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| Front view into the mouth of an archerfish Image: Sourced from australianmuseum.net.au [Accessed: 30 March 2014] |
Toxotidae is a family of archerfish,
specializing in hunting for insects and small creatures that are land based. There are seven different species in the family Toxotidae. They
are found in a variety of environments, varying from estuaries, river systems,
mangrove forests and even open ocean, and target prey that live in trees or on structures out of the water. They
are known for their ability to capture their prey by spitting quick and
accurate jets of water to knock their prey off their perch. Prey can vary from
flies and beetles to larger prey such as small lizards.
This is an
unusual ability is made possible due to the structure of the fish’s mouth,
which has a narrow groove on the mouth roof. When the fish presses its tongue
against the roof of its mouth, and closes its gills together, water is forced
through and creates a long stream of water, which is used to dislodge prey, and
bring them into the water for easy eating (Schlegel et al, 2006).
There
are several challenges associated with targeting prey that sits at height, out
of the water, when the predators are themselves under the water. The first
issue is the optical properties of the water and air together. When firing a
water jet, the fish must compensate for the refraction and angle of the target
when moving between air and water, and the impact of gravity, as the image
outside the water will appear at a different distance and angle (Temple et al,
2010).
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| Image: Photographer Andrew Lawson [Accessed 30 March 2014] |
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| Image: Sourced from Caters News Agency [Accessed 30 March 2014] |
It has also
recently been found that archerfish are able to precisely calculate the force
at which they deliver their water jet, in response to the size of the prey
target. This would inevitably be an energy conserving method, allowing their
complex hunting method to be less costly. Archerfish were found to identify the
size of larger targets, and deliver larger forces in their water jet, when
compared to smaller targets where they delivered smaller forces in their stream
of water (Schlegel et al, 2006).
Even fish,
which had been raised in an artificial environment, where all advantages or
force related adjustment were removed, were able to fine-tune their water
stream to increase or decrease relative to prey size (Schlegel et al, 2006.
To gain
further understanding of the amazing technique of this little fish, a BBC Earth
video has been posted below.
Note: At 2:00 minutes onwards is a section on Velvet Worms, which is unrelated but still fascinating. Perhaps not recommended for those that aren’t keen on creepy insects with too many legs.
References
Schlegel, T.,
Shmid, C J., Schuster S., 2006, ‘Archerfish shots are evolutionarily matched to
prey adhesion’, Current Biology [Online],
16(9), R836-R837. Available at: http://dx.doi.org.elibrary.jcu.edu.au/10.1016/j.cub.2006.08.082
[Accessed 31 March 2014]
Temple, S., Hart, N S., Marshall, N J., Collin S P., 2010,
‘A spitting image: specializations in archerfish eyes for vision at the
interface between air and water’, Proceedings
of the Royal Society of Biological Sciences [Online], 277, 2607 – 2615.
Available at: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2982040/
Doi: 10.1098/rspb.2010.0345 [Accessed 31
March 2014]
Great blog post and great video. Archer fish are really quite extraordinary in their abilities to accurately hit their prey. Is there any indication of how archer fish are able to compensate for the optical difference between water and air?
ReplyDeleteHi Tasmin, I did a little bit of a read up on this and found that, using microspectrophotometry, researchers were able to characterise photoreceptor absorbance in the eyes of archerfish. Across the retina, archerfish have specially adapted cones and rods to compensate for the spectral differences in both aquatic and arial views. Its especially useful when compensating for backlight which would most likely be a major issue for fish that are always looking up at the sky. Its also suggested this may be found in other surface fish.
DeleteHi. Amazing blog, really interesting! I was just wondering, do different species have their own preffered habitats and prey, or do they hunt everywhere and everything they see? I mean, are they specialized? You are doing a great job, enjoyed reading this blog!
ReplyDeleteHi Marthe, unfortunately I can't really seem to find anything about species being selective and specialised when it comes to prey. I might suggest that they just target whatever they find, which most likely varies based on what kind of environment they are living in. Mangrove forests most likely offer a different array of prey types compared to river systems that are further inland. Thanks for the compliments! :)
DeleteHey Eva have you seen any study where they were able to actually quantify the force that is exerted when they spray? Such a cool video :)
ReplyDeleteHey Dave, in the first study that I cited, there is a table that shows the relationship between the force of the water jet and the type/size of prey. They measured the forces by absorbing and weighing the water that was fired, and also monitored the speeds at which it was fired. I tried to attach the graph, but can't manage to. Would be worth a look though :)
DeleteHi Eva. This reminded me, I've never looked into it but I heard that chameleons hunting with their tongues are able to correct their aim when their vision is distorted by researchers. Great blog, I was going to mention the fishing herons but then I looked over your old posts and saw you were onto it already. Didn't know about the Margay - very interesting. Really cool posts!
ReplyDelete