1. The Settlement of Haliotis rufescens Red Abalone
Larvae on Varying Substrates
Statement of Problem
Methods
Results
Discussion
As settlement is a key stage in the maturation of abalone larvae, which substrate will promote the greatest settlement of the larvae?
As a result of this study, the substrate with the highest amount of settlement is the acrylic tank surface, commonly used in tanks for captive abalone.
This data could be a result of an evolutionary relationship. As generations have passed throughout the nursery at Cabrillo, their populations have adapted to the acrylic surface.
Therefore, the result of the highest settlement on the acrylic tile is a possible result of the adaptation to the acrylic tank surfaces over time, becoming a preference for settlement for the red abalone larvae.
This data can be applied throughout the nursery when raising abalone larvae. Instead of using plastic buckets, acrylic surfaces can be used to increase the rate of settlement and allow the settlement to occur within a more condensed area, thus more larvae can be maintained instead of lost through actions including transporting the larvae from different containers.
The larvae were separated into three equal groups after fertilization and were placed into the clear buckets.
Water changes were conducted each day for a week. After a week, the larvae reached the settlement stage after hatching.
Larvae were collected from each of the three clear buckets and were counted out into nine separate groups of approximately fifty larvae.
Each group of the fifty larvae were then placed into the nine different crystallizing dishes. Each dish contained one of the three substrates that had been sitting in salt water overnight to achieve a biofilm layer.
The larvae were then allowed to settle overnight. The next day they were placed under a microscope and the amount of larvae in the negative area were counted.
Introduction
Vesicular lava and coarse sandstone are not appropriate substrates, and artificial substrates such as cinder block are inappropriate surfaces for larval settlement as well. However, sedimentary rock of fine grain composition, such as claystone and siltstone, slate and limestone, or ceramic tiles, are found to be the best substrates for settlements for all settling stages.
Plastic materials commonly used in the hatchery may be readily accepted by settling larvae when placed in the natural environment.
My hypothesis is that by using varied substrates such as ceramic tiles, common tank acrylic surfaces, and PVC plastic piping, then the ceramic tiles will have the most successful red abalone settlement rate as it is a naturally occurring settlement site in abalones’ natural habitat. .
Table 1: This graph displays the varying averages of the amount of red abalone that settled on the positive area (substrate) of each of the crystalizing dishes.
Figure 1: A single red abalone larvae under the microscope with a forming radula. Photo taken by author
Figure 2: Set up of the nine crystallizing dishes
with the varying substrates. Photo taken by author
Further Implications
The use of acrylic surfaces when allowing settlement for larvae abalone can not only be applied to the red abalone within the aquarium,
but also the captive born and raised white
abalone, a cousin species.
With the promotion of settlement, the larvae of the white abalone will be able to able to more successfully grow into the juvenile stage, leading to further maturation and possible success in reproduction, thus re-establishing the endangered species.
Materials
The substrates that were required for this study were: ceramic tiles, PVC piping, and acrylic petri dishes (the control). Other materials that were required include clear buckets of 20 liters, nine crystalizing dishes that are approximately 2.75 inches tall and 3.5 inches wide, soft tubing, ridging tubing, three oxygen pipe lines (provided by the Cabrillo Aquatic Nursery), beakers, a microscope, a counting dish, and the red abalone larvae.
Figure 3: Red abalone larvae under the microscope. Live larvae are green and clear shells are nonliving larvae. Photo taken by author
Table 2: This graph displays the varying averages of the amount of red abalone that settled in the negative area (crystalizing dish).
Figure 4: Counting larvae under the microscope. Larvae are in a petri dish substrate Photo taken by author
All photos taken by author.