Mutagenic impact of the biotoxin of veined rapa whelk Rapana venosa (Valenciennes, 1846) (Gastropoda, Muricidae)

Abstract

The invasion of the predatory gastropod mollusk Rapana venosa, known as veined rapa whelk, in the Black Sea and its outspread in many regions of the World Ocean have led to complex structural changes in the communities of bivalve mollusks. When capturing a prey, the adult rapa whelk excretes a biotoxin from the hypobranchial gland that causes severe paralysis of the musculature of bivalve mollusks. Under experimental conditions, it was established that the biotoxin, after the short-term exposure of the fertilized eggs of the mussels Mytilus galloprovincialis to it, has a mutagenic effect, causing chromosomal aberrations in the embryos. The acentric groups of chromosomes, single and multiple chromosome bridges, chromosome lags and polyploidy indicate transformation or destruction of threads of the achromatin spindle in the mitosis anaphase. The chromosome fragmentation and emergence of ring chromosomes in the metaphase and anaphase of mitosis of mussel embryos are the consequence of the partial destruction of chromatin. The underdeveloped shell, anomalous development of D-veligers’ velum, and the changed form of the ‘eye spots’ and hepatopancreas of the larvae at the veliconcha stage result from chromosomal mutations during the embryo development. The mechanism of the rapa whelk biotoxin action on the chromosomal apparatus of mussel embryos is discussed.