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, although the size of the sucker relative to the swimming fin is very small when compared with the sucker in 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 (see title illustration)
   2. Like in 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 (see image of Carinaria galea below)
2. Shell
   1. Present in adults and either cap-shaped (Carinaria and Pterosoma), covering the viscera and gills (see image below), or microscopic (Cardiopoda), embedded in visceral nucleus dorsum
      

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      Figure. Stalked visceral nucleus and gills covered by shell in Carinaria galea.  Digestive gland dark brown and testis pink. 

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

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      Figure. Protoconch at apex of adult shell in Carinaria galea. 

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 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).

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: Stanford University Press. 259 pp.

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