Effect of temperature on the development of skeletal deformities in Gilthead seabream (Sparus aurata Linnaeus, 1758) E. Georgakopoulou a , P. Katharios b , P. Divanach b , G. Koumoundouros a,c, ⁎ a Biology Department, University of Patras, 26500 Rio, Patras, Greece b Hellenic Center for Marine Research, Institute of Aquaculture, P.O. Box 2214, 71003 Heraklio, Crete, Greece c Biology Department, University of Crete, Vasilica Vouton, P.O. Box 2208, 71409 Heraklio, Crete, Greece abstract article info Article history: Received 29 December 2009 Received in revised form 5 August 2010 Accepted 6 August 2010 Keywords: Eggs Marine fish larvae Abnormalities Gill-cover Fins The development of skeletal deformities is an important problem for finfish hatcheries. In the present paper, the effect of water temperature on the development of skeletal deformities in Sparus aurata was examined. Six combinations of three temperatures (16, 19, and 22 °C) were applied during three ontogenetic windows: the autotrophic (embryonic and yolk-sac larval stages), the exotrophic larval (first feeding to metamorphosing larvae of 14–16 mm TL) and the juvenile (metamorphosing larvae of 14–16 mm TL to juveniles of 40–45 mm TL) periods. The results demonstrated a significant effect (p b 0.05) of water temperature on the development of inside folded gill-cover, haemal lordosis, as well as of mild deformities of the caudal and dorsal fin-supporting elements. The prevalence of gill-cover deformities was elevated when 16 °C water temperature was applied during the autotrophic and exotrophic larval periods (50.0 ± 2.8%, mean ± SD), or only during the autotrophic period (14.0 ± 0.0%). Haemal lordosis development, the second most severe skeletal deformity, presented fluctuating response against water temperature up to 14–16 mm TL (3.0 ± 4.2 to 13.0 ± 9.9%). However, the application of 22 °C during the juvenile period resulted in the lowest and less variable incidence of haemal lordosis (1.0 ± 0.0 to 5.0 ± 1.4%). The mild deformities of caudal and dorsal fins presented different responses to water temperature. The prevalence of caudal-fin deformities was elevated when 16 °C temperature was applied during the exotrophic larval period (54.0 ± 8.5%), while dorsal-fin deformities were favoured when 22 °C temperature was applied during the autotrophic and exotrophic phases (35.0 ± 9.9 to 39.0 ± 4.2%). In the examined thermal range, growth rate was significantly elevated with the temperature increase. Fish survival was higher in the treatments where temperature after yolk-consumption increased from 16 or 19 °C to 19 or 22 °C, respectively. The results are discussed in respect to the onset of ontogeny of the different skeletal elements and the need of applying different thermal conditions during the development of S. aurata. © 2010 Elsevier B.V. All rights reserved. 1. Introduction Skeletal deformities are one of the most significant biological problems for marine finfish hatcheries. Official data on the incidence of deformities in commercial hatcheries are lacking. Results from case studies of quality control in marine hatcheries during the last 15 years, show that skeletal deformities affect 7–20% on average of the produced juveniles, whereas occasionally this incidence has been shown to elevate at 45–100% (Koumoundouros, unpublished data). The development of deformities in reared fish is, to a great extent, the result of knowledge gaps on the environmental (including nutritional) optima of the early life stages of fish. A variety of abiotic (e.g. Tandler et al., 1995; Kihara et al., 2002; Trotter et al., 2003; Sfakianakis et al., 2006; Cobcroft and Battaglene, 2009) and nutritional (e.g. Takeuchi et al., 1998; Gapasin and Duray, 2001; Haga et al., 2003; Mazurais et al., 2009; Darias et al., 2010) conditions have been proven significant in the development of skeletal deformities, but skeletal deformities continue to downgrade hatcheries' production, even in the case of well studied species (e.g. Dicentrarchus labrax and Sparus aurata). This fact could be at least partially explained by the lack of studies on the combined effects of more than one factor (e.g. Sfakianakis et al., 2006) and by the underestimation of the changing environmental and nutritional optima during the ontogeny of a given species (e.g. Mazurais et al., 2009). Water temperature is a critical factor for the successful hatchery production, as it significantly affects growth, differentiation and survival rates. Optimum temperature conditions have been studied in a variety of fish species, mainly in respect to growth, survival, developmental rates and early morphological abnormalities (e.g. Marangos et al., 1986; Polo et al., 1991; Ottesen and Bolla, 1998; Koumoundouros et al., 2001b; Klimogianni et al., 2004; Sfakianakis et al., 2004; Martell et al., 2005). To our knowledge, the literature on the thermal optima for normal skeletal development is rare (e.g. Aquaculture 308 (2010) 13–19 ⁎ Corresponding author. Biology Department, University of Patras, 26500 Rio, Patras, Greece. Tel./fax: + 30 2610969217. E-mail addresses: koumound@upatras.gr, gkoumound@biology.uoc.gr (G. Koumoundouros). 0044-8486/$ – see front matter © 2010 Elsevier B.V. All rights reserved. doi:10.1016/j.aquaculture.2010.08.006 Contents lists available at ScienceDirect Aquaculture journal homepage: www.elsevier.com/locate/aqua-online