Morphological and Molecular Studies of the Rapa Whelk, Rapana venosa (Neogastropoda, Muricidae), from Odesa Bay

Abstract

The gastropod Rapana venosa is a successful worldwide invader occurring in the Black Sea. The aim of this study is to overview specific population features of this mollusk from Odesa Bay through integrative systematic approach by means of morphological and molecular research. For this purpose, individuals of mollusks were collected from the Black Sea and examined using morphological methods: traditional morphometry, which employs linear parameters of shells (height, width, whorl height, whorl width, height of the last whorl) and shell weight, and geometric morphometrics of the shell shape data; for a molecular genetic test, the COI gene region were used. Among all conchological variability, the two morphotypes were defined: the first has a "squat"/"broad" shape – shells have a thick and durable last whorl and a low spire, and the second one – "extended" shape: shells are relatively slender with an elongated high-conical spire. According to the geometric morphometric data R. venosa has statistically significant differences among defined morphotypes (F=4.12, p=0.001); however, the shapes among sexes are not significantly different (F=1.13, p=0.318). No genetic diversity, neither novel haplotypes were revealed by the molecular analysis: in Odesa Bay, the haplotype occurring also in other regions of invasion across the world are present.

Keywords

• coi
• geometric morphometric analysis
• invasive species
• phylogenetics
• papa whelk
• shell morphology