Ovarian Development of a River Catfish Hemibagrus nemurus (Valenciennes, 1840) in Captivity FATIMAT ADENIKE ADEBIYI 1 , SITI SHAPOR SIRAJ 1Ã , SHARR AZNI HARMIN 2 , AND ANNIE CHRISTIANUS 1 1 Department of Aquaculture, Faculty of Agriculture, Universiti Putra Malaysia, Selangor, Malaysia 2 Department of Aquatic Biotechnology, Faculty of Science and Technology, Universiti Industri Selangor, Selangor, Malaysia Hemibagrus nemurus is a riverine catfish with high economic and nutritive values. Investigations on ovarian development of this fish were carried out to determine the mode of ovarian development and describe the oocyte developmental stages. Histological studies were done on ovaries using light microscopy and scanning electron microscopy. Fish were sampled monthly for a period of six months (August 2009 to January 2010). The mean oocyte diameter (OD) ranged from 8717 161.41 mm to 1,167726.77 mm and the highest OD was in November. Oocyte size–frequency distribution showed a polymodal distribution. The mean gonadosomatic index (GSI) ranged from 1.1470.87% to 7.0671.40% and highest GSI was in November. The ovaries exhibited three phases of oocyte growth, which were primary growth, secondary growth and maturation phases. Based on histological criteria, the oocyte developmental stages were divided into seven stages as chromatin nucleolar, early perinucleolar, late perinucleolar, cortical alveolar, vitellogenesis, mature oocyte and germinal vesicle migration stages. All the seven stages of oocyte development were observed in the ovaries. Oogonia were always present throughout the developmental stages. The ovaries had more than two stages of oocyte development. This is the first report on the mode of ovarian development of H. nemurus. These findings indicated that H. nemurus has asynchronous mode of ovarian development and is capable of spawning several times in a year under favourable conditions. J. Exp. Zool. 315:536–543, 2011. & 2011 Wiley Periodicals, Inc. How to cite this article: Adebiyi FA, Siraj SS, Harmin SA, Christianus A. 2011. Ovarian development of a river catfish Hemibagrus nemurus (Valenciennes, 1840) in captivity. J. Exp. Zool. 315:536–543. The knowledge of reproductive biology of fish is very vital for successful fish culture. The gonads play an important role in reproduction. Hence, for fish to reproduce, the gonads need to be well developed and matured. Oogenesis and spermatogenesis are the two reproductive processes that occur in female and male fish during the reproductive cycle, leading to the production of mature oocytes and spermatocytes. During the process of oogenesis, the ovary undergoes different developmental stages, which include oocyte growth, development and maturation. Ovarian development occurs in three phases which are the primary growth phase, secondary growth phase and maturation phase (Coward and Bromage, ’98; Cek et al., 2001). During these phases the oocytes undergo a series of development. The primary growth phase is usually characterized by previtellogenic oocytes, while the secondary growth phase is characterized by vitellogenic oocytes Published online 6 September 2011 in Wiley Online Library (wileyonline library.com). DOI: 10.1002/jez.702 Received 5 March 2011; Revised 28 June 2011; Accepted 20 July 2011 Grant Sponsor: Ministry of Agriculture, Malaysia; Grant number: 5487718; Grant Sponsor: Internal Funding from Universiti Putra Malaysia. Abbreviation: ANOVA, Analysis of variance; GSI, Gonadosomatic index; OD, Oocyte diameter; OO, Oogonia; I, Chromatin nucleolar oocyte; II, Early perinucleolar oocyte; III, Late perinucleolar oocyte; IV, Cortical alveolar oocyte; V, Vitellogenic oocyte; VI, Mature oocyte; VII, Germinal vesicle migration oocyte. Ã Correspondence to: Siti Shapor Siraj, Department of Aquaculture, Faculty of Agriculture, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor, Malaysia. E-mail: shaporsiraj@yahoo.com; shapor@putra.upm.edu.my ABSTRACT J. Exp. Zool. 315:536–543, 2011 & 2011 WILEY PERIODICALS, INC. RESEARCH ARTICLE