Assessment of spermatogenesis in harbour porpoises (Phocoena phocoena) from the North and Baltic Seas

Male germ cells (GC) are arranged within the seminiferous epithelium in a set of welldefined cellular associations called stages. The identification of these stages can be used to assess the developmental profile of gene expression during spermatogenesis and to identify defects in spermatogenesis arising in pathological conditions. Detailed knowledge on spermatogenesis in adult harbour porpoises (Phocoena phocoena) is restricted to a few studies. Though the seminiferous epithelium seems to comprise similar GC populations and somatic Sertoli cells like terrestrial wildlife species, spermatogenesis is additionally known to proceed in a seasonal pattern. No information is available about the number of stages in the porpoise testis. For that purpose, testes of 115 harbour porpoises from German and Dutch waters were collected at different time points of the year and histologically analyzed using HE staining. The selected sections were examined using the Periodic acid Schiff (PAS) reaction to assess spermatogenic stages. In order to complete staging and to detect spermatids, protamine 1 mRNA in-situ-hybridization was performed. Spermatogenesis in the high-mating season (July) is found to proceed in eight stages showing a multi-stage arrangement within one tubular cross section. An increasing number of missing GC generations from August to September has been encountered. Our data provide a detailed staging of spermatogenesis in harbour porpoises that might be useful for the detection of possible influences of endocrine disruptors on male reproductive biology in upcoming studies.