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Alegret, Ortiz & Kaminski (eds.), 2012. Ninth International Workshop on Agglutinated Foraminifera, Abstract Volume Benthic foraminiferal squatters: species that inhabit the tests of other foraminifera Andrew J. GOODAY National Oceanography Centre, Southampton, European Way, Southampton SO14 3ZH, UK e-mail: ang@noc.ac.uk There are scattered literature records of foraminifera that inhabit the tests of other benthic or planktonic foraminifera on an obligate or opportunistic basis. Calcareous species of the genus Ramulina (suborder Lagenida) have long been known to adopt this mode of life (Carter 1889; Jones and Chapman 1897; Rhumbler 1911). However, this contribution with focus on monothalamous (single-chambered, non-calcareous) inhabitants. The first report was that of Rhumbler (1894), who described five species of organic-walled allogromiids from the empty shells of the large agglutinated foraminiferan Saccammina spherica. The inhabiting test forms an elongate, more or less convoluted tube in Ophiotuba gelatinosa, Dactylosaccus vermiformis and Dendrotuba nodulosa; the other two species, Rhynchogromia variabilis and Rhynchosaccus immigrans, have ovate to sausage-shaepd tests. Only O. gelatinosa and D. nodulosa appear to be obligate inhabitants. The thread-like, organic-walled species Nemogullmia longevariabilis sometimes occupies foraminiferal tests and polychaete tubes, although the association is not obligate (Nyholm, 1956). Christiansen (1971) illustrated an undescribed shallow-water form with long and thin pseudopodia that lives inside empty tests of Saccammina sphaerica and feeds exclusively on other foraminifera. In a culture experiment using sediment from the North Sea, Moodley (1990) observed an undescribed monothalamous species that rapidly crawled into empty Quinqueloculina shells when offered the opportunity. Gooday (1986a) found numerous novel monothalamous foraminifera inhabiting empty globigerinacean shells in samples from the Porcupine Seabight (1340 m water depth; NE Atlantic). Many of these forms were apparently obligate inhabitants that constructed various kinds of agglutinated structures (e.g. branched and unbranched tubes and lumps) on the exterior of the host shell. Within the framework of the ECOMAR project, we recently discovered similar organisms inhabiting globigerinacean shells at bathyal depths (~2,500 m) at 4 sites located around 53°N (NW, NE sites) and 49°N (SW, SE sites) on the Mid Atlantic Ridge. One form, assigned to the poorly-known genus Hospitella, comprises a series of brown, organic-walled compartments (‘pseudochambers’), which occupy the chambers of the host shell and end in a tubular extension that projects externally. Another form, described as a new genus and species, has a cell body enclosed in a very thin, organic wall and containing numerous stercomata and iron-rich xanthosomes. The inhabiting organism constructs a short conical, finely-agglutinated structure on exterior of the host shell. A variety of other forms, including discrete allogromiid-like cells, compact masses of stercomata and protoplasm, and agglutinated spheres, were also found within planktonic shells at the ECOMAR sites. These inhabitant foraminifera (or foraminifera-like organisms) represented 18% (NW site) 38% (NE station), 39% (SE station), and 46% (SW station) of the stained foraminiferal assemblages at the ECOMAR sites. Although it is often difficult to differentiate between species, our results suggest that inhabitant foraminifera may contribute significantly to biodiversity in the deep sea. This is of interest in the context of recent molecular studies on environmental (sediment) samples. Lecroq et al. (2011) used a Next Generation Sequencing approach to analyse foraminiferal species richness in five different oceanic regions. More than 33
Alegret, Ortiz & Kaminski (eds.), 2012. Ninth International Workshop on Agglutinated Foraminifera, Abstract Volume half (47%) of the Operational Taxonomic Units (OTUs) could not be placed in any high-level taxonomic groups. These undetermined OTUs made up between ~25% and 55% of the foraminiferal assemblages based on microbarcode sequences. At least one third of the OTUs that could be assigned to higher taxa were placed within the monothalamous foraminifera. The monothalamous and undetermined OTUs together represented >80% of OTUs in most of the samples. It is possible that some of the undetermined sequences detected by Lecroq et al. (2011) correspond to inhabitant foraminifera. They therefore represent an overlooked but potentially important facet of deep-sea biodiversity that warrants closer taxonomic scrutiny. References: Carter, H.J. 1889. Ramulina parasitica, a new species of fossil Foraminifera infesting Orbitolites Mantelli, var. theobaldi, with comparative observations on the process of reproduction in the Mycetozoa, Freshwater Rhizopoda, and Foraminifera. Annals and Magazine of Natural History (6) 4, 94-101. Christiansen, B.O. 1971. Notes on the biology of foraminifera. Troisième Symposium Européen de Biologie Marine. Vie et Milieu, Supplement No 2 vol II. 465-478. Gooday, A.J. 1986. Meiofaunal foraminiferans from the bathyal Porcupine Seabight (northeast Atlantic): size structure, standing stock, taxonomic composition, species diversity and vertical distribution in the sediment. Deep-Sea Research, 33, 1345-1373. Jones, T.R. & Chapman, F. 1897. On the fistulose Polymorphinae and on the genus Ramulina. Part II – the genus Ramulina. Zoological Journal of the Linnean Society, 168, 334-354 Lecroq, B., Lejzerowicz, F., Bachar, D., Christen, R., Esling, P., Baerlocher, L., Østerås, M., Farnelli, L. & Pawlowski, J. 2011. Ultra-deep sequencing of foraminiferal microbarcodes unveils hidden richness of early monothalamous lineages in deep-sea sediments. Proceedings of the National Academy of Sciences of the USA. doi:10.1073/pnas.1018426108 Moodley, L. 1990. ‘Squatter’ behaviour in soft-shelled foraminifera. Marine Micropaleontology, 16, 149-153. Nyholm, K-G. 1956. On the life cycle and cytology of the foraminiferan Nematogullmia longivariabilis. Zoologiska Bidrag från Uppsala, 31, 484-495. Rhumbler, L. 1911. Die Foraminiferen (Thalamophoren) der Plankton Expedition. Zugleich Entwurf eines natuerlichen Systems der Foraminiferen auf Grund selektonischer und mechanischphysiologischer Faktoren. Erste Teil, Die allgemeinen Organizationsverhaltnisse der Foraminiferen. Ergebnisse der Plankton-Expedition der Humboldt Stiftung. Kiel und Leipzig. Verlag von Lipsius & Tischer (1909), 1-331. Rhumbler, L. 1913. Die Foraminiferen (Thalamophoren) der Plankton Expedition. Zugleich Entwurf eines natuerlichen Systems der Foraminiferen auf Grund selektonischer und mechanischphysiologischer Faktoren. Zweiter Teil. Systematik: Arrhabdamminidia, Arammodisclidia und Arnodosammida. Ergebnisse der Plankton-Expedition der Humboldt Stiftung. Kiel und Leipzig. Verlag von Lipsius & Tischer (1909), 332-476. 34
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