Present-day marine biotas are increasingly subject to anthropogenically-forced extinctions. The study of the global mass extinction event at the Cretaceous-Paleogene (K-Pg) boundary can aid in our understanding of the patterns of selective extinction and survival and the dynamics of ecosystem recovery. Outcrops in the Maastrichtian type region (The Netherlands, Belgium) comprise an expanded K-Pg boundary succession, presenting a unique opportunity to study marine ecosystem recovery within the first thousands of years following the Chicxulub impact. We have reevaluated and studied the palynological, micro- and macropalaeontological record of this unique succession. Ecosystem changes across the K-Pg boundary in this region are rather limited, showing a general shift from epibenthic filter feeders to shallow-endobenthic deposit feeders. The fauna of the lowermost Paleocene still has many ‘Maastrichtian’ characteristics, a biological assemblage that survived the first hundreds to thousands of years into the earliest Paleocene. The shallow-marine oligotrophic carbonate sea of the Maastrichtian type area as inhabited by starvation-resistant, low nutrient-adapted taxa, that were seemingly less affected by the shortlived detrimental conditions of the K-Pg boundary catastrophe, such as darkness, cooling, food-starvation, ocean acidification, resulting in relatively high survival rates. The high survival rate allowed for a fast recolonization and rapid recovery of marine faunas in the Maastrichtian type area.
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RBINS Staff Publications 2019
Due to the availibility of high-quality lacustrine sediment records, the Moervaart depression in northwestern Belgium is a very suitable region from which to assess environmental responses to abrupt climate change during the late-glacial (ca. 14,5 – 11,5 ka cal BP). Multiple-proxy analyses of physical parameters (bulk sediment composition and magnetic susceptibility) and biotic remains (palynomorphs, plant macroremains, diatoms, freshwater molluscs, ostracods and chironomids) resulted in a considerable amount of valuable data concerning the climate and palaeoenvironment in this region. The climatic cycles observed in the late-glacial significantly affected the local vegetation and water shed. The milder Bølling interstadial (ca. 14,5-14,1 ka cal BP), characterized by shallow swamps and an open vegetation of mainly birch, grasses, willow and juniper, was abruptly interrupted by a short cold phase, the Older Dryas (ca. 14,1-13,8 ka cal BP), in which a dry and open grass tundra occurred. Based on the presence of Gloeotrichia colonies, known as nitrogen fixers, it is suggested that during the Older Dryas these cyanobacteria created more favourable conditions for aquatic plants to colonize the swampy areas. During the successive Allerød interstadial (ca. 13,8-12,6 ka cal BP), a shallow, large palaeolake with submerged vegetation (e.g., Nymphaea and Myriophyllum) developed, whereas a more dense birch forest (1st phase), accompanied by pine (2nd phase), was continuously present in the surroundings. Extreme cold climatic conditions during the Younger Dryas (ca. 12,6-11,5 ka cal BP), however, caused major hydrological changes, originating in the development of an east-west trending palaeochannel system across the (nearly-)desiccated lake area. In summary, our results clearly demonstrate strong and rapid environmental responses to abrupt climate change at the last glacial-interglacial transition in the Moervaart area.
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Stress responses are key for parasite survival and, thus, also the evolutionary success of these organisms. However, a strong bias in parasite genomic research towards few human pathogens results in a lack of knowledge on evolutionary diversification mechanisms. Comparative studies of closely related and functionally similar lineages are the key for understanding factors driving adaptive evolution of stress responses. To address this knowledge gap, we contrasted evolutionary patterns of several antioxidant, heat shock, osmoregulatory, and behaviour-related genes in two fish parasitic flatworm lineages with varying species and ecological diversity, Cichlidogyrus and Kapentagyrus (Monopisthocotyla). We assembled the sequences of 48 genes related to stress responses in 11 species through an in-silico exon bait capture approach, applied phylogenetic reconstruction and tested for signatures of selection. The study also reports the first foraging (For) gene orthologs in flatworms. Additionally, the absence of cytochrome P450 (Cyp) and kappa (Gstk) and sigma-class glutathione S-transferases (Gsts) in monopisthocotylan flatworms is reported, genes typically considered essential for metazoan life. The results reveal copy number differences in heat shock (Hsp) and oxidative stress genes between the two parasite lineages potentially linked to the diversity of ecological niches occupied by their respective host taxa. Positive selection is detected in genes related to mitochondrial protein import (Hsp) and behaviour (For) in species of Cichlidogyrus infecting a host lineage under adaptive radiation (East African cichlids), suggesting an adaptive link to a putative co-radiation of parasites and hosts. Therefore, the study identifies the first potential molecular function linked to a flatworm radiation.
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RBINS Staff Publications 2025
