Reviews in Fish Biology and Fisheries 12: 133–142, 2002.
© 2003 Kluwer Academic Publishers. Printed in the Netherlands.
Morphophysiological studies on alligator gar (Atractosteus spatula)larval
development as a basis for their culture and repopulation of their natural
, M. Gonz
Grupo Ecoﬁsiolog´ıa, Fac. de Ciencias Biol´ogicas, Universidad Aut´onoma de Nuevo Le´on, Apartado F-96,
Monterrey, C. P. 66450, M´exico (E-mail: firstname.lastname@example.org);
Delegaci´on SAGARPA Tamaulipas, Encino
100, Tampico, Tamaulipas, C.P. 89230, M´exico
Accepted 6 March 2002
Abstract page 133
Materials and methods 134
Feeding trials (weaning)
Key words: alligator gar, enzymes, hormones, larval development, morphology, nutrition, physiology
Natural populations of alligator gar (Atractosteus spatula) have declined recently due to the effects of commercial
and sport ﬁsheries. Aquaculture represents a short-term alternative to restore natural populations, and a ﬁrst step to
accomplish culture of this species is the study of early life stages. Therefore, multidisciplinary research was used
to describe the major morpho-physiological changes taking place during this period. The studies serve as a basis
for the introduction of artiﬁcial diets for culture. A morphological study distinguished different nutritional stages,
as well as external indicators of starvation. A histological approach showed the digestive tract to be completely
formed 5 days after hatching (DAH), at the beginning of exogenous feeding. Throughout larval development,
intestinal maturation was followed and a nutritional indicator based on the mid-gut cell height was validated.
The occurrence of pepsin-like proteolytic activity was detected from ﬁve DAH, while trypsin, chimiotrypsin
and aminopeptidase-like activities gradually increased from two to nine DAH. The incidence of cannibalism in
culture conditions was controlled by exposure to anti-thyroid compounds (thiourea – TU) to retard snout growth.
This treatment did not effect growth and allowed juveniles to feed on live prey but prevented the consumption
of gar larvae of the same size. Larvae exposed to 3,3
,5-triiodo-1-thyronine (T3) had faster development, a
potentially advantageous characteristic for the repopulation of their natural habitat. Finally, artiﬁcial feeds were
well accepted and resulted in growth rates similar to those of gar larvae that were fed natural prey. This has
allowed the development of a feeding strategy that effectively reduced cannibalism and led to the production of 30
cm juveniles in four months.