"FACTORS THAT CONTROL SKELETALFORMATION IN FISH INCLUDE:Scientists have for a long time linked skeletal formation in fish to geneticmake-up of thefish species in question (Gilligan et al ,2002 ; Yu et al,2008).Genes therefore have beenconfirmed to be involved in different stages and role in the process of skeletal development infish (D’Souza et al,2013 ; Vankatesh,2003).There are vertebrae genes in fish which controlthe physiology and development of bones and skeleton of fish (Amores et al.,1998 ;Christoffels et al.,2004 ; Prohaska and Stadler,2004).The proteins involved in cartilage andbone formation during skeletogenesis depends on genes that control the transcription process( D’Souza et al., 2013 ; Hartmann and Tabin,2000 ; Day et al., 2005).The beta catenin groupof genes have been also found to influence and control skeletal development in elephantshark fish Callorhinchus milii) which is a cartilaginous fish through control of skeletalformation process such as cell differentiation (Hartmann,2007).These genes in particular asexpressed in Callorhinchus milii fish dertermine the rate of sketeltal growththrough controlof the maturation process of the chordrocytes to endochondral ossification ( Zhu et al., 2009 ; Day et al., 2005 ).A number of genes have also been identified in the sea bream fish involvedin mineralisation process ( Tiago et al., 20011 ; Ferraresso et al., 2008). Tenascin andthrombospondin are some of the annotated genes discovered in fish with specific roles inskeletal growth particularly in osteoblast cell differentiation and mineralisation which controlthe entire process of skeletal formation in such fish ( Pombinho et al., 2004 ; Rafael et al.,2006).Nutrition or feeding is one the factosr that are implicated to regulate and control skeletaldevelopment in fish (Cahu et al., 2003).Feeding is regards as a major factor that controls skeletal formation since almost all minerals and vitamins must be supplied through the diet which must be balanced in such as way that all the required nutrients are provided in their right proportions (NIFES,2015).Minerals like magnesium,zinc and manganese play a greaterfunction in skeletal growth by acting as co-factors to various enzymes that have particularroles in the process of skeletogenesis in fish (Sadler et al., 2001).Other important nutrientsinclude the fatty acid and glycerol especially the polyunsaturated fatty acids a role ofinducing skeletal development through the process of mineralisation (Fontagne,2012).Many abnormalities of the skeleton have been observed in fish due to poor feeding,for example,scoliosis which are spinal malformations, coiled vertebral column,small and short and few finrays,malformations of the jaws and operculum,among others(Divanach et al.,1996) insalmonids and other fish species. Even vitamins such as A and C equally have a role inskeletogenesis in fish(Dabrowski et al., 1998). Merchie et al.(1995) and Covey et al.( 1985)in their experiments regarding the role of vitamins, it was discovered that providing sufficientamount of ascorbic acid to juvenile fish improved the rate of skeletal growth. Different fish species have varying vitamin requirement for example the carp larvae require45mg per kilogram of dry matter of ascorbic acid (Gouillbou-Coustanset al., 1998) while theturbot and european sea bass need20mg of dry matter ascorbic acid at a weaning stage (oillous – constants et al., 1998).Geurden et al.(1997) further urged that lipids likephosphatidylchline accelerates sketetal growth and prevents skeletal deformities in fish suchas the Cyprinus carpio. Kanazawa et al.(1983) concluded from his trial experiments thatphospholipids inclusion in the diet of fish in the right amounts up to 5% greatly reduceskeletal deformation of the jaw and scoliosis in rock bream and Plecoglossus altivelis . Toxins are another factor that control skeletal development in fish (Heideman et al.,2013). There are quite many toxins that have impact on the process of bone formation infish,one of them being dioxin which reduce the rate of cell different during skeletal formation(Safe et al., 1998 ; Rowland and Gustafsson,1997). exposure of tetrachlorodibenz-dioxin tozebra fish showed permanent skeletal deformities and short term general developmentaleffects ( Antkiewicz et al., 2005 ; Heideman at al., 2013). Examples of deformities in fishinclude head and axial skeleton malformations. Vasconcelos et al.