AtlantaRoger R. Seapy
This tree diagram shows the relationships between several groups of organisms.
The root of the current tree connects the organisms featured in this tree to their containing group and the rest of the Tree of Life. The basal branching point in the tree represents the ancestor of the other groups in the tree. This ancestor diversified over time into several descendent subgroups, which are represented as internal nodes and terminal taxa to the right.
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An atlantid with:
- Shell and keel calcareous
- Larval shell becomes the spire in the 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 adult shell consists of three sequentially-deposited regions (see the images below); a dome-shaped embryonic shell (protoconch I) of about one whorl, a larval shell (protoconch II) of a variable number of whorls, and the adult shell (teleoconch) also of a variable number of whorls
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Figure. Scanning electron micrographs of the embryonic portion (protoconch I) of the larval shell (left), the larval shell (protoconch II; middle), and the adult shell (right) in Atlanta plana. Note that in the last SEM the protoconch is shaded blue to distinguish it from the teleoconch. Scale bars = 100 µm (middle) and 0.5 mm (right). © 2005
- The number of whorls comprising the shell spire is an important taxonomic character that can be difficult to visualize. When the shell is viewed from its right side, the total number of whorls that make up an adult shell can be determined by counting outward from the embryonic shell. In the above example of Atlanta plana, the shell possesses a total of 4-1/4 whorls. Although the total whorl count may be useful as a taxonomic character for describing fully-grown adults, it is variable in all other individuals since the number increases with shell growth. However, the number of whorls comprising the shell spire is not variable, but rather is predictable because it represents only the larval portion of the adult shell. In late-stage larvae (such as the larval shell image above), the last 1/4 whorl can be seen to increase noticeably in width by comparison with the preceding whorls. In larval shells that have surface sculpture, the junction between the larval shell and the beginning of the adult shell (teleoconch) is often marked by the termination of, or a change in, the sculpture pattern (see, for example, the SEM of the tilted shell spire on the A. brunnea page). Even without the ability to distinguish this point of transition the point at which the whorl width increases markedly is visible under the dissection microscope. The sketch below of the whorl sutures in Atlanta inflata give an example of the method used to determine the number of spire whorls. Note that in practice, the shell is first oriented so that the embryonic shell is directed upward in the field of view. Then, the whorls are counted outward from the embryonic part of the spire using an imaginary line directed upward. In the case of A. inflata, the number of spire whorls at the point of rapid increase in whorl width is 4-1/2. Examples of whorl sketches for two other species, A. lesueuri and A. peroni (from Richter and Seapy, 1999), are included below for comparison. Spire whorl numbers for the nineteen species of Atlanta are included in the table below and range from two and one-half (in A. lesueurii and A. oligogyra) to six (in A. gibbosa).
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Figure. Sketch of the whorl sutures from Atlanta inflata. The shell is oriented with the embryonic shell oriented upward and the whorls are counted based on an imaginary line directed upward. the numbers in the sketch denote the end of one whorl and the beginning of the next whorl. The number of whorls in the spire in this example is 4-1/2, as indicated by the arrow. © 2009 Roger R. Seapy
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Click on an image to view larger version & data in a new windowFigure. Sketches of the whorl sutures on the shell spire and extending onto the first adult shell whorl in Atlanta lesueurii (left) and A. peronii (right). The dashed line in each sketch denotes the ending and beginning point for each spire whorl. The arrow at the bottom of each sketch indicates the number of whorls comprising the shell spire. © 2009
- The shape of the spire is highly variable among Atlanta species and can often serve as a distinctive character (see below). Examples include the tall, turreted spire of A. turriculata, the conical spire of A. brunnea, and the tilted (or "inclined") spires in the A. inclinata and A. gibbosa species groups .
- In addition to spire shape, spire ornamentation can also 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), to highly ornate and 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, 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, the 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 (with A. gaudichaudi and A. lesueurii now forming their own species groups) and the A. inclinata-group (the A. gibbosa now forming its own group).
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, five (A. turriculata, A. frontieri, A. plana, A. echinogyra, and A.gibbosa) are Indo-Pacific, two (Atlanta inflata and A. californiensis) occur only in the Pacific, one (A. selvagensis) is Indo-Atlantic, and one (A. fragilis) has only been recorded from 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 was recorded from the northeastern Atlantic by de Vera, Seapy and Hernandez (2006) and must now be regarded as cosmopolitan.
The seven species groups, their contained species, the distinguishing features of each group and species, and each species' geographic distribution 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)
de Vera, A., R. R. Seapy, and F. Hernandez. 2006. Heteropod molluscs from waters around the Selvagens Islands (Gastropoda: Carinarioidea). Vieraea 34: 33-43.
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.
Thiriot-Quievreux, C. 1968. Variations saisonnieres des Mollusques dans le plancton de la region de Banyuls-sur-Mer (Zone sud du Golfe du Lion) Novembre 1965 - Decembre 1967. Vie et Milieu, Serie B, 19: 35-83.
Thiriot-Quievreux, C. 1970. Cycles annuels des populations planctoniques de Mollusques en 1968 dans la region de Banyuls-sur-Mer. Cmmparisison avec les annees precedentes 1965-1967 Vie Milieu, Series B, 21: 311-335.
Thiriot-Quievreux, C. 1973. Heteropoda. Oceanography and Marine Biology Annual Review 11: 237-261.
Correspondence regarding this page should be directed to Roger R. Seapy at
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- First online 19 February 2005
- Content changed 17 July 2010
Citing this page:
Seapy, Roger R. 2010. Atlanta http://tolweb.org/Atlanta/28752/2010.07.17 in The Tree of Life Web Project, http://tolweb.org/. Version 17 July 2010 (under construction).