Developmental changes in stomach, intestine, and skin glycoconjugates in summer flounder (Paralichthys dentatus): A lectin histochemical study Bruno Soffientino a,⁎ , Marta Gomez-Chiarri b , Jennifer Specker a a Graduate School of Oceanography, University of Rhode Island, Box 200, URI Bay Campus, 218 South Ferry Rd., Narragansett, RI 02882-1197, United States b Department of Fisheries, Animal and Veterinary Science, University of Rhode Island, 23 Woodward Hall, Kingston, RI 02881, United States Received 25 June 2005; received in revised form 19 July 2005; accepted 23 July 2005 Abstract This study asked whether the glycoconjugates of stomach, intestine, and skin epithelia and their mucous secretions change during metamorphosis in summer flounder. Larvae and juveniles were assayed histochemically with biotinylated lectins, and scored for differences in staining intensity and specificity between the two developmental stages. In the stomach epithelium, the number of positive lectins changed little from larvae to juveniles; however, the secreted mucus increased in staining with DBA, ECL, GSA II, PNA, and SBA lectins. In the intestine, a developmental decrease in the binding intensity of the intestinal brush border was noted for DSL, RCA 120 , VVA, SNA, and UEA I lectins, while intestinal goblet cells underwent a large increase in binding for GSA II. The skin mucous cells of the larvae were negative for DBA, DSL, ECL, PNA, RCA 120 , and SNA, but became positive in the juveniles. In conclusion, this study showed that changes in glycoconjugate expression occur during metamorphosis in the stomach, intestine, and skin of summer flounder. The changes in the gut glycoconjugates correlate developmentally with shifts in bacterial flora composition found by other studies, and therefore might be relevant to the study of bacteria–host relationships in summer flounder. © 2005 Elsevier B.V. All rights reserved. Keywords: Lectin; Glycoconjugate; Summer flounder; Host–pathogen relationship; Gut flora; Vibrio 1. Introduction The summer flounder is a marine flatfish from the North American East Coast recently introduced to the aquaculture industry. Efforts to implement biologically and economically viable culture methods are hampered by disease susceptibility following transport stress (Soffientino et al., 1999). An understanding of the physiology and environ- mental requirements of larval and juvenile stages is critical to the development of culture methods for most fish. Heavy mortality typically occurs during these stages, but the causes often remain unknown, due in part to the difficulty of carrying out detailed pathological studies in very small specimens (Alves et al., 1999). Developmental and physiological studies of the gut and skin barrier function (hydrophobicity, mucus production and composition, secretion of antimicrobial peptides) should be emphasized because these epithelia are the barriers that pathogens breach, and at the same time they Aquaculture 253 (2006) 680 – 687 www.elsevier.com/locate/aqua-online ⁎ Corresponding author. Tel.: +1 401 874 6599; fax: +1 401 874 6887. E-mail address: bruno@gso.uri.edu (B. Soffientino). 0044-8486/$ - see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.aquaculture.2005.07.044