Anatomy and Locomotion of a Worm

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Questions and Answers

Where are the black eyespots located in the head region?

Middorsally (correct)

Dorsally

Laterally

Ventrally

What is the function of the flame cells in the excretory system?

To digest nutrients

To absorb oxygen

To regulate body temperature

To collect nitrogenous wastes and excess water (correct)

What is the structure of the body wall in this organism?

Parenchyma, basement membrane, and nervous tissue

Basement membrane, muscle fibers, and parenchyma (correct)

Epidermis, muscle, and basement membrane

Epidermis, basement membrane, and parenchyma

How does the worm move?

Using its cilia and mucous secretion Signup and view all the answers

What is the function of the intestinal caeca?

To absorb nutrients Signup and view all the answers

What is the structure of the nervous system?

Two cerebral ganglia and two nerve cords Signup and view all the answers

How many excretory canals are present in this organism?

Two Signup and view all the answers

What is the function of the mouth in this organism?

For both ingestion and egestion Signup and view all the answers

What is the characteristic feature of the body wall of Aschelminthes?

Cuticle, epidermis and one longitudinal muscle layer Signup and view all the answers

What is the mode of reproduction in Aschelminthes?

Both asexual and sexual reproduction Signup and view all the answers

Where do Schistosoma spp (Blood flukes) inhabit?

In the intestine Signup and view all the answers

How many sets of reproductive systems are present in each proglottid of Cestoda?

Two Signup and view all the answers

What is the characteristic feature of the Trematoda?

Well-developed suckers are usually present Signup and view all the answers

What is the function of the ventral sucker in Trematoda?

Used for attachment Signup and view all the answers

What is the characteristic feature of the life cycle of Cestoda?

Complicated Signup and view all the answers

What is the size range of female Schistosoma spp?

12 to 26 mm Signup and view all the answers

What type of excretory system do flatworms possess?

Protonephridia Signup and view all the answers

What is a unique feature of turbellarian flatworms?

They have regeneration capabilities Signup and view all the answers

How do cestodes reproduce?

Through self-fertilization Signup and view all the answers

What is a characteristic of the nervous system in flatworms?

It has a ladder-like structure Signup and view all the answers

What is a function of the epidermis in flatworms?

Movement through cilia Signup and view all the answers

What is a type of parasitic flatworm?

Cestode Signup and view all the answers

What is true about the body structure of flatworms?

They are dorso-ventrally flattened Signup and view all the answers

How do trematodes reproduce?

Through cross-fertilization Signup and view all the answers

Study Notes

Body Structure

The head region has two black eyespots middorsally.
The mouth is located on the ventral surface near the middle of the body.
The body wall consists of layers of muscle fibers (circular, longitudinal, and dorsoventral), with spaces between the muscles and internal organs filled with parenchyma (a loose meshwork of cells lacking definite walls).

Locomotion

The worm glides slowly on the bottom mud using cilia and mucous secretion from the ectoderm.
It can also move by muscular contraction of its body.

Digestive System

There is no anus; the mouth is used for both ingestion and egestion.
The mouth leads to the pharynx, which branches into three intestinal caeca (blind).

Excretion and Osmoregulation

The first organ system specialized for excretion consists of flame cells (protonephridia) and branched excretory tubules in the parenchyma.
The excretory tubules collect in two longitudinal excretory canals, one on each side of the body, which open to the exterior on the dorsal surface by minute excretory pores.
Flame cells collect nitrogenous wastes and excess water from the parenchyma and drive them down the excretory tubules to the exterior.

Nervous System

The nervous system is composed of two cerebral ganglia and two nerve cords connected by transverse strands, forming a ladder-like structure.

Reproduction

Asexual reproduction occurs through regeneration and binary fission.
Sexual reproduction involves self or cross fertilization, with fertilized eggs depositing on submerged objects and hatching to young worms that develop into adults through metamerphosis.

Phylum Platyhelminthes (Flatworms)

General characteristics: acoelomate, triploblastic, bilaterally symmetrical, dorso-ventrally flattened, and epidermis with cilia or tegument.
Organs of attachment and adhesion (hooks and suckers) are present.
Digestive system is incomplete (absent in Cestodes).
Excretory system consists of protonephridia.
Nervous system is ladder-like.
No respiratory, circulatory, and skeletal systems are present.
Soft bodies, no exo-or endoskeleton.
Sexes are united (hermaphrodite, or monocious).
Exceptions: family Schistosomatidae.

Turbellaria (Free Living Flatworms)

Free-living, mostly marine, with some endo-commensals or parasites.
Ciliated epidermis.
Digestive system is incomplete.
Mouth is ventral.
Body is unsegmented.
Tangoreceptors and chemoreceptors are present.
Life cycle is simple.
Regeneration is present.

Trematoda (Flukes)

Leaf-like body.
Well-developed suckers are present.
Digestive system is incomplete.
Ovary is single, and testes are two or many.
Complex life cycles.

Cestoda (Tapeworms)

Body is covered with tegument.
Body is divided into scolex, neck, and many segments or proglottids.
The scolex is provided with adhesive structures (hooks and suckers).
Mouth and digestive system are totally absent.
Each segment (proglottid) contains one or two sets of complete hermaphroditic reproductive systems.
Life cycle is complicated.

Examples of Flatworms

Planaria sp.
Fasciola sp. (Liver fluke)
Schistosoma spp. (Blood flukes)
Taenia sp. (Tapeworms)

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Description

This quiz covers the anatomy of a worm's body, including the head region and body wall structure, as well as its mode of locomotion.