Nov 09 2010 | Posted by SSBibek

Shark Eye Research Gives Insight Into Ocean Health

The joint study between researchers at The University of Western Australia and The University of Queensland looked at the visual adaptations of four species of wobbegong sharks, which are also known as carpet sharks.

The study examined the western wobbegong (Orectolobus hutchinsi) and the dwarf spotted wobbegong (Orectolobus parvimaculatus, which are both found off Western Australia, as well as the ornate wobbegong (Orectolobus ornatus) and the spotted wobbegong (Orectolobus maculatus) found off Queensland.

The researchers found that the eyesight of the western and ornate wobbegongs was suited to both day and night activities, whereas the spotted and dwarf spotted wobbegongs were better adapted to low light conditions.

WA Premier’s Research Fellow and Winthrop Professor Shaun Collin, Associate Professor Nathan Hart and UQ’s Dr Susan Theiss said the results would lead to a better understanding of the sensory systems of marine life and help scientists better predict reactions to a change in light conditions.

Dr Theiss said the sharks’ visual adaptations were linked to factors such as their diet, habitat, whether in shallow or deep waters, and their reproductive behaviours.

“This research is important in establishing general trends and predictions in biogeography and ecology that we don’t yet have data for,” Dr Theiss said. 

“If we can understand their habitat, we can extrapolate and make informed decisions about other sharks and rays and how they are able to survive in different light environments.

“It appears that the wobbegong species we studied have different visual adaptations that could be linked to times of increased activity.  For example, the spotted and dwarf spotted wobbegongs are probably more active in low-light conditions such as night time, or in the early morning or late afternoon, whereas the western and ornate wobbegongs are visually suited to a range of light conditions.”

Professors Collin and Hart – who were involved with the research while at the University of Queensland and are continuing it with UWA’s School of Animal Biology and UWA’s Oceans Institute – said wobbegongs were fairly common in the temperate waters of the continental shelf and could give an insight into how these key indicator species may be used to monitor the marine environment.

“Almost nothing is known about the behaviour of wobbegongs, but what our research on the visual systems can do is predict their behaviour, so we look at the shark’s visual system at the level of the photoreceptors, which are the cells that detect light,” Professor Collin said.

“If you see these common species interacting and behaving normally in a particular environment, this can be a good indicator of the health of that part of the ocean.”

He said wobbegongs were not man-eaters although they could inflict a nasty bite if someone stepped on them.  They also had a different feeding pattern to most other sharks which were often fast moving and sought out their prey.

“Wobbegongs do the opposite, they are lie-in-wait predators that use camouflage and allow animals to come to them,” he said.

“They’ve even got some ‘dermal appendages’ that come off the front of their head which may even be mistaken for some sort of a lure, so animals come close and get taken very quickly by their fast-acting jaws.”

The findings of the research are featured in the paper “Visual adaptations among wobbegong sharks”, which is co-authored by Dr Theiss, Associate Professor Nathan Hart and Professor Collin.

The paper will be published in the journal Brain, Behaviour and Evolution.