THESIS APPROVAL

undulatory swimming. Also, the peristaltic crawling was present when worm had a
movement by getting extra traction from bristles that can be projected from the side of
its body. The explanation of such phenomena in most oligochaetes is there are
muscles arranged into two distinct layers in the body wall - the circular and
longitudinal muscle layers. A nerve cord below the intestine along the entire length
of the body worm has a major role of controlling these muscles that cause it to move.
Because of no hard skeletal elements to which these muscles attach, the forces were
produced since worms contract simply act upon the inner fluid-filled body
compartments (Jamieson, 1981). This design is referred to as a hydrostatic skeleton,
a typical manner of many burrowing invertebrates which lack appendages (Barnes,
1974). When the worm crawls, chaeta are protruded in those segments that are
undergoing shortening and thickening due to longitudinal muscle contraction. This
helps to anchor these segments to the substrate. In contrast, chaetae are retracted in
segments that are undergoing elongation and thinning due to circular muscle
contraction (Jamieson, 1981).
Clump living of L. hoffmeisteri population found in this observation
indicates an orientation behavior which is referred to as thigmotaxis (Drewes and
Fourtner, 1989). In nature, suitably cramped microhabitats may be established
including tight spaces between submerged, decaying leaves or crevices in submerged
(Stephenson, 1930). These preferred habitats offer worm protection from predators as
well as access them to food (Brinkhurst and Gelder, 1991). Additionally, these
organisms seemed to be vigilant in the environmental surroundings. Worms showed
rapidly pulled back their tail if they were touched by using glass rod. This reflex
response in L. hoffmeisteri is as possible as other oligochaetes since there are
mechanosensory neurons present in these animals to detect touch, vibration and
pressure. Drewes and Cain (1999) described this mechanism in which when a tail
segments of oligochaete worm was touched, it responded reflexively by waving of
muscle contraction that move in a direction opposite to the actual direction of body
propulsion in the term retrograde. Furthermore, those tails holding up to the water
surface were quickly withdrawn when they felt threatened. Since these worms have
tiny photoreceptor cells scattered along their tail segments (Drewes and Fourtner,
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