Lageveld

A LOVELY SUMMER MORNING. Let's go swimming, outdoors, in a clear and clean lake. Still almost nobody there, the silent water is reflecting the sky under the shining sun, so let's go in! Hmm... a bit freezing, that water. A bit more careful now, we step in the first shallow centimeters and that's how we notice a swarm water-flea-like animals that are swimming away from our feet (visible in a small movie filmpic - 1MB). These animals were Micronectae - a lesser boatman species so small that there a few people who know the name dwarf lesser boatman.

micronecta on mm scale

Micronecta (Small swimmer) species are with their 2 mm size the smallest members of the lesser water boatman family. On the picture on the right, a comparison with a common water-flea on a millimeter scale (the yellow bars). Some water-fleas are twice as large! You could meet Micronecta (plural: Micronectae) in small to very large swarms in the shallow water on the rim of clean brooks and lakes. Minute insects, living under water and not common because of general pollution: no wonder people don't know much about them. Most species are living in the tropical zone, where even in the year 2002 a number of new species were discovered, which indicates that everything is by far not known about these little dwarfs(see literature link below). The hard to differentiate species scholtzii(=meridionales), minutissima, griseola, pusilla and poweri can be found in Europe. Micronectae are, like all lesser water boatmen, living at the bottom. I did only see them in shallow water, about a centimeter in depth, on the border of streams and lakes, sometimes in small puddles at the border, with a depth off less then a centimeter . There they whirl up the loose material of the bottom with their little front legs, which are equipped with sieving hairs just like those of the rest of the Corixidae. Their need of oxygen-rich waters, explains the preference for the shallow, turbulent border zone. Especially on spots where fine material is accumulating.


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Micronecta scholtzi standing on sand
Micronecta scholtzi
(Click on the picture to enlarge)

Micronecta on sand, front side
Micronecta scholtzi on sand
(No enlargement present)




micronecta-mp3 MICRONECTA, SOUND

Click on the picture left to open a mp3 sound-file (85kb).

Like their fellow men of other Lesser Water Boatman species the males are able to make a chirping sound. (Scientific term: stridulating, which I guess is just a another word for brushing). The sound is much of a much higher pitch then that of the other Corixidae, which could be an advantage, because high tones are well conducted in water. It is also produced in a different, not fully understood manner. Fact is, that it's incredibly loud for such a tiny animal: if you put them in a petri-dish you can hear them from several meters distance. (Click on the pictures on the left for the sound). The males are passionate singers, in summer they may chirp all day long, often in choir. On the sixth segment of the male's abdomen is a tiny plate with microscopic ribs, this was held for the brush-organ and as such called strigil. But later discovery's show that this organ has merely a function in taking in air while mating at the surface. Well then, where DOES the chirping come from? Recent investigations point at... the genital! A small capsule encloses the penis and two little chitinous structures standing on both sides, the parameres. The movable capsule rubs over tiny ribs of the right paramere. (See literature link below).

Not much is known about Micronecta's behaviour. They mostly live in great swarms. In contrast to the other Corixoidae members they hibernate not as the perfect insect, but as larva.

MICRONECTA, NYMPHES
Micronecta nymphe Micronecta nymphe
Click on the pictures to enlarge

THE NYMPHE of Micronecta is translucent, specially the first stages. Almost impossible to find it on the sand, with its spotted, translucent body. It is striking to see, how after a short swimming course, it seems to disappear on the sand bottom, even at closer spotting range. The nymphes instinctively use this feature: compared to the adult insect they seem more unwilling to swim, and sooner take position again on the camouflaging sand.

Bugs often have defensive (one might say offensive) stink glands. Structures like these are also present in some water-bugs, but there they may have a role in the breathing process. At some stages of Corixa-nymphes the stink glands are distinctively marked. These Micronecta nymphes seem to have have these (brown spots on the body). Nymphes of the earlier stages have no wings and don't come up to get air. Nymphes are not a real larvae (like a caterpillar for example) because they strongly resemble the adult insect. Some scientists just simply call them larvae though.


- - Even MORE pictures - click on the pictures underneath for more on Micronecta...


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Literature: Nico Nieser - Guide to the aquatic heteroptera of Singapore and Peninsular Malaysia. IV Corixoidea

Volgende On the last page some international names of the Real- and the Lesser Water Boatman.



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All pictures on this site have been made by G.H. Visser (Almelo, Holland), unless otherwise mentioned. All rights remain with him. These photo's may not be used for other then strictly private uses. In case you want to use them for purposes including third parties, you MUST request permission, by e-mailing the author. I encourage especially those wanting to use the pictures for nature-expositions or other educative targets.
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rev 22-04-2011


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