GENERAL ORGANISATION OF MONOGENEA

INTRODUCTIONPhylum - Platyhelminthes

Trematoda CestodaTurbellaria

ORDER

MonogeneaEx-

Polystoma

AspidobotheriaEx-

Aspidogaster

DigeneaEx- Fasciola

CLASS

GENERAL Characters Of Trematoda

A• Ecto-or Endoparasitic form.

• Body shape – Leaf like.

B• Body wall without epidermis and cilia.

• Well developed suckers are present.

C• Mostly Hermaphrodite except few families of Digenea.

• Life cycle simple or complicated.

morphology

Body sucker

Nervous system

Reproductive system

Alimentary tract

Body suckerPresence of a posteriorly situated adhesive structure-

Opisthaptor

Large, Circular, Muscular disc generally is separated completely or partially, into smaller suckers by septa.

The opisthaptor does bear 2-4 large hooks known as Anchors.

A single anchor is divided into root, base and shaft.

Many species possess various numbers of small suckers divided by septa, ranging

from 6-240 depending on the species.

In addition to the opisthaptor ,monogeneids usually possess 2 anteriorly located auxiliary sucker-the prohaptor.

Prohaptor situated one on each side of the mouth.

Prohaptor may appear as pits, sucker, or discs.

Reference: Thomas ChangPolystoma Diplectamum

Alimentary Tract

Mouth- anterior, flanked on each side by a prohaptor.

In Discocotyle sagittata, prohaptors modified as buccal suckers.

Mouth is surrounded by an oral sucker.

Head glands and head organ are present.

Intestinal tract is an inverted Y shape.

In Dactylogyrus amphibothrium, the caeca are not united posteriorly , but possess side branches.

In Polystoma, the caeca extend into the disc shaped opisthaptor.

Anatomy of monogenids

Nervous system

It consist of large cluster of nerve ganglia and cells.

Two nerves masses connected- transverse commissure

Situated at the anterior end of the body .

In some species the “brain” is arranged in a well formed circumesophageal ring.

1.

2.

3.

Nerve fibres extend from this ring.

Ventral nerves are highly developed and are connected by a series of transverse commissures .

Branches of nerve fibres innervate to the various sucker muscles and other portions of body.

In monogenea, 1 or 2 pairs of eye spots are present.

Source: Thomas Chang

Osmoregulatory system

• It is of the protonephritic type.• Flame cells are present at the end of collecting

tubules• Each tube makes a “U” curve.• The end of ascending tube there is a swelling

known as the contractile bladder• The tubes leaves the bladder empty to the

outside through the two separate nephridiopore• Nephridiopores are situated dorsolateral to the

mouth.

Osmoregulatory system

Reproductive system

THE MALE SYSTEM-

i) It consist of 1,2 or 3 testis, ex- Leptocotyleand Monocotyle.

ii) A single Vas efferens arises from each testis.

iii) A common atrium is found, the aperture is known as genital pore.

The Female system

A single ovary is present.

Shape may range globular to elongate.

Oviduct arises from the surface of the ovary.

Unicellular glands, collectively known as the Mehlis’ gland secrete into the ootype.

Terminal of the uterus opens into genital atrium.

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