Echinodern Echinarachnius parma Development Lab
Ella Spungen ('19)
Introduction
Echinarachnius parma, commonly known as the sand dollar, is generally found along the Atlantic coastline, North of Long Island, on sandy bottoms in shallow water. E. parma uses it spines for both movement and to bury itself in sand. The sand dollar is a deposit feeder, often eating organisms such as diatoms and detritus on the sandy bottom. It uses its tube feet to eat, to move, and to respirate.
The reproduction of E. parma is external - both male and female sand dollars release gametes during approximately the same time period and in a concentrated area. E. parma generally reproduces during late summer and early fall. Reproduction is purportedly triggered by two factors: one, an increase of salinity in the water, and, two, the presence of other gametes in the water. When one sand dollar begins producing gametes, triggered by the increase of salinity, other sand dollars in the area sense these gametes and begin releasing their own gametes. When the gametes - both eggs and sperm - are released, they find each other in the water and begin fertilization.
There are both challenges and benefits of external fertilization. One of the challenges is the fact that the gametes, once released, are very vulnerable as a food source to predators. In addition, the gametes can often become dispersed within the ocean quite easily, making it difficult for the male and female gametes to find each other. To counteract these challenges, E. parma produces a large amount of gametes in the same area, so it is easier for the gametes to find each other. Finally, the larva of E. parma is planktonic, allowing for wide dispersal to lessen competition for food and resources. The purpose of this lab was to observe the reproduction process of Echinarachnius parma.
Methods and Materials
First, a 20 ml beaker was filled to the brim with salt water and placed onto a tray to avoid spillage. One E. parma was removed from a tank filled with unused sand dollars and placed, aboral side down, on top of the beaker. A syringe was used to inject 10 ml of .5 M potassium chloride into the oral cavity of E. parma to stimulate the release of gametes. If a milky stream was seen, the sand dollar was male and releasing sperm. If red eggs were seen, the sand dollar was female. If a green substance was seen, the sand dollar was immature and unable of producing gametes. The eggs and sperm were both diluted, and the diluted eggs were placed on a slide and observed under a compound scope without clips on 100x magnification (Fig 1). Then, a drop of diluted sperm was placed on the same slide and the zygote was observed under the scope (Fig 2). A certain period of time passed, and the two cell stage (Fig 3) and four cell stage (Fig 4) were observed.
Echinarachnius parma, commonly known as the sand dollar, is generally found along the Atlantic coastline, North of Long Island, on sandy bottoms in shallow water. E. parma uses it spines for both movement and to bury itself in sand. The sand dollar is a deposit feeder, often eating organisms such as diatoms and detritus on the sandy bottom. It uses its tube feet to eat, to move, and to respirate.
The reproduction of E. parma is external - both male and female sand dollars release gametes during approximately the same time period and in a concentrated area. E. parma generally reproduces during late summer and early fall. Reproduction is purportedly triggered by two factors: one, an increase of salinity in the water, and, two, the presence of other gametes in the water. When one sand dollar begins producing gametes, triggered by the increase of salinity, other sand dollars in the area sense these gametes and begin releasing their own gametes. When the gametes - both eggs and sperm - are released, they find each other in the water and begin fertilization.
There are both challenges and benefits of external fertilization. One of the challenges is the fact that the gametes, once released, are very vulnerable as a food source to predators. In addition, the gametes can often become dispersed within the ocean quite easily, making it difficult for the male and female gametes to find each other. To counteract these challenges, E. parma produces a large amount of gametes in the same area, so it is easier for the gametes to find each other. Finally, the larva of E. parma is planktonic, allowing for wide dispersal to lessen competition for food and resources. The purpose of this lab was to observe the reproduction process of Echinarachnius parma.
Methods and Materials
First, a 20 ml beaker was filled to the brim with salt water and placed onto a tray to avoid spillage. One E. parma was removed from a tank filled with unused sand dollars and placed, aboral side down, on top of the beaker. A syringe was used to inject 10 ml of .5 M potassium chloride into the oral cavity of E. parma to stimulate the release of gametes. If a milky stream was seen, the sand dollar was male and releasing sperm. If red eggs were seen, the sand dollar was female. If a green substance was seen, the sand dollar was immature and unable of producing gametes. The eggs and sperm were both diluted, and the diluted eggs were placed on a slide and observed under a compound scope without clips on 100x magnification (Fig 1). Then, a drop of diluted sperm was placed on the same slide and the zygote was observed under the scope (Fig 2). A certain period of time passed, and the two cell stage (Fig 3) and four cell stage (Fig 4) were observed.
