Levantamento radiológico das deformidades vertebrais de Tambaqui Colossoma Macropomum (Cuvier, 1818) (Characiformes, Serrasalmidae) de cultivo

Abstract

Skeletal deformities are malformations found in fish that can affect animal welfare and negatively impact zootechnical performance and reproductive behavior. In aquaculture, the incidence of skeletal deformities can cause damage and waste. In Brazil, the tambaqui Colossoma macropomum (Teleostei: Serrasalmidae) is the second most cultivated fish species in continental aquaculture. Since the incidence of deformities has not yet been reported for tambaqui, and that this is relevant for phenotypic characterization in species improvement programs, the objective of this work was to describe the occurrence of different types of skeletal deformities found in tambaqui families produced in captivity. After 90 days post-hatch DPE (body weight ~ 50g) was inserted with an intramuscular chip (Passive Integrated Transponder - PIT) in all fish, and individuals were selected based on size and Total Length (TL) and transferred to excavated tanks to compose a breeding program. At this stage, fish that had any external abnormality were selected (n = 660 in total) for the present study, when they were sacrificed with a lethal dose of Benzocaine (220 mg.L-1), fixed in 100% ethanol for further analysis X-ray. The X-ray images in Dicom format were treated, and a 20 mm scale was added to each one using the ImageJ program (v1.51j8). Then, a file in format (tps) was generated (tpsUtil64 v1.76), and landmarks were “digitized” over the center of each vertebra (tpsDig v2.31). Using the family and deformity variables, a principal component analysis (PCA) was performed using the MorphoJ program (v1.06d) in order to verify the presence of outliers (digitizing errors). All X-ray images were carefully examined in order to characterize the different types of vertebral deformities in the species. As a result, this study identified 13 types of vertebral deformity, namely: 1) reduction of intervertebral spaces; 2) homogeneous compression; 3) compression without “X-structure”; 4) unilateral compression; 5) fusion and compression; 6) spinal stretching; 7) superior biconcave with a decalcified center; 8) complete fusion; 9) pronounced biconcave; 10) hyper-radiodense; 11) kyphosis; 12) irregular internal structure; 13) dorsal or ventral displacement; and 14) severe multiple malformation. These deformities were illustrated and described. This study advances the existing knowledge about the types of deformity in tambaqui, which is necessary for future work to investigate its causes. It is known that several factors can influence the appearance of such deformities (i.e. incubation temperature, malnutrition, management, triploidization and genetic factors), which can be better investigated based on this basic work of description.