Home About us Contact
|
Home About us Contact | ||
|
|
||
Several Fish Species (several + fish_species)
Selected AbstractsHypocretin/orexin in fish physiology with emphasis on zebrafishACTA PHYSIOLOGICA, Issue 3 2010P. Panula Abstract One hypocretin/orexin (hcrt) gene has been identified in several fish species. The first pufferfish gene was identified in 2002 and the zebrafish gene was cloned in 2004. Its structure is very similar to that of mammals, and it encodes for two active peptides with C-termini similar to those of mammals. The gene is expressed in the brain in only one hypothalamic nucleus, which sends projections to the telencephalon, diencephalon, mesencephalon and rhombencephalon. The terminal fibres are found in close contact with many aminergic cell groups, including those of raphe serotonergic, locus coeruleus noradrenergic, several dopaminergic cell groups and the sole histaminergic hypothalamic cluster. One receptor corresponding to mammalian hcrt 2 receptor has been identified in fish. Overexpression of hcrt in zebrafish has been reported to consolidate wakefulness and inhibit rest. On the other hand, fish lacking the hcrt receptor show short and fragmented sleep instead of sleepiness and cataplexy. Food deprivation increases hcrt mRNA expression in zebrafish brain, and intracerebroventricular hcrt peptides stimulate food consumption and feeding behaviour in goldfish. Hcrt peptides thus have important roles in fish physiology. Many genetic and functional methods available render fish, especially zebrafish, a suitable organism to study new aspects of hcrt physiology in vertebrates. [source] Evidence for a widespread involvement of NO in control of photogenesis in bioluminescent fishACTA ZOOLOGICA, Issue 4 2010Jenny Krönström Abstract Krönström, J. and Mallefet, J. 2009. Evidence for a widespread involvement of NO in control of photogenesis in bioluminescent fish. ,Acta Zoologica (Stockholm) 91: 474,483. The presence of nitric oxide synthase (NOS) and nerve fibres in the photophores of seven bioluminescent fish species (Hygophum benoiti, Myctophum punctatum, Electrona risso, Cyclothone braueri, Vinciguerria attenuata, Maurolicus muelleri and Porichthys notatus) with endogenous photocytes, were investigated. Antibodies directed against neuronal and inducible NOS (n and iNOS respectively) and NADPH-diaphorase activity were used to reveal the locations of NOS, while antibodies directed against acetylated tubulin were used to visualize nerve fibres. The nNOS antibody labelled structures in all investigated photophores except in the organs from P. notatus. The photocytes of P. notatus showed NADPH-diaphorase activity. In the myctophid species, NOS-like immunoreactivity was found in small intracellular structures of the photocytes and in nerve fibres reaching the photocytes. nNOS-positive fibres were also found among lens/filter cells in V. attenuata, and in M. muelleri the cytoplasm of lens/filter cells contained NOS-like material. In C. braueri, a cell type located at a collecting chamber for luminous products in the photophore contained NOS-like material. All photophores received an innervation reaching the photocytes, as well as other components including lens/filter areas. The results of this study comply with an involvement of nitric oxide in the control of bioluminescence in several fish species. [source] Assessing the potential for fish predation to impact zebra mussels (Dreissena polymorpha): insight from bioenergetics modelsECOLOGY OF FRESHWATER FISH, Issue 2 2004M. A. Eggleton Abstract,,, Rates of annual food consumption and biomass were modeled for several fish species across representative rivers and lakes in eastern North America. Results were combined to assess the relative potential of fish predation to impact zebra mussels (Dreissena polymorpha). Predicted annual food consumption by fishes in southern waters was over 100% greater than that in northern systems because of warmer annual water temperatures and presumed increases in metabolic demand. Although generally increasing with latitude, biomasses of several key zebra mussel fish predators did not change significantly across latitudes. Biomasses of some less abundant fish predators did increase significantly with latitude, but increases were not of the magnitude to offset predicted decreases in food consumption. Our results generally support the premise that fishes in rivers and lakes of the southern United States (U.S.) have inherently greater potential to impact zebra mussels by predation. Our simulations may provide a partial explanation of why zebra mussel invasions have not been as rapid and widespread in southern U.S. waters compared to the Great Lakes region. Resumen 1Modelamos la tasa de consumo anual de alimento y biomasa para varias especies de peces en una muestra representativa de ríos y lagos del este de Norte América. Combinamos los resultados para evaluar el potencial relativo que estas especies de peces pueden ejercer sobre la abundancia del mejillón asiático Dreissena polymorpha. Las predicciones sobre consumo para peces en lagos y ríos del sur fueron más del 100% comparadas con sistemas septentrionales. Esto se puede deber a las temperaturas anuales más altas y aumentos en la demanda metabólica de peces en ríos y lagos del sur de Norte América. 