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Atlanta inclinata Gray 1850

Atlanta inclinata Souleyet 1852

Roger R. Seapy
Containing group: Atlanta

Introduction

Atlanta inclinata attains a large maximal size (to 6-7 mm), and the adult shell is clear to light yellow. The keel is moderately elevated, with a rounded to slightly truncated leading edge. The spire consists of about 5 whorls and is globose (or beehive shaped). The internal walls of the spire are decalcified. The spire surface bears small, low tubercles (or punctae) that are usually scattered but sometimes can form irregular spiral lines. The inner surface of the spire has radially-arranged lines (as in A. tokiokai). The innermost whorl adjacent to the umbilicus is rounded and has a low and wide, but nearly indistinct, ridge. Eyes type b, operculum type c, and radula type II. The radula is large, with a growth angle of about 16°, and the number of tooth rows are limited to about 60. The lateral teeth are monocuspid, and the rachidian teeth are about 20% wider than in A. tokoikai. The species has a cosmopolitan distribution in tropical to subtropical waters.

Diagnosis

Characteristics

  1. Shell
    1. Maximal shell diameter large (to 6-7 mm)
    2. Shell clear to light yellow in color
    3. Spire inclined relative to the shell plane
      Click on an image to view larger version & data in a new window
      Click on an image to view larger version & data in a new window

      Figure. Shell of a 3.6 mm Atlanta inclinata; views of the right side (left) and the spire (right).  Images from Richter (1990, figs. 3 and 15), modified by addition of scale bars (= 1.0 mm and 0.1 mm, respectively). © 1990 G. Richter

    4. Spire consists of about 5 whorls (see SEM below of juvenile shell)
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      Click on an image to view larger version & data in a new window

      Figure. Juvenile shell of Atlanta inclinata, viewed from the right side. Image from Richter (1990, fig. 26), modified by addition of scale bar (= 0.5 mm). © 1990 G. Richter

    5. Spire shape globose (beehive shaped), with shallow but distinct sutures evident when spire is viewed from the side (see larval shell below)
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      Click on an image to view larger version & data in a new window

      Figure. Larval shell of Atlanta inclinata in side view. Image modified from Richter (1990, fig. 10) by addition of scale bar (= 0.5 mm). © 1990 G. Richter

    6. Spire surface with small, low tubercles (or punctae) that are usually scattered, but can form irregular spiral lines. Tubercles occasionally continue on to first teleoconch whorl
      Click on an image to view larger version & data in a new window
      Click on an image to view larger version & data in a new window
      Click on an image to view larger version & data in a new window
      Click on an image to view larger version & data in a new window

      Figure. Shell spire of Atlanta inclinata. Image from Leslie Newman (pers. comm.). Scale bar = 100 µm. © 1990 L. J. Newman

    7. Inner walls of spire with radially-arranged lines, which can only be seen using transmitted light (click on image below to resolve the radial lines, which are seen most clearly in the upper portion of the outermost whorl)
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      Click on an image to view larger version & data in a new window

      Figure. Shell spire of Atlanta inclinata, viewed using transmitted light. Image from Richter (1990, fig. 30). © 1990 G. Richter

    8. Internal walls of spire whorls decalcified (see transmitted light photograph below)
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      Click on an image to view larger version & data in a new window

      Figure. Transmitted light photograph of an Atlanta inclinata larval shell in apertural view. Image from Richter (1990, fig. 22), modified by addition of scale bar (= 0.5 mm). © 1990 G. Richter

    9. A very low, wide spiral ridge is present on the rounded whorl adjacent to the umbilicus (see second SEM below)
      Click on an image to view larger version & data in a new window
      Click on an image to view larger version & data in a new window

      Figure. Shell of Atlanta inclinata, viewed from the left side (left) and enlarged to show umbilical region (right). Images from Richter (1990, figs. 4 and 16), modified by addition of scale bars (= 1.0 mm and 100µm, respectively). © 1990 G. Richter

  2. Eyes type b
  3. Operculum type c
  4. Radula type II
    1. Radula large, with a growth angle of about 16°
      Click on an image to view larger version & data in a new window
      Click on an image to view larger version & data in a new window
      Click on an image to view larger version & data in a new window
      Click on an image to view larger version & data in a new window

      Figure. Radula of Atlanta inclinata in dorsal view. Image from Richter (1990, fig. 37), modified by addition of scale bar (= 100 µm). © 1990 G. Richter

    2. Number of tooth rows limited to about 60
    3. Lateral teeth monocuspid (see SEM below)
      Click on an image to view larger version & data in a new window
      Click on an image to view larger version & data in a new window
      Click on an image to view larger version & data in a new window
      Click on an image to view larger version & data in a new window

