Juliidae,

common name In biology, a common name of a taxon or organism (also known as a vernacular name, English name, colloquial name, country name, popular name, or farmer's name) is a name that is based on the normal language of everyday life; and is often con ...

the bivalved gastropods, is a

family Family (from ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

of small

sea snail Sea snails are slow-moving marine (ocean), marine gastropod Mollusca, molluscs, usually with visible external shells, such as whelk or abalone. They share the Taxonomic classification, taxonomic class Gastropoda with slugs, which are distinguishe ...

s, marine

gastropod Gastropods (), commonly known as slugs and snails, belong to a large Taxonomy (biology), taxonomic class of invertebrates within the phylum Mollusca called Gastropoda (). This class comprises snails and slugs from saltwater, freshwater, and fro ...

mollusk Mollusca is a phylum of protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant species of molluscs are recognized, making it the second-largest animal phylum after Arthropoda. The ...

s or

micromollusk A micromollusc is a shelled mollusc which is extremely small, even at full adult size. The word is usually, but not exclusively, applied to marine molluscs, although in addition, numerous species of land snails and freshwater molluscs also ...

s in the superfamily Oxynooidea, an opisthobranch group.MolluscaBase eds. (2021). MolluscaBase. Juliidae E. A. Smith, 1885. Accessed through: World Register of Marine Species at: http://marinespecies.org/aphia.php?p=taxdetails&id=196330 on 2021-06-09 Taxonomic edit history These are

sacoglossa Sacoglossa are a superorder of small sea slugs and sea snails, marine gastropod mollusks that belong to the clade Heterobranchia known as sacoglossans. There are 284 valid species recognized within this superorder. Sacoglossans live by ingestin ...

n (sap-sucking) sea snails, and many of them are green in color. These snails are extremely unusual in that their shells consist of two separate hinged pieces or valves. The valves are joined by a ligament, and look nothing like a normal snail shell; instead the valves look almost exactly like the two hinged valves of a

clam Clam is a common name for several kinds of bivalve mollusc. The word is often applied only to those that are deemed edible and live as infauna, spending most of their lives halfway buried in the sand of the sea floor or riverbeds. Clams h ...

, a

bivalve Bivalvia () or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class (biology), class of aquatic animal, aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed b ...

mollusk, which is a related but very different class of mollusks. Up until the mid-20th century, the Juliidae were known only from

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

shells, and not surprisingly, these fossils were interpreted as being the shells of bivalves. '' Julia'', which is the type genus of the family, was named in 1862 by

Augustus Addison Gould Augustus Addison Gould (April 23, 1805 – September 15, 1866) was an American naturalist and the foremost conchologist of his era. He described over 1,100 new species of mollusks, including all known mollusks of Massachusetts and the shells co ...

, who described it as a bivalve genus. Juliidae are known from the

Eocene The Eocene ( ) is a geological epoch (geology), epoch that lasted from about 56 to 33.9 million years ago (Ma). It is the second epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), Era. The name ''Eocene'' comes ...

period to the Recent, but they probably first appeared during the

Paleocene The Paleocene ( ), or Palaeocene, is a geological epoch (geology), epoch that lasted from about 66 to 56 mya (unit), million years ago (mya). It is the first epoch of the Paleogene Period (geology), Period in the modern Cenozoic Era (geology), ...

. The similarity of the bivalved shells of Juliidae to those of bivalves does ''not'' mean that these snails are closely related to bivalves; this is an example of

convergent evolution Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last comm ...

Nomenclature

Juliidae was named by Edgar Albert Smith in 1885. The

type genus In biological taxonomy, the type genus (''genus typica'') is the genus which defines a biological family and the root of the family name. Zoological nomenclature According to the International Code of Zoological Nomenclature, "The name-bearin ...

is '' Julia'', named by

in 1862. The family name Prasinidae was proposed earlier, by Stoliczka in 1871, but because ''Prasina'' is a

junior synonym In taxonomy, the scientific classification of living organisms, a synonym is an alternative scientific name for the accepted scientific name of a taxon. The botanical and zoological codes of nomenclature treat the concept of synonymy differently. ...

of ''Julia'' and use of Juliidae has become widely accepted, Juliidae is the correct name according to article 40.2 of the

International Code of Zoological Nomenclature The International Code of Zoological Nomenclature (ICZN) is a widely accepted Convention (norm), convention in zoology that rules the formal scientific name, scientific naming of organisms treated as animals. It is also informally known as the I ...

