Without further ado, here is 'That's What Slugs are For', now with more slugs!
Sunday, December 30, 2007
Without further ado, here is 'That's What Slugs are For', now with more slugs!
Friday, December 28, 2007
These guys used to be the ‘bees knees’ as it were. There was once over 4500 different genera existing in all parts of the ocean. Now there are only 350 different species of brachiopods, and they are only found between 100 to 200 meters (330-600 feet) down.
So what happened? Why do we now have clams and such instead of brachiopods? Well there are several hypotheses, but I will share the one that makes the most sense to me. Brachiopods were well established when the clams came along, and were not giving up the prime spots to any newbie filterer. However, the decline of brachiopods coincided with the rise of shell crushing sharks. The clams, which could bury themselves, had a refuge from predation that the brachiopods could not utilize. So, brachiopods got crunched, and the clams and such took over the filtering the ocean gig.
Brachiopods are so abundant as fossils that they are often used to date rocks. (Like, finding a certain species will tell you that the rock is between x and z years old) They can also be bought at any curio or museum shop, as an example of a real fossil along with the ever-present trilobite.
Thursday, December 27, 2007
I've been trying to find out more about it but the new stories have been remarkably flash-in-the-pan. There was a big glut of stories till it turned out that the men may have been terrorizing the tiger and may have helped it escape by dangling their legs over the edge. Apparently, she jumped up a 12.5 foot wall (although some reports say 18). I don't know for sure how deep it was, but it looked much taller than two man-heights the last time I was there.
What is disturbing to me is 2 things. First the news reports were so full of misinformation, that I don't believe anything they say. This was the same tiger that scratched up her zookeeper in 2006, when the zookeeper stuck her arm in the cage during a feeding demonstration. Some news reports said she (tiger) ripped or chewed the zookeeper's arm off. Other reports said that the three guys who were attacked did not know each other and made it seem like the tiger was just wandering around mauling people. There were only 20 in the whole zoo at the time of the attack, there were no other witnesses around the cat enclosure. The two other men involved in the incident have not given statments to the police yet.
The second is the reaction against it. Yes, there are many people who think that teasing tigers is not a good idea. Yet the other half protest that the zoos are still responsible, no matter what the boys did. The SF zoo is putting up security cameras (which I think is a great thing, then they can fine people teasing the animals!), and are talking about electrified fences. Basically, to keep people from their own stupidity. But most outdoor cat enclosures in zoos are built the same way.
These people also cry shame on the other half, who believe that if the kids teased the tiger, then they are to blame. How can you be so insensitive, they cry. How can you value the tiger's life over the boy's?
She was part of a breeding program. There are less than 500 Siberian tigers left in the wild.
Wednesday, December 26, 2007
They found that there was no difference in egg size due to colony morphology or size, but smaller colonies were less likely to spawn a second or third time. They did find that chlorophyll concentration of the eggs increased with increasing size of the colony. This may have been due to the fact that larger colonies were deeper down, so packaged their eggs with more zooxanthellae than the smaller, shallow water colonies.
They also found that eggs sizes within the bundles varied, which interests me because I work on maternal provisioning in a colonial animal too. I find that larvae released by my bryozoans can have up to a 2-fold difference. I am most curious to know how much those eggs varied, since most researchers ignore within brood variability. They also found that the egg sizes varied among spawning events. Generally there was a decrease in the size of the eggs on subsequent spawning events, but a slight increase in the number.
This raises some interesting questions. It would be interesting to find out if the same amount of energy is expended for each of the broods (that is does the increase in number balance the fact that smaller eggs are made). Are these smaller eggs as fit as larger eggs? Are parent colonies more willing to take a chance by producing smaller eggs, since they are assured some reproductive success with the earlier large egg brood?
Finally, if would be fun to know if this down shift in egg size (energy into eggs) is accompanied by an up shift in sperm production. Since the eggs and sperm are packaged in the same bundle, it may be relatively interesting to quantify the egg/sperm ratio. It would also be interesting to see if that ratio is different among the different sizes of colonies. It's generally easier (energetically) to be a male, so would smaller colonies increase their reproductive success by packaging extra sperm?
Monday, December 24, 2007
The week before, one of the directors of the aquarium was visiting the tidepools when he noticed these really cool fossil whale remains.
This is a shot of the rostrum. The two center lines that are close together are the upper jaw, while the bottom line is one half of the lower jaw.
Here's the neat part. This may be a cast of the inside of the brain case. The knob on the back end may be the foramen magnum.
Finally, a close shot of the fossilized bone. You can see the two layers of bone, the lighter compact bone (or cortical bone) and the darker, more porous spongy bone (or cancellous bone).
What a cool tidepool find!
Saturday, December 8, 2007
Tuesday, December 4, 2007
The joining of the optic nerve bundle to the retina itself in vertebrates causes a blind spot (no photoreceptor are located here). On the other hand, cephalopod optic nerves are attached at different points along the back of the eye (not the inner layer), eliminating the need for a 'bald spot' on the retina.
