Write a note on habit, habitat and external features of pila globasa
Answers
1. Habit and Habitat of Pila Globosa:
Pila globosa or the apple snail is one of the largest freshwater mollusks. It is commonly found in freshwater ponds, pools, tanks, lakes, marshes, rice fields, and sometimes even in streams and rivers. They occur in those areas where there is a large amount of aquatic vegetation like Vallisneria, Pistia, for food. They are amphibious being adapted for life in water and on land.
The animal creeps very slowly by its ventral muscular foot, covering about five cm per minute.
The movement of the animal is like the gliding movement of the planarian. During the rainy seasons, Pila comes out of the ponds and makes long terrestrial tours, thus, respiring air directly. It can overcome long periods of drought in a dormant condition and buried in the mud; this period of inactivity is called aestivation or summer sleep.
Explanation:
1. Habit and Habitat of Pila Globosa:
Pila globosa or the apple snail is one of the largest freshwater mollusks. It is commonly found in
freshwater ponds, pools, tanks, lakes, marshes, rice fields, and sometimes even in streams and
rivers. They occur in those areas where there is a large amount of aquatic vegetation like
Vallisneria, Pistia, for food. They are amphibious being adapted for life in water and on land.
The animal creeps very slowly by its ventral muscular foot, covering about five cm per minute.
The movement of the animal is like the gliding movement of the planarian. During the rainy
seasons Pila comes out of the ponds and makes long terrestrial tours, thus, respiring air directly.
It can overcome long periods of drought in a dormant condition and buried in the mud; this
period of inactivity is called aestivation or summer sleep.
2. External Features of Pila Globosa:
The shell of Pila:
The shell of Pila globose, as in other Gastropoda, is univalve but coiled around a central axis in
a right-handed spiral.
The top of the shell is the apex which is formed first and growth of the shell takes place from it, the
apex contains the smallest and the oldest whorl. Below the apex is a spire consisting of several
successively larger whorls or coils followed by penultimate whorl and the largest whorl or body
whorl which encloses most of the body.
The lines between the whorls are called sutures. Internally all the whorls of the shell are freely
communicated with one another; such a shell is called unilocular. The body whorl has a large
mouth or opening, the margin of the mouth is called a peristome from which the head and the
foot of the living animal can protrude.
When viewed from the ventral side with the peristome facing the observer, the mouth lies to the
right of the columella, and the shell is spiraled clockwise, then it is spoken of as being right-
handed or dextral. The outer margin of the mouth is called an outer lip, and the inner margin is to
inner or columellar lip.