Using Omics and Behavioural Approaches to Understand Human Impacts on Octopods
Files
(Thesis)
Date
2023
Authors
Hua, Qian Hui Qiaz
Editors
Advisors
Gillanders, Bronwyn
Doubleday, Zoe A. (University of South Australia)
Doubleday, Zoe A. (University of South Australia)
Journal Title
Journal ISSN
Volume Title
Type:
Thesis
Citation
Statement of Responsibility
Conference Name
Abstract
Our world is facing major environmental threats due to anthropogenic causes.
Climate change and overfishing have put immense pressure on our ecosystems which
can have irreversible consequences. Given our reliance on earth’s resources for our
survival, this thesis investigates the fundamental biology and ecology of one key
resource, the octopod, in a bid to understand, and thereby mitigate, the impacts of
anthropogenic pressures on this charismatic and commercially important animal.
Octopus berrima, the main study species in this thesis, constitutes a developing,
small-scale fishery in southeast Australia. However, much information about this
species remains unknown. I thus adopted an “omics” approach to examine their
population genomic structure and their proteomic responses to ocean warming. I also
studied their feeding behaviour to determine how adaptable they are to changing
environmental conditions.
To support sustainable fisheries management, I first genetically identified the
octopod species harvested in South Australia as Octopus berrima and Octopus
pallidus using the universal marker cytochrome oxidase III (COIII). I also found that
these two morphologically similar species could be distinguished using
morphometrics, which could be useful for fishers and fishery scientists. Then, using
double digest restriction site-associated DNA sequencing (ddRADseq), I genetically
compared intraspecific populations of these species across southeast Australia and
delineated two metapopulations of O. pallidus and three metapopulations of O.
berrima. This information is valuable for genomics-based management decisions to
ensure the sustainability of octopod fisheries.
Proteomics is a powerful yet under-utilised tool in ecology that can reveal how
organisms respond to biological perturbations, such as disease and environmental
stress. However, current gold standard methods for sampling and preparing tissues for proteomics analyses are not practical or feasible for many field-based ecological
applications (i.e. immediately freezing samples at -80 °C). The lack of established
protocols for the proteomic analyses of wild specimens, particularly obtained in
remote areas, may be why proteomics is not widely used in ecology. Hence, I
optimised the proteomics workflow by testing the suitability of RNAlater for the field
and various parameters on wild-caught Octopus berrima tissue samples preserved on
ice and in RNAlater. Proteins were detected using SDS-PAGE and liquid
chromatography tandem mass spectrometry. I demonstrated that RNAlater is ideal
for the field as it preserves protein integrity and I also successfully identified high
numbers of proteins (> 3,500) that may contain potential biomarkers for future
ecological research. While proteomic profiles were consistent across sexes and tissue
types, homogenising tissues with steel beads yielded 10 % more proteins than with
liquid nitrogen. These findings demonstrated the possibility of obtaining deep
proteomic coverage on field-caught samples and serves as a first step to establishing
proteomics protocols for studying the effects of environmental stressors on wild
specimens.
As a voracious and versatile predator, octopods feed on a wide variety of crustaceans,
gastropods and bivalves that supports their exponentially high growth rates and “live
fast, die young” life history strategy. Little research has explored behavioural plasticity
with feeding in octopods despite its importance to a species’ ability to adapt to
changing environmental conditions. Despite being commercially targeted, the
preferred prey of Octopus berrima is not known, and neither do we know if their
preference for a certain prey can be modified with imprinting. In an experimental
setting, I allowed newly hatched octopods to select from three prey types to establish
their baseline prey preference ranking. In a separate experiment, I exposed each
group of eggs to visual and chemical stimuli of each of the three prey types, before
testing their prey preference upon hatching. I found that they preferred isopods, followed by amphipods and then mussels. However, regardless of which prey type
the embryos were exposed to, the resulting hatchlings retained their prey preference
of isopods. These findings advance our understanding of behavioural plasticity in
octopods which has ecological and evolutionary significance.
With the predatory role of octopods in the food web as well as an increasing interest
in utilising octopods as an alternative protein source to fish, studying the effects of
ocean warming is important in understanding their capacity to adapt to future oceans,
especially at a vulnerable phase of life in the embryonic stage. Hence, I exposed
Octopus berrima embryos to different thermal conditions (19 °C – control, 22 °C –
current summer temperature, and 25 °C – projected summer temperature in 2100)
and analysed the proteome of the hatchlings using quantitative proteomics. For
octopods exposed to 25 °C, I found significantly reduced levels of key proteins
associated with the eyes, which suggests that future warming could impair octopod
vision. I also found a corresponding increase in the abundance of proteins involved
in the cellular stress response and decrease in those involved in non-essential
processes like digestion, indicating severe signs of stress under future warming. This
study is the first to examine proteomic responses of octopods to increasing
temperatures and these findings suggest that an ecologically and commercially
important species might be at risk in the face of climate change.
Overall, this thesis has examined the population structures of octopods and their
potential vulnerability to future oceans by using omics and behavioural approaches.
New methods and insights developed from this research could assist future research
on octopods, as well as conservation efforts to avoid overexploitation and extinction
of these ecologically, commercially, and culturally important animals.
School/Discipline
Biological Sciences
Dissertation Note
Thesis (Ph.D.) -- University of Adelaide, School of Biological Sciences, 2023
Provenance
This electronic version is made publicly available by the University of Adelaide in accordance with its open access policy for student theses. Copyright in this thesis remains with the author. This thesis may incorporate third party material which has been used by the author pursuant to Fair Dealing exceptions. If you are the owner of any included third party copyright material you wish to be removed from this electronic version, please complete the take down form located at: http://www.adelaide.edu.au/legals