Testate protists in the genus Gromia (‘gromiids’, supergroup Rhizaria) are common and diverse in marine settings. However, their ecological significance is not well understood, partly because they remain largely undescribed with most records being of the type species, G. oviformis. To enhance our knowledge of gromiid biodiversity, we use morphological and genetic data to describe four new species with tests of different shapes from sublittoral depths (21–136 m) in South Georgia fjords: G. pashukae (ovate), G. landrethi (spherical), G. amygdaliformis (almond-shaped), and G. saoirsei (elongate), maximum lengths 3.4, 2.5, 1.4 and 4.5 mm, respectively. We also describe two smaller ( ~1 mm) gromiid species from intertidal sites on the Falkland Islands: G. cedhageni (ovate test with finely granular, orange-coloured contents), and Gromia psammophila (subrectangular test with numerous small mineral grains embedded in pale, finely granular material). Gromia landrethi is also represented by DNA sequences from specimens collected in Ushuaia (Argentina) and G. psammophila by sequenced specimens from southern Chilean fjords, but the other species are known only from localities in South Georgia or the Falkland Islands. Analysis of partial SSU rRNA genes confirms the presence of these six new species, as well as an undescribed species represented by a clade of three sequences branching separately. Our results increase the number of described gromiid species from 10 to 16, and underline the importance of these poorly known relatives of the foraminifera in higher-latitude intertidal and fjord settings.
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