Analysis of 686 expressed sequence tags (ESTs) from the intertidal harpacticoid copepod Tigriopus japonicus (Crustacea, Copepoda) Young-Mi Lee a , Il-Chan Kim b , Sang-Oun Jung a , Jae-Seong Lee a, * a Department of Environmental Science, Graduate School, Hanyang University, Seoul 133-791, South Korea b Polar BioCenter, Korea Polar Research Institute, Korea Ocean Research & Development Institute, Ansan 426-744, South Korea Abstract The intertidal harpacticoid copepod Tigriopus japonicus is an important species in the study of marine pollution. To facilitate molecular biomonitoring using T. japonicus, we constructed a T. japonicus unidirectional cDNA library using kZAP expression vec- tor, excised to pBluescript vector with the aid of helper phage, and analyzed 686 randomly picked expressed sequence tags (ESTs) from this species. From the 686 ESTs sequenced, we found several functional genes such as vitellin, kinases and potential detoxi- fication-related genes. We are now preparing a T. japonicus cDNA chip for molecular ecotoxicological studies. In this paper, we discuss the potential use of T. japonicus ESTs and their importance in ecotoxicology. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Copepod; Tigriopus japonicus; Expressed sequence tag; EST 1. Introduction The collection of expressed sequence tags (ESTs) is important to identify expressed genes in cells or specific tissues, clarifying gene functions and tissue physiology (Adams et al., 1991; Ju et al., 2000). However, in cope- pods, the only k cDNA libraries available were made from Tigriopus californicus (Rawson et al., 2000; Raw- son and Burton, 2002), Artemia sp. and Daphnia magna. Of these, the Burton group, who are studying T. califor- nicus, have not yet collected a large number of ESTs. As the infrastructure for genetic study in copepods was still inadequate, the analysis of expressed genes in the genus Tigriopus and related copepod species will facilitate further study. The genus Tigriopus (T. japonicus, T. californicus and T. brevicornis) is recognized as important for testing coastal environmental contamination, as individuals are easy to capture from a single tidal rock pool and easy to maintain in the laboratory. They also have the advantage of a small genome size (ffi200 Mb) (Wyng- aard and Rasch, 2000). Tigriopus japonicus is known to be common along the coast of Korea (Song and Chang, 1993). T. japonicus is easily distinguished by its bright orange colored body. It colonizes the splash pools on the rocky shores all year round except for the winter in Korea (Kim et al., 2003). It has been used extensively for in vivo testing in ecotoxicology (Misitano and Schi- ewe, 1990; Forget et al., 1998; Barka et al., 2001; Ara et al., 2002; Forget et al., 2003; Marcial et al., 2003). However, to expand our knowledge to a molecular bio- logical level, it would be necessary to characterize important biomarker genes including those for phase I and II detoxification enzymes from hepatopancreas. This will improve our understanding of the effects of coastal pollutants on these intertidal species. To date, the Burton group has focusing research on the evolution of T. californicus using the mitochondrial cytochrome b gene and the genomic cytochrome c gene of the electron transport system (Willett and Burton, 0025-326X/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.marpolbul.2005.02.014 * Corresponding author. E-mail address: jslee2@hanyang.ac.kr (J.-S. Lee). www.elsevier.com/locate/marpolbul Marine Pollution Bulletin 51 (2005) 757–768