The effect of male colouration on reproductive success in Nile tilapia (Oreochromis niloticus)

Abstract

Body colouration in tilapia is an important trait affecting consumer preference. In the Nile tilapia (Oreochromis niloticus), there are three colour variants which are normal (wild type), red and blond. In some countries, the red variant is important and reaches higher prices in the market. However, one major problem regarding red tilapia culture is their body colouration which is often associated with blotching (mainly black but also red) which is undesirable for the consumer. The overall aim of this work was to expand knowledge on various aspects of body colouration in Nile tilapia using genetic approaches. The results of this research are presented as four different manuscripts.The manuscripts (here referred as Papers) have either been published (Paper IV) or are to be submitted (Paper I, II and III) in relevant peer reviewed journals.Paper I and II investigated the inheritance of black blotching and other body colour components of the red body colour. Specifically, Paper I consisted of two preliminary trials (Trial 1 and 2), to look at the ontogeny of black blotching and body colour components over a period of six months. Trial 1 investigated the effect of tank background colour (light vs dark) on black blotching and other body colour components and was carried out using a fully inbred (all female) clonal red line. Trial 2 was carried out using mixed sex fish and was aimed to investigate the association of black blotching with the sex of the fish. The results from this study were used to guide the experiment described in Paper II. Sixteen red sires with various levels of black and red blotching were crossed to clonal females and the inheritance of blotching and other body colour components were investigated using parent-offspring regressions. The results showed no significant heritability for black blotching and body redness, but a significant niloticus) were used as mapping families and the blond locus was located in LG5. Four out of eight markers were successfully used to assess the interaction of blond on red blotched fish. The blond gene did not significantly reduce the area of blotching but did reduce the saturation (paler blotching) and enhanced the redness of body colour in the Rrblbl fish compared to the RrBlbl group.Finally, Paper IV aimed to find out the effect of male colouration on reproductive success in Nile tilapia. A choice of one wild type male and one red male was presented to red or wild type females and these fish were allowed to spawn under semi-natural spawning conditions. Eggs were collected from the female"s mouth after spawning and paternity was assessed using microsatellite genotyping and phenotype scoring. No significant departures from equal mating success were observed between the red and wild type males, however there was a significant difference between the red and wild The results from this research help to broaden our knowledge and understanding on the aspects of body colouration in Nile tilapia and provide fundamental information for further research.

DNA sampling from mucus in the Nile tilapia,Oreochromis niloticus: minimally invasive sampling for aquaculture-related genetics research

“…All the samples were genotyped for one microsatellite locus ( UNH995 ) and two SNP markers ( Oni23063 and Oni28137 ) using a CEQ ™ 8800 sequencer (Beckman Coulter ® , Fullerton, CA, USA) and the Kompetitive Allele Specific PCR (KASP) genotyping system (KBioscience, Teddington, Middlesex, UK) following the methods described by Rajaee, Huntingford, Ranson, McAndrew and Penman () and Palaiokostas, Bekaert, Khan, Taggart, Gharbi, McAndrew and Penman () respectively. Selected mucus and fin sample DNA were also amplified using universal bacterial primers (16S rDNA) to estimate the relative abundance of bacterial DNA (minor modifications from Hovda, Sivertsvik, Lunestad, Lorentzen & Rosnes ).…”

Patterns of colour inheritance from crossbreeding between Red hybrid tilapia (Oreochromis sp.) and GIFT tilapia (Oreochromis niloticus)

“…The production of GIFT (Genetically Improved Farm Tilapia) strain is an example of highly successful selective breeding programme utilizing genetic variability and heritability information of population level broodstocks of a single species (Oreochromis niloticus) (Hamzah et al, 2014). On the other hand, crossbreeding or hybridization among different tilapia species, either naturally or through artificial propagation has resulted in the production of various strains of Red hybrid tilapia (Watanabe et al, 2002;Rajaee et al, 2010).…”

“…Although the initial genetic records on the production of Red hybrid tilapia is not well documented, their derivation is generally attributed to crossbreeding between a mutant reddish orange O. mossambicus with other species including normal O. aureus, O. niloticus, and O. hornorum (Watanabe et al, 2002). The aims are generally to obtain other desirable traits such as faster growth rate or higher tolerance towards cold temperature or salinity (Rajaee et al, 2010). Nowadays, Red hybrid tilapia strain is one of the most popular tilapia cultures in most countries in Southeast Asia and make up to 85% of total tilapia production in Malaysia (Ng and Hanim, 2007).…”

“…Studies on the pattern of inheritance of colour and pigmentation in tilapia has been documented by Pongthana et al, 2010 andRajaee et al, 2010), however, the molecular mechanism responsible for the determination of colour and pigmentation is still poorly understood. Accordingly, most of the red genotype of Red hybrid tilapia strains are predicted to be controlled by a single dominant trait (either homozygous dominant RR or heterozygous Rr), while the recessive wild type is homozygous recessive (rr) (Wohlfarth et al, 1990;Huang et al,1988).…”

“…This includes the Thai strain, Philippine red and Sterling strain. Meanwhile, the Taiwanese and Fijiian strains both exhibit pink body colouration for the homozygous dominant RR allele (Rajaee et al, 2010). In addition, the red colour is often associated with spots or blotches (mainly black but also red) which makes the fish less attractive and affects their market prices.…”