Photo of the day (38): eggs of Physa acuta

Physa acuta (or Physella acuta according European malacologists) is a very common freshwater snail. It is non-indigenous in Europe, originally from the North America.

It can be often found in highly eutrophic water reservoirs such as ponds for intensive aquaculture with common carps like this one in the South Moravia:
pond 01
pond 02

Notice, that there are no wetland plants on banks.

There were many Physa acuta snails and many of its eggs on stones in the water. There are 7-50 eggs (Beran 1998) or 7-53 eggs (Glöer 2002) in gelatinous egg capsules. In-situ photo of eggs of Physa acuta (I have taken the stone out of water, of course.):
Eggs of Physa acutaEggs seems to be in very early development phase (probably less than 5 days old).


(in Czech) Beran L., 1998: Vodní měkkýši ČR. – Metodika Českého svazu ochránců přírody č. 17, Vlašim: ZO ČSOP Vlašim, 113 pp., page 83.

(in Czech) Beran L., 2002: Vodní měkkýši České republiky – rozšíření a jeho změny, stanoviště, šíření, ohrožení a ochrana, červený seznam. [Aquatic molluscs of the Czech Republic – distribution and its changes, habitats, dispersal, threat and protection, Red List]. – Sborník přírodovědného klubu v Uh. Hradišti, Supplementum 10, 258 pp., pages 197-198.

(in German) Glöer P. 2002: Die Süßwassergastropoden Nord- und Mitteleuropas. Die Tierwelt Deutschlands, ConchBooks, Hackenheim, 326 pp., ISBN 3-925919-60-0, page 238.

Further reading:

September 26, 2014: The Egg Masses of Freshwater Pulmonate Snails. The Blog of the FWGNA Project.

Perez, K. E. & Sandland G. (last change May 21, 2014, accessed November 1, 2014) Illustrations of common aquatic snail egg masses in Wisconsin. Key to Wisconsin Freshwater Snails.

Photo of the day (33): Physa fontinalis

Physa fontinalis is a widespread freshwater snail in Europe. It has a sinistral shell as all Physidae snails. A remarkable anatomical feature are finger-like lobes or tentacle-like lobes, that are extensions of the mantle and they partly cover the shell. I counted 7 lobed on the right front and 3 or 4 lobes near the apical part of the shell on the photographed snail. In comparison with Physa acuta, the Physa fontinalis has thin and translucent shell and a rounded apex.

Physa fontinalis