Photo of the day (79): Syrinx aruanus

Syrinx aruanus is a species of extant gastropod with the largest shell. The height of the shell can be up 72.2 cm. The largest specimen is stored in the Houston Museum of Natural Science. The volume of the animal is also very large. It is thought to be more voluminous than the largest extinct snail Campanile giganteum.

Syrinx aruanus is a marine sea snail and it belong to the family Turbinellidae.

I thank Jan Linhart, who has taken the photo of the shell in the Phuket Sea shell Museum, Thailand. I do not know exact measurements of this shell.

Syrinx aruanus

Shell of Syrinx aruanus in the Phuket Sea shell Museum. Photo by Jan Linhart,, CC-BY-4.0.

Specimen of the shell height 91 cm was previously reported in the literature, but the reported size was wrong.

It may be also the heaviest extant snail (reaching up to 18 kg?), but I found no proper reference.

What are the limits of gastropods?


McClain C. R., Balk M. A., Benfield M. C., Branch T. A, Chen C., Cosgrove J., Dove A. D. M., Gaskins L. C., Helm R. R., Hochberg F. G., Lee F. B., Marshall A., McMurray S. E., Schanche C., Stone S. N. & Thaler A. D. 2015: Sizing ocean giants: patterns of intraspecific size variation in marine megafauna. – PeerJ 3:e715.  DOI: 10.7717/peerj.715.

Taylor J. D. & Glover E. A. 2003: Food of giants – field observations on the diet of
Syrinx aruanus (Linnaeus, 1758) (Turbinellidae) the largest living gastropod. pp. 217-223. – In: Wells F. E., Walker D. I. & Jones D. S. (eds) 2003: The Marine Flora and Fauna of Dampier, Western Australia. Western Australian Museum, Perth.


Gastropods in Phuket Sea shell Museum

Phuket Sea shell Museum is located at the south of the Phuket Island in Thailand.

I thank to Jan Linhart who has taken these photos of shells in the Phuket Sea shell Museum.

Collection of shells of sea snails from the family Haliotidae:


Shells of Haliotidae. Photo by Jan Linhart,, CC-BY-4.0.

Collection of shells of sea snails from the family Costellariidae:


Shells of Costellariidae. Photo by Jan Linhart,, CC-BY-4.0.

Collection of shells of sea snails from the family Terebridae:


Shells of Terebridae. Photo by Jan Linhart,, CC-BY-4.0.

Stages of growth of the Charonia tritonis from the family Ranellidae:

Charonia tritonis

Stages of growth of the Charonia tritonis. Photo by Jan Linhart,, CC-BY-4.0.

Stages of growth of the Turbinella pyrum from the family Turbinellidae:

Turbinella pyrum

Stages of growth of the Turbinella pyrum. Photo by Jan Linhart,, CC-BY-4.0.

There are also other shells of gastropods and other shells of molluscs, such as ammonites and bivalves in the museum. It is worth to visit.




Photo of the day (78): eggs of Tarantinaea lignaria

Those are egg capsules and embryos of a marine snail Tarantinaea lignaria from the family Fasciolariidae. Its synonyms are Pleuroploca lignaria  and Fasciolaria lignaria.

Egg capsules of Fasciolariidae are possible to identify to the genus level and to the species level. But majority of egg capsules of Fasciolariidae is not known.

Tarantinaea lignaria eggsThe egg capsules looks like on these photos. There is a circular opening in the middle of the cup. Newly hatched snails are escaping through the opening. There are visible embryos through the transparent wall of the capsules and there can be some few embryos inside one capsule. Exact number of embryos in one capsule was not published. It seems that this species may have a direct development.
Tarantinaea lignaria eggsThese egg capsules comes from the southern Croatia. I have taken these photos at September 28, 2016. Majority of snails hatched out already, but there are still some (live?) embryos visible in few capsules. There is also a juvenile snail on one of the capsules that probably (but not surely) belong to the same species.
Tarantinaea lignaria eggsDetail cropped from the previous photo shows a juvenile snail:
Tarantinaea lignaria eggsAnother view of the cluster of egg capsules:
Tarantinaea lignaria eggsDetail cropped from the previous photo shows two egg capsules:
Tarantinaea lignaria eggs The drawing of egg capsules of Tarantinaea lignaria is in the series on Gunnar Thorson’s collection of prosobranch egg capsules. I did not made proper measurements.

