older tadpoles fattened when disturbed at midday.     

The respiratory metabolism of a lizard (Lacerta vivipara) in supercooled and frozen states

We investigated the respiratory metabolism of the overwintering lizard Lacerta vivipara while in either supercooled or frozen states. With a variable pressure and volume microrespirometer and a chromatograph, we show that the oxygen consumption of the supercooled animals showed a nonlinear relationship with temperature and an aerobic metabolism demand between 0.5 and -1.5 degrees C. A significant increase in the respiratory quotient (RQ) values indicated an increasing contribution by the anaerobic pathways with decreasing temperature. In the frozen state, two phases are easily detectable and are probably linked to the ice formation within the body. During the first 5-6 h, the animals showed an oxygen consumption of 3.52 +/- 0.28 microl. g(-1). h(-1) and a RQ value of 0.52 +/- 0.09. In contrast, after ice equilibrium, oxygen consumption decreased sharply (0.55 +/- 0.09 microl. g(-1). h(-1)) and the RQ values increased (2.49 +/- 0.65). The present study confirms the fact that supercooled invertebrates and vertebrates respond differently to subzero temperatures, in terms of aerobic metabolism, and it shows that aerobic metabolism persists under freezing conditions.