Characteristics of the first blastomeres in fish have been evaluated in previous studies as a predictive tool for egg and larval quality. Nevertheless, the presence of inclusions in fish blastodisc is still poorly informed. In the present report, we describe the relationship between cellular inclusions and some embryonic quality parameters (symmetry, fertility rate, survival rate) in farmed coho salmon. Egg from 261 females were fertilized with 400 × 103 spermatozoa/ egg and incubated in the dark in separated flowthrough incubators. In the stage of four cells, embryos from 60 females were fixed in Stockard’s solution and the blastodiscs were classified as i) unfertilized, ii) fertilized with inclusion and iii) without inclusion. The blastomeres symmetry was also registered. Embryos from 30 females (15 with and 15 without inclusions) were incubated until pigmented eye embryo stage to determine the survival rate.
Cell inclusions were detected in 8.81% of the evaluated females, 24.1± 24.2 of the egg from those females showed cellular inclusions. The inclusions are variable in size and deep, in fact they can occupy about 50% of the blastodisc volume or going beyond all the cell (Figure 1).
Egg samples with this abnormality showed significantly lower fertility, blastomeres symmetry, and survival rate when compared with those cells without inclusions (Figure 2). Further studies should focus on the assessment of oocyte in different aged stages to verify the incidence of these structures.