Fig. 3. Ultrasound images illustrating the spatial relationships between organs in a non-dissected cuttlefish. The dorsal mantle is always at the top of the image, and the ventral mantle is always at the bottom. Non-cardiovascular organs are abbreviated with lower case letters. (A) Transverse section through the anterior mantle. (B) Midsagittal section showing organs from planes 1 and 2 of Fig. 1 (see supplementary material, Movie 1). The head is towards the right. (C) Transverse section through the branch point and the efferent branchial vessels (plane 3, Fig. 1; also see supplementary material, Movie 2). (D) An oblique transverse section through the ventricle. Organs visible on the right are posterior to those on the left. This roughly corresponds to plane 4 in Fig. 1. Nidamental glands (ng) are present only in females. AU, auricle; AVC, anterior vena cava; BP, branch point; cf, collar flap; dg, digestive gland; EBV, efferent branchial vessel; f, funnel; int, shared course of the intestine and ink sac duct; LVC, lateral venae cavae; m, mantle; V, ventricle. All scale bars are 2 cm.