The photoreceptor in cephalopod eyes actually face towards the light! Vertebrate photoreceptor face away from the light and light must pass through other layer before hitting the photoreceptor.
Another interesting design plus is that squids very rarely get cataracts in the center of their eyes. What they found was that squids, and some other cephalopods (like octopods) have two types of genes responsible for making the proteins for the lenses in their eyes. These genes have an extra insertion, either short or long insertions, (which are basically like extra instructions) that are not found in our eyes. When these extra insertions are translated into the proteins, they give extra stability to the protein so they won’t unfold. Since cataracts are caused by the proteins unfolding (making an opaque part in the lens), squids are less likely to get cataracts.
Now, the long gene produces a more stable form of protein than the short gene. The ‘long gene’ proteins are found in the center of the squid eye, while the ‘short gene’ proteins are found in the edges. This means that the center of the eye is least likely to get a cataract. You may wonder why the squid does not just use all ‘long gene’ proteins. I don’t know, but there may be some energy costs associated with making the larger more stable protein, so that it is more cost effective to use the ‘short gene’ proteins on the edges where they don’t count (hypothesis).
Either way, they are better lenses than what we have.
Another cool thing is, that each group of ‘advanced’ cephalopods has their own special version of the two genes, but they work very similarly. This stuff was very well put together; I can’t wait to read the paper on this. It will probably end up in Science, if it has not been published already!
Here’s the original abstract…
SWEENEY, A*; JOHNSEN, S.
Evolution of High-Acuity Vision in Coleoid Cephalopods
Spherical lenses with a graded refractive index design are required for camera-like vision in aquatic animals. In cephalopods, these lenses are made of a group of closely related proteins collectively called S-crystallins. Our earlier work has shown that an adaptive radiation these S-crystallin genes and positive selection on the electrostatic properties of S-crystallin proteins led to a graded refractive index lens capable of forming high-resolution images in the squid Loligo opalescens. In the L. opalescens lens, S-crystallins with high charge stabilize the optical properties of regions of low refractive index in peripheral layers, and S-crystallins with lower charge are tightly packed in the high refractive index cortex. The mechanistic link between S-crystallin sequence, biochemistry and refractive index allows us to understand in molecular detail the optical evolution of a camera-like eye in cephalopods. To understand the transition from ancestral cephalopod vision to extant camera-like vision in coleoid cephalopods, we used techniques from molecular evolution, biochemistry, molecular dynamics, optical modeling and image analysis. We sequenced 600 S-crystallin genes from most major coleoid taxa, constructed a gene tree from these sequences and analyzed it for patterns of charge evolution. We also measured the optical quality of these lenses by calculating their modulation transfer functions (MTFs). Our gene tree suggests that high-resolution lenses evolved from a low-resolution ancestor multiple times within the coleoid cephalopods. Consistent with our gene tree data, our MTF data show that there is taxonomic variation in lens quality within coleoid cephalopods. We will discuss the correlations between independent adaptive radiations of S-crystallin molecules, high acuity vision in cephalopods and possible evolutionary scenarios in which these changes in visual acuity may have been occurring during the Jurassic radiation of squid.
Friday, November 30, 2007
Wednesday, November 21, 2007
These are Harlequin bugs, or Harlequin cabbage beetles (Murgantia histrionica). They live by sucking the juices out of cabbages and other cabbage family members. Most of the time they are considered a pest by farmers. They are part of the stinkbug family, although they also play dead when disturbed.
The females lay up to 12 eggs in a double line on the leaves…
After hatching, the young (nymphs) cannot fly. They will go through 5 successive molts before they get the color patterns and the wings of an adult. That takes approximately 42-47 days.They are very dependant on temperature conditions for their growth and development.In northern areas, they only have one clutch per year. In southern areas they can have three clutches. When mating the male and female stand with their abdomens touching, for the transfer of sperm.
These bug pictures were all taken on one Bladderpod bush, a native bush to California. Some harlequin bugs will spend their entire lives on a single bush.
Sunday, November 18, 2007
I want to do a post on some of the cool talks I heard at the meeting I went to last week, and I will soon. I just need to finish the results section of my thesis and get back on track with grading. That is so enjoyable. After all, "the results showed that higher temperatures did not decrease the population growth, instead slowed it down from growing".
However, in all fairness, my writing probably distresses my advisor to a similar degree!
Thursday, November 8, 2007
Tuesday, November 6, 2007
Its name comes from its tendancy to form large groups (hundreds) of crabs which then march down the beach. I’ve heard tell that the larger crabs ‘direct’ the movement (i.e. smaller crabs follow them) earning them the nickname of general crabs, but I have yet to find some verification of this. When disturbed, the crabs corkscrew into the sand on their side.
Saturday, November 3, 2007
Thursday, November 1, 2007
This means that the mothers gave up to 4 times the amount of energy needed to undergo metamorphosis to their young!