(2010) argued that sometoxins that affect skeletal growth are produced by bacteria and phytoplankton liketetrodotoxin, okadaic acid brevetoxins,among others. Zinc chloride is yet another toxincapable of making fish develop malformed skeletal bones in fish. This toxin in particularinterferes with deoxyribonucleic acids synthesis which affects protein formations that arenecessary for cell growth in the matrix (Burundo et al., 2016).Replacement of fishmeal impacts on skeleton formation in fish in the following way:Replacing fismeal has far reaching impacts on skeletal formation and development in fishthrough provision of imbalanced and insufficient nutrients by fishmeal replacement which arenecessary for skeletal formation in the farmed fish (Darias et al., 20011).Very low levels ofvitamin C or ascorbic acid as in many fish meal replacement like the case of soybeanmeal disrupts the profile of genes that are involved in skeletogenesis in the farmed fish ( Mazuriaset al., 2009 ; Darias et al., 2010 ; Villeneuve et al., 2006).Fernandez et al. (2009) pointed outthat vitamin C plays a key role in skeletal formation and unfortunately it cannot besynthesised by farmed fish leaving dietary source as the only option, short of which resultsinto skeletal malformations. Resorption of the opercula as well as poor cartilage developmentparticularly in the gills are among the most noticeable skeletal deformities due to lower levelsof ascorbic acid in farmed fish (Soliman et al., 1986 ; Hilomen –Garcia,1997). Thesedeformities have been observed in the european sea bass ( Dicentralkuis labrax) and otherfarmed fish species and they are an indication that ascorbic acid is involved in collagen andcartilage formation during the ontogeny stage of skeletal formation (Terova et al., 1998,Darias,et al.,2011) hence a 30 mg of ascorbic acid per kg diet recommended So as satisfy itsrequirements for ossification during skeletogenesis (Darias et al ,2011).Amounts of ascorbicacid higherthan this recommended in farmed fish is an added advantages in farmedfishgiven the level of interaction between ascorbic acid and vitamin E. This therefore means thatascorbic acid complements vitamin E availability( Diarias et al., 2010). Carinci et al.(2005)urged that ascorbic acid is also involved in osteablast differentiation and proliferation duringskeletogenesis which would be impaired if it is not supplied in the right proportions .fishmeal replacement like poultry and feather meals are cheap but contain low levels of vitaminswhich may have an impact on skeletogenesis ( Wang et al., 2006). Fishmeal contain higher levels of minerals such as phosphorus, manganese, zinc andmagnesium compared to feather meal, moringa leaf meal and other fish meal replacements(Watanabe et al., 1997).Therefore, replacing fish meal with such alternative sources wouldhave a negative impact on the process of skeletogenesis due to inadequate supply of suchminerals which are vital in skeletal development in the framed fish (Paul et al., 2015).Lowlevels of management cause skeletal deformities in the farmed fish particularly rainbow troutand carp (Satoh et al., 1983).Between 20- 30 mg per kilogram of dry diet is necessary foradequate functioning of the channel cat fish ( Gatlin and Wilsion ,1984).These minerals alsoplay a paRt as co-factors in different enzymes involved in skeletogenesis. Role of calcium, phosphorus and vitamin D in skeletal formationCalcium has a big role to play during skeletal formation in fish as in form of calciumphosphate necessary for calcification of bones which brings about the rigidity of the skeletal system in farmed fish (Lall, 2002). Calcium is also said to be involved in functioning ofmuscles attached to the skeletal system in fish through impulse transmission andneurotransmitter release across synapse (Herberger and Loretz ,2013). Amores ,A., Force,A.,Yan,Y.L.,Joly,L. and Amemiya ,C.( 1998).Zebrafish hox clusters andvertebrate genome evolution.science 282: 1711- 1714.Cahu,C.and Takeuchin, T.(2003).Nutritional components affecting skeletal development of larvae. 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