A female Nephila pilipes daintily dines on a dead bat (Rhinolophus cornutus orii) caught in its web in Japan.
|
Spiders are a fascinating and remarkably successful group of arthropods,
with 41,000+ living species and 500 or so new species being discovered and
described each year. They are also a
very old lineage, the earliest definite spider fossils date to some 300,000,000
years and indicate that the history of
the group extends back even further than that. Spiders come in a wide range of
sizes and shapes and exhibit a remarkable diversity of ecology and lifestyles.
A small rhinolophoidean bat entangled in the web of Nephila pilipes in Australia. |
All spiders
are predators and while they most feed on invertebrates, especially other
arthropods, occasionally larger prey is taken.
A recent paper by Martin Nyffeler and Mirjam Knornschild documents the little
known fact that spiders sometimes also fed on bats. In most cases these are large spiders that
produce large orb-webs that snare small, insectivorous bats that are actually smaller
than the spider. While none of these spiders specializes in capturing and
feeding exclusively on bats, this fascinating behavior has been observed on all
continents (with the exception of Antarctica)
and is not insignificant.
Map showing reported incidents (red dots) of bat predation by spiders. |
Nor is it just bats that are caught in webs. There are a
number of published records of small birds taken by spiders as well, although
that appears to be much rarer than incidents with bats.
A Nephila feeds on a finch in Australia. |
In most cases the bat/bird predator is a large spider of the
genus Nephila, the largest orb
weaving spiders. Nephila is known as
a golden orb weaver, a reference to the color of its spider silk. Its poison is a neurotoxin similar to that of
the famous Black Widow Spider. While not
lethal to humans, the amount of toxin injected by Nephila when biting a bat smaller than itself is relatively huge
--- and fatal.
Nephila jurassica, the largest fossil spider. Actual specimen on left, explanatory drawing on right. |
Because their exoskeleton is only weakly mineralized,
spiders have a relatively poor fossil record.
However, it turns out that the largest known fossil spider is also
referable to Nephila. Nephila jurassica is known from a single
specimen, a female, and comes from rocks of Middle Jurassic age of China, some
165,000,000 years-old. The fossil is reasonably
complete and the preservation is spectacular, with even fine details of sensory
“hairs” clearly visible.
The remarkable preservation of N. jurassica is evidenced by these fine sensory hairs on the opisthosoma. |
Insect fossils are very diverse and common in the rocks in
which N. jurassica was found and
certainly were the primary food source for the species. However, given the work
of Nyffeler and Knornschild on modern spiders and bats, one might naturally wonder
if birds and/or bats might have also fallen prey to N. jurassica.
The oldest definite fossil bats, known from well preserved
skeletons, date from the Eocene Period about 100,000,000 years younger than N. jurassica. The oldest known bird, Archaeopteryx, is from the Late Jurassic of Europe, about 15
million years younger than N. jurassica. Furthermore,
Archaeopteryx is the size of a raven
or crow and much too large to be caught in a spider web. However, there is another group of Mesozoic
flying vertebrates that might have provided a feast, at least occasionally, for
Nephila.
The small pterosaur Anurognathus ammoni pursues an insect in a Late Jurassic forest in Europe. |
Pterosaurs first took to the skies in the Late Triassic and continued
soaring and flapping until the end of the Cretaceous. During those 160,000,000
years they evolved into many different sizes and shapes, and flew in everything
from forests to soaring great distances over open oceans. While some pterosaurs
were gigantic, others were quite small. Anurognathus had a body length of just 4
inches and a weight of only 1.5 ounces.
This is small enough be caught in a large web, such as that made by N. jurassica.
The complete, but very small and delicate, skeleton of Anurognathus ammoni is more easily seen under UV light. |
Pterosaur predation by spiders is just an inference. Paleontologists have not found any fossils of
pterosaur remains preserved in a spider web and the chances of such a find are
small, although not impossible. However,
given what we known about the predatory behavior of large orb weavers and the
very small size of some groups of pterosaurs it seems very likely that
pterosaurs provide occasional sustenance to Nephilia
and its kin. I’m waiting for one of the
many talented paleoartists to do an appropriately tasteful painting of N. jurassica straddling across and
feeding on an anuroganthid that is all wrapped up in spider silk. And above the
image, it reads:
Nephila.
Proudly killing and eating flying vertebrates for 165,000,000 years.
It would be a beautiful thing.
Thanks to Tracy Ford for calling my attention to N. jurassica.
*************************************
SOURCES
Kuntner, M. and Coddington, J.A. 2009. Discovery of the
largest orb weaving spider species: The evolution of gigantism in Nephila. PLoS ONE 4(10): e7516. doi:10.1371/journal.pone.0007516
( http://www.plosone.org/article/info:doi/10.1371/journal.pone.0007516)
Nyffeler, M. and Knornschild,
M. 2013. Bat Predation by Spiders. PLoS ONE 8(3):
e58120. doi:10.1371/journal.pone.0058120 (http://www.plosone.org/article/info:doi/10.1371/journal.pone.0058120)
Penny, D. and Selden, P.A. 2005. Assembling the Tree of
Life—Phylogeny of Spiders: a review
of the strictly fossil spider families. European
Arachnology (Deltshev, C. and Stoev, P.,
eds). Acta zoologica bulgarica,
Suppl. No. 1: pp. 25-39.
Selden, P.A., Shih, C.K.,
and Ren, D. 2011. A golden orb-weaver spider (Araneae: Nephilidae:
Nephila) from the Middle Jurassic of China. Biology
Letters 7: 775–778. (http://rsbl.royalsocietypublishing.org/content/7/5/775)
Witton, M.P. 2008. A new approach to determining pterosaur
body mass and its implications for pterosaur flight. Zitteliania B28: 143-159.
PHOTOS
Nephila pilipes with bats in Japan and Australia and map of incidents: Nyffeler and Knornschild 2013.
Nephila with finch: http://entophile.com/page/5/
Nephila jurassica photos: Selden, Shih, and Ren 2011
Anurognathus ammoni flesh restoration: http://commons.wikimedia.org/wiki/File:AnurognathusDB.jpg
Anurognathus ammoni skeleton: http://pterosaur.net/fossils_uv_anurognathus.php
Haloo pak^^
ReplyDeleteKami dari SENTANAPOKER ingin menawarkan pak^^
Untuk saat ini kami menerima Deposit Melalui Pulsa ya pak.
*untuk minimal deposit 10ribu
*untuk minimal Withdraw 25ribu
*untuk deposit pulsa kami menerima provider
-XL
-Telkomsel
untuk bonus yang kami miliki kami memiliki
*bonus cashback 0,5%
*bunus refferal 20%
*bonus gebiar bulanan (N-max,samsung Note 10+,Iphone xr 64G,camera go pro 7hero,Apple airpods 2 ,dan freechips)
Daftar Langsung Di:
SENTANAPOKER
Kontak Kami;
WA : +855 9647 76509
Line : SentanaPoker
Wechat : SentanaPokerLivechat Sentanapoker
Proses deposit dan withdraw tercepat bisa anda rasakan jika bermain di Sentanapoker. So… ? tunggu apa lagi ? Mari bergabung dengan kami. Pelayanan CS yang ramah dan Proffesional dan pastinya sangat aman juga bisa anda dapatkan di Sentanapoker.