Macroplea mutica (Fabricius 1792) (Insecta: Chrysomelidae) 

Compiled by: Fritz Gosselck & Joachim Schmidt, Germany

1. Description / Ecological demands / Autecology

Macroplea mutica is a 6-7 mm long, straw-coloured chrysomelid beetle with long legs and antennas. It differs from its close relative M. pubipennis by only the shape of elytral apex and the male genitalia. It lives in sheltered inlets in shallow waters, at a depth range of 25-50 cm. M. mutica lives in brackish water but is also known from freshwater localities. In the Baltic Sea, this herbivorous beetle is trophically associated with submerged plants of the Baltic coast e.g. Ruppia ssp., Potamogeton pectinatus, Zannichellia palustris, Zostera marina, Myriophyllum spicatum. It lives underwater throughout its life cycle, but the details of its biology, especially in larval stages, are poorly known. The adult beetles crawl together, the smaller male "riding" on females' back.

2. Distribution

M. mutica is a halophile species, living on the coasts of Baltic Sea, Mediterranean, and Caspian Sea, known also from freshwater e.g. lake Balaton in Hungary. Similarly, there are also some freshwater records from Finland and Sweden. It is associated with saline lagoons on the Atlantic coast. M. mutica lives in inlets (Bodden) of the German and Polish coast. Its formerly known localities in Puck bay and the environs of Gdańsk have not been confirmed for several decades. The species seems to be very rare in the exposed coasts.

3. Importance

M. mutica is an example of a species highly connected to the biotope “submerged plants –phytal”, which is endangered by anthropogenic activities.

4. Status of threat

A very rare declining halophilous species. In Poland it may have become extinct or its populations are very much reduced (CR Critically Endangered). In Germany it has the status “Endangered” in both responsible lists. It is listed on the updated list of Latvian beetles (Coleoptera). In Finland and Sweden, no clear decline has been recorded and it has been evaluated as LC (Least Concern).

5. Threat factors

M. mutica is threatened by all activities destroying its habitat: increasing pollution of coastal waters, coastal constructions, harbours, and dredging. Also disturbance caused by boat traffic, changes in water quality as well as changes in vegetation due to eutrophication  (mainly expansion of reeds) are unfavourable to this species.

6. Conservation measures needed

Elimination or at least strong limitation of the above-mentioned factors would create the possibility of restitution and maintenance of Macroplea mutica in the Baltic Sea area.

Inspite of this, inventories are needed to find out the actual distribution of, and threats to, M. mutica in the Baltic Sea. More research on the ecology of the species is also needed. The most important known populations are already partly protected. Newly discovered sites should be protected as well and all harmful human activities should be prohibited there.

7. References:

Binot M., R. Bless, P. Boye, H. Gruttke & P. Pretscher 1998. Rote Liste gefährdeter Tiere Deutschlands. Schriftenreihe für Landschaftspflege und Naturschutz, 55, Kilda-Verlag: 1-434.

Kölsch G. & R. Suikat 2003. Zur Biologie der aquatischen Blattkäfergattung Macroplea ssp. (Colepotera, Chrysomelidae). (Kurzfassung). www.entomologentagung2003.uni-halle.de/pdf/sektion08.pdf

Merck T. & H. von Nordheim 1996. Rote Listen und Artenlisten der Tiere und Pflanzen des deutschen Küstenbereichs der Ostsee. - BfN, Bonn-Bad Godesberg, Schriftenreihe für Landschaftspflege und Naturschutz 48: 1-108.

Silfverberg H. 1987.  Mapping the Finnish Chrysomelidae (Coleoptera). I. Notulae Entomologicae 67: 5-16.

Warchałowski A. 1985. Chrysomelidae - Stonkowate (Insecta: Coleoptera). Część I (część ogólna oraz podrodziny: Donaciinae, Orsodacninae, Synetinae, Zeugophorinae i Criocerinae). Fauna Pol. 10: 1-373.

Zbigniew Głowaciński, Janusz Nowacki: Polish Red Data Book

www.fmnh.helsinki.fi/julkaisut/vuosikertomukset/2001/ltkm2001-fin-osa2.pdf In Finnish