Research history

Initial interpretation as bivalves

These bivalved gastropods were for a long time only known from

s and dead material. Because of this, they had been described as being somewhat atypical

bivalves Bivalvia () or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed by a calcified exoskeleton consis ...

. In the late 19th century they were classified among the bivalves, within the family

Mytilidae The Mytilidae are a family (biology), family of small to large Marine life, marine and Brackish water, brackish-water bivalve molluscs in the order (biology), order Mytilida. One of the genera, ''Limnoperna fortunei, Limnoperna'', even inhabits f ...

, the mussels. George Washington Tryon, Jr. (1884)
''Structural and systematic conchology: an introduction to the study of the Mollusca. Volume III''
Philadelphia, published by the author
page 267
''Julia'' was named by

in 1862. He considered it a bivalve with similarities to '' Vulsella'', ''

Pedum Pedum () was an ancient town of Latium in central Italy, located between Tibur and Praeneste, near modern Gallicano nel Lazio. The town was a member of the Latin League. History Around 488 BC, Pedum was captured by an invading army of the ...

'', and

Veneridae The Veneridae or venerids, common name: Venus (mythology), Venus clams, are a very large family of minute to large, saltwater clams, marine bivalve molluscs. Over 500 living species of venerid bivalves are known, most of which are edible, and m ...

, but noted that it was difficult to classify due to its distinctiveness. Another genus that would later be identified as a juliid, ''

Berthelinia ''Berthelinia'' is a genus of gastropod belonging to the family Juliidae.MolluscaBase eds. (2021). MolluscaBase. Berthelinia Crosse, 1875. Accessed through: World Register of Marine Species at: http://www.marinespecies.org/aphia.php?p=taxdetails ...

'', was named by H. Crosse based on a fossil in 1875. Crosse initially only had a single valve to study, and thus was unaware of its bivalved nature, and identified it as a gastropod similar to '' Hipponix''. In 1887, with more material at hand, Crosse and Fischer realized that ''Berthelinia'' had a bivalved shell and accordingly reclassified it as a bivalve. Two shells of ''Julia'' were obtained during the ''Challenger'' expedition, and in Edgar Albert Smith's 1885 review of the bivalves collected from the expedition, he named the family Juliidae for the genus, noting that its systematic position was not yet determined. In 1951, Arthur Day Howard reported a freshly dead shell found while washing

green algae The green algae (: green alga) are a group of chlorophyll-containing autotrophic eukaryotes consisting of the phylum Prasinodermophyta and its unnamed sister group that contains the Chlorophyta and Charophyta/ Streptophyta. The land plants ...

, and predicted the live animal would be found attached to green algae.

Discovery of live animals

Until the mid-20th century, these creatures were still considered to be

. Then, in 1959, living individuals of one species were collected on the green alga, '' Caulerpa'', in

Japan Japan is an island country in East Asia. Located in the Pacific Ocean off the northeast coast of the Asia, Asian mainland, it is bordered on the west by the Sea of Japan and extends from the Sea of Okhotsk in the north to the East China Sea ...

. It was immediately clear that these animals were, in fact, unusual gastropods with a two-part shell. The first-discovered live species of bivalved gastropod was '' Tamanovalva limax'', described by Kawaguti & Baba (1959). Once the habitat, appearance, and life habits of these very small and inconspicuous animals were understood, researchers in subsequent years were able to find a number of other species and genera in different parts of the world, also living on various species of ''Caulerpa''.

Description

As Tryon (1884) wrote in his description of the genus '' Julia'': the shell is oblong, thick, and cordiform. The valves are closed, the margins entire and the valves are inequilateral. The lunule is deep circular, projecting into the interior of the right

valve A valve is a device or natural object that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids, or Slurry, slurries) by opening, closing, or partially obstructing various passageways. Valves are technically Pip ...

