Molecular and morphological diversity of monothalamous foraminifera from South Georgia and the Falkland Islands: Description of four new species

Morphology and molecular phylogeny of two new species of Psammophaga (Rhizaria, Foraminifera) from the west coast of India

Benthic foraminifera are unicellular eukaryotic protists that construct an organic, agglutinated, or calcareous test wall. Although single-chambered (monothalamous) foraminifera are ubiquitous in marine habitats worldwide, they are poorly known compared to their multi-chambered relatives, notably from the tropical marine environments of India. In this study, we describe two new species of marine monothalamid genus Psammophaga Arnold, 1982, from the Rajapuri Creek, coastal Maharashtra, India (Arabian Sea). Psammophaga holzmannae sp. nov. is ovoid to spherical shaped, 103-246 µm in length, single aperture, translucent to orange color cytoplasm, outer surface is composed of agglutinated fine clay particles, and ingested mineral grains are concentrated near its aperture. Psammophaga sinhai sp. nov. is oblong, elliptical, or droplet-shaped, 279-448 µm in length, single aperture, yellow olive color cytoplasm, the exterior surface formed of agglutinated fine clay particles, and the ingested mineral grains are dispersed throughout the body. Phylogenetic analyses based on partial small subunit rRNA gene sequences position new species within the Clade E of monothalamids and are genetically distinct from other Psammophaga. Elemental (SEM-EDS) analysis of engulfed mineral grains revealed preferential selection and uptake of heavy opaque titaniferous minerals from the ambient environment in the cytoplasm.

Unlocking foraminiferal genetic diversity on estuarine mudflats with eDNA metabarcoding

Environmental biomonitoring is a prerequisite for efficient evaluation and remediation of ecosystem degradation due to anthropogenic pressure or climate change. Estuaries are key habitats subject to multiple anthropogenic and natural stressors. Due to these multiple stressors, the detection of anthropogenic pressure is challenging. The fact that abundant natural stressors often lead to negative quality assessments has been coined the "estuarine quality paradox". To solve this issue, the application of molecular approaches with successful bioindicators like foraminifera is promising. However, sampling protocols, molecular procedures and data analyses need to be validated before such tools can be routinely applied. We conducted an environmental DNA survey of estuarine mudflats along the French Atlantic coast, using a metabarcoding approach targeting foraminifera. Our results demonstrate that estuarine environments have only a few active OTUs dominating the community composition and a large stock of dormant or propagule stages. This last genetic diversity components constitute an important reservoir, with different species which can potentially develop in response to the temporal variability of the multiple stressors. In fact, different OTUs were dominant in the studied estuaries. Our statistical model shows that the physical and chemical characteristics of the sediment and the climatic conditions explain only 43 % of the community composition variance. This suggests that other, less easily quantifiable factors, such as the history and use of the estuaries or the ecological drift could play an important role as well. Environmental DNA biomonitoring opens new perspectives to better characterize the genetic diversity in estuaries.

Novel contributions to the molecular and morphological diversity of freshwater monothalamid foraminifera: Description of six new species

Non-marine monothalamous foraminifera are common in freshwater and soil habitats. They comprise a poorly-known group lacking sufficient information about diversity, morphology, reproduction, distribution and ecology. Based on an integrative morphological and molecular approach we describe a new family, a new genus and six new species of freshwater monothalamids from different localities in the Netherlands and France. We establish Astroperula as a new genus of organic walled freshwater foraminifera that contains two species, Astroperula dumacki and Astroperula parvipila. Furthermore, two new agglutinated freshwater monothalamids are described and illustrated, Limnogromia leanneae and Lacogromia pawlowskii, one new organic walled, Velamentofex dujardini, and a new naked monothalamid, Haplomyxa retiforma. Additional information is provided about a special form of cell division in Claparedellus lachmannii and L. leanneae, and feeding behavior in cultures of V. dujardini. Morphological observations are added for an unidentified Limnogromia sampled from the Netherlands and two types of Lacogromia sampled from an alpine region in the French Pyrenees and a karst sinkhole in Bosnia and Herzegovina. The present study provides additional insight into the ecology, diversity and occurrence of freshwater monothalamids and emphasizes the fact that a combination of morphological and molecular methods is necessary to clearly distinguish species in this group.

Shallow-marine testate amoebae with internal structures from the Lower Devonian of China

Testate amoebae, a polyphyletic protist group inhabiting a wide variety of extant ecosystems, have evolved as far back as early Neoproterozoic. However, their fossil record is discontinuous and biased toward empty shells. Here, we report an arcellinid testate amoeba species, Cangwuella ampulliformis gen. nov., sp. nov., from a shallow-marine community in the Early Devonian of Guangxi, southwestern China. With the aid of scanning electron microscopy and X-ray micro-tomography, we find that the shell of our testate amoeba contains some acetabuliform structures. Although such configuration does not match exactly with the known internal structures in extant testate amoebae, our fossils highlight the potential of exploring the ecological relationships between fossil testate amoebae and their associated organisms, and increase our knowledge on the diversity of testate amoebae in Early Devonian environments.

Lead and cadmium exposure alters shell morphogenesis in a single-chambered, agglutinated foraminiferan protist

Changes to calcareous foraminiferal shell morphology are well documented in heavy metal-polluted marine environments, however less is known about how these toxicants affect agglutinated foraminifera, particularly single-chambered (monothalamid) species. Here we used an agglutinated monothalamic foraminifer, Astrammina rara, to study shell morphogenesis during exposure to lead (Pb) and cadmium (Cd). Isolated cell bodies incubated with artificial sediment and control, Pb-, or Cd-spiked artificial seawater constructed new agglutinated shells in four weeks. Time-lapse recordings showed normal motile behavior during treatments. SEM imaging of reconstructed shells, however, revealed dramatic deformations in the bioadhesive of Pb-exposed shells, and less so in Cd-exposed shells. ICP-MS analysis of the isolated shells showed elevated levels of Pb, but not Cd, in the bioadhesive of treated specimens, indicating that the two metals exert their effects differentially. These findings show that certain agglutinated foraminifera may be useful indicator species in studies of heavy metal-polluted benthic marine environments.