Newton, Kyle C.

To fully understand the function of the elasmobranch
electrosensory system it is necessary to examine
electrosensory nerves extending from the ampullae
of Lorenzini to the central nervous system. Studies
detailing the composition of sensory axons are rare,
but they have shown that ontogenetic and sexual
dimorphism exists in the anterior lateral line nerve
(ALLN) of numerous species. This study obtained a
count of the number of axons comprising the ALLN in
male vs. female and adult vs. juvenile yellow stingrays
(Urobatis jamaicensis). We hypothesized that
males have more axons than females, and that the
number of axons is ontogenetically constant. We
expect males to have 30% more axons in their ALLN,
and that the number of axons is ontogenetically constant
for both sexes. This study will provide unique
data about the electrosensory nerves of Yellow
stingrays that can be used in future studies to make
comparisons between other species.

The 3MT® competition celebrates the exciting research conducted by graduate students. Developed by The University of Queensland (UQ), the exercise cultivates students’ academic, presentation, and research communication skills. The competition supports their capacity to effectively explain their research in three minutes, in language appropriate to a non-specialist audience. The first 3MT® competition was held at the University of Queensland in 2008 with 160 students competing. In 2009 and 2010 the 3MT® competition was promoted to other Australian and New Zealand universities and enthusiasm for the concept grew. Since 2011, the popularity of the competition has increased and 3MT® competitions are now held in over 170 universities across more than 18 countries worldwide.

Elasmobranchs (sharks, skates, and rays) migrate across a wide range of
spatiotemporal scales, display philopatry, seasonal residency, and maintain
home ranges. Many animals use the Earth’s magnetic field to orient and navigate
between habitats. The geomagnetic field provides a variety of sensory cues to
magnetically sensitive species, which could potentially use the polarity, or
intensity and inclination angle of the field, to derive a sense of direction, or
location, during migration. Magnetoreception has never been unequivocally
demonstrated in any elasmobranch species and the cognitive abilities of these
fishes are poorly studied. This project used behavioral conditioning assays that
paired magnetic and reinforcement stimuli in order to elicit behavioral responses.
The specific goals were to determine if the yellow stingray, Urobatis jamaicensis,
could detect magnetic fields, to quantify the nature of the magnetic stimuli it could
detect, and to quantify the learning and memory capabilities of this species. The results supported the original hypotheses and demonstrated that the yellow
stingray could: discriminate between magnetic and non-magnetic objects; detect
and discriminate between changes in geomagnetic field strength and inclination
angle; and use geomagnetic field polarity to solve a navigational task. The yellow
stingray learned behavioral tasks faster and retained the memories of learned
associations longer than any batoid (skate or ray) to date. The data also suggest
that this species can classify magnetic field stimuli into categories and learn
similar behavioral tasks with increased efficiency, which indicate behavioral
flexibility. These data support the idea that cartilaginous fishes use the
geomagnetic field as an environmental cue to derive a sense of location and
direction during migrations. Future studies should investigate the mechanism,
physiological threshold, and sensitivity range of the elasmobranch magnetic
sense in order to understand the effects of anthropogenic activities and
environmental change on the migratory ability of these fishes.