Photo of the day (53): Bolma rugosa

Bolma rugosa is a marine snail in the family Turbinidae. It is quite a big snail with a shell length up to 70 mm. Locality of my snail is Croatia. I have taken the following photos ex situ in the aquarium.

Bolma rugosaThose pointed structures bellow the shell are sensory structures, that are called epipodial tentacles. They are common structures in Vetigastropoda (one of main groups of gastropods).

Detail of epipodial tentacles:

epipodial tentacles of Bolma rugosaFoot view of Bolma rugosa:

Bolma rugosaFew other photos by other authors also shows epipodial tentacles on Bolma rugosa: at the top right corner of the photo.

or on the Circolo Attività Subacquee Chieri (Diving Club in Chieri, Italy) website at


Wanichanon C., Laimek P., Chitchulanon N., Suphamungmee W., Apisawetakan S., Linthong V., Sretarugsa P., Kruatrachue M., Upatham E. S., Poomtong T. & Sobhon P. (2004). Sensory receptors on cephalic and epipodial tentacles of Haliotis asinina Linnaeus. Journal of Shellfish Research, 23(4): 1097-1106.

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 (52): Tonna galea

Tonna galea is a large sea snail with worldwide distribution in temperate and in tropical seas. I have taken these photos in Croatia.

Tonna galea one of the largest snails in the Mediterranean Sea. Because of its size and because its beautiful shell it is exploited or over-exploited as a food source and as a tourist souvenir.

This species is protected by 1979 Berne Convention on the Conservation of European Wildlife and Natural Habitats as a strictly protected species. Therefore is is protected by law in many European countries. For example in Croatia it is protected since 2013 by law. It is forbidden to capture, kill, trade, import, export, and so on.

Despite its protection, its population size is thought to be greatly declined. Exporting of empty shells abroad is also not allowed. Let them for local residents and maybe they will use them in some nice way like this:

Tonna galea
With Haworthia sp.:

Tonna galea
With Aloe sp.:

Tonna galea

Doxa C. K., Sterioti A., Kentouri M. & Divanach P. (2011). “Encapsulated development of the marine gastropod Tonna galea (Linnaeus, 1758) in captivity“. Journal of Biological Research 16: 304–307.

Katsanevakis S., Lefkaditou E., Galinou-Mitsoudi S., Koutsoubas D. & Zenetos A. (2008). “Molluscan species of minor commercial interest in Hellenic seas: Distribution, exploitation and conservation status“. Mediterranean Marine Science, 9: 77-118.

(1979). Berne Convention. Annex II.

(in Croatian) (2013). “Zakon o zaštiti prirode. [Nature Protection Act]”. Narodne novine«, broj 80/2013 [Official Gazette 80/13].

Photo of the day (51): Elisolimax from Madagascar

The photo of this land slug is from the tropical moist forest in northern Madagascar. It was identified according to the photo only. It is either Elisolimax bella or Elisolimax madagascariensis. Genus Elisolimax belong to the family Helicarionidae.

Locality: Madagascar, tropical moist forest, between Joffreville village and the entrance to the Amber Mountain National Park, coordinates: -12.502470, 49.201356, November 15, 2014. Photo by Martin Mandák.

I thank to Martin Mandák from the Czech Republic for taking the photo.

I thank to Owen Griffiths from Mauritius for the slug identification.

Elisolimax from Madagascar. Photo by Martin Mandák, CC-BY-4.0.

Elisolimax from Madagascar. Photo by Martin Mandák, CC-BY-4.0.


Photo of the day (50): Flabellina affinis

Flabellina affinis is a species of a nudibranch (Nudibranchia). Some nudibranchs really breathe by naked gills, but this species belong to a group of nudibranchs, that breathe by the whole body surface.

It is common species in the Mediterranean Sea. It feeds on colonial hydrozoids from the genus Eudendrium. It live in rocky habitat in the sublittoral zone not far from the shore.

I have taken photos in the lab (ex situ), so we take take a look at some anatomical features. Flabellina affinis can reach up to 50 mm, but my specimen is much smaller, about 20 mm. It is pink.

Flabellina affinisIt has a pair of tentacular foot corners (foot tentacles) – the most lower ones. It has a pair of labial tentacles (they are called as oral tentacles in other slug species). The top one ear-like structures are called rhinophores. There is visible small dark eye on the photo above. Eye is more likely on the base of rhinophores than on the base of labial tentacles.

