Birth of a Backswimmer (Friday 5)

A few months ago, I posted a series of photos for Friday 5 that depicted the development of aquatic snail eggs.  In addition to the two species of snails I had in my tank at the time were a bunch of backswimmers in the genus Notonecta.  The morning after I put them in the tank, I came across a bunch of what could only be backswimmer eggs attached to a leaf, so I started photographing them.  I thought their development was fascinating and spent a little over two weeks watching the snail and the backswimmer eggs to see what happened.  Today I give you the Notonecta part of the story!

The eggs started out looking like what I would consider pretty standard true bug eggs:

Notonecta eggs, 1 day old

Notonecta eggs, 1 day old

They were simple to start off, just translucent white cylindrical eggs with rounded ends.  Many eggs were attached to this leaf in a sort of neat little line along the edges, but there were others attached to rocks and even a few stuck to the large rams horn snail that was oozing its way around the tank, so I suspect this was simply a convenient place to deposit them rather than a preferred method of placement.  In just under a week, some changes were evident:

Notonecta eggs, 6 days old

Notonecta eggs, 6 days old

This photo isn’t as well focused as I’d like, but it illustrates two things.   First, the structure of insect egg shells is absolutely stunning!  All of that patterning mirrors the cells that laid down the chorion (= the insect eggshell), so you’re effectively looking at structure of the mother’s internal organs when you look at an insect chorion.  In both eggs you can also see some faint red markings, more distinctly in the egg on the right.  Those red patches are the developing eyes of the backswimmers, so you can see which end is the head and which is the tail.  What was previously a little cylinder of bug goo had turned into the start of a baby insect with clear evidence of the changes visible without dissecting the egg in just a few days.

Things started to change more rapidly after the first eye spots were visible.  By day 10, the eggs looked like this:

Notonecta eggs, 10 days old

Notonecta eggs, 10 days old

The red eye patches had taken on the shape of backswimmer eyes by this point.  You could also see some black markings within the egg.  The bugs inside were clearly further along than they had been.  You could also easily spot the eggs that were not developing and were never going to hatch at this point.  The egg on the left side of the image was having problems and wasn’t developing properly – it has no eyes or any black patterning visible.  It never hatched.

Shortly before they hatched, you could see all sorts of structures inside the eggs:

Notonecta eggs, 18 days old

Notonecta eggs, 18 days old

You can’t see it very well without enlarging the photo (click to enlarge!), but you can see the outline of the plates on the upper surface of the thorax, the legs, and that the black markings are part of the legs.  By this point, the eggs were two and half weeks old and a few had hatched.  The empty chorions in the lower right corner highlight the cap of the egg the nymph inside popped open to emerge from the egg and a membrane that lined the chorion.  The eggs in this image hatched over three days (if they hatched at all), so they seemed to have some variability in their developmental times.

This is what came out of the egg:

Notonecta first instar

Notonecta first instar

The first instar nymphs were tiny, just a few millimeters long.  You can clearly see the bright red eyes and the black claws, both of which were visible through the egg chorion as they developed.  And, as a bonus this week, this is what these tiny nymphs eventually turn into:

Notonecta mature adult

Notonecta mature adult

The coloration becomes a lot more complex, they gain wings, and their bodies elongate relative to their width as they age.  Check out those gorgeous eyes on the adult!  And, these insects are fairly large, about 1 cm, which means that they have to grow a lot to become adults, and they do it very quickly.  That tiny nymph emerges from the egg and molts just 5 times before it becomes an adult, which means massive growth spurts each time they molt.

