Febrero 21, 2012

mad-as-a-marine-biologist:

theseablog:

Irrelephant wanted some information on Sea Squirts/ascidians, so here we go. Prepare for some proper marine science.

I think ascidians are actually somewhat ignored, they’re some very beautiful animals. Consisting of around 2300 species it’s quite a diverse class although they all have some common characteristcs: They’re all sessile (attached to a hard substrate), they’re all filter feeders (meaning they filter out organic matter from the water column) and unlike other similar Tunicates they have a much tougher tunic made of polysaccharides. They can either be solitary or form colonies several meters in diameter. They have a relatively simple nervous system, with receptors for chemical changes, light and touch. All are hermaphroditic and capable of both asexual & sexual fragmentation. 

Interestingly, Nudibranchs (amongst other animals) feed on them, but also use them as a substrate for egg attachment. 

Due to the incredible filtering capabilites of these animals, they’re incredibly sensitive to pollution.

As for some interesting species, Polycarpa aurata and Rophalaea are incredibly pretty, but Didemnum (shown above overgrowing green algae) species might be more interesting due to it being a major invasive species (and only one of the many invasive sea squirts) and generally a big nuisance.

And the best part is that they are Chordates! They look like simple animals, especially in their resemblance to sponges, but are infinitely more complicated. With digestive, circulatory and reproductive organ systems they more closely resemble higher vertebrate anatomy. Their larvae has a primitive backbone - a notochord - thus it joins us in Phylum Chordata. Some believe it’s the closest we have to the ‘link between vertebrates and invertebrates’.

(vía mad-as-a-marine-biologist)

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    my inner nerd!!!!!
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    they also have spicules embedded in their tunic used for defense which differ in shape and size based on the species...
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