So far, the molluscs we have looked at have had some sort of shell, but not all molluscs have taken the shelled path.

Today, and in the next post, we are going to meet some which prefer to be without shells, and are, in my opinion, some of the most beautiful molluscs around: So, without further ado, let me introduce you to todays topic: the nudibranch (from the Latin nudus meaning naked, and the Greek brankhia meaning gills, so literally, “naked gills”)

Berghia coerulescens, a species of nudibranch. Image from wikipedia

This group of animals has a whole lot of awesomeness going on, some of which we will cover today, and then it will spill over into the next post too!

For today, lets take a look at the one in the video, it is called Glaucus atlanticusm and the reason it is awesome for me, is that, despite being a squishy little sea-slug like thing, around 3cm long, it eats these:

Physalia physalis (Better known as the Portuguese Man O’ War) Image from wikipedia

Now, if there is one thing we know about Portuguese Man O’ War, it is that it has a very nasty sting, due to the trailing tentacles being full of cells which can fire toxic darts into its prey (or into an unsuspecting persons leg) (See link HERE for post about Man O’ War)

So how does Glaucus cope with these stings? There is a hypothesis that it releases mucus while eating the tentacles (Yes, because it is small, and the PMOW is much larger, it nibbles its way up the tentacles), which protects its insides from the stings, which can remain active for a period of time after the Man O’ War is dead.

To make it even cooler, it takes some of these stings, and uses them in its own defense. It goes a little something like this:

Glaucus eats the tentacle with the stinging nematocysts within it.  Some of these pass through digestion, and end up in growths on the outside of the animal, called cerata. These then become part of the animals defense systems, meaning it can fire them at any attackers.

It has primitive teeth (denticles) which it uses to chomp through its prey, but also to hang onto them

So, this is a fairly cool animal so far, but, it gets even more amazing when you find out some other details about it.

This lovely little animal floats upside down, so its top side is in the water, and its underside is at the surface.  It floats because it has a bubble of air in its stomach, but this means it has no way of steering, so it floats around as the winds or currents take it

In common with many fish which are found near the surface (Sharks for example), it uses a form of camouflage which is known as countershading

Its “top” (Which is in the water) is light silvery grey, so it is difficult to spot from below, whilst its “bottom” is a deeper blue, or blue and white, which helps it blend in with the water when seen from above.

I will leave this last image of Glaucus atlanticus for you, and next post we will look at some of the other animals in this family.

Glaucus Atlanticus. Image from EOL (Encylopedia of Life)

This is a BBC one from late last year, about the life cycle of stars.  I started watching it last night, aiming to fall asleep to it, but had to stay awake to the end!

Astronomy is not usually something I post about, as it is not a subject I know much about, but, this one was fascinating!

Enjoy!

Last time, way back in October, I wrote about bivalves (HERE), and wanted to pick up where we left off, so today is about their vision and movement, as promised.

I am going to focus on scallops (Pectinidae) as they have both interesting eyes, and strange movement.

Let’s start out with the eyes.  You and me have two eyes, and this is a fairly common number of eyes to have, Scallops however, seem to be quite fond of eyes, usually having between 40 and 70, but they can have up to 100!

Eyes on a giant scallop, the dark blue dots along the rim of the shell. (Image from Wikipedia)

Now, not all eyes function the same way as ours do, we have already met organisms with eyespots, which are just a bunch of light sensitive cells able to distinguish between light and shade so the organism can move away from predators, or towards the light for photosynthesis. (HERE)

The eyes of scallops are what is known as concave mirror eyes.  These are “simple” eyes, which have a reflective layer at the back of the eye, which bounces light back onto the cells which are able to process the light. As they have so many eyes, positioned along the edge of their shell, they are able to follow an object as it moves past them, rather than having to move their eye to keep it in focus.  They also have two retina in each eye, one which responds to light, and one which responds to darkness.

Scallop Eye, showing the reflecting surface at the back which bounces light to the rods. (Image from rewiring-neuroscience.com)

I have been trying to find other diagrams showing this, and have come up with a couple of sites, depending on how techy of an explanation you want:

Opthobook.com has a very simple diagram (HERE), and a little video explaining the basics of eye variation (HERE).  For the more technical diagrams and explanations, this paper by M.F.Land (1965) is interesting (HERE), as well as this illustrative paper by Colicchia et al (2009)   (HERE). One final paper on comparative morphology (similarities and differences between the parts in different organisms) from Speiser & Johnson (2008) (HERE)

So, apart from having more eyes than that teacher at school who always spotted you chatting (Not that I was ever talking during class, of course!), what else is cool about these bivalves?

