Comparative study on the gamete quality, artificial propagation and larval development of common goldfish, shubunkin, black moor, and oranda variants of goldfish (Carassius auratus)

Due to the origin and diversity of goldfish, it is a suitable model organism to investigate the effect of artificial selection on reproduction and larval development. In the present study, four, well-known variants of goldfish (common goldfish, shubunkin, black moor, oranda) with considerable phenotypical differences were compared within the framework of gamete quality assessment, propagation trial, larvae rearing and morphology assessment. In our first experiment, sperm concentration, sperm volume per fish (sperm volume) and volume of sperm per kg of body weight of males did not differ significantly between the variants. Concerning the measured Computer-Assisted Sperm Analysis (CASA) system parameters, shubunkin and oranda had significantly higher progressive motility (pMOT, %) than black moor. Tendencies in female gamete production were observed in the second experiment, despite not all cases displaying significant differences. For pseudo-gonadosomatic index (PGSI, %), higher values were recorded for the globular-bodied goldfish, while the contrary was seen for the number of eggs per gram. Out of the four variants, a significantly higher fertilization rate was determined for oranda, while a significantly lower hatch rate was calculated for black moor. In the third experiment, a significant difference in the body length of freshly hatched larvae was observed between common goldfish and shubunkin during larvae rearing. However, at 3 days post-hatching (dph), shubunkin and oranda had a significant difference in this parameter. At 10 dph, common goldfish and shubunkin had significantly lower body weights than black moor and oranda. Moreover, developmental variances between common goldfish and black moor were observed in larvae morphology. At the end of larvae rearing, a significantly higher survival rate was recorded for common goldfish than for shubunkin and oranda. Even though not all parameters show considerable differences between the variants, black moor is far behind the others in terms of hatching rate and morphological abnormalities. Thousands of years of artificial selection have had a noticeable mark on the reproductive capacity and larval development of goldfish variants studied. Our results may contribute to further research on the impact of artificial selection on reproductive biology.