New Zealand Journal of Marine and Freshwater Research abstracts
Short communication
Stage-dependent thyroxine effects on sea urchin development
LELAND G. JOHNSON*
University of Auckland
Leigh Marine Laboratory
P. O. Box 349
Warkworth, New Zealand
*Present address: Department of Biology, Augustana College, Sioux
Falls, SD 57197, United States. email: johnson@inst.augie.edu
Abstract Thyroxine, one of the iodinated hormones produced by
vertebrate thyroids, has been reported to accelerate late larval development in
several sea urchins (Chino et al. 1994) and in the crown-of-thorns starfish
(Johnson & Cartwright 1996), but thyroxine effects on earlier portions of
echinoderm development have not been reported. I investigated thyroxine effects
on developmental rates during several periods spanning development from early
cleavage to metamorphosis in the New Zealand sea urchin Evechinus
chloroticus (Valenciennes). Thyroxine treatment slowed development
between the eight-cell stage and assembly of the four-armed pluteus and
mid-larval development between the four-armed and six-armed stages. Thyroxine
treatment accelerated progress of eight-armed plutei toward settling, but did
not alter the final percentages of larvae that settled and metamorphosed to
juvenile urchins. Acceleration of late larval echinoderm development by
thyroxine may indicate a relatively ancient evolutionary origin of thyroxine's
effects on developmental processes (Johnson 1997).
Keywords sea urchin; larval development; New Zealand;
thyroxine; developmental acceleration; metamorphosis; Evechinus
chloroticus
M98006
Received 17 February 1998; accepted 29 July 1998
PDF file of entire paper: medium quality (469K); (scanned from paper original: notes about this process)
This year's abstracts |
Journal home page |
All abstracts |
Publishing home page
