Biochemical characterization and physiological role of cortical rods in black tiger shrimp, Penaeus monodon Hathairat Kruevaisayawan a,c , Rapeepun Vanichviriyakit a , Wattana Weerachatyanukul a, ⁎ , Sirilug Magerd a , Boonsirm Withyachumnarnkul a,b , Prasert Sobhon a a Department of Anatomy, Faculty of Science, Mahidol University, Rama VI Road, Bangkok 10400, Thailand b The Center of Excellence in Shrimp Biotechnology, Faculty of Science, Mahidol University, Bangkok 10400, Thailand c Department of Anatomy, Faculty of Medical Science, Naresuan University, Phitsanulok 65000, Thailand Received 28 December 2006; received in revised form 15 March 2007; accepted 3 April 2007 Abstract Cortical rods (CRs), precursors of egg jelly investment in many penaeoid shrimp, are composed of different proportions of proteins and carbohydrates, the physiological role of which still requires extensive investigation. In this study, we demonstrated the biochemical properties of the CRs and their role in the induction of the acrosome reaction (AR). Profiles of the isolated CRs revealed a number of major protein bands ranging from 35 to 230 kDa. These CR proteins were extensively glycosylated and sulfated. Lectin-based carbohydrate analysis further revealed the highest reactivity of concanavalin A (Con A) among other lectins used. In addition, the selective interference of Con A binding with mannose but not glucose indicated that CR glycoproteins were of high-mannose type. Using immunoblotting with anti-CR antibody, we further demonstrated that part of egg water (EW, a natural AR inducer) was derived from miscible components of the CRs. Physiological tests of water-soluble CR (wsCR) revealed its high AR inducing competency comparable to that of EW, which was far superior to that of acid-urea treated CR (auCR). Furthermore, the wsCR-induced AR was selectively inhibited by Con A, suggesting the significance of the exposing mannose residues in regulating P. monodon sperm AR response. © 2007 Elsevier B.V. All rights reserved. Keywords: Cortical rod; Egg jelly; Carbohydrate; Acrosome reaction 1. Introduction By the end of vitellogenesis in penaeiod shrimp, the developing eggs reach the final stage of oocyte maturation which is characterized by the appearance of rod-like bodies, called cortical rods (CRs), arranged radially around the periphery of the oocyte plasma membranes (Anderson et al., 1984; Lynn and Clark, 1987; Pongtippatee-Taweepreda et al., 2004; Rankin and Davis, 1990; Yano, 1988). These CRs are located in the extracellular crypts formed by the invagination of the oolemma into the egg cortex. During spawning, CRs are released upon contact of the eggs with seawater and form a jelly investment around the eggs in many penaeiod shrimp species (Clark et al., 1990; Pongtippa- tee-Taweepreda et al., 2004; Rankin and Davis, 1990; Yano, 1995). Thereafter, the jelly substances gradually fall off from the spawned egg surface and become the Aquaculture 270 (2007) 289 – 298 www.elsevier.com/locate/aqua-online ⁎ Corresponding author. Tel.: +66 02 201 5422; fax: +66 02 354 7168. E-mail address: scwwy@mahidol.ac.th (W. Weerachatyanukul). 0044-8486/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.aquaculture.2007.04.004