Project description:The four-eyed fish Anableps anableps exhibits a unique visual system adapted for simultaneous aerial and aquatic vision, making it an exceptional model for investigating evolutionary innovations in vertebrate eye development. This dual vision capability is supported by specialized adaptations to the eye, including a thicker dorsal (aerial) cornea and asymmetric expression of visual opsins: opn1mw1 in the ventral retina, and opn1lw1 in the dorsal retina. To investigate the molecular and spatial basis of this asymmetry, we used single-nucleus RNA sequencing (snRNAseq) of the retina in combination with spatial transcriptomics of the whole eye. Our findings reveal that the asymmetric opsin distribution results from a developmental expansion of the ventral retina, which is adapted for detecting aerial light, alongside a reduction in the dorsal retinal domain responsible for aquatic vision. These results highlight a novel mechanism of regional specialization in the vertebrate retina and provide insights into the evolutionary innovations in the vertebrate visual system.
Project description:Testing for toxicity in a number of aquatic organisms is necessary for risk assessments of substances. Yet, aquatic larvae of the so-called EPT (Ephemeroptera, Plecoptera, Trichoptera) taxa are regularly exposed to several environmental contaminants and have been demonstrated to be extremely vulnerable to a variety of environmental pollutants. These results show that existing toxicity testing can result in an underestimating of the risk for EPT taxa and that more toxicity data using EPT taxonomic representatives are needed. Unfortunately, there is a dearth of standardized test techniques and scant published data, particularly for European EPT species. Our study's objective was to create a testing framework for a variety of endpoints in the mayfly Cloeon dipterum. Due to its high prevalence in local waterbodies and its brief lifecycle of a few weeks in the right environmental conditions, C. dipterum was selected as the test organism. To this end, two chronic toxicity tests with semi-static test design and two media renewal per week were performed. Small larvae in the stage L3 based on the wing pad development described by Cianciara (1976) were used in the tests. Four replicates per test concentration and control containing five individuals per replicate were installed. The emergence was determined daily on working days. The tests were conducted at a temperature of 20 °C (± 1 °C) and the illumination was < 1 µE m2s 1 with a light and dark rhythm of 16:8 h. The physico-chemical parameters pH, oxygen concentration, and oxygen saturation were measured using the multiparameter device WTW Multi 1970i at test start, throughout each media renewal, and at test end. Continuous temperature measurements were taken, and weekly lighting assessments were made. Fipronil was administered to C. dipterum larvae in the long-term exposure experiment at nominal concentrations ranging from 0.038 to 0.60 g/L. This test was conducted for 38 days until all larvae had emerged. In the short-term exposure experiment, C. dipterum larvae were exposed to Fipronil in nominal concentrations between 0.038 and 0.30 µg/L for a test duration of seven days. At test end, the larvae were sampled for transcriptome analysis.
Project description:Understanding how novel complex traits originate is a foundational challenge in evolutionary biology. Yet how descent with modification in developmental evolution may lead to morphological innovation remains poorly understood. We investigated the origin of thoracic horns in scarabaeine beetles, one of the most dramatic classes of secondary sexual traits in the animal kingdom. We show that thoracic horns derive from bilateral source tissues, that diverse wing genes are functionally required for instructing this process, and that in the absence of Hox-input thoracic horn primordia transform to contribute to ectopic wings. Once induced, however, the transcriptional profile of thoracic horns diverges markedly from that of wings and other wing serial homologs. Our results provide evidence for the serial homology between thoracic horns and insects wings, and suggest that other insect innovations may similarly derive from wing serial homologs and the concomitant recruitment of diverse genes from outside a wing formation context.