The interaction between O2 and CO2 movements during aerobic exercise in fish

In resting rainbow trout, 99 per cent of the total CO2 excreted across the gills consisted of bicarbonate (HCO3-) dehydrated to CO2 in the red cell. This value decreased to 93 percent during exercise, the remainder being excreted as molecular CO2 which existed in the pre-branchial blood. HCO3- dehydration consumes a proton which can be supplied from hemoglobin (1-1b) through its buffer capacity or the Haldane effect. Bohr proton release from Hb upon oxygenation is maximal between 50 and 100 percent of Hb saturation, consistent with observations made in tench blood. At low swimming speeds, when venous blood 02 content (CvO2) was high, there was a small but insignificant acidosis as blood passed through the gills, indicating a greater release of protons than could be consumed by HCO3-. At higher swimming speeds, when CvO2 was low, there was a significant alkalosis in the arterial blood relative to the venous blood, indicating that fewer protons were released upon oxygenation than HCO3- ions were dehydrated to CO2. The disproportionate release of Bohr protons over the range of Hb-O2 saturation in the blood at the gills limits HCO3- dehydration during greater work loads, conserving the HCO3- buffer capacity of the blood and tissues.

Cardiovascular effects of adrenomedullin in teleost fishes

Adrenomedullin is a fifty-two-amino acid polypeptide that was first discovered in pheochromocytoma cells, and later in the normal adrenal medullae, lungs, kidneys, and blood. In mammals, adrenomedullin has vasodepressive effects, mainly by decreasing peripheral vascular resistance. I investigated the effects of adrenomedullin in fish to see if this novel neuropeptide would have an effect in lower vertebrates, or if its actions were limited to the higher vertebrates. Bolus injections of adrenomedullin resulted in a reduction of heart rate and dorsal aortic pressure in the rainbow trout Oncorhynchus mykiss. However, adrenomedullin had no effect in the Atlantic cod, Gadus morhua. The effects of adrenomedullin in trout appear to be due to a direct action on the peripheral vasculature, as pre-treatment of celiac artery strips with tetrodotoxin had no effect on the ability of adrenomedullin to relax the strip.

Habitos alimenticios de la trucha arco iris, Salmo gairdnerii, Richardson 1836, en el embalse de Agua Fria, Edo. Miranda, Venezuela / Food habits of the rainbow trout, Salmo gairdnerii, Richardson 1836, in the reservoir of Agua Fria, Miranda State, Venezuela

Se estudiaron los hábitos alimenticios de Salmo gairdnerii (216 ejemplares) en un embalse tropical oligotrófico situado a 1720 m.s.n.m. y en dos quebradas afluentes al mismo. Los organismos más importantes en la dieta de las truchas del embalse fueron: larvas de insectos acuáticos )Odonata, Chironomidae y Corixidae), microcrustaceos (Cladocera y Ostracoda) y caracoles (Physidae). En las quebradas predominaron las larvas de Chiromidae y Simuliidae. Se encontró diferencia estadística significativa en la alimentación de las truchas del embalse entre la época de sequía y lluvias, esta diferencia no se manifestó en las quebradas. En la dieta se produjeron cambios con el desarrollo de la struchas. El ancho de nicho trófico en el embalse fue mayor que en las quebradas debido a una mayor equidad. Los valores de superposición de nicho resultaron más altos en las quebradas que en el embalse