Q 31. What are the anatomical differen... [FREE SOLUTION]

Chapter 1: Q 31. (page 7)

What are the anatomical differences between nemertines and mollusks?

Short Answer

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Molluscs have a shell, albeit a reduced shell. Nemertines do not have a shell. Nemertines have a proboscis; molluscs do not. Nemertines have a closed circulatory system while molluscs have an open circulatory system.

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Anatomy of mollusks

The muscular foot is the most ventral organ and the mantle is the limiting dorsal organ that overlies the visceral mass. The foot, which serves for locomotion and anchoring, varies in shape and function depending on the type of mollusc being studied. In shellless molluscs, the leg is usually the same size as the shell opening. The leg is extendable and extendable. In the class Cephalopoda ("head-foot"), the foot is funnel-shaped to expel water at high speed from the mantle cavity; and the front edge of the leg was modified into a circle of arms and tentacles.

Most molluscs have a special feeding organ, the radula, which has chitinous saw-like teeth. The radula is present in almost all groups. Used to crush or scrape food before it enters the digestive tract. The mantle (also known as pallium) is the dorsal epidermis in molluscs; all molluscs except some cephalopods are specialized to secrete a calcareous shell that protects the animal's soft body.

Anatomy of nemertines

Nemertini are the simplest eukoelomates. These ribbon-shaped animals carry a specialized proboscis enclosed in a rhynchocoel. The development of a closed circulatory system derived from the coelom is a significant difference observed in this species compared to other pseudocoelomate phyla. The digestive, nervous and excretory systems are more developed in nemertines than in less advanced tribes. Embryonic development of Nemertine worms proceeds through the planuliform larval stage.