Environmental Conditioning of Skeletal Anomalies Typology and Frequency in Gilthead Seabream (Sparus aurata L., 1758) Juveniles

Abstract

In this paper, 981 reared juveniles of gilthead seabream (Sparus aurata) were analysed, 721 of which were from a commercial hatchery located in Northern Italy (Venice, Italy) and 260 from the Hellenic Center for Marine Research (Crete, Greece). These individuals were from 4 different egg batches, for a total of 10 different lots. Each egg batch was split into two lots after hatching, and reared with two different methodologies: intensive and semi-intensive. All fish were subjected to processing for skeletal anomaly and meristic count analysis. The aims involved: (1) quantitatively and qualitatively analyzing whether differences in skeletal elements arise between siblings and, if so, what they are; (2) investigating if any skeletal bone tissue/ossification is specifically affected by changing environmental rearing conditions; and (3) contributing to the identification of the best practices for gilthead seabream larval rearing in order to lower the deformity rates, without selections. The results obtained in this study highlighted that: i) in all the semi-intensive lots, the bones having intramembranous ossification showed a consistently lower incidence of anomalies; ii) the same clear pattern was not observed in the skeletal elements whose ossification process requires a cartilaginous precursor. It is thus possible to ameliorate the morphological quality (by reducing the incidence of severe skeletal anomalies and the variability in meristic counts of dermal bones) of reared seabream juveniles by lowering the stocking densities (maximum 16 larvae/L) and increasing the volume of the hatchery rearing tanks (minimum 40 m3). Feeding larvae with a wide variety of live (wild) preys seems further to improve juvenile skeletal quality. Additionally, analysis of the morphological quality of juveniles reared under two different semi-intensive conditions, Mesocosm and Large Volumes, highlighted a somewhat greater capacity of Large Volumes to significantly augment the gap with siblings reared in intensive (conventional) modality.

Normal and histopathological organization of the opercular bone and vertebrae in gilthead sea bream Sparus aurata

“…However, such differences may be attributed to different rearing conditions and improvements in the rearing procedures over the last 2 decades (Koumoundouros 2010, Prestinicola et al 2013. Opercular anomalies detected in gilthead sea bream juveniles were randomly distributed on both sides of the head, which was in agreement with previous data reported by Beraldo et al (2003).…”

“…In this study, the frequency of lordotic vertebrae (10.1%) was within the normal range found in other studies and hatcheries (Andrades et al 1996, Koumoundouros et al 2002, Prestinicola et al 2013. The aetiology of this skeletal disorder might vary depending on the rearing and environmental conditions (see reviews in Koumoundouros 2010, Boglione et al 2013a).…”

“…Vertebral column malformations may occur frequently in the wild, but are rarely detected (Gavaia et al 2009) whereas they are quite commonly detected under intensive aquaculture conditions (Kranenbarg et al 2005, Koumoundouros 2010, Prestinicola et al 2013. In this study, the frequency of lordotic vertebrae (10.1%) was within the normal range found in other studies and hatcheries (Andrades et al 1996, Koumoundouros et al 2002, Prestinicola et al 2013.…”

“…Although the improvement and refinement of rearing techniques have considerably reduced the frequency of these types of deformities (Boglione et al 2013a), lordosis and kyphosis are still 2 of the most relevant osteological abnormalities observed in the axial skeleton of reared gilthead sea bream, while a partial and/or total lack of operculum is the most frequent anomaly affecting its cranial region (Koumoundouros et al 1997b, Boglione et al 2001, 2013b, Beraldo et al 2003, Verhaegen et al 2007, Castro et al 2008, Koumoundouros 2010, Prestinicola et al 2013). Several studies have described skeletogenesis in gilthead sea bream (Faustino & Power 1998, 1999, 2001) and the typology of fish skeletal deformities (Witten et al 2009, Boglione et al 2013b, Prestinicola et al 2013, among others) in order to better understand the phases of skeletogenesis and the effects of biotic and abiotic factors on the proper development of bone and the appearance of skeletal anomalies. Various procedures have been used as simple and rapid diagnostic tools for studying skeletal deformities in fish, such as X-rays, double staining or even computer tomography; allowing the identification of abnormal growth in different skeletal structures (see reviews in Witten et al 2009, Koumoundouros 2010, Boglione et al 2013b.…”

Relationship between uninflated swim bladder and skeletal anomalies in reared gilthead seabream (Sparus aurata)

“…The aim was to detect a possible relationship between the absence of swim bladder and some skeletal bone anomalies, using a standardised protocol (Boglione et al, 2009(Boglione et al, , 2006(Boglione et al, , 2003(Boglione et al, , 2001Prestinicola et al, 2013) for monitoring skeletal anomalies.…”