Microworld

world of amoeboid organisms

Actinophrys salsuginosa
A. salsuginosa

Actinophrys salsuginosa Patterson, 2001

Diagnosis: Actinophrys species with nucleolar material forming a peripheral layer of small aggregates, and with a cyst incorporating spherical siliceous elements.

Dimensions: Main body 29-114 µm in diameter, mean 44 µm ; nucleus 10-19.2 µm.

Ecology: Brackish water, Swanpool, England.

Remarks: As with other actinophryids, A. salsuginosa is able to form cysts with multiple layers in the wall. Sintered siliceous beads mostly 0.3-1.0 µm in diameter form a layer of the cyst wall.
Actinophrys salsuginosa resembles A. sol closely in general appearance and size of trophic individuals. It can be distinguished from A. sol (sensu Patterson 1979) because of the arrangement of the nucleolar material and by the spherical (as opposed to flattened) shape of the siliceous elements of the wall. The body size of A. salsuginosa is similar to that of A. sol, although the new species has a more vacuolated outer region, and more delicate (longer and thinner) arms. The two species differ in their tolerance of saline conditions. A. sol did not survive in salinities greater then 20% sea water. A. salsuginosa continued to grow actively in 40% salinity. Under similar salinity conditions, the new spe­cies was slightly larger, more vacuolated, with fine arms, formed larger masses during feeding; these masses did not adhere to the substrate to the same extent as those of A. sol. A. salsuginosa differs also from the marine A. tauryanini because it is usually half the size, has a different nucleolar morphology, is tolerant of low salinity regimes, and may have a layer of large peripheral vacuoles. A. salsuginosa can be distinguished from A. pontica by the nucleolar configuration.
Two ultrastructural characteristics of A. salsuginosa suggest a close relationship to Actinosphaerium nucleofilum. They are: location of the nucleolar sub­stance as a peripheral layer of small grains (Anderson and Beams 1960, Shigenaka et al. 1980), and siliceous components of the cyst wall of both are sintered spheres (Patterson and Thompson 1981).

(all remarks from Mikrjukov and Patterson, 2001)

Ferry Siemensma, created March 3, 2019; last modified March 07, 2022
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