High dietary arachidonic acid levels affect the process of eye migration and head shape in pseudoalbino Senegalese sole Solea senegalensis early juveniles.

The effect of high dietary levels of arachidonic acid (ARA) on the eye migration and cranial bone remodelling processes in Senegalese sole Solea senegalensis early juveniles (age: 50 days post hatch) was evaluated by means of geometric morphometric analysis and alizarin red staining of cranial skeletal elements. The incidence of normally pigmented fish fed the control diet was 99·1 ± 0·3% (mean ± s.e.), whereas it was only 18·7 ± 7·5% for those fed high levels of ARA (ARA-H). The frequency of cranial deformities was significantly higher in fish fed ARA-H (95·1 ± 1·5%) than in those fed the control diet (1·9 ± 1·9%). Cranial deformities were significantly and negatively correlated with the incidence of normally pigmented animals (r² = -0·88, P < 0·001, n = 16). Thus, fish displaying pigmentary disorders differed in the position of their eyes with regard to the vertebral column and mouth axes, and by the interocular distance and head height, which were shorter than in fish not displaying pigmentary disorders. In addition to changes in the positioning of both eyes, pseudoalbino fish showed some ARA-induced osteological differences for some of the skeletal elements from the splanchnocranium (e.g. right premaxillary, dentary, angular, lacrimal, ceratohyal and branchiostegal rays) and neurocranium (e.g. sphenotic, left lateral ethmoid and left frontal) by comparison to normally pigmented specimens. Pseudoalbino fish also had teeth in both lower and upper jaws. This is the first study in Pleuronectiformes that describes impaired metamorphic relocation of the ocular side eye, the right eye in the case of S. senegalensis, whereas the left eye migrated into the ocular side almost normally.

Senegalese sole (Solea senegalensis) coping styles are consistent over time: behavioural and physiological responses during ontogenesis.

Individuals differ in how they cope with stressful situations along a behavioural continuum, being proactive and reactive at the extremes of this continuum. Proactive individuals are usually bold, highly active and take risks, while reactive organisms are generally shy, exhibit low activity and avoid risky situations. Definitions of stress coping styles state that proactive and reactive traits are consistent over time and across contexts. The present study evaluated the individual differences in stress coping style, physiological changes and reproductive status in Senegalese sole juveniles and breeders over three and two-years, respectively. To determine stress coping style, the fish were subjected to three individual (restraining, new environment, confinement) and one group screening test (risk taking). Both groups were tested on three occasions, juveniles were tested each year and adults were tested in the first year and twice (spring and autumn) in the second year. On the third year, a proportion of the juveniles initiated puberty and the reproductive status of all individuals was assessed and compared with their behavioural responses. Results demonstrated individual differences that were consistent with proactive and reactive traits in juveniles and breeders. Significant intra-individual repeatability and consistency of juveniles and breeder's behavioural responses were observed over time and across situations. In addition, glucocorticoid levels (cortisol) were consistent for individuals. Another result to highlight was that juveniles that past puberty and initiated gametogenesis had significant higher activity, risk predisposition and lower plasma cortisol levels compared to fish that remained immature (did not initiate puberty).