J. Ocean Univ. China (Oceanic and Coastal Sea Research) DOI 10.1007/s11802-012-1885-y ISSN 1672-5182, 2012 11 (2): 174-180 http://www.ouc.edu.cn/xbywb/ E-mail: xbywb@ouc.edu.cn Embryology of Maldives Clownfish, Amphiprion nigripes (Amphiprioninae) Swagat Ghosh * , Thipramalai Thankappanpillai Ajith Kumar, and Thangavel Balasubramanian Centre of Advanced Study in Marine Biology, Faculty of Marine Sciences, Annamalai University, Parangipettai-608 502, Tamil Nadu, India (Received August 25, 2011; revised December 22, 2011; accepted January 16, 2012) © Ocean University of China, Science Press and Spring-Verlag Berlin Heidelberg 2012 Abstract This study investigated the embryonic development of Maldives clownfish Amphiprion nigripes under natural conditions (28 – 30℃) at a lagoon of Agatti Island, Lakshadweep, India. The newly deposited fish egg was capsule-shaped and orange-red, with a (0.73 ± 0.04) mm 3 yolk containing 5 – 10 fat globules. The embryonic development of fertilized eggs was divided into 26 stages and the time elapsing for each stage was recorded. Results showed that the cleavage was rapid, with the first division observed 1 h 20 min after fertilization. Blastulation occurred 4 h later, followed by gastrulation 12 h after fertilization, with a yolk volume of (0.61 ± 0.06) mm 3 . The organogenesis process started 22 h after fertilization when the blastopores closed and notochord formation began. The embryonic stage was recorded 24 h later, with the appearance of forebrain, midbrain, hindbrain, melanophores on yolk-sac and 22 somites, and a decreased yolk volume of (0.54 ± 0.08) mm 3 . Other organs developed well 31 h after fertilization, whereas the heart started beating and blood circulation began 78 h later. Red pigmentation (erytrophores) appeared 96 h after fertilization, with a small yolk volume of (0.22 ± 0.02) mm 3 . Mouth developed well and eyes were noticeable 120 h later, with head, pectoral fin and tail fre- quently moving 144 h after fertilization. The embryo reached the pre-hatching stage 168 h later and started to hatch after 170 – 180 h incubation. This study first detailed the embryonic development and yolk absorption of A. nigripes under natural conditions. Keywords Amphiprion nigripes; clownfish; embryonic development; spawning; yolk volume 1 Introduction Breeding patterns and behavioural aspects of many tropical and sub-tropical Pomacentrid fishes have been well documented (Gopakumar et al., 1999, Ignatius et al., 2001, Ajith Kumar et al., 2010, Swagat, 2010). However, the description of fish eggs and associated embryological studies are lacking, particularly for those species from the Indian waters. Balon’s (1975) salutatory model and ter- minology of ontogeny are holistic and there are compel- ling arguments for their adaptation (Balon, 1990, 1999). The formation of a competent oocyte in fish eggs is one of the most fully elaborated processes in cells, and the observation of morphological characters during an early stage of embryonic development is considered to be a reliable and practical method for evaluation of the quality or viability of teleost eggs (Vallin and Nissling, 1998). The embryonic development of fish refers to the period during which the developing individual is entirely de- pendent on nutrients provided by the yolk from the egg (Liew et al., 2006). The exact state of embryonic deve- * Corresponding author. Tel: 0091-4144-253999 E-mail: swagotor@gmail.com lopment to hatch varies with fish species and environ- mental conditions. Once the embryo is free of egg mem- branes, the free-embryo phase begins. During this period, the embryo ceases to be coiled and becomes increasingly fish-like, but it continues to rely on the yolk for nutrient supply and usually remains in the original environment. The embryonic period begins upon the fertilization, and can be divided into two phases. The first is the egg cleav- age phase, which is the interval between the first cell di- vision and appearance of recognizable predecessors of the organ system, especially the neural plate. The second is the embryo phase during which the embryo becomes rec- ognizable as a vertebrate (Moyle and Cech, 2004). Job- ling (2002) suggested that embryonic period includes the time between fertilization and commencement of organo- genesis. The larval period is signified by the appearance of the ability to capture food (Chen, 2005). Despite previous desciption of Amphiprioninae em- bryonic development by Allen (1974) and Wilkerson (2001), detailed information is lacking regarding the early embryonic development of Amphiprion nigripes found in the Indian Ocean only, particularly the Indian waters such as Maldives, Sri Lanka (Allen, 1991) and Lakshadweep (Swagat, 2010). Previously, Hoff (1996) studied the egg development of the anemonefish, A. ocellaris, whereas