Well..I think sometimes a video says way more than I can by rambling, so lets take a look at how these scallops move:

This movement is done by using muscles at the back of the shell to open and close it, this pushes water out of the shell, and the scallop shoots off like one of those bottle rockets you make as a kid with fizzy drinks!  They can control the direction of the jet of water, so it is not a completely random motion.

As I mentioned yesterday, I have been writing my bachelor project, and I thought I would share with you a little of the topic I have written it on.

I could write a post which would keep my good e-friend Argyle Sock very happy, with lots of statistical stuff in it, but, honestly, if I see the terms “not normally distributed” one more time, my head may go pop!

Also, the actual topic is much cooler than the stats (even though they are very cool too of course!).

I would like to introduce to a group of pigments called anthocyanins.  These are the reason for the colour of blueberries, blackberries, some grape species, olives and many other fruits, and purple or red colourings in flowers, like these pansies:

Violet pansies: The purple colour is caused by anthocyanins in the petals. Image from Wikipedia

The amazing bright red colours you see in autumn leaves is also down to anthocyanins.

So..why have I spent this last semester writing about pretty red colours?

Well..here is where it gets a little more interesting (not that pretty purple flowers are not interesting of course!)

Anthocyanins are also found in leaves which are not about to fall off the tree.  Some plants have red leaves when they are young, and some plants can turn on and off the red colouring under certain conditions

Sciencey term for the day: This is called phenotypic plasticity….a phenotype is the appearance something has due to certain genes being expressed. If a phenotype is plastic, it means it can change under certain environmental conditions.

So, I have been looking at a particular plant, which is usually green and grows in shallow lakes.  These lakes dry out a bit in the summer (Yes, we have summer in Denmark, sometimes!), and so some of these plants may end up out of the water.  If this happens, 90% of these plants turn red, until the water covers them again.

The reason I have been looking at this plant (with a bunch of other people who are much better at scary maths than me!) is because it is not entirely clear exactly what the red stuff in the leaves does.  In some plants it seems to act a bit like a sunscreen, in others it seems to stop the plant being eaten by insects.

The amazingly awesome Leaf-cutter ants (Several posts on them will come along a bit later in our evolution journey) will not harvest leaves which are red. This may be because insects do not see red the way we do, they do not have the parts in their eyes which can collect red light.

Leaf Cutter Ants carrying leaves off to their underground farm Image from wikipedia

It has also been suggested that anthocyanins can help plants survive during cold or drought conditions, so, there seems to be a whole lot of stuff that this pigment helps with.

The health food industry has even been getting in on it, and you can buy anthocyanin supplements…this is because in plants, they work as anti-oxidants, and we are always hearing about how having free radicals is bad for us, and so we should eat blueberries, or whatever the cool food to eat this week is (its usually the most expensive one!).  I am not entirely sold on this idea, as, last time I checked, I am not a plant.

So anyway, I have been working with an awesome group of my fellow students, and we have been trying to make these poor plants very stressed to see what happens. We grew them under some very bright lights, and then did some tests where we zapped them with..well…an even brighter light, to see what they did.

Personally, I find the plant we have been studying more interesting than the actual pigment we have been looking at, although, that has been fascinating to learn about.  The plant itself has no stomata, which are the holes which plants use for taking in carbon dioxide and giving out oxygen and look like this in extreme close-up:

Stomata on a tomato leaf Image from wikipedia

Because this plant has no stomata, it has to breathe through its roots, which is extremely cool!  This means that it can only live in lakes which do not have a lot of nutrients in them, because, if you increase the amount of nutrients which end up at the bottom of a lake, you decrease the amount of carbon dioxide which is produced by the bacteria eating all the dead stuff at the bottom.

As more dead stuff ends up at the bottom of the lake, the bacteria down there start using up more oxygen than is available, and so the only ones that can live there produce methane (CH4) instead of carbon dioxide (CO2). This is what is found in my favourite land-types, the wetlands, bogs and moors.

Oh, yes, I forgot to show you a picture of the plant!  This is the little thing I have spent 6 weeks growing, and then several weeks cutting up and zapping with bright lights!

