Observations on the functional anatomy of the Ommastrephid, Illex Illecebrosus (Leseur, 1821) (Coleoidea: Cephalopoda), with emphasis on musculature and the blood vascular systemQuantitative aspects of the food of Littorina Littorea (Linnaeus)

Bradbury, Helen Elizabeth (1970) Observations on the functional anatomy of the Ommastrephid, Illex Illecebrosus (Leseur, 1821) (Coleoidea: Cephalopoda), with emphasis on musculature and the blood vascular systemQuantitative aspects of the food of Littorina Littorea (Linnaeus). Doctoral (PhD) thesis, Memorial University of Newfoundland.

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Abstract

The ommastrephid Illex illecebrosus, has escaped analysis by anatomists for the almost 150 years since its first description by Lesueur in 1821. During the mid-1880's, A. E. Verrill, in his studies on Northeastern Atlantic cephalopods, gave excellent descriptions, with detailed illustrations of this particular oegopsid. Also incorporated in Verrill’s descriptions are recorded observations on certain behavioural aspects such as the feeding and colour changes of this squid. It was for Leonard Williams (1909) to give zoologists an accurate and detailed study of the anatomy of a decapod cephalopod, the species being Loligo pealei Lesueur. This work has since become the standard source of squid anatomy, particularly in North America. Too often, however, squid structure and function is interpreted on basis of knowledge of octopods or sepioids, whether it applies or not. -- Wherever possible, this thesis departs in large measure from previous squid anatomical studies in that it incorporates functional aspects of the anatomy with gross and microscopic structural features of selected organs and organ systems of lllex illecebrosus. -- The musculature of the mantle complex, the hyponomal complex and the brachial cone complex are elucidated and described from a functional viewpoint. Greatest effort was made in the use of a variety of techniques to trace the blood vascular system and observe its several parts in vivo. The system, really a double system, is closed and blood always passes through endothelial lined vessels. Consideration was also given to the cartilaginous and structural skeletal features of the squid, as well as gross, microscopic and in vivo anatomical studies of the alimentary canal and its associated organs. These morphological investigations are enhanced by related behavioural investigations conducted primarily on locomotion and feeding. -- The results of these studies are the basis of discussion on the molluscan structural nature of the squid, its divergence from the basic ancestral molluscan body plan, and subsequent evolution into a pelagic oceanic niche.

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