title: Development of digestive tract and enzyme activities during the early ontogeny of the tropical gar Atractosteus tropicus.
abstract: Changes in digestive enzyme activity and histology were studied in Atractosteus tropicus embryos, larvae and juvenile periods. Alkaline protease, chymotrypsin, carboxypeptidase A, lipase and α-amylase were detected in all periods and gradually increased until reaching the maximum peak in juveniles; meanwhile, acid protease was first detected at 5 days after hatching (dah) when first feeding started and trypsin and leucine aminopeptidase activities were detected from 19 dah, their values being increased gradually until reaching a maximum value at 31 dah. Acid and alkaline phosphatase activities increased from yolk-sac absorption (3 dah) until day 31 after hatching. Zymogram for acid protease showed two bands in active forms (0.4 and 0.5 Rfs) from day 5 after hatching and a third protease form (0.3 Rf) that appears at 31 dah. Two active forms (26.3 and 24.9 kDa) were detected using SDS-PAGE alkaline proteases zymogram at 5 dah, and an additional active form (44.1 kDa) was detected at 7 dah. Regarding the histological development of the digestive system, the exocrine pancreas containing zymogen granules was already visible at 3 dah, whereas at 5 dah first gastric glands were already detected in the stomach. Between 7 and 9 dah, the digestive tract of A. tropicus resembled that of a juvenile specimen with a well-developed and short oesophagus, stomach divided into a glandular and non-glandular (pyloric) stomach, folded intestine with pyloric caeca and a well-developed spiral valve (posterior intestine). Considering this, larvae of A. tropicus are capable of digesting several foods from yolk absorption (3 dah), maximizing its activities at 15 dah, age at which the organisms maximize its capability to absorb nutrients from diets provided.
authors.affiliation: Laboratorio de Acuicultura Tropical, DACBIOL-UJAT, Carretera Villahermosa-Cárdenas KM 0.5, 86139, Villahermosa, Tabasco, Mexico.
authors.forename: C A
authors.initials: CA
authors.lastname: Frías-Quintana
authors.affiliation: Laboratorio de Acuicultura Tropical, DACBIOL-UJAT, Carretera Villahermosa-Cárdenas KM 0.5, 86139, Villahermosa, Tabasco, Mexico.
authors.forename: G
authors.initials: G
authors.lastname: Márquez-Couturier
authors.affiliation: Laboratorio de Acuicultura Tropical, DACBIOL-UJAT, Carretera Villahermosa-Cárdenas KM 0.5, 86139, Villahermosa, Tabasco, Mexico. alvarez_alfonso@hotmail.com.
authors.forename: C A
authors.initials: CA
authors.lastname: Alvarez-González
authors.affiliation: Centro de Investigaciones Biológicas del Noroeste S.C., Av. Instituto Politécnico Nacional 195, Colonia Playa Palo de Santa Rita Sur, 23096, La Paz, Baja California Sur, Mexico.
authors.forename: D
authors.initials: D
authors.lastname: Tovar-Ramírez
authors.affiliation: Centro de Investigaciones Biológicas del Noroeste S.C., Av. Instituto Politécnico Nacional 195, Colonia Playa Palo de Santa Rita Sur, 23096, La Paz, Baja California Sur, Mexico.
authors.forename: H
authors.initials: H
authors.lastname: Nolasco-Soria
authors.affiliation: Facultad de Ciencias Marinas, Universidad Autónoma de Baja California (UABC), PO Box 76, 22860, Ensenada, B.C., Mexico.
authors.forename: M A
authors.initials: MA
authors.lastname: Galaviz-Espinosa
authors.affiliation: Laboratorio de Acuicultura Tropical, DACBIOL-UJAT, Carretera Villahermosa-Cárdenas KM 0.5, 86139, Villahermosa, Tabasco, Mexico.
authors.forename: R
authors.initials: R
authors.lastname: Martínez-García
authors.affiliation: Laboratorio de Acuicultura Tropical, DACBIOL-UJAT, Carretera Villahermosa-Cárdenas KM 0.5, 86139, Villahermosa, Tabasco, Mexico.
authors.forename: S
authors.initials: S
authors.lastname: Camarillo-Coop
authors.affiliation: División de Ciencias de la Vida, Campus Irapuato-Salamanca, Universidad de Guanajuato, Ex Hacienda El Copal, Irapuato, Guanajuato, Mexico.
authors.forename: R
authors.initials: R
authors.lastname: Martínez-Yañez
authors.affiliation: IRTA - Sant Carles de la Ràpita, Crta. Poble Nou km 5.5, 43540, Sant Carles de la Rapita, Tarragona, Spain.
authors.forename: E
authors.initials: E
authors.lastname: Gisbert
mesh_terms: D000818:Animals; D005399:Fishes / Q000196:embryology*; D041981:Gastrointestinal Tract / Q000196:embryology* / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental / Q000502:physiology; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology; D007814:Larva / Q000378:metabolism
keywords: Atractosteus tropicus; Lipase; Ontogeny; Phosphatase; Proteases; α-Amylase