Grazer-induced Bioluminescence and Toxicity in Marine Dinoflagellates
(2024) BION03 20232Degree Projects in Biology
- Abstract
- Marine copepods are the most abundant type of zooplankton of the ocean in terms of biomass. They imprint their surrounding waters with a unique signature of chemical compounds, out of which copepodamides stand out. These polar lipids are recognized by some phytoplanktonic species, who induce defensive traits in response, including bioluminescence and toxin production, colony size plasticity or structural modifications. Even though it is thought that this predator-prey relationship is generalized within the phytoplankton, the extent of species known to detect and react to copepodamides is unknown. Here, I have studied bioluminescence and toxicity as a grazer-induced response to increasing concentrations of copepodamides in three species of... (More)
- Marine copepods are the most abundant type of zooplankton of the ocean in terms of biomass. They imprint their surrounding waters with a unique signature of chemical compounds, out of which copepodamides stand out. These polar lipids are recognized by some phytoplanktonic species, who induce defensive traits in response, including bioluminescence and toxin production, colony size plasticity or structural modifications. Even though it is thought that this predator-prey relationship is generalized within the phytoplankton, the extent of species known to detect and react to copepodamides is unknown. Here, I have studied bioluminescence and toxicity as a grazer-induced response to increasing concentrations of copepodamides in three species of marine dinoflagellates: bioluminescent Protoceratium reticulatum, paralytic shellfish toxin (PST) producing Gymnodinium catenatum and PST producing and bioluminescent Alexandrium catenella. I also measured the trade-offs that these traits might imply as reductions in growth rates. All three species of dinoflagellates significantly upregulated their defensive traits upon copepodamide exposure, adding these to the list of species capable of detecting and reacting to grazer cues. Moreover, no reductions in growth rates were observed. (Less)
- Popular Abstract
- Fight or flight – Diving into the defense mechanisms of marine dinoflagellates
Tiny yet fundamental organisms of the ocean, the phytoplankton, are subject to a daily strong predation threat from zooplankton. In response, phytoplankton have developed the ability to “smell” or sense their predator in the environment and defend themselves against it. They can do so by inducing traits such as bright bioluminescent flashes or producing toxicity. These are thought to act as defense mechanisms, since they can be effective at deterring zooplankton away. This capacity of sensing predators in the environment is thought to be general within the phytoplankton, but the extent of species capable of doing so remains unknown. This project sheds some... (More) - Fight or flight – Diving into the defense mechanisms of marine dinoflagellates
Tiny yet fundamental organisms of the ocean, the phytoplankton, are subject to a daily strong predation threat from zooplankton. In response, phytoplankton have developed the ability to “smell” or sense their predator in the environment and defend themselves against it. They can do so by inducing traits such as bright bioluminescent flashes or producing toxicity. These are thought to act as defense mechanisms, since they can be effective at deterring zooplankton away. This capacity of sensing predators in the environment is thought to be general within the phytoplankton, but the extent of species capable of doing so remains unknown. This project sheds some light on this question by studying how three different species of dinoflagellates react to natural concentrations of copepodamides.
The planktons are aquatic organisms who are incapable of swimming against the ocean currents and, consequently, simply drift in the water. A huge fraction of these, the phytoplankton, are composed of microscopic photosynthesizing organisms who harness the sun´s light to create organic matter and oxygen. Despite their small size, they account for ~50% of the oxygen we breathe and serve as the basis of the aquatic food web. Their main predator is the animal fraction of the plankton: the zooplankton. Copepods are the most abundant species of zooplankton and, unknowingly, release a molecule into their surrounding water called copepodamides. Phytoplankton have evolved to detect these molecules as “danger”, meaning that their enemies are close by. As a response, they can display different defense strategies such as armoring themselves by thickening their outer layers, developing spines, changing their colony size, emitting bright bioluminescent flashes, or even producing toxicity. Predators, on the other hand, can selectively choose their prey, and prefer not to feed upon the “protected” organisms. This allows the defended phytoplankton species to thrive and survive, so much that they may become dominant in the location they are found at. If they overgrow, they can produce harmful algal blooms (HABs), commonly known as “red tides”, which can cause great environmental problems.
The amount of phytoplanktonic species that can recognize these copepodamide molecules and defend themselves is unknown, and although scientist suspect this to be a common trait within the phytoplankton, more research is needed. For this reason, I explore if three different species of dinoflagellates, a type of marine phytoplankton that commonly forms HABs, can detect and react to copepodamides. Two of them, Alexandrium catenella and Protoceratium reticulatum, are bioluminescent. Another two, Alexandrium catenella and Gymnodinium catenatum, produce a set of very potent toxins called paralytic shellfish toxins.
Methods
To conduct this project, I perform what’s known as “dose-response” experiments. Cells of the different dinoflagellate species are individually grown in glass tubes. These are previously coated with copepodamides in an increasing manner, i.e. tubes ranged from lower concentration to higher. For each species, there are a few glass tubes without copepodamides, and serve as control to estimate the basal level of toxicity and bioluminescence expressed by the cells. Bioluminescence is measured with an instrument called “luminometer”, and toxins are extracted through a process of centrifugation, freeze-drying, and chemical analysis.
Results and Discussion
Bioluminescence and toxicity were successfully induced as a response to naturally occurring concentrations of copepodamides in all our species, adding three new ones to the list of species capable of detecting and reacting to copepodamides. This further supports the idea that copepodamide recognition within the phytoplankton is a general trait. Moreover, the fact that phytoplankton can detect and react to a unique chemical cue released by their predators, and that this deters copepods, indicates that the traits they induce serves as a defense mechanism. Learning about this predator-prey relationship will allow us to better understand some of the factors that contribute to harmful algal bloom formation, as well as the ecological dynamics of the ocean.
Master’s Degree Project in Biology 60 credits 2024
Department of Biology, Functional Ecology Division
Lund University
Supervisor: Erik Selander (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9175841
- author
- Gonzalo Valmala, Paula Isabel
- supervisor
- organization
- course
- BION03 20232
- year
- 2024
- type
- H2 - Master's Degree (Two Years)
- subject
- language
- English
- id
- 9175841
- date added to LUP
- 2024-10-24 14:35:29
- date last changed
- 2024-10-24 14:35:29
@misc{9175841,
abstract = {{Marine copepods are the most abundant type of zooplankton of the ocean in terms of biomass. They imprint their surrounding waters with a unique signature of chemical compounds, out of which copepodamides stand out. These polar lipids are recognized by some phytoplanktonic species, who induce defensive traits in response, including bioluminescence and toxin production, colony size plasticity or structural modifications. Even though it is thought that this predator-prey relationship is generalized within the phytoplankton, the extent of species known to detect and react to copepodamides is unknown. Here, I have studied bioluminescence and toxicity as a grazer-induced response to increasing concentrations of copepodamides in three species of marine dinoflagellates: bioluminescent Protoceratium reticulatum, paralytic shellfish toxin (PST) producing Gymnodinium catenatum and PST producing and bioluminescent Alexandrium catenella. I also measured the trade-offs that these traits might imply as reductions in growth rates. All three species of dinoflagellates significantly upregulated their defensive traits upon copepodamide exposure, adding these to the list of species capable of detecting and reacting to grazer cues. Moreover, no reductions in growth rates were observed.}},
author = {{Gonzalo Valmala, Paula Isabel}},
language = {{eng}},
note = {{Student Paper}},
title = {{Grazer-induced Bioluminescence and Toxicity in Marine Dinoflagellates}},
year = {{2024}},
}