Smooth ball float

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Smooth ball float
Hyphydrus ovatus (Linné, 1761) .jpg

Smooth ball float ( Hyphydrus ovatus )

Systematics
Superclass : Six-footed (Hexapoda)
Class : Insects (Insecta)
Order : Beetle (Coleoptera)
Family : Swimming beetles (Dytiscidae)
Genre : Hyphydrus
Type : Smooth ball float
Scientific name
Hyphydrus ovatus
( Linnaeus , 1761)

The smooth spherical swimmer ( Hyphydrus ovatus ) is a beetle from the family of swimming beetles (Dytiscidae).

features

The beetles reach a body length of 4 to 5.3 millimeters. They are uniformly rust-red, but the wing covers are mostly brown to brownish-black in color, except for the edge. Compared to other swimming beetles, the body shape is very broad, rounded oval and high, almost spherical on top. The underside is also curved outwards. Because of its size, shape and color, the smooth ball float is sometimes also called "cherry stone".

The antennae are short and narrow. Both the lip stylus and the mandibular stylus have a thickened end link that is much longer than the base link. The back shield ( scutellum ) is missing in this beetle.

The tarsi members of the first and second pair of legs have small suction cups on the underside that prevent them from sliding off the substrate. The rails ( tibia ) and tarsi of the rear pair of legs are studded with long bristles so that the legs can serve as paddles and enable fast swimming.

Gender dimorphism

The dimorphism between the two sexes is not apparent at first glance. Using morphometric methods, however, it was found that the males are usually larger than the females, their wings are longer and their heads are wider. It is assumed that these gender differences are due to a selection mechanism in which the males have to compete against other males, since during the summer months there are usually significantly fewer females of the ball swimmer than males. The males can also be distinguished from the females by their shiny, densely dotted, but hairless elytra, while in the female they have a silky shimmer and appear rather dull and are only individually dotted.

larva

The larva, which is up to 1.5 centimeters long and robustly built, has whitish horizontal stripes on its brown body. The long frontal horn of the larva is striking. Studies have shown that this nasal has mechanoreceptors at the tip , which act as tactile sensory organs , making it easier to track down prey in the sludge and between plant remains. The part of this appendage that is close to the mouth limbs bears small teeth made of chitin , which are used to hold the prey in place. With the help of the mandibles , which are specially deflected in these beetle larvae, worms and insect larvae are pressed from below against this toothed appendix , which is reminiscent of the upper jaw of the vertebrate animals , and thus caught.

Occurrence

The Smooth Kugelschwimmer is a Palearctic species and occurs all over Europe, including in the north, with the exception of Northern Norway , Swedish Lapland and northern Finland . In the east the distribution area extends to Asia Minor and in Siberia to Lake Baikal .

It prefers standing water or areas with little current in small flowing water. Like almost all swimming beetles, it can fly well and spreads to different biotopes such as garden ponds and newly colonized bodies of water such as the lakes and ponds of recultivated areas of open- cast brown coal mining . Since both the larvae and the adults are predatory and carnivorous , these water beetles are dependent on organic communities with an already well-established food chain . They are therefore looking for small, plant-rich bodies of water that have existed for a long time and are usually found in forest ponds or oxbow lakes. In contrast to many other swimming beetles, the smooth spherical swimmer is common and not endangered anywhere in its range.

Way of life

The beetles are predatory. The flight time is all year round. As with most swimming beetle species, overwintering takes place as an imago. When diving, the ball swimmer takes a supply of air with it, which it stores in an air bubble. This air bubble is renewed from time to time when the beetle protrudes from the surface of the water with the tip of the abdomen. Most other swimming beetle species, however, store the air supply under their wings. Little is known about the mating behavior of these water beetles.

The beetles lay their eggs on aquatic plants in spring, larval development is in May and June. The larva usually runs with its six slightly hairy legs over the bottom of the water, but can also swim a few centimeters to the surface to take a breath. It lives predatory between the aquatic plants, where it searches in the detritus for the worms, mosquito larvae and small crustaceans that live there .

