Sexually dimorphic skin glands in the invasive species Lithobates catesbeianus (Anura:Ranidae)

Males of most amphibian species possess specialized cutaneous glands, known as sexually dimorphic skin glands (SDSGs). SDSGs are usually clustered in specific body regions and are externally visible, but in some cases, external differences between males and females can be slight or absent, and the occurrence of SDSGs can only be disclosed by histological studies. Chemical signals produced by SDSGs markedly affect amphibian behaviour and reproduction, and therefore their occurrence, features, and location in the body could provide information on potential mechanisms of intraspecific communication in a particular species. In the present study, we perform light microscope (both histological and histochemical), and scanning electron microscope studies of skin samples from male and female adult specimens of the invasive bullfrog Lithobates catesbeianus, covering several body regions that could hold SDSGs. Most skin areas analysed showed only ordinary granular and mucous glands despite remarkable sexual dimorphism that could be externally observed. By contrast, the male nuptial pads contained exclusively SDSGs that were hypertrophied specialized mucous glands (SMGs), closely resembling breeding glands described in other anurans. Our histochemical study revealed that these SMGs contain heterogeneous populations of secretory cells, possibly involved in pheromone production. We discuss these characteristics of the SDSGs found in L. catesbeianus, as well as the surface specialization of the nuptial pads (achieved by scanning electron microscopy) in the light of their potential role in the chemical communication in this invasive species.

Analysis of the common spadefoot toad (PELOBATES FUSCUS) skin secretions on the presence of the potential hemostasis system effectors

Since nowadays the chemical synthesis of new bioactive compounds is a complicated and expensive procedure, alongside with the increased price for drugs based on synthetic biologically active compounds, scientists lay emphasize on natural sources as a promising raw material for various biologically active substances. Amphibian skin glands secretions are a powerful source of potential pharmacological agents. Currently their antimicrobial, antiviral, cardiotonic and antidiabetic activities have been studied in detail, although almost nothing is known about the effects of the tailless amphibians' skin secretions on the functioning of the hemostasis system. The aim of this study was to analyze the potential effects of the components of skin glands secretions of a representative of Ukrainian batrakhofauna – the Common spadefoot toad (Pelobates fuscus) on some parameters of hemostasis system. In the result of chromatographic separation of general skin secretions, 4 protein fractions were obtained, containing a variety of proteins with molecular masses ranging from 17 to 150 kDa. The components of fraction 1 activated prothrombin and factor X in plasma. Several components of fraction 4 had proteolytic activity and substrate specificity for collagen. The components of fractions 1 and 2 prolonged plasma coagulation time in the APTT. Thus, it was proved the presence of biologically active compounds in the P. fuscus skin secretions, that indicates the prospects for further research to identify the individual components responsible for the manifestation of the shown effects in order to provide clues in understanding the structural and functional characteristics and mechanism of action. Moreover, advances in this area will further increase the use of amphibian skin secretions as a raw material for the development of new original pharmaceutical agents and/or biotechnological products