Lobsters Are Osmoregulators

Methods

To determine the principals of osmoregulation, we sampled two lobsters from each tank and there were three different tanks which the water ranged in salinity. The experiment is to determine whether the six lobsters tested are osmoregulators or osmoconformers, this is done by obtaining a sample of hemolymph. The first step of the lab is to prepare the needle and syringe that will be taking the hemolymph. The syringe size was 1 ml, and the intention is to collect between 0.5 and 1.0 ml of hemolymph. The needle size was 20 gauge, because anything smaller would destroy the hemolymph cells. Then the lobster was picked up with a firm grim around the dorsal celphao-thorax region and flipped over to expose the ventral side. The hemolymph was be extracted from the central midline of the ventral pre-branchial region, of the first section. Although, before piercing the membrane, the bevel of the needle had to be pointing up. When the needle was injected into the membrane, it did not have to go any deeper than 2-3 mm into the hemocyannin (blood cavity). If the needle went to deep it would strike nerves of the lobster. This procedure was completed six times on six different lobsters, to determine if the lobsters are osmoregulators or osmoconformers.

As soon as the hemolymph was taken form the lobster it was placed into a marked 1.5 ml microcentrifuge tube, and placed on ice. It was then taken to a lab and spun for 3 minutes on a microcentrifuge. The serum from the microcentrifuged hemolymph was taken back to the General Physiology Lab in Duffy and placed into osmometer, which measures the osmolarity. This is done by freezing the sample of hemolymph and the time that it takes to defrost depicts the amount of osmoles.

Water analyses for the three tanks determined the temperature Ñ"C, pH, salinity (ppt), oxygen levels and the ammonia content. The temperatures of all three tanks were taken by a digital thermometer and the pH of the water was taken by a pH meter. The normal range of pH for a marine tank is approximately 8.3. The salinity of the tanks was determined by two different instruments. The first being the refractometer, which measures the light refraction though water. The amount of light ray refracted though the water determines the salinity. The refractometer required correct readings of temperature for it to be accurate. The other instrument is called hydrometer that measures the specific gravity of salinity in water. This was accomplished by the height at which the hydrometer floated in water. The amount of salt in the water affects its density; therefore the hydrometer gave an accurate reading of salinity.

The water was also tested for the amounts of ammonium within the three tanks. The ammonium analysis began with a water sample from each tank. This was taken to the lab and diluted 1/10 with deionized water in a test tube. Three test tubs were used with 2.5 ml from the three different tanks and then the test tube was then filled with 22.5 ml of deionized water. Thirty drops of Mineral Reagent had to be placed in the test tubes, then 3 drops of poly-vinal alcohol. The last step was adding 1 ml of Nesslers Reagent, which had to be inverted before being placed in the spectrophotometer, which had a digital screen that produced the ammonium value. Oxygen levels were also taken, by a dissolved oxygen meter that measures the amount of oxygen dissolved in a unit volume of water.

Abstract

It has been previously shown that lobsters are osmoconformres, which implies that their blood osmolarity is similar to the environment in which they live. In this lab, we hypothesize that osmoconformity will occur in high salinity manifested as an increase in the osmolarity of hemolymph and in low salinity it will manifest as a decrease in the osmolarity of hemolymph. Therefore this experiment was to determine that lobsters in various salinities will osmoconform to their environment. In order to test that lobster's osmoconform, we had to extract approximately 1.0 ml hemolymph from their hemocyannin on the ventral first section of the pre-branchial region. The hemolymph was spun for three minutes in a microcentrifuge and the serum was then tested on an osmometer, which determined the osmolarity of the hemolymph. The results substantiated the hypothesis, in that, lobsters internal osmoles fluctuate with the salinity of the external environment. The two lobsters in the low salinity tank had the lowest osmolarity 0.746 osmoles; the two lobsters in the normal salinity had 0.873 osmoles. The last tank with the highest salinity had the lobsters with the highest osmolarity at 1.445 osmoles. Therefore our data suggests that lobster's osmoconform, with respect to the salinity of their environment by readjusting their intracellular solute concentration to prevent swelling or dehydration because the osmolarity of their hemolymph dictates that of the environment.