Digestive system development and study of acid and alkaline protease digestive capacities using biochemical and molecular approaches in totoaba (Totoaba macdonaldi) larvae

Abstract

The present study aimed to describe and understand the development of the digestive system in totoaba (Totoaba macdonaldi) larvae from hatching to 40 days post-hatch (dph) from morphological and functional perspectives. At hatch, the digestive system of totoaba was undifferentiated. The anus and the mouth opened at 4 and 5 dph, respectively. During exogenous feeding, development of the esophagus, pancreas, liver and intestine was observed with a complete differentiation of all digestive organs. Expression and activity of trypsin and chymotrypsin were observed as early as at 1 dph, and increments in their expression and activity coincided with changes in food items (live and compound diets) and morpho-physiological development of the accessory digestive glands. In contrast, pepsin was detected later during development, which includes the appearance of the gastric glands between 24 and 28 dph. One peak in gene expression was detected at 16 dph, few days before the initial development of the stomach at 20 dph. A second peak of pepsin expression was detected at day 35, followed by a peak of activity at day 40, coinciding with the change from live to artificial food. Totoaba larvae showed a fully morphologically developed digestive system between 24 and 28 dph, as demonstrated by histological observations. However, gene expression and activity of alkaline and acid proteases were detected earlier, indicating the functionality of the exocrine pancreas and stomach before the complete morphological development of the digestive organs. These results showed that integrative studies are needed to fully understand the development of the digestive system from a morphological and functional point of views, since the histological organization of digestive structures does not reflect their real functionality. These results indicate that the digestive system of totoaba develops rapidly during the first days post-hatch, especially for alkaline proteases, and the stomach becomes functional between 20 and 24 dph allowing the weaning process to begin at this age.

Initial ontogeny of digestive enzymes in the early life stages of captive-bred European eels during fasting: A partial characterization

“…The data in the present study showed the presence of the transcript genes in eel larvae from hatching to P20 in accordance with other studies reporting on the European eel (Politis et al, 2018), Anguilla japonica (Kurokawa et al, 2002;Murashita et al, 2013;Pedersen, 2003) and other marine species, such as totoaba, gilthead seabream, Pacific bluefin tuna, Asian seabass, Atlantic cod, European seabass and Senegal sole (Galaviz et al, 2015;Mata-Sotres et al, 2016;Murashita et al, 2014;Srichanun et al, 2013;Zambonino-Infante et al, 2008).…”

Expression analyses of digestive enzymes during early development and in adults of the chame fishDormitator latifrons

“…Oligonucleotides for digestive enzymes and reference genes were selected from those reported in other species. Trypsin ( tryp ) and ribosomal 18S‐rRNA ( 18S ) were reported for spotted rose snapper (Moguel‐Hernández et al, ); leucine aminopeptidase ( lap ) and alpha‐tubulin ( tub‐α ) were reported for Asian seabass (Srichanun, Tantikitti, Utarabhand, & Kortner, ); pepsin ( pep ) was reported for totoaba (Galaviz et al, ). The oligonucleotides of digestive enzymes and reference genes used for qPCR analyses are shown in Table .…”

Assessment of dietary taurine essentiality on the physiological state of juvenileTotoaba macdonaldi

“…Totoaba was placed on the endangered list of the Convention on International Trade in Endangered Species (CITES) and, in 1979, was included in the US Endangered Species list (Barrera‐Guevara, ). Protocols on reproduction, larval development and juvenile nutrition were developed as dedicated research was conducted, highlighting the high potential of commercial totoaba aquaculture (Galaviz et al., ; López, Flores‐Ibarra, Bañuelos‐Vargas, Galaviz & True, ; Trejo‐Escamilla, Galaviz, Flores‐Ibarra, Álvarez González & López, ; True, Loera & Castro, ). In a previous study of totoaba, green liver was detected when fish were fed a commercial diet with soybean meal (SBM) and soy protein concentrate (SPC) without taurine supplementation (López et al., ).…”