Is there a digestive maturation model in agastric fish species?
E.Mayra Toledo-CuevasFrancisco J.Moyano LópezCarlos A.StrssmannManuel DíazCarlos A.Martínez Palacios
Universidad Michoacana de San Nicolás de Hidalgo.Instituto de Investigaciones Agropecuariasy Forestales.Av.San Juanito Itzícuaro S/N.Col.San Juanito ltzícuaro.58330,Morelia,Michoacán,MéxicoEscuela Politecnica Superior.Depto.de Biologia Aplicada.Universidad de Almeria,EspanaTokyo University of Marine Science and Technology,Faculty of Marine Science,Department of Marine Biosciences,JapanUniversidad Michoacana de San Nicolas de Hidalgo.Instituto de Investigaciones Agropecuariasy Forestales.Av.San Juanito Itzicuaro S/N.Col.San Juanito Itzicuaro.58330,Morelia,Michoacan,México
摘要：<正>Our research group has been working since several years ago in achieving the culture of a mexican silverside known as Pez Blanco of Patzcuaro（Menidia estor）.This is an endemic freshwater species belonging to the Atherinopsidae family.Although a lot of progress has been done,it hasn’t been possible yet to develop a balanced diet that allows good growth and survival. In similar situation are"pejerreyes",other freshwaters members of the family that are successfully cultured in Japan.Additionally,their weaning period is very long,about 5 months for M.estor and 2 months for pejerrey.It’s known that digestive physiology’s studies help to determine the most adequate weaning period that coincides with digestive maturation,and also to"design"the most appropriate feed according to their digestive capacities.However,preliminary studies in M.estor seem to show that because of being an agastric fish,they don’t follow the described digestive maturation model for marine gastric species.The aim of this work was to analysis more extensively the digestive development of two pejerrey species,Odontesthes bonariensis and O. hatcheri,also agastric species.They were reared at the Tokyo’s University of Marine Science and Technology Experimental facilities,since fertilized eggs up to 3 months post hatching,under standard culture and feeding conditions.Groups of 15 individuals were sampled each week,from the 1st post hatching week to the 9th,and then the 11th and 13th weeks.Because of their small size, hepatopancreas and intestine were extracted only from the 9th to 13th week’s fish.Whole individuals and organs were lyophilized during 48h.Enzyme extracts were prepared by homogenization in cold MilliQ water,followed by centrifugation（12000rpm,20 min,4℃）. Sample extracts were assayed for the determination of trypsin,chimotrypsin,lipase and acid and alkaline phosphatases by fiuorometric assays.Important variations in the digestive activity profiles were found during the development of each species and also among them.These findings can reflect the differences in feeding habits and their digestive abilities.Nevertheless,it seems that the described digestive maturation pattern couldn’t be found.For example,the acid phosphate activity was always lower than the alkaline one,but both increase during the ontogeny of the species.
The 14th International Symposium on Fish Nutrition & Feeding