Carinaria cristata (Linnaeus 1766)

Introduction

Carinaria cristata attains the largest body size (≥ 680 mm body length) of all heteropods. The proboscis is short and the trunk inflated. The tail is larger (in proportion to the trunk and proboscis) than in any other species of Carinaria, with a tall dorsal crest that slopes posteriorly and leads to a whip-like posterior portion. In large adults the dorsal surface of the tail develops a pattern of brown pigmentation and the posterior part of the tail is brown. The shell is triangular in side view, with a height to basal length ratio of 0.8-1.0. With increasing size, the apical portion of the shell slopes posterioly. The keel is very low, increasing gradually in height towards the shell aperture.

Brief Diagnosis

A species of Carinaria with the following characteristics:

• Reaches the largest body size among all the species of heteropods (≥680 mm)
  
• Proboscis short and trunk inflated
  
• Tail very large and elongate, with a tall dorsal crest
  
• In large animals, dorsal surface of tail with distinct pattern of brown pigmentation
• Shape of shell triangular in side profile, with a very low keel
  

Characteristics

1. Body morphology
   1. Proboscis short; trunk inflated with a thick cutis
      
   2. Viewed dorsally, eye shape triangular
   3. Tentacles present anterior to eyes; right one smaller than the left in older individuals, but in younger animals the rignt one is somewhat longer than the left (Tesch, 1949)
      
   4. Visceral nucleus stalk short, with the result that the visceral mass and shell are positioned lower than in other species of Carinaria
      
   5. Tail very large and elongate; length greater than that of the combined proboscis and trunk (to 175%; see figure below)
   6. Tail crest tall, tapering posteriorly to a whip-like posterior region that is triangular in cross-section
      
   7. In older individuals, dorsal surface of tail crest brown with short, ventrally-directed brown bands, and posterior section of tail brown (contrast the tails of the animals in the title illustration and in the figure below)
      
      

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      Figure. Largest specimen (body length ≥ 680 mm) of Carinaria cristata recorded to date. Proboscis and trunk of specimen appear to be contracted; thus, the actual body length is undoubtedly greater than 680 mm. Specimen missing its visceral nucleus and shell at the time of collection by hand from the ocean surface outside Palmyra Atoll. © 2007 John Svenson 
      

2. Shell morphology
   1. In side view shell triangular, with apical part of the shell sloping posteriorly. Height to basal length ratio of shell = 0.8-1.0 (Okutani, 1961)
      
   2. Keel very low and increases gradually in height with proximity to shell aperture (see middle photograph below)
      
      

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      Figure. Three shells of Carinaria cristata of decreasing size. Apical portion of shell on left missing. Photographs from Tesch (1906, Plate 9, Figs. 38-40). Scale bars based on  shell sizes given in figure legends. © 1906 J. J. Tesch
      

      

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      Figure. Shell of Carinaria cristata, viewed from right side. Shell height = 22.6 mm. © 1961 Takashi Okutani

3. Radular morphology with a central (rachidian) tooth bearing three pointed cusps; typical of carinariids
   
   

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   Figure. Drawing of a section of the radula in Carinaria cristata. To distinguish between the shapes of the two marginal and the single lateral teeth that are present on both sides of the central tooth in each tooth row, marginal teeth are illustrated on the left and lateral teeth on the right of the central tooth row. © 1976 S. van der Spoel
   

   

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   Figure. Anterior end of proboscis with the mouth held open to show the radula. The lighter- colored central teeth are flanked, on either side, by the darker-colored, overlapping marginal and lateral teeth. © 2007 John Svenson

References

Okutani, T. 1961. Notes on the genus Carinaria (Heteropoda) from Japanese and adjacent waters. Publications of the Seto Marine Biological Laboratory 9: 333-352.

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

Tesch, J. J. 1906. Die Heteropoden der Siboga-Expedition. Monograph 51, 112 pp, 14 plates. E. J. Brill, Leiden.

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