Shell colour variation in Bullia digitalis, a sand‐dwelling, intertidal whelk (Gastropoda: Prosobranchia)

JOSEPH HELLER*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

Bullia digitalis is an intertidal whelk that lives on sandy beaches in South Africa. It is highly variable in shell colour, with individuals varying from white to dark brown. This paper describes shell colour variation of B. digitalis at seven sites, along a 230 km coastline east of the Cape Peninsula. Seven colour forms were found: striped, violet, banded violet, banded brown, orange, pale yellow and white. These forms are probably genetically determined morphs. The striped form is the most common at all sites, constituting 53–62% of each sample. The violet is the second most common morph. Its frequencies are remarkably stable at 15–17%. The striped form blends well into the sandy environment and may therefore be of considerable cryptic value in concealing B. digitalis from predators. The violet form is highly conspicuous. Its stable frequency throughout the study area may represent a genetic balance that is not relevant to any visual advantages of the violet colour.

Original languageEnglish
Pages (from-to)247-258
Number of pages12
JournalBiological Journal of the Linnean Society
Volume46
Issue number3
DOIs
StatePublished - Jun 1992

Keywords

  • Bullia
  • Colour
  • intertidal
  • polymorphism
  • sand
  • selection
  • snail

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