Dr Maria Holzmann

Non-marine foraminifera remain among the least explored groups within the Rhizaria, despite their ecological and evolutionary significance. We report the rediscovery of the agglutinated monothalamid Limnogromia saxicola (Penard, 1905) and provide the first integrative morphological and molecular characterization of this species since its original description. In addition, we describe four new organic-walled monothalamids based on morphological and molecular data: Claparedellus arenivagus sp. nov., C. dunicola sp. nov., Perseforaminifer crypticus gen. et sp. nov., and Edaphoallogromia bettighoferi sp. nov. Morphological differentiation is challenging due to limited diagnostic characters and intraspecific variability, although nuclear architecture and birefringent cytoplasmic crystals provide useful markers. Limnogromia saxicola and P. crypticus include environmental sequences that are nearly identical to those obtained from individually extracted specimens. This is the first time that environmental sequences can be confidently linked to defined species. Additionally, brief descriptions and illustrations are provided for seven undetermined monothalamous morphotypes for which no sequences could be obtained. Our findings expand the known diversity, ecological range, and cryptic complexity of freshwater monothalamids. This study underscores the importance of integrating morphological, molecular, and ecological data to resolve taxonomy, detect cryptic diversity, and better understand the evolutionary history of non-marine monothalamids.

Henderson (2023) gave informal descriptions of several soft-walled, monothalamid foraminifera from intertidal zones in the Lorne area of northwest Scotland based on morphology. In the present study, we use a combination of morphological and molecular data to formally establish one new genus and five new monothalamid species from the same area. Lorneia sphaerica gen. & sp. nov. (monothalamid Clade D) has a spherical, coarsely agglutinated test containing magnetic particles and minute aperture-like openings distributed around the test. Lorneia ovalis gen. & sp. nov. (Clade D) has similar characteristics, but the test is oval, and there is a terminal aperture situated at each end. Psammophaga owensi sp. nov. (Clade E) has an oval, finely agglutinated test with a simple terminal aperture and intracellular magnetic particles. In Hilla brevis sp. nov. (Clade Y), the test is broadly oval and finely agglutinated with a reflective sheen and a large terminal aperture with a pronounced collar. Flaviatella zaninettiae sp. nov. (Clade Y) has an elongate, finely agglutinated test with a reflective sheen, a tubular terminal apertural structure, and distinctive yellow cytoplasm. Two species, Flexammina islandica Voltski and Pawlowski, 2015 and Ovammina opaca Dahlgren, 1962, are reported for the first time in Scottish coastal waters. This study underlines the importance and diversity of monothalamid foraminifera in coastal settings.

Benthic foraminifera are one of the major groups of eukaryotes living at cold seeps on the Arctic seafloor. However, their distribution and endemicity in these habitats have been largely debated. It is still unclear whether foraminiferal species commonly found in cold seeps differ genetically from those in deep-sea environments, and to what extent the seep community is distinct. To address these questions, we analyzed sediment DNA metabarcoding data specifically targeting foraminifera in different deep-water cold seep microhabitats (microbial mats, siboglinid tubeworms field) and reference sites within and outside the seep. Our results revealed microhabitat specificity among benthic foraminifera species. Microbial mats were dominated by a unique type of rDNA sequences assigned to a new lineage of monothalamid (single-chambered) foraminifera not previously reported from any other Arctic location. Other foraminiferal species were found across both seeps and reference stations. This study shows the presence of an endemic benthic foraminiferal species at cold seeps and confirms the existence of many common opportunistic species.

