There is no true circulatory or respiratory system, but like all other animals, flatworms do take in oxygen. It may have suckers in various degrees of development, large hooks called anchors (or hamuli), small hooks that are remnants from the larval stage, or complex clamps that may be either muscular or sclerotised. The morphology of the opisthaptor is highly variable. The opisthaptor is primarily responsible for the attachment of the monogeneans to the host. In other species there is an oral sucker, with various degrees of muscularisation that surrounds the mouth.

In some species, the prohaptor may have a number of cephalic or head glands that secrete a sticky adhesive substance, and shallow muscular suckers, all used for attachment. The prohaptor has various adhesive and feeding structures. These differ between the prohaptor which is on the anterior end of the body and the opisthaptor, which is part of the posterior end of the body.

The haptor is a part of Platyhelminthes used to attach to its host. The longest ever recorded flatworm was a tapeworm over 90 ft (27 m) long. The interior of the acoelomate body is filled with somewhat loosely spaced mesodermal tissue called parenchyma tissue.įlatworms have a hydrostatic skeleton, which consists of a water filled body cavity that is controlled by muscles.įlatworms exhibit an undulating form of locomotion.ĭepending on species and age, individuals can range in size from almost microscopic to over 20 m long. There is also no true body cavity (coelom) except the gut hence, flatworms are classified as acoelomates. Turbellarians generally have a ciliated epidermis.

This means their organ systems form out of three germ layers: an outer ectoderm and an inner endoderm with a mesoderm between them.

Flatworms are the simplest triploblastic animals with organs. The flatworm’s cephalized soft body is ribbon-shaped, flattened dorso-ventrally (from top to bottom), and bilaterally symmetric.

Flat worm eggs