Catalogue of Organisms: Existence of the Rosalinidae

Among the many fashionable foraminiferans, one of the distinguished radiations is amongst members of the Rotaliida, characterised by globose chambers and calcareous, hyaline check partitions. Among the many quite a few households making up the Rotaliida are members of the Rosalinidae.

Benthic type of Rosalina globularis, from Brady (1884).

Rosalinids could also be thought to be pretty typical-looking marine rotaliids with the check rising freely as a low trochospire (so a flattened cone or dish form). The aperture of the check is a low slit on the inside margin alongside the umbilicus (Hansen & Revets 1992). Rosalinids have a posh life cycle involving each benthic and planktonic phases (Sliter 1965). The asexually reproducing diploid stage is benthic. Relying on circumstances, diploid people could divide to supply different diploid people, leading to a number of asexual generations. Ultimately, nevertheless, the diploid technology will endure meiosis to supply the haploid sexual technology (within the frequent species Rosalina globularis, that is induced by publicity to hotter water). Within the sexual technology, a big globular chamber types at maturity that covers the umbilical facet of the check. This float chamber turns into full of fuel, permitting the foram to disperse planktonically earlier than releasing gametes to supply the subsequent diploid technology. Planktonic people are distinct sufficient in look from their benthic counterparts that they have been lengthy mistaken for distinct taxa earlier than their id was revealed by lab cultures.

Life cycle of Rosalina globularis, from Sliter (1965).

Nearly all of forams are particulate feeders. A community of filamentous pseudopodia radiating outwards from the cell physique captures micro-organisms and different natural particles. Nevertheless, one genus of rosalinids, Hyrrokkin, lives as parasites on sessile invertebrates (Cedhagen 1994). Species of this genus have variously been discovered on sponges, corals and bivalves. On sponges, they decide on the inhalent floor of the sponge and dissolve the underlying tissues. On bivalves, they type pits on the shell floor from which they bore holes by means of to the physique cavity. Pseudopodia prolonged by means of this gap enable the foram to feed on host tissue. Infested hosts could bear a number of scars from the foram transferring about on the outer floor. The forams might also feed on different animals comparable to polychaete worms or bryozoans hooked up to the floor of their main host. In such circumstances, Hyrrokkin stays in its authentic pit however develops an irregularly formed chamber with its aperture directed in the direction of the alternate prey. Hyrrokkin species evidently do effectively from their rapacious way of life: whereas different rosalinids are solely a fraction of a millimetre in diameter, Hyrrokkin sarcophaga is an absolute big reaching round six millimetres throughout and with protoplasm containing hundreds of nuclei. Proving as soon as once more that one could make an excessive amount of revenue from the labour of others.

Cross-section of Hyrrokkin sarcophaga boring into shell of file clam Acesta excavata, from Schleinkofer et al. (2021).

REFERENCES

Cedhagen, T. 1994. Taxonomy and biology of Hyrrokkin sarcophaga gen. et sp. n., a parasitic foraminiferan (Rosalinidae). Sarsia 79: 65–82.

Hansen, H. J., & S. A. Revets. 1992. A revision and reclassification of the Discorbidae, Rosalinidae, and Rotaliidae. Journal of Foraminiferal Analysis 22 (2): 166–180.

Sliter, W. V. 1965. Laboratory experiments on the life cycle and ecologic controls of Rosalina globularis d’Orbigny. Journal of Protozoology 12 (2): 210–215.