In this global review we recognise, describe and figure 205 morphospecies of living elphidiids (Cribroelphidiidae, Elphidiellidae, Elphidiidae, Haynesinidae) from around the world and summarise their biogeography. Fifty-eight phylospecies (S1–58) are recognised by DNA sequencing grouping in eight clades and almost all are shown to be morphologically distinguishable. A further 148 morphospecies, that have not yet been sequenced, have sufficiently distinct morphology to be recognised and we hypothesise there could be at least another 100 rather cryptic and less common species that we have not been able to distinguish confidently to include in this review. We recognise the following families and genera: Family Cribroelphidiidae (clade F), containing the genera Cribroelphidium and Protelphidium; Family Elphidiellidae containing the genera Cryptoelphidiella (clades D and E), Elphidiella (clade B), Emayerella (replacement name for Mayerella junior homonym), and Rectoelphidiella; Family Elphidiidae s.l. (clades A, B, H and I), containing the genera Australononion (n. gen.) (clade I), Elphidium (clades A and H), Epistomaroides, Hispidoelphidium (n. gen.), Millettoelphidium (n. gen.) (clade H), Stomoloculina, and Toddinella (clade B); Family Haynesinidae (clade C), containing genera Aubignyna and Haynesina; Family Notorotaliidae, which molecular analyses confirm branches among these “elphidiids” has been reviewed previously and contains genera Buccella, Cristatavultus, Notorotalia, Parrellina and Porosorotalia. The families Elphidiidae and Elphidiellidae are based on morphological characters, as molecular analysis shows them to be polyphyletic but for the moment a clear morphological distinction is not possible for the obtained molecular clades. Seven molecular species and 34 morphospecies are described and named as new: Cribroelphidium calvomarcileseae, C. inflatogunteri, C. knudsenae (S3), C. revetsi (S41), Cryptoelphidiella daisyana, C. schweizerae, Elphidium altenbachi (S49), E. apthorpae, E. canni, E. davidhaigi, E. fajemilai, E. feylinghansseni, E. gischleri, E. goldsteinae, E. hanseni, E. hollisi, “E.” hulmei (S39, S57), E. kawagatai (S33), E. korsuni, E. larsi, E. lobulatum, E. lunatum, E. mouangaae, E. pereirai, E. pilleti (S18), E. poagi, E. sabaaae, E. scottorum, E. thisseni, E. yankoae, Epistomaroides fordererae, Haynesina lecozei, Millettoelphidium culveri (S51), M. yassinii, Protelphidium hottingeri, Toddinella akandaensis, T. crundwelli, T. darlingae, T. grenfelli, T. lutzei, and T. spezzaferriae. Two genotypes of “Elphidium” hulmei are genetically distinct but morphologically cryptic and unable to be separated using morphology. A further 16 unnamed morphospecies are described but not formally named because of insufficient material to do so. A neotype is proposed for Epistomaroides punctulatus (d’Orbigny) and a lectotype for Elphidium owenianum (d’Orbigny). Elphidiids live in mostly shallow seas (hyposaline to hypersaline) and occur throughout the world except for around the coast of the bulk of Antarctica. No species is cosmopolitan but a few (e.g., Australononion simplex, Cribroelphidium clavatum, C. decipiens, C. gunteri, C. knudsenae, C. lidoense, Elphidium advena, E. alvarezianum, E. articulatum, E. fax, “E.” formosum, E. gerthi, E. hanseni, E. jenseni, E. longipontis, Haynesina germanica, Hispidoelphidium hispidulum, Preotelphidium schmitti and Toddinella incerta) are widespread in two or more ocean regions, whereas the majority are endemic to smaller areas. Twenty biogeographic “provinces” are recognised by cluster analysis of presence/absence records with the highest diversities in the northwest Pacific and tropical East Indies-North Australia provinces with 74 and 49 species each. At the highest level of clustering their world biogeography can be divided into three large regions – Arctic and Atlantic; Indian and Pacific; and Southern Ocean. Levels of endemism in our “provinces” range between 0 (five provinces) and 33% (Southern Ocean). This review identifies at least 33 non-indigenous species (2 genotypes, 31 morphospecies) presumably introduced by accidental anthropogenic transfer in the last several centuries, probably in ship’s ballast, across large oceanic barriers to establish disjunct distribution patterns.

