Evaluation of the Digestive Gland in Disease and Health from the Common Cuttlefish (Sepia officinalis)
Occasionally outbreaks occur of unexpected deaths in captive and laboratory reared cuttlefish. From a review of tissues over the past 10 years from the National Resources Center for Cephalopods the digestive gland was a useful organ to evaluate gross and histologic lesions. Findings from these tissues helped in making management decisions about colony animals.
The digestive gland (also known as the midgut gland or hepatopancreas) is the largest gland of the cephalopod body. The gland has many functions of which some are not completely understood. The known functions include synthesis and secretion of digestive enzymes; resorption and metabolism of nutrients; synthesis and storage of lipids, glycogen, pigments, vitamins, and protein bound Fe, Cu, Ca, and non-physiologic metals.1 The gland is also responsible for excretion and rejection of waste products from digestion and cellular metabolism. The digestive gland is paired; having a capsule composed of collagenous and muscle fibers which encloses tubular structures. The two types of cells that are within the tubular structure are basal cells and digestive cells. Basal cells have a pyramid-like form and are attached to a thick basal lamina that borders the blood sinus. Digestive cells are also attached to the basal lamina, but their microvillar border contacts the lumen of the tubules. Digestive cells are columnar in shape.
In the disease state, the digestive gland can respond differently to a variety of etiologic agents including poor environmental conditions, infectious agents, trauma, and nutritional quality. The histopathologic response to a toxin such as increased environmental copper levels was widespread multifocal necrosis of the digestive gland. This lesion was also found when a diet of certain types of fish were fed to cuttlefish. Many of the infections involving Sepia were caused by Vibrio spp. The digestive gland lesions usually involved multifocal necrosis or locally extensive necrosis often times with an inflammatory cell response. Differentiation of infectious lesions versus toxic lesions using digestive gland morphologic evaluations may serve as a useful tool in the management of cuttlefish production colonies.
This work would not have been possible without the help of Drs. Philip Lee and Bernd Budelmann and Philip Turk and John Forsythe, National Resource Center for Cephalopods, the University of Texas Medical Branch at Galveston, Galveston, Texas.
1. Budlemann BU, Schipp R, von Boletzky S. Cephalopoda. In: Harrison FW, Kohn A, eds. Microscopic Anatomy of Invertebrates, volume 6A. New York, NY: Wiley-Liss Inc.; 1997:200–207.