Cardiapoda richardi Vassière 1904

Introduction

Cardiapoda richardi is distinguished from C. placenta by the following: small adult body size (to about 30 mm); eight gills located at the entrance to the mantle cavity; lens of the eye rests in a depression in a black base of hemispherical shape; fin sucker present only in males; tail with a low dorsal crest, a retractable brown, membranous structure on the mid-ventral surface, and a reddish-brown, filamentous tail extension; and a radula with the central rachidian tooth bearing three pointed cusps, of which the lateral cusps are shorter than the median one (in C. placenta, the pointed cusps are of equal length).

Brief Diagnosis

A species of Cardiapoda with:

• Eight gills located at the entrance to the mantle cavity
  
• Lens of eye rests in a depression in a solid black base of hemispherical shape
• Fin sucker only in males
  
• Tail with a low dorsal crest
• Ventral surface of tail with a retractable, brown membranous structure
  
• Tail terminates in a reddish-brown, filamentous extension
• Central rachidian tooth bears a middle portion with three, pointed cusps, of which the lateral cusps are shorter than the median cusp

Characteristics

1. Body morphology
   
   1. Eight gills located at entrance to mantle cavity
   2. Tentacles elongate and of equal length
      
      

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      Figure. Frontal view of Cardiapoda richardi, illustrating the elongate tentacles anterior to the eyes and projecting laterally from the base of the proboscis. © L. Madin

   3. Numerous, small white spots cover the body. In side profile the spots appear elevated, like very low tubercles (click on the photo below for enlarged view).  Each spot appears to consist of a cluster of minute, white specks
      
      

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      Figure. Right side of body in Cardiapoda richardi. Small, white spots cover the body. © L. Madin

   4. Lens of eye rests in a cup-like depression in a large, pigmented base
      
      

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      Figure. View of right side of head region and eye in Cardiapoda richardi. © L. Madin

   5. Tail with a low dorsal crest, a brown membranous structure or expansion (see first title illustration) that can be retracted into an elongate mid-ventral groove (see below), and a terminal reddish-brown, filamentous extension that is highly contractile (compare the length of the tail extension in the two title illustrations). Thiriot-Quiévreux (1975) reported the presence of the membranous structure on the tail in larvae of the species
      
      

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      Figure. Ventro-lateral view of tail in Cardiapoda richardi. Note the low dorsal crest and the elongate indentation on the mid-ventral surface into which the brown membranous structure is retracted. © L. Madin
      

2. Radula
   1. The radula of a 9-mm juvenile Cardiapoda richardi was illustrated by Thiriot-Quiévreux (1975; see below). The central rachidian tooth consists of a middle region with three cusps that are close together at the base; the median one is of moderate length and has a broad base, the left one is about one-half the length and basal width of the median one, and the right one is very short.
      

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      Figure.  Scanning electron micrographs of the radula from a juvenile Cardiapoda richardi at low (left) and high (right) magnfication. Photographs from Thiriot-Quiévreux (1975, Fig. 5D,E). © 1975 C. Thiriot

   2. Adult radular morphology is not recorded in the literature. The photograph below is from a 20-mm individual (provided by Orso Angulo, Universidad Autónoma de Baja California Sur). In comparison with the juvenile radula above, the median cusp of the central rachidian tooth remains the longest of the three and the side cusps are noticeably shorter and are comparable in length. The difference in length of the median and side cusps contrasts with their comparable length and the outward flair by the side cusps in C. placenta (see the C. placenta page).
      

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      Figure. Photograph of central rachidian teeth in the radula of a 20-mm adult  Cardiapoda richardi. © Orso Angulo

3. Shell
   1. Larval shell globular, consisting of 3.25 whorls. Spire whorls smooth except for a pair of elevated spiral ridges on the second whorl; also reported from C. richardi from the North Atlantic by Thiriot-Quiévreux, 1975). Umbilicus open, with about 13 elevated, radiating striae on wall. Aperture wide, slightly greater than 1/2 shell diameter
      

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      Figure. Scanning electron micrographs of the larval shell of Cardiapoda richardi, viewed from the right side, left side, and aperture (left, center and right, respectively. Shell diameter = 0.6 mm. © R. R. Seapy

   2. Adult shell not characterized in the literature. Spoel (1976:158) stated "A shell is never described for this species, but a coil in the liver top of small specimens proves that a small shell must be present also after the veliger stage"
   3. Following metamorphosis, the teleoconch develops directly from the aperture of the larval shell (see the two figures below)
      

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      Figure. Early post-metamorphic 5.7-mm Cardiapoda richardi. Note the transparent larval shell (enclosing the coiled digestive gland and the heart and gills) and the conspicuous keel of the teleoconch extending to the upper left. © 2008 Orso Angulo

   4. Scanning electron micrograph of the shell from the 5.7 mm individual in the above photograph (both images graciously provided by Orso Angulo, Universidad Autónoma de Baja California Sur), which clearly shows that the adult shell in Cardiapoda richardi is strikingly different from that in C. placenta (compare with the scanning electron micrograph of the adult shell of C. placenta). Here, the teleoconch arises as a direct extension from the larval shell aperture and possesses a prominent, short keel that appears at  the beginning of the teleoconch; similar to that seen in Carinaria.
      

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      Figure. Shell from a 5.7-mm Cardiapoda richardi, viewed from the right side. Note that the outer part of the dorsal keel is broken off (compare with the photograph of the animal above). Scale bar = 0.5 mm. © 2008 Orso Angulo

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.

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

Tesch, J. J. 1949. Heteropoda. Dana Report 34. 54 pp.

Thiriot-Quiévreux, C. Observations sur les larves et les adulte de Carinariidae (Mollusca: Heteropoda) de l'Océan Atlantique Nord. Marine Biology 32: 379-388.