aquatic invertebrates – part one

Yes, it’s still winter. And no, I didn’t see these on the weekend. However, just as some people enjoy poring over seed catalogues while anxiously awaiting spring, I like looking through photos, anticipating what I’ll soon be seeing once the snow goes away.

Recently, the subject of bioindicators and aquatic invertebrates came up at Niches. That, in turn, got me thinking about past years doing frog pond and stream surveys. Almost inevitably, that led to investigating monitoring programs that I might participate in this coming year.

That brings me to this morning, pondering over what to write about today. I decided to dig up some photos of aquatic invertebrates seen while I’ve been out on past surveys. They might be of interest to some of you, and perhaps make you anxious to get out and look for some in your own area. I’ll make this a two or three part series depending on what other photos I come across in the next few days.

The top photo is of a Water Scorpion insect – from the genus Ranatra, which is part of the family Nepidae, belonging to the order Hemiptera (True Bugs). The Water Scorpion is usually found suspended upside down, floating just beneath the surface of ponds or slow-moving bodies of water. Despite the name, it really has nothing to do with scorpions — the tail end’s actual function is to assist in breathing. This creature uses its clasping front pair of legs to seize prey, which it feeds on with sharp mouthparts in the head. It has wings, but these are kept tightly folded against the abdomen. The insect is not a strong swimmer, propelling itself through various kicking and bobbing motions or by grasping nearby vegetaion. Its motions don’t seem particularly controlled. Here’s a page with more info about them if you’re curious in knowing a bit more about them.

The next creature is what is commonly known as a Fairy Shrimp. I believe this one is a species of Eubranchipus. These are tiny crustaceans that may be found in vernal pools – in this region, early May is a good time to look for them. As you can see from the above photo (click on images for larger view), they have a series of little legs that they use to propel themselves through a wave-like motion. You’ll need a magnifying lens to get a good look at them as they aren’t very large. Here’s a bit more about Fairy Shrimp from the Vernal Pool Association website.

The rest of these photos are of the aquatic larvae of the Caddisfly (order Trichoptera). This source states that there are 800 species in North America. Depending on species, most Caddisfly larvae form various kinds of cases as a refuge that provides camouflage and protection. I’ve included examples of two of the typical types of cases that may be found. The above example is made of organic debris such as bits of leaves, spruce needles, and other stuff (click on the photo to get a better look at the material). The photos below are of the other type of case which is made of tiny stone fragments cemented together with silk produced by the larvae. Often, small bits of grass or other debris are cemented together with the stone fragments. The stone fragment cases are usually found on the underside of rocks in streams. Some Caddisfly larvae are free-living and do not form cases. They are usually predatory species that move about as they search for prey.

In the two photos above, you can see the larvae sticking out of the case. They emerge to feed, but when disturbed, will pull back inside of their refuges.

As you can see from the photo below, some of these cases are incredibly intricate. The stone ones don’t usually look quite this way when you find them beneath a rock. However, if you find some empty cases, gently clean them off to reveal the beauty of these tiny marvels. If you want to know more about Caddisflies and their larvae, here’s an interesting page with photos and information.

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6 Responses to “aquatic invertebrates – part one”

  1. Marcia Bonta Says:

    As always, Bev, your blog is an excellent natural history lesson. It makes me long for a pond of my own.

  2. Ontario Wanderer Says:

    Good morning Bev, Hummm, this is a great blog for a record breaking cold morning (-20 in Hamilton). It gives me something to look forward to in a month or two. I’ve not really taken many photos of water creatures other than frog, and turtles. I guess a dip net and a jar are in order.

  3. Wayne Says:

    Which do I like best, the fairy shrimp or the caddisfly cases? The water scorpion or the caddisfly cases?

    I like them all, but those are beautiful cases. Are they on the mesh of a zo-net? The selection and placement of the tiny bits of rock are amazing. They look just like they do down here!

    Regarding the water scorpions, as well as dragonfly nymph forms – I image our ornamental ponds are full of these things but I have not yet gotten around to sampling for them. I’m thinking that I’m really needing to use our kitchen aquarium for holding such samplings, rather than for tropical fish (which it doesn’t hold anyway). It adorns the dining table room, though, and the last time we tried this it kind of grossed out a set of dinner guests.

  4. burning silo Says:

    Marcia – Ponds, creeks and wetlands are such fascinating places. When I was about five, the little pond at the end of our street was like a magnet for me. I used to like to go down with a pail to try to catch tadpoles and other small creatures to look at. If anything, I like doing that even more now! (-:

    OW – It’s cold here too. -26C (or -15F). The windchills is supposed to be around -42C (or -44F). Very frigid. I’m looking forward to warmer weather and pond creatures in a couple of months too. Yes, definitely get out there with a dip net and a jar!

    Wayne – Decisions, decisions! I went through this yesterday morning while trying to decide which photo to put at the top of the post! I finally went with the water scorpion due to the size and shape of the photo (otherwise, I couldn’t decide!).
    Re: the caddisfly photo — I think it might have been on top of a butterfly net that I always bring along on stream surveys in case I want to capture flying insects.
    I expect your ponds could have water scorpions – they’re actually quite common, although few people seem to see them. They make interesting aquarium guests. I have kept various aquatic invertebrates in an aquarium on my sun porch for awhile to study them. However, here’s the warning about most of these creatures — and I expect you already know what I’m going to write. Most aquatic invertebrates have a one track mind — eat, eat, eat. Therefore, expect to see plenty of creatures eating other creatures. You bring a bunch of little things inside and check the aquarium the next day and find empty snail shells and bits of other body parts floating around, and a few of the “survivors” cruising around looking for more victims. A few years ago, while out on a stream survey, I put two water beetles into a plastic yogurt container. About 15 minutes later, I opened to lid to add something else and one of the beetles was halfway through feeding on the other beetle. Not a pretty sight. Definitely *not* the kind of thing to impress certain dinner guests!

  5. Drhoz! Says:

    nice photo of a carnivorous water bug, on a carnivorous water plant – that IS a bladderwort it’s perched on, isn’t it?

  6. burning silo Says:

    Drhoz – Yes! That’s a bladderwort. The stream where I shot this photo has a lot of it floating around. I bring a small plastic aquarium along with me in the canoe when out on surveys and just scoop things out to photograph so the two must have been rounded up together – a deadly duo.