AtlantaRoger R. Seapy
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Atlanta is the type genus of the Atlantidae, containing all but two of the species in the family (the other two genera, Protatlanta and Oxygyrus, are monospecific). The shell and keel are calcareous (composed of aragonite). The larval shell is retained following metamorphosis, becoming the spire in the adult shell. All species but one, A. californiensis in the temperate North Pacific, dwell in tropical to subtropical waters. The geographic distribution of most species (10) are cosmopolitan, being found in all three main oceans. Among the remaining species, four are Indo-Pacific, two are restricted to the Indian Ocean, one to the Atlantic, two to the Atlantic and Indian Oceans, and two to the Pacific Ocean.
An atlantid with:
- Shell and keel calcareous
- Larval shell becomes spire of adult shell
- Eye morphology of three types: a, b and c (see Atlantidae page)
- Operculum morphology of three types: a, b, c (see Atlantidae page)
- Radular morphology of two types: I and II (see Pterotracheoidea page)
- The shell consists of three sequentially-deposited portions; a dome-shaped embryonic shell (protoconch I) of about one whorl (see below left), a larval shell (protoconch II) of a variable number of whorls (see below middle), and the adult shell (teleoconch) of a variable number of whorls (see below right) Click on an image to view larger version & data in a new window
Figure. Scanning electron micrographs of embryonic portion (protoconch I) of larval shell (left), larval shell (protoconch II; middle), and adult shell (right; protoconch shaded blue to distinguish it from the teleoconch) in Atlanta plana. Scale bars = 0.1 mm (middle) and 0.5 mm (right). © 2005
- Spire whorl number. The number of whorls comprising the spire of the adult shell (the protoconch) is constant, while the number of whorls in the teleoconch increases with shell growth (see above right). The size of the teleoconch whorls (reflected in the width of the whorls when the shell is viewed from the right side) increases rapidly with growth. Thus, the approximate location on the shell where the narrow whorls of the protoconch end and the rapidly increasing width of the teleoconch whorls begin is easily determined under a dissection microscope. The whorl number ranges from two and one-half (Atlanta lesueurii and A. oligogyra) to six (A. gibbosa) (see table below)
- Spire shape and ornamentation. Spire shape is highly variable and can often serve as a distinctive species and species group (see below) characterisitic. Examples include the tall, turreted spire of A. turriculata, the tilted (or "inclined") spire in the A. inclinata and A. gibbosa species groups, and the large, low rounded and elevated spire of A. inflata and A. helicinoidea. Similarly, spire ornamentation can be very distinctive, ranging from smooth (e.g., the A. lesueurii species group and three of the members of the A. peronii species group) to ornamented by low, elevated spiral ridges (e.g., A. inflata, A. helicinoidea, and A. plana) and highly ornate elevated sculpture (e.g., A. brunnea, A. echinogyra and A. turriculata).
- Nineteen species are currently regarded as valid in the genus Atlanta. These species are partitioned into seven species groups (see table below). Tesch (1908) was the first to group together the species of Atlanta sharing similar morphologies. He recognized four species groups; the A. peronii-, A. inflata-, A. turriculata-, and A. inclinata-groups. In addition to these four groups, three additional ones are currently recognized; the A. lesueurii-, A. gaudichaudi- and A. gibbosa groups. Except for Tesch's A. turriculata-group, the composition of Tesch's species groups has changed by species invalidations, addition of new species over time, and addition of three new species groups. The main changes in Tesch's species groups have occurred in the A. peronii-group (A. gaudichaudi and A. lesueurii now form their own species groups) and the A. inclinata-group (A. gibbosa now forms its own group).
