Bio-imaging the brain to save sawfish
In early 2024, a terrifying phenomenon struck populations of smalltooth sawfish in Florida, USA. Just when the Smalltooth Sawfish Recovery Implementation Team was optimistic that recovery had begun, there were at least 54 confirmed sawfish mortalities, coupled with hundreds of accounts of a fish ‘spinning disease’, with no further explanation. Kara is characterising brain morphology from an existing collection of smalltooth sawfish, using advanced 3D bio-imaging to predict behavioural and sensory shifts throughout life. These invaluable data from healthy smalltooth sawfish form the baseline from which to identify neuro-compromise in individuals afflicted with ‘spinning disease’.
Kara Yopak
I have been captivated by elasmobranchs for as long as I can remember, and my interest continued from the age of five through undergraduate and graduate school to today. I received my BA in biology (with a specialisation in marine science) from Boston University in 2002 and completed my PhD in sensory neuro-ethology at the University of Auckland in New Zealand in 2007. I later went on to postdoctoral appointments at the University of California San Diego and the University of Western Australia. While I started my PhD intent on studying elasmobranch behaviour, it was in Auckland that...
Normal vs. compromised: Can brain organization in healthy smalltooth sawfish inform an unusual mortality event?
Using advanced 3D bio-imaging methods (magnetic resonance imaging, or MRI), this study will characterise the brain in the smalltooth sawfish, including shifts in patterns of brain organisation throughout a lifespan that might bring about changes in sensory specification and behaviour in this species. Data collected from healthy individuals will then serve as a platform upon which we can build a better understanding of a devastating ‘spinning disease’ that has led to an unprecedented number of smalltooth sawfish mortalities in the past year.
Large, severely neuro-compromised smalltooth sawfish are currently dying in South Florida at an unprecedented rate. This project will utilise previously collected brain tissue from unexpected mortalities before and after this die-off in order to identify neural anomalies in the afflicted individuals and hopefully provide a way forward for recovery.
The brain of sharks and their relatives represents an early, yet remarkably complete, stage in the evolution of the vertebrate brain. Previously thought to be primitive, small-brained predators, sharks and their relatives are now known to have relatively large brains and a high degree of variability in the size of major brain regions (termed brain organisation). These differences have been linked to differences in primary habitat, life-history traits and/or specific behaviour patterns, which suggests patterns of brain organisation provide insight into behaviour, sensory specialisation and even ‘intelligence’ between species and/or throughout life in a single species.
Sawfish (Pristidae) make up a family of highly modified rays that are characterised by a saw-shaped rostrum. Due to severe range restriction and population decline in the last century, the smalltooth sawfish <i>Pristis pectinata</i> was added to the US endangered species list on 1 April 2003 and is currently found primarily in south-western Florida. Sawfish are some of the most threatened elasmobranchs in the world and understanding their biology becomes even more critical for conservation efforts. However, for the smalltooth sawfish there is little to no data on patterns of brain growth, which can provide critical information about functional shifts in behaviour and habitat at key life stages. Furthermore, the brain can often serve as a ‘bio-indicator’, which enables us to identify neural anomalies that might underlie disease or responses to environmental change.
The Florida Fish and Wildlife Conservation Commission (FWC) has been conducting research on smalltooth sawfish since 2004. In recent years, the Smalltooth Sawfish Recovery Implementation Team was optimistic that recovery had begun in the USA. However, since early 2024 there have been at least 54 confirmed sawfish mortalities, coupled with hundreds of accounts of a fish ‘spinning disease’, with no current explanation.
Identifying the cause and neural underpinnings of this abnormal behaviour is critical for the survival of the smalltooth sawfish in Florida waters. This study aims:
- To characterise brain morphology from an existing collection of healthy smalltooth sawfish, using advanced 3D bio-imaging that enables us to predict behavioural and sensory shifts throughout life.
- To form a baseline from these invaluable data from which to better identify key regions of neuro-compromise in individuals afflicted with this unexplained ‘spinning disease’.
- To use bio-imaging data to develop 3D printed models of the brain for use in teaching and outreach.