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Cystiscus minutissimus (Tenison-Woods, 1876)

Diagnosis: Shell small, colourless transparent to opaque white; spire concealed by lip callus; outer lip thickened internally, smooth; external varix absent; siphonal notch absent; posterior notch absent; lacking collabral parietal callus ridge; columella with two or three strong plaits, sometimes with several weaker lirae above.

Size: About 3 mm in length.

Distribution: Australian Museum collection: central Queensland to eastern Tasmania , 3-200 metres.  Literature: Tasmania , Victoria

Comparison: This species is oval in outline, with the outer lip rising above the spire.

Synonymy: Marginella pumilio Tate & May; Marginella nielseni Laseron, 1948 (Hewish in Wilson, 1994)

Remarks: The illustrated specimen (Fig. 1) is one of the three syntypes of  M. nielseni Laseron, 1948 from off Batemans Bay in 25-60 fathoms (46-110 m).  Laseron described his species as having three plaits, which is so for two of the syntypes, but the third specimen (figured here) has two strong plaits and several weaker lirae above. The figured shell is colourless transparent - the brown colour is the dried animal inside.

   Cystiscus minutissimus of one of the few Australian cystiscids that has been studied in detail. Murray (1970) reported the species living in abundance on the bryozoan Amathia bisericata Krauss, 1837, at a depth of 13 metres in Westernport , Victoria .  She kept specimens living in the laboratory on this bryozoan where they fed, paired, spawned and lived for up to six months. The mollusc carries out its life cycle on the bryozoan; spawning takes place throughout the year.  Tough walled, transparent egg capsules are deposited singly on the stem of the bryozoan, each containing one red-coloured egg.  After six or seven weeks one well-developed juvenile crawls from each capsule.

Fig. 1: Off Batemans Bay, NSW,  in 25-60 fathoms (46-110 m). Syntype of Marginella nielseni Laseron, 1948 (C.103364)


Copyright Des Beechey 2004