Ecological Niche of the Crab
INVESTIGATING THE ECOLOGICAL NICHE OF THE CRAB USING A FAIR TEST
INTRODUCTION: The ecological niche of the crab Hemigrapsus edwardsi.
The crab is a member of the Crustacea phylum and is in the family Grapsidae. This crab species is found only in New Zealand on rocky shores. The rocky shore, where the crabs studied in this investigation were found is quite exposed. There is a large rock platform that provides small crevices and small rocks which help to protect them from wave action and predators. There are also sea lettuce, and other algae growing on parts of the rocks.
The crab has many adaptations that allow it to live on the rocky shore including: • grey/black colour for camouflage • food detection structures (antennae on its head and hairs on the mouth parts to sense chemicals in the sea water) • 4 pairs of legs with muscles that allow it to move sideways, as well as forwards and backwards • behavioural adaptations such as scuttling under rocks when the tide goes out or to avoid predators • freezing when being attacked (we noticed this when we touched some of them on their backs). This might confuse predators. • gills for gas exchange.
The rock pools provide a micro-climate where the temperature and salinity of the water will change, depending on the weather. If it was a really hot day, the rock pools will get warmer, more water will evaporate and the salinity will increase. The crab would have to be adapted to cope with these changes in salinity, otherwise, as the concentration of salt in the water around it changes, it will gain or loose mass due to osmosis. Through the process of osmoregulation, the crab is able to maintain a constant water balance in its body, but to do so requires energy and this could be measured by an increase in the respiration rate. This is what I am going to investigate.
Aim: To determine whether the respiratory rate of the crab changes in different salinities.
Hypothesis: The respiratory rate of the
INTRODUCTION: The ecological niche of the crab Hemigrapsus edwardsi.
The crab is a member of the Crustacea phylum and is in the family Grapsidae. This crab species is found only in New Zealand on rocky shores. The rocky shore, where the crabs studied in this investigation were found is quite exposed. There is a large rock platform that provides small crevices and small rocks which help to protect them from wave action and predators. There are also sea lettuce, and other algae growing on parts of the rocks.
The crab has many adaptations that allow it to live on the rocky shore including: • grey/black colour for camouflage • food detection structures (antennae on its head and hairs on the mouth parts to sense chemicals in the sea water) • 4 pairs of legs with muscles that allow it to move sideways, as well as forwards and backwards • behavioural adaptations such as scuttling under rocks when the tide goes out or to avoid predators • freezing when being attacked (we noticed this when we touched some of them on their backs). This might confuse predators. • gills for gas exchange.
The rock pools provide a micro-climate where the temperature and salinity of the water will change, depending on the weather. If it was a really hot day, the rock pools will get warmer, more water will evaporate and the salinity will increase. The crab would have to be adapted to cope with these changes in salinity, otherwise, as the concentration of salt in the water around it changes, it will gain or loose mass due to osmosis. Through the process of osmoregulation, the crab is able to maintain a constant water balance in its body, but to do so requires energy and this could be measured by an increase in the respiration rate. This is what I am going to investigate.
Aim: To determine whether the respiratory rate of the crab changes in different salinities.
Hypothesis: The respiratory rate of the