Development
of endocrine system regulating exocrine pancreas and estimation of feeding
and digestive ability in Japanese eel larvae
T. Kurokawa, N. Iinuma, T. Unuma, H. Tanaka, H.
Kagawa, H. Ohta, T. Suzuki-2004
Aquaculture, 234(1-4): 513-525
Abstract:
To investigate the feeding and digestive physiology
of early eel larvae, the development of cholecystokinin (CCK) and peptide YY
(PYY) in the larval intestine, the feeding speed and pancreatic trypsin
secretion in response to feeding were observed. CCK and PYY mRNA started to
be expressed in the larval intestine at 8 days post-hatching (dph). This
indicates that the pancreatic enzyme secretion is probably controlled by the
CCK and PYY endocrine systems from the first feeding. Using fluorescein
isothyiocyanate isomer (FITC)-labeled freeze-dried shark egg powder
(Aquaran) as a diet, 10-dph eel larvae were estimated to feed at a rate of
0.04 µg Aquaran/min. The tryptic activity in the intestines of 11-dph
larvae increased approximately 4.2-fold at 1 h of feeding, whereas that in
the pancreas remained constant. These results indicate that the digestive
tract of these larvae recognized Aquaran as a nutrient, and that the
exocrine pancreas secreted digestive enzymes into the intestine and began to
synthesize digestive enzymes in response to feeding.