SEMINAR: CWR Presents

Cartilaginous fishes are comprised of approximately c. 1185 species worldwide and occupy a range of niches and primary habitats. It is a widely accepted view that neural development can reflect morphological adaptations and sensory specializations and that similar patterns of brain organization, termed cerebrotypes, exist in species of that share certain lifestyle characteristics. Clear patterns of brain organization exist across cartilaginous fishes, irrespective of phylogenetic grouping.

Examination of brain size (encephalization, n = 151) and interspecific variation in brain organization (n = 84) across this group suggests that chondrichthyan brain structures might have developed in conjunction with specific behaviours or enhanced cognitive capabilities. Larger brains, with well-developed telencephala (associated with spatial learning and memory) and large, highly foliated cerebella (associated with motor control) are reported in species that occupy complex reef or oceanic habitats, such as Prionace glauca and Sphyrna zygaena. In contrast, benthic and benthopelagic demersal species comprise the group with the smallest brains, such as Cephaloscyllium spp. and Squatina californica, with a relatively reduced telencephalon and a smooth cerebellar corpus.

There is also evidence of a bathyal cerebrotype; deep-sea benthopelagic sharks, such as Centroselachus crepidater and Harriotta raleighana possess relatively small brains and show a clear relative hypertrophy of the hindbrain and the structures that receive non-visual sensory input. Using this broad dataset, this talk will explore how brain morphology may serve as a tool to make predictions about the behavioral ecology, sensory specialization, and predatory habits of species that are difficult to acquire and/or study in the wild.

I will also discuss the development of new techniques, such as magnetic resonance imaging (MRI), and its impact to the field of comparative marine biology. While it does not have the spatial resolution of histological data, MRI offers distinct advantages over traditional methods by allowing for in situ brain imaging of rare specimens where gross dissection is difficult or impossible. In a case study, the brain size and brain organization in the large-bodied whale shark, Rhincodon typus, is described, where I investigate the digital reconstruction of rare, damaged specimens and discuss the advantages, drawbacks, and future of MRI in comparative neuroanatomical studies.



Biography,

Dr. Kara E. Yopak’s (née) research focuses on the evolution of neural systems, particularly how brains have diversified within some of the earliest vertebrate groups, namely sharks, skates, rays, and chimaerids, a group collectively referred to as Chondrichthyans. Dr. Yopak received her B.A. in Biology (with a specialization in marine science) from Boston University in 2002 and completed her PhD at the University of Auckland in New Zealand in 2007. For her PhD and beyond, Dr. Yopak’s research has focused on comparative neuroanatomy within the clade of cartilaginous fishes, and how the development of major brain areas vary between species in conjunction with the adaptive evolution of their sensory and motor systems.

She has explored a variety of traditional and novel techniques to explore questions related to brain evolution of sharks and their relatives, including magnetic resonance imaging (MRI). Her data suggest that brain organization and the relative development of major brain structures reflect an animal’s ecology, even in phylogenetically unrelated species that share certain lifestyle characteristics, a pattern similarly documented in other vertebrate groups.

She is currently working within the Neuroecology Group, within the School of Animal Biology at UWA. Here she is exploring a multitude of questions relating to brain development, including how the brain, major brain components, and cell classes within these brain components scale across this unique group of animals. This work will potentially highlight a developmental plan that originated at least as early as cartilaginous fishes and may have been carried through evolutionary time to mammals. In addition, she is investigating whether alterations during early development in these animals can lead to changes in brain development, and by extension cognitive capabilities. This work could have far reaching implications for preservation of Australia’s biodiversity, particularly for improving survival strategies for captively-reared endangered species.



PS* This seminar is free and open to the public & no RSVP required.

****All Welcome****