Elmidae
Macronychus quadrituberculatus, From: GG Jacobson, " The beetles of Russia and Western Europe " (St. Petersburg 1905-15 ), T. 42
The Elmidae are a freshwater (aquatic ) live globally widespread beetle family of Polyphaga. They include 1330 described species (as of 2008).
Features
The beetles are small, between a little less than a millimeter to ten millimeters long, most species between two and three millimeters. Your body outline is oval in general, sometimes elongated with parallel sides of the body. The head is somewhat protected retracted into the prothorax (usually up to the eyes) and from below by a semi-circular projection of the Prosternums, the mouthparts are directed downwards, never pre-stretched forward. The antennas are usually elfgliedrig ( rarely reduced to up to seven members ) and culled simply filiform or slightly towards the tip. (But come in non-European Branches also at the Elmidae sensor lobes ago) This is the main external distinguishing feature of the European species of very similar family Dryopidae, in mostly all antennal segments from the third to redrafted into a spindle-shaped, semi- toothed lobe are. The pronotum is the upper forward curved, keeled on the sides and contributes to many genera and species characteristic keels or gutters on the top, where the presence and shape is very important in the identification of species. The elytra may carry such keels. The elytra run at rest usually oval pointed to the rear and carry longitudinal rows of pits point. Most species bear full, membranous hind wings and are capable of flight, but there occur a few species with shorter wings. The most important difference to the family Dryopidae is the shape of the female genitalia. These are not out, as in the Dryopidae to an ovipositor, but usually shorter and soft sclerotized with paired projections ( often called spin stylus, but probably sensory organs ). Dis male genitalia consist of three parts with a central and two lateral parameres aedeagus, they are usually essential in the identification of species.
Characteristic of the families Elmidae and Dryopidae is the construction of the legs. These are designed always strong and as staple legs, the beetles have no buoyancy. At the five -membered tarsi of the last term is increased remarkably, taken together, often longer than the other four members. At its peak, there are two enlarged, pointed claws. This has the animals introduced its German name hooks or claws beetles. The legs are greatly enlarged in some non-European genera, the leg length may in East Asian species of the genus Ancyronyx exceed the body length. This has these beetles the popular name "spider beetle" introduced.
The Elmidae are usually colored solid black. Some species show a metallic blue sheen. In many ways ( not in Europe ) is a distinctive, yellow color drawing of spots and bands present, which is interpreted as a warning costume. Few species have yellow-brown or reddish color.
Characteristic of the Elmidae and Dryopidae is their plastron respiration. For this, the underside including legs ( Elminae ) or the entire body surface ( Larainae ) are occupied with an extraordinarily dense stocking very short, hooked hairs and non-wettable by wax coatings. The hair can be so small that they can only be resolved in the electron microscope. Under water, the animals carry an air bubble under the elytra with it. The coated portion is covered with hair by an air film, which is in communication with the reservoir, wherein it looks, when viewed in water silvery white. From the air coating can out and oxygen diffuse and so renew the air supply (which is why the animals are dependent on oxygen-rich water ) carbon dioxide. Since carbon dioxide is considerably more soluble in water than oxygen, its partial pressure decreases by air coating, this would normally be the bladder become smaller and eventually exhausted to the air reservoir. Due to the special design of the integument, the bladder can, however, remain under pressure ( it is supported by the bristles quasi ). Therefore, the beetles do not need to renew such as all diving beetles ( Dytiscidae ), the air reservoir to the surface, but can their whole Imaginalleben remain submerged throughout. In some species the Larainae the plastron is less fully developed, this bear under water a larger bubble with and sometimes need to renew their air supply.
Larvae
The stretched, up to 16 mm long larvae are like the Imagines well sclerotized. They are usually parallel to each other and elongated, in some species (e.g., of the genus Elmis ) of the body is laterally widened in sheet form, so as to form a triangular cross-section body. The abgeplattten larvae usually live on the surface of stones, those more likely to be buried with a round body cross-section or in the pore system of the river bed. They carry three, usually quite short pairs of legs and can not swim like the Imagines. They breathe through gills on their abdomen end hoses, which are usually ausstülp and retractable and called by an " operculum " gill cover protected, wearing a pair of claws and thus shows its origin as abdominal limb pair.
Life cycle
All Elmidae lay their eggs in the water and live as larvae in water. The imagos are predominantly water alive. The Larainae there are some species that are occasionally encountered as Imagines permanently or out of water. But this then always live near water, usually even in the area of the water surface.
