title: Rearing temperature induces changes in muscle growth and gene expression in juvenile pacu (Piaractus mesopotamicus).
abstract: Pacu (Piaractus mesopotamicus) is a fast-growing fish that is extensively used in Brazilian aquaculture programs and shows a wide range of thermal tolerance. Because temperature is an environmental factor that influences the growth rate of fish and is directly related to muscle plasticity and growth, we hypothesized that different rearing temperatures in juvenile pacu, which exhibits intense muscle growth by hyperplasia, can potentially alter the muscle growth patterns of this species. The aim of this study was to analyze the muscle growth characteristics together with the expression of the myogenic regulatory factors MyoD and myogenin and the growth factor myostatin in juvenile pacu that were submitted to different rearing temperatures. Juvenile fish (1.5 g weight) were distributed in tanks containing water and maintained at 24°C (G24), 28 °C (G28) and 32 °C (G32) (three replicates for each group) for 60 days. At days 30 and 60, the fish were anesthetized and euthanized, and muscle samples (n=12) were collected for morphological, morphometric and gene expression analyses. At day 30, the body weight and standard length were lower for G24 than for G28 and G32. Muscle fiber frequency in the <25 μm class was significantly higher in G24, and the >50 μm class was lower in G24. MyoD gene expression was higher in G24 compared with that in G28 and G32, and myogenin and myostatin mRNA levels were higher in G24 than G28. At day 60, the body weight and the standard length were higher in G32 but lower in G24. The frequency distribution of the <25 μm diameter muscle fibers was higher in G24, and that of the >50 μm class was lower in G24. MyoD mRNA levels were higher in G24 and G32, and myogenin mRNA levels were similar between G24 and G28 and between G24 and G32 but were higher in G28 compared to G32. The myostatin mRNA levels were similar between the studied temperatures. In light of our results, we conclude that low rearing temperature altered the expression of muscle growth-related genes and induced a delay in muscle growth in juvenile pacu (P. mesopotamicus). Our study provides a clear example of thermally induced phenotypic plasticity in pacu fish and shows that changing the rearing temperature during the juvenile stage can have a considerable effect on gene expression and muscle growth in this species.
authors.affiliation: São Paulo State University, UNESP, Institute of Biosciences, Department of Morphology, 18618-970 Botucatu, SP, Brazil. Electronic address: ttgutierrez@gmail.com.
authors.forename: Tassiana
authors.initials: T
authors.lastname: Gutierrez de Paula
authors.affiliation: State University of Maringa, Biological Sciences Center, Department of Morphological Sciences, 18618-970 Botucatu, SP, Brazil. Electronic address: fernandalosi@gmail.com.
authors.forename: Fernanda Losi Alves
authors.initials: FL
authors.lastname: de Almeida
authors.affiliation: São Paulo State University, UNESP, Institute of Biosciences, Department of Morphology, 18618-970 Botucatu, SP, Brazil. Electronic address: fcarani@gmail.com.
authors.forename: Fernanda Regina
authors.initials: FR
authors.lastname: Carani
authors.affiliation: São Paulo State University, UNESP, Institute of Biosciences, Department of Morphology, 18618-970 Botucatu, SP, Brazil. Electronic address: ijvechetti@ibb.unesp.br.
authors.forename: Ivan José
authors.initials: IJ
authors.lastname: Vechetti-Júnior
authors.affiliation: São Paulo State University, Institute of Biosciences, Department of Biostatistics, 18618-970 Botucatu, SP, Brazil. Electronic address: bioestatistica@ibb.unesp.br.
authors.forename: Carlos Roberto
authors.initials: CR
authors.lastname: Padovani
authors.affiliation: São Paulo State University, Aquaculture Center (CAUNESP), 14884-900 Jaboticabal, SP, Brazil. Electronic address: rondi_salomao@hotmail.com.
authors.forename: Rondinelle Arthur Simões
authors.initials: RA
authors.lastname: Salomão
authors.affiliation: São Paulo State University, UNESP, Institute of Biosciences, Department of Morphology, 18618-970 Botucatu, SP, Brazil. Electronic address: edsonmareco@gmail.com.
authors.forename: Edson Assunção
authors.initials: EA
authors.lastname: Mareco
authors.affiliation: Sao Paulo Agency for Agribusiness Technology-APTA-Pole High Sorocabana, 19015-970, Post office box: 298, Presidente Prudente, SP, Brazil. Electronic address: vander@apta.sp.gov.br.
authors.forename: Vander Bruno
authors.initials: VB
authors.lastname: Dos Santos
authors.affiliation: São Paulo State University, UNESP, Institute of Biosciences, Department of Morphology and CAUNESP, 18618-970 Botucatu, Sao Paulo, Brazil. Electronic address: maeli@ibb.unesp.br.
authors.forename: Maeli
authors.initials: M
authors.lastname: Dal-Pai-Silva
mesh_terms: D000818:Animals; D060125:Characiformes / Q000235:genetics* / Q000254:growth & development; D015870:Gene Expression; D006358:Hot Temperature; D024510:Muscle Development; D009132:Muscles / Q000378:metabolism*; D017570:MyoD Protein / Q000235:genetics / Q000378:metabolism; D018008:Myogenin / Q000235:genetics / Q000378:metabolism; D055435:Myostatin / Q000235:genetics / Q000378:metabolism
chemical_list: D017570:MyoD Protein; D018008:Myogenin; D055435:Myostatin
keywords: Extrinsic factor; Fish; Myogenic regulatory factors; Myostatin; Skeletal muscle