Psammophaga, Arnold, 1982

Gschwend, Florian, Majda, Aneta, Majewski, Wojciech & Pawlowski, Jan, 2016, Psammophaga fuegia sp. nov., a New Monothalamid Foraminifera from the Beagle Channel, South America, Acta Protozoologica 55 (2), pp. 101-110 : 109

Global Psammophaga diversity and phylogeny

This study highlights, once more, that much work remains to be done in the description of monothalamid diversity. Despite the facts that Clade E and Psammophaga are among the best established groups of monothalamids, that Psammophaga species are cosmopolitan in easily accessible shallow water marine habitats, and that they are amongst the most abundant members of monothalamid communities, there are only five Psammophaga species that have been described until now, including the present description.

Numerous reports and sequence data from different parts of the globe are available and we can discern eight well established phylotypes in addition to the five described species ( Fig. 4 ). Most phylotypes show a restricted distribution; only one phylotype from the Black Sea and P. crystallifera were found in very distant locations. The former was recovered mostly in the Black Sea but also once in Southampton, the latter was found in Admiralty Bay and in Sweden but nowhere else until now. Furthermore, one to three phylotypes were detected per sampling location. From New Zealand, Svalbard, Panama, the Beagle Channel we know only a single type per region, from Antarctica we know two distinct species, and from Denmark and the Black Sea we have records of three different phylotypes. The relationships among the different phylotypes remain unclear, and the sampling locations, although distributed over the globe, remain scarce compared to a global scale. If Psammophaga is a cosmopolitan genus, which is suggested by the current data, and as the types show restricted distribution patterns, we are missing major parts of its species diversity. No sequences or morphological data is available from Africa, Asia, Australia or polar regions of North America. Moreover, no sequence data is available for P. simplora , which is the type species for the genus. Like many other monothalamids, Psammophaga remains undersampled on a global scale and the poor phylogeny may reflect this state of knowledge.

High abundances of Psammophaga species observed in this and other studies ( Majewski et al. 2005, 2007; Pawlowski and Majewski 2011) indicate that they have an important ecological role at least on a microbial scale. Moreover, it suggests that they are highly competitive in some environments. The reasons for this would be interesting and it may be possible that the ingestion of mineral particles is part of the answer. Our data and the study of P. magnetica suggest that the organisms are capable to select which mineral particles they ingest. The comparison between P. magnetica and P. fuegia indicates that the selection depends on the species and/or mineral composition of the sediment. However, we do not understand the relative importance of these factors. How did the ability to ingest mineral particles evolve? Do different species prefer different mineral compositions? What are the advantages of the mineral ingestion? Altin-Ballero et al. (2013) mention two reasons why mineral ingestion could be beneficial: it could act as ballast and stabilize the Psammophaga cells or the species could feed on bacteria growing on the particles.

In summary, we can state that the species diversity of Psammophaga is poorly known, but due to their high abundance and diversity, their cosmopolitan distribution in shallow water settings, and their special characteristic features, species of this genus should be target- ed for studies focusing on biogeographical, ecological, and evolutionary questions concerning the monothalamid foraminifera.

Figures

Fig. 4. ML-tree of the genus Psammophaga, with Vellaria zucchellii as outgroup. Bootstrap values bigger than 80% are shown. Described species are highlighted in grey.