The phylum Mollusca contains over 100,000 species with a variety of body forms and lifestyles. In mollusks, the coelom is reduced and limited to the region around the heart. The Mollusk body first appeared during the Cambrian Period. All mollusks have: 1. A visceral mass containing internal organs, including the digestive tract, paired kidneys, and reproductive organs. 2. A mantle [...]
The following points highlight the top two types of respiration in mollusca. The types are: 1. Aquatic Respiration 2. Terrestrial Respiration. Type # 1. Aquatic Respiration: In this, O2 dissolved in water is used. The surface of the respiratory structure is greatly increased to allow rapid absorption of O2. The aquatic respiratory structures may be placed under two heads—primary and [...]
In this article we will discuss about:- 1. Description of Torsion 2. Course of Torsion 3. Ways 4. Effect 5. Significance. Description of Torsion: 180° anticlockwise twisting of the visceropallium on the head-foot long axis during early development in gastropod molluscs is torsion. It is an early and fundamental event in gastropod ontogeny (the event in phylogeny, which brought the [...]