Student article – Discovering Living Light
Discovering living light – Heather Emberson-Marl age 18
Ysgol y Preseli Pembrokeshire
Key Words: Bioluminescence; hydroid; Obelia, Darwin Centre, brittle star
I attended several Darwin Centre workshops as part of the “Discovering Living Light” project. In 2016, I was lucky enough to have my brain lit up by bioluminescence. My journey of discovery started with an adventure into the lab and dark rooms at Welston Court Science Centre with Professor Anthony Campbell, and Dr Valerie Morse. It was my first steps into the world of creatures that can ‘flash’ in the dark – by amazingly making their own light. I also learnt the difference between bioluminescence and fluorescence and the fact that they both have applications in medicine. Eventually this would lead me to discover bioluminescence for myself by snorkelling for samples and finally extracting a magic protein that I triggered with calcium ions to light up, under the watchful eye of Dr Valerie Morse, a lover of hydroids and all things bioluminescent.
Having seen and measured bioluminescence and fluorescence in the workshop at Welston Court, I then wanted to see if I could find bioluminescent or fluorescent marine organisms at two different sites in Pembrokeshire. The sites were St Brides bay and Milford Haven marina. A second aim was to determine if I could extract photoprotein from any bioluminescent hydroids that I found.
Background to bioluminescence
Living light or bioluminescence is light production from the mixing of chemical components in living creatures. These creatures can include jellyfish, hydroids, sea pens and brittle stars (Morse, 2013).
What are the components of the light reaction?
The components of the light reaction are; luciferin, luciferase and oxygen. In a classic bioluminescent reaction, marine organisms like the sea pansy mix these components together to produce light. The enzyme luciferase catalyses the reaction (Campbell, 2003). A more recent discovery is that the hydroid Obelia geniculata contains a photoprotein, which has the key components for the reaction bound together.
In the presence of calcium ions, a photoprotein will emit blue light. The first photoprotein was discovered in the jellyfish Aequeorea and is called aequorin. Osamu Shimomura (1987) discovered aequorin (Morse, 2013).
Two of the bioluminescent species that I found in Pembrokeshire are hydroids.
What are hydroids?
Hydroids are a life stage of most animals in the class Hydrozoa, in the phylum Cnidaria. and are predators related to jellyfish. Hydroids can appear as branched plants or jelly fish like animals, they are colonial animals, meaning that what appears to be one organism, is in fact many smaller organisms living together to create a colony. Hydroids are often in branching forms, the polyps are surrounded by a shell of chitin. The central stalk that is attached to a hard surface, will appear to grow branches. The life cycle of a hydroid such as Obelia includes two life stages; a mainly stationary polyp phase and a free moving medusa phase. These organisms will spend most of their life in polyp form, of which there are two types, a feeding polyp termed a hydranth and reproductive polyp, called a gonotheca (Morse, 2013).
Sample collection at St Brides
To collect samples of marine creatures at St Brides bay my aim was to find the oar weed Laminaria and look for the fine hair like strands of Obelia. Snorkelling was an ideal observation tool due to most of the Laminaria being submerged in deep water. Brittle stars are found in the holdfasts of Laminaria so I looked for those as well. My friend Angharad used an underwater “go pro” to film the marine life in the bay. I was accompanied by a friend, my mum, and Valerie Morse for safety reasons.
Collecting samples at Milford Haven Marina
Samples were obtained from weighted boards and ropes positioned in Milford Haven marina (Morse, 2013).
To identify and photograph specimens we used a binocular microscope and Panasonic camera at the Darwin Centre research lab, and at Welston Court Science centre.
Extraction of Photoprotein
I used a method established by Prof Anthony Campbell for this (Campbell, 1974).
Determining which species were fluorescent
To view fluorescence in marine specimens I used the Hund microscope at Welston Court Science centre.
To test the brittle star Amphipholas squamata, for bioluminescence we used the Photek imaging camera at Welston court.
Determining which species were bioluminescent
Bioluminescence was measured by using a chemiluminometer. A specimen was placed in a small LP 3 tube, which was then inserted into the chemiluminometer. Potassium ions are then added to trigger bioluminescence. The chemiluminometer contains a photomultiplier tube, which counts the photons coming from the marine creatures.
