Embryonic development of Bithynia tentaculata

Bithynia tentaculata is a well known freshwater snail from the family Bithyniidae. It occurs in the Palearctic. Females lay eggs and the development lasts few weeks depending on the water temperature. It hatch after 12-14 days at the temperature 25 °C (Cather & Verdonk 1974). I had temperature 26 °C in my aquarium, so my snails hatched out in the 12th day.

This is how they look like shortly before hatching:

Bithynia tentaculata eggsEggs are usually laid in two rows. There is seen a bit compressed shape of eggs, when you will look out from the side view:

Bithynia tentaculataIt will go though the cleavage, blastula, gastrula in the first two days. This very early development was studied by various scientists (Erlanger 1892, Van Dam 1986).

Day 1:

Bithynia tentaculata

Day 2:

Bithynia tentaculata

Day 3:

Bithynia tentaculata

Then it will form a radula, shell, nervous system, tentacles, ctenidium, heart, foot, snout and other organs. The shell is translucent, so if you would watch the embryo in the microscope, then there would be ctenidium and heart easily recognisable.

Day 4:

Bithynia tentaculata

Day 5:

Bithynia tentaculata

Day 6:

Bithynia tentaculata

Day 7:

Bithynia tentaculata

There is clearly visible a shell by naked eye since the seventh day.

Day 8:

Bithynia tentaculata

Eyes, foot, head and snout are clearly recognizable.

Day 9:

Bithynia tentaculata

Day 10:

Bithynia tentaculata

Tentacles are visible easily.

Day 11:

Bithynia tentaculata

Day 12 – hatching:

Bithynia tentaculata

The first hatched snails:

Bithynia tentaculata

The diameter of hatching snails is 1.2 mm and their weight is 0.25 mg (Negus 1998).

Day 13:

Bithynia tentaculataThere left only empty egg cases and incorrectly developed embryos in the 13th day.

So this is a brief insight how Bithynia tentaculata develops and how you can see it by naked eye or by magnifying lens. But it is a worth to use microscope.

When it will be lucky and if no predator will eat the juvenile snail, it will grow into a snail like this:

Bithynia tentaculataReferences

Cather J. N. & Verdonk N. H. (1974). “The development of Bithynia tentaculata (Prosobranchia, Gastropoda) after removal of the polar lobe“. Journal of embryology and experimental morphology, 31(2): 415-422.

Erlanger R. (1892). “Beiträge zur Entwicklungsgeschichte der Gastropoden”. Mittheilungen aus der Zoologischen Station zu Neapel 10: 376-404.  Plate 25-26.

Negus M. R. (1998). “A Life Table for the fresh water mollusc Bithynia tentaculata (L.)”. Journal of Biological Education, 32(1): 14-23, DOI:
10.1080/00219266.1998.9655588 abstract

Van Dam W. I. (1986). “Embryonic development of Bithynia tentaculata L. (Prosobranchia, Gastropoda). I. Cleavage”. Journal of Morphology 188(3): 289-302. DOI: 10.1002/jmor.1051880304 abstract

Photo of the day (42): Bithynia transsilvanica

Bithynia transsilvanica is an eastern European freshwater snail. This species was previously known as Bithynia troschelii.

Frontal view:

Bithynia transsilvanicaIt is very similar to Bithynia leachii. But Bithynia transsilvanica is larger and it can reach up to 11 mm in shell height. The first three photos are of the same specimen and the width of the shell is 8 mm and the height of the shell is 10 mm.

Lateral view:

Bithynia transsilvanicaView of a foot:

Bithynia transsilvanicaAnother photo is of a smaller Bithynia transsilvanica snail. The width of the shell is 7 mm and the height of the shell is 9 mm. There is seen its operculum, that is slightly pointed. It is an important identification feature:

Bithynia transsilvanicaReferences

Beran L. & Horsák M. (2009) “Distribution of Bithynia leachii (Sheppard, 1823) and Bithynia troschelii (Paasch, 1842) (Gastropoda: Bithyniidae) in the Czech Republic“. Malacologica Bohemoslovaca 8: 19-23.

Horsák M., Juřičková L. & Picka J. (2013) Měkkýši České a Slovenské republiky. Molluscs of the Czech and Slovak Republics. Kabourek, Zlín, 264 pp. (in Czech and English). pages 29 and 43.

Photo of the day (40): Bithynia leachii

Bithynia leachii is a widespread freshwater snail in Europe and it is a least concern species. This snail can live in natural and unpolluted wetlands only. In some areas, for example in the Czech Republic, it is critically endangered, because it inhabits a very limited area there.

There is seen on this frontal view, that the shell has very convex whorls and a very deep suture. This feature distinguish it from other Bithynia species.

Bithynia leachiiThe snail on the photo has the width of the shell 4.5 mm and the height of the shell is 5.5 mm. The snail of such size is adult already.

Right side view of the same snail:

Bithynia leachiiReferences

Beran L. & Horsák M. (2009) “Distribution of Bithynia leachii (Sheppard, 1823) and Bithynia troschelii (Paasch, 1842) (Gastropoda: Bithyniidae) in the Czech Republic“. Malacologica Bohemoslovaca 8: 19-23.

Vavrová L., Cianfanelli S., Prie V., Georgiev D. & Ghamizi M. (2010). “Bithynia leachii“. The IUCN Red List of Threatened Species. Version 2014.3. <www.iucnredlist.org>. Downloaded on 18 January 2015.