I thank to Dr. Paolo Russo from Italy for the species identification.

Gunnar Thorson (1906-1971) was professor of marine biology at the University of Copenhagen. He assembled the collection of egg capsules but he did not publish results of the whole collection by himself. Series of four monographs based on Thorson’s collection was published in 1992-2000 and it is very useful resource for anybody interested in this field.


D’Asaro C. N. 2000: Gunnar Thorson’s world-wide collection of prosobranch egg capsules: Fasciolariidae. Ophelia: 52(2), 77-112. DOI: 10.1080/00785236.1999.10409421

Photo of the day (77): egg laying of Phyllidia flava

Those are two marine slugs Phyllidia flava laying eggs. This is ventral view showing the foot of snails in an aquarium. Both of them are laying a spiral ribbon of eggs:
Phyllidia flava laying eggsThis species of sea slug is orange and its eggs are also orange. But you are lucky to see its eggs so clearly like this, because it usually lays eggs on the Axinella cannabina sponge, which is also orange.

It is a “camouflage” in general. This type of camouflage, when the animal visually resemble its surrounding is called “crypsis”. It is a “visual crypsis” and the animal has “cryptic coloration”.

Detail of the bigger slug cropped from the previous photo shows the head part on the left. The slug has its genital pore on the right side of the body so the genital pore is down on the photo:
Phyllidia flava laying eggsPhyllidia flava starts the laying in the center of the spiral, of course. But some species are known to start the spiral ribbon from the outside.(!) Most nudibranchs lays the spiral ribbon in an anticlockwise direction. There are very few nudibranchs that lays egg ribbons in a clockwise direction. Phyllidia flava lays eggs in the same way as the majority of nudibranchs in an anticlockwise direction. You are seeing an underside of the egg ribbon through the transparent glass of the aquarium so the ribbon appear clockwise on these three photos.

Two egg ribbons of Phyllidia flava from underside:
Phyllidia flava egg ribbonsReferences

Rudman, W. B., 2004 (August 2) Nudibranch egg masses – the direction they spiral. Sea Slug Forum. Australian Museum, Sydney.

Photo of the day (75): egg capsules of Stramonita haemastoma

Those are empty egg capsules of Stramonita haemastoma.

Stramonita haemastoma is a big predatory marine snail of the family Muricidae. It inhabits coastal waters (intertidal and subtidal) up to depth of 9 meters. It is thought to be quite common in the Mediterranean Sea, but areas with low abundance exist. However it was reported that the population in Israel in Eastern Mediterranean has collapsed because of warming of the coastal waters. The subspecies living in the Mediterranean Sea is Stramonita haemastoma haemastoma.

My egg capsules of Stramonita haemastoma comes from southern Croatia. Eggs are laid in clusters to solid surface. Number of snails are laying eggs on the same place making collective spawns.

Empty egg capsules of Stramonita haemastoma attached on a valve of a bivalve Mytilus edulis. The filaments all around are byssus filaments of the bivalve:
egg capsules of Stramonita haemastomaThe spawning season was reported from late April to August. Unfertilized capsules are purple, freshly laid capsules are yellow. The egg development lasts about 20 days. But all of capsules on the photos are empty already, because I collected them in late September.

The each capsule is about 10 mm in height, 3 mm wide and 2 mm thick. Although one capsule is just 10 mm long, it contain thousands of eggs (from about 2300 eggs to about 6050 eggs). One female will deposit from 20 to 86 capsules, usually 47 capsules on average. This gives incredible number of about 200 000 eggs per one female. When are hatching larvae leaving the capsule, larvae are about 50 μm in shell height.

Detail of two egg capsules:
egg capsules of Stramonita haemastomaReferences

Lahbib Y., Abidli S. & El Menif T. N. 2011: Spawning and intracapsular development of Stramonita haemastoma haemastoma (Gastropoda: Muricidae) collected in northern Tunisia. Marine Biology Research, 7(7): 719-726. DOI: 10.1080/17451000.2011.558099.

