![]() Accessed īoukal DS, Boukal M, Fikáček M, Hájek J, Klečka J, Skalick ý S, Šťastný J, Trávníček D (2007) Catalogue of water beetles of the Czech Republic (Coleoptera: Sphaeriusidae, Gyrinidae, Haliplidae, Noteridae, Hygrobiidae, Dytiscidae, Helophoridae, Georissidae, Hydrochidae, Spercheidae, Hydrophilidae, Hydraenidae, Scirtidae, Elmidae, Dryopidae, Limnichidae, Heteroceridae, Psephenidae). A comprehensive method to assess European streams using benthic macroinvertebrates developed for the purpose of the Water Framework Directive. How?! Why?! We get answers.AQEM Consortium (2002) Manual for the application of the AQEM system. Once entering the aquatic state they no longer fly.Ĭrystal Maier - Collections Manager of Insects at The Field Museum - spent a month in New Zealand, going from stream to stream in search of beetles that spend their entire lives underwater. A newly emerged beetle may fly a significant distance before entering the stream. The pupae crawl out of the water, breathes air and pass through a pupal stage in holes along the streams banks. The larvae moult up to 8 times before they are ready to pupate. The females lay their eggs in crevices in solid objects on the bottom of the stream. These can be retracted for protection, or rhythmically expanded and contracted to increase oxygen flow.Īdult riffle beetles mate in the water. Filamentous gills emerge from under the last (9th) abdominal segment. The antennae and mouthparts are shorter than the head. They are elongated and are up to 16 mm long (most less than 8), and have a head and 3 pairs of legs visible from above. Riffle beetle larvae are strictly aquatic. If the bubble becomes too small to keep up with metabolic demands and the insect must renew the entire bubble by returning to the water's surface. When the bubble's surface area decreases, its rate of gas exchange also decreases. Unfortunately, the size of the bubble shrinks over time as nitrogen slowly diffuses out into the water. An insect can remain underwater as long as the volume of oxygen diffusing into the bubble is greater than or equal to the volume of oxygen consumed by the insect. The larger the surface area of the bubble, the more efficiently this system works. In effect, the bubble acts as a "physical gill" - replenishing its supply of oxygen through the physics of passive diffusion. The air bubble provides an insect with a supply of oxygen, due to a unique physical property of absorbing oxygen molecules that are dissolved in the surrounding water. The under the last (9th) abdominal segment (bubble) covers the insect spiracles (valve-like openings in the exoskeleton) so the insect can "breathe" air from the bubble while submerged. These hairs trap a layer of air, called a plastron, on the surface of the body, and the beetle uses this for gas exchange. The adults are aquatic and have the ability to live underwater because the ventral surface of their body is covered with an extremely dense layer of tiny, specialised, hydrophobic hairs. The slender antennae are 11 segmented and without a distinct club. They have relatively long legs with tarsal claws. The adult beetles are small (1-8 mm long), dark, elongate and sclerotised (hard body). They feed on decayed plant material and algae. Riffle beetles are usually live in cool, rapid streams. ![]() The Elminae are far more abundant and diverse than the Larainae. The family Elmidae is divided into two subfamilies: Elminae and Larainae. Riffle beetles are small aquatic beetles in the family Elmidae of which there are about 1400 species known worldwide, with many more undescribed. Common name: Riffle beetles, Water beetles
0 Comments
Leave a Reply. |