[OGD] cricket pollinating (La Reunion)

  • From: viateur.boutot@xxxxxxxxxxxx
  • To: orchids@xxxxxxxxxxxxx
  • Date: Tue, 12 Jan 2010 14:33:15 -0500

"Instead of gorging on flowers, the raspy cricket pollinates them
... its... behaviour has surprised scientists.
...
this species... acting as a pollinator.

... this is the first time a cricket has been spotted pollinating a flower...

A study of the nocturnal insect, which was found on the island of Reunion, 
has been published in the Annals of Botany.
... has yet to be given a scientific name, but it belongs to the Glomeremus 
genus of crickets, which are also known as raspy crickets.
...
The insect was spotted by researchers who were attempting to find out how a 
species of orchid called Angraecum cadetii was being pollinated.

This green-white flower is closely related to the comet orchid, which is 
found in Madagascar.

Naturalist Charles Darwin predicted that because the comet orchid has an 
incredibly long nectar spur (the part of the plant that holds the sweet 
nectar), it would be pollinated by an insect with an equally long tongue.

It was later found that the nocturnal hawk moth with a proboscis measuring 
approximately 35cm (14in) in length was the pollinator.

However on Reunion... hawk moths are very rare and the Angraecum cadetii 
orchid has a shorter nectar spur than its Madagascan relative, so 
scientists suspected something else was pollinating it.

... scientists trained a night-vision camera on the flower.
...
Claire Micheneau, from the University of Reunion, who carried out the 
research with the UK's Royal Botanical Gardens (RBG), Kew, and the 
University of Strasbourg, France, told BBC News: "We were very surprised 
when we saw a cricket.
"Crickets usually eat flowers, not pollinate them."

The film shows a wingless cricket, which measures about 2-3cm (0.8-1.2in) 
in length and has extremely long antennae.

It crawls onto the flower and pokes its head in to the nectar spur to drink 
up the sweet liquid before leaving with lumps of pollen attached to its 
head and visiting other flowers on the orchid.

... Micheneau said: "This is the first time that we have seen flowers being 
regularly pollinated by a cricket."

The team added that the cricket seemed to be the only pollinator present on 
the flower and that it was extremely effective at doing the job, possibly 
thanks to the fact that the size of its head matched the size of the nectar 
opening on the orchid.
...
Further analysis of the cricket revealed that the species was new to science.
        
Professor Mark Chase, director of the Jodrell Laboratory at RBG Kew, said: 
"It really is a completely bizarre thing for a cricket to do and it is 
strange for an orchid to become adapted to that kind of pollinator."

... the cricket was also unusual in other ways.
Professor Chase explained: "They do some fairly sophisticated things by 
cricket standards.
"Most crickets just stop eating and find a place to hide away during the 
daytime and it's usually a different place every time.
But this one finds its way back to its own specific nest.

"And that is a key thing for being able to re-locate the orchids, because 
they go back to those several times, and it is that capacity to keep track 
of where they are in their environment that allows them to do this sort of 
navigation."

The research team is now looking at how the relationship may have come about.

... Chase said: "Orchids rarely co-evolve with their pollinators, mostly it 
is a case of the orchid adapting to an insect or animal that already exists 
that may visit flowers of other plants, and the orchids sort of tap into 
that."   "

URL : http://news.bbc.co.uk/2/hi/science/nature/8391540.stm

_____________________

"In 2008 Claire Micheneau, a RBG Kew-associated PhD student studying how 
the epiphytic orchid genus Angraecum has adapted to different pollinators 
on Reunion Island, and Jacques Fournel, her collaborator, shot the... footage.
It shows a raspy cricket (Glomeremus sp) carrying pollen on its head as it 
retreats from the greenish-white flowers of Angraecum cadetii.
...
Says Claire Micheneau, "We knew from monitoring pollen content in the 
flowers that pollination was taking place.
However, we did not observe it during the day.
That's why we rigged up a night camera and caught this raspy cricket in 
action.
...
a... surprising shift in the pollination of Angraecum, a genus that is 
mainly specialised for moth pollination...

"The moths that are the main Angraecum pollinators on Madagascar are not 
found on Reunion and until we started our research the pollination of this 
genus on Reunion had always been an open question."

Micheneau's research also revealed that two other species of Reunion Island 
Angraecum orchids (A. bracteosum and A. striatum) are pollinated by two 
species of small white eye songbirds (Zosterops borbonicus and Zosterops 
olivaceus).

She continues, "My studies have shown that the raspy cricket is also a 
surprisingly efficient pollinator with higher rates of pollination and 
fruit set in Angraecum cadetii than those recorded in its bird-pollinated 
sister-species." (1)

There is a close match in size between the raspy cricket's head and 
Angraecum cadetii's nectar-spur opening (2).
These wingless raspy crickets reach the flowers by climbing up the leaves 
of the orchid or jumping across from neighbouring plants.
They use long very long antenna to explore their surroundings.

Just why the raspy cricket developed a taste for orchid nectar is still a 
key question for Micheneau.
"Although crickets are typically omnivorous and eat both plant material and 
other insects, we think the raspy cricket has evolved to eat nectar to 
compensate for the general scarcity of other insects on Reunion."
...
Film footage of the cricket can be downloaded here 
http://www.kew.org/press/downloads/cricket_footage/
...
Images are available to download from www.kew.org/press/images ...
A PDF of
Orthoptera, a new insect order recorded as orchid pollinator...
is available from the Royal Botanic Gardens, Kew press office 
www.aob.oxfordjournals.org
...
(1) Fruit set was 10% for the bird-pollinated species, and around 20% for 
Angraecum cadetii

(2) A nectar spur is a hollow tube extending from the petals of a flower 
that holds nectar in its base
...
Kew Gardens...
Its landscaped, 132 hectares and RBG Kew's country estate, Wakehurst Place, 
attract nearly 2 million visitors every year.
Kew was made a UNESCO World Heritage Site in July 2003 and celebrates[d] 
its 250th anniversary in 2009."

URL :

http://www.eurekalert.org/pub_releases/2010-01/rbgk-fki011110.php
_______________

see also :

http://tempsreel.nouvelobs.com/actualites/sciences/20100112.OBS3380/la_fructueuse_rencontre_dune_orchidee_et_dun_criquet.html

and

http://www.elmundo.es/elmundo/2010/01/12/ciencia/1263291649.html

*****************
Regards,

VB


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