Rilov. G. 2016: Multi-species collapses at the warm edge of a warming sea. Scientific Reports, 6: article number: 36897. DOI: 10.1038/srep36897.

Photo of the day (74): eggs of Arion obesoductus

This is a cluster of eggs of a land slug Arion obesoductus.

It was laid by a specimen, that I captured in central Moravia at October 26, 2017. I captured only one slug and it later laid this cluster of four eggs in captivity. At least two slugs successfully developed and hatched out from these eggs.

I am not sure if there are any informations available about the life cycle of Arion obesoductus. I do not know if laying of four eggs is a rule or exception. Arion obesoductus is a small slug with a maximum body length of 25 mm. So laying clusters with small number of eggs makes sense. Otherwise these eggs looks like any other eggs of slugs from the Arionidae family as well as similar to eggs of many other land gastropods.

The cluster of eggs at December 13, 2017:
eggs of Arion obesoductus

The same cluster of eggs at December 18, 2017:
eggs of Arion obesoductus



Photo of the day (72): Charonia lampas

This statue of a boy holding a shell is a work by Czech sculptor Julius Pelikán (1887–1969). Pelikán’s style is generally classified as realism, symbolism and New Objectivity. Lets suppose that the artist represented the subject truthfully and lets take a look at the shell from malacological/conchological point of view.

The shell is big, with pointed spire, and with numerous spiral ribs on the whole shell. The only conclusion is a Triton’s trumpet of the genus Charonia (family Ranellidae). Ranellidae are marine predatory snails and some of them are small while some of them are really big. There are only three extant species in the genus Charonia. Based on the spiral ribs it can be only Charonia lampas. The shell height of the Charonia lampas is up to 39 cm and it lives in all European seas.

Right side view detail:
statueLeft side view detail:
statueThe boy is listening to “the sound of the ocean”, which is in fact a seashell resonance. The sound of the ocean from a shell is a myth. Symbolist artists tried to feel with all senses, including hearing. The shell is a symbol that is uncovering a hidden secret of the thing. Those are clear signs of symbolism.

The name of the statue is Boy with a shell (Hoch s mušlí). It is a patinated plaster statue with a height of 67 cm. It was made in 1912.

Right side view:
statueFrontal view:
statueLeft side view:
statueThe statue comes from the collection of the Olomouc Museum of Art (Muzeum umění Olomouc). Fortunately this statue is on the display in temporal exhibition “Intimate Expression ‒ The fate and work of Julius Pelikán (1887‒1969) in the 20th century drama” (Intimní exprese ‒ osud a dílo Julia Pelikána (1887‒1969) v dramatu 20. století) in the Regional Museum in Olomouc (Vlastivědné muzeum Olomouc). The exhibition lasts from March 16, 2018 to April 22, 2018.


Vodrážka M. 2018: Intimní exprese ‒ osud a dílo Julia Pelikána (1887‒1969) v dramatu 20. století. ‒ Vlastivědné muzeum v Olomouci v koedici se statutárním městem Olomouc, 100 pp., ISBN 978-80-85037-88-3.

Wikipedia contributors (October 28, 2016): Seashell resonance. ‒ Wikipedia, accessed March 26, 2018.

Zatloukal P. 2011: O Juliu Pelikánovi a Pelikánově vile. ‒ Listy, (4).

Photo of the day (71): Phyllidia flava

Phyllidia flava is a species of a sea slug living in Mediterranean Sea. It lives and feeds on an Axinella cannabina sponge and on other sponges.

Phyllidia flavaThere are two Phyllidia flava slugs on the photo. The left one is emitting some chemicals as a self defensive behavior against predators. This is one of various ways of self defensive behavior, that sea slugs use. I did not hurt the slug anyhow. I just moved it from one aquarium to an aquarium for taking photos and the slug felt threatened. There is an Axinella cannabina sponge on the photo in the background too. My slugs comes from Croatia.

It did not emit the “smoke” for a long time. The slug looked after 72 seconds like this. You can also see gills between the foot and the mantle.
Phyllidia flavaReferences

Kirkland I. (2017) Self Defense. Last change June 9, 2017. Accessed March 15, 2018.