      Figure. Section of radula with about four tooth rows in Atlanta inclinata. Image from Richter (1990, fig. 32), modified by addition of labels for rachidian and lateral teeth and scale bar (= 100 µm). © 1990 G. Richter 

    4. Rachidian teeth in the adult portion of the radula (see SEM above) about 20% wider than in A. tokiokai, but about 30% narrower than in A. gibbosa and A. meteori (see respective species pages)
      Click on an image to view larger version & data in a new window
      Click on an image to view larger version & data in a new window

      Figure. Rachidian tooth from adult portion of radula in Atlanta inclinata. Image from Richter (1990, fig. 39), modified by addition of scale bar (= 10 µm). © 1990 G. Richter

    Comments

    Historically, the species of Atlanta with inclined spires (i.e., tilted strongly relative to the shell plane) have been treated together in a single A. inclinata species group (van der Spoel, 1976). In his 1990 paper, however, Richter characterized four species of Atlanta with inclined spires, and concluded that they belonged to two distinctively different species groups. He placed two of the species, A. inclinata and A. tokiokai, in the A. inclinata species group and the other two, A. gibbosa and A. meteori, in an A. gibbosa species group. The most comprehensive reference to the species of Atlanta with inclined spires is the paper by Richter (1990); the paper is noteworthy for the organization of the plates enabling direct comparisons between the four species. The species pages on atlantids with inclined spires, beginning with this one, have drawn heavily from this paper.

    The two species in the Atlanta inclinata species group are very similar and Richter (1990) argued that they must be closely related. Features shared by A. inclinata and A. tokiokai (summarized in Richter and Seapy, 1999, p. 639) include: (1) spire large and globose, (2) internal spire whorls decalcified, (3) internal wall of spire whorls with radially-arranged lines, (4) external surface of spire whorls with sculpture of small punctae that continue on to the first whorl of the adult shell, (5) eyes type b, and (6) operculum type c. The main differences between the two species are: (1) the punctae on the spire are smaller and scattered or form irregular spiral lines in A. inclinata, while in A. tokiokai the punctae are larger and are arranged in distinct spiral lines, (2) when the spire is viewed from the side, the sutures are shallow but clearly separate the spire whorls in the former species, while they are shallower and difficult to distinguish in the latter one, (3) a low, nearly indistinct ridge is present on the whorl adjacent to the umbilicus on the left side of the shell in the former species, while this ridge is strongly developed in the latter one, (4) the area between the aforementioned ridge and the umbilicus is rounded in the former species but is flattened in the latter one, (5) the radula is large, with a growth angle of about 16° in the former species, and is small and ribbon-like, with a growth angle of about 9° in the latter one, (6) the lateral teeth are moncuspid in the former species, and have an accessory cusp in the latter one, and (7) the rachidian teeth in the adult portion of the radula are about 20% wider in the former than in the latter species.

Other Names for Atlanta inclinata Gray 1850

References

Richter, G. 1990. Zur Kenntnis der Gattung Atlanta (IV). Die Atlanta inclinata-Gruppe (Prosobranchia: Heteropoda). Archiv für Molluskenkunde 119: 239-275.

Richter, G. and R. R. Seapy. 1999. Heteropoda, pp. 621-647. In: D. Boltovskoy (ed.), South Atlantic Zooplankton. Backhuys Publishers, Leiden.

Spoel, S. van der. 1976. Pseudothecosomata, Gymnosomata and Heteropoda (Gastropoda). Bohn, Scheltema and Holkema, Utrecht. 484 pp.

About This Page


California State University, Fullerton, California, USA

Correspondence regarding this page should be directed to Roger R. Seapy at

Page: Tree of Life Atlanta inclinata Gray 1850. Atlanta inclinata Souleyet 1852. Authored by Roger R. Seapy. The TEXT of this page is licensed under the Creative Commons Attribution License - Version 3.0. Note that images and other media featured on this page are each governed by their own license, and they may or may not be available for reuse. Click on an image or a media link to access the media data window, which provides the relevant licensing information. For the general terms and conditions of ToL material reuse and redistribution, please see the Tree of Life Copyright Policies.

Citing this page:

Seapy, Roger R. 2011. Atlanta inclinata Gray 1850. Atlanta inclinata Souleyet 1852. Version 23 July 2011 (under construction). http://tolweb.org/Atlanta_inclinata/28763/2011.07.23 in The Tree of Life Web Project, http://tolweb.org/

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