Marine Sensory Systems
Claire Walsh and Kim Mroz
CoMPLEX, University College London
Introduction
Electroreception
The marine environment di↵ers from our own in a myriad of ways and surviving it requires
an equally di↵erent set of sensory adaptations. Many marine species have adapted their
sensory systems to this environment in ingenious ways that help them to stand out from the
crowd, navigate the ocean currents and detect prey at long range.
UV Vision
Many fish have extended visual range into the UV
portion of the spectrum. This is thought to provide
a means for these fish to simultaneously stand out
to potential mates and remain inconspicuous to
predators.
Many marine vertebrates, including sharks and rays, possess
the ability to detect electrical stimuli generated by muscle and
nerve activity [2]. This sense assists passive location of hidden
prey in conditions that are problematic for vision and smell.
Consequently, the signals emitted have evolved in some species
to be harder to detect by becoming more complex or consisting
of higher frequencies.
Magnetic Field Navigation
Given the vastness of the oceans and the apparent lack of visible navigational cues, a method of
sensing location and direction is crucial for many
marine animals embarking on long-distance migration routes or simply looking for home.
Figure: Visible and UV fish markings.
Figure: Histogram showing the number of attacks of damsel fish on
their own species (preferred) or other species (non-preferred), with
UV visible and UV filtered scenarios (***= p < 0.001). Note that in
UV light the damsel fish shows a preference for attacking its own
species. Figure and caption taken from [4].
Figure: Electroreceptors of a shark.
Until recently it was thought that only large
bold UV patterns would be discernable, due
to the small proportion of UV cones and
the large amount of scatter of UV in water.
However, the damselfish seems to be able
to identify others by their intricate facial
patterns.
Work carried out by [4] showed that male
Ambon damselfish can discriminate between individuals from their own species
and those of other species. The work
showed that males are more likely to attack
members of their own species as they pose
more competition for mates (see graph to
the left).
Figure: Loggerhead turtle migration route with the
orientation of turtles in Earth’s magnetic field shown at
three widely separated locations. Each dot represents
the mean angle of a single hatchling. The arrow in the
center of each circle represents the mean angle of the
group. Dashed lines represent the 95% confidence
interval for the mean angle. Figure and caption taken
from [1].
Figure: A loggerhead turtle [3]
Loggerhead sea turtles can distinguish between the intensities and angle of inclination at
which geomagnetic field lines intersect the Earth’s surface. This information varies with
location enabling them to build a navigational map of their migratory route.
[1] K.J. Lohmann, C.M.F. Lohmann and C.S. Endres. The sensory ecology of ocean navigation. Journal of Experimental Biology, 211(11):1719–1728, 2008.
[2] T.H. Bullock. Seeing the world through a new sense: Electroreception in fish: Sharks, catfish, and electric fish use low-or high-frequency electroreceptors, actively and passively, in
object detection and social communication. American scientist, 61(3):316–325, 1973.
[3] B. J. Skerry Accessed: 29/05/2012. http://animals.nationalgeographic.com/animals/reptiles/loggerhead-sea-turtle/
[4] U. E. Siebeck, A. N. Parker, D. Sprenger, L. M. Mäthger, and G. Wallis. A species of reef fish that uses ultraviolet patterns for covert face recognition. Current Biology, 20(5):407–410,
2010.