Good-genes hypotheses of sexual selection predict that offspring fathered by preferred males should have increased viability resulting from superior genetic quality. Several studies of birds have reported findings consistent with this prediction, but maternal effects are an important confounding variable. Those studies that have attempted to control for maternal effects have only considered differential maternal investment after egg laying. However, female birds differentially deposit testosterone in the eggs, and this influences the development of the chick. This study shows that female birds deposit higher amounts of testosterone and 5alpha-dihydrotestosterone in their eggs when mated to more attractive males.

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Development of an in situ perfused kidney preparation for elasmobranch fish: action of arginine vasotocin. Am J Physiol Regulatory Integrative Comp Physiol 282: R1636-R1642, 2002 10.1152/ajpregu.00810.2000.-Acclimation of the European lesser-spotted dogfish Scyliorhinus canicula to reduced environmental salinity [85-70% seawater (SW)] induced a significant diuresis in addition to a significant decrease in plasma osmolality in vivo. The threshold for this diuresis was determined to be 85% SW. Therefore, S. canicula acclimated to 85% SW was selected for further study as a diuretic model in the development of an in situ perfused kidney preparation. The renal role of arginine vasotocin (AVT) in the in situ perfused trunk preparation was investigated. In SW, perfusion of 10 Ϫ9 and 10 Ϫ10 M AVT resulted in a glomerular antidiuresis and decreases in tubular transport maxima for glucose and perfusate flow. In 85% SW, 10 Ϫ10 M AVT had no significant effect on these renal parameters with the exception of transport maxima for glucose and perfusate flow. Tubular parameters remained unchanged by either 10 Ϫ9 or 10 Ϫ10 M AVT. The results demonstrate that the perfused kidney preparation was a viable tool for the investigation of renal parameters in elasmobranch fish and that AVT induced a glomerular antidiuresis.antidiuresis; seawater; Scyliorhinus canicula; dogfish; neurohypophysial hormones MARINE ELASMOBRANCHS MAINTAIN their plasma isoosmotic or slightly hyperosmotic to that of the surrounding environment, primarily due to the retention of urea (22). Plasma sodium and chloride concentrations are generally higher than those found in marine teleosts, but the fish still face a continuous influx of NaCl across semipermeable membranes, particularly the gills (18,20). Due to the plasma iso/hyperosmolality, some influx of water will occur and urea will be lost to the environment across permeable surfaces, along a concentration gradient. Elasmobranchs are not capable of producing a hyperosmotic urine with respect to body fluids, and the kidneys are not the major site of NaCl excretion (17). It appears that renal retention of urea may be a more important function for the kidney in elasmobranch fish (7).Arginine vasotocin (AVT), a homologue of arginine vasopressin (AVP) in mammals, is the major neurohypophysial peptide in lower vertebrates. It has been characterized in all elasmobranchs examined to date (1, 2). In addition to AVT, the European lesserspotted dogfish Scyliorhinus canicula also has the oxytocinlike peptides, phasvatocin and asvatocin, which occur in roughly equal molar amounts in the pituitary (13). AVT is also present in the pituitary in a proportional amount that is lower by about a factor of 20 (13). This low pituitary level was thought to reflect a permanent secretion of AVT (2). Although accurate levels of AVT have been measured in teleosts, the presence of additional neurohypophysial peptides in elasmobranchs and the potential for these to cross-react with the antiserum have meant that it has not been possible at...

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A technique using 51 chromium-labelled erythrocytes was used to measure blood volume in Scyliorhinus canicula following long-term and acute salinity transfers. Basal whole-blood volume was 5Á6 AE 0Á2 ml 100 g À1 (mean AE S.E.), this increased (6Á3 AE 0Á2 ml 100 g À1 ) following þ14 day acclimation to 80% sea water (SW) and decreased (4Á6 AE 0Á2 ml 100 g À1 ) following acclimation to 120% SW. These changes were shown to be primarily due to changes in plasma volume, with no significant changes in extrapolated red-cell volume being demonstrated. Blood volume was also measured in the same animals during 10 h acute transfer to 100% SW. Plasma volume in S. canicula during acclimation from 80% SW was significantly reduced (4Á5 AE 0Á3 ml 100 g À1 ) after 6 h of transfer to 100% SW. Blood volume in animals during acclimation from 120% SW was significantly increased (4Á8 AE 0Á2 ml 100 g À1 ) after 4 h of acute transfer. The osmoregulatory implications of these different timeframes during hyposaline and hypersaline transfer are discussed, along with the importance of this in vivo technique as context for in vitro studies with haemo-dynamic stimuli.

The existence of an intrarenal renin‐angiotensin system (RAS) in a perfused European lesser‐spotted dogfish Scyliorhinus canicula trunk preparation was examined by the inhibition of angiotensin‐converting enzyme by captopril. This resulted in a glomerular diuresis, an increase in urea and chloride clearance and excretion, and an increase in transport maxima for glucose. It is proposed that these results suggest the presence of an intrarenal RAS.