Early warming stress on rainbow trout juveniles impairs male reproduction but contrastingly elicits intergenerational thermotolerance.

The exposure of adult fish to warm or high temperatures is known to impair reproduction, yet the long-term reproductive impacts for treatments at early life are not well clarified. This study aimed to evaluate the effects of warm temperature (WT) during juvenile stage on gonad maturation, gamete quality, and offspring thermotolerance in rainbow trout. While the comparison of basic reproductive parameters in WT females did not reveal any kind of impairment, many WT males showed an atrophied, undeveloped gonad, or a smaller testis with lower milt volume; sperm quality parameters in WT males and deformity rates in the respective progeny were also highly affected. However, despite of such negative effects, many of the remaining progeny presented better rates of survival and growth when exposed to the same conditions as those of parental fish (WT), suggesting that thermal stress in parr stage males elicited intergenerational thermotolerance after a single generation. The present results support that prolonged warming stress during early life stages can adversely affect key reproductive aspects, but contrastingly increase offspring performance at upper thermal ranges. These findings have implications on the capacity of fish to adapt and to cope with global warming.

Trophic interference by Salmo trutta on Aplochiton zebra and Aplochiton taeniatus in southern Patagonian lakes.

The length and mass ratio, diet and isotopic composition of Aplochiton zebra and Aplochiton taeniatus inhabiting a Salmo trutta-invaded and a S. trutta-free lake in southern Patagonia were compared. Results indicate that S. trutta exercises important trophic interference over A. zebra and A. taeniatus, causing changes in their dietary composition by reducing the consumption of winged Diptera through changes in feeding behaviours that involve jumping out of the water. This effect is significantly higher in A. zebra than in A. taeniatus a species that has a highly specialized diet. The dietary changes of A. zebra and A. taeniatus in sympatry with S. trutta lead to an impoverishment of their isotopic nitrogen signals (δ(15)N), suggesting a reduction of their trophic position. In the case of A. zebra, this translates into a significant decrease in its body condition factor. Such interference could lead to a population decline of this species and would explain the current distribution range decline and allopatry with S. trutta in fluvial systems.

Spinosad toxicity to Simulium spp. larvae and associated aquatic biota in a coffee-growing region of Veracruz State, Mexico.

Spinosad is a naturally derived insecticide that has shown potential as a mosquito larvicide. To determine the activity of spinosad against blackflies, late-instar larvae from a community comprising Simulium triittatum (63.6%) and seven other species, including three known vectors of onchocerciasis in Mexico (S. metallicum, S. ochraceum, and S. callidum), were subjected to concentration-mortality laboratory bioassays following World Health Organization guidelines. Cephalic capsule measurements confirmed the relatively homogeneous distribution of experimental larvae. The 50% lethal concentration of spinosad was estimated at 1.48 ppm spinosad (95% confidence interval: 1.07-2.33) for a 10-min exposure period, whereas larvae treated with 0.05 ppm of the organophosphate temephos experienced 61% mortality. Immature aquatic insects were identified to genus and tested for their susceptibility to spinosad in the laboratory. After exposure to 12 ppm spinosad for 10 min, ephemeropterans, odonates, trichopterans, and hemipterans did not experience significantly increased mortality over that of untreated controls, whereas a significant increase in mortality was observed in spinosad-treated Plecoptera (P < 0.001). Tilapia and trout fry exposed to 12 ppm spinosad for 10 min did not experience increased mortality at 24-h postexposure over that of the controls. We conclude that spinosad is less toxic than temephos to these blackfly species, but is likely to have a low impact on nontarget members of the aquatic community.

Characterization of manures from fish cage farming in Chile.

This study aims to characterize salmonid manures and to determine their potential use in agricultural soils. Sampling was carried out below salmon and trout cages in farms located in lakes and in the sea in the South of Chile during 2002-2003. Manure was analyzed for macronutrients, micronutrients and heavy metals. Results showed a high variability between samples and differences between sea and lake manure. Dry matter contents were low averaging c. 12-15%. Manures showed low OM contents with values

Oogenesis and plasma levels of sex steroids in cultured females of brown trout (Salmo trutta linnaeus, 1758) in Chile.

Naturalized brown trout populations in Chile are a valuable genetic resource with aquaculture potential. The oogenesis of a three-year-old brown trout cultured population was studied in southern Chile. Gonadosomatic index (GSI), oocyte growth, gonadal microscopic characteristics, and plasma levels of estradiol-17beta (E2), testosterone (T), and 17alpha-hydroxyprogesterone (17alpha-HP) were measured bimonthly for a nine-month period before spawning. The maximum GSI level (22%) was similar to that described for other salmonids, although it was reached in May, more than one month before the population started spawning. Oocyte growth increases strongly from January when diameter reaches more than 1 mm. The vitellogenic period (six-seven months) is consistent with the long vitellogenesis, described for salmonid females maturing at three years old. E2 shows a slow increase from November, reaching its peak value in March (65.2+/-0.7 ng/ml), during maximal vitellogenic activity. T increases as oogenesis progresses, reaching a maximum of 90+/-20 ng/ml during May, and falling considerably during ovulation. Following a typical pattern of progestogens in salmonid oogenesis, 17alpha-HP stays at basal levels during most of oogenesis, but experiences a strong surge (2.0+/-0.4 ng/ml) just before ovulation.

Volumetric and ionic responses of goldfish hepatocytes to anisotonic exposure and energetic limitation.

