Hygrobia

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Hygrobia
Hygrobia hermanni

Hygrobia hermanni

Systematics
Class : Insects (Insecta)
Order : Beetle (Coleoptera)
Subordination : Adephaga
Superfamily : Dytiscoidea
Family : Damp beetle
Genre : Hygrobia
Scientific name of the  family
Hygrobiidae
Régimbart , 1878
Scientific name of the  genus
Hygrobia
Latreille , 1804

Hygrobia is a genus of beetles whose larvae and adults live aquatically (in water). It is the only genus of the, thus monotypical , family Hygrobiidae . The family, or the only European species, Hygrobia hermanni , is occasionally referred to by the common names damp beetles or mud swimmers. In English-speaking countries like Australia (where most of the species live) they are called screech beetles (translated: " screech beetles ", after the sound produced by stridulation , sometimes also squeak beetles ).

features

The beetles are about 8.5 to 10 millimeters long and are yellow, reddish or black colored or drawn. The surface, especially the pronotum and elytra, is clearly dotted, the spaces between the dots are finely meshed. They have a short oval, above all on the ventral side (ventral), highly arched, streamlined body with a protruding head that is not retracted into the pronotum and is narrower than the pronotum . The large complex eyes protruding clearly from the contour of the head are striking. The antennae consist of eleven segments, the base limb (scapus) is elongated, the other limbs have short thorns. The simply built mandibles are two-pointed, there is neither a chewing surface (mola) nor rows of hairs. The lower jaw buttons are four-part and the lip buttons are three-part.

The pronotum is short and wide and narrows towards the front, with a row of hairs on the front edge. The rear edge of the first trunk segment has a long extension, which is pointed at the end and which can be inserted into a pit in the middle and rear chest. The legs are thin, the rear rails widened somewhat flat, and have webbed hair on the rails (tibia) and foot members (tarsi) of all pairs of legs. The hips of the hind legs are transverse and immobile, fused in the middle. The plate-shaped extensions of the coxes typical of the family of water treaders (Haliplidae), however, are either completely absent or greatly reduced. All rails have two spurs at the top. The membranous hind wings, which are hidden under the wing covers when at rest, are well developed, the beetles are capable of flight.

At the abdomen six are abdominal side sternites visible, the third and fourth are fused together. The stridulation apparatus used to generate sounds consists of the edge of the wing tip and the seventh sternite, which can be rubbed against each other.

The males differ from the females in that the first three tarsi members of the front and middle pairs of legs are widened and that they have suction cups made of widened hair on their underside. The difference between the wet beetles and the swimming beetles is that the former have an elongated, transversely divided plate on the metasternum .

Larvae

Hygrobia has three larval stages. The third instar larvae reach a body length of 18 millimeters. They are brown in color with yellow or whitish markings. The head and prothorax are very large in relation to the rest of the body, in the first larval stage the head is almost as large as the rest of the body. The overall thorax is almost as long, or even longer, than the abdomen. The large, flattened head is slightly rounded on the sides, the mouthparts point forward (prognath). A broad sclerite, the gula, is formed on the underside of the head (in contrast to the Dytiscidae larvae). The head has six larval eyes (stemmata), the antennae are four-limbed, with the fourth limb being very small. The mandibles of the mouthparts are very large and crescent-shaped (falciform) with a cutting edge that lacks the internal channel in the Dytiscid larvae. The maxilla lacks the cardo and both chewings ( Galea and Lacinia ), the maxillary palpus is tripartite. The submentum of the labium is fused behind with the gula, the labial palpus is two-part. The long, six-limbed legs sit on the trunk, the tarsi each have two claws. Webbed hairs are only formed on the tarsi and tibia in the first two larval stages. Seven segments can be seen on the abdomen. The eighth segment is very small, it has a thread-like extension that is reminiscent of a terminal filum, such an extension is absent in all other aquatic Adephaga (Hydradephaga) larvae. At the rear end there are paired appendages, the urogomphi , of variable length; in the European species, in the third larval stage, they are shorter than the last abdominal segment. The larvae are characterized by tubular, tufted gills that are located at the base of the hips (coxae) of all three pairs of legs and on the first abdomen segment. Hygrobia larvae are the only larvae of the Dytiscoidea with gills.

Way of life

The animals live in water, in standing water, especially ponds. They tend to swim slowly in a zigzag style, as they take turns rowing their legs. Most of the time, however, they tend to move forward crawling along the edge or bottom of the water. They are predatory and hunt annelworms and diptera larvae on the bottom of stagnant water covered with mud or dead plant material. The beetles row to move. They have to surface occasionally (about every 30 minutes) to take in oxygen, which is stored under the deck wings. They can fly and are occasionally attracted by artificial light at night. They can make noises by rubbing the abdomen and wings together. The eggs are laid in a gelatinous shell on aquatic plants .

