Photo of the day (86): Scyllaea pelagica

Scyllaea pelagica is a species of a nudibranch.

When I saw this sea slug for the first time, it resembled a floating rag to me. A very small floating rag. It is even waving in the water and it will bent easily in the smallest water current.

Scyllaea pelagicaScyllaea pelagicaI suppose that such appearance gives to a slug an advantage against predators. The brown coloration gives a resemblance to surroundings between the Sargassum brown algae. Its waving is a cryptic behaviour. Those are two ways of a camouflage.

Its constant movement and bending in every unobvious angles is a challenge for taking photos of this sea slug.

Its body length can reach up to 45 mm. My specimen comes from southern Croatia. The whole distribution of this species is large, because it can be found in all tropical and temperate seas. It is the only species from the family Scyllaeidae in Mediterranean Sea.

Let’s taken a closer look in a clearer position. Right side view of the Scyllaea pelagica heading right:
Scyllaea pelagicaLeft side view of the Scyllaea pelagica heading left:
Scyllaea pelagicaIts rhinophores are very small and they are hidden in rhinophore sheaths. Its head with mouth and with rhinophore sheaths looks like this from underside:
Scyllaea pelagicaThere are two pairs of lobes on its dorsal part of the body. Underside view:
Scyllaea pelagicaThere are also visible dendritic gills on the dorsal part and between lobes. Gills are transparent or white in color.
Scyllaea pelagicaThere is a genital pore on the right side of the body. It lies in front of the first pair of lobes. There is also anus on the right side of the body. It lies between those lobes.
Scyllaea pelagicaThere are also beautiful blue spots on the sides and on the dorsal part of the body.

Where are eyes? I found no eyes in my photos. I am also not sure what exactly are orange like structures inside the body of the slug.

References

Rudman, W.B., 2004 (March 10) Scyllaea pelagica Linnaeus, 1758. [In] Sea Slug Forum. Australian Museum, Sydney.

Cataneo-Vietti R., Chemello R. & Giannuzzi-Savelli R. (eds.) 1991 Atlas of Mediterranean nudibranchs. Atlante dei Nudibranchi del Mediterraneo. La Conchiglia, Roma, page 22 (only mention its occurrence and nothing more).

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Photo of the day (85): dress with cowries

This is a Native American woman’s dress with cowrie shells.

The dress is on display in the Náprstek Museum of Asian, African and American Cultures in Prague. It is a part of the temporary exhibition Indians in 2017-2019.

dress with cowrie shellsIt is a woman’s dress made of cotton. The bodice is decorated with six lines of cowrie shells (family Cypraeidae). They are probably shells of money cowrie Monetaria moneta, that is the most common cowrie.

dress with cowrie shellsThe dress is from the first half of the 20th century. It comes from the Western Plains Indians. According to the Museum staff is was made by Crows or by Cheyennes. Shells comes from the Indo-Pacific tropical waters and therefore they were imported to the Great Plains.

There is also a belt made of hide and of cloth. There were used porcupine quills in the embroidery of the belt:
dress with cowrie shellsSuch cowries decorations were used also by other Native American tribes, including for example Sioux. Decorating by Crows with elk teeth looks very similar. Elk teeth were probably used in times when cowries were not available yet.

The same style of the dress is shown for example on this 1904 photo:

Cheyenne baby in dress with cowrie shells

1904 photo of Cheyenne baby by American photographer Jessie Tarbox Beals (1870-1942). Public domain. It comes from the website of Missouri Historical Society.

It depicts the Cheyenne baby. There are only four rows of cowrie shells. It seems that there are money cowrie Monetaria moneta shells too, but there are also some ring cowrie Monetaria annulus shells on the right sleeve and on the right part of the dress (on the left part on the photo).

References

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Photo of the day (84): Recluzia lutea

Recluzia lutea (Bennett, 1840), synonym: Recluzia rollandiana Petit de la Saussaye, 1853, is a species of a marine pelagic snail. This means that this snail does not live on the sea bottom, but it lives in the water column. Surprisingly this snail has no swimming fins. This species does not live in the whole water column, but in its the most upper part, closer to the surface level. Therefore it is a part of neuston and such gastropods are called neustonic gastropods. Simply said: Recluzia lutea float on the sea surface. There is also the term ‘plankton’ used for these gastropods: that means it is only able to drift and it cannot swim against the water current. This species is holoplanktonic, which means that it is planktonic for its entire life. It live under a raft-like float made from air bubbles and mucus. It has not yet been observed how the float is constructed by Recluzia.

Recluzia lutea

Shells of Recluzia lutea. Photo by Rodrigo B. Salvador, CC-BY-4.0.

These shells of Recluzia lutea were found way up in the Matinhos River, Paraná state, in southern Brazil, after a storm event, and sent to the Zoology museum in São Paulo.

References

Beu A. G. 2017: Evolution of Janthina and Recluzia (Mollusca: Gastropoda: Epitoniidae). Records of the Australian Museum, 69(3): 119–222. DOI: 10.3853/j.2201-4349.69.2017.1666

S. van der Spoel, L.J. Newman & K.W. Estep (accessed December 13, 2018) Recluzia rollandiana. Marine Species Identification Portal.

Photo of the day (80): Tonna galea 2

Tonna galea is a large sea snail, that belongs to the family Tonnidae. It is family of predatory gastropods.

My Tonna galea is from southern Croatia.

Video of crawling Tonna galea on the sand in an aquarium (there is no audio):

Another video of the same Tonna galea (no audio):

The frontal view of Tonna galea usually looks like this:

Tonna galeaWhile this is the view of the same specimen of Tonna galea with extended proboscis:

Tonna galea with extended proboscisProboscis is the darker part coming from its head.

Proboscis is a prehensile tube and there is a mouth at the end of the proboscis. Therefore it is an important part of the body of the sea snail. Proboscis is well innervated (there are nerves inside the wall of proboscis) and there are glands next to the proboscis. I found no exact measurements of the proboscis of such big Tonna galea sea snails in the literature.

References

Simone L. R. L. de 1995: Anatomical study on Tonna galea (Linné, 1758) and Tonna maculosa (Dillwyn, 1817) (Mesogastropoda, Tonnoidea, Tonnidae) from Brazilian region. Malacologia 37(1): 23-32.

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, http://www.linhartmarketing.cz/, 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?

References

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:

Haliotidae

Shells of Haliotidae. Photo by Jan Linhart, http://www.linhartmarketing.cz/, CC-BY-4.0.

Collection of shells of sea snails from the family Costellariidae:

Costellariidae

Shells of Costellariidae. Photo by Jan Linhart, http://www.linhartmarketing.cz/, CC-BY-4.0.

Collection of shells of sea snails from the family Terebridae:

Terebridae

Shells of Terebridae. Photo by Jan Linhart, http://www.linhartmarketing.cz/, 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, http://www.linhartmarketing.cz/, 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, http://www.linhartmarketing.cz/, 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.

References

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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.

References

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.