, the left valve is in the same place furnished with dentiform tubercles. The hinge line is simple and arched. The

ligament A ligament is a type of fibrous connective tissue in the body that connects bones to other bones. It also connects flight feathers to bones, in dinosaurs and birds. All 30,000 species of amniotes (land animals with internal bones) have liga ...

is external and narrow. There are two muscle scars which are unequal and subcentral. These animals have two valves, and the soft parts can be completely withdrawn inside the shell. de Bruyne R. H. (2004). ''Encyklopedie ulit a lastur''. Rebo Productions, 336 pp., , page 223. The two valves are usually thin and translucent. In the genus ''

Tamanovalva ''Berthelinia'' is a genus of gastropod belonging to the family Juliidae.MolluscaBase eds. (2021). MolluscaBase. Berthelinia Crosse, 1875. Accessed through: World Register of Marine Species at: http://www.marinespecies.org/aphia.php?p=taxdetails ...

'' there is a

protoconch A protoconch (meaning first or earliest or original shell) is an embryonic or larval shell which occurs in some classes of molluscs, e.g., the initial chamber of an ammonite or the larval shell of a gastropod. In older texts it is also called " ...

on the

apex The apex is the highest point of something. The word may also refer to: Arts and media Fictional entities * Apex (comics) A-Bomb Abomination Absorbing Man Abraxas Abyss Abyss is the name of two characters appearing in Ameri ...

of the left valve. This is clearly visible in the left valve of '' Tamanovalva babai''. The body of the live animals is in most cases green (as it is in many

ns), and in many species the individual appears green in totality. This, combined with the very small overall size, makes the animal hard to see on the green algae on which it lives. This ability serves as

crypsis In ecology, crypsis is the ability of an animal or a plant to avoid observation or detection by other animals. It may be part of a predation strategy or an antipredator adaptation. Methods include camouflage, nocturnality, subterranean life ...

, especially as cryptic coloration (

camouflage Camouflage is the use of any combination of materials, coloration, or illumination for concealment, either by making animals or objects hard to see, or by disguising them as something else. Examples include the leopard's spotted coat, the b ...

). In two specie

an

the camouflage is even more complete: the mantle of the animal is patterned in a way that closely resembles the structure of the alga on which it lives. The empty valves of the shells of these animals are in some cases green, in other cases brownish-green or yellow, and in yet others, colorless. The species '' Julia zebra'' has shells that are finely striped with brown and blotched with white.

Ecology

Distribution

Species in this family occur in all tropical zone seas and all

temperate zone In geography, the temperate climates of Earth occur in the middle latitudes (approximately 23.5° to 66.5° N/S of the Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ra ...

seas.

Life cycle

After hatching, the juvenile snails immediately take their place on algae (the larval phase of

veliger A veliger is the planktonic larva of many kinds of sea snails and freshwater snails, as well as most bivalve molluscs (clams) and tusk shells. Description The veliger is the characteristic larva of the gastropod, bivalve and scaphopod taxono ...

is extremely short).

Feeding habits

Juliidae feed on

of the genus '' Caulerpa''. Some species of Juliidae feed only on one species of ''Caulerpa''; others feed on multiple species of this green alga.

2005 taxonomy

This family is within the superorder

Sacoglossa Sacoglossa are a superorder of small sea slugs and sea snails, marine gastropod mollusks that belong to the clade Heterobranchia known as sacoglossans. There are 284 valid species recognized within this superorder. Sacoglossans live by ingestin ...

(according to the taxonomy of the Gastropoda by Bouchet & Rocroi, 2005). The family Juliidae consists of the following subfamilies (according to the taxonomy of the Gastropoda by Bouchet & Rocroi, 2005): * subfamily Juliinae E. A. Smith, 1885 - synonym: Prasinidae Stoliczka, 1871 * subfamily Bertheliniinae Keen & A. G. Smith, 1961 - synonym: Tamanovalvidae Kawaguti & Baba, 1959 * † (fossil) subfamily Gougerotiinae Le Renard, 1980

Genera

The

of the family Juliidae is '' Julia'' Gould, 1862. Based on a classification by Jensen (1996),Jensen K. R. (1996). "Phylogenetic systematics and classification of the Sacoglossa (Mollusca, Gastropoda, Opisthobranchia)". ''Philosophical Transactions of the Royal Society London B Biological Sciences'' 351(1335): 91–122. . three recent genera were recognized in the family Juliidae: '' Julia'' Gould, 1862; ''Berthelinia'' Crosse, 1875; ''

