The role of mucus in particle processing by suspension-feeding marine bivalves: unifying principles

1997 ◽  
Vol 129 (2) ◽  
pp. 389-397 ◽  
Author(s):  
P. G. Beninger ◽  
S. D. St-Jean
Author(s):  
Peter G. Beninger ◽  
Marcel Le Pennec

Histochemical techniques were used to investigate the possible role of the buccooesophageal glands in the blue mussel, Mytilus edulis L. (Mollusca: Bivalvia). No activity was observed for any of the eight major digestive enzymes tested; however, the glands contained large amounts of both neutral and acid mucopolysaccharides. These results confirm the importance of mucus in the ingestive process in M. edulis, and do not support the hypothesis of ingestion of particles suspended in water alone.Until recently it was thought that the Bivalvia were the only class of molluscs in which some type of secretory gland of extracellular digestive function in the bucco-oesophageal region was totally absent (Table 1). However, in a study of the mode of particle ingestion in five species of suspension-feeding bivalves, an extensive glandular complex was reported in the bucco-oesophageal region of Mytilus edulis L. only (Beninger et al., 1991). Although these glands were observed to liberate secretions into the oesophageal lumen, it was not known whether they performed any digestive function.


2020 ◽  
Vol 6 (49) ◽  
pp. eabc6721
Author(s):  
John R. Paterson ◽  
Gregory D. Edgecombe ◽  
Diego C. García-Bellido

Radiodonts are nektonic stem-group euarthropods that played various trophic roles in Paleozoic marine ecosystems, but information on their vision is limited. Optical details exist only in one species from the Cambrian Emu Bay Shale of Australia, here assigned to Anomalocaris aff. canadensis. We identify another type of radiodont compound eye from this deposit, belonging to ‘Anomalocaris’ briggsi. This ≤4-cm sessile eye has >13,000 lenses and a dorsally oriented acute zone. In both taxa, lenses were added marginally and increased in size and number throughout development, as in many crown-group euarthropods. Both species’ eyes conform to their inferred lifestyles: The macrophagous predator A. aff. canadensis has acute stalked eyes (>24,000 lenses each) adapted for hunting in well-lit waters, whereas the suspension-feeding ‘A.’ briggsi could detect plankton in dim down-welling light. Radiodont eyes further demonstrate the group’s anatomical and ecological diversity and reinforce the crucial role of vision in early animal ecosystems.


Development ◽  
2020 ◽  
Vol 147 (14) ◽  
pp. dev183079 ◽  
Author(s):  
Berenika Płusa ◽  
Anna Piliszek

ABSTRACTPre-implantation mammalian development unites extreme plasticity with a robust outcome: the formation of a blastocyst, an organised multi-layered structure ready for implantation. The process of blastocyst formation is one of the best-known examples of self-organisation. The first three cell lineages in mammalian development specify and arrange themselves during the morphogenic process based on cell-cell interactions. Despite decades of research, the unifying principles driving early mammalian development are still not fully defined. Here, we discuss the role of physical forces, and molecular and cellular mechanisms, in driving self-organisation and lineage formation that are shared between eutherian mammals.


2021 ◽  
Vol 15 (2) ◽  
pp. 153
Author(s):  
Marcello Guimarães Simões ◽  
Antonio Carlos Marques ◽  
Luiz Henrique Cruz de Mello ◽  
Renato Pirani Ghilardi

The Megadesmidae (Bivalvia, Anomalodesmata) fossil record was examined in order to assess the role of taphonomy in cladistic analysis. Megadesmids are thick-shelled, infaunal, suspension-feeding bivalves. Our data indicate that their fossil record seems biased in favor of thick-shelled, shallow-burrowing genera and/or deep­burrowing forms. Consequently, there is a relation between the mode of life (shallow versus deep) and the resolution and quality of the fossil record. Deep-burrowers (Vacunella) are often preserved in life position offering a more accurate (temporal and spatial) fossil record, adequate for paleoecological inferences, while shallow-burrower shells (Plesiocyprinella), that are more prone to post-mortem transport and temporal mixing, offer a record with poor spatial and temporal resolution. The identification of homoplasy among infauna! bivalves constitutes a major challenge for their cladistic analysis. Within Megadesmidae intrinsic (bauplan limitations) and extrinsic (better preservational potential) factors favor the occurrence and preservation of homoplasy among the deep-burrowers. The implications are: a) clustering of deep-burrowing bivalves (Vacunella, Roxoa) due to parallel homoplasies, forming "adaptive", not necessarily "evolutive" taxa, and b) lower consistency indices in their cladistic analysis. 


2021 ◽  
Vol 15 (02) ◽  
pp. 135-150
Author(s):  
Manfred Euler

This review presents a sequence of exemplary experience-based encounters with self-organizing systems on different levels of difficulty. Based on hands-on experiments and creative modeling it provides a viable educational road to build up a deeper understanding of self-organization principles and their comprehensive nature. Theories of self-organization describe how patterns, structures and new types of behavior emerge in energetically open systems, resulting from the local interaction of many components. As an external control instance is missing, the underlying philosophy is counterintuitive to our habits of causal thinking. This thematic and conceptual framework impacts on many STEM domains and presents a blueprint for modeling emergent structures and complex functions in natural and technological systems. It reveals unifying principles that can help in reducing, in structuring and, finally, in understanding and controlling the emerging complexity. An overview across diverse STEM domains highlights the role of this overarching concept. This cross-disciplinary approach can help in improving the dialogue and the knowledge exchange between the individual fields. Moreover, in a self-referential fashion, the modeling of self-organization provides us with fresh perspectives to reflect our own creative processes.


2021 ◽  
pp. 105908
Author(s):  
Taiki Okabe ◽  
Rion Saito ◽  
Kohei Yamamoto ◽  
Riku Watanabe ◽  
Yoshiki Kaneko ◽  
...  
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