Thursday, October 25, 2007
Tuesday, October 23, 2007
I also love the classic line of "I'm going to run some carbon 14 tests on this tissue. There have been some recent discoveries in the field of genetics that might help us understand its structure."
Sunday, October 21, 2007
This is a picture of a crinoid. Crinoids are in the same phylum as sea urchins, cucumbers, and sea stars, the echinoderms (spiny-skin). Basically, if you imagine an upside-down brittle star with lots of arms, you’ve got a crinoid. There are two types, stalked crinoids, which have a stalk giving them the common name of ‘sea lilies’, and stalk-less crinoids, which have claw like cirri that they use to walk with.
Both types are filter feeders, and you often find them in deeper waters where they catch ‘marine snow’ detritus and dead matter that falls from the upper surface. Their tube feet are modified to assist in filter feeding, they lack the suction cups on the end that most other members of the echinoderm phyla posses. Also, they are one of the few members of the echinoderms whose anus is on the same side as their mouth, instead of the opposite side. (The other group that has the same arrangement is the sand dollars)
They first appeared in the oceans around 510 million years ago, around the middle of the Cambrian beginning of the Ordovician periods. They were incredibly abundant from the Silurian to the Carboniferous periods (435-290 mya), such that whole layers of ocean limestone are made up entirely of their fossils.
While modern stalked crinoids only reach a height of 60cm (23 inches), some fossil forms reached 20 meters in height (60 feet)!
Thursday, October 18, 2007
Wednesday, October 17, 2007
So I just got back from a great meeting, and now that my brain is functional again, I wanted to share an interesting talk that I attended. Basically, for those who have never experienced it, when you got to a meeting you get to here a ton of research, most of which is not published yet or in progress. So several days of hearing really smart people doing really cool stuff! (although it can be a mixed bag…) My brain exploded. But now that the knowledge has begun to settle…
The following is a description of some work being done by several people in Australia.
Okay, some background. Most fish have a stage after thy hatch when they float around in the water, before they get big enough to settle out. This would lead to mixing of fish, as they could potentially end up anywhere. However, when they looked at the genetics of some of these fish found on near by reefs, they found that they were very different and not mixing. This means that the baby fish are finding away to keep themselves in the area, or coming back when they are big enough to swim. But how do they know which reef is the one they hatched from?
These researchers looked at larval fish just before they became big enough to settle and tried to see if the babies could ‘tell’ their home by the smell of the water. What they found was that babies found on one reef preferred the water of that reef to any others. They also found that when they kept the babies in the different water for a time to get them to adjust to the new water, they still preferred their ‘home’ water.
Since most of these fish were brooded as eggs on the reef, the researchers were also curious to see when this smell impression was made. Were they impressed while they were in the egg or at hatching? So they took some anemone fish eggs (clown fish), which were known to home not only to reefs, but also back to particular anemones, and ran some tests. Some eggs were kept in anemone water till just before they hatched, and others were only put in anemone water when they were hatching. What they found was that the fish imprinted on the anemone, smelling water immediately after hatching, but not while they were in the eggs.
What it means is that it is possible that some of the fishes on reefs smell the water after hatching, than use the odor to keep themselves from getting too far from their home. So when it comes time for them to settle, they settle on the same area they were born in!
Below is the original abstract with the names and the affiliations of the researchers working on this. I look forward to reading the paper when it gets published.
MILLER-SIMS, V*; ATEMA , J; GERLACH, G; KINGSFORD, MJ
Boston University Marine Program, Marine Biological Laboratories, James Cook University
Olfactory imprinting in coral reef fish
Most marine organisms have a pelagic larval dispersal phase, leading to the question of how far larvae disperse. Larval behavior and odor preferences may play an important role in larval dispersal and settlement. Apogonid larvae prefer the odor of the reef on which they were caught over other reefs and ocean water. It is possible that this response is due to acclimatization to the odor of water the fish have been recently swimming instead of a long-term preference. We tested apogonid larvae settling on One Tree Island by catching them as they came onto the reef and testing their preference for water for One Tree vs. water from Heron Island in a flume preference test. We then held the fish in either One Tree or Heron water and tested them over a period of nine days. The preference for One Tree water declined in both groups over time; there was no significant difference between the animals held in One Tree or Heron water and both groups maintained a preference for One Tree throughout the testing period. Odor preferences remain stable over time despite exposure to other odors and it is possible they are the result of olfactory imprinting to the home reef odor. Olfactory imprinting has been shown in anemonefishes, but the sensitive period is unknown. Breeding pairs of Amphiprion melanopus were held either with or without an anemone. Eggs and larvae were exposed the anemone from egg laying through hatching (1), from egg laying to just prior to hatching (2), just previous to and 1 hour after hatching (3) or had no anemone exposure (4). At 15 days those larvae in groups 2 and 4 had no preference for the anemone while those in groups 1 and 3 showed a strong significant preference for anemone odor. In this species of reef fish larvae must be exposed to the imprinting odor after hatching in order to learn it.