Photo of the day (54): eggs of Ancylus fluviatilis

Adults of freshwater gastropod Ancylus fluviatilis have a cap-like shell. But shells of its embryos are a bit different. You can find eggs of Ancylus fluviatilis in spring and in early summer on stones in streams. I found these eggs in northern Bohemia in June.

Eggs are laid in capsules. There are 9-12 eggs in each capsule.

egg capsules of Ancylus fluviatilisThere can be seen foot, eyes and tentacles under stereo microscope easily in this state of development. There are also ribs on the shell, that resemble ribs of some Patella species to me. I have taken the photo in situ.

eggs of Ancylus fluvitilisI found no images of eggs of Ancylus fluviatilis for comparison on the internet after a brief search.


Species summary for Ancylus fluviatilis. AnimalBase, last change 26 October 2013, accessed 8 July 2016.

Streit B. (1976). Energy flow in four different field populations of Ancylus fluviatilis (Gastropoda-Basommatophora). Oecologia, 22(3): 261-273.

Photo of the day (45): water mite on a Helisoma anceps

Water mites is a group of about 5000 species of mites. Scientific name of them is Hydrachnidia or Hydrachnidia or Hydracarina or Hydrachnellae. They are usually very small and this is one of them. I found it in my freshwater aquarium on Helisoma anceps. It is so small that I had to use lens to verify, that the small dot on the shell is a water mite. water mite on Helisoma ancepsThe water mite is in the centre of the photo. It is on the mantle edge near the aperture. Detail cropped from the previous photo: water miteYou can compare the size of the water mite with two Ferrissia fragilis snails on the top of the shell of Helisoma anceps. Both of these freshwater snail species are of North American origin and both belong to the same family Planorbidae. Ferrisia fragilis can reach 3.2 mm maximum shell length, but I think my snails are a bit smaller. The water mite is about 0.5 mm or smaller. It was actively moving on the snail. The dot in the centre of the photo is the water mite: water mite on Helisoma anceps with Ferrissia fragilisI do not know the origin of the water mite. I found only one in my aquarium meantime.

Photo of the day (44): eggs of Helisoma anceps

Helisoma anceps lays eggs in gelatinous translucent clusters.

This cluster is taken shortly after eggs laying. I think it is about the second or the third day. There are seen five small dot-like embryos:

eggs of Helisoma ancepsAnother cluster of eggs contains six more developed embryos:

eggs of Helisoma ancepsThis is yet another cluster of nine eggs shortly before hatching. Eight hours later all snail were hatched. The length of this whole cluster is 4 mm and it is attached to a stem of a common freshwater plant from the genus Hydrocotyle. There are seen shells of all nine embryos and there are seen heads with eyes of three snails in the first row:

eggs of Helisoma anceps

Photo of the day (19): Planorbis planorbis

Planorbis planorbis is very common freshwater snail in western part of Eurasia.

It holds its shell upside down and its shell is sinistral as in all other Planorbidae. Apertural view of a shell with a live snail in it:


Dorsal view of a snail and umbilical view of its shell:


Apical view of the shell and foot of a snail. The sun was shining brightly on the snail so there are some internal anatomical features visible. (This one photo is unaltered, while there are adjusted levels on other photos.)

If I undersnad it correctly then there is clearly visible renal vein as a thick red-brown line inside the last whorl. The renal vein leads to the kidney (that starts with renal tube). I think, there is also air chamber visible. I think, that the dark line insie whorls is inestine, that is connected to the stomach (the most dark place in the penultimate whorl):


There is visible a mantle border on the photo:


A similar photo:



There are anatomical images of the genus Gyraulus by Meier-Brook available. These images are also reproduced in other malacological books because it shows the whole anatomy of the animal (removed from the shell).

Meier-Brook C. 1983 “Taxonomic studies on Gyraulus (Gastropoda: Planorbidae)”. Malacologia 24(1-2): 1-113. page 30.

Some anatomical images exactly of Planorbis planorbis were made by Baker, but they are not clearly undestandable without detailed anatomical knowledge.

Baker F. C. 1945 The molluscan family Planorbidae. The University of Illinois Press, Urbana.

Photo of the day (15): Planorbarius corneus

Planorbarius corneus (Linnaeus, 1758) is a freshwater snail from the family Planorbidae. All Planorbidae have hemoglobin in its respiratory system – in its blood. It is the same respiratory protein that transport oxygen in human’s blood. Albino specimen are quite popular in aquaria, but albinos occur in nature sometimes too. When a planorbid snail is an albino snail, then the color of its hemoglobin is clearly visible and the whole snail is in bright red color.

Photo of albino Planorbarius corneus on human hand:



Baker F. C. 1945: The molluscan family Planorbidae. The University of Illinois Press, Urbana. page 13.

Photo of the day (14): Helisoma anceps

Helisoma anceps, synonym: Planorbella anceps, is a freshwater snail from family Planorbidae. It is native to North America. It is sometimes kept in aquaria in Europe.

Planorbidae are breathing free air and their breathing pore is called pneumostome (it is the same as in land snails). The pneumostome is on the right side of the body, but it is close to the median line (= to the center).

The very large pneumostome is visible on this photo of juvenile Helisoma anceps:


Additionally Planorbidae have another breathing organ, that is used for breathing underwater. It is called pseudobranch and it is placed on the left side of the body. It evolved by extending of the anal region and therefore anus is always close to the pseudobranch. The pad-like pseudobranch of an adult Helisoma anceps is about 2 mm wide and 1 mm high. You can see the pseudobranch easily, if you will watch to the left side of your planorbid snails crawling in the water.

The following two photos shows the extended pseudobranch of the same specimen of juvenile Helisoma anceps:



Baker F. C. 1945: The molluscan family Planorbidae. The University of Illinois Press, Urbana. page 3 and page 126. Plate 23, figure 4.

Photo of the day (8): Anisus leucostoma

Anisus leucostoma is planorbid freshwater snail with Palearctic distribution. It occurs in standing water such as periodic marshes.


Its shell is flattened and it has dimensions of shell about 6.5 mm × 1.4 mm. Therefore it is not easy to get its sharp photo with such dimensions and moreover in water. Addtionally its brown shell can be covered with some coating, that gives to the shell very dark appearance.


Anisus leucostoma crawling below the water surface in natural light conditions. There is also visible for example mantle edge on the lip of the aperture:



Comparison with larva of Culex:


Anisus leucostoma extended from its shell:


There is periphyton attached on the shell:


Under bright artificial lighting and with white balance there is visible, that the periphyton consist of green algae: