Carinaria challengeri Bonnevie 1920

Introduction

Carinaria challengeri is a small species (to 40 mm body length). Except for the presence of a pair of pigmented, hemispherical structures on the ventral surface of the tail, C. challengeri shares its external morphology most closely with C. lamarcki. Like the latter species, its shell seen in side view is broadly triangular, with a height to basal length ratio of 0.5, and the tail is small with a low dorsal crest.

Brief Diagnosis

A species of Carinaria with:

• Body length up to 40 mm
• Viewed laterally, shell broadly triangular in shape, with a height to basal length ratio of 0.5
• Tail small, with a low dorsal crest and a ventral pair of pigmented, hemispherical structures of unknown function
  

Characteristics

1. Body morphology
   1. Proboscis short and thick, continuous with well-developed trunk
   2. Tail short with a low dorsal crest
   3. Pair of reddish-brown, hemispherical structures located posteriorly on the tail, on either side of the ventral midline
      
      

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      Figure. Left: close-up of Carinaria challengeri tail (from title illustration). Note coloration and location of the reddish-brown "claspers". © Alejandro de Vera. Right: Drawing of tail of C. challengeri, with details of the pair of hemispherical folds of tissue. Scale bar = 0.5 mm. (drawing from Richter and Seapy, 1999, modified from Bonnevie, 1920). 

   4. Additional differences between this species and C. lamarcki were reported by Pafort-van Iersel (1983): visceral nucleus darker and on a smaller stalk; cutis thinner and with more numerous and smaller tubercles; retinal base of eyes more darkly pigmented; and, tentacles more strongly developed, with the left one distinctly longer than the right one.
2. Shell morphology
   1. Viewed from right side, shell broadly triangular with height to basal length ratio of 0.5.
   2. Keel moderately low
      
      

      Click on an image to view larger version & data in a new window

      
      

      Figure. Close up of visceral nucleus and shell of Carinaria challengeri, viewed from the right side of the body. Note the grown digestive gland extending into the coiled protoconch.© Alejandro de Vera

Comments

Carinaria challengeri was originally described as a variety of C. lamarcki by Bonnevie (1920). This subspecific designation was followed by subsequent authors (see Spoel, 1976) until Pafort-van Iersel (1983) showed that the geographic ranges of the two varieties (termed "formae" by Spoel, 1976) overlapped along a north-south transect (along 30º W. Longitude) in the middle North Atlantic Ocean; C. lamarcki forma lamarcki between 32° and 49ºN, and C. lamarcki forma challengeri between 40º and 45ºN. Thus, the range of the latter is sympatric with the northern part of the range of the latter, and since no specimens were collected that were morphologically intermediate within the overlapping range, Pafort-van Iersel concluded that they are distinctive and separate species.

Bonnevie (1920) termed the pair of pigmented structures on the tail ventrum "claspers". However, Tesch (1949) stated that the structures have little to no musculature and that they probably could not function in mating. Bonnevie also considered specimens of C. challengeri to represent juveniles of C. lamarcki because of their small size (30-40 mm maximal body length) and of her observation that while the "claspers" were present in small animals (<30-40 mm), the structures were not present in larger animals. Recognition of C. challengeri as a separate species, however, negates her conclusions.

References

Bonnevie, K. Heteropoda. 1920. Report on the Scientific Results of the "Michael Sars" North Atlantic Deep-sea Expedition 1910, 3(2)(zoology): 3-16.

de Vera, A., R. R. Seapy, and F. Hernandez. 2006. Heteropod molluscs from waters around the Selvagens Islands (Gastropoda: Carinarioidea). Vieraea 34: 33-43.

Pafort-van Iersel, T. 1983. Distribution and variation of Carinariidae and Pterotracheidae (Heteropoda, Gastropoda) of the Amsterdam Mid North Atlantic Plankton Expedition 1980. Beaufortia 33: 73-96.

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

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