Effects of snout dimensions on the hydrodynamics of suction feeding in juvenile and adult seahorses

Seahorses give birth to juveniles having a fully functional feeding apparatus, and juvenile feeding behaviour shows striking similarities to that of adults. However, a significant allometric growth of the snout is observed during which the snout shape changes from relatively short and broad in juveniles to relatively long and slender in adults. Since the shape of the buccal cavity is a critical determinant of the suction performance, this snout allometry will inevitably affect the suction feeding ability. To test whether the snout is optimised for suction feeding throughout an ontogeny, we simulated the expansion of different snout shapes varying from extremely long and slender to short and broad for juvenile and adult snout sizes, using computational fluid dynamic models. Our results showed that the snout diameter at the start of the simulations is involved in a trade-off between the realizable suction volume and expansion time on the one hand (improving with larger initial diameters), and maximal flow velocity on the other hand (improving with smaller initial diameters). Moreover suction performance (suction volume as well as maximal attainable flow velocity) increased with decreasing snout length. However, an increase in snout length decreases the time to reach the prey by the cranial rotation, which may explain the prevalence of long snouts among syngnathid fishes despite the reduced suction performance. Thus, the design of the seahorse snout revolves around a trade-off between the ability to generate high-volume suction versus minimisation of the time needed to reach the prey by the cranial rotation.     

Detection of chitinase activity by 2-aminobenzoic acid labeling of chito-oligosaccharides

Chitinases are hydrolases capable of hydrolyzing the abundant natural polysaccharide chitin. Next to artificial fluorescent substrates, more physiological chito-oligomers are commonly used in chitinase assays. Analysis of chito-oligosaccharides products is generally accomplished by UV detection. However, the relatively poor sensitivity poses a serious limitation. Here we report on a novel, much more sensitive assay for the detection of chito-oligosaccharide reaction products released by chitinases, based on fluorescent detection, following chemical labeling by 2-aminobenzoic acid. Comparison with existing UV-based assays, shows that the novel assay offers the same advantages yet allows detection of chito-oligosaccharides in the low picomolar range.     

Mitochondrial dysfunction leads to reduced chronological lifespan and increased apoptosis in yeast

We previously isolated a Saccharomyces cerevisiae mutant (HsTnII), which displays 40% reduced chronological lifespan as compared to the wild type (WT). In this study, we found HsTnII cultures to be characterized by fragmented and dysfunctional mitochondria, and by increased initiation of apoptosis during chronological aging as compared to WT. Expression of genes encoding subunits of mitochondrial electron transport chain and ATP synthase is significantly downregulated in HsTnII, and as a consequence, HsTnII is not able to respire ethanol. All these data confirm the importance of functional mitochondria and respiration in determining yeast chronological lifespan and apoptosis.     

Temperature-dependent lipid content and fatty acid composition of three thermophilic bacteria

The lipid content and fatty acid composition of a strain ofBacillus caldolyticus and of two facultative thermophiles (B. flavothermus and strain NZ-2) were analysed after growth at different temperatures. In all three strains the amount of membrane, as a fraction of total cellular dry mass, was found to increase with temperature, however, in varying degrees. Changes of lipid content and protein/lipid ratio inB. caldolyticus between 60°C and 100°C and in strain NZ-2 between 45°C and 70°C were minor; inB. f avothermus the alterations in the 50°C–70°C range were more pronounced. The same was found for changes observed in the phospholipid/total lipid and phospholipid/membrane ratios, and also in the amounts of individual phospholipids. The alterations of the fatty acid composition were most significant inB. caldolyticus, especially between 80°C and 95°C. In contrast, the main changes inB. flavothermus and NZ-2 were found to occur between 30°C and 50°C, and between 45°C and 60°C, respectively. Based on these data, strain NZ-2 could be characterized as the least andB. flavothermus as the most versatile of the three organisms.