Ecology of 30,000,000 Year Old Spiders

Science Daily has an interesting article on spiders trapped in amber. This is a subject I have blogged about previously here. According to the article 671 species of spiders, dating to approximately 30 million years ago, from the Baltic and the Carribean were compared. Here is a picture of one:

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New Species of Assassin Spiders Discovered

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According to the California Academy of Sciences nine new species of assassin spiders (such as the one pictured above) have been discovered in Madagascar:

These tiny arachnids in the Archaeidae family are only about 2 mm (less than 1/8 inch) long, but their bizarre fangs and spider-hunting practices have earned them a reputation as the world’s most grotesque spiders. They hunt by stabbing their prey with venom-filled fangs that are attached to the ends of extremely elongated jaws. These specialized jaws are about ten times longer than the jaws of most other spiders their size. To support these long jaws and prevent them from dragging along the ground, Assassin spiders have also evolved elongated necks.

*snip*

Surprisingly, the DNA data also revealed that the presence of elongated necks among Archaeidae spiders had evolved at least two separate times. A classic example of convergent evolution, her findings suggest that the need to strike out at prey from a distance encouraged the evolution of extended body parts on more than one occasion.

Blood Drinking Spiders!

The above is a jumping spider native to Africa:

Evarcha culicivora, is found only around Lake Victoria in Kenya and Uganda. A species of jumping spider, or salticid, it usually hunts insects on tree trunks and buildings. It stalks its prey rather than trapping it in a web.

At the moment it is pretty unique. You see it has a taste for mammal – and human – blood! How do we know this? Scientists recently conducted prey preference experiments. This is how it works:

Lab experiments conducted near Lake Victoria showed the spider preferred female mosquitoes fed with human blood over all other prey, including male mosquitoes, which don’t feed on animal blood.

Tests of the spider’s prey preferences showed it went for blood-engorged female mosquitoes in 83 percent of cases when offered a choice of two similar-size insects.

When it came to making a choice based on smell alone, with the two meal options hidden from view, around 90 percent of jumping spiders selected the blood-filled mosquito.

Although many spiders have relatively poor eyesight—those that use webs to trap prey have no need for acute vision, Nelson says—jumping spiders are an exception.

“Salticids are predators that actively search for prey and mates and typically do not build webs,” she said. “They have evolved eyes that support high-acuity vision suited to their active lifestyle.”

Spiders don’t have the skin-piercing mouth parts needed to feed directly on human blood, but the mosquito-munching jumping spider appears to have got around this. The strategy has other advantages as well, Nelson points out.

“Blood-feeding is a dangerous activity,” she said. “Animals that are bitten have a swatting response, and often the insect is killed.”

So, essentially the spider has come up with a method to avoid being swatted and still specialize on blood.

The study team suspects a blood meal is also biologically important to E. culicivora.

They say spiders expend a lot of energy breaking solid food down into liquid by injecting their prey with digestive enzymes.

“Perhaps blood is a ready-made, nutrient-rich liquid meal,” Nelson said.

Although spiders creep me out, I think this is a fascinating study in evolution. Mosquitos specialize on blood as a food source as does E. culicivora but both have evolved different methods to obtain it. It would be interesting to find out if mosquitos were E. culicivora’s primary prey or if this is a recent addition to their diet. It would also be interesting to see if there is a closely related species that doesn’t feed on mosquitos (I’m thinking of Rhagoletis pomonella).

20,000,000 Million Year Old Spider

The above is a picture of a 20,000,000 year old spider trapped in amber. Sciectists recently created an interesting method for studying the creature – shades of Jurassic Park.

According to BBC News:

Palaeontologist Dr David Penney, of the University of Manchester, found the 4cm long by 2cm wide fossil during a visit to a museum in the Dominican Republic.

Since the discovery two years ago, he has used droplets of blood in the amber to reveal the age of the specimen.

It is thought to be the first time spider blood has been found in amber and scientists hope to extract its DNA.

Even more interesting:

Dr Penney believes it was climbing up a tree 20 million years ago when it was hit on the head by fast flowing resin, became engulfed in the resin and died.

He claims the shape and position of the blood droplets revealed which direction the spider was travelling in and which of its legs broke first.

You can see more images of spiders trapped in amber atMesozoic Arachnids along with other interesting info about Mesozoic spiders.

Eocene Insect and Plant Diversity in South America

Since I have an anthropology background I really don’t post that much on plants and insects (What, no bones? Inconceivable!) But I found this really fascinating.
Researchers collected over 3,500 fossils from from 25 quarries in Patagonia. Each fossil was examined for four types of insect damage:

The four feeding groups are those insects that feed on the external leaf, chewing holes, edges and other leaf parts; those insects that mine tissues inside the leaf; those that produce bulbous galls and those that pierce and suck the leaves. Because different insects chew, mine, gall and pierce in different ways, the researchers recognized 52 discrete damage types from the four feeding groups. They applied these categories to both bulk samples from single quarries and to individual leaf species.

