Pila: Classification, Structure and FAQs

Pila is an aquatic gastropod mollusc belonging to the family Ampullariidae. They are freshwater snails that are commonly known as apple snails. Read this article to learn in detail about the Pila genus.

Table of Contents

• Classification of Pila
• Structure of Pila
• Nervous System of Pila
• Ganglia
• Commissures
• Connectives
• Nerves
• Digestive System of Pila
• Alimentary Canal
• Digestive Glands
• Respiration in Pila
• Frequently Asked Questions

Classification of Pila

Structure of Pila

• Pila is a soft, unsegmented and globose mollusc whose body can be divided into head, visceral mass and foot.
• The head consists of two pairs of tentacles, one pair of eyes and a ventral slit mouth, also known as an aperture.
• The foot is flat, broad, ventral and almost triangular in shape. It is attached to the operculum.
• A visceral mass, that is a hump-like structure, houses all the main organs of the animal.
• The mantle is a structure that covers the visceral mass. It secretes calcium carbonate and forms a shell for the organism.
• The striking feature of Pila is the presence of an operculum. The operculum is an anatomical calcareous structure that is attached to the upper surface of the foot. It acts as a trapdoor that closes the aperture of the shell when the soft part of the animal is withdrawn.

Nervous System of Pila

The nervous system of a gastropod consists of ganglia, connectives, commissures, and the nerves connecting to different organs.

Ganglia

A ganglion is a small compact mass of nerve cells and connective tissue. There are five pairs of ganglia found in Pila, namely cerebral ganglia, pleuropedal ganglia, visceral ganglion, buccal ganglia and supraintestinal ganglia.

Commissures

The nerve connections between two ganglia are termed as commissures. The ganglia pairs are placed on the opposite sides of the body such that commissures can connect them. The cerebral ganglia are connected by the cerebral commissure, the buccal ganglia are connected by the buccal commissure, and similarly, the pleuropedal ganglia are connected by the pedal commissure.

Connectives

The nerve connections that join two dissimilar ganglia are called connectives. Cerebrobuccal connective connects cerebral and buccal ganglia. The pleuropedal ganglion is connected to the cerebral ganglia on each side by cerebropleural and cerebropedal connectives.

Nerves

• The cerebral ganglia innervate the eye and tentacles on the sides of the body.
• The pedal ganglion gives out nerves to the foot.
• The pleural ganglion innervates the mantle.
• The supraintestinal ganglion gives out nerves to the pulmonary sac and the ctenidium.
• The buccal ganglion sends out nerves to the buccal mass.
• The visceral ganglia innervate the kidney, intestine, pericardium and genitals.

Digestive System of Pila

The digestive system of Pila comprises the alimentary canal and digestive glands. Let us look at them briefly.

Alimentary Canal

• The alimentary canal is a coiled structure that starts from the mouth and ends at the anus.
• It is divided into three regions, namely the foregut made up of the buccal cavity and oesophagus, the midgut, which includes the stomach and intestine and the hindgut, which comprises the rectum.
• The buccal cavity is a chamber which is made up of several sets of muscles for the movement of the radula (mouth).
• Oesophagus is a narrow, long tube that extends from the buccal mass and opens into the stomach.
• The stomach is a U-shaped chamber that receives the oesophagus and opens into the intestine via a pyloric chamber.
• The intestine is a long and coiled structure that is present between the gonads and ultimately joins the rectum.
• The rectum is a thick-walled tube that opens into the anus.

Digestive Glands

• There are two salivary glands found on either side of the buccal mass. They secrete carbohydrase enzymes and mucin-like substances.
• The digestive glands are triangular and coiled. The digestive epithelium is lined with alveoli and is made up of three types of cells: secretory cells, resorptive cells and lime cells.
• The oesophageal pouches are rounded structures located below the salivary glands that open narrow ducts at the junction of the oesophagus and buccal cavity. These pouches secrete digestive enzymes.
• The buccal glands are structures present at the roof of the buccal cavity that function as accessory digestive glands.

Respiration in Pila

Pila can survive in both water and land. They are amphibians that exhibit double mode of respiration, i.e. they can use oxygen from water during aerobic respiration and inhale atmospheric air while on land. The animal possesses a gill or ctenidium for aquatic respiration and pulmonary sacs or lungs for aerial respiration. Nuchal lobes act as accessory respiratory glands.

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