Chemical Warfare in the Environment—Secondary Metabolites From Starfish (<i>Asterias amurensis</i>) Induce Teratogenicity in Medaka Embryos (<i>Oryzias melastigma</i>)

Starfish saponins, known for their role as feeding deterrents against predators like crabs and fish, have been extensively studied for their antifeedant and cytolytic effects. Recent research suggests that starfish secondary metabolites possess antifouling and antifeedant properties and play a role in biological interactions and various ecological functions. Previous research demonstrated that saponins from starfish exert their toxic effects on fish by interacting with cholesterol in the blood cell membrane. This study investigated the hypothesis that secondary metabolites, other than saponins, from the starfish Asterias amurensis may be harmful to fish eggs, particularly marine medaka (Oryzias melastigma) eggs, which share starfish habitat. We systematically separated the secondary metabolites of A. amurensis by a variety of chromatographic methods. Two oligoglycosides related to embryonic teratogenicity were identified, including one previously undescribed tetrasaccharide (1) and one known pyrrole oligoglycoside (2). Their structures were established mainly on the basis of detailed analysis of the nuclear magnetic resonance spectroscopy (NMR) and mass spectroscopic data. Compounds 1 and 2 exhibited strong lethality and significantly reduced voluntary movements in medaka embryos, with compound 2 showing more pronounced effects on teratogenicity and heart rates. The main morphological abnormalities observed included delayed head development (DHD), tiny spines (TS), incomplete absorption of oil balls (OB), cardiac abnormalities (CA), and shrunken yolk sacs (SYS). Our findings imply that starfish secondary metabolites may have broader ecological effects, influencing habitat-sharing species in subtle but crucial ways.