3.6. Morphological characterization of carp skin collagens and ultrastructure by SEM As shown in Fig. 4, all collagens appeared to be irregular dense sheet-like film under SEM, and the surface was partially wrinkled. The ultrastructure of all ASC and PSC were found to be similar based on SEM analysis. The pore size of collagen increased with higher water content during its preparation. These might be due to the dehydration while freeze drying (Li et al., 2013; Veeruraj et al., 2013). Thus, the collagens (ASC and PSC) extracted from the skin of catla and rohu can be used for the manufacture of homogeneous porous collagen devices and scaffolds.