The presence of hyperostosis in Atlantic moonfish, Selene setapinnis (Mitchill, 1815) in the Brazilian Coast ˗ case report

The occurrence of hyperostotic bones is common in marine fish, especially in the Carangidae family, despite few records of this condition in fishes from Brazilian waters. The present study describes the occurrence of hyperostosis in Atlantic moonfish (Selene setapinnis) in, Rio de Janeiro State, Brazil. Radiographs of the fish specimens were taken and all of them presented hyperostosis in at least three different regions: cleithrum, pterygiophores and pleural ribs. The observed pattern is different from previously described for other species of the same genus. It is the first record for the species and a valuable contribution to the study of bone diseases in fishes from the Brazilian coast.


INTRODUCTION
The increase of periosteal osteogenesis that modifies normal bone morphology is defined as hyperostosis (Meunier et al., 2010). This condition causes bone thickening and swollen shape (Olsen, 1971;Desse et al., 1981;Meunier and Desse, 1986;Gauldie and Czochanska, 1990;Smith-Vaniz et al., 1995). Several families of marine teleost fishes are often described with the condition, although the etiology and implications remain unclear. Different hypothesis about this disorder have been proposed. Schlüter et al. (1992) suggested the presence of hyperostotic bones as a physiological response to chemically adverse environment. Gauldie and Czochanska (1990) described it as a possible genetic control. Lima et al. (2002)  non-pathological condition (Desse et al., 1981;Gauldie and Czochanska, 1990.;Smith-vaniz et al., 1995).
Hyperostotic bones is often observed in speciesspecific structures like haemal and neural spines, ribs, pterygiophores (Desse et al., 1981), despite of taxonomically related species can exhibit different patterns for hyperostosis (Smith-Vaniz et al., 1995). Tuna (2015) showed that the same individual can develop several affected regions simultaneously. Although the occurrence of hyperostosis apparently does not affect the consumption, it leads to a possible bacterial contamination and makes filleting difficult, causing loss of muscle tissue and imperfections in the cut (Giarratana et al., 2012;Ramos and Faisca., 2016) which can make filleting process impossible at industrial level (Lima et al., 2002). Smith-Vaniz et al (1995) describe the presence of this condition in 92 species divided into 22 families.
Even though a clear taxonomic pattern does not seem to exist, some studies demonstrate a high prevalence of hyperostosis in individuals from the Carangidae family (Smith-Vaniz et al., 1995;Béarez, 1997;Chanet, 2018), a family with several species of commercial importance in the southeast-south of the Brazilian coast (Report…, 2018). The present study reports the occurrence of hyperostosis in specimens of Selene setapinnis (Mitchill, 1815). This is the first case reported for hyperostosis in this species and one of the few cases reported in Brazilian waters.

MATERIALS AND METHODS
Nine specimens of Atlantic moonfish were acquired in the Cabo Frio region, Rio de Janeiro, Brazil. The specimens were identified, sexed and biometrics were performed for total length, standard length, and total weight. X-ray radiography was conducted using the X-ray equipment MAG 300mA, performed in collimator calibrated 50 Kv/160mA in radiographic cassettes of 35 x 43 and 24 x 30cm.The radiographic images were processed using the software Sante Dicom Viewer Pro.

RESULTS
The mean and standard deviation for the total length of the fishes were 38.8cm ±1.28cm (ranged from 36.5 to 40.5cm). The standard length averaged was 29.1cm ±1.58cm (ranged from 25.7 to 30.7cm). The average weight was 690.4g, with standard deviation ± 64.2grams (ranged from 614 to 783g). All specimens analyzed had skeletal deformities, varying in number and type of affected structures.
Hyperostosis was found in pterygiophores of all analyzed specimens. The number of pterygiophores affected ranged from 15 to 23. The presence of this condition on both sides of the cleithrum was also observed in almost all individuals, except for one male specimen. Seven individuals had deformations in the first pair of ribs. Hyperostosis in the supraoccipital, haemal spines, neural spines or other bones were absent ( Figure 1).

DISCUSSION
Only three structures were affected: cleithrum, ribs and pterygiophores. After the analysis of radiographic images, it was determined that with the pterygiophores the most affected structures considering the thickening and amount of bones ( Figure 2). Male and female specimens had their bones affected, corroborating with previous studies that reported the development of condition in both genders (Lima et al.;Paig-Tran et al.;. The observed pattern for S. setapinnis in the present work was different from the described in previous studies for other species of the same genus. Béarez (1997) reported the presence of condition in the supraoccipital region in skeletons of individuals from S. brevoorti (Gill, 1863) andS. peruviana (Guichenot, 1866) found in archaeological sites in Ecuador. Guzman and Polaco (2002) observed the hyperostosis in the cranial region, cleithrum and neural spines in three individuals of S. vomer and S. brevoorti from zooarchaeological collections in Mexico.
Different patterns in related species can be found (Smith-Vaniz et al., 1995;Rapisarda et al., 2008). Trichiurus lepturus (Linnaeus, 1758) collected in different studies (James, 1960;Lima et al., 2002;Al Nahdi et al., 2016) the incidence of individuals with hyperostosis ranged from 94.5% to 10.5%. These differences in presence versus absence of the condition and patterns could not be analyzed as a single factor. The occurrence of hyperostosis The presence… related to a genetic factor (Smith-Vaniz et al., 1995;Jawad, 2013) could explain the fact that species living in the same environment may present different prevalence, including the complete absence of condition. Physiological or environmental factors could justify the presence of this bone condition, as an aid to support the fin (erection aid), aging, temperatures, water chemical composition, pathogenic factors, floating aid, hydrostatic maintenance, hypersaline environments, among others (Murty, 1967;Meunier and Desse, 1986;Smith-Vaniz et al., 1995;Gaudant and Meunier, 1996;Chang et al., 2008;Meunier et al., 2008;Giarratana et al., 2012;Paig-Tran et al ., 2016;Chanet, 2018).

CONCLUSIONS
The present study is the first record of hyperostosis in different individuals of Selene setapinnis from southern-south waters of Brazil. The patterns described for the presence of hyperostosis differ from the affected bones of other species of the same genus. The cause of hyperostosis remains unclear and further research is necessary to elucidate future questions about the epidemiology of this disorder.