TDK conference 2025

Arthropod molting hormones, the so-called ecdysteroids are the only steroids produced by arthropods, with indispensable effects in their development, diapause, sexual maturation, reproduction and behavior. Plants also biosynthesize similar compounds, the phytoecdysteroids. In addition, ecdysteroids were experimentally shown to have anabolic effects in higher vertebrates, enhancing the metabolic utility of energy supplies, as well as promoting protein synthesis and tissue growth. Naturally, song birds (Aves: Passeriformes) and bats (Mammalia: Chiroptera) were found to have low to high concentrations of these biologically active molecules in their blood. However, besides these high vertebrate orders, members of which constantly feed on insects, it is unknown if other vertebrates would also naturally have ecdysteroids in their circulation. The aim of this work was to clarify this, by analyzing blood samples of wild animals with ultra-high performance liquid chromatography and high-resolution quadrupole-orbitrap mass spectrometry. In this context, such wild animal species were chosen as sample sources which either opportunistically ingest arthropods or are often fed artificially by insect-containing diet in zoological gardens. Thus, blood samples were taken in three zoological gardens, the Hannover Zoo, the Budapest Zoo, and the Sóstó (Nyíregyháza) Zoo from the following reptilian and mammalian species: Chinese water dragons (n=3), eastern hedgehogs (n=8), desert foxes (n=5), striped skunks (n=4), meerkats (n=8) and mandrills (2). These represented one reptilian and three mammalian orders (Squamata and Eulipotyphla, Carnivora, Primates, respectively). Road-killed mammalian carnivores were also sampled in Hungary post mortem, including six wild cats, four beech martens and five Eurasian otters. Finally, blood samples were also drawn and analyzed from nine species of water-associated or predatory birds (n=91) caught for ringing purposes and representing six orders (other than Passerifomes). Ecdysteroids were detected in only two (one avian and one mammalian) species. The blood of a Common Kestrel (Falco tinnunculus) contained 58.9 pmol/mL 20-hydroxyecdysone (CV: 1.2%). In addition, 40.9 pmol/mL (CV: 1.4%) of dacryhainansterone (a phytoecdysteroid) was detected in the blood sample of a beech marten. These results show for the first time that ecdysteroids may also be present in the blood of predominantly carnivorous species of birds and mammals. However, unlike in passerine birds and bats which continuously feed on insect, detectable levels of these anabolic substances appear only occasionally in the blood of opportunistic insectivores. This is probably related to the quick clearance of ecdysteroids in vertebrates. This also implies that ecdysteroids, apart from song birds and bats, probably do not have significant anabolic effect in artificially and occasionally insect-fed zoo animals.