2La biomasa de varias especies claves de peces que consumen D. polymorpha no cambió apreciablemente con latitud. La biomasa de algunos peces que consumen D. polymorpha aumentó significativamente con latitud, pero este aumento no era de una magnitud suficiente para compensar la disminución en el consumo de alimento. 3Nuestros resultados apoyan generalmente la premisa de que los peces en ríos y lagos del sur de los Estados Unidos (EE.UU.) tienen un potencial inherente mayor para poder controlar D. polymorpha. Nuestras simulaciones proporcionan una explicación parcial de por qué las invasiones de D. polymorpha no han sido tan rápidas y ampliamente distribuidas en aguas sureñas comparado con la región de los Grandes Lagos. [source] Effects of ultraviolet radiation on the eggs of landlocked Galaxias maculatus (Galaxiidae, Pisces) in northwestern PatagoniaFRESHWATER BIOLOGY, Issue 3 2000M. Battini Summary 1Ultraviolet radiation (UVR) damages early life stages of several fish species. Galaxias maculatus is a small catadromous fish, with landlocked forms occurring in many lakes within the Nahuel Huapi National Park (Patagonia, Argentina). In this work, the vulnerability of G. maculatus eggs exposed to both natural and artificial UVR was investigated in relation to water transparency. 2Field experiments were performed in two lakes differing in UVR attenuation. Galaxias maculatus eggs were exposed to in situ levels of UVR in quartz tubes incubated at various depths. For laboratory experiments, the eggs were exposed to five levels of artificial UVB radiation. 3Exposure to natural UVR causes various degrees of egg mortality depending on water transparency and incubation depth. In the less transparent lake (Kd320 = 3.08 m -1), almost complete mortality was observed near the surface. At a depth of 43 cm the observed mortality was only 22%, but was still significantly different from the dark control. In the most transparent lake (Kd320 = 0.438 m -1), almost total mortality was observed in tubes incubated at 2.56 m or shallower. A gradual decline in mortality was recorded from that depth to 3.78 m where the values approached those in the dark control treatments. 4A monotonic relationship between mortality and UV exposure could be observed both in field and laboratory experiments. Using the results from field incubations, a LD50 of 2.5 J cm -2 nm -1 was estimated. In a few mountain lakes, this value would be exceeded even if the eggs were laid at the maximum depth of the lake. Thus UVR seems a sufficient cause to explain the absence of G. maculatus populations in some mountain lakes. For most lakes, however, UVR is probably one of several important environmental factors, which together determine the habitat suitability. [source] The significance of vitamin D for fish: a reviewAQUACULTURE NUTRITION, Issue 1 2010E.-J. LOCK Abstract Fish store large quantities of vitamin D in their liver and fat tissues, including the fat associated with muscle, and this makes fish an important dietary source of vitamin D. Fish do not synthesize vitamin D and are fully dependent on dietary sources to meet their requirement. Under natural circumstances planktonic vitamin D accumulates in the aquatic food chain. In aquaculture, formulated diets are used and vitamin D intake can be manipulated. The minimum dietary requirement for vitamin D has been established in several fish species. The role of vitamin D in fish physiology is still enigmatic. Till the 1970s there was consensus that fish accumulate but not metabolize vitamin D. There is substantial evidence now, four decades later, that fish have a vitamin D endocrine system with similar functions as in mammals. We here summarize the major characteristics of the fish vitamin D endocrine system. The hydroxylation of vitamin D to more polar metabolites, their plasma levels and protein-bound transport in blood plasma will be discussed. The vitamin D receptor profile, receptor distribution and responses to vitamin D are reviewed for the key target tissues (gill, intestine, kidney and bone). We will address the classical slower actions through transcription factors as well as the faster G-protein coupled (membrane) receptor mediated effects. We then review the dietary requirement of vitamin D in aquaculture and address some lesser known functions of the vitamin D endocrine system. [source] | ||||||||||