fertilization

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Day 5 EMBS – The final sprint

It’s not fun to get the presentation slot first out on the morning after the conference dinner. But Katarina from Estonia got a good attendance and gave an interesting presentation on the zebra mussel (Dreissena polymorpha) and its impact on the ecosystem of the heavily eutrophicated Pärnu Bay in southern Estonia.

Maillie Gall from Australia told A story of two sea urchins, in which she compared the population genetics of the two sea urchin species Heliocidaris erythrogramma and Heliocidaris tuberculata to see how far their larvae spreads. She has primarily examined whether the duration of the planktonic larval stage plays a role for the spreading distance. It was very nice to rest those weary eyes on some beautiful pictures of sea urchins and Australian waters.

Jennifer Loxton held one of the conference’s coolest presentations, according to me. She showed how a bryozoan (phylum Bryozoa, it’s an animal) that came into English waters recently from Japan, reproduce like crazy. With movies and beautiful microscope images, we see that most of the currently known bryozoans form one egg bump per individual, where a larva is formed which then swims away and form a new colony. The Japanese moss animal produces up to five bumps, simultaneously! Unbelievable. The animal is red in color and thrives in cold water with high salinity, so we’ll probably not see it at the Swedish coast.

Final speaker of the conference was Paul Somerfield from Plymouth Marine Laboratory, renowned marine biologist and statistician, who talked about how to use statistics and not place too much weight on that which is odd or rare if one wants to describe an overall pattern. The presentation was entitled “Putting the species back into community analysis “. Funny, easy to understand and relevant!

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Seaweed project within BalticSea 2020

Anyone who is interested in the Baltic Sea might have heard of Baltic Sea 2020 Foundation.
Baltic Sea 2020 is a foundation founded by Bjorn Carlson through a donation of 500 million SEK (55 million EUR). The Baltic Sea 2020 Foundation’s assets shouldfund projects that are action-oriented, innovative and helps to improve the knowledge of the Baltic Sea continuously until 2020. The BalticSea 2020 Foundation began its work in 2006 and has to date initiated more than 70 projects, of which 25 are ongoing.

One of these projects is about trying to re-establish bladderwrack inside Björnöfjärden, a bay outside Stockholm. Björnöfjärden is heavily eutrophicated and the water is quite turbid with particles that prevents the light from penetrating. It quickly becomes dark below the surface, so that only a few stands of seaweed survive here. Observant locals have informed us that there was plenty of seaweed in the Björnöfjärd in the past, however.

So, seaweed enthusiasts to the rescue!

Susanne Qvarfordt is ready to establish bladderwrack.

Susanne Qvarfordt is ready to establish bladderwrack.

Susanne Qvarfordt from the environment surveillance company Sveriges Vattenekologer has initiated a project that will examine what factors might prevent the seaweed population from re-establishing in Björnöfjärden.
In addition, she asked the BalticSeaWeed blog to help with our expertise!

So, during the first days of June, we collected fertile tips of bladderwrack. These were sexed (we cut the receptacles and see if they are male or female), so that we would get an appropriate ratio of males and females at each site.

Sexing seaweed is best done with a scalpell and a magnifying glass.

Sexing seaweed is best done with a scalpell and a magnifying glass.

The bladderwrack were made into small beautiful fertile bouquets which were then attached to a grid. These will be placed in the water, floating over a number of concrete plates, and hopefully make new small seaweed babies that can attach itself to the plates.

All is ready for a baby boom!

All is ready for a baby boom!

So, now we have placed three grids in Björnöfjärden and three in nearby Fjällsviks Bay, to see if any of the other actions carried out in Björnöfjärden will affect the seaweeds ability to reproduce.
So, keep your fingers crossed that no one gets caught with their anchor or fish tackle in our beautiful grids, and hope for calm weather at Midsummer full moon so that there will be many wee ones.

Placing a seaweed grid with buoys.

Placing a seaweed grid with buoys.

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Spinning eggs for Easter

I am going to render a normal conversation that often happens when I talk about seaweed and what I do.

– So, you work with seaweed. Nice! What do you do with it?
– Well, among other things I try to cross different species with one another in order to understand how speciation occurs.
-That sounds interesting. When does the seaweed bloom, then? Or….does it have flowers?
-Nope, it has eggs and sperm just like us. Bladderwrack and narrow wrack have male and female plants and actually have an almost identical lifecycle to humans.
-It has eggs and sperm?! But…is it an animal, then?

Suddenly you realize that what you learned during biology class in school was just a rough cut, simplified picture of reality. Nature and evolution is so much more than that, with more imagination and concepts than we humans are able to name.

I think it is fantastic that algae, some of the planet’s first living organisms, have used eggs and sperm for a long time. Maybe longer even than humans have been around. A flick on the nose at us when we think we are evolutionarily advanced.

Here’s a video of how eggs from bladderwrack start spinning by all the sperm swimming around them, hoping to fertilize. Beautiful!

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Reproduction

Narrow wrack (Fucus radicans) and bladderwrack (Fucus vesiculosus) have separate male and female plants. The reproductive organs are called receptacles and are placed at the tips of the plant. They are easily recognised by their warty structure.

When we try to “sow” seaweed”, we start with collecting ripe plants from the field, determine which sex they have, and cut of the receptacles.

Cut receptacles of bladderwrack

Cut receptacles of bladderwrack

The picture to the left shows a bladderwrack ready to sow. Note that the pile of cut receptacles to the right in the photo is from three plants.

In order to separate between males and females, one has to cut a mm-thin slice of the receptacle and (with a little magnifying help from a loupe or similar) see if there are oogonia (8 eggs in a small sack) or antheridia (64 sperm in an even smaller sack). This can only be done on ripe receptacles, or else it is very hard to see.

Round oogonia contains 8 eggcells. Some are beginning to open up.

Round oogonia contains 8 eggcells. Some are beginning to open up.

Each receptacle consists of several small chambers, conceptacles. The opening pore of these conceptacles are what causes the warty structure of the receptacle. Each conceptacle openes onto the receptacle surface, and this is where oogonia and antheridia (eggs and sperm in bags) are ejected out into the water mass during fertilization. When the oogonia and antheridia have reached the water, the bag keeping them contained, begins to dissolve.

The female oogonia looks like a collection of small green peas, and can be seen with the naked eye if they are very ripe.

It's a girl! Lots of ripe, round oogonia in the receptacles.

It’s a girl! Lots of ripe, round oogonia in the receptacles.


A ripe male, packed full of orange sperm.

A ripe male, packed full of orange sperm.

Antheridia are too small to see, even with a loupe. You need a microscope for them. On a receptacle cut, they give an impression of orange balls along the inside of the receptacle edge (see picture). The colour comes from the eyespot of the sperm, which is orange. With this, the sperm can tell light from dark.

Reproduction occurs around full moon, when it is much darker down towards the bottom than up towards the surface. The sperm “knows” that it should swim towards darkness. The reason for this is that the heavy eggs are sinking in order to attach to the bottom once they become fertilized.