I was fascinated by a report on research on fly ears this morning.
Apparently it was discovered that some members of a parasitic group of
flies (Tachinidae) have auditory abilities that allow them to home in on
their cricket hosts in order to infect them with their minute maggots.
What was so interesting is that it was a mystery how these flies could
locate their hosts when their two ears (located on their "chest" rather
than on their head) are only a millimeter apart and both fact forward.
Well it turns out that the fly _Ormia ochracea_ has an ear that appears
novel in the rest of God's creation. The ears are in fact are internally
connected forming a totally new way of hearing that allows the fly to
determine directionality. These are the only flies that posses true
typanal hearing organs. The complexity of this ear is really amazing and
so I thought to myself, Ah, an example of irreducible complexity. I ran
over to the library and looked up this fly and found a couple of articles.
One in particular is totally fascinating.
"The tympanal hearing organ of a fly: phylogenetic analysis of its
morphological origins." R. Edgecomb, D. Robert, M. Ronald, and R. Hoy.
Cell and Tissue Research (1995) 282:251-268.
Some, but not all flys in the Genus Ormia have this fully developed typanic
membrane system. What is interesting in the paper is that they look at the
close relative of Ormia and find that although they are also parasatoid
they do NOT locate hosts by sound yet they have various portions of what is
a complete ear in the Ormia but are not using it to "hear" their host.
Apparently similar structures in other genera and species are "preadapted"
for hearing:-)
Here is the abstract of the above citation:
Abstract. A key adaption for any parasitoid insect is the sensory modality
that it uses to locate its host insect. All members fo the speciose family
Tachinidae (Diptera) are parasitoids, but only flies of the tribe Ormiini
use acoutsitc cues to find their hosts. Ormiine flies are parasitoids of
various gener of crickets and katydids. Gravid females of one ormiini
species, Ormia achracea, hear the reproductive calling song of male field
crickets and home in on those calls to locate their hosts. While many
flies possess varous kinds of "ears" to detect airborne sounds, only
ormiine flies have been reported to possess true tympanal hearing organs.
Such organs are well-known to occur in their cricket and katydid hosts.
The ormiine ear is an evolutionary innovation within Diptera. Our
objective was to trace the phylogenetic origins of the tympanal hearing
organ among higher flies. Since the ormiine hearing organ is a complex
organ within the prothorax, we examined possible precursor structures in
the prothoraces of selected Diptera. We have uncovered a sutie of
characters that define the ormiine ear. These characters in the prothorax
include a pair of prosternal tympanal membranes, a pair of chordontal
sensory organs, and modifications of the tracheal system. we have been
able to identify and trace the presumptive homologs of these ormiine
characters through selected species of related Diptera, using the method of
outgroup comparison.
end abstract.
I couldn't help but think, what if the relatives of these flies were no
longer living. Would I look at this very unusual organ for hearing and
say, there is not evidence of precursor structures which could have
produced this ear? If any part of this ear is missing the auditory
capability would be lost and thus the whole advantage of hearing the host.
Isn't this possibly a case of irreducible complexity? Or is this an
example where one migh say it is possible an example of irreducible
complexity and thus a candidate for mediate creation but investigation does
allow us to eliminate that possibility in this case? Anyway, a very
intersting example of organ evolution.
Another thing that was intersting about this report is that this ear is now
being studied by an engineer who believes that this ear will be used to
"create" a whole new kind of hearing aid that will be vastly better than
existing ones. I look at this as another example of how God has provided
in creation a blueprint of things that can be used for the improvement of
man's condition. How awesome is out God who's creativity far surpasses our
abilities to comprehend.
Regards,
Joel Duff