Spirolocammina petrae Siemensma, Bakovic & Holzmann, 2025
Diagnosis: The test has an elongate ovate shape, with chambers arranged in a planispiral coil, convex sides, and a subrounded periphery, with five externally visible chambers. The test wall is densely covered with small, irregularly shaped mineral particles interspersed with much finer particles. The apertural tube is typically longer than the main body. The aperture is terminal, located at the end of the final chamber, smooth, and without teeth or any ornamentation.
Description of the type material: The test resembled a long, chambered cylindrical tube, folded multiple times. In lateral view, four chambers were externally visible on one side and three on the opposite side, with the two final chambers exposed on both sides. Under transmitted light, the proloculus appeared as a rounded chamber. The test wall was densely covered with small, irregularly shaped mineral particles ranging from 5 to14 μm in size, interspersed with much finer particles (~2 μm). It measured 7–8 μm in thickness. Test length varied from 140 to 349 μm, and width from 54 to 77 μm. The aperture measured 10 μm wide in the largest test and 6.5 μm in the smallest. Smaller specimens had a shorter apertural tube, sometimes shorter than the main body, whereas in larger specimens, the apertural tube extended relatively far beyond the main body. The aperture was V-shaped on one side and rounded on the opposite side. Clear cytoplasmic streaming was observed in the only living specimen. This specimen was isolated, and its DNA extracted, although no sequence was obtained.
Ecology: This species inhabits clay and sinter pools in the vadose zone of Miljacka II Cave, Croatia, in complete darkness. These sites are flooded only during rare extreme events, with surface water influence suggested by occasional dead algae found in the pools.
Remarks: The two extant described species in the genus Spirolocammina are known from deep-sea environments (Burmistova, 1978; Earland, 1934). Based on morphological data, the new species is provisionally assigned to the genus Spirolocammina. Currently, no sequences are available for species within this genus, and further research is needed to clarify their phylogenetic relationships.
