Temperature effects on gene expression and morphological development of European eel, Anguilla anguilla larvae

Abstract

Temperature is important for optimization of rearing conditions in aquaculture, especially during the critical early life history stages of fish. Here, we experimentally investigated the impact of temperature (16, 18, 20, 22 and 24°C) on thermally induced phenotypic variability, from larval hatch to first-feeding, and the linked expression of targeted genes [heat shock proteins (hsp), growth hormone (gh) and insulin-like growth factors (igf)] associated to larval performance of European eel, Anguilla anguilla. Temperature effects on larval morphology and gene expression were investigated throughout early larval development (in real time from 0 to 18 days post hatch) and at specific developmental stages (hatch, jaw/teeth formation, and first-feeding). Results showed that hatch success, yolk utilization efficiency, survival, deformities, yolk utilization, and growth rates were all significantly affected by temperature. In real time, increasing temperature from 16 to 22°C accelerated larval development, while larval gene expression patterns (hsp70, hsp90, gh and igf-1) were delayed at cold temperatures (16°C) or accelerated at warm temperatures (20–22°C). All targeted genes (hsp70, hsp90, gh, igf-1, igf-2a, igf-2b) were differentially expressed during larval development. Moreover, expression of gh was highest at 16°C during the jaw/teeth formation, and the first-feeding developmental stages, while expression of hsp90 was highest at 22°C, suggesting thermal stress. Furthermore, 24°C was shown to be deleterious (resulting in 100% mortality), while 16°C and 22°C (~50 and 90% deformities respectively) represent the lower and upper thermal tolerance limits. In conclusion, the high survival, lowest incidence of deformities at hatch, high yolk utilization efficiency, high gh and low hsp expression, suggest 18°C as the optimal temperature for offspring of European eel. Furthermore, our results suggest that the still enigmatic early life history stages of European eel may inhabit the deeper layer of the Sargasso Sea and indicate vulnerability of this critically endangered species to increasing ocean temperature.

River‐Specific Gene Expression Patterns Associated with Habitat Selection for Key Hormone‐Coding Genes in Glass Eel‐Stage American Eels

“…Recently, Politis et al. () studied the larval stage of European Eels and showed that GH expression was higher at a higher temperature. Here, temperature may not play such a role, as temperatures in northern areas (Grande‐Rivière‐Blanche and Rivière‐Saint‐Jean) are expected to be colder than in the Nova Scotia littoral zone.…”

“…, ) and in embryonic and larval European Eels (Politis et al. ), and we studied glass eels colonizing rivers previously associated with different American Eel ecotypes (Mersey River on the Atlantic coast [BW/SW ecotype]; Rivière‐Saint‐Jean, Gulf of St. Lawrence [FW ecotype]; and Grande‐Rivière‐Blanche, St. Lawrence estuary [FW ecotype]; Pavey et al. ) and according to their salinity preference (Boivin et al.…”

Effect of parental origin on early life history traits of European eel

“…Gametes from each replicate were then activated using 11.7 ml of activation media, which consisted of reverse osmosis water salted to 36 psu using Red Sea salt (Red Sea International, Eilat, Israel) at 20°C. After 5 min of gamete contact time, the eggs/embryos were transferred into 200‐ml beakers for incubation at 36 psu and 18°C (Politis et al, ). After 4 hr of incubation, embryos from each treatment were transferred into new beakers with filtered UV seawater at 36 psu, supplemented with 50 ppm ampicillin and rifampicin (Sigma‐Aldrich Chemie, Steinheim, Germany; Sørensen et al, ) and kept in a thermal incubator at 18°C (Politis et al, , ).…”

“…At present, improved assisted reproductive technologies and in vitro fertilization techniques are implemented to produce viable eggs and hatched larvae (Butts, Sørensen, Politis, Pitcher, & Tomkiewicz, ; Mordenti et al, ; Müller, McEvoy, Tomkiewicz, Politis, & Amigo, ). In addition, controlled laboratory studies have identified optimal environmental conditions for improved early offspring performance, that is light (Politis, Butts, & Tomkiewicz, ), salinity (Sørensen, Butts, Munk, & Tomkiewicz, ) and temperature (Politis et al, , ). Together, this new innovative technology has enabled the production of copious amounts of offspring reaching the first‐feeding stage (Butts, Sørensen, Politis, & Tomkiewicz, ; Sørensen, Tomkiewicz, et al, ).…”

Changes in gene and genotype frequencies during the development of the grass carp Ctenopharyngodon idella

“…Fishes are an important, stable and safe protein resource for humans, especially in China where aquaculture is considered an effective method for providing animal proteins (Gui & Zhu, ). During ontogenesis from the oosperm to adulthood, fishes are affected by many threats in the complex water environment, especially in the early stage of development (Bourrachot et al ., ; Du Gas et al ., ; Politis et al ., ). The early stage of development is critical for fishes because the digestive, immune and skeletal systems are incomplete in this stage (Ferraresso et al ., ; Huttenhuis et al ., ; Sahlmann et al ., ).…”