Loading...
4 results
Search Results
Now showing 1 - 4 of 4
- Potential fecundity of twaite shad Alosa fallax fallax (Pisces: Clupeidae) from the upper estuary of the river Mira (SW Portugal): preliminary resultsPublication . Pina, Teresa; Esteves, Eduardo; Coelho, M.L.; Andrade, José Pedro AndradeThe great majority of European anadromous fishes are threatened species (Leleck, 1980). Despite the existing legal protection for migration fishes, these are vulnerable and particulary threatened by antropogenic impact, by physical obstacles for migrating fish and by physical impacts on spawning and nursery areas.
- Diel variation of fish eggs and larvae in two Portuguese estuaries (rivers Mira and Guadiana)Publication . Esteves, Eduardo; Coelho, M.L.; Pina, Teresa; Andrade, José Pedro AndradeThe importance of estuaries as fish nurseries areas has been well documented. Several studies have indicated that a variety of factors, both abiotic and biotic, influence the distribution of fish species in a estuary (Robinson & Bain, 1989).
- Excitation–contraction coupling reflects the metabolic profile of mantle muscle in young cuttlefishPublication . Callaghan, Neal I.; Ducros, Loïck; Bennett, J. Craig; Capaz, Juan Carlos; Andrade, José Pedro Andrade; Sykes, António; Driedzic, William R.; Lamarre, Simon G.; MacCormack, Tyson J.The mantle muscle of common cuttlefish, Sepia officinalis, is responsible both for high-magnitude and rapid movements for locomotion, as well as sustained ventilation, which require specific metabolic, electrophysiological, and structural organization. Young cuttlefish have a highly oxidative phenotype and a rapid growth rate. Here, we show high rates of oxygen consumption and protein synthesis in juveniles, and these rates decay exponentially over the first few weeks of growth. This is associated with considerable citrate synthase activity (relative to larger cuttlefish) but a lack of glucose metabolism based on zero uptake of glucose by isolated muscle sheets and minimal activity of hexokinase (similar to larger animals). In contrast to glucose metabolism in the heart, glucose metabolism in these muscle sheets was not stimulated by extracellular taurine. Previous research revealed an unusual ion channel complement in mantle myocytes, the most notable feature of which is the lack of a Na+ current during depolarization. Because this adaptation is not consistent across the coleoid clade, we investigated excitation-contraction coupling. Here, mantle energetics and contractility, including the individual components of the total Ca2+ flux driving contraction, were studied. Results indicate that the majority of Ca2+ current underlying contractile stress development capacity in cuttlefish juveniles is not mediated by dihydropyridine-sensitive L-type channels, in contrast to their adult counterparts, and the sarcoplasmic reticulum contributes little to routine contractility. We had previously noted an influence of physiological levels of taurine in limiting cardiac contractility but found no analogous sensitivity in mantle muscle. Finally, transmission electron microscopy of subcellular architecture revealed the presence of sarcoplasmic tubular aggregates, suggesting that oxidative inhibition of sarcoplasmic reticulum function limits its role in this life stage.
- Replacement of fish meal with crustacean meals in diets for long-snouted seahorse, hippocampus guttulatus: digestibility and growth performancePublication . Palma, Jorge; Correia, Miguel; Andrade, José Pedro Andrade; Bureau, DominiqueThis study investigated the effect of partially replacing fish meal with krill and copepod meals in inert diets co-fed with shrimp on the growth and nutrient digestibility of long-snout seahorses (Hippocampus guttulatus). A control diet (Diet 1) using raw starch and four experimental diets with similar protein (approximate to 44.8%) and energy (approximate to 15.1 MJ/kg) levels were tested. Diet 2 used fish meal as the sole protein source, while in Diets 3-5, krill and copepod meals replaced 44% of the fish meal. Seahorses fed shrimp + Diets 2-5 showed significantly higher growth rates (p < 0.05) than those fed shrimp + Diet 1, though there were no significant growth differences among Diets 2-5. Digestibility of dry matter (46.1% to 72.2%), lipids (73.3% to 85.5%), crude protein (89.8% to 95.8%), energy (82% to 92.2%), and phosphorus (28.7% to 64.4%) varied with diet, being consistently lower in seahorses fed shrimp + Diet 1. As an agastric species, H. guttulatus did not exhibit impaired digestibility for any of the tested nutrients, minerals, or energy. This study suggests that crustacean meals can effectively substitute fish meal in inert diets for this species, contributing to the sustainability and optimization of captive seahorse husbandry practices.