Osmoregulation in elephant fish Callorhinchus Milii (Holocephali), with special reference to the rectal gland

Hyodo, Susumu, Bell, Justin D., Healy, Jillian M., Kaneko, Toyoji, Hasegawa, Sanae, Takei, Yoshio, Donald, John and Toop, Tes 2007, Osmoregulation in elephant fish Callorhinchus Milii (Holocephali), with special reference to the rectal gland, Journal of experimental biology, vol. 210, pp. 1303-1310, doi: 10.1242/jeb.003418.

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Title Osmoregulation in elephant fish Callorhinchus Milii (Holocephali), with special reference to the rectal gland
Formatted title Osmoregulation in elephant fish Callorhinchus Milii (Holocephali), with special reference to the rectal gland
Author(s) Hyodo, Susumu
Bell, Justin D.
Healy, Jillian M.
Kaneko, Toyoji
Hasegawa, Sanae
Takei, Yoshio
Donald, JohnORCID iD for Donald, John orcid.org/0000-0001-5930-2642
Toop, Tes
Journal name Journal of experimental biology
Volume number 210
Start page 1303
End page 1310
Publisher The Company of Biologists Ltd
Place of publication Cambridge, England
Publication date 2007
ISSN 0022-0949
Keyword(s) holocephalan fish
elephant fish
rectal gland
Summary Osmoregulatory mechanisms in holocephalan fishes are poorly understood except that these fish are known to conduct urea-based osmoregulation as in elasmobranchs. We, therefore, examined changes in plasma parameters of elephant fish Callorhinchus milii, after gradual transfer to concentrated (120%) or diluted (80%) seawater (SW). In control fish, plasma Na and urea concentrations were about 300 mmol l–1 and 450 mmol l–1, respectively. These values were equivalent to those of sharks and rays, but the plasma urea concentration of elephant fish was considerably higher than that reported for chimaeras, another holocephalan. After transfer to 120% SW, plasma osmolality, urea and ion concentrations were increased, whereas transfer to 80% SW resulted in a fall in these parameters. The rises in ion concentrations were notable after transfer to 120% SW, whereas urea concentration decreased predominantly following transfer to 80% SW. In elephant fish, we could not find a discrete rectal gland. Instead, approximately 10 tubular structures were located in the wall of post-valvular intestine. Each tubular structure was composed of a putative salt-secreting component consisting of a single-layered columnar epithelium, which was stained with an anti-Na+,K+-ATPase serum. Furthermore, Na+,K+-ATPase activity in the tubular structures was significantly increased after acute transfer of fish to concentrated SW (115%). These results suggest that the tubular structures are a rectal gland equivalent, functioning as a salt-secreting organ. Since the rectal gland of elephant fish is well developed compared to that of Southern chimaera, the salt-secreting ability may be higher in elephant fish than chimaeras, which may account for the lower plasma NaCl concentration in elephant fish compared to other chimaeras. Since elephant fish have also attracted attention from a viewpoint of genome science, the availability of fish for physiological studies will make this species an excellent model in holocephalan fish group.
Notes External
Language eng
DOI 10.1242/jeb.003418
Field of Research 060603 Animal Physiology - Systems
HERDC Research category C1 Refereed article in a scholarly journal
Copyright notice ©2007, The Company of Biologists Ltd
Persistent URL http://hdl.handle.net/10536/DRO/DU:30007611

Document type: Journal Article
Collection: School of Life and Environmental Sciences
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