Context : We present the study of a magnitude limited sample ( m _ { B } \leq 16.6 mag ) of 13 late type galaxies ( LTGs ) , observed inside the virial radius , R _ { vir } \sim 0.7 Mpc , of the Fornax cluster within the Fornax Deep Survey ( FDS ) .

Aims : The main objective is to use surface brightness profiles and g - i colour maps to obtain information on the internal structure of these galaxies and find signatures of the mechanisms that drive their evolution in high-density environment , which is inside the virial radius of the cluster .

Methods : By modelling galaxy isophotes , we extract the azimuthally averaged surface brightness profiles in four optical bands .
We also derive g - i colour profiles , and relevant structural parameters like total magnitude , and effective radius .
For 10 of the galaxies in this sample , we observe a clear discontinuity in their typical exponential surface brightness profiles , derive their “ break radius ” , and classify their disc-breaks into Type II ( down-bending ) or Type III ( up-bending ) .

Results : We find that Type-II galaxies have bluer average ( g - i ) colour in their outer discs while Type-III galaxies are redder .
The break radius increases with stellar mass and molecular gas mass while decreases with molecular gas-fractions .
The inner and outer scale-lengths increase monotonically with absolute magnitude , as found in other works .
For galaxies with CO ( 1-0 ) measurements , there is no detected cold gas beyond the break radius ( within the uncertainties ) .
In the context of morphological segregation of LTGs in clusters , we also find that , in Fornax , galaxies with morphological type 5 < T \leq 9 ( \sim 60 % of the sample ) are located beyond the high-density , ETG-dominated regions , however there is no correlation between T and the disc-break type .
We do not find any correlation between the average ( g - i ) colours and cluster-centric distance , but the colour-magnitude relation holds true .

Conclusions : The main results of this work suggest that the disc breaks of LTGs inside the virial radius of the Fornax cluster seem to have arisen through a variety of mechanisms ( e.g .
ram-pressure stripping , tidal disruption ) , which is evident in their outer-disc colours and the absence of molecular gas beyond their break radius in some cases .
This can result in a variety of stellar populations inside and outside the break radii .