Biomedical subjects

B Shillito

Publications and source records attributed to B Shillito.

4 recordsLinked to original sources

PubMed2001

Deep-sea ecology. Developmental arrest in vent worm embryos.

Temperature is a key factor in controlling the distribution of marine organisms and is particularly important at hydrothermal vents, where steep thermal gradients are present over a scale of centimetres. The thermophilic worm Alvinella pompejana, which is found at the vents of the East Pacific Rise (2,500-m depth), has an unusually broad thermotolerance (20-80 degrees C) as an adult, but we show here that the temperature range required by the developing embryo is very different from that tolerated by adults. Our results indicate that early embryos may disperse through cold abyssal water in a state of developmental arrest, completing their development only when they encounter water that is warm enough for their growth and survival.

Animals↗

PubMed2001

Hydromineral regulation in the hydrothermal vent crab Bythograea thermydron.

This study investigates the salinity tolerance and the pattern of osmotic and ionic regulation of Bythograea thermydron Williams, 1980, a brachyuran crab endemic to the deep-sea hydrothermal vent habitat. Salinities of 33 per thousand-35 per thousand were measured in the seawater surrounding the captured specimens. B. thermydron is a marine stenohaline osmoconformer, which tolerates salinities ranging between about 31 per thousand and 42 per thousand. The time of osmotic adaptation after a sudden decrease in external salinity is about 15-24 h, which is relatively short for a brachyuran crab. In the range of tolerable salinities, it exhibits an iso-osmotic regulation, which is not affected by changes in hydrostatic pressure, and an iso-ionic regulation for Na(+) and Cl(-). The hemolymph Ca(2+) concentration is slightly hyper-regulated, K(+) concentration is slightly hyper-hypo-regulated, and Mg(2+) concentration is strongly hypo-regulated. These findings probably reflect a high permeability of the teguments to water and ions. In addition to limited information about salinity around hydrothermal vents, these results lead to the hypothesis that B. thermydron lives in a habitat of stable seawater salinity. The osmoconformity of this species is briefly discussed in relation to its potential phylogeny.

Animals↗

PubMed1997

Diffraction contrast imaging of extracellular matrix components using zero-loss filtering.

The beta-chitin microfibrils from the deep-sea hydrothermal vent worm Riftia pachyptila were studied in both mature and fresh tubes experimentally obtained. The methods used were electron diffraction and electron diffraction contrast images, in conjunction with an electron-energy filter, operated in the zero-loss mode. In both studied samples, microfibrils are organized in successive layers, inside which they are parallel. However, the fresh tube is less densely packed and diffraction data show that these microfibrils may be in a partially hydrated state. These results indicate that a later step occurs in the compaction of the tube material once it has been extruded. Comparison of filtered and unfiltered diffraction patterns shows that zero-loss filtering significantly improves both working conditions and quality of diffraction recordings.

Actin Cytoskeleton↗

PubMedDate not supplied

Effect of cadmium, copper and mercury on antioxidant enzyme activities and lipid peroxidation in the gills of the hydrothermal vent mussel Bathymodiolus azoricus.

Metals are known to influence lipid peroxidation and oxidative status of marine organisms. Hydrothermal vent mussels Bathymodiolus azoricus live in deep-sea environments with anomalous conditions, including high metal concentrations. Although B. azoricus are aerobic organisms they possess abundant methano and thioautotrophic symbiotic bacteria in the gills. The enzymatic defences (superoxide dismutase (SOD), catalase (CAT), total glutathione peroxidase (Total GPx) and selenium-dependent glutathione peroxidase (Se-GPx)) and lipid peroxidation were determined in the gills of B. azoricus exposed to Cd (0.9 microM), Cu (0.4 microM) and Hg (0.1 microM) with different times of exposure. The experiments were performed in pressurized containers at 9+/-1 degrees C and 85 bars. Results show that vent mussels possess antioxidant enzymatic protection in the gills. Cd and Cu had an inhibitory effect in the enzymatic defence system, contrarily to Hg. These enzymatic systems are not completely understood in the B. azoricus, since reactive oxygen species might be produced through other processes than natural redox cycling, due to hydrogen sulphide and oxygen content present. Also the symbiotic bacteria may play an important contribution in the antioxidant protection of the gills.

Analysis of Variance↗