Protocol for a systematic evidence map of sex hormone biosynthesis in Mollusca

The continuing debate around the presence of vertebrate-type steroids in molluscs as well as their possible involvement in invertebrate reproduction and development reflects the gap of knowledge that exists within molluscan endocrinology. Although previous attempts in addressing the occurrence of vertebrate-type steroids in molluscs as well as the expression of steroidogenic genes in molluscan tissues are informative, doubts remain as to whether these steroids possess a functional role. Missing is a systematic evidence map on the presence of sterols and steroid hormones (vertebrate-type and invertebrate-type) in Mollusca as well as on the expression of steroidogenesis-related genes (including transport proteins and enzymes involved in the production and breakdown of retinoids) in these species. Furthermore, a systematic search of the literature on the expression of nuclear hormone receptors and nuclear retinoid receptors will also be conducted in the hopes of developing a better understanding on the function of NRs and their role in molluscan sex hormone biosynthesis. This systematic evidence map aims to: (1) provide a comprehensive assessment of our current understanding of sex hormone biosynthesis in molluscs, through an appropriate evaluation of all available evidence that exists in the literature and (2) highlight gaps in our knowledge for future research.

This draft protocol is now being published on the open repository Zenodo as part of an 'open peer review' process. The wider scientific community is invited to comment on the systematic mapping methodology aiming to collect and assess literature that addresses the occurrence of different sex hormones in molluscs as well as the expression of nuclear hormone receptors and steroidogenesis related genes in molluscan tissues. 

Please send your comments and feedback using this form until Wednesday 28/07/2021 23:00 (CET).