Part B: Classification of Parasitic Organisms - arthropods
Examine the parasites contained in the glass vials. Based on your observations identify them from the following descriptions.
Vial 6
Vial 7
Vial 8
Vial 9
Vial 10
Arthropods (Phylum Arthropoda)
Jointed leg animals. They have a hard outer skin (exoskeleton). Made up of segments: head, thorax and abdomen.
Class Insecta
The head contains one set of antennae. The thorax is made of three segments bearing three pairs of legs. They may have wings. The Order
Order Phthiraptera (lice)
They are small and wingless and have flattened bodies. The eyes are reduced or absent and the segmentation of the abdomen is indistinct.
Suborder Anoplura (sucking lice)
They have mouthparts adapted for sucking tissue fluids and the blood of their host.
| Linognathus vituli (long nosed sucking louse) |
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The eyes are absent. The abdomen is membranous with numerous hairs on each segment. The first pair of legs are the smallest. It has an elongated head and body. Sucking lice can debilitate the animal if there are considerable numbers feeding, but numbers usually increase when an animal is under stress.
Suborder Mallophaga (biting lice)
They feed on the epithelial debris on the skin of the host. They generally cause considerable irritation to the animal in large numbers.
| Damilinia ovis (sheep biting louse) |
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The antennae are thread-like and visible from the sides of the head. The head is broad.
The browsing on the upper layers of the skin will cause irritation and scratching causing loss of wool and fleece damage.
Order Aphaniptera (fleas)
They are wingless with laterally compressed bodiesabout 1.5 to 4 mm long. He exoskeleton is thick and dark brown
Order Diptera (flies and mosquitos)
They have a single pair of membranous wings. The mouthparts are adapted to sucking. They have large compound eyes.
| Lucilia cuprina (green bottle blowfly) |
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Bright metallic green colour. Silver white face and cheeks. Thorax with strong black bristles in four rows, abdomen narrow, tapering and bears fine hairs. Legs black, except thighs of first pair which are bright green. Medium size, 11 mm. Cause of primary blowfly strike. Attracted to moist areas of skin. The maggots are aggressive and will burrow into softened skin.
Class Arachnida
Have no head and therefore no antennae. Therefore the body is either divided into two sections or is fused into one. Mouthparts are small and they feed by sucking body fluid.
Order Acarina
Includes the hard and soft ticks and the minute relatives called mites. They have typically four pairs of legs. The mouthparts consist of a central toothed probe surrounded by two short sharp projections called pedipalps. The rest of the body is indistinct and fused.
| Boophilus microplus (tropical cattle tick) |
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The body is a plain light brown colour. Some ticks are multi-coloured but this one is plain. They start out small (about 3 mm) but the females engorge on blood and grow until they reach 2 cm long.
The mouthpieces attach through the skin of the cow and they suck significant volumes of blood. This obviously causes irritation and can debilitate the animal. They also spread the protozoal parasite that causes tick fever.
Molluscs (Phylum Mollusca)
They have a mantle with a significant cavity used for breathing and excretion, the presence of a radula, and the structure of the nervous system
Class Gastropoda
This class comprises snails and slugs. They typically have a well-defined head with two or four sensory tentacles with eyes, and a ventral foot. They often have a coiled one-piece shell.
Family Lymnaeidae
Small to large air-breathing freshwater snails
| Lymnaea tomentosa (freshwater snail) |
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Found on aquatic plants in swamps, ponds, and quiet waters. In Australia, this species is the most important intermediate host for liver fluke (Fasciola hepatica). The shell of mature freshwater snails varies from about 5 mm long for the small types to about 25 mm for the largest. They are most easily identified by the spiral of their shell. Looking at the pointed end, the direction of the spiral is determined by going around the shell from the point (or apex) to the large end. Their shell twist in a clockwise direction.