Lobelia Dortmanna. Image from wikimedia

So, I hope I did not bore you too much with the slightly off-topic post, and next time we will pick up on the evolutionary trail again, with some weird and wonderful creatures. If you prefer plants, hang in there, we will get to them in a few million years or so!

Normal service will resume tomorrow with a post about some more intriguing animals, although I probably should write a bit about what I have written my bachelor paper on, seeing as it has kept me away for 6 weeks or thereabouts, so, tomorrows post will be about plants, then back to normal…promise!

Most of these are in the original post I made (HERE), but as they are at the end of a long post, I will put them up on here again, with the new information.

The Forestry Commission has published a visual guide to symptoms: Ash Dieback Disease

The Forestry Commission has also updated its guidance, with information that this is now a quarantine pest, and gives contact details if you think you have come across a site of infection. It also outlines how it is thought that the ancient woodlands have become infected. HERE

I used this Forestry Commission PDF in my original post, it is fairly easy to read and gives an overview: Chalara Fraxinea

The Woodland Trust has updated their guidance since I last read it, with the advice that any suspected infections should be reported at once: HERE

The Government has said that 50,000 trees have already been destroyed: (BBC source HERE)

EDIT for update: There is a website which will be launching Monday at ASHTAG and there will be a smartphone app launching Monday too.  I will post details of that when it arrives.

I mentioned on my fellow blogger Argylesocks post (HERE) that my concern is that with the onset of autumn, we will not know until next year what the extent of the infection is, as the fungus is now in the leaf litter over the winter.

I hope that these are isolated cases in woodlands, but I do not understand why it took from February til late September for this to get attention, or be publicised.

For my non-UK readers, I apologise for the UK-centric posting the last few days.  I am currently writing a post relating to a US issue, so will put that up over the soon.  I will be returning to my evolution based posting next week, but will keep putting up posts of interest to current environmental issues, to go a little more in depth into those.  If you have a story from anywhere relating to environmental or ecological issues which you would like to read a bit more in depth on, you can chuck me an email at squirrellyskeptic at gmail dot com.

At the time I wrote that  ”So far, it seems that the fungus has not managed to infect “wild” trees in the UK, and the government has begun a consultation, which will end on the 26th of October, which could lead to a ban on imports of Ash (and given the severity of the threat, I would hope that a ban is imposed).”

Well, this week it has been announced that the disease has been discovered in  mature forests in the UK, as this Guardian article discusses (HERE).

My last post about this was a bit technical and clunky, so I will try to keep this easier to read.  I want to try to explain as much of the specifics as I can though, because, when I am finding anything out, I like knowing all the details if possible, rather than just understanding the gist of something.

We are going to take a little detour, as I could just tell you that “Mature forests are important” and let you just take that as read, but I would rather run through the reasons behind my claim.

So, firstly, what is a mature forest?

To most of us, a forest is a forest is a forest, but to biologists, and specifically botanists, there is a difference in the type of forest, and it has to do with a term called succession.

Succession can be thought of as the stages of life of an area, whether that is to do with a wetland, a forest, a field etc.

My ecology textbooks define succession as “Replacement of one community by another, often progressing to a stable terminal community called the climax“

To illustrate this I will use the example of how a natural forest progresses, as it is one of the simpler ones to picture, but this also applies to planted forests, although the starting point is different there, as we actually initiate tree growth.

Diagram showing forest succession. Image from the encyclopedia of New Zealand

So, we start out with our bare ground on the left of the diagram, which usually consists of some soil, maybe some grass species (those little guys get everywhere).  This bare ground may be the result of a big event like a glacier retreating, or it could be from the drying up of a lake, or the spread of grasses along a sand dune area.  It can also be derelict land which was previously used as an urban area, things are a little more complex in that case, but the basic order still follows.

If we imagine that we have some rocks on the bare ground, and a few tough grasses to start with.  The rocks provide a nice cosy place for some lichen to start living, whilst the grass roots prevent what little soil or sand there is from blowing away.

The lichen cause damage to the rocks, and small particles of rocks fall off and get trapped on the ground by the grasses, and other particles flying around in the wind also become trapped.  As the lichens and grasses die, or get damaged, they fall to the ground, and begin to form a layer.  Eventually, there is enough of this layer (known as humus) to allow mosses to take hold in the area, and as these die off, they too add to the growing layer of dead stuff on the surface, which allows for bacteria to come in and decompose them, adding nutrients to the new soil.

