| dc.contributor.author | Jackson, Daniel Lloyd. | en_US |
| dc.date.accessioned | 2014-10-21T12:34:11Z | |
| dc.date.available | 1999 | |
| dc.date.issued | 1999 | en_US |
| dc.identifier.other | AAINQ49268 | en_US |
| dc.identifier.uri | http://hdl.handle.net/10222/55648 | |
| dc.description | As a force that draws zooplankters away from their food sources near the ocean surface, gravity has influenced the evolution of mechanisms and behaviours that counteract sinking. Paradoxically, it has also been suggested that gravity can be exploited by heavy zooplankters like bivalve larvae as a means of increasing feeding efficiency, notwithstanding the higher cost of locomotion. Gravity acts as a cue for orientation as veligers migrate throughout the water column, and is one of the physical forces that govern the helical swimming pattern that is typical of larval bivalve behaviour. The aim of this study was to examine how gravity affects swimming behaviour and orientation in marine bivalve larvae, and also how gravity influences their feeding, growth, and development processes. | en_US |
| dc.description | Veliger larvae of the blue mussel Mytilus edulis were reared in the Canadian Space Agency's Aquatic Research Facility (ARF) on a ten day spaceflight mission aboard the NASA Space Shuttle Endeavour . Video recordings of larval behaviour in both microgravity and in a normal gravity control centrifuge were made twice daily, and samples of larvae were preserved on Flight Days 3, 5, and 7. One group of larvae from each gravity treatment was returned alive to Earth. | en_US |
| dc.description | Larval growth rates were low in both gravity treatments, but there was a tendency towards greater growth and feeding rates in larvae reared in normal gravity. There was no strong evidence to suggest that mussel larvae are capable of buoyancy regulation; gravity did not influence the density of the animals nor the relative amounts of positively buoyant neutral lipid deposits. Larval development may have been affected by the absence of gravity, however. Although the larvae returned alive from space appeared normal and were capable of feeding, larvae reared in microgravity were generally in poorer condition and had thinner shells than larvae in normal gravity. Mortality rates were similar in both gravity treatments. | en_US |
| dc.description | Most larvae in microgravity continued to swim in a helical pattern, but changed direction and helix dimensions frequently. In contrast to the vertically directed swimming behaviour of larvae in normal gravity, veligers in microgravity did not exhibit any directional orientation. Mean forward swimming speeds, pitch angles, and helix heights of larvae in microgravity were greater than their normal gravity counterparts. Larvae swimming downwards in normal gravity had greater translational and rotational swimming speeds than either upward swimmers or larvae in microgravity. The helix diameters of downward swimmers, were also greater than those of larvae swimming in the absence of gravity. | en_US |
| dc.description | A kinematic analysis of the forces produced by mussel larvae swimming in the presence and absence of gravity is presented. Larvae in microgravity required less energy to swim than larvae in normal gravity, and were able to move in higher helices and steeper pitch angles due to the lack of interactions between gravity and drag. The model decomposes total power output into power produced along the x- and y-axes, and reveals that mussel larvae can take advantage of the effect of gravity to transfer more power into the horizontal component of motion while swimming downwards. This behaviour has been implicated as an adaptation to maximise feeding success. Overall, these studies suggest that bivalve larvae have a much greater degree of control over their behaviours than has been previously considered. | en_US |
| dc.description | Thesis (Ph.D.)--Dalhousie University (Canada), 1999. | en_US |
| dc.language | eng | en_US |
| dc.publisher | Dalhousie University | en_US |
| dc.publisher | | en_US |
| dc.subject | Biology, Ecology. | en_US |
| dc.subject | Biology, Oceanography. | en_US |
| dc.subject | Biology, Animal Physiology. | en_US |
| dc.subject | Biology, Zoology. | en_US |
| dc.title | Gravity and the physiology of locomotion and feeding in marine bivalve larvae: Results from Space Shuttle experiments. | en_US |
| dc.type | text | en_US |
| dc.contributor.degree | Ph.D. | en_US |
