Quantitative differences among the brains of cephalopods

Abstract

The relative sizes of 30 lobes of the brains of 63 species of cephalopods have been compared. Some of the observed differences could be related to the way of life of the animal and others to the taxonomic relationships. The octopods are separated from the decapods by their larger brachial and other suboesophageal lobes, larger inferior frontal systems and smaller optic lobes. Vampyroteulhis lies somewhat between these two main groups. The vertical lobe system is large in sepioids and loliginids, smaller in decapods from deeper water, but large in Vampyroteuthis. In octopods, it is large in the typical epibenthic forms but smaller in those from deeper water and very small in cirrates. The inferior frontal system is very large in epibenthic octopods and Benthoctopus and in cirrates, but smaller in epipelagic and bathypelagic forms. The optic lobes are larger in decapods than in octopods from comparable depths and are especially large in deep‐sea decapods. They are larger in epipelagic octopods than in the typical benthic forms. The photosensitive vesicles vary by nearly two orders of magnitude. They are very small in squids living in surface waters, larger in mesopelagic forms and enormous in some cranchiids and in Balhyteuthis. In Histioteulhis, the side with the larger eye had an optic lobe twice as big as that on the side of the smaller eye, but with only slight differences in other parts of the brain. In the octopods, the inferior frontal system was generally large, being concerned with the tactile memory system, and tends to be inversely related to the size of the optic lobe.

A biphasic memory curve in the chambered nautilus,Nautilus pompiliusL. (Cephalopoda: Nautiloidea)

“…This finding is particularly interesting given the absence of a vertical lobe complex in nautilus, and suggests that both procedural artefacts and the particular neuroanatomical structure of nautilus may have combined to produce the short retention times we observed. In coleoids the vertical and subfrontal lobe complexes are necessary for visual and tactile memory, respectively (Boycott and Young, 1955;Sutherland, 1963;Maddock and Young, 1987;Young, 1961;Young, 1991;Fiorito and Chichery, 1995;Robertson et al, 1996). Nautilus lacks both these dedicated regions (Young, 1965) and it seems likely that this pliesiomorphic neuroanatomy retained by N. pompilius would affect its capacity for memory storage.…”

The Evolution of Flexible Behavioral Repertoires in Cephalopod Molluscs

“…The VL complex in the common European cuttlefish is approximately 24% of the total brain volume, whereas the VL complex in common octopus occupies about 13% of the total brain volume ( fig. 1 B) [Maddock and Young, 1987]. Relative volume of neural resources is correlated with learning in cephalopods; increases in volume of the vertical lobe during cuttlefish development are correlated with a corresponding improvement in learning for example [Dickel et al, 1997].…”

“…The vast majority of cephalopods (i.e., other than nautiluses) utilize specialized skin cells (chromatophores, iridophores, leucophores and papillae) to effect visual and textural camouflage to avoid visual predators, hunt prey, and to signal with conspecifics [Adamo and Hanlon, 1996]. Finally, cephalopods are endowed with large, sophisticated visual and nervous systems, contributing to their efficiency in predation and competition with marine vertebrates and invertebrates of all types [Packard, 1972;Maddock and Young, 1987;Aronson, 1991;Hanlon and Messenger, 1996]. Cephalopods are capable of sophisticated higher-order learning capabilities [detailed below and reviewed in Sanders, 1975;Boyle, 1986;Hanlon and Messenger, 1996, p. 132-147].…”

“…( B ) Respective sizes of the vertical lobe complex (VL), inferior frontal complex (InFF) and Optic Lobe (OL) for representative species of the major cephalopod types in the classification. The values were calculated from the comparative data published in Maddock and Young [1987] (reproduced with permission from Wiley-Blackwell). Those data describe the volume of brain regions in proportion to the total volume of the central brain (excluding the optic lobes).…”

Treatise Online, no. 17, Part M, Chapter 3: Anatomy of Recent forms

“…The shape and form of the cephalic cartilage tends to follow that of the central nervous system. The numerous lobes of the brain show differences in size and shape between genera and even species (J. z. young, 1971;MaddoCk & young, 1987), and these differences may be reflected in the cephalic cartilage. Histological sections of numerous coleoid species reveal the cephalic cartilage to be hyaline or reticulate (Fig.…”