Non-marine foraminifera are among the least-studied groups of protists due to their low population densities, patchy distribution, and spatiotemporal variability. This study investigated foraminifera from four caves within the Dinaric karst region of southeastern Europe, using both morphological and molecular methods. Our results confirm the presence of foraminifera in all examined caves. A new monothalamous foraminifer, Lacogromia cepelaki sp. nov., is described based on morphological and molecular data from Jopićeva Cave (Croatia). Three additional Lacogromia taxa are informally described from different caves. However, due to the lack of distinct morphological characteristics, their formal taxonomic description will require molecular analyses of live specimens. A further important outcome of this study is the morphological description of Spirolocammina petrae sp. nov., discovered in Miljacka II Cave (Croatia). This represents the first discovery of an agglutinated tubothalamid foraminifer adapted to a freshwater environment. As no molecular data could be obtained, its phylogenetic position remains undetermined, and further research will be necessary.

A new genus and species of a monothalamid foraminifera, Adhaerentella dendrocorona, has been identified through phylogenetic and morphological assessment from the Pacific Ocean abyssal plain at Station M, off California. After at least 1 year of colonization time on the seafloor at 4000 m, 141 specimens belonging to the new species were observed attached to plastic substrate deposited on the bottom as a part of the Seafloor Epibenthic Attachment Cube (SEA3) experiments. Adhaerentella dendrocorona is characterized by agglutinated hemispherical tests connected with dendritic tubes. The delicate phyllosilicate branches collapse when not immersed, but embedding in agar or resin facilitates imaging. MicroCT images reveal compositional differences between the agglutinated base and branching tube structures, consisting of phyllosilicates. Despite sharing some morphological similarities with other attached agglutinated genera, such as Capsammina, Crithionina, and Hemisphaerammina, Adhaerentella dendrocorona is genetically different from the latter genera and branches in the monothalamid Clade M. Adhaerentella dendrocorona has a close relationship with undescribed monothalamids from Antarctica, suggesting the possible global distribution of the genus. This study indicates that monothalamid foraminifera are important components of attached abyssal meiofauna, which have evolved morphologies that are likely adapted for suspension feeding in oligotrophic environments that feature hard substrates.

Single chambered foraminifera (monothalamids) occur in all marine habitats, as well as freshwater and terrestrial environments. Their genetic diversity by far surpasses their morphological variety and a combination of morphological and molecular data is needed to distinguish species and classify them. We present here the results of an integrative taxonomic study of monothalamids from bathyal and abyssal samples collected from the Bering Sea and Aleutian Trench and from coastal waters in the Southern Hemisphere. Based on morphological and molecular (DNA barcode sequences of 18S rRNA) data, we describe Flaviatella gen. nov., a member of monothalamid Clade Y. The type species, F. profunda gen. & sp. nov., was isolated from surface sediment samples collected at lower bathyal depths (3553 m) in the Bering Sea and at abyssal depths (4612 m) close to the nearby Aleutian trench. Specimens collected in 2007 from near the Japan trench (5360 m depth) are morphologically similar and genetically identical to this species. We also describe a second species of the new genus, F. siemensma sp. nov., based on samples collected in 2019 from a shallow subtidal bay in the Falkland Islands. Flaviatella is a new genus with a large geographic distribution and a wide bathymetric range, showing that monothalamid taxa can successfully colonize disjunct areas and adapt to different environmental conditions.

A new genus and species of a monothalamid foraminifera, Adhaerentella dendrocorona, has been identified through phylogenetic and morphological assessment from the Pacific Ocean abyssal plain at Station M, off California. After at least 1 year of colonization time on the seafloor at 4000 m, 141 specimens belonging to the new species were observed attached to plastic substrate deposited on the bottom as a part of the Seafloor Epibenthic Attachment Cube (SEA) experiments. Adhaerentella dendrocorona is characterized by agglutinated hemispherical tests connected with dendritic tubes. The delicate phyllosilicate branches collapse when not immersed, but embedding in agar or resin facilitates imaging. MicroCT images reveal compositional differences between the agglutinated base and branching tube structures, consisting of phyllosilicates. Despite sharing some morphological similarities with other attached agglutinated genera, such as Capsammina, Crithionina, and Hemisphaerammina, Adhaerentella dendrocorona is genetically different from the latter genera and branches in the monothalamid Clade M. Adhaerentella dendrocorona has a close relationship with undescribed monothalamids from Antarctica, suggesting the possible global distribution of the genus. This study indicates that monothalamid foraminifera are important components of attached abyssal meiofauna, which have evolved morphologies that are likely adapted for suspension feeding in oligotrophic environments that feature hard substrates.

