Sea urchin gametes are an excellent model for observing vertebrate development. Sea urchins are a low cost species that can be maintained in a laboratory environment, have external fertilization and have distinct stages for viewing development in offspring. They are external breeders, so when the gametes are mature, they are released into seawater. The seawater carries the gametes where they will fertilize and develop. How does the sperm find the eggs? The jelly coating on the mature eggs produce a chemical signal that attracts sperm (Gilbert, 2000). This method of sperm finding egg must have a protection mechanism for the right sperm to find the right egg. The sea urchins have a particular bindin receptors that look specifically …show more content…
The instructor brought forth three sea urchins from the tank in the back of the room. The three sea urchins were then injected with .5M of potassium chloride (KCl) and placed mouth up into a 120 mL of seawater. After waiting for 10 to 15 minute time interval there was no reaction from the sea urchins. The lab instructor injected another .5M of potassium chloride (KCl) and placed into 120 mL of sea water mouth up. Once all three were placed into containers with the seawater solution they started to expel gametes approximately 10 minutes later.
The first sea urchin to expel gametes was male as were the second and third. With three males and no females we were instructed to observe eggs from the previous class. These eggs were stored at 4 degrees C in the refrigerator. While there had been twelve sea urchins prior to the lab: one tested on Friday, four died over the weekend, four were used on Monday, and three on Tuesday. The eggs were collected from the previous class’s one female out the four used. The eggs were observed on a microscope at 10X magnification. We were instructed to gather information on: size, shape, estimate of amount of eggs in solution. We were also going to place the eggs into sumi ink; however, we did not place the eggs within the ink. Individually we did not do this task, but the instructor did with his and displayed his for the whole …show more content…
It was determined that the eggs were bad and we would not get any plutei larvae from this batch.
Table 1: Gamete Sizes: Difference in egg and sperm size.
Egg size .05 mm
Sperm Size .001 mm
Table 2: Sperm Count: stock solution, 1:1 dilution, plastic container and Sea Uchin.
Stock solution 2,310,000
1:1 dilution 4,620,000
Plastic container 13,860,000
Sea Urchin 1,663,200,00
The size and amount of eggs and sperm produced are vastly different. The amount of sperm produced is a reproduction mechanism to allow the passing of as many of their gametes as possible. The eggs are lager because of the materials needed for embryo growth, so females put more energy into their gametes then males. The eggs in our section were not fertilized because they were 24 hours old. Since fertilization did not occur for our section we did not set up petri dishes to observe the plutei larvae