Mitotic chromosomes of Gyrinidae, arranged as karyotypes. a G. minutus, ♂, Isle of Lewis, testis, plain (Giemsa stained) b G. caspius, ♂, Lydd, mid-gut, plain c–e G. paykulli, ♂, Catfield Fen, mid-gut c plain d partially C-banded, still showing chromosome morphology, e the same nucleus fully C-banded, much chromosome morphology lost f, g G. distinctus fairmairei, ♂, Kuwait, testis, plain h, i G. marinus, ♂, Lydd, testis h plain i the same nucleus C-banded j, k G. opacus, Sweden, mid-gut, plain j ♂ k ♀ l, m G. opacus, Greenland, plain l ♂, mid-gut m ♀, ovary n, o G. natator, ♂, Lough Briskeen, mid-gut n plain, o the same nucleus C-banded p–s G. substriatus, ♂, testis, plain p, q Kennington r, s Isle of Lewis t, u G. suffriani, ♂, Catfield Fen, mid-gut, Giemsa stained t plain, u with spontaneous C-type banding v, w G. urinator, ♂, Tilford, testis v plain w the same nucleus C-banded x, y Orectochilus villosus, ♂, Stonesfield, mid-gut x plain, y the same nucleus C-banded. The scale line to the right of the autosome rows of u, v represents 5 μm. The vertical lines on the left-hand side link karyotypes of the same species.