An Investigation Into the Effects of Varying Seawater Concentrations on Two Marine Invertebrates’ Osmoregulatory Abilities; Carcinus Maenas and Arenicola Marina.
An investigation into the effects of varying seawater concentrations on two marine invertebrates’ osmoregulatory abilities; Carcinus maenas and Arenicola marina.
Introduction
The concentration of solutes in the bodily fluids of most marine invertebrates is roughly isosmotic to their environment (Raven, 2008). Because there is no osmotic gradient there is no tendency for the net diffusion of water away from the animal’s cells to occur. When a change in salinity occurs some organisms have the ability to maintain a constant internal homeostasis despite these external changes and are known as osmoregulators (Oxford, 2008). Other animals lack this ability and as such are called osmoconformers; their internal osmolarity matches that of their environment although their ionic composition may be different (Oxford, 2008). In this experiment the osmoregulatory capability of two marine invertebrates was investigated, Carcinus maenas (shore crab) and Arenicola marina (lugworm). The lugworm’s capability to regulate cell volume over a period of 90 minutes was observed by measuring the change in weight of an entire worm exposed to different seawater concentrations in 15 minute intervals. The shore crab’s haemolymph ionic composition was analysed in response to a longer term exposure to hypo-osmotic conditions over 3 days. The haemolymph was analysed for osmolarity, Sodium ion concentration and chloride ion concentration.
Methodology
Instructions were followed for both organisms as supplied by the lab schedule.
Carcinus maenus
Haemolymph was extracted from a crab that had been stored in a seawater concentration of 75% for 3 days prior to the experiment. 200µl was then pipetted into an Eppendorf tube, avoiding transferring any coagulated proteins into the Eppendorf tube. The osmolarity of the sample was measured by pipetting 100µl of the sample into another Eppendorf tube and placing this inside a Camlab Freezing Point Osmometer, ensuring the probe is clean and dry. Sodium
Introduction
The concentration of solutes in the bodily fluids of most marine invertebrates is roughly isosmotic to their environment (Raven, 2008). Because there is no osmotic gradient there is no tendency for the net diffusion of water away from the animal’s cells to occur. When a change in salinity occurs some organisms have the ability to maintain a constant internal homeostasis despite these external changes and are known as osmoregulators (Oxford, 2008). Other animals lack this ability and as such are called osmoconformers; their internal osmolarity matches that of their environment although their ionic composition may be different (Oxford, 2008). In this experiment the osmoregulatory capability of two marine invertebrates was investigated, Carcinus maenas (shore crab) and Arenicola marina (lugworm). The lugworm’s capability to regulate cell volume over a period of 90 minutes was observed by measuring the change in weight of an entire worm exposed to different seawater concentrations in 15 minute intervals. The shore crab’s haemolymph ionic composition was analysed in response to a longer term exposure to hypo-osmotic conditions over 3 days. The haemolymph was analysed for osmolarity, Sodium ion concentration and chloride ion concentration.
Methodology
Instructions were followed for both organisms as supplied by the lab schedule.
Carcinus maenus
Haemolymph was extracted from a crab that had been stored in a seawater concentration of 75% for 3 days prior to the experiment. 200µl was then pipetted into an Eppendorf tube, avoiding transferring any coagulated proteins into the Eppendorf tube. The osmolarity of the sample was measured by pipetting 100µl of the sample into another Eppendorf tube and placing this inside a Camlab Freezing Point Osmometer, ensuring the probe is clean and dry. Sodium
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