Morphology of the digestive system of Antarctic nototheniid fishes
Received: 24 November 1995/Accepted: 27 January 1996 |
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Authors: | J T Eastman A L DeVries |
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Institution: | (1) Department of Biological Sciences and College of Osteopathic Medicine, Ohio University, Athens, OH 45701-2979 USA fax: 614-593-0300; e-mail: eastman@ouvaxa.cats.ohiou.edu, US;(2) Department of Molecular and Integrative Physiology, University of Illinois, Urbana, IL 61801-3704, USA, US |
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Abstract: | Although Antarctic nototheniid fishes are ecologically diverse, this survey of aspects of the anatomy and histology of the
digestive system of 25 species showed little interspecific variation in the structure of this system. The gastrointestinal
tract is illustrated and all but two species shared a similar pattern of intestinal coiling. The average number of pyloric
ceca in most nototheniids was 6–7, with means ranging from 3.0 to 7.6. Reduction in the number of ceca was evident in both
phyletically basal and derived species. Intraspecific variation in cecal number was nonexistent in some species, but in others
ranged between 2 and 4 ceca. Numerous hepatic ducts, contained within the liver parenchyma, converged on the neck of the gall
bladder. The bile duct penetrated the gut wall near the origins of the most dorsally located ceca. The terminal portion of
the pancreatic duct paralleled, but did not join, the bile duct. The exocrine pancreas was diffuse and present in intercecal
and splenic mesenteries, in the wall of the gall bladder and in tissue near the walls of the bile and pancreatic ducts. Unlike
many other teleosts, the liver of nototheniids usually lacked pancreatic exocrine tissue. Nototheniids had a principal pancreatic
islet (Brockmann body) and 2–3 accessory islets. Peritoneal melanism was a convergent feature of species living in the water
column and probably served to screen the bioluminescence from gut contents. |
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