Protozoan parasitizing a mosquito larva ?

The Sierra Nevada of California right now is blooming. The hills are brushed in the purple, golds and yellows of the California floral palette and beneath the old firs massive bolete mushrooms are pushing up through the duff, nearly asking to find themselves on a dinner plate. Water is abundant and where it has pooled, a bloom of mosquitoes is brewing. A good friend from my Bozeman years asked me to shoot some video of the larvae with the Foldscope, which like many projects seems easy at first, but as per usual the devil is usually in the details. Below is the imagery and a questions they generated for me about the biology and then I’ll get into the technical notes on how to find larvae and how to image live ones.

Live mosquito larva (moving up abdomen to siphon that is at the surface of the water):

 

Dead mosquito larva (starting at the head and then moving to the siphon and then back up the other side):

 

Still frame of anatomy of interest:

mosquito larvae parasite(?)

Video of the Vorticella (Thanks @Laksiyer for the ID) feeding. Video is slowed down 4X so that you can see the particles getting sucked in.

 

What the heck are those goblet shaped structures? I’ve looked at a couple general mosquito larva illustrations and images online and none seem to show this. I am wondering if this is some sort of parasite upon the larva? The general shape reminds me of zoosporangium of oomycota, but really I’m at a loss for what these structures are. I’m fairly sure they are not part of the regular anatomy of the mosquito larva. Does anyone have any ideas?

How to find mosquito larva: In the Sierra I’ve noticed an interesting trend, which is I don’t find a ton of mosquito larva in small puddles on the ground or in ponds/lakes. However, if you can find an old stump with water in it I almost always find larvae in there. Ponds that have lots of rotting logs however do seem to have larvae. Either way, get close to some water and look at the surface for little bobbing worm shaped critters that shuttle away from the surface as you approach and then return to the surface in a short period of time. I found my larvae in a stump and took some home in a little tube:

IMG_6347 IMG_6348 IMG_6350

 

 

 

 

Anytime I’m out in the field looking for critters I use iNaturalist to make observations, because if I use my cell phone it automatically grabs my GPS coordinates and a time stamp, which gives me rich meta data around observations. I can always add things like microscopy to an observation once I get home. Also there are just a bunch of nice people on there that help me ID all of the stuff I don’t know. Here is the observation for these mosquito larvae: http://www.inaturalist.org/observations/3188258

How to image a live mosquito larvae: I quickly realized slapping a cover slip on a mosquito larvae would not work, because it is so big and with my focusing skill on the Foldscope it would quickly lead to death my crushing. I figured I wanted something that could have a well in it that I could push on without it crushing and was big enough to accommodate the larvae and its water. Using a coverslip, glass slide, nail polish and bits of rubberband I made the following well on a slide system:

IMG_6612 IMG_6647IMG_6619

 

 

 

 

The trickiest part about building the well was building up the nail polish along the edge of the coverslip as it will sort of capillary action pull its way under the glass slide, so I found it easiest to put a few small beads on the edge of the coverslip, let them harden and then come back and add beads of nailpolish between those and this minimized how much of it spread out beneath the coverslip. The mosquito larvae seemed relatively “happy” in the glass mount and made it easier to image. The only trick I didn’t use that I wish I would have in retrospect was tossing the mosquito larvae and slide in the fridge for a bit to cool it down a bit as many of the first videos weren’t any good because it was flicking around to much. The mosquito larvae expired while I was at work, probably because most of its water evaporated, but this did make it easier to image! I used the magnetic mount for the Foldscope with my iphone5 and zoomed in a bit in video mode to get rid of the vignetting and used a desk lamp as my light source.

3 Comments Add yours

  1. laksiyer says:

    Wow.. what a fascinating post. I love your rubber-band nail polish mount.. Removing it thought might be a pain. I have used two sided tape quite successfully for such kinds of wet mounts and I have gained a great liking for these plastic coverslips (few more thing to add to the kitty). I suspect those protozoan that you saw might be stalked vorticellae. They are commonly observed on mosquito larvae. See a post by Manu (see the video around the 1st minute).https://microcosmos.foldscope.com/?p=906
    I wonder if there is some kind of a symbiosis between the two or if it is a “just so”. But it has been observed independently on many occasions.. Perhaps it is the right microaerophilic depth for the vorticellae on these mosquito larvae. Love reading your posts.

    1. Manu Prakash says:

      @laks : love the symbiosis or parasite theory. Every single time I collect mosquito larvae in the field – right around the anus – see vorticella. Since a lot of stuff is dumped out – I could imagine a cloud of bacteria around. It’s interesting strategy for something that is “stationary” stalked to be attached to something that is mobile – you get best of both worlds 🙂

      What a wonderful post @Damontighe. Absolutely love the illumination and the natural history context.

      Here is another parasite (ambiphyra) I found on fish fins..
      https://microcosmos.foldscope.com/?p=14627

      The question is – if you watch log enough, do they contract?

      Cheers
      Manu

      1. damontighe says:

        @Laksiyer – Thank you so much in identifying the protozoan! Looking at Manu’s video I do see them around the anus and revisiting mine I see there is a large number near the anus and clusters around the base of lateral hairs on the abdomen. I wonder how much of location is about access to potential food (anus) and simply finding a surface to adhere to since both the abdomen and anal cluster seem to be right next to where the hairs emerge.

        As to the question of what sort of interaction does the Vorticella have with the mosquito larva, according to the below paper its a negative effect and has potential application as a biocontrol agent.
        http://jad.tums.ac.ir/index.php/jad/article/viewFile/390/307

        So that it would be easier to see what the Vorticella were doing I used the youtube editor to slow down the video to 4X and isolated just the few seconds where it the Vorticella can be seen sucking in particles from the water. I added it to the above post, but a link is also here: https://www.youtube.com/watch?v=uVV1fSWllVo

        @Manu – I did see a few of the stocked Vorticella move side to side, but I never saw one contract. The fish parasite is cool! I’ve seen a few big copepod parasites on sharks in the bay and I’d love to catch another to get it under the scope: http://www.inaturalist.org/observations/2931950

        I’m trying to reuse the slide nail-polish-rubberband slide by simply washing out the chamber, letting it dry and then will refill when I try to shoot another organism that doesn’t fit nicely under a coverslip.

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