| Recent
projects Comparative evo-devo studies of vertebrate attachment glands: Ontogeny, evolution & homology of cement gland and attachment organs in lower vertebrates - PhD project supervised by Robert Cerny - supported by the STARS programme of the Faculty of Science, Charles University in Prague - ended in 2017 Abstract Cement glands or so called attachment organs are larval cranial structures found in most vertebrates with water-dwelling larval stages. These structures secrete mucus that helps larvae to attach to substrate or simply to stay at their hatching place before their locomotory organs are fully developed and before they can feed. Morphology, topographic location on the head, number of these glands/organs, but also their embryonic origin significantly differ among vertebrate lineages; their homology or more exactly the level of their homology might therefore be questioned. The key problem is represented by mostly unknown fact that in basal Actinopterygians like Polypterus (bichir) or Amia (bowfin) (so called "ancient fishes") these structures seem to be embryonically derived from the pharyngeal endoderm whereas similar structures of other vertebrates are of superficial (ectodemal) origin. Moreover, in Xenopus these structures are commonly considered as a paradigm for anteriormost head patterning with Otx2 gene expression. The goal of this project is to identify developmental-genetic mechanisms that drive morphogenesis of these structures in several evolutionary key vertebrate lineages. By using descriptive and experimental methods of comparative embryology we seek to study these structures in sturgeons, bichirs and amphibians in order to identify plesiomorphic and apomorphic features of developmental-genetic modules of these organs and thus to reveal key developmental changes responsible for phenotypic variability of these fundamental adaptive larval organs of vertebrates. Deciphering the evolution of cement organs in ray-finned fishes - supported by GAUK grant no. 220213 - ended in 2015 Abstract Cement glands, one of the key vertebrate larval adaptations, often are the first structures to develop on the embryonic head. In vertebrates they allow the larvae to attach to the substrate. Although temporarily restricted, they can have striking influence on craniofacial development. Various types of cement glands have been described in actinopterygians, dipnoans and amphibians, similarly to ascidians and lancelets. Although there are many studies on their function and morphology, the question of their homology remains unsolved. While cement glands share many cytological characteristics of secretory cells, they seem to differ considerably in arrangement or embryonic origin. Nevertheless, cement glands have recently been defined as a result of shared capacity of larval head ectoderm to express adhesive cells. However, among actinopterygians these organs can rise from different germ layers and in dissimilar embryonic contexts (Minarik et al., in prep.). To assess their homology it is therefore essential to understand their evolution among actinopterygians first. This project aims to provide a detailed embryological, developmental and proteomic characteristic of cement organs in key members of Actinopterygii in order to understand their developmental formation and evolution. This step might help to elucidate evolution of these adaptive structures of vertebrates in general. Evolution of vertebrate foregut formation: Contribution of pharyngeal morphogenesis into embryonic and larval adaptive structures of basal fishes: Micro-CT analyses of developmental processes and gene expression patterns - supported by Aktion Österreich-Tschechien scholarship - autumn semester 2014/2015 Abstract (shortened) Our previous data on bichir (Minarik et al., in prep.) have demonstrated surprising endoderm germ-layer origin of larval cement organs, a transient mucus-secreting structures situated on head surface of many vertebrate larvae which enable a firm adhesion before mouth, fins or limbs well develop. Whereas in other lineages these organs derive paradigmatically from outer ectoderm via epidermal thickening, in bichirs we have revealed a strikingly dissimilar morphogenesis via foregut-derived pouches, which only later fuse with adjacent epidermis. Similar developmental formation has also been suggested for bowfins and gars, according to some histology-based reports from the beginning of 20th century. Such situation contradicts the general notion of pharyngeal endoderm as a conservative germ layer with little or no adaptive potential outside the foregut context. This study aims to perform comparative analysis of developmental formation and morphogenesis of pharyngeal endoderm throughout embryogenesis to identify its contribution to novel adaptive traits. Concurrently, expression patterns of candidate genes involved in these processes will be evaluated in key fish lineages (bichirs, sturgeons, bowfins, gars, teleosts). MSc & BSc Projects: Developmental morphogenesis of attachment organs in lower vertebrates - MSc Thesis supervised by Robert Cerny - BSc Thesis supervised by Robert Cerny |
© Martin Minařík 2018; Last Update II/2024