The three larval stages of the smooth spherical swimmer have slightly different ways of life. The young larva in the first instar stays in the upper part of the aquatic plants, where it does not have far to the water surface to breathe. There it eats larvae of crustaceans floating by in the plankton and small insect larvae. In the second larval stage, the ball swimmers hunt deeper in the water and prey on larger animals, while the third larval stage shows the typical walking on the ground in the root zone of the plants. There are mud tube worms and midge larvae to capture.

Taxonomy and systematics

Carl von Linné called the beetle Dytiscus ovatus when it was first described in 1761 . The specific epithet ovatus means "egg-shaped" and describes the body shape of the water beetle, known in German as a ball float. The smooth ball float was described again by Johann Christian Fabricius in 1777 under the name Dytiscus gibbus ; from 1832 it was called Hyphydrus fabricii . In 1856 a separate genus Actobaena was established for this swimming beetle. According to the priority rules for the naming of living beings, it got the original species name ovatus again after its return to the genus Hyphydrus . It was not until 1928 that Bertrand attributed the larva to the smooth spherical swimmer.

The smooth spherical swimmer , like its relative, the six-spotted dwarf swimmer ( Hydroporus palustris ), belongs to the subfamily Hydroporinae , which was described by Aube in 1836, within the sea beetle family . Within this subfamily, the tribe Hyphydrini was established, which includes ten other species of swimming beetles in addition to the genus Hyphydrus . The smooth spherical swimmer is the type of this tribe. In Europe there are three other types of Hyphydrus , namely Hyphydrus anatolicus , Hyphydrus aubei and Hyphydrus maculatus .

supporting documents

Individual evidence

  1. ^ A b c Carl Gustav Calwer: Beetle Book. Natural history of the European beetles. For hand use by collectors. Fourth edition, ed. by G. Jäger, G. Thienemann Verlag, Stuttgart 1876, p. 77 facsimile of the page
  2. Wasserkäfer ( Memento from October 14, 2010 in the Internet Archive ) on the website of the Munich Water Management Authority
  3. Torsten Rossmann, Cameron Tropea: Bionics: current research results in natural science, engineering and humanities. Springer, Berlin 2007, p. 101 ISBN 3-540-21890-4
  4. Picture of the spherical float on the foreleg, the tarsal limbs equipped with a suction device are visible
  5. Steven A. Juliano: Quantitative Analysis of Sexual Dimorphism and Sex Ratio in Hyphydrus ovatus (Coleoptera: Dytiscidae). Ecography, 15, 3, pp. 308–313, 1992 full text ( Memento from June 22, 2010 in the Internet Archive ) (PDF, English)
  6. Pictures of the larva of the ball swimmer at Hydro-Kosmos
  7. a b Henning Friis, Thomas Bauer and Oliver Betz: An insect larva with a 'pig-snout': structure and function of the nasal of Hyphydrus ovatus L. (1763) (Coleoptera: Dytiscidae). Journal of Zoology, 261, 1, pp. 59-68, Cambridge University Press, 2003 doi : 10.1017 / S0952836903003972
  8. Wolfram Pflug: Lignite mining and recultivation. Springer, Berlin 1998, p. 394 ISBN 3-54060-092-2
  9. Picture of a female of the smooth spherical swimmer with air bubble in Microcosmos
  10. Anders N. Nilsson, Mogens Holmen: The aquatic Adephaga (Coleoptera) of Fennoscandia and Denmark. Volume 2, Dyticscidae: Dytiscidea v. 2. Fauna Entomologica Scandinavica, Volume 32, Brill Academic Publishing, 1995, p. 39 ISBN 9-00410-456-9

literature

  • Heiko Bellmann: Insects . 2nd edition, Steinbach's natural guide, Eugen Ulmer Verlag, 2010, page 92 ISBN 978-3-8001-5931-4
  • Heiko Bellmann: The new cosmos insect guide. Franckh-Kosmos, Stuttgart 2009, page 146 ISBN 978-3-440-11924-2

Web links

Commons : Smooth Kugelschwimmer ( Hyphydrus ovatus )  - Collection of images, videos, and audio files