'' Kawaguti & Baba, 1959. While Jensen (2007)Jensen K. R. (November 2007)
"Biogeography of the Sacoglossa (Mollusca, Opisthobranchia)"
. '' Bonner zoologische Beiträge'' 55(2006)(3-4): 255–281. recognized two recent genera with a few subgenera in the genus ''Berthelinia''. Recent species listed here are based on Jensen (2007), fossil genera and species are based on Le Renard (1996):

Juliinae

* '' Julia'' Gould, 1862 - synonym: ''Prasina'' Deshayes, 1863 ** (recent) '' Julia burni'' Sarma, 1975 ** (invalid recent species) '' Julia cornuta'' (De Folin, 1867) ** (invalid recent species) '' Julia equatorialis'' Pilsbry & Olsson, 1944 ** (recent) '' Julia exquisita'' Gould, 1862 - this species was mentioned in report by the

Challenger expedition The ''Challenger'' expedition of 1872–1876 was a scientific programme that made many discoveries to lay the foundation of oceanography. The expedition was named after the naval vessel that undertook the trip, . The expedition, initiated by W ...

Bolland R. F. (2001)
"Okinawan Opisthobranch of the Week ''Julia exquisita''"
Last change of the page 12 March 2001. ** (recent) '' Julia japonica'' Kuroda & Habe, 1951 ** (recent) '' Julia mishimaensis'' Kawaguti & Yamasu, 1982 ** (recent) '' Julia thecaphora'' (Carpenter, 1857) - a probable synonym is '' Julia zebra'' Kawaguti, 1981 ** (recent) '' Julia zebra'' Kawaguti 1981 * (fossil) '' Candinia'' Le Renard J., Sabelli B. & Taviani M. 1996Le Renard J., Sabelli B. & Taviani M. (March 1996). "On ''Candinia'' (Sacoglossa: Juliidae), a New Fossil Genus of Bivalved Gastropods". ''

Journal of Paleontology The ''Journal of Paleontology'' is a peer-reviewed scientific journal covering the field of paleontology. It is managed and published by Cambridge University Press on behalf of the Paleontological Society. Indexing The ''Journal of Paleontology ...

'' 70(2): 230–235. ** (fossil) '' Candinia pliocaenica'' Le Renard J., Sabelli B. & Taviani M. 1996 - from lower Pliocene near

Siena Siena ( , ; traditionally spelled Sienna in English; ) is a city in Tuscany, in central Italy, and the capital of the province of Siena. It is the twelfth most populated city in the region by number of inhabitants, with a population of 52,991 ...

in Italy. ** (fossil) '' Candinia krachi'' (Baluk & Jakubowski, 1968) - synonym: ''Berthelinia krachi'' Baluk & Jakubowski, 1968

Bertheliniinae

* ''Berthelinia'' Crosse, 1875 - type genus of the subfamily Bertheliniinae ** subgenus ''Berthelinia'' Crosse, 1875 *** (recent) '' Berthelinia caribbea'' Edmunds, 1963Rudman W. B. (4 October 2003)
"''Berthelinia caribbea'' Edmunds, 1963"
. Sea Slug Forum. Australian Museum, Sydney, accessed 10 May 2009. *** (recent) '' Berthelinia chloris'' (Dall, 1918) *** (invalid recent species) ''Berthelinia corallensis'' Hedley, 1920 *** (recent) '' Berthelinia darwini'' Jensen, 1997 *** (recent) '' Berthelinia ganapati'' Sarma, 1975 *** (recent) '' Berthelinia pseudochloris'' Kay, 1964 *** (recent) '' Berthelinia rottnesti'' Jensen, 1993 *** (recent) '' Berthelinia schlumbergeri'' Dautzenberg, 1895 *** (recent) '' Berthelinia waltairensis'' Sarma, 1975 *** (fossil) '' Berthelinia elegans'' Crosse, 1875 ** subgenus ''

Midorigai ''Berthelinia'' is a genus of gastropod belonging to the family Juliidae.MolluscaBase eds. (2021). MolluscaBase. Berthelinia Crosse, 1875. Accessed through: World Register of Marine Species at: http://www.marinespecies.org/aphia.php?p=taxdetails ...

