title: Sex steroid receptor evolution and signalling in aquatic invertebrates.
abstract: In vertebrate reproductive endocrinology sex steroids play a pivotal role via binding to receptors. However, information on the origin and relevance of sex steroids in invertebrates is limited. This review highlights current literature on steroid receptors in aquatic invertebrates and reports on some new findings. It has been shown that invertebrates of the deuterostome clade, such as Acrania and Echinodermata, respond to estrogens and androgens and, at least in Branchiostoma, an estrogen receptor has been cloned. Within the protostomes, most findings are related to aquatic molluscs. Sex steroid receptor-like proteins are abundant in gastropods, bivalves and cephalopods and also sex hormone signalling shows partial similarity to the deuterostomes. In ecdysozoans, however, the impact of sex steroids is still a matter of debate even though there is evidence on the presence of estrogen receptor-like proteins in Crustacea and on physiological effects of estrogens in both Nematoda and Crustacea. Recent findings suggest the presence of an estrogen receptor alpha-like protein of unclear physiological role in Gammarus fossarum (Crustacea). Binding studies revealed the crustacean Hyalella azteca to possess specific binding sites only for androgens but not for estrogens suggesting a possible limitation to functional androgen receptors in this species. Further studies have to be conducted to shed more light into the discussion about the controversy about sex steroid receptors in invertebrates.
authors.affiliation: Animal Physiological Ecology, University of Tübingen, Konrad-Adenauer-Strasse 20, D-72072 Tuebingen, Germany. heinz-r.koehler@uni-tuebingen.de
authors.forename: Heinz-R
authors.initials: HR
authors.lastname: Köhler
authors.forename: Werner
authors.initials: W
authors.lastname: Kloas
authors.forename: Martin
authors.initials: M
authors.lastname: Schirling
authors.forename: Ilka
authors.initials: I
authors.lastname: Lutz
authors.forename: Anna L
authors.initials: AL
authors.lastname: Reye
authors.forename: Jan-S
authors.initials: JS
authors.lastname: Langen
authors.forename: Rita
authors.initials: R
authors.lastname: Triebskorn
authors.forename: Roland
authors.initials: R
authors.lastname: Nagel
authors.forename: Gilbert
authors.initials: G
authors.lastname: Schönfelder
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D012739:Gonadal Steroid Hormones / Q000378:metabolism; D007448:Invertebrates / Q000502:physiology*; D008969:Molecular Sequence Data; D010802:Phylogeny; D011987:Receptors, Steroid / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D015398:Signal Transduction
chemical_list: D012739:Gonadal Steroid Hormones; D011987:Receptors, Steroid