One species, A. peresi, is included in the species list for the genus Atlanta (Richter and Seapy, 1999: Table 1) is highly questionable and is excluded from the table below. It was described by Frontier (1966) from the northwestern Indian Ocean off Madagascar. Although its adult shell morphology and opercular type were characterized by Frontier, its eye and radular morphologies are unknown and no specimens from Frontier's collections have been found for further examination. Substantive doubt concerning its validity resulted from the examination of the extensive samples containing atlantid heteropods from the northern Indian Ocean by Richter (1974), who found that none of the specimens could be identified as A. peresi. In addition, study of samples from the southeastern Indian Ocean by Seapy et al. (2003) did not record any specimens that could be identified as this species, and there have been no records of the species from the Pacific Ocean (Seapy, 1990; Newman, 1990). The interested reader is referred to Richter and Seapy (1999: 640) for a further description and discussion of this problematic species.
The geographic distribution of the species in the genus are summarized in the last three columns of the table below. The highest number of species occurs in the Pacific (17), followed by the Indian (16) and the Atlantic (12) Oceans. Ten species are cosmopolitan, recorded from all three major oceans, while five (A. turriculata, A. frontieri, A. plana, A. echinogyra, and A.gibbosa) are Indo-Pacific and one is Indo-Atlantic (A. selvagensis). Two species (Atlanta inflata and A. californiensis) only occur in the Pacific, and one (A. fragilis) is found only in the Atlantic; no species are unique to the Indian Ocean. In should be noted that one species, A. meteori was previously regarded as Indo-Pacific, but it was recorded from the northeastern Atlantic by de Vera, et al. (2006) and must now be treated as cosmopolitan.
The seven species groups, their contained species, and the distinguishing features of each group and species are presented in the table below. The species comprising each species group share the same radular type, usually the same opercular type, and, in many cases, the same eye type.
|Species group||Group characteristics||Species*||Species characteristics||Shell diameter (except keel)||Number of spire whorls||Eye type||Opercular type||Radular type||Atlantic Ocean ||Pacific Ocean ||Indian Ocean |
|A. brunnea- |
|Shell small with tall, rounded keel; spire strongly elevated and sculptured, with complex ornamentation and a prominent spiral ridge; color darkens with age||A. brunnea ||Spire tall conical; color yellowish-brown to dark brown; circumglobal||<2 mm||4||a||a ||I ||+||+||+|
|A. turriculata||Spire tall, turreted; spire color yellowish- to reddish-brown and grading into clear outer shell whorl; Indo-Pacific||<2 mm||4-1/4||a||a ||I ||-||+||+|
|A. inflata- group||Shell either inflated (width ca. 40% of shell diameter) or flat; spire large (relative to shell size) and low with shallow sutures or small and low; spire surface smooth to sculptured (with evenly-spaced spiral ridges)||A. inflata||Shell spire low conical, with low spiral ridges, varible in expression; spire sutures lack coloration; keel tall with truncate leading edge; keel base yellow-brown to brown; Pacific Ocean||<1.5 mm||4-1/4 to 4-1/2||a||c ||I ||-||+||-|
|A. selvagensis||Shell spire low conical, with low spiral ridges, variable in expression; spire sutures reddish-brown; keel base yellow-brown to brown; Atlantic and Indian Oceans ||<2 mm||3-1/2 to 3-3/4 ||a ||c ||I ||+||-||+|
