The course of gametogenesis in narrow-clawed crayfish (Astacus leptodactylus Eschscholtz, 1823) in the condition of water bodies of the Dnieper region

Purpose. Detailed study of the stages of reproductive development (oogenesis and spermatogenesis) of crayfish using the example of the narrow-clawed crayfish Astacus leptodactylus Eschscholtz, 1823 in reservoirs of the Dnieper region. Methodology. The study was conducted during the period of 2022-2023. The material for the study were individuals of the narrow-clayed crayfish A. leptodactilus. A morphometric analysis was performed, after which the crayfish were preserved in an alcohol solution (70% ethanol and 2% glycerol) for the slide of histological cross-sections. Histological slides of crayfish gonads were made in accordance with generally accepted histological methods. The analysis of the cross-sections was carried out using a microscope and a digital camera. Descriptions of the slides were made using atlases of histology of decapods. Findings. It has been found that the gonads exhibited an asynchronous development and were in stages C, D, E, F, with a significant number of oocytes in stage C. The diameter of oocytes in phase D mainly ranged from 195.72 ± 12.43 μm with an area of 38,21 μm². The nucleus had a diameter of 48.14 ± 1.44 μm. In phases E, the size of oocytes reached a diameter of 259.24 ± 76.18 μm and an area of 52,850 ± 5,760 μm². Throughout phase D, the diameter of vacuoles was 18.45 ± 0.86 μm. In phase E, the diameter of vacuoles increased to 26.55 ± 1.24 μm, and as soon as in the transitional phase E–F, vacuoles merged massively with individual non-merging vacuoles having a diameter of 25.22 ± 1.12 μm. At the terminal stage F, oocytes reached definitive sizes and were ready for ovulation. The average size of larvae was 2600 ± 0.093 μm in diameter. The course of spermatogenesis in crayfish males was characterized by synchronous development of gametes. The analysis of sections showed that the area of spermatocytes was 43.14 ± 0.74 μm2 with a diameter of 7.14 ± 0.23 μm. In turn, the nuclei of spermatocytes had dimensions of 21.64 ± 0.35 μm2 and 5.24 ± 0.02 μm in diameter. Originality. A comprehensive analysis of crayfish gametogenesis was conducted for the first time in the zones of the reproductive range of the Dnieper reservoirs. Some features of the stages of oogenesis and spermatogenesis were identified and the impact of the ecological regime on the reproduction of crayfish was studied.