Humidity and Porcellio Scaber Essay

Sophie White
Biology 3.1
Background Research:
Slaters belong to the order Isopoda. They are scavengers and omnivores, which mean they eat a variety of food of both animal and plants.
They are nocturnal because they come out at night time and their preferred habitats are in lime-rich soils because they need calcium to build their hard cuticle. They like dark, damp and sheltered places eg logs, leaf litter, rotting wood, under loose tree bark, garden debris, compost heaps, under rocks and bricks
Slaters lack a waxy cuticle layer that is used in most insects to minimise desiccation (drying out due to water loss). As a result of this their behaviour is concerned with avoiding desiccation. For example, they will try to reduce water loss by moving away from hot or dry areas and will therefore head toward more humid and cooler conditions. They will increase their rate of movement when the humidity or temperature is unfavourable as a result of orthokinesis.
In the humid conditions it is possible for slaters to absorb water vapour by diffusion through their exoskeleton. And in the cooler conditions, it tends to be darker so slaters would also prefer dark conditions over brighter conditions. The fact that slaters are more active at night means they’d avoid predators resulting in greatly reduced water loss.
If the temperature is too low, it means the slaters would become sluggish meaning they’re unable to avoid their predators.
To avoid desiccation in higher temperatures, the slaters speed up their movements. This is so they don't spend too much time in unfavourable conditions, therefore increasing their chances of survival.
They have a large surface area to volume ratio meaning that they are more likely to lose water by diffusion.

Kingdom: Animalia
Phylum: Arthropoda
Subphylum: Crustacea
Class: Malacostraca
Order: Isopoda
Suborder: Oniscidea
Family: Porcellionidae
Genus: Porcellio
Crustaceans with a ridged, segmented, long exoskeleton and fourteen jointed limbs
Most commonly found in cool, damp and humid conditions
Prone to desiccation (hence why they avoid dry environments) because of the lack of a waxy coating on their exoskeleton
Most of their behaviour revolves around avoiding desiccation, so are therefore most commonly found in damp conditions
Often found in groups/clumps to reduce surface area and water loss (behavioural adaptation)
They spend the daylight hours congregated under shelters, sometimes in large numbers; at night they wander around in search of food, and even climb tree trunks (nocturnal)
Once uncovered, slaters will try to escape the light

Bibliography:
Soil Bugs. (2015). Isopoda. Retrieved from www.soilbugs.massey.ac.nz/isopoda.php
UKEssays. (2015). Physical Education. Retrieved from www.ukessays.com/essays/physical-education/orthokinesis-in-slaters-relative-to-humidity-physical-education-essay.php
Tree Lupin & woodlice pages. Woodlice Online. Retrieved from www.porcellio.scaber.org/woodlice/expback.htm
Biowikicsj.wikispaces.com,. 'Woodlice Investigation'. N.p., 2015. Web. 15 Feb. 2015.
Porcellio.scaber.org,. 'P.Scaber Experiment Background Information'. N.p., 2015. Web. 18 Feb. 2015. http://www.porcellio.scaber.org/woodlice/expback.htm
Abbott, C. H. and Search (1918) Reactions of land isopods to light
Drobne, D., Drobne, S. and 313-322, Z. 457: (2014) Reference values for feeding parameters of isopods (Porcellio scaber, Isopoda, Crustacea)
Hornung, E., Farkas, S. and Fischer, E. (1998) Tests on the Isopod Porcellio Scaber
Rombke, T., Rombke, J. and Russell, D. (2011) Soil Organisms
Citation
(Drobne, Drobne, and 313-322, 2014)
(Abbott, 1918)
(Rombke, Rombke, and Russell, 2011)
(Hornung, Farkas, and Fischer, 1998)

Aim: To investigate the preferred light intensity in artificial light for Porcellio scaber

Hypothesis: That the slaters will be found in abundance in 0-200lux light exposure.

Equipment:
6 choice chamber (constructed from 6 petri dishes)
Light metre
20 slaters
Lamp
Shade cloth
Black paper
White

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