EFFECT OF STARVATION ON REFEEDING, DIGESTIVE ENZYME
ACTIVITY, OXYGEN CONSUMPTION, AND AMMONIA EXCRETION IN JUVENILE WHITE SHRIMP
LITOPENAEUS VANNAMEI
L.I. Comoglio, G. Gaxiola, A. Roque, G. Cuzon, O.
Amin-2004
Journal of Shellfish Research, 23(1): 243-249
Abstract:
Juveniles of the white shrimp Litopenaeus
vannamei were
kept without food for between 0 to 15 days to evaluate the impact of
starvation on physiologic state (oxygen consumption, poststarvation
refeeding index, nitrogen excretion, and O:N ratio) and digestive enzymes
activity. Physiologic changes were found after 6 days of fasting, and
refeeding ability declined as a result. Nevertheless. the shrimp were able
to survive 16 days without food. Starvation caused metabolism to drop
progressively toward a basal level (21 J . h-1 . g-1)
and a decrease in the rate of ammonia excretion, because of the catabolism
of amino acids from soluble protein in the hepatopancreas. This decrease led
to an increase in digestive enzymes specific activity (U/mg protein). But,
expressed as total U. all digestive enzyme activities decreased in the
absence of substrate from 0.016 to 0.007 U/hepatopancreas (HP) for
(1-amylase and 2.58 to 0.63 U/HP for total trypsin. L. vannamei juveniles showed a true physiologic adaptation
mechanism to food deprivation: no changes in body weight but loss in
hepatosomatic index, no exuviations, including the utilization of HP soluble
proteins (a drop from 269 to 53 mg/mL). After 10 days, a neoglycogenic
pathway and the corresponding tissue enzymes activities seemed enhanced, and
the animals derived all energetic substrates mainly from protein (O:N ratio
of 17) to cover their metabolic costs. Estimates of basal metabolism (Hem)
from the routine respiration rate per day (from 361 to 725 J . g ww-1
. day-1 through the 15-day starvation period), and loss of
nonfecal energy (HxE) from the nitrogen excretion rate (varying from 39 to
57 J . g ww-1 . day-1 during the same period) were
used in a bioenergetic partition model of a fasting juvenile, which
indicated that the energetic requirement to survive without feeding was in
the range of 418 and 771 J . g ww-1. day-1 during the
15-day period of starvation.
(Centro Austral de Investigaciones Cientificas (CADIC-CONICET), Ushuaia,
Tierra del Fuego, Argentina, e-mail: lcomoglio@hotmail.com)