|A. helicinoidea||Body whorl of shell nearly circular in cross section; keel of low to moderate height, rounded; spire large with spiral ridges, somewhat variable in expression; spire light purple or yellow to yellow-tan; circumglobal||<2 mm||4-1/2 to 4-3/4 ||c||c ||I ||+||+||+|
|A. californiensis||Shell flattened; keel of moderate height, truncate, and with red-brown base; spire small (relative to shell size), low conical to globular, and smooth; colorless to uniformly or mottled, light yellow, brown or violet; North Pacific Ocean||<3.5 mm||3-1/4||a||c ||I ||-||+||-|
|A. lesueurii- group||Shell spire very small; after larval metamorphosis, only a single and rapidly-expanding last whorl (teleoconch) is formed ||A. lesueurii||Shell entirely transparent; spire low and conical with prominent (deep) sutures; keel high, truncate; circumglobal||<6 mm||2-1/2||b||b ||I ||+||+||+|
|A. oligogyra||Shell faint pink to yellow; spire low and rounded with shallow sutures: keel of moderate height, rounded; circumglobal||<3 mm||2-1/2||a||b ||I ||+||+||+|
|A. peronii- group||Shell flat, of moderate to large size; spire small||A. peronii||Spire low, rounded; keel of moderate height, truncate; shell colorless, becoming faintly yellow in large specimens; circumglobal||<10 mm||3-1/2||b||b ||II ||+||+||+|
|A. fragilis||Shell fragile (thin-walled), transparent and completely colorless; keel high; Atlantic Ocean||<9 mm||3-1/2||b||b||II ||+||-||-|
|A. rosea||Spire nearly globular; spire whorls difficult to distinguish due to extremely shallow sutures of first two and one-half whorls; color faintly yellow; species name based on bright pink larval shell; circumglobal||<5 mm||3-1/2||b||b ||II ||+||+||+|
|A. frontieri||Spire low, with first and second whorls elevated, forming a low cone; distinctive thin, elevated spiral ridge along outer margin of spire whorls; keel of moderate height, rounded; colorless; Indian Ocean||<5.5 mm||4-1/2||b||b ||II ||-||+||+|
|A. gaudichaudi- group||Shell flat; shell spire small, with low conical shape ||A. gaudichaudi||Spire smooth; keel of moderate height, truncate and with a brown base; shell colorless; circumglobal||<3 mm||3-1/4||b||b ||I ||+||+||+|
|A. plana||Spire low conical with weak, spiral ridges; spire sutures violet; keel moderately low and rounded, with a brown base; Indo-Pacific||<3.5 mm||3-1/2||a||b ||I ||-||+||+|
|A. echinogyra||Spire low conical, slightly tilted relative to shell plane, with prominent spiral ridges and secondary sculpture; spire reddish-brown and teleoconch colorless; Indo-Pacific||<2.5 mm||3-3/4||a||c ||I ||-||+||+|
|A.inclinata- group||Shell spire large, globose (bee-hive shaped), strongly inclined relative to shell plane, with shallow sutures and numerous small tuberculae on the surface; keel moderately high and rounded; internal shell wall of radially-arranged lines||A. inclinata||Spire with small tuberculae scattered on surface; spire weak rose color and last shell whorl colorless; circumglobal||<7 mm||4-1/2||b||c ||II ||+||+||+|
|A. tokiokai||Spire with spirally-arranged rows of low tuberculae; colorless to light yellow; circumglobal||<3 mm||5-1/2||b||c ||II ||+||+||+|
|A. gibbosa- group||Shell spire large and high; internal shell wall without radially-arranged lines; shell completely transparent and colorless||A. gibbosa||Spire moderately inclined relative to shell plane, with a broad base and pointed apex; circumglobal? (presence in Atlantic Ocean uncertain)||<4 mm||6||b||b ||II ||-?||+||+|
|A. meteori||Spire strongly inclined relative to shell plane, conical and steep sided; keel high, truncate; circumglobal||<4 mm||5-3/4||b||b ||II ||+||+||+|