Below is an example.

Insect Damage Posted by Hello

They were then compared to approximately 2700 fossils from three sites in North America. The results:

The researchers found that the number of damage types at each of the four major Patagonian quarries significantly exceeds each of the three North American samples. The number of functional feeding groups is also greater than all North American samples for three of the four major quarries. The diversity of damage types and feeding groups at the Patagonian sites for individual plant species hosts is also highest.

“Insect damage on leaves, the remains of insect meals, is uniquely valuable data,” says Wilf. “While actual insect fossils can give us taxonomic information, leaf damage provides unique ecological data about which and how many kinds of insects were eating and interacting with ancient plant species in the deep past. Also, insect damage on fossil plants, which can be very abundant, can give us a great deal of information about insects at times and places with very few insect fossils.”

The research design was extremely rigorous. The North American fossils were collected by the same team and members of that team helped collect the Patagonian fossils (to insure identical collection methods). Two of the researchers scored all the insect damage (to insure consistency in the scoring). Samples were then adjusted for size. All in all an impressive piece of research. Incidentally, if a creationist ever tells you we can’t learn about the past because humans weren’t around to witness it you can point them to this post – which shows, in a very convincing fashion, that we can.

Also, the same team published an earlier study which gives a few more details. You can find a summary of that earlier work here.

Here is a few paragraphs to tide you over till you get there:

Many Eocene fossil sites in North America have been collected 100 years or more. Laguna del Hunco, though known for 80 years, is now the first of this age from South America to be heavily and quantitatively sampled. Quantitative sampling, where every specimen is tallied and identified, allows sample size to be taken into account when comparing recovered diversity. The age of the deposit was also not well constrained.

The researchers collected more than 1,500 fossils and identified more than 100 different fossil leaf species including dicots, monocots, conifers, ginkgophytes, cycads and ferns. They also identified a variety of seeds, fruit and flowers. In total, they more than tripled the known diversity of the site in two weeks. Using paleomagnetic dating, which uses the Earth’s magnetic pole reversals, and argon argon dating, which compares the amounts of two isotopes of argon one of which is produced by the natural radioactive decay of potassium, the researchers dated the fossils to a half million year interval between 52 and 53 million years ago. These are the first high-precision ages for the deposit, which now can be correlated anywhere in the world.

I will be republishing this, in a slighttly different form, over at Transitions this evening.

Black Widow Update

About a month ago I did a post on the Brown Recluse and the Black Widow. I have discovered an interesting article on widow spiders so I am publishing a link to it for those who are interested.

It is in Science in Africa a great online magazine.

The Button Spiders of Southern Africa .

Icons of Creationism: The Bombardier Beetle

I had originally intended to do this post yesterday in time for the Friday Ark, but got sidtracked. Normally I like to research what I post about for the Friday Ark and this time is no exception. Which is part of the reason why I didn’t get it written. My original intention was to post a couple of picts, find a few links to interesting info about the beetle and discuss how it could evolve. One of the great things about trying to provide interesting scientific information about whatever I post for the Friday Ark is that sometimes I stumble across some really fascinating stuff. This time I struck the mother load. I think, to be more than a little snarky, George Bush should have looked to the insect world for weapons of mass destruction! To be an insect is to be immersed into a nightmare world of chemical warfare.

Chrysomeline (Leaf) beetles, for example, have chemical defense glands. Originally, they synthesized the chemicals themselves. During the course of their evolution, however, the became dependent on plant hosts to acquire the chemicals they use for defense (in other words, they incorporate the host plants toxins into their own defense system). One group within the Chrysomelines (the interuptus group)however, has managed to adapt to a wide variety of plant hosts and uses a wide variety of chemical defenses. One of the more interesting things about this is that in order to go from self synthesized to use of host derived chemicals only requires the change of one or two enzymes. To go from the use of host derived metabolites to use of many hosts also requires the change of one or two enzymes.

Fireflies illustrate another, creepy, way insects can acquire chemical defenses. Female fireflies of the genus Photuris imitate females of the genus Photinus. Once they attract a male of the genus Photinus they eat him! Photinus species have a chemical called lucibufagin (similar to a chemical found in the chinese toad) which are extremely noxius to the insects that prey on fireflies (mainly jumping spiders). So female Photuris acquire the chemical by ingesting male Photinus. Then when attacked they engage in what is called reflexive bleeding and the chemical in their blood drives the predator away. They also incorporate the chemical into eggs when they lay them so their offspring is protected.

