Search

Trypsin is an important serine protease that is considered to be involved in digestion of protein in teleost fish. Nevertheless, studies on trypsin/trypsinogen in fish embryos are very limited. In this study, the trypsinogen of turbot ( Scophthalmus maximus ) ( tTG ) was identified and the expression patterns and activity of trypsinogen/trypsin were investigated. The results showed that the tTG mRNA was evenly distributed in the oocytes and was also expressed along the yolk periphery in early embryos. At later embryo stages and 1 days after hatching (dph), the tTG mRNA concentrated at the alimentary tract and head. Quantitative expression analysis showed that the tTG transcripts decreased after fertilization until the gastrula stage, then increased with the embryo and larvae development. This result was also confirmed by the specific activity analysis of trypsin and in-situ-hybridization (ISH). All of the results indicated that tTG in early embryo stages was maternally derived and expressed by itself after gastrula stages. Additionally, location of tTG mRNA in embryos and larvae was investigated; we considered that trypsin may have multiple functions during the embryo development process. Based on our results regarding trypsinogen in embryos and early development, we concluded that the trypsin/trypsinogen in turbot embryos was inherited from a maternal source and we suggested that trypsin in early development has multiple functions in the process of development. [ABSTRACT FROM AUTHOR]

Abstract: To investigate the effect of dissolved oxygen level ([O2]) on maintenance metabolism, feeding metabolism, aerobic swimming performance and their metabolic interaction in juvenile southern catfish (Silurus meridionalis Chen), we measured the following: (1) the resting oxygen consumption rate (MO2rest) over a range of water [O2] and from this we calculated the critical oxygen tension (P crit) of fasting fish; (2) the postprandial MO2 response (10% body mass meal size) at water [O2] of 1, 2, 4 and 8mgO2 L−1; and (3) the swimming performance of fasting and digesting fish at water [O2] of 1, 2, 4 and 8mgO2 L−1 at 25°C. The MO2rest remained constant over a broad range of water [O2] but then dropped markedly upon reaching the P crit (16.4% saturation). Hypoxic groups presented lower peak postprandial MO2 (MO2peak) (1mgO2 L−1 group), larger energy expenditure and longer digestive process (both 1 and 2mgO2 L−1) than those of normoxic groups. Both critical swimming speed (U crit) and the active metabolic rate (MO2active) of fasting fish remained unchanged over a decrease in water [O2] from 8 to 4mgO2 L−1 and then decreased significantly with further decreases in water [O2]. These parameters in fed fish showed a pronounced decrease as water [O2] decreased from 8 to 1mgO2 L−1. Feeding caused a significantly lower U crit in the 2mgO2 L−1 water [O2] group, a significantly higher MO2active in both the 2 and 8mgL−1 water [O2] groups and a significantly higher metabolic scope (MO2active − MO2rest) in both the 2 and 4mgO2 L−1 water [O2] groups compared to fasting fish. The MO2 increased greatly with swimming speed in the higher water [O2] groups, whereas it leveled off as swimming speeds approached the U crit in the lower water [O2] groups. Within all water [O2] groups, feeding caused a higher MO2 compared to fasting fish when fish swam at the same speeds, except in the 1mgO2 L−1 group. This finding showed that the critical water [O2] for maintenance of metabolism, digestion, swimming and postprandial swimming increased sequentially due to the increasing O2 demand, which challenges respiratory capacity. With the administration of the medium-sized meal that was used in this study, the metabolic mode of juvenile southern catfish changed from an additive mode during normoxia to a digestion-priority mode under moderate hypoxia and to locomotion-priority mode under hypoxia. [Copyright &y& Elsevier]

Abstract: The major neutral lipase excreted by the pancreas in fish, is bile activated lipase (BAL). Here we present evidence that cod have a functional BAL and a non-functional pancreatic lipase related protein (PLRP). The Atlantic cod genome does not seem to contain colipase which is essential for pancreatic lipase activity. During the larval stages, the gene expression of BAL was low until the point when pyloric caeca started to differentiate and develop (~20mm standard length (SL)). Then the expression increased until ~50mm SL. The PLRP gene was expressed but showed very little regulation. The activity of neutral lipase did not increase in parallel to gene expression. The mismatch between activity and gene expression measurements may be partly explained by the unspecific analytical method, when analysing lipase activity in larva whole body. There is neutral lipase activity in numerous tissues in the fish larvae and the lipase activity in the gut, relatively to activity in the whole body, decreased with age. Furthermore, neutral lipase activity in rotifers was ten times higher than in whole cod larvae with full guts. Activity originating from the live prey may therefore explain the high whole body lipase activity from 3 to 20dph. The results also indicate that “adult type” digestion of neutral lipid develops late in the larval period (from 20mm SL), while other mechanisms of lipid uptake are active at the early larval stage. [ABSTRACT FROM AUTHOR]