[Pollinator] [beemonitoring] Hummingbird "sweet genes"

[Lisa Horth]

Peter -

This is interesting too and suggests that possibly the hexose-rich nectar
using orioles, honeyeaters and sunbirds would have a T1R1 that has evolved
slightly differently from hummers T1R1 if hexose tastes different from the
sucrose-rich hummer foods. That is pretty easy to test now that the
groundwork has been laid for the T1 receptors in birds!

Lisa


On Mon, Aug 25, 2014 at 9:34 AM, Peter Bernhardt <bernhap2 at slu.edu> wrote:

> Dear Lisa:
>
> That's very interesting.  There's also a question of digestion.  I do
> remember some publications about 20 years ago about the ability of birds to
> digest sucrose.  Apparently, many passerines like the enzyme sucrase. Their
> systems can't split the molecule and they either derive no energy or it's a
> dangerous feed for them.  That's why you are not supposed to give a pet
> canary a sugar lump.  This is also supposed to explain why so many small
> berries are hexose rich and low in sucrose.  More important for us, nectar
> analyses of flowers pollinated by orioles, honeyeaters, sunbirds etc. were
> hexose rich or dominant.  In contrast, most hummingbird nectars are sucrose
> rich/dominant.  I wish I could remember the authors of these articles but
> someone in our group should know.
>
> Peter
>
>
> On Sun, Aug 24, 2014 at 11:45 AM, Lisa Horth <lisahorth at gmail.com> wrote:
>
>> Peter,
>>
>> I think your point is an interesting one.
>>
>> The NewScientist blurb says T1R2 was lost from birds (but retained in
>> lizards).
>>
>> Now, hummers were just found to use T1R1 for tasting sweet (instead of
>>  tasting 'savory' with it, like other vertebrates).
>>
>> Liberies is quoted as saying "The re-evolution of sugar receptors may
>> have happened multiple times". So, I'd expect that the authors of the
>> Science paper would agree with you and will very likely search other (sugar
>> eating) bird species for a functional T1Rs (especially T1R1s since part of
>> their cool find is that it has been co-opted for a new function: sweet
>> detection not savory detection).
>>
>> The loss and regain (or shift in use) of sensory receptor function is
>> cool and occurs in vomeronasal and visual receptors, too. For example, deep
>> sea coelacanths have functional 'visual receptors' (opsins) that have
>> evolved to only a tiny range of light that is visible in deep sea water.
>> They have lost some receptors entirely, like the T1R2 was lost from birds.
>> Shallow-water, sexually selecting guppies however, have a large number of
>> visual color receptors, explaining how the females see all those dramatic
>> tail colors.
>>
>> Similarly, butterflies have more opsins than bees do, but that might not
>> be news to this list........
>>
>> Lisa
>>
>>
>>
>>
>>
>> On Fri, Aug 22, 2014 at 11:43 AM, Peter Bernhardt bernhap2 at slu.edu
>> [beemonitoring] <beemonitoring-noreply at yahoogroups.com> wrote:
>>
>>>
>>>
>>> The following link will take you to a popular article on the evolution
>>> and genetics of taste buds on a hummingbird's tongue.  The article insists
>>> that most birds have lost the ability to taste the sweetness in foods.  I'm
>>> not so sure I agree.  What about all those fruit eating species in so many
>>> families as well as nectar drinking birds in the Meliphagidae,
>>> Nectarinidae, Zosteropidae etc.?
>>>
>>>
>>> http://www.newscientist.com/article/dn26089-hummingbirds-turned-savoury-into-sweet-to-taste-nectar.html#.U_diqFb5gTs
>>>
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>>
>>
>>
>> --
>> Lisa Horth, PhD
>> Haupt Fellow
>> Smithsonian Gardens
>> Washington DC
>> (202) 633-5849
>>          &
>> Associate Professor
>> Dept of Biological Science
>> Old Dominion University
>> Norfolk, VA 23529
>> lhorth at odu.edu
>>
>
>


-- 
Lisa Horth, PhD
Haupt Fellow
Smithsonian Gardens
Washington DC
(202) 633-5849
         &
Associate Professor
Dept of Biological Science
Old Dominion University
Norfolk, VA 23529
lhorth at odu.edu
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