What did the ocean say to the beach?... Nothing, it just waved!
Although the glamour of field work is what most people associate with marine biology, many hours are dedicated to processing samples in the lab to collect data to answer research questions. Over the past few weeks, I have been involved in tons of lab work processing sponge specimens from various locations for taxonomic identification. To taxonomically identify a species means classifying it based on its physical characteristics. A specialized taxonomist and reference to many guides and taxonomic keys is essential to narrow down a specimen to species level. Unfortunately, the ability to accurately identify is often limited to the quality of available identification resources. Needless to say, things can often get a little tricky. What’s interesting is that the specific part of the specimen used in taxonomic identification varies for different groups of organisms. In my case, I am focused on identifying sponge species which is done through looking at intricate skeletal structures.
Halichondria panicea sponge collected from Grand Manan. Credit: Claire Goodwin
Sponges are simple animals that can be an array of various shapes, colours, and sizes. Their phylum, Porifera, means “pore bearing” referring to the many small holes and channels on their bodies. These structures allow sponges to filter water and feed on the tiny organisms and food particles contained in it. As sessile animals, they grow attached to substrate such as rock on the seafloor and cannot move. What I find most impressive about sponges is their remarkably diverse skeletal structures, which you may not expect from such simple creatures. The skeleton is made up of individual microscopic silica glass (or calcium carbonate in some groups) components called spicules that vary in shape and size, unique to each sponge species. Taxonomists rely on these spicules for identification since external appearances can often be misleading. Additionally, the arrangement of the spicules within the skeleton can also be a valuable characteristic for taxonomy.
Some of the various spicule types found in sponges. Credit: Lukowiak et al., 2013
To get a close look at the spicules of a sponge, some preparation must be done in the lab. This is where I come in! Each sponge specimen collected goes through two processes before identification is possible. First, sponge spicules are extracted from the sponge tissue (spongin) by placing a small piece into bleach. The bleach dissolves all the tissue surrounding the skeleton, leaving behind a solution full of only spicules. After a few rinses with water and 95% ethanol, the spicule solution is dropped onto a microscope slide. A few drops of a transparent glue made from balsam trees is placed over the spicules and a cover slip is secured on top (yes, the glue smells like a Christmas tree). The second step involves taking a tissue sample of the sponge by slicing an extremely thin section through its outer surface and inner layer. This tissue sample is placed in clove oil (which also has a Christmassy smell), clarifying the tissue to make it appear more transparent. Once clarified, the sample is placed on the same microscope slide, coated by more balsam glue, and sealed beneath a cover slip.
Spicule preparation. Credit: Sandra Jaskowiak
Tray of microscope slides with sponge spicule preps and tissue samples. Credit: Sandra Jaskowiak
Three trays of microscope slides later, I moved to the lab microscope to photograph, measure, and describe the spicules of each individual specimen. These were then grouped based on similar spicule structures and identified accordingly to most recent species descriptions. Once identified, species names are updated in a specimen catalogue which will later be assigned a DNA barcode following DNA analysis.
Spicule prep (left) and tissue sample (right) of a Halichondria panicea sponge under a microscope. Credit: Sandra Jaskowiak
I hope that you’ve been able to learn something new from my blog over the past few weeks. Unfortunately, this will be my final post but I am so happy for the opportunity to share what I have been up to at Huntsman Marine over these few months. If you have any questions for me or would like to connect, feel free to reach out at email@example.com.