Peruvian fire sticks (related to the walking sticks) also use chemical defenses. They are rather unique in that a lot of species, when molting, shed their defensive glands. Fire sticks shed the cuticle lining, but do not shed the gland itself. Consequently, they do not have to wait as long after molting to use their chemical defense. The glands are located near their neck. The chenical is sometimes ejected as a spray but more often is oozed out as a froth and spreads down the thorax. The chemical is related to quinoline and other species of walking stick do not have this type of chemical. In that sense Peruvian firesticks are unique.

Opilionid beetles are similar to the Peruvian fire sticks in the way the use their chemical defenses, but not identical. A bubble of enteric fluid is dribbled out their mouth and onto a track which runs by their glands, where quinonoid paste is injected into the enteric fluid. This bubble then moves down a groove on the beetles carapace. The beetles use it back legs to scoop some of this mixture of and tries to smear it on it’s attacker.

Which brings us to the Bombardier beetle. Bombardier beetles compose two branches in family Carabidae (brachinoid and paussoid). The Paussoid branch is believed to be older and more primitive (in evolutionary terms). One of these (Metrius contractus) is believed to be close to the ancestral condition for Bombardier beetles. It has two gland openings near the abdominal tip. The glands themselves are cuticle lined and have two chambers (as in all Bombardier beetles). When attacked the froth is emitted and either runs down a track (if attacked in the front)or builds up near the glands (if attacked from the rear). M. contractus is unusual in that the froth develops into a mist, whereas in brachinoid species it is sprayed in any direction. M. contractus is also unique in that the froth is only 50 degrees centigrade rather than one hundred degrees centigrade as in brachinoid species.

Which brings us to the Bombardier species proper. The species pictured below is Stenaptinus insignis.

A single bombardier beetle can discharge upward of 20 times
before depleting its glands (6). The discharges are accompa-nied
by audible detonations, and they have been shown to be
potently deterrent to a number of predators, including ants (6,
12–15).
The spray of bombardier beetles is ejected at 100°C (13).
This is because the quinones are generated explosively at the
moment of ejection by the mixture of two sets of chemicals
ordinarily stored separately in the glands. Each gland consists
of two confluent compartments. The larger of these (storage
chamber or reservoir) contains hydroquinones and hydrogen
peroxide while the smaller one (reaction chamber) contains
special enzymes (catalases and peroxidases). To activate the
spray, the beetle mixes the contents of the two compartments,
causing oxygen to be liberated from hydrogen peroxide and the
hydroquinones to be oxidized by the freed oxygen. The oxygen
also acts as the propellant, causing the mixture to ‘‘pop’’ out
(16–18). The heat that accompanies the formation of the spray
is perceptible (13) and contributes to the defensive effective-ness
of the secretion (14, 15). An early explorer, reporting on
large bombardier beetles from the neotropics, commented that
when these ‘‘play off their artillery’’ they are so hot to the touch
‘‘that only few (can) be captured with the naked hand’’ (19).
Although it was known that bombardier beetles can aim their
spray by revolving the abdominal tip (6), the degree of
precision with which they target their ejections had escaped
notice. (from THOMAS EISNER AND DANIEL J. ANESHANSLEY, (1999) Spray aiming in the bombardier beetle: Photographic evidence. Proc. Natl. Acad. Sci. USA
Vol. 96, pp. 9705–9709, August 1999)

Bombardier 1 Posted by Hello

This first picture shows a bettle directing the spray to the front. Note the glob of stuff on it’s back. They attached a wire to the beetle by embedding it in wax. They then used the wire to handle the beetle.

Posted by Hello

This second picture shows a beetle directing the spray backwards.
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The third shows the beetle directing the spray to the right rear – note the forceps, they had to pinch it’s leg to set it off.

In addition to the insects mentioned above, a wide variety of other insect use some form of chemical defense including: millipedes, cockroaches, ants, termites earwigs and grasshoppers to name a few (but I’m still in shock about the male-eating fireflies. I am used to that kind of thing in, say, black widow spiders, but not in lightening bugs!).

So, we have a wide variety of different chemicals, a large number of different ways of getting the chemicals and delivering them (we could have given details on Opilionid beetles and millipedes as well). In some cases, the differences are caused by differences in a few enzymes. I have done much research into the origins and evolution of these systems, but from what I have read so far Bombardier beetles don’t represent that much of a challenge to evolutionary theory. Rather, they seem to be a specialization of several traits already present in nature in one form or another – benzoquinones, for example, are used by a wide variety of insects.
I will probably write some more about this in the future. I just need to do some more research into a really fascinating area of biology (it’s referred to as chemical ecology in the literature I’ve read).