The larvae also live predatory, in the same habitat as the adults . They don't have to come up to breathe, however, as they breathe through their gills. They pupate on land in damp sand and mud.

Systematics

The Hygrobiidae form, together with the families Dytiscidae , Aspidytidae and Amphizoidae, the superfamily Dytiscoidea within the Adephaga . While this grouping is considered to be well secured, its exact sister group relationship is still unclear. A basic position was proposed, with the other families as a sister group, or a sister group relationship with the Dytiscidae, which u. a. is supported by the morphology of the larvae. A phylogenomic study sees the genus Hygrobia within the Dytiscidae (which would make them paraphyletic), but the statistical reliability of this result is very low.

The family name Hygrobiidae, derived from the genus name Hygrobia , was introduced by Latreille in 1804 as "Hygriobia"; the changed spelling was established by the ICZN in 1954. Some authors are of the opinion that since the family name was not included in the change, the name Paelobiidae, based on the synonymous name Paelobius Schönherr, 1808, should have priority for the family . This name is occasionally used in scientific literature, but mostly, as a forgotten name, is considered a synonym of Hygrobiidae.

species

The genus Hygrobia has a disjoint distribution, with one species in the Western Palearctic, one in China and four in Australia. Such a distribution picture is interpreted as a relic occurrence of a once more widespread group, whose other representatives have become extinct. According to estimates using the molecular clock method , the genus could be around 184 million years old, older than the splitting of the supercontinent Pangea .

Sources and literature

  • Konrad Dettner: Hygrobiidae. In Rolf G. Beutel, Richard AB Leschen: Handbuch der Zoologie - Coleoptera, Beetles, Volume 1: Morphology and Systematics (Archostemata, Adephaga, Myxophaga, Polyphaga partim). 1st edition. de Gruyter, 2005, ISBN 3-11-017130-9 . Second, revised edition 2016, ISBN 978-3-11-038622-6 .

Individual evidence

  1. ↑ Remigius Geiser (editor): Red list of beetles (Coleoptera). In: Margret Binot, Rüdiger Bless, Peter Boye, Horst Gruttke, Peter Pretscher: Red List of Endangered Animals in Germany. Series of publications for landscape management and nature conservation 55. Bonn-Bad Godesberg (Federal Agency for Nature Conservation), 1998. ISBN 3-89624-110-9
  2. ↑ Feuchtkäfer Lexikon der Biologie, www.spektrum.de, 1999
  3. ↑ Heinz Freude: 2nd family Hygrobiidae (mud swimmers) in Heinz Freude, Karl Wilhelm Harde, Gustav Adolf Lohse: Die Käfer Mitteleuropas. Volume 3 Adephaga 2, Palpicornia, Histeroidea, Staphylinoidea 1. Goecke and Evers Verlag, Krefeld 1971. ISBN 3-87263-015-6
  4. ↑ Hygrobiidae, Hygrobia. Identification and Ecology of Australian Freshwater Invertebrates. An interactive guide. Murray Darling Freshwater Research Center, 2013.
  5. ↑ a b Yves Alarie, Rolf G. Beutel, Chris HS Watts (2004): Larval morphology of three species of Hygrobiidae (Coleoptera: Adephaga: Dytiscoidea) with phylogenetic considerations. European Journal of Entomology 101: 293-311.
  6. ↑ Ignacio Ribera, James E. Hogan, Alfried P. Vogler (2002): Phylogeny of Hydradephagan Water Beetles Inferred from 18S rRNA Sequences. Molecular Phylogenetics and Evolution 23 (1): 43-62. doi: 10.1006 / mpev.2001.1080
  7. ↑ Mariano C. Michat, Yves Alarie, Lars Hendrich (2014): Description of the third instar of Hygrobia nigra (Clark, 1862) (Coleoptera: Paelobiidae), with a key for the identification of mature larvae of Hygrobia Latreille, 1804 and phylogenetic analysis. Zootaxa 3827 (3): 318-330.
  8. ↑ Oliver Hawlitschek, Lars Hendrich, Michael Balke (2012): Molecular phylogeny of the squeak beetles, a family with disjunct Palearctic-Australian range. Molecular Phylogenetics and Evolution 62 (1): 550-554. doi: 10.1016 / j.ympev.2011.09.015
  9. ↑ Erhan G. Taşar et al. (2012): A Good Sample to Concurrent Fauna: Study on Aquatic Coleoptera Fauna (Adephaga and Polyphaga) of Lake Van Basin (Turkey), with some Zoogeographic Remarks. Journal of the Entomological Research Society 14 (2): 27-37.

Web links

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