The relationship between cell volume and K(+) transmembrane fluxes of goldfish (Carassius auratus) hepatocytes exposed to anisotonic conditions or energetic limitation was studied and compared with the response of hepatocytes from trout (Oncorhynchus mykiss) and rat (Rattus rattus). Cell volume was studied by video- and fluorescence microscopy, while K(+) fluxes were assessed by measuring unidirectional (86)Rb(+) fluxes. In trout and rat hepatocytes, hyposmotic (180 mosmoll(-1)) exposure at pH 7.45 caused cell swelling followed by a regulatory volume decrease (RVD), a response reported to be mediated by net efflux of KCl and osmotically obliged water. By contrast, goldfish hepatocytes swelled but showed no RVD under these conditions. Although in goldfish hepatocytes a net ((86)Rb(+))K(+) efflux could be activated by N-ethylmaleimide, this flux was not, or only partially, activated by hyposmotic swelling (120-180 mosmoll(-1)). Blockage of glycolysis by iodoacetic acid (IAA) did not alter cell volume in goldfish hepatocytes, whereas in the presence of cyanide (CN(-)), an inhibitor of oxidative phosphorylation, or CN(-) plus IAA (CN(-)+IAA), cell volume decreased by 3-7%. Although in goldfish hepatocytes, energetic limitation had no effect on ((86)Rb(+))K(+) efflux, ((86)Rb(+))K(+) influx decreased by 57-66% in the presence of CN(-) and CN(-)+IAA but was not significantly altered by IAA alone. Intracellular K(+) loss after 20 min of exposure to CN(-) and CN(-)+IAA amounted to only 3% of the total intracellular K(+). Collectively, these observations suggest that goldfish hepatocytes, unlike hepatocytes of anoxia-intolerant species, avoid a decoupling of transmembrane K(+) fluxes in response to an osmotic challenge. This may underlie both the inability of swollen cells to undergo RVD but also the capability of anoxic cells to maintain intracellular K(+) concentrations that are almost unaltered, thereby prolonging cell survival.

Further observations on cerebellar climbing fibers. A study by means of light microscopy, confocal laser scanning microscopy and scanning and transmission electron microscopy

The intracortical pathways of climbing fibers were traced in several vertebrate cerebella using light microscopy, confocal laser scanning microscopy, scanning and transmission electron microscopy. They were identified as fine fibers up to 1(micron thick, with a characteristic crossing-over bifurcation pattern. Climbing fiber collaterals were tridimensionally visualized forming thin climbing fiber glomeruli in the granular layer. Confocal laser scanning microscopy revealed three types of collateral processes at the interface between granular and Purkinje cell layers. Scanning electron microscopy showed climbing fiber retrograde collaterals in the molecular layer. Asymmetric synaptic contacts of climbing fibers with Purkinje dendritic spines and stellate neuron dendrites were characterized by transmission electron microscopy. Correlative microscopy allowed us to obtain the basic three-dimensional morphological features of climbing fibers in several vertebrates and to show with more accuracy a higher degree of lateral collateralization of these fibers within the cerebellar cortex. The correlative microscopy approach provides new views in the cerebellar cortex information processing.(AU)

Comparative uptake, bioaccumulation, and gill damages of inorganic mercury in tropical and nordic freshwater fish.

This paper reports comparative results on the bioaccumulation of inorganic mercury and resulting gill damages in the tropical fish, Trichomycterus zonatus, and a nordic species, Salvelinus alpinus, using radioisotope 203Hg techniques and scanning electron microscopy. Uptake of inorganic Hg from water was much more important in T. zonatus than in S. alpinus and the Hg concentration in S. alpinus increased at a slower rate in all tissues during the first 24 h of exposure. After 96 h, Hg concentration was 70 times higher in the kidney, 10 times higher in liver, intestine, skin, and brain, and 3 times higher in gills, muscle, and the rest of body of T. zonatus compared to S. alpinus. Gill damages in T. zonatus were more evident and occurred much earlier than for S. alpinus. According to our data, the high differences observed in the inorganic mercury uptake, bioaccumulation, and gills damages strongly suggest that T. zonatus is more sensitive to inorganic mercury pollution than S. alpinus. Further studies are urgently needed to determine whether the high sensitivity observed for T. zonatus to inorganic Hg is also present in the majority of tropical species or whether this species presents an isolated case.

Further observations on cerebellar climbing fibers. A study by means of light microscopy, confocal laser scanning microscopy and scanning and transmission electron microscopy.

The intracortical pathways of climbing fibers were traced in several vertebrate cerebella using light microscopy, confocal laser scanning microscopy, scanning and transmission electron microscopy. They were identified as fine fibers up to 1(micron thick, with a characteristic crossing-over bifurcation pattern. Climbing fiber collaterals were tridimensionally visualized forming thin climbing fiber glomeruli in the granular layer. Confocal laser scanning microscopy revealed three types of collateral processes at the interface between granular and Purkinje cell layers. Scanning electron microscopy showed climbing fiber retrograde collaterals in the molecular layer. Asymmetric synaptic contacts of climbing fibers with Purkinje dendritic spines and stellate neuron dendrites were characterized by transmission electron microscopy. Correlative microscopy allowed us to obtain the basic three-dimensional morphological features of climbing fibers in several vertebrates and to show with more accuracy a higher degree of lateral collateralization of these fibers within the cerebellar cortex. The correlative microscopy approach provides new views in the cerebellar cortex information processing.

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