Jeroen Admiraal

Evolutionary origin and development of snake fangs

Many advanced snakes use fangs—specialized teeth associated with a venom gland—to introduce venom into prey or attacker. Various front- and rear-fanged groups are recognized, according to whether their fangs are positioned anterior (for example cobras and vipers) or posterior (for example grass snakes) in the upper jaw. A fundamental controversy in snake evolution is whether or not front and rear fangs share the same evolutionary and developmental origin. Resolving this controversy could identify a major evolutionary transition underlying the massive radiation of advanced snakes, and the associated developmental events. Here we examine this issue by visualizing the tooth-forming epithelium in the upper jaw of 96 snake embryos, covering eight species. We use the sonic hedgehog gene as a marker, and three-dimensionally reconstruct the development in 41 of the embryos. We show that front fangs develop from the posterior end of the upper jaw, and are strikingly similar in morphogenesis to rear fangs. This is consistent with their being homologous. In front-fanged snakes, the anterior part of the upper jaw lacks sonic hedgehog expression, and ontogenetic allometry displaces the fang from its posterior developmental origin to its adult front position—consistent with an ancestral posterior position of the front fang. In rear-fanged snakes, the fangs develop from an independent posterior dental lamina and retain their posterior position. In light of our findings, we put forward a new model for the evolution of snake fangs: a posterior subregion of the tooth-forming epithelium became developmentally uncoupled from the remaining dentition, which allowed the posterior teeth to evolve independently and in close association with the venom gland, becoming highly modified in different lineages. This developmental event could have facilitated the massive radiation of advanced snakes in the Cenozoic era, resulting in the spectacular diversity of snakes seen today.

Molecular evolution of the MAGUK family in metazoan genomes

BackgroundDevelopment, differentiation and physiology of metazoans all depend on cell to cell communication and subsequent intracellular signal transduction. Often, these processes are orchestrated via sites of specialized cell-cell contact and involve receptors, adhesion molecules and scaffolding proteins. Several of these scaffolding proteins important for synaptic and cellular junctions belong to the large family of membrane-associated guanylate kinases (MAGUK). In order to elucidate the origin and the evolutionary history of the MAGUKs we investigated full-length cDNA, EST and genomic sequences of species in major phyla.ResultsOur results indicate that at least four of the seven MAGUK subfamilies were present in early metazoan lineages, such as Porifera. We employed domain sequence and structure based methods to infer a model for the evolutionary history of the MAGUKs. Notably, the phylogenetic trees for the guanylate kinase (GK)-, the PDZ- and the SH3-domains all suggested a matching evolutionary model which was further supported by molecular modeling of the 3D structures of different GK domains. We found no MAGUK in plants, fungi or other unicellular organisms, which suggests that the MAGUK core structure originated early in metazoan history.ConclusionIn summary, we have characterized here the molecular and structural evolution of the large MAGUK family. Using the MAGUKs as an example, our results show that it is possible to derive a highly supported evolutionary model for important multidomain families by analyzing encoded protein domains. It further suggests that larger superfamilies encoded in the different genomes can be analyzed in a similar manner.

Developmental anatomy of lampreys

Lampreys are a group of aquatic chordates whose relationships to hagfishes and jawed vertebrates are still debated. Lamprey embryology is of interest to evolutionary biologists because it may shed light on vertebrate origins. For this and other reasons, lamprey embryology has been extensively researched by biologists from a range of disciplines. However, many of the key studies of lamprey comparative embryology are relatively inaccessible to the modern scientist. Therefore, in view of the current resurgence of interest in lamprey evolution and development, we present here a review of lamprey developmental anatomy. We identify several features of early organogenesis, including the origin of the nephric duct, that need to be re‐examined with modern techniques. The homologies of several structures are also unclear, including the intriguing subendothelial pads in the heart. We hope that this review will form the basis for future studies into the phylogenetic embryology of this interesting group of animals.

The missing pillar: Eudemonic values in the justification of nature conservation

The public justification for nature conservation currently rests on two pillars: hedonic (instrumental) values, and moral values. Yet, these representations appear to do little motivational work in practice; biodiversity continues to decline, and biodiversity policies face a wide implementation gap. In seven EU countries, we studied why people act for nature beyond professional obligations. We explore the motivations of 105 committed actors for nature in detail using life-history interviews, and trace these back to their childhood. Results show that the key concept for understanding committed action for nature is meaningfulness. People act for nature because nature is meaningful to them, connected to a life that makes sense and a difference in the world. These eudemonic values (expressing the meaningful life) constitute a crucial third pillar in the justification of nature conservation. Important policy implications are explored, e.g. with respect to public discourse and the encounter with nature in childhood.

Motivations for committed nature conservation action in Europe

Despite ongoing efforts to motivate politicians and publics in Europe regarding nature conservation, biodiversity continues to decline. Monetary valuation of ecosystem services appears to be insufficient to motivate people, suggesting that non-monetary values have a crucial role to play. There is insufficient information about the motivations of actors who have been instrumental in successful conservation projects. We investigated the motivations underlying these biodiversity actors using the ranking of cards and compared the results with the rankings of motivations of a second group of actors with more socially related interests. For both groups of actors, their action relating to biodiversity was supported in general by two groups of motivations related to living a meaningful life and moral values. The non-biodiversity actors also noted that their action relating to biodiversity rested more on beauty, place attachment and intrinsic values in comparison with their main non-biodiversity interests. Our results have implications for environmental policy and biodiversity conservation in that the current tendency of focusing on the economic valuation of biodiversity fails to address the motivations of successful actors, thereby failing to motivate nature conservation on an individual level.

What makes you a 'hero' for nature? Socio-psychological profiling of leaders committed to nature and biodiversity protection across seven EU countries

Biodiversity loss is a widely debated world problem, with huge economic, social, and environmentally negative consequences. Despite the relevance of this issue, the psychological determinants of committed action towards nature and biodiversity have rarely been investigated. This study aims at identifying a comprehensive social-psychological profile of activists committed to biodiversity protection and at understanding what determinants best predict their activism. A questionnaire investigating relevant social-psychological constructs identified in the literature on environmental activism was administered to 183 outstanding leaders (vs. non-leaders) in biodiversity protection across seven EU countries. Leaders (vs. non-leaders) in biodiversity protection showed, among other constructs, higher scores on environmental values, attitudes, identity, perceived control, a feeling of union and spirituality with nature, and willingness to sacrifice for their cause. Results are discussed within the theoretical framework of a motivation model of committed action for nature and biodiversity protection. Applications of the results are also proposed.