Biology subjects

Schenkelaars, Q.

Publications and source records attributed to Schenkelaars, Q..

4 recordsLinked to original sources

bioRxiv2024

The Oscarella sponges genus: a hidden yet colorful diversity

The identification and classification of new taxa are crucial for understanding biodiversity. However, assigning samples to new taxa requires cautious and rigorous approaches. Historically, taxonomy has heavily relied on morphological traits, which can be subjective and may not always reflect underlying genetic divergence, particularly in organisms with few diagnostic morphological traits. A prime example is the sponge genus Oscarella (Homoscleromorpha), where species delimitation is challenged by the absence of spicules and limited morphological characters. Here, we address this gap by combining an extensive genetic dataset (192 specimens, five markers) with systematic photographic documentation. This approach enabled a robust assessment of Oscarella diversity in the Western Mediterranean, resulting in the identification of four species new to science. Multigene phylogenetic analyses also enabled us to propose an evolutionary scenario for color polymorphism. Moreover, our data highlighted critical limitations in current methodologies for studying Oscarella, including the low resolution of the widely used cytochrome c oxidase subunit I (cox1/COI) gene, the lack of genetic data for many species, and insufficient information on their geographical distribution. These issues, which mirror challenges across many taxa, highlight the urgent need for standardized genetic frameworks and comprehensive datasets to improve taxonomic resolution for each taxon.

evolutionary biology↗

bioRxiv2022

The compact genome of the sponge Oopsacas minuta (Hexactinellida) is lacking key metazoan core genes

BackgroundBilaterian animals today represent 99% of animal biodiversity. Elucidating how bilaterian hallmarks emerged is a central question of animal evo-devo and evolutionary genomics. Studies of non-bilaterian genomes have suggested that the ancestral animal already possessed a diversified developmental toolkit, including some pathways required for bilaterian body plans. Comparing genomes within the early branching metazoan Porifera phylum is key to identify which changes and innovations contributed to the successful transition towards bilaterians. ResultsHere, we report the first whole genome comprehensive analysis of a glass sponge, Oopsacas minuta, a member of the Hexactinellida. Studying this class of sponge is evolutionary relevant because it differs from the three other Porifera classes in terms of development, tissue organization, ecology and physiology. Although O. minuta does not exhibit drastic body simplifications, its genome is among the smallest animal genomes sequenced so far, surprisingly lacking several metazoan core genes (including Wnt and several key transcription factors). Our study also provided the complete genome of the symbiotic organism dominating the associated microbial community: a new Thaumarchaeota species. ConclusionsThe genome of the glass sponge O. minuta differs from all other available sponge genomes by its compactness and smaller number of predicted proteins. The unexpected losses of numerous genes considered as ancestral and pivotal for metazoan morphogenetic processes most likely reflect the peculiar syncytial organization in this group. Our work further documents the importance of convergence during animal evolution, with multiple emergences of sponge skeleton, electrical signaling and multiciliated cells.

evolutionary biology↗

bioRxiv2020

The polymorphism of Hydra satellite sequences provides strain-specific signatures

Hydra are freshwater polyps widely studied for their amazing regenerative capacity, adult stem cell populations, low senescence and value as ecotoxicological marker. Many wild-type strains of H. vulgaris have been collected worldwide and maintained effectively under laboratory conditions by asexual reproduction, while stable transgenic lines have been continuously produced since 2006. Efforts are now needed to ensure the genetic characterization of all these strains, which despite similar morphologies, show significant variability in their response to gene expression silencing procedures, pharmacological treatments or environmental conditions. Here, we established a rapid and reliable procedure at the single polyp level to produce via PCR amplification of three distinct microsatellite sequences molecular signatures that clearly distinguish between Hydra strains and species. The TG-rich region of an uncharacterized gene (ms-c25145) helps to distinguish between Eurasian H. vulgaris strains (Hm-105, Basel1, Basel2 and reg-16), between Eurasian and North American H. vulgaris strains (H. carnea, AEP), and between the H. vulgaris and H. oligactis species. The AT-rich microsatellite sequences located in the AIP gene (Aryl Hydrocarbon Receptor Interaction Protein, ms-AIP) also differ between Eurasian and North American H. vulgaris strains. Finally, the AT-rich microsatellite located in the Myb-Like cyclin D-binding transcription factor1 gene (ms-DMTF1) gene helps to distinguish certain transgenic AEP lines. This study shows that the analysis of microsatellite sequences provides a barcoding tool that is sensitive and robust for the identification of Hydra strains. It is also capable of identifying cryptic species by tracing microevolutionary events within the genus Hydra.

evolutionary biology↗

bioRxiv2017

Hydra, a model system for deciphering the mechanisms of aging and resistance to aging

The freshwater cnidarian polyp named Hydra, which can be mass-cultured in the laboratory, is characterized by a highly dynamic homeostasis with a continuous self-renewal of its three adult stem cell populations, the epithelial stem cells from the epidermis, the epithelial stem cells from the gastrodermis, and the multipotent interstitial stem cells, which provide cells of the nervous system, gland cells and germ cells. Two unusual features characterize these stem cells that cannot replace each other, they all avoid G1 to pause in G2, and the two epithelial populations are concomitantly multifunctional and stem cells. H. vulgaris that does not show any signs of aging over the years, resists to weeks of starvation and adapts to the loss of neurogenesis, providing a unique model system to study the resistance to aging. By contrast some strains of a distinct species named H. oligactis undergo a rapid aging process when undergoing gametogenesis or when placed in stress conditions. The aging phenotype is characterized by the rapid loss of somatic interstitial stem cells, the progressive reduction in epithelial stem cell self-renewal, the loss of regeneration, the disorganization of the neuro-muscular system, the loss of the feeding behavior, and the death of all animals within about three months. We review here the possible mechanisms that help H. vulgaris to sustain stem cell self-renewal and thus bypass aging processes. For this, FoxO seems to act as a pleiotropic actor, regulating stem cell proliferation, stress response and apoptosis. In H. oligactis, the regulation of the autophagy flux differs between aging-sensitive and aging-resistant animals, pointing to a key role for proteostasis in the maintenance of a large pool of active and plastic epithelial stem cells.

evolutionary biology↗