In order for the reproduction of blood flukes to occur asexually, infecting a freshwater snail must happen to act as an intermediate host. Blood flukes are unique in the way that they can reproduce sexually and asexually. Blood flukes are the only form of trematodes that are not hermaphrodites, meaning they have both a male and female sex. Most trematodes are simultaneous hermaphrodites, having both male and female organs.

Trematodes generally lack any specialized sense organs, although some ectoparasitic species do possess one or two pairs of simple ocelli. The nerve cords running along the ventral surface are always the largest, while the dorsal cords are present only in the Aspidogastrea. The brain consists of a pair of ganglia in the head region, from which two or three pairs of nerve cords run down the length of the body. The two collecting ducts typically meet up at a single bladder, opening to the exterior through one or two pores near the posterior end of the animal. This consists of two or more protonephridia, with those on each side of the body opening into a collecting duct. Īlthough the excretion of nitrogenous waste occurs mostly through the tegument, trematodes do possess an excretory system, which is instead mainly concerned with osmoregulation. As in other flatworms, there is no anus, and waste material must be ingested through the mouth. In some species, the caeca are themselves branched. The pharynx connects, via a short oesophagus, to one or two blind-ending caeca, which occupy most of the length of the body. The mouth is located at the forward end of the animal, and opens into a muscular, pumping pharynx. It is also the surface of gas exchange there are no respiratory organs. The body surface of trematodes comprises a tough syncytial tegument, which helps protect against digestive enzymes in those species that inhabit the gut of larger animals. Their most distinctive external feature is the presence of two suckers, one close to the mouth, and the other on the underside of the animal. Trematodes are flattened oval or worm-like animals, usually no more than a few centimeters in length, although species as small as 1 millimetre (0.039 in) are known. Varied trematodes, from 1911 Encyclopædia Britannica Adult blood flukes can live indefinitely in human or animal reservoir hosts. Any contact with water can cause potential human infection. Humans get infected by the cercariae, which are the larval forms of trematodes. īlood Flukes: include five species of Schistosoma: Schistosoma japonicum, S. There are high numbers of human infection with all three of these liver flukes. Liver flukes are commonly found within bile ducts, liver, and gallbladder in mammalian and avian species. Clonorchis and Opisthorchis are considered the most important human pathogens because they are classified as class 1 carcinogens. Liver Flukes: include Clonorchis, Opisthorchis, and Fasciola. The first intermediate host of the lung fluke is a snail, the second intermediate host is a crab or crayfish, and the final host for lung flukes is an animal or human host. The completion of a lung fluke's life cycle follows the cycle of first, second, and final hosts. Paragonimus westermani needs three different hosts in order to survive, reproduce, and complete its life cycle. Lung Flukes: there are eight species of lung flukes that infect humans: Paragonimus westermani, P. Blood flukes include species of the genus Schistosoma.

Blood flukes inhabit the blood in some stages of their life cycle.This group includes the lung fluke, Paragonimus westermani, and the liver flukes, Clonorchis sinensis and Fasciola hepatica. Tissue flukes infect the bile ducts, lungs, or other biological tissues.For instance, pond flukes infect fish in ponds. They may also be classified according to the environment in which they are found. įlukes can be classified into two groups based on, the system in which they infect their vertebrate host. Two other parasitic classes, the Monogenea and Cestoda, are sister classes in the Neodermata, a group of Rhabditophoran Platyhelminthes. The Digenea, the majority of trematodes, are obligate parasites of both mollusks and vertebrates, but rarely occur in cartilaginous fish. The smaller Aspidogastrea, comprising about 100 species, are obligate parasites of mollusks and may also infect turtles and fish, including cartilaginous fish. Nearly all trematodes are parasites of mollusks and vertebrates. The trematodes or flukes include 18,000 to 24,000 species, divided into two subclasses.

Fluke worm