I know it probably makes me weird, but I love watching insect eggs develop!  They undergo some pretty amazing changes in a very short amount of time, plus they’re beautiful to look at and you can often see through the chorion and peek at what’s happening inside.  Eggs might not move, but they’re still fascinating and I am thrilled I got an opportunity to document how these eggs developed!  I hope at least some of you find it as interesting as I did.  :)

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Unless otherwise stated, all text, images, and video are copyright © C. L. Goforth
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Birth of a Snail (Friday 5)

On March 4th, I was in the midst of an all out race to prep curriculum for an insect-themed afterschool citizen science program I’m developing.  One of the things we wanted to provide to the state park rangers who will be implementing the bulk of the program was a couple of vials containing examples of hand sanitizer preserved dragonfly and damselfly nymphs.  That meant getting into the pond to look for nymphs.  I had spent four straight weeks in front of my computer working non-stop on the afterschool program and was thrilled to get outside, even though it was cold in the water and we found only a single dragonfly and a couple of snails.  One of my coworkers needed photos of the snails for our pond field guide, so I promised to take them home and photograph them.  I set up my tank and put the snails in and left them overnight so the bubbles would dissipate.  The next day, I realized that one of the snails had laid eggs.  A LOT of eggs.  There were only two snails in the tank, so it had to be this one:

Physid snail

Pouch snail (family Physidae)

… or this one:

Planorbid snail

Ram’s horn snail (family Planorbidae)

 

And I have to say: those snails and their eggs enthralled me!  I was exhausted and overworked, so nothing gave me more satisfaction than watching my two snails, one of which was going to be a mother of several hundred baby snails, gliding around the tank every evening after work.  I took the photos we needed for the pond guide the day after I set everything up, but I kept watching and kept photographing over a few weeks.  Today I am going to show you what happened.  Let’s start at the beginning…

March 6, 2015

Snail eggs, Day 1

Snail eggs, Day 1

I added the snails to the tank on March 5 and left them overnight, so these eggs were less than 24 hours old when I first saw them.  I love that you can see a little dot in the center of the mostly clear eggs!  Nutritious yolk perhaps?  A little cluster of cells that would become the snails?  I really have no idea as I know little about snails, but I thought they were rather beautiful.  There were lots of clusters like this in the tank.

March 11, 2015

Snail eggs, Day 7

Snail eggs, Day 6

After 6 days, the shape of the little embryos inside the eggs were becoming much more snail-like.  You could see some little curved snail bodies and the very beginnings of their shells.  The color comes from the light hitting a piece of wood in the tank under the leaf these were laid on – they were largely transparent.

March 16, 2015

Snail eggs, Day 12

Snail eggs, Day 11

The snails were now 11 days old and you could definitely tell they were snails!  Most of the developing snails inside the egg cluster had mostly to fully developed shells, though still tiny, and had taken on a distinctively spiraled shape.  A few had already broken free of their eggs and left the cluster, including the one in the lower right of the egg cluster who is making a break for it in this photo.

March 18, 2015

Snail eggs, Day 14

Snail eggs, Day 13

By this point, most of the snails had escaped the egg cluster, though a few late bloomers were left.  You can still see the leftover egg compartments and the jelly that held the cluster together if you look hard.  Looks like there may have been a couple of dud eggs in the lot too that probably won’t ever hatch.

March 19, 2015

Baby snails

Baby snails

Baby snails!  There are now about 50 of these on the loose in the tank, each about 2-3 mm long.  They’re absolutely tiny – small enough you’d mistake them for shmutz on the glass if you didn’t know what you were looking for – but they move pretty darned fast for such tiny little animals!  They’ve spread out across the entire tank in just a couple of days.  For some reason, I feel like this is an impressive feat for a 2mm long snail.

And, now that the baby snails have hatched, I can look at their shells and tell that they are pouch snails and not the ram’s horn snails.  That meant that possible baby mama number one above was the parent of dozens and dozens of eggs that are still developing and many more than have already hatched.  She was rather prolific in her laying and I just found another clutch today.  I’m going to have SO many snails in a couple more weeks!  In the meantime, I’m going to enjoy watching these grow.

While all of this epic snail drama was going on, I had a similar situation happening with a bunch of backswimmers.  I’ll share my baby photos of those guys soon.  In the meantime, have a GREAT weekend everyone!

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Unless otherwise stated, all text, images, and video are copyright © C. L. Goforth