Marine species identified from St Brides Bay
Green fluorescent protein in the photocyte of Obelia longissima a bioluminescent hydroid which lives in Milford Haven marina, magnification X1000.
A brittle star Amphipholas squamata, found at St Brides and identified using the light microscope at Welston Court Science Centre. The bioluminescence was confirmed by recording it on the Photek imaging system.
A Blue ray limpet from St Brides bay.
A marine gastropod mollusc from the patellidae family. I thought this was fluorescent due to green fluorescent protein. I have now found out that its fluorescence is due to materials in its shell (Ling and Kolle, 2015).The fluorescence fades in adult specimens.
Marine species identified from Milford Haven marina
There was a small light response from the scale worm: it may therefore be a bioluminescent species.
Light production from the photoprotein obelin
Average counts per second from the obelin photoprotein I extracted from Obelia longissima. The photo protein produced less light when stimulated by calcium ions than was expected. However, results show that the bioluminescent hydroid Obelia longissima, in Milford marina does contain the photoprotein.
Presenting my results
In 2017 I presented a summary of my project at the Milford Haven Port authority to an audience that included Prof Campbell and Dr Stephanie Matthews. Speaking in front of a larger audience was a nerve wracking, but a very valuable experience.
I found 4 different bioluminescent species at the two sample sites. I also found a scale worm that was possibly bioluminescent, and I would like to go on to discover if it has a photoprotein.
I recorded the bioluminescence of Amphipholis squamata using the photek imaging system, with the guidance of Prof Campbell, and this showed me that the light producing cells (photocytes) are in the tentacles, of the specimen and not in the central disk. I found two bioluminescent species of hydroid Obelia longissima and Obelia geniculate. Both species were also fluorescent because they contain green fluorescent protein. I have now found out that this protein is in Obelia’s light producing cells and changes the wavelength of its bioluminescence from blue to green. Another hydroid Dymena pumila was not bioluminescent or fluorescent but this species can act as a useful control when conducting experiments. I successfully extracted obelin from Obelia longissima and it did produce a maximum of 5200 counts per second in the chemiluminometer. This was a relatively low reading so it is well worth repeating this experiment at different times of the year. Obelin is an important photoprotein because it can be used to measure calcium ions in living cells (Campbell, 2018).
The blue ray limpet was fascinating. I initially thought it would contain GFP but I have now found out that the fluorescence is due to materials in its shell (Ling and Kolle, 2015.The fluorescence fades in adult specimens.
This project has allowed me to develop my scientific skills particularly in microscopy, imaging and identification of marine specimens. These will be very useful to me when I go to University. I have also learnt a great deal about how to write up and present scientific experiments. Some of the experiments I only carried out once due to the time available, but I now know that experiments have to be conducted in triplicate and an average taken to produce accurate results.
The hydroids and brittle star were so beautiful under the microscope that they inspired me to use them in my Art A level coursework. I made my notes on them in Welsh because I am a Welsh speaker and the language is very important to me.
Thanks are due to Dr Valerie Morse for guiding me through experiments and advice about presenting and writing up my results. I would also like to thank Prof Campbell for all his help and my friend Anghared Noakes who helped me snorkel for samples and also took part in experiments at the Darwin research lab.
- Campbell, AK (1988). Chemiluminescence: principles and applications in biology and medicine, pp608. Horwood/VCH, Chichester and Weinheim. ISBN 3-527-26342-X. 0 7156 2499 7.
- Campbell, AK (1994). Rubicon: the fifth dimension of biology. pp 304. Duckworth, London, 0 7156 2499 7.
- Campbell, AK (2018). Fundamentals of intracellular calcium, Wiley, Chichester.
- Campbell, AK (2003). Save those molecules! Molecular biodiversity and life. Journal of Applied Ecology. 40:193-203
- Campbell, AK (2003). Rainbow Makers. Chemistry in Britain June 2003:30-33
- Ling and Kolle 2015
- Morse, VJ (2013). The regulation and origin of bioluminescence in the hydroid Obelia. Thesis Cardiff University.
- Shimomura (1987) or his book