Authors: A. Zilber, D.N. Popper And Y. Yom-tov

Abstract: The effect of stocking density, origin of eggs and water flow regime on growth, survival and body condition of young Nile crocodiles was studied. No adverse effects of high densities, up to 15 animals/m1 was found. Animals hatched from eggs collected in nature had a slight advantage in growth. All tested parameters had no effect on survival, apart from increased mortality of 4-8 month old crocodiles kept at high density during their first cold season. Continuous water flow did not improve growth. Practical implications of these results are discussed.

Authors: Aurora M. Castilla And Dirk Bauwens

Abstract: We studied habitat selection by Lacerta lepida in an open. degraded Mediterranean Quercus ilex-forest using two different methods. First, the frequency of lizard observations in distinct habitat types was compared with habitat availability. Although lizards were seen in a wide range of habitats. a preference for sites with a complex vertical vegetation structure was evident. We also quantified structural features of the habitat at sighting spots of adult lizards. Both univariate and multivariate analyses indicated that lizards preferred sites with a relatively high coverage of high (> 2 m) vegetation, but with some low ( <50 cm) vegetation, and where some rocks were present.

Authors: Mario Diaz And Antonio Lorenzo

Abstract: Plasma concentrations of aldosterone, sodium and potassium were measured in the lizard, Gallotia galloti. Aldosterone concentrations in control animals were 29.48 ± 8.65 ng/dl, which falls within the range reported for this hormone in mammals. Peripheral sodium and potassium concentrations were 1 32.81 .± 2.28 and 5.77 ± 0.32 meq/I, respectively. Plasma aldosterone and sodium were negatively correlated. A positive relationship could be established between potassium concentration and aldosterone levels. Acute or chronic administration of exogenous aldosterone increased the circulating levels of this hormone, being maximal in chronically treated animals. However, although plasma concentrations of aldosterone were augmented by acute administration, the sodium concentration in the plasma was only elevated by chronic treatment. No further changes to potassium concentration could be observed under primary hyperaldosteronism conditions. The extent to which aldosterone may be implicated in the regulation of sodium and potassium transport in reptiles and its possible action on postrenal structures of electrolyte transport are discussed.

Authors: Ad. Padhye And H.V. Ghate

Abstract: Short term effects of different concentrations of NaCl and KCl on embryos and tadpoles of the frog Microhyla ornata were studied. Both NaCl and KCl caused significant reduction in swelling of the perivitelline space (PVS), an effect very similar to that reported for acidic pH. Tadpoles were observed to be somewhat more resistant to both NaCl as well as KC!, as compared to the embryos. KCl was found to be more toxic than NaCl. A typical teratogenic effect was observed in KC! treated embryos which showed swollen head coelom, whereas NaCl caused incomplete closure of the neural tube.

Authors: Eliezer Frankenberg And Yehudah L. Werner

Abstract: We provide data on the fecundity of locally common Israeli reptiles, and use these data to examine current ideas on the reproductive ecology of lizards. Our methodology was selected in consideration of the acute problems of nature conservation in Israel. In the museum collections of the Hebrew University of Jerusalem and Tel Aviv University we used radiography to locate the shelled oviductal eggs of 164 female lizards. belonging to eleven species (Agamidae and Lacertidae). Each sample sums the species· variation over its range and over different years. Female body size. egg number and egg volume were determined. Specific clutch volumes. relative to maternal body lengths. resembled those reported in iguanid lizards from tropical America. Clutch size varied intraspecifically and. in most species, correlated to maternal size. In others, egg size was more influenced by maternal size. We argue that the latter species oviposit in more stable environments than do the majority.

Authors: Anna Pecio

Abstract: Female smooth newts begin egg deposition in spring after hibernation even if they have not been inseminated. All these eggs are unfertilized. This indicates that the sperm from the previous years are either not retained in the seminal receptacles or are incapable of fertilization. A large proportion of females do not lose receptivity after the first insemination and may collect several spermatophores during the egg-deposition period. There seems to be a positive correlation between the number of eggs deposited and the number of spermatophores transferred.

Authors: H.I. Griffiths And D.H. Thomas

Abstract: The Mexican axolotl, Ambystoma mexicanum is an aquatic-phase oxygen conformer with a close correlation between rates of aquatic oxygen consumption and aquatic oxygen tension. Rates of oxygen consumption at normoxic oxygen tensions were 1 8.2µ1 02.g·1.h-1 at 20°C and 1 3.8µ.I 02.g-1.h-1 at 30°C. Air-breathing (i.e. rising to the water surface to gulp air) increases in hypoxia, associated with a decrease in gill ventilatory movements. Therefore, oxygen compensation during aquatic hypoxia appears to occur in the aerial phase, whilst aquatic gas-exchange surfaces show little ability to compensate for changes in ambient oxygen tension.