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The side view of Sepia officinalis, or the common cuttlefish.

Cuttlefish

The side view of Sepia officinalis, or the common cuttlefish.

Cuttlefish are marine animals of the order Sepiida belonging to the Cephalopoda class. Despite their name, cuttlefish are not fish but molluscs. Cuttlefish have an internal shell (cuttlebone), large W-shaped pupils, and eight arms and two tentacles furnished with denticulated suckers, with which they secure their prey.

Cuttlefish

Cuttlefish are marine animals of the order Sepiida belonging to the Cephalopoda class. Despite their…

"Diagram of circulatory and excretory systems in a Decapod-like Sepia. 1, Gill; 2, renal sac; 3, afferent branchial vessel; 4, branchial heart; 5, abdominal vein; 6, heart; 7, viscero-pericardial sac (body cavity); 8, genital organ; 9, posterior aorta; 10, "auricle"; 11, glandular appendix of branchial heart; 12, renal appendices of branchial vein; 13, external aperure of kidney; 14, vena cava; 15, anterior aorta; 16, bifurcation of vena cava; 17, reno-pericardial aperture." -Thomson, 1916

Cuttlefish Circulatory and Excretory Systems

"Diagram of circulatory and excretory systems in a Decapod-like Sepia. 1, Gill; 2, renal sac; 3, afferent…

"Diagram of the structure of Sepia. a., Eight short arms around mouth; l.a., one of the two long arms; b., beak of the mouth; c.g., cerebral ganglia, with commissures to the others; E., eye; g., gullet; d.g., digestive gland (the "salivary glands" are not represented); st., stomach; a., anus; sh., shell-sac with sepiostaire; k., kidney; R., reproductive organ; br.h., branchial heart; g., a gill; i.b., ink-bag; m.c., mantle cavity; f., funnel." -Thomson, 1916

Cuttlefish Structure

"Diagram of the structure of Sepia. a., Eight short arms around mouth; l.a., one of the two long arms;…