Question

12.3 ● cross - section through (a) the intestinal region of the sandworm, nereis, and (b) magnified view depicting parapodia and setae.
check your progress
1.1 what kind of stimuli do you suppose the tentacles detect?
1.2 what features of sandworms would lead you to believe that they are free - living predators?
exercise 12 - 2
earthworms (class clitellata, subclass oligochaeta)
materials needed
□ preserved specimen of lumbricus
□ slide of lumbricus c.s.
□ dissection tools
□ dissecting pan
□ dissecting pins
□ latex gloves
□ dissecting microscope
□ compound microscope
earthworm external anatomy
members of the class clitellata, subclass oligochaeta (≈3,000 sp.), such as earthworms, blackworms, and angleworms, are free - living worms that live in freshwater habitats or damp soil. unlike polychaetes, oligochaetes lack parapodia and rely on their entire epithelial surface for gas exchange. most possess short, bristly setae on each segment. terrestrial members, such as the common earthworm, are well - suited for their fossorial (burrowing) lifestyle and possess many adaptive features for subterranean life.

Explanation:

1.1 Tentacles in sandworms likely detect chemical, tactile, and possibly light stimuli. Chemically, they can sense food - related substances in the water. Tactilely, they can feel physical contact with objects in the environment. Light - sensing ability might help in detecting changes in light levels for navigation or predator avoidance.
1.2 Features indicating sandworms are free - living predators include the presence of well - developed tentacles for detecting prey, and the structure of their body which allows for active movement in search of food. Their parapodia and setae provide mobility to chase and capture prey.

Answer:

1.1 Chemical, tactile, and possibly light stimuli.
1.2 Well - developed tentacles for prey detection and body structure enabling active movement for hunting.