'' : synonym of ''Berthelinia'' Crosse, 1875 *** (recent) '' Berthelinia australis'' (Burn, 1960) - synonym: '' Midorigai australis'' Burn, 1960 ** subgenus ''

'' Kawaguti & Baba, 1959 : synonym of ''Berthelinia'' Crosse, 1875 *** (recent) '' Berthelinia babai'' (Burn, 1965) - synonym: '' Tamanovalva babai'' Burn, 1965 Rudman W. B. (16 October 2011)
"''Tamanovalva babai'' Burn, 1965"
. Sea Slug Forum. Australian Museum, Sydney, accessed 10 May 2009. *** (recent) '' Berthelinia fijiensis'' (Burn, 1966) *** (recent) '' Berthelinia limax'' (Kawaguti & Baba, 1959) - synonym: '' Tamanovalva limax'' Kawaguti & Baba, 1959 - a type species of the subgenus ''Tamanovalva'' Kawaguti S. & Baba K. (1959). "A preliminary note on a two-valved sacoglossan gastropod, ''Tamanovalva limax'', n. gen., n. sp., from Tamano, Japan". ''Biological Journal Okayama University'' 5(3-4): 177–184. ** subgenus ''

Edenttellina ''Berthelinia'' is a genus of gastropod belonging to the family Juliidae.MolluscaBase eds. (2021). MolluscaBase. Berthelinia Crosse, 1875. Accessed through: World Register of Marine Species at: http://www.marinespecies.org/aphia.php?p=taxdetails ...

'' : synonym of ''Berthelinia'' Crosse, 1875 *** (recent) '' Berthelinia typica'' (Gatliff &

Gabriel In the Abrahamic religions (Judaism, Christianity, Islam), Gabriel ( ) is an archangel with the power to announce God's will to mankind, as the messenger of God. He is mentioned in the Hebrew Bible, the New Testament and the Quran. Many Chris ...

, 1911) - synonym: '' Edenttellina typica'' Gatliff & Gabriel, 1911Rudman W. B. (16 October 2001)
"''Edenttellina typica'' Gatliff & Gabriel, 1911"
. Sea Slug Forum. Australian Museum, Sydney, accessed 10 May 2009. * (fossil?) '' Anomalomya'' Cossmann, 1887 * (fossil?) '' Namnetia'' Cossmann, 1906 * (fossil?) '' Squamulinia'' Le Renard, 1989

Gougerotiinae

* (fossil) '' Gougerotia'' Le Renard, 1980 - type genus of the subfamily Gougerotiinae ** (fossil) '' Gougerotia orthodonta'' Le Renard, 1980 ? subfamily * (fossil) '' Hemiplicatula'' Deshayes, 1861 * (fossil?) '' Saintia'' de Raincourt, 1877

Evolutionary history

The earliest known fossils of Juliidae date to the

, though the group may have originated earlier, in the

. The earliest-appearing genera are ''

'', '' Gougerotia'', '' Hemiplicatula'', and '' Saintia'', which are known from the

Ypresian In the geologic timescale the Ypresian is the oldest age (geology), age or lowest stage (stratigraphy), stratigraphic stage of the Eocene. It spans the time between , is preceded by the Thanetian Age (part of the Paleocene) and is followed by th ...

age (– million years ago) of the

Paris Basin The Paris Basin () is one of the major geological regions of France. It developed since the Triassic over remnant uplands of the Variscan orogeny (Hercynian orogeny). The sedimentary basin, no longer a single drainage basin, is a large sag in ...

. '' Julia'' itself first appears in the

Oligocene The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...

Footnotes

References

This article incorporates public domain text from reference.

External links

* Cory Pittman & Pauline Fiene. 2009
Juliidae
Sea Slugs of Hawaii.
Images of 4 species of Juliidae in Japan

Photos of ''Julia exquisita''
at Sea Slug Forum
Detailed photos of the shell of ''Julia exquisita''
at Sea Slug Forum * http://taxonomist.symphonic-net.com/contents/Others/Julia/julia!.html {{Authority control Extant Eocene first appearances