brittlestar vs Compact Stonewort

Amphiura filiformis compared with Nitella tenuissima

Key Differences

brittlestar is Least Concern while Compact Stonewort is Extinct.

Taxonomic Classification

Rank	brittlestar	Compact Stonewort
Kingdom	Animalia (Animals)	Plantae (Plants)
Phylum	Echinodermata (Echinoderms)	Charophyta (Charophyta)
Class	Ophiuroidea (Ophiuroidea)	Charophyceae (Charophyceae)
Order	Amphilepidida (Amphilepidida)	Charales (Charales)
Family	Amphiuridae	Characeae
Genus	Amphiura	Nitella
Species	Amphiura filiformis	Nitella tenuissima

Conservation Status

brittlestar

LC — Least Concern

Compact Stonewort

EX — Extinct

Physical Characteristics

Attribute	brittlestar	Compact Stonewort
Diet	—	—
Average Lifespan	—	—
Average Length	—	—
Average Weight	—	—

Habitat & Geographic Range

brittlestar

Habitat

Native to Europe, inhabiting ecosystems characteristic of the region.

Range

Distributed across Denmark, Norway, and Sweden.

Compact Stonewort

Habitat

Native to Asia and Europe and North America, inhabiting ecosystems characteristic of the region.

Range

Distributed across Brazil, Norway, Sweden, Taiwan, and United States.

brittlestar

The Brittlestar (Amphiura filiformis) is a species in the genus Amphiura. It is currently classified as Least Concern on the IUCN Red List. Native to Europe, inhabiting ecosystems characteristic of the region.

Compact Stonewort

<em>Nitella tenuissima</em>, a stonewort formerly found in fresh and brackish water habitats, was a member of the charophyte family Characeae — the algal lineage most closely related to land plants. Historical records document its occurrence across Brazil, Norway, Sweden, Taiwan, and the United States, where it inhabited clear, oligotrophic lakes, ponds, and slow-flowing water bodies with low nutrient levels. Like other Nitella species, it was a delicate, translucent, submerged aquatic plant lacking the calcium carbonate encrustation of related genera, forming low-growing mats on soft sediments in well-illuminated shallow water. The species played a role in aquatic ecosystems by stabilising lake sediments, contributing to water clarity, and providing microhabitat for invertebrates and small aquatic organisms. <em>Nitella tenuissima</em> is classified as Extinct by the IUCN, having not been recorded from any of its former localities despite targeted searches. The primary causes of its extinction are believed to be widespread eutrophication of freshwater habitats driven by agricultural nutrient runoff and sewage discharge, which eliminated the clear, nutrient-poor conditions on which the species depended. The loss of this stonewort is emblematic of the broader decline of freshwater charophyte diversity across the Northern Hemisphere. Biological traits including historical morphological measurements and reproductive parameters are documented only in sparse historical herbarium specimens and early botanical literature.