Hydrobia ulvae. Height in mm and sex, top left to bottom right : 6.5 f, 5.5 m, 5 f, 5.5 f, 4.5 m, 4.4 m. Upper Dee Estuary, salinity 29 p.p.t. Majority; shallow sutures and flattened whorls. A few (2 bottom right); deep sutures & small but adult.
Hydrobia ulvae. Height in mm and sex, top left to bottom right : 6.5 f, 5.5 m, 5 f, 5.5 f, 4.5 m, 4.4 m. Upper Dee Estuary, salinity 29 p.p.t. Majority; shallow sutures and flattened whorls. A few (2 bottom right); deep sutures & small but adult.
Hydrobia ulvae. Height in mm and sex, top left to bottom right : 6.5 f, 5.5 m, 5 f, 5.5 f, 4.5 m, 4.4 m. Upper Dee Estuary, salinity 29 p.p.t. Majority; shallow sutures and flattened whorls. A few (2 bottom right); deep sutures & small but adult.