Frontal view of the slug:

Flabellina affinisThe slug has cerata on its body. Cerata are in groups. There are from six to nine groups of cerata on the right side and on the left side of the body. My slug has seven groups of cerata, but the sixth group and the seventh group are not paired.

Flabellina affinisThe slug is small and it can crawl on the water level in the laboratory conditions. So there is also foot or ventral side visible on photos sometimes. There are visible genital apertures bellow the first group of cerata on the right side of the body on the following photos. They looks like two small tubercules. There is visible anus as a black dot on the right side between the first and second group of cerata. Anus looks like a small pointed tubercule:

Flabellina affinis

Flabellina affinisThere is a dark structure between the first and the second group of cerata, but I do not know what it is:

Flabellina affinis

Flabellina affinisReferences

Schulze A. & Wägele H. (1998) “Morphology, anatomy and histology of Flabellina affinis (Gmelin, 1791) (Nudibranchia, Aeolidoidea, Flabellinidae) and its relation to other Mediterranean Flabellina species“. Journal of Molluscan Studies 64(2): 2195-214. doi:10.1093/mollus/64.2.195

Photo of the day (49): Ambigolimax valentianus

Ambigolimax valentianus is a land slug from the family Limacidae. Its native distribution includes Iberian Peninsula only, but it is spreading in many other countries as an invasive species. It can live in greenhouses and similar habitats in cold areas only. It lives in greenhouses in Central Europe too. It is a pest in greenhouses and it is able to overpopulate and then it can be a serious pest. It can reach the length up to 70 mm.

Various views of the slug:

Ambigolimax valentianus

Ambigolimax valentianus

Ambigolimax valentianus

Ambigolimax valentianusThe foot is light gray:

Ambigolimax valentianusThere exist two forms of Ambigolimax valentianus: a form with two dark lateral bands and a a spotted form. The spotted form looks like this. It looks a bit yellow on the photo, but it is caused by the sunglight.

Ambigolimax valentianusIts eggs look like this. I found those eggs below the bowl for the potted plant.

Ambigolimax valentianusNotice the juvenile slug in the front. It is interesting that its egss will not survive temperatures above 33 °C.

A juvenile slug:

Ambigolimax valentianusAnother photo with juvenile slugs:

Ambigolimax valentianusThis species is also known as Lehmannia valentiana. In fact I did not known, that it could be placed in the genus Ambigolimax up today.

So I searched for reasons of its generic placement:

Klee et al. found out based on molecular phylogeny research of cytochrome-c oxidase I (COI) genes, that the genus Lehmannia is diphyletic in 2005. She also repeated the information in her thesis in 2013.

Rowson et al. confirmed such placement also according to the COI genes analysis in 2014. By the way, they did not comment this species in the PLoS article anyhow. They just shown the cladogram on the figure 5.

The results are:

Lehmannia marginata (O. F. Müller, 1774) still belong to the genus Lehmannia Heynemann, 1863, because it is the type species of the genus.

Lehmannia valentiana (Férussac, 1822) belong to the genus Ambigolimax Pollonera, 1887 as a Ambigolimax valentiana (Férussac, 1822). It is the type species of the genus Ambigolimax.

Lehmannia nyctelia (Bourguignat, 1861) also belong to the genus Ambigolimax as Ambigolimax nyctelius (Bourguignat, 1861).

There is a question, where will belong other 13 European species of Lehmannia. Especially those ones, whose reproductive system is not known.


Horsák M., Dvořák L. & Juřičková L. (2004) Greenhouse gastropods of the Czech Republic: current stage of research. Malacological Newsletter, 22: 141–147, page 143.

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). page 163.

Klee B., Falkner G. & Haszprunar G (2005). Endemic radiations of Limax (Gastropoda: Stylommatophora) slugs in Corsica – they came twice. In: Burckhardt D (ed.), 8. Jahrestagung der Gesellschaft für biologische Systematik, Basel 13.-16. September 2005, Abstracts of talks and posters: p.78. Basel (Naturhistorisches Museum). Organisms Diversity and Evolution 5, Electr. Suppl. 13: 75.

Nitz. B. (2013). Integrative systematics and biogeography of Limax (Gastropoda: Stylommatophora). Dissertation Thesis, Ludwig-Maximilians-Universität, München, 133 pp., page 105.

