Water Surface Fleas?

[JENnKerry]

Hey Dr. Ron. My wife was doing a water change on our 55 gallon last night when she noticed ALOT of these little white flea like bugs racing across the surface of the water. They really didn't go underwater, just along the surface. They also didn't look like amphipods or copepods. Any idea? Thanks

Kerry

[rshimek]

Hi,

I would need an image of them to be sure, but they sound like a flightless marine midge (=gnat).

Here is some information about them:

Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Group Name: Chironomidae
Common Name: Marine Midge
Pontomyia species.


Maximum size: Up to about 1/8th inch (3 mm) long

Range: Indo Pacific

Minimum Aquarium Size: Small tank (10 gal, 38 L) or larger

Lighting: Immaterial.

Foods & Feeding: Larvae feed on algae and detritus; adults don’t feed.

Aquarium Suitability Index/Compatibility: Occasionally found, a real curiosity. Harmless or beneficial.

Captive Care: These flightless gnats are some of the few wholly marine insects; live in tide pools or shallow lagoons, probably enter aquaria as larvae in algae in/on live rock. Are noticeable as small bugs skating on the water surface. They move only on their front two legs, and only the males will be seen. Larvae feed in masses of algae or detritus. Adults flightless, do not feed; males skim over the surface looking for a female; grub-like females lack even the vestigial wings of the males, and may not even have legs. Adults live only a few hours; males die after copulation, the females after egg deposition. Eggs hatch into a small grub or maggot, these find algae and detritus and live in it. After four larval stages, they form pupae, and emerge as adults.

Here is an image (the wing pads are vestigial, they can't fly):

http://reefcentral.com/gallery/data/500/41Aquarium_Gnat2.jpg

[JENnKerry]

Thanks for your help Dr. Ron. I lookedat the tank this morning and they were all gone ( as far as being noticable on the water surface). Are they nocturnal? From the looks of your picture, I'd say that's what they are. As long as they're harmless.

[rshimek]

Hi,

I don't know if they are nocturnal. It would make sense if they are. You are only the second person I know of who has had these come in on something. Rather neat, really. And, yes they are harmless, probably somewhat beneficial as the maggots eat algae and detritus.

[JENnKerry]

Cool. More critters for the sandbed. That's a plus :D
Thanks again for your help

Kerry

[Telgian]

I've seen them on occasion; first in the nano that I started with (4.5 gal.), and as recently as a week ago, when I noticed one skittering along on the surface. Assuming that they are the same critters that is.

I can't recall exactly when I saw them with respect to the lighting. I'll pay a bit more attention in the future.

Thanks for the information on them. Another mystery has a name. :D

[rshimek]

Hi Telgian,

See if you can get an image. It is possible I suppose that FW water striders could be found in marine tanks.

[JENnKerry]

Yea, I want to say that is the bug that lives in the tank. I was looking at the dead ones and the body resembles the picture you posted. Your right, they dont live long, I wake up in the morning to see these little dead bugs on the top of the water. I thought they were gnats that were getting caught up in the light then drowning in the tank. But after seeing them skim across the water super fast, that all makes sense. I know they had to come in on the live rock. As long as they dont harm anything, I have no problem having them. Pretty cool I must say

[Telgian]

I'll try to get a picture next time I see one.

I'm not sure that it is a FW water strider, or at least these don't have the appearance of the water striders that I used to catch as a kid from a nearby creek.

There's a picture of the FW version that I'm familiar with here (http://www.enature.com/fieldguide/showRguide.asp?rguideID=710&speciesID=3796).

And a direct link (http://a1410.g.akamai.net/f/1410/1633/7d/images.enature.com/insects_spid/insects_spid_m/IS0099_1m.jpg) to the picture to avoid the advertising. :D

(Gaah...this doesn't help me resist the urge to start a 40gal. full of creek critters!!! Any marine equivalents to boatmen and whirlybeetles???) ;)

[Edit: Blah dunna wirk 'ere.]

[rshimek]

Originally posted by Telgian

Hi

I'll try to get a picture next time I see one.

<b><font class="nf" color="deeppink">THANKS!!!</b></font>

I'm not sure that it is a FW water strider, or at least these don't have the appearance of the water striders that I used to catch as a kid from a nearby creek.

Yes, these little guys are rather distinctive, that's why I wanted an image, just to verify what you are seeing. Your photography is generally good, so that would be a double bonus. :D

(.... Any marine equivalents to boatmen and whirlybeetles???)

No. The only fully marine insects are about 30 species of flightless water striders (in the genus Halobates) and these little midges. No beetles, etc....