The Elmidae lay their eggs, where previously known singly or in small Located cemented from the surface of rocks or wood in the water. The hatching after 5 to 15 days depending on the type larvae go through five to eight larval stages. The larvae usually sit on the surface of stones or other hard substrate and scrape the organic nursery ( periphyton ) from algae and other organisms on the surface. Some species are specialized to particular substrates, such as tufa ( travertine ), which precipitates from kalkgesättigtem brook or spring water. These can be so encrusted with lime as imagines that they look like little stones. A few species, such as the North American Lara avara, feed on submerged woody debris in which they dig long superficial galleries. In this low-energy food substrate they need four to six years to develop to the imago, the imaginal beetles then lives only about three weeks. Some other species have been kept alive in the laboratory and imagines but up to ten years. But most Elmidenarten have a one-year development cycle ( univoltine or monovoltin ). Sometimes northern populations of the same species take longer to develop.
All kinds pupate out of the water. For this purpose, they dig a small cavity in the soil or under moss beds near the shore, some species wait to just the summer sinking water levels drop and pupate in the low-tide water bed. Others have Tracheenblasen extensible, enabling them to rise to the water surface and can be anywhere drifting ashore. The dolls wear two long and stiff thread-like appendages on the pronotum, and usually two pairs of hooks on the back end. The hatching beetles normally do not run directly to the water, but lead before a flight through dispersion. You acknowledge waters at the reflection properties, as is clear from erroneously on car paint or other surfaces landed properties with similar individuals. Flying individuals of almost all species can be caught with window traps. If a suitable waters reached, diving beetles under. You leave at least in the subfamily Elminae the water never voluntarily and can no longer automatically go into hiding when they were dried out normally.
Way of life
Imaginale Elmidae feed as well as the larvae of algae and other detritus, rarely of living macrophytes. Most species live in flowing water, just pull calmer waters before. A few species live in the area of the shoreline amphibious, other waves in the area of lakes. Also types of stagnant water are mostly dependent on water movements and do not occur in deeper water layers, the maximum water depth is reached about ten meters in a few lakes. Most species are flow specialists and prefer fast flowing waters.
Within the family, there are some species with special adaptations. Thus, there are specialized types, for example in thermal springs. Very few species are subterranean waters specialized ( stygobiont ) throughout the Palearctic so far, for example, only a single species, which was found in Morocco. In flowing waters, they come from the source creek in large flows, the average number of species increases with the size of waters. Also to the south, the number of species is increasing both in Europe and worldwide. Within the tropical rivers of all kinds are colonized diverse. Although most types of hard substrates preferable as stones, there is also fine sand and other specialized types substrates.
Elmidae and their larvae are prey of fish. Their share in the intestinal contents, however, is usually less than its share of individuals in benthic invertebrates, so that their importance as fish food organisms is rather low. While some North American species were spurned with yellow warning drawing of predators in the food choice experiment, the European species are eaten by trout, for example, without hesitation.
Elmidae deemed pointer - organisms for good water quality, many are indicator species with low saprobic index within the Saprobiensystems, ie pointer for organically unpolluted waters. In moderately organically polluted waters some species can survive when the flow is fast enough. A number of species are habitat specialists, such as on -tufa or dead wood, these types are used as an indicator species of the riverine typing, some species are indicator species of good or very good water quality in the European assessment procedure PERLODES
System
The Elmidae were formerly often performed as a subfamily of closely related with them Dryopidae, both morphologically very similar families the German name " claws beetle" or " bug hooks " are used. Scientific synonyms for the family name Elmidae are, inter alia Helmidae, Elminthidae and Limniidae. The name of the family is derived from the genus Elmis Latreille, 1802. Meaning and origin of this name is unknown. The monophyly of the family has not been tested to date, their relationship to the Dryopidae and a number of other families ( Heteroceridae, Helocharididae ) is not been definitively
The Elmidae are usually classified into the superfamily Byrrhoidae, occasionally with each other probably more closely related aquatic families of this superfamily in its own superfamily Dryopoidea, which would then be the sister taxon Byrrhoidea. They are divided into two subfamilies, the Larainae (synonyms: Larinae, Potamophilinae ) and the Elminae.
The following list contains the 54 European species of the Elmidae for " Fauna Europaea " (2007):
Subfamily Elminae
- Mulsant & Rey 1872 Dupophilus brevis
- Elmis Aenea (Müller 1806)
- Elmis Bosnica Zaitzev 1908 Elmis Bosnica Bosnica Zaitzev 1908
- Elmis Bosnica tenuis Berthélemy 1979
- Elmis maugetii fossulata ( Kuwert 1890)
- Elmis maugetii maugetii Latreille 1798
- Elmis syriaca zoufali Reitter 1910
- Limnius perrisi carinatus ( Pérez- Arcas 1865)
- Limnius perrisi perrisi ( Dufour 1843)
- Limnius sulcipennis damryi Fairmaire 1881
- Limnius sulcipennis sulcipennis Fairmaire 1881
- Oulimnius tuberculatus perezi ( Sharp 1872)
- Oulimnius tuberculatus tuberculatus (Müller 1806)
Subfamily Larainae
- Potamophilus acuminatus (Fabricius, 1792)