Carinariidae Blainville 1818

Introduction

The bodies of carinariids, like those of pterotracheids, are greatly enlarged by comparison with the microscopic atlantids. Also like the pterotracheids, the body in most species is elongated and cylindrical, and is divisible into three regions (proboscis, trunk and tail). A reduced shell is present, growing out of the larval shell after metamorphosis. The adult shell is either cap-shaped, covering the viscera, gonads, heart and gills (Carinaria and Pterosoma) or is microscopic, modified only slightly from the larval shell, and embedded dorsally in the visceral nucleus (Cardiapoda).  A fin sucker is present in both sexes (with the exception of Cardiapoda richardi, which lacks a sucker in females) and the size of the sucker relative to the swimming fin is very small in comparison with the atlantids.

Brief Diagnosis

Heteropod molluscs with:

• Body elongated and basically cylindrical, divided into proboscis, trunk and tail
  
• Viscera compacted into a stalked visceral nucleus
• Shell cap-shaped, covering the viscera and other organs, or microscopic, embedded in the dorsal part of the visceral nucleus.

Characteristics

1. Body morphology
   1. Body elongate and basically cylindrical, except in Pterosoma which has a broad and disc-shaped trunk
   2. Like pterotracheids, body divided into proboscis, trunk and tail regions
      

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      Figure.  Body regions in Carinaria japonica. ©

   3. Visceral nucleus dorsal and stalked
2. Shell
   1. Adult shell macroscopic in Carinaria (cap-shaped) and Pterosoma (flattened) and covering the viscera and gills, or microscopic in Cardiapoda and embedded in dorsal tissues of the visceral nucleus
      

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      Figure. Stalked visceral nucleus and shell in Carinaria galea (left) and Pterosoma planum (right).  In the left image, the digestive gland is dark brown and testis is pink. ©
      
      
      
      Figure. Drawings of the microscopic adult shell in Cardiapoda placenta, viewed from the right side and aperture. Shell diameter (left image) about 0.8 mm. Drawings modified from Tesch (1949).
      

   2. Protoconch located at apex of adult shell (teleoconch) in Carinaria and Pterosoma
      
      

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      Figure. Enlarged view of apical region of shell in Pterosoma planum. ©

   3. Larval shell globular; umbilicus open with radiating striae; aperture oval with smooth outer lip
      
      

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      Figure. Larval shell of Carinaria galea. Shell viewed from right side, left side, and aperture, respectively. Note the striae radiating from the umbilicus (middle image) and the operculum inside the shell aperture (right image). Scale bar = 250 µm (applies to all images). ©

3. Swimming fin and sucker
   1. Fin sucker small and located on the posteroventral margin of the swimming fin; present in both sexes
      

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      Figure. Swimming fin and fin sucker in male Carinaria japonica. Penial appendage and penis dorsal to swimming fin. ©

4. Radula
   1. Shape broadly triangular, with a relative low and limited number of tooth rows (34-44)
   2. Central (rachidian) tooth broad with a low base, three cusps, and  prominent posterolateral processes
   3. Lateral teeth with a small, curved cusp on the inner accessory plate
   4. Marginal teeth monocuspid
      

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      Figure. Radula of Carinaria lamarcki. Left: low magnification view (scale bar = 200 µm. Right: high magnfication view (scale bar = 20 µm). © G. Richter.

Comments

Most species are in the genus Carinaria; Pterosoma is monotypic and there are two species of Cardiapoda. The genera can be distinguished by the following characters:

References

Lalli, C. M. and R. W. Gilmer. 1989. Pelagic snails. The biology of holoplanktonic gastropod snails. Stanford University Press, Stanford. 259 pp.

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

Seapy, R. R. and C. Thiriot-Quiévreux. 1994. Veliger larvae of Carinariidae (Mollusca: Heteropoda) from Hawaiian waters. Veliger 37: 336-343.

Tesch, J. J. 1949. Heteropoda. Dana Report 34, 53 pp., 5 plates.