The American whelk tingle, Urosalpinx cinerea (Say), on British oyster beds

Abstract

The American whelk tingle, Urosalpinx cinerea (Say), a gastropod enemy of oysters, has been introduced to Britain with American oysters and is now established in the rivers Blackwater, Colne, Crouch and Roach in Essex and on the Kentish Flats off Whitstable. Evidence available concerning the migratory powers of Urosalpinx is conflicting, but it is probable that migration is of local significance only in the spread of this pest. To infest new areas tingles or their spawn must be transported by human or other agency, for Urosalpinx has no free-swimming larval stage, the eggs being deposited in capsules from which fully formed young tingles emerge.Females of Urosalpinx grow more quickly than males and reach a larger size. In males the annual increase in shell height never exceeds 0·2 cm. after the first 3 years, and is generally rather less. In females an annual increment of 0·2 cm., or slightly more, is general up to the age of about 7 years, after which it gradually falls. Males and females of the same age differ in height by about 0·25 cm. Growth marks are frequently to be seen on the shell and are of value in assessing growth rates. In both sexes a maximum age of 13–14 years may be reached. Urosalpinx reaches a much greater average size in Britain than in its natural habitat on the Atlantic coast of the U.S.A.Females may deposit some spawn during the first 2 years of life, but the amount is insignificant in relation to the production of older tingles. Spawning begins when the water temperature in its seasonal rise reaches 12° C. Adult females may deposit an average of 25 egg capsules at a single laying, but it is possible that further capsules are deposited later in the season. The bulk of the spawn is deposited in May and June on British beds, but a few freshly laid capsules may sometimes be found in August and September. The average period of incubation is about eight weeks. Young tingles usually begin to emerge early in July. The average number of young emerging from each capsule is 11–74. Urosalpinx appears to be more prolific on British oyster beds than in America.