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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For wild, sea-run brown trout (Salmo trutta) smolts, the physiological consequences of abrupt transfer to seawater and simultaneous challenge with copepodid larvae of the sea louse, Lepeophtheirus salmonis (Krøyer, 1837), were investigated in the laboratory. Analysis of osmoregulatory, metabolic, and stress markers allowed the derivation of a sublethal threshold burden of L. salmonis, above which the host suffers major physiological stress. Noticeable lice effects, consistent across all measured markers, were not observed until L. salmonis developed to the mobile preadult and adult stages. Preadult L. salmonis caused significant increases in plasma chloride, osmolality, glucose, lactate, and cortisol and a significant reduction in haematocrit. Piecewise linear statistical approaches allowed the determination of abrupt changes in these physiological markers, attributable to the intensity of L. salmonis infestation on individual fish, and identification of overall threshold lice burdens. Thirteen mobile lice·fish–1 (weight range 19–70 g) was a consistent breakpoint across several physiological measures. This information will provide a valuable, objectively derived tool to aid in the formulation of effective wild fisheries management policy concerning S. trutta conservation.

In euryhaline teleosts, osmoregulation is a fundamental and dynamic process that is essential for the maintenance of ion and water balance, especially when fish migrate between fresh water (FW) and sea water (SW) environments. The European eel has proved to be an excellent model species to study the molecular and physiological adaptations associated with this osmoregulatory plasticity. The life cycle of the European eel includes two migratory periods, the second being the migration of FW eels back to the Sargasso Sea for reproduction. Various anatomical and physiological changes allow the successful transition to SW. The aim of this study was to use a microarray approach to screen the osmoregulatory tissues of the eel for changes in gene expression following acclimation to SW. Tissues were sampled from fish at selected intervals over a 5-mo period following FW/SW transfer, and RNA was isolated. Suppressive subtractive hybridization was used for enrichment of differentially expressed genes. Microarrays comprising 6,144 cDNAs from brain, gill, intestine, and kidney libraries were hybridized with appropriate targets and analyzed; 229 differentially expressed clones with unique sequences were identified. These clones represented the sequences for 95 known genes, with the remaining sequences (59%) being unknown. The results of the microarray analysis were validated by quantification of 28 differentially expressed genes by Northern blotting. A number of the differentially expressed genes were already known to be involved in osmoregulation, but the functional roles of many others, not normally associated with ion or water transport, remain to be characterized.

Complementary DNAs encoding homologs of the mammalian aquaglyceroporins (termed AQPe) and aquaporin-1 isoforms (termed AQP1) were isolated from the European eel. The AQP amino acid sequences share 35-54% identity with other known human AQPs. Although AQPe mRNA expression was approximately equivalent along the entire length of the gut, AQP1 expression was the highest in the posterior/rectal segment. Seawater (SW) acclimation increased AQP1 mRNA abundance by 5-and 17-fold in the anterior, 14-and 23-fold in the mid-, and 9-and 7-fold in the posterior/rectal gut regions of yellow and silver eels, respectively. SW acclimation had an effect on AQPe mRNA expression only in the midintestine of silver eels, where a small but significant 1.7-fold increase in abundance was measured. Western blots using an eel AQP1-specific antibody identified the presence of a major immunoreactive 28-kDa protein, primarily within the posterior/rectal segment. A 3-wk SW transfer induced an increase in AQP1 protein abundance in all intestinal segments, with the posterior/rectal region still expressing protein levels ϳ40-and 8-fold higher than the anterior and midsegments, respectively. Strong AQP1 immunofluorescence was detected within the vascular endothelium in both freshwater (FW)-and SW-acclimated eels and in the epithelial apical brush border in the posterior/ rectal gut regions of SW-acclimated eels. Cortisol infusion into FW eels had no effect on intestinal AQPe mRNA expression but induced increases in AQP1 mRNA and protein levels. These results provide evidence for the presence of a SW-induced and steroid-regulated AQP water channel pathway within the intestine of the European eel.Anguilla anguilla; gastrointestinal tract; AQP1; AQPe; corticosteroid WHEN FACED WITH EXTERNAL ENVIRONMENTS of varying salinity, euryhaline teleosts, such as the European eel (Anguilla anguilla), have a fundamental osmoregulatory problem: the maintenance of their body fluid composition and osmolality. Osmoregulation is achieved by linked ion and water transport in the gill, kidney, gastrointestinal tract, and urinary bladder (15). The intestine is a major osmoregulatory organ in euryhaline teleost fish, especially when acclimated to seawater (SW). When transferred to the marine environment, euryhaline fish such as the European eel increase their drinking rate by Ͼ10-fold and the ingested SW is mainly desalinated, first within the esophagus, possibly by passive ion diffusion, and thereafter along the entire length of the intestine, by active transport of monovalent ions into the blood. The subsequent water absorption is considered to take place in the intestine by osmotic mechanisms after active absorption of the monovalent ions, the "solute-linked water flow" pathway (52). The magnitude of water fluxes across various parts of the intestine has also been determined, with highest levels occurring in the midregion followed in descending order by the posterior and anterior intestine and rectum (5, 9).Although intestinal salt and water transporters are central t...