Cloning and expression of hyperglycemic (CHH) and molt-inhibiting (MIH) hormones mRNAs from the eyestalk of shrimps of Litopenaeus vannamei grown in different temperature and salinity conditions Asunción Lago-Lestón a,1 , Elizabeth Ponce a, ⁎ , Ma. Enriqueta Muñoz b a Centro de Investigación Científica y de Educación Superior de Ensenada, Departamento de Biotecnología Marina, Km. 107 carretera Tijuana-Ensenada, Ensenada, B.C. CP 22860, Mexico b Facultad de Ciencias Químicas e Ingeniería, Universidad Autónoma de Baja California, Av. Tecnológico s/n Mesa de Otay, Tijuana, B.C. CP 22390, Mexico Received 31 December 2006; received in revised form 6 April 2007; accepted 10 April 2007 Abstract This study describes the effect of temperature and salinity on the expression of chh and mih genes obtained from Litopenaeus vannamei juveniles. Results suggest that temperature had a higher effect on gene expression than salinity. Two different mih transcripts were obtained from the eyestalks of shrimps exposed to 20 °C. Direct sequence evidence suggests that these two isoforms come from a mih gene transcribed in an alternative splicing manner. The genome-cDNA alignment suggests that the mih-1 contains 4 exons and gives rise to a mature MIH-like peptide of 73 amino acids (Liv-MIH-1), while mih-2 contains exons I, II and IV and gives rise to a mature MIH-like peptide of 74 residues (Liv-MIH-2). The chh transcript is suggested to consist of 3 exons and gives rise to a mature peptide of 74 amino acids (Liv-CHH). The exon–intron boundary of the mih and chh genes follows Chambon's rule (GT-AG) for the splice donor and acceptor sites. Gene structure and phylogenetic analysis imply that these three peptides are more related to the CHH group than to the MIH/GIH group. Liv-MIH and Liv-MIH-2 may have a multi-functional role as observed in other CHH family members. © 2007 Elsevier B.V. All rights reserved. Keywords: Gene expression; Alternative splicing; Gene structure; Neurohormones; Litopenaeus vannamei 1. Introduction Crustaceans have developed a complex neuroendo- crine system that involves regulatory elements able to act at short, medium or long term allowing them to respond to external factors by adjusting their vital functions to current needs (Kleinholz and Keller, 1979; Keller, 1992; de Kleijn and van Herp, 1995). Among the external conditions that regulate these factors are temperature, salinity, photoperiodicity, nutrition and stress (Ferraris et al., 1994). Studies frequently focus on the effect of a single variant and, in addition, most studies have used postlarvae with little attention having paid to responses of juvenile and adult shrimp (Ponce et al., 1997). Since Aquaculture 270 (2007) 343 – 357 www.elsevier.com/locate/aqua-online ⁎ Corresponding author. Tel.: +52 646 1750500x24441; fax: +52 646 1750569. E-mail address: eponce@cicese.mx (E. Ponce). 1 Current address: CCMAR, CIMAR-Laboratório Associado, Uni- versidade do Algarve, Campus de Gambelas, 8005-139 Faro, Portugal. 0044-8486/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.aquaculture.2007.04.014