Rowson B., Anderson R., Turner J. & Symondson W. O. C. (2014). The slugs of Britain and Ireland: undetected and undescribed species increase a well-studied, economically important fauna by more than 20%. PLoS ONE 9(4): e91907. doi:10.1371/journal.pone.0091907

Stojnić B., Vukša M., Jokić G. & Čkrkić M. (2011). First record of introduced valencia slug, Lehmannia valentiana (Férussac, 1822), in Serbia. Pesticidi i fitomedicina, 26(3): 213–220. doi:10.2298/PIF1103213S

Udaka H., Mori M., Goto S. G. & Numata H. (2007). Seasonal reproductive cycle in relation to tolerance to high temperatures in the terrestrial slug Lehmannia valentiana. Invertebrate Biology, 126(2): 154–162.

Photo of the day (48): Pisania striata

Pisania striata is a marine snail in the Buccinidae family. It is a common species in the Mediterranean Sea. It is a scavenger or predator, but I found no detailed information about its food. Its habitat include rocky seashore (eulittoral zone or intertidal zone) and in the sublittoral zone not far from the shore (subtidal zone).

The height of the shell is up to 30 mm. There are fine spiral striae on its shell sculpture. The specific name striata is derived from those striate.

This one is from the Dubrovnik-Neretva County, southern Croatia. I have taken this photo in situ in very shallow water (about 2-3 cm) with an ordinary non-water-proof camera. Maybe it can be a motivation for anybody to take photos of marine animals with any camera. You just need to take care about reflections from the water level.

Its body is black. It extend its siphon through the siphonal notch during crawling, because there are chemoreceptors in the siphon and the snail is searching for its prey:

Pisania striata in situDetail of the snail:

Pisania striataApertural view shows, that its foot and some parts of its body are surprisingly light gray:

apertural view of Pisania striataYou can also compare the length of its siphon with tentacles:

foot of Pisania striataAnother view shows that the shape of its operculum is like a droplet:

a live Pisania striataReferences

Dance S. P. (ed.) (1974). The Encyclopedia of Shells. Blanford Press, ISBN 0713706988, page 145.

Photo of the day (47): Lithoglyphus naticoides

Lithoglyphus naticoides is a freshwater snail. Its distribution is Pontic and Danubian.

Shells from my collection comes from Danube river in Slovakia. The apertural view of the shell looks like this. The width of the shell is 8.5 mm and the height of the shell is 8.5 mm:

shell of Lithoglyphus naticoidesOblique view of the same shell:

an oblique view of the shell of Lithoglyphus naticoidesIt lives on the muddy bottom, and it can not lay egg capsules on stones. Therefore is lay egg capsules on shells of other Lithoglyphus naticoides snails. Remains of egg capsules on the shell of Lithoglyphus naticoides:

the shell of Lithoglyphus naticoides with egg capsulesthe shell of Lithoglyphus naticoides with egg capsulesDried egg capsules that have a dried embryo inside:

the shell of Lithoglyphus naticoides with egg capsulesthe shell of Lithoglyphus naticoides with egg capsulesthe shell of Lithoglyphus naticoides with egg capsules

The width of the following shell is 7.0 mm and the height of the shell is 7.0 mm.

apertural view of the shell of Lithoglyphus naticoidesapical view of the shell of Lithoglyphus naticoideslateral view of the shell of Lithoglyphus naticoidesumbilical view of the shell of Lithoglyphus naticoidesI wanted to see a color photo of an operculum of Lithoglyphus naticoides, but I found color drawings on the internet only and black-and-white photo of an operculum in books. So I made few photos of an operculum of Lithoglyphus naticoides.

The width of the operculum is 3.0 mm and the height of the operculum is 4.0 mm. It is the operculum from the shell above. Outer side of the operculum:

outer side of an operculum of Lithoglyphus naticoidesInner side of the operculum:

inner side of an operculum of Lithoglyphus naticoidesReferences


Photo of the day (46): Tandonia rustica and Tandonia kusceri

Updated on July 8, 2016.

Tandonia rustica is a land slug with Central European and South European distribution.

Its native distribution include Bohemia such as this juvenile one from the Northern Bohemia:

Tandonia rusticaIt has small dots.

Its coloration differ slightly from other Tandonia species. These slugs from Bratislava City in Slovakia are Tandonia kusceri. It is non-indigenous in Slovakia.

a group of Tandonia rustica

dorsal view of a Tandonia rusticaReferences

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). page 34 and page 113.

Korábek O., Čejka T. & Juřičková L. (2016): Tandonia kusceri (Pulmonata: Milacidae), a slug new for Slovakia. – Malacologica Bohemoslovaca, 15: 3–8.

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.