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Torsion (twisting) is the rotation of visceral organs in anticlockwise direction through an angle of 180° on the rest of the body during larval development. The phenomenon takes place in the free-swimming (veliger) larva of gastropods and converts the symmetrical larva into an asymmetrical adult.
- In which of the following does torsion occur?
- What is Detorsion in Mollusca?
- How does coiling differ from torsion?
- What is fouling in gastropods?
- What do you mean by Detorsion?
- What is significance of torsion?
- Do slugs undergo torsion?
- How do gastropods move?
- Do mollusks go through larval stages?
- Who suggested that torsion is an adaptation?
- What survival problem did torsion create How have gastropods evolved to avoid this problem?
- How do gastropods avoid fouling?
- Are gastropods bilateral?
- Why are gastropods so successful?
In which of the following does torsion occur?
Torsion is a gastropod synapomorphy which occurs in all gastropods during larval development.
What is Detorsion in Mollusca?
Detorsion is reversal of torsion which takes place when during evolution shell is lost or a type of shell evolves that has openings on the opposite sides. In such situations twisting of visceral mass is not necessary.
How does coiling differ from torsion?
As nouns the difference between torsion and coiling
is that torsion is twist, twisting while coiling is the pattern or motion of something that coils.
What is fouling in gastropods?
Fouling is when waste that is excreted, washes back into the snails gills. ... With the shell coiling and pressed on the right side of the mantle cavity, over the years gastropods have lost the gill, auricle and kidney (Hickman et al, 2009). With the loss of the right gill, fouling is less likely to happen.
What do you mean by Detorsion?
Medical Definition of detorsion
: the removal of torsion specifically : correction of abnormal twist (as of the intestine)
What is significance of torsion?
a. Torsion promotes stability in the adult by bringing the body of the snail nearer to substratum. b. The free flow of respiratory water current in the posteriorly located mantle cavity containing the gills is obstructed by the back- flow of water current during upstream movement of the snail.
Do slugs undergo torsion?
Some gastropods such as the slug (below) do not have a shell. The larvae undergo torsion during development. It is a twisting that positions the visceral mass so that the anus is above the head. ... Slugs do not have shells.
How do gastropods move?
Gastropods move using a single appendage—the foot. For many gastropods the power for locomotion is provided by muscular waves moving along the ventral surface of the foot1–3, the force of these waves being coupled to the substratum by a thin layer of pedal mucus.
Do mollusks go through larval stages?
Both mollusks and annelids develop through a larval stage called a trochophore larva. Trochophore larvae are characterized by having a band of cilia that wraps around the body.
Who suggested that torsion is an adaptation?
Garstang (1928) advocated that torsion is an adaptive feature and useful to the larvae (veliger larva) for protection of soft parts against enemies but of little direct use to the adult.
What survival problem did torsion create How have gastropods evolved to avoid this problem?
Gastropods have evolved to avoid this problem by losing the gill, atrium on their right side due to carrying a coiled shell with a conispiral shape, leading to bilateral symetry.
How do gastropods avoid fouling?
How have gastropods evolved to avoid fouling? Since organs of the mantle cavity (osphradia) would be better sample water when turned in the direction of travel, the head could be withdrawn into the shell. ... Some, with two gills, avoid fouling by venting excurrent water through a dorsal cleft above the anus.
Are gastropods bilateral?
Thus, although gastropods are still considered to be bilaterally symmetrical (that's how they start out), by the time they become adults, gastropods that have undergone torsion have lost some elements of their "symmetry".
Why are gastropods so successful?
Gastropods are well-known animals which have been associated with humans since the dawn of civilization. Their bodies were gathered for food and their shells were used as tools, ornaments, and later as money. Their widespread occurrence is clear evidence of their successful adaptation to different environments.
