Synaptonemal complex analysis in spermatocytes and oocytes of turbot, Scophthalmus maximus (Pisces, Scophthalmidae)

A surface-spreading synaptonemal complex (SC) technique was used to analyze spermatocytes and oocytes of turbot (Scophthalmus maximus) to visualize the process of chromosome synapsis. The total SC length was 205 +/- 12 mum in males and 172 +/- 29 mum in the only female analyzed. A representative SC karyotype of turbot was obtained. Each SC showed lateral elements of equal length. No bivalent exhibiting atypical synaptic behaviour that could be associated with heteromorphic sex chromosomes was observed, either in males or in the female. The DNA content of turbot was evaluated in eight individuals of both sexes by flow cytometry analysis. The 2C mean DNA content of turbot (1.308 +/- 0.009 pg/cell) was among the lowest observed within fishes. No statistical differences in DNA content were revealed between the sexes [Wilcoxon/Mann-Whitney test; P(W-x = 0.243)]. The SC/DNA content ratio observed in turbot was the highest reported to date in bony fishes (Osteichthyes).