Noteworthy changes have been made in the authorship (and in some cases the spelling or, in the case of Atlanta brunnea, a change in the specific epithet) of seven species in the genus Atlanta that were originally described by Souleyet (1852) in a chapter on the Heteropoda collected from the Bonite Expedition of 1836/1837. Souleyet gave vernacular and species names (e.g., 'Atlante de Gaudichaud' and 'Atlanta Gaudichaudii, nobis'). However, J. E. Gray had earlier latinized Souleyet's vernacular names in an "Explanation of Plates" that was part of the third (1850) of a five volume (1842-1857) collection of illustrations copied by his wife, M. E. Gray from the then-existing literature, which included those from an Eydoux and Souleyet atlas of 1841? (for a more complete discussion, see the Preface in Janssen and Seapy, 2009). As a result, J. E. Gray formally became the author of all but one (A. gibbosa) of Souleyet's species. The affected species include:
Atlanta brunnea Gray, 1850 (= Atlanta fusca Souleyet, 1852)
Atlanta gaudichaudi Gray, 1850 (= Atlanta gaudichaudii Souleyet, 1852)
Atlanta helicinoidea Gray. 1850 (= Atlanta helicinoides Souleyet, 1852)
Atlanta inclinata Gray, 1850 (= Atlanta inclinata Souleyet, 1852)
Atlanta inflata Gray, 1850 (= Atlanta inflata Souleyet, 1852)
Atlanta lesueurii Gray, 1850 (= Atlanta lesueurii Souleyet, 1852)
Atlanta rosea Gray, 1850 (= Atlanta rosea Souleyet, 1852)
Eydoux, F. and L. F. A. Souleyet. 1841(?). Voyage autour du monde execute pendant les annees 1836 et 1837 sur la corvette 'La Bonite', commandee par m. Vaillant, capitaine de vaisseau, publie par ordre du Gouvernement sous les auspices du Departemente des las Marine. Histoire Naturelle, Zoologie Atlas, 8 pp. Paris
Frontier, S. 1966. Notes morphologiques sur les Atlanta récoltées dans le plancton de Nosy Bé (Madagascar). Cah. ORSTOM, Sér. Océanogr. 4: 131-139.
Gray, J. E. 1850. Explanation to the plates. In: Gray, M. E., Figures of molluscous animals selected from various authors, etched for the use of students. Vol. 4, 124 pp. Longman, Brown, Green and Longmans, London.
Janssen, A. W. and R. R. Seapy. 2009. On the identity and distribution of Atlanta inflata Gray, 1850 (Gastropoda, Pterotracheoidea, Atlantidae) in the world's oceans. Basteria 73: 139-157.
Richter, G. 1961. Die Radula der Atlantiden (Heteropoda, Prosobranchia) und ihre Bedeutung für die Systematik und Evolution der Famiie. Zeitschrift f?r Morphologie und ?kologie das Tiere: 163-238.
Richter, G. 1974. Die Heteropoden der "Meteor"-Expedition in den Indischen Ozean, 1964/65. "Meteor" Forschungs-Ergebnisse 17(D): 55-78.
Richter, G. and R. R. Seapy. 1999. Heteropoda, pp. 621-647. In: D. Boltovskoy (ed.), South Atlantic Zooplankton. Leiden: Backhuys Publ.
Seapy, R. R. 1990. The pelagic family Atlantidae (Gastropoda: Heteropoda) from Hawaiian waters: a taxonomic survey. Malacologia 32: 107-130.
Seapy, R. R., C. M. Lalli and F. E. Wells. 2003. Heteropoda from western Australian waters, pp. 513-546. In: F. E. Wells, D. I. Walker and D. S. Jones (eds.), The marine flora and fauna of Dampier, Western Australia. Perth: Western Australia Museum.
Souleyet, [L. F. A.] 1852. In: Eydoux, [F.] and Souleyet [L. F. A.], Voyage autour du monde execute pendant les annees 1836 et 1837 sur la corvette 'La Bonite'... Zoologie, col. 2. 664 pp. A. Bertrand, Paris.
Vera, de A., R. R. Seapy, and F. Hernandez. 2006. Heteropod molluscs from waters around the Selvagens Islands (Gastropoda: Carinarioidea). Vieraea 34: 33-43.
Correspondence regarding this page should be directed to Roger R. Seapy at
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- First online 19 February 2005
- Content changed 31 January 2010
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Seapy, Roger R. 2010. Atlanta http://tolweb.org/Atlanta/28752/2010.01.31 in The Tree of Life Web Project, http://tolweb.org/. Version 31 January 2010 (under construction).