Over time, the nutrients and soil layer builds up, and small, tough plants can begin to grow there.  These are often other grasses, ferns and very small bushes (Box 2 in the diagram). Microbes, insects, worms etc begin to colonize the young soil.

As the soil quality improves (because the plants there die, and are broken down, and nutrients build up in the soil), and the stability of the soil increases due to the growing number of plants, seeds which are blown in the wind, deposited by animals etc begin to be able to grow, and some of these will be from trees.

Initially, only small, hardy trees can grow, but new species come in and as the conditions continue to improve for plants, taller trees begin to take hold.  These do not grow in the earlier stages as tall trees usually require higher levels of nutrients than bushes, or dwarf trees.

Now we have a young forest, and species of animals and birds begin to colonize the area. Trees begin to grow taller, and form a canopy, this leads to a change in the communities of plants which are on the forest floor, and the ones which die off further improve the soil quality.

Finally, we reach the mature forest stage, where the animal and plant communities are stable, and as a tree dies, a sapling takes its place.  In some ecosystems, trees can stay short, like a new tree, for years until a gap opens up in the canopy, then they all race to be the one to take the place in the sun at the top.  Whilst individual trees may change, the overall structure of the forest stays the same at this point, which provides stability for the animal, bird and insect populations, and leads to the forests which we love to walk in.

Whilst the exact age at which a forest is defined as mature varies (depending on the types of trees which are present), a mature forest is several decades old.  If these forests are able to continue developing, they eventually are classified as Ancient Woodlands, which in the UK means forests which have been there for 400 years or so (the current definition of an ancient forest in the UK is forests which have existed since 1600).

EDIT FOR UPDATE: I have found out that one of the woodlands affected is actually an Ancient Woodland, which is believed to have been in place for around 1000 years. Info about Ashwellthorpe HERE

Ok, so now you know why I feel that mature forests are important.  They provide a stable habitat for wildlife and other plants, and due to the length of time which it takes for them to develop, they are not something which is easily replaced.  They also play a role in preventing soil loss from rain or wind erosion.

Now, you are probably wondering why Ash trees are so important, and why the media have been giving this so much attention.

Ash is the fourth commonest tree in the UK, and many forest areas have it as the dominant species. (source: Woodland Trust). Birds such as woodpeckers and owls live in Ash trees, as they are easy for them to hollow out, and they provide food and a habitat for a diverse range of animals, insects, mosses and lichens (For more info, see the Royal Forestry Society link HERE)

Ash woodlands are part of the UK Biodiversity Action Plan, and are listed as a priority habitat in the plan. (See page 60 in this PDF), and they say:

“Mixed ashwoods are amongst the richest habitats forwildlife in the uplands, notable for bright displays of flowers such as bluebell.. primrose..wood cranesbill and wild garlic . Many rare woodland flowers occur mainly in upland ashwoods, such as dark red helleborine.., Jacob’s ladder.., autumn crocus.., and whorled solomon’s seal … Some rare native trees are found in these woods, notably largeleaved lime… and various whitebeams…. Upland mixed ashwoods also harbour arich invertebrate fauna, which may include uncommonor declining species. The dense and varied shrub layer found in many examples can in the southern part of the types range provide suitable habitat conditions fordormice… The alkaline bark of old ash (and elm where it still survives) supports an important lichen flora…. ”  (Latin names have been removed, hence the dots)

Aside from the ecological importance, it has a long history in the UK and Northern Europe, it is suggested as  the “world tree” from Norse Mythology (Yggdrasil) and Ash has been used in the UK since early history, as everything from spears to walking sticks, furniture etc.

So, seeing as these woodlands are on the Priority habitat list, you are probably thinking that the government has taken immediate action on this, and had in fact begun to assess this threat as soon as they heard of it.  Well….not quite.  George Monbiot over at the Guardian has pointed out that the government were made aware of the threat to the Ash tree in the UK some time ago, before the imported infected trees were discovered, and that even importers of Ash trees were recommending that action be taken (link HERE)

So, what is the government in the UK doing?  They have announced that a ban is being implemented starting Monday (link HERE).  Bear in mind this fungus was first found in the UK 8 months ago (February)…. Would it have taken so long for action to be taken if we were talking about infected livestock?

