vs Coastal Silver-stiletto

Chrysosphaerella annulata compared with Acrosathe annulata

Key Differences

is Not Evaluated while Coastal Silver-stiletto is Least Concern.

Taxonomic Classification

Rank		Coastal Silver-stiletto
Kingdom	Chromista (Chromista)	Animalia (Animals)
Phylum	Ochrophyta (Ochrophyta)	Arthropoda (Arthropods)
Class	Chrysophyceae (Chrysophyceae)	Insecta (Insects)
Order	Ochromonadales (Ochromonadales)	Diptera (Diptera)
Family	Paraphysomonadaceae	Therevidae
Genus	Chrysosphaerella	Acrosathe
Species	Chrysosphaerella annulata	Acrosathe annulata

Conservation Status

NE — Not Evaluated

Coastal Silver-stiletto

LC — Least Concern

Physical Characteristics

Attribute		Coastal Silver-stiletto
Diet	—	—
Average Lifespan	—	—
Average Length	—	—
Average Weight	—	—

Habitat & Geographic Range

Habitat

Native to Europe, inhabiting ecosystems characteristic of the region.

Range

Distributed across Norway and Sweden.

Coastal Silver-stiletto

Habitat

Typically found in virtually all terrestrial and freshwater habitats.

Range

Distributed across Belgium, Denmark, Norway, and Sweden.

Chrysosphaerella annulata is a colonial freshwater chrysophyte microalga in the genus Chrysosphaerella, class Chrysophyceae. Unlike unicellular loricate chrysophytes, Chrysosphaerella species form spherical or ellipsoidal free-floating colonies in which individual cells are embedded in a common gelatinous matrix. The individual cells bear long siliceous scales with distinctive ring-like or annular structures — referenced by the species epithet annulata — projecting outward from the colony surface, giving the colony a spiny appearance under microscopy. These siliceous scales are species-specific and their morphology, as revealed through electron microscopy, is the primary character for identifying Chrysosphaerella species. C. annulata has been recorded from Norwegian and Swedish freshwater environments, consistent with the Scandinavian emphasis in chrysophyte research and the high diversity of chrysophytes in boreal freshwater systems. Chrysosphaerella colonies are planktonic, inhabiting the limnetic zone of oligotrophic to mesotrophic lakes where they may form locally conspicuous populations during favorable conditions. The species uses chlorophylls a and c with fucoxanthin for photosynthesis, contributing to primary production. Chrysosphaerella scales can accumulate in lake sediments, providing a record of past community composition and environmental conditions. C. annulata has not been assessed under IUCN criteria and is classified as Not Evaluated. Its documentation contributes to understanding the diversity of colonial chrysophyte forms in northern European freshwater ecosystems.

Coastal Silver-stiletto

Coastal silver stiletto (Acrosathe annulata) is a slender robber fly in the family Therevidae, native to northwestern Europe, including the United Kingdom, France, the Netherlands, Belgium, and Scandinavia. Adults are found on coastal sand dunes and sandy heathland, where they perch on bare sand to ambush small flying insects. Stiletto flies in the family Therevidae are characterised by a slender body, long pointed abdomen, and predatory habits; adults prey on a variety of small dipterans and other flying insects during warm, sunny periods. Larvae develop in sandy soil, where they are also predatory, feeding on other invertebrate larvae. Acrosathe annulata is a habitat specialist restricted to open, sandy coastal habitats with sparse vegetation—environments that have declined substantially across northwestern Europe due to dune stabilisation, recreational disturbance, and the cessation of traditional dune management. The IUCN lists it as Least Concern, though regional conservation bodies in the United Kingdom have flagged population declines. It is considered an indicator of high-quality coastal sand dune habitats and is monitored through national invertebrate surveys.