Slater (woodlouse), Biological name Porcellio scaber, is probably the most common species in New Zealand. They belong to the biological class Crustacea. Their size is about 17mm in length. They have rough exoskeleton and usually in dark grey colour. They have 7 pairs of legs, each pair is attached to the underneath of each thorax segment. Their body consists into three sections: head, thorax and abdomen, these are often fused together so that it is difficult to be sure where each section starts or ends. Most slaters can live for 2-4 years, although most die as juveniles. ➢ Habitat
In New Zealand, slaters are common in spring and autumn as they prefer low light intensity and high humidity and cooler temperature. They are mostly found in cool, damp conditions such as under the bricks, woods and rocks, damp soil litter under the trees.
Soils which are rich in calcium and other macro-decomposers (such as earthworms) generally have high number of slaters. These soils are usually in neutral or alkaline pH. As we known, acid soils have always limited the density of slater population because these soils may be lack sufficient calcium to enables them to build up their calcareous exoskeletons. In my initial trials of the slaters natural habitat, I observed that slaters are living between pH6 and pH9. Slaters share their habitat with centipedes, spiders, earthworms, etc. They have predators such as small birds and spiders. Slaters usually feed on dead plant material, fungi, and organic matter in soil so they are omnivores and scavengers. The densities of slaters have usually expressed in numbers per square meter and may be very high. The density shows a sharp increase on release of the young, then followed by a rapid decline as these young meet an early end.
➢ Adaptive features
Slaters have many adaptations that enable them to live in a range of terrestrial habitats and help them to reduce the chances of desiccation due to they do not have a waterproof waxy cuticle on their exoskeleton. • Slaters have respiratory pleopods that help reduce desiccation. • Their tail includes the Uropods which are for “drinking” water to maintain the water balance in the body. • They moult their old skin. That helps reduce predation by other insects and water losses, also allows them to remain reasonably active. • Slaters show positive chemotaxis so they choose to live in the soil which content more calcium or lime. By reading the information above, I decided that I am going to investigate the preferred soil pH for slaters, which will be the best soil pH for their calcareous exoskeleton, and helps to increase chances of survival in the terrestrial habitat.
The purpose of this experiment is to investigate the density of slater in areas of different level of pH. Thus find out which level of pH is preferred for them.
In the area of higher pH, more slaters prefer and therefore more of them will move towards and stay in that area.
There is no significant difference by the slaters when the soil pH is higher or lower.
• 40 pieces of laboratory tissue paper
• About 100 slaters
• Stop watch
• pH meter
• 6 Petrie dishes (8.5cm diameter)
• Distilled water
• 1.5mL of pH solutions (pH4, pH5, pH6, pH7, pH8, pH9) • 6 little bottles
• Glue gun
• Black paper
• Black ink
• 6 drops
1. Randomly collect about 100 slaters of similar sizes under woods and rocks from the garden. Keep them in a black ice-cream container, with moist soil and a couple of dead leaves. Make small holes in the lid for ventilation. Put some food in, such as lettuce or carrot. Keep this environment as similar to their natural habitat as possible. Place this container in a dark and cool area. 2. Make up a choice chamber with 6...