I apologise for the very long post, but I feel it is important that I explain exactly why we need to make sure that we do not lose our Ash trees the way we lost our Elms, and I am very angry at the government response.

Last time we met the Spider Conch and today, we meet some of its relatives, the bivalves.   As the name suggests, these animals have two shells, and the ones you probably know best are oysters and clams.  Today I will write about the various feeding methods of these animals, and then the next post will be on movement and vision.

There are bivalves which resemble a 2-shelled animal we met earlier, the brachiopod (HERE), and so can be easily confused.

The first bivalve I would like you to meet today is Pedum spondyloideum, or the blue-lipped coral oyster. I am mostly showing you this one because I think it is spectacularly beautiful

Blue lipped coral oyster. Image from wikipedia

This is a teeny tiny scallop (or Pectinidae to give it the proper family name), which lives between corals.  These are in the same order as oysters (Ostreoida), so are related to them, but are in a different family to what me and you know as oysters.

There is an important differences between these, and the other molluscs we have met so far;

General anatomy of a bivalve. Image from Merriam-Webster

I mentioned before (HERE) that molluscs have a rather cool tongue called a radula, which is essentially lots of rows of tiny teeth that they use for scraping food off of surfaces.

If you look at the diagram above, there is no label saying “radula”.  This is because bivalves do not have one!  (They also do not have a head!) The image below shows the internal structure of a clam, and will help me explain what they do instead of scraping food:

Internal anatomy of a clam, image from Encyclopedia Britannica

In the image above, you can see something labelled the “incurrent siphon” and the “excurrent siphon”. As these animals breathe (by extracting oxygen from the water), they cause small currents around their gills.  These currents contain not just water, but yummy particles of food, which get moved towards the gills.  There are cilia (those small hair-like wavey things we have bumped into a lot) on the gills, which move these currents towards tiny pores.

If you take a peek at the top diagram, there is something labelled as the “labial palps”.  These, and the gills produce mucus (like you do when you have a cold), and this covers the food particles and they fall down towards the mouth where they are eaten.  So yes, they do eat food covered in snot!  Large particles like sand fall down into the mantle, and are carried out by cilia again (those little hairs just get everywhere don’t they?). Sometimes these particles get stuck in the mantle, and become irritating, at which point they become pearls (although not the sort we use for decoration, they are formed differently).

This method of feeding is known as filter feeding, and is how most bivalves eat. There are some species however, who obtain their food using a method known as deposit feeding.

This is thought to be the original form of feeding for bivalves.  Instead of the gills assisting in filtering food, they are used purely for breathing, whilst the labial palp has tubes attached to it which stick out to grab food from the sand or mud.  Food which is caught in currents moving towards the gills is also grabbed and eaten.

Still other species use symbiosis with small organisms (a lot like the corals do) whereby these organisms carry out photosynthesis and the bivalve gets most of its nutrition that way, while doing a small amount of filter feeding.  The most well known example of this is the giant clam, which is a huge animal, up to 1.2m or so long.

Giant clam, image from wikipedia

These animals are so huge that they are not able to move, so they sit on the sea floor, often in places like the Great Barrier Reef:

Giant clam on the Great Barrier Reef. Image from National Geographic

The bacteria, and dinoflagellates which I wrote about HERE obtain food by photosynthesis, like plants do, and then the Giant Clam feeds on the by-products produced, as shown in this video:

One final point about bivalve feeding.  Because they filter feed, they also perform a role in cleaning water, which benefits other organisms in their ecosystem, and mussels can be used as an indicator of how polluted a body of water is.  This is because as they feed, heavy metals and other pollutants are filtered, and build up within their bodies as they are unable to process them (like us with mercury etc).  So, if you measure the levels of these pollutants in mussels and other bivalves, it gives you an idea of how polluted the area is.

This video shows oysters and how they can function as filterers of water:

As mentioned in the video, populations of bivalves are decreasing in some areas, and this means they are less able to filter the water, which in turn has an impact on the other animals and plants in the ecosystem.

I am going here:

Jutland. Image from wikipedia

to investigate why these:

Beavers. Image from Wikipedia

have moved house, like this:

Moving house! (Beavers do move house like this, honest!). Image from wikipedia

So, I am off to spend a week getting muddy and wet and interviewing lots of trees and plants, so I will not be blogging again until next Sunday most likely, as there is no internet there!