Cephalopod mollusks, particularly the octopods, are considered by many to be one of the most highly evolved invertebrate groups. Their anatomy is quite different from that of the vertebrates in many ways; but in some aspects (e.g., ocular anatomy), the development and anatomy are quite similar. The unusual appearance of the octopods as well as the plethora of myths and legends that surround them have made them very popular with zoo and aquarium visitors. Currently, captive populations of octopods mainly consist of wild-caught specimens. The difficulty of gender determination in immature specimens, their relatively short lifespans, their relative abundance in the wild, and their ease of capture have historically made captive propagation a relatively low priority. With few exceptions,1 very little has been published about their basic anatomy and physiology in the veterinary medical literature. Thus, our current understanding of the etiology, onset and treatment of their diseases is quite rudimentary.
Ultrasonography was used in the present study to characterize the anatomy of their internal organs and organ systems including gills, eyes, digestive system, reproductive organs and central nervous system. Eight animals of two species were examined (Octopus vulgaris, Enteroctopus dofleini) using both mobile and static ultrasonographic images. Ultrasonographic results were verified by postmortem preparations of either wild-caught animals or animals obtained from aquaria.
Ultrasonography was useful in characterizing several anatomic features unique to the Octopodae, such as the central nervous system (central ganglion), which encircles the esophagus, the hepatopancreas or ‘digestive gland,’ and the unpaired gonads. The relatively large spermatophores found in the Needham’s sack of the males are also readily visualized. Overall, ultrasonography provided a fairly detailed view of the internal gross anatomy. As such, sonographic imaging should be able to facilitate the creation of reliable protocols for the physical examination of living octopods. In our hands, ultrasonography proved to be a useful diagnostic tool in the general assessment of the overall nutritional status, health status, gender and reproductive state of individual specimens.
Present and future results with sonographic imaging may contribute to the improvement of the quality of both health and reproductive management of these keystone aquatic animals.
1. Stoskopf, M.K., and B.S. Oppenheim. 1996. Anatomic features of Octopus bimaculoides and Octopus digueti. J. Zoo Wildl. Med. 27:1–18.