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The Daily Bucket is a regular feature of the Backyard Science group.  It is a place to note of any observations you have made of the world around you.  Sun, rain, seasons...snails, insects, ferns, meteorites, climate, birds and/or flowers....  All are worthy additions to the bucket.  Please let us know what is going on around you in a comment.  Include, as close as is comfortable for you, where you are located. Each note is a record that we can refer to in the future as we try to understand the patterns that are quietly unwinding around us.
Most of us are familiar with the radical changes in appearance we see from caterpillar to butterfly, or tadpole to frog. But insects and amphibians are not the only kinds of animals to undergo metamorphosis. Let's take a look at creatures that spend their whole lives in water. Aquatic animals - which are for the most part invertebrates - have very different lifestyles as youngsters than they do when they grow up.  They eat different food, have different predators, prefer different habitats.

You may recollect the difference between the adult Bubble Snail and its microscopic larval form, a good example of this.

gastropod veliger
METAMORPHOSIS is a biological process by which an animal physically develops after birth or hatching, involving a conspicuous and relatively abrupt change in the animal's form or structure through cell growth and differentiation...which is usually (but not always) accompanied by a change of habitat or behaviour. (biology-online.org dictionary)

The word "metamorphosis" derives from Greek μεταμόρφωσις, "transformation, transforming", from μετα- (meta-), "change" + μορφή (morphe), "form".

The vast majority of aquatic invertebrates have drifting (ie. planktonic) larvae, whether they grow up to be crawling, swimming, burrowing or even totally stuck in place as adults. The young float away from their parents in ocean currents, an extremely successful mode of dispersing a species throughout the environment, sometimes thousands of miles.

It's so successful that some are easily introduced by human activity into new bodies of water, where they become invasive species. Invasive species are a serious threat to ecosystems worldwide, operating synergistically with other threats like global warming, habitat loss and pollution to degrade healthy environments. Hitching a ride with cargo ships in their ballast is a common means for aquatic invaders: in port, when a ship unloads cargo, it takes in seawater as ballast, then discharges that water, with everything in it, when it loads cargo in some other port. Considering that almost all cargo moves by sea (95% in the U.S., 80% worldwide), we're talking a huge volume of water being moved. And in even one drop of water there can be hundreds of larvae along with other planktonic organisms, like we see in this microscopic view of Salish Sea water.

The Mediterranean Sea has over 900 introduced species. In the last quarter century since zebra and quagga mussel larvae were inadvertently released into the Great Lakes, freshwater ecosystems all over the Midwest have been devastated by the effects of these bivalves. Here in the Pacific Northwest, we are fighting to keep invasive tunicates and green crabs, among others, from spreading. If you are a Northwesterner, here's a great resource for identifying them.

Regulations exist to minimize transfer of invasive larvae, both U.S. and internationally. Even fully implemented and enforced, however, invasive larvae can still find their way where they shouldn't, and of course these can't address the problems caused by existing established invasive species.

It's a deadly serious game of survival, pitting the biological imperative of one species against the carefully balanced panoply of established species in a ecosystem. Throw in the economic interests of the shipping industry vs. communities dependent on the resources of their functioning native environment, and it is a high stakes game.

But let's zero in on a small marine community now, and see how the larval forms compare to the adult creatures they grow into, all of them lovely vigorous native Salish Sea invertebrates. Just for fun, here's a matching game to see how evident the features of a larval form are. For example, as you saw for the local native White Bubble Snail, its larva has a circular, coiled shape, a clue to the circular form of adult snail shells, and their body inside.

More below the veliger larva.                                                

Here's a chance for you to test your observational skills (or good guessing!). All these photos were taken in my local waters of the Salish Sea in the Pacific Northwest, adults and planktonic larval forms. The larvae pictures were taken with a digital microscope after collecting samples with a plankton net recently. I was a little disappointed not to see any echinoderm larvae, but I guess this isn't their season right now.

(A caveat: It is impossible to tell exactly which species a larva comes from without isolating an individual and collecting what it produces. These are all wild plankton pictures, so I have picked one representative species for each larval form (one crab, one nudibranch, etc). Invertebrate embryologists may be able to distinguish between a Purple Shore Crab larva and a Green Shore crab larva, but that's beyond my pay grade. For the level of visual resolution in these photos, they would look identical.)

So, here's the game:

In the left column are larval forms, labeled by number.
In the right column are adult forms of the same organism, labeled by letter, randomly ordered. Note there are 10 larvae and 9 animals. Two of the larvae are the same animal, at different developmental stages.

Match each number to a letter (eg. 1 is X, 2 is Z). Then use the key at the end to see how well you did. If you like, please report your results in the poll.

Have fun!

(A) Feather Duster tubeworm (Eudistylia vancouveri)
barnacle l
(1)
op nudi
(B) Opalescent nudibranch (Hermissenda crassicornis)
clamworm l
(2)
(C) Clam worm (Nereis vexillosa)
crab l
(3)
(D) Giant Pacific octopus (Octopus dofleini)
octo l
(4)
(E) Hydroid (Plumularia sp)
feather d later l
(5)
(F) Acorn barnacle (Balanus glandula)
hydroid lar
(6)
orange ribbon worm
(G) Orange Ribbon worm (Tubulanus polymorphus)
nemert lar
(7)
(H) Decorator crab (Oregonia gracilis)
jingle larv
(8)
(I) Jingle Shell clamshells (Pododesmis macrochisma)
nudi larv
(9)
feather duster early l
(10)
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(In case you were wondering, that's me "shaking hands" with the octopus, back when I used to do cold-water diving. Octopuses are extremely intelligent creatures, and if you treat them respectfully, they may greet you graciously.)

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Scroll down for the answers:                                              

Answers: 1F,2C,3H,4D,5A,6E,7G,8I,9B,10A


The sea is full of animals, attached to surfaces, burrowing in the mud, swimming freely, drifting, and invisible - such glorious diversity in my backyard.

What's happening in nature where you live?



"Green Diary Rescue" is Back!

"Green Diary Rescue" will be posted every Saturday at 1:00 pm Pacific Time on the Daily Kos front page.  Be sure to recommend and comment in the diary.

Originally posted to Backyard Science on Sat Sep 21, 2013 at 07:00 AM PDT.

Also republished by Community Spotlight.

Poll

How many did you correctly match (without looking 'em up, ha)?

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50%11 votes

| 22 votes | Vote | Results

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