Early identification of non-indigenous species is important, as they have the potential to disrupt biogeochemical cycles, ecosystem stability, and trophic energy transfer in fragile ecosystems. Non-indigenous species may impact the functioning of the Baltic Sea ecosystem, the largest brackish water body in the world. This study presents the first record of the non-indigenous Asian foraminiferal species Ammonia confertitesta in the southeastern Baltic Sea. The species was recorded at 6 out of 14 sampling stations in the Gulf of Gdańsk, Poland, with one station sampled several times throughout the year, where A. confertitesta was consistently present. The species was also found in Puck Bay, a shallow western branch of the Gulf of Gdańsk. Our finding marks the first modern record of the genus Ammonia in the southeastern Baltic Sea. It provides new evidence for the rapid spread of A. confertitesta in European waters, highlighting its ability to thrive in environments where other calcareous foraminiferal species face difficulties. Morphometric comparisons with a population of the same species found in the western Baltic Sea shows that the Gulf of Gdańsk specimens are smaller. This may indicate that the species has reached its limits of environmental tolerance. However, given the increasing abundance of A. confertitesta in the Gulf of Gdańsk, it is important to monitor its further progression and investigate its long-term ecological impact on native species and the Baltic Sea ecosystem.

A non-indigenous species (NIS) of benthic foraminifera was first identified in a core collected in 1993 in San Francisco Bay, California, USA, and subsequently identified as Trochammina hadai Uchio, 1962. Archived samples and literature reviews were used to determine that the species, which is native to Asia, arrived in San Francisco Bay between the early 1960s and 1983. Through molecular analyses of specimens, archived samples and literature reviews from 1930–1983, and site surveys of harbors and estuaries along the western North American seaboard in 1994–2024, in total more than 2500 samples, we documented the presence of T. hadai at 73 locations in the USA and four in Canada. Trochammina hadai has also been recovered at nine sites in Sweden, two in France, three in Brazil, and two locations at one site in Australia. The rapid temporal and geographic spread of the NIS T. hadai in a non-native location is illustrated by a time series from 1930 to 2024 in San Francisco Bay. Between 1980 and 1986, the species' range expanded from low abundance (1.5 %) at a single site to cover nearly the entire South Bay with > 70 % abundance at some locations. By 1995 and continuing into 2010, the species expanded its range into the central and northern portions of San Francisco Bay, commonly with abundances of > 30 % and sometimes exceeding 70 %. This expansion may predate 1995, but a lack of samples makes it difficult to be more precise. Unfortunately, two Pb-210 and Cs-137-dated cores (BC01 and BC02) recovered from northern South Bay and Central Bay did not clarify this point, but additional cores may. Trochammina hadai is an infaunal opportunist that thrives in polluted locations. We surmise the species was introduced along the west coast of the USA in Puget Sound between 1902 and the 1920s, with cultivated oysters and oyster larvae and associated plant matter and residual sediment. This probably also happened in some areas of France, Sweden, and Brazil, where Japanese oysters were introduced in 1966, 1970, and 1975, respectively. After World War II, commercial shipping expanded dramatically and, with it, the release of ballast water and sediment in receiving ports, which introduced NIS worldwide. This primary vector of introduction occurred in large industrial harbors in several countries, sometimes followed by secondary introductions in small industrial centers and marinas by mud attached to the anchors and anchor chains of smaller boats.