Oblique Tetradesmus
Tetradesmus obliquus
Tetradesmus obliquus is a freshwater-context green microalga also encountered under the historical names Scenedesmus obliquus and Acutodesmus obliquus. A named culture can provide photosynthetic biomass in a defined food-web setting, but green water does not identify the species or prove feed value. The 6–25 µm display range is only a broad cell-level observation guide, and no fixed magnification establishes the taxon.
Water type
Freshwater
Biological group
Chlorophyceae
Record type
Species
Recognition confidence
Medium
Ecological functions
Primary producer, Live food
Aquarium impact
Context-dependent
Culture and management
Dedicated starter culture
Typical size
6 µm – 25 µm
Visible to the naked eye
No, not as an individual
Useful starting magnification
No universal threshold supported by reliable evidence
Identity, habitat, and ecological role
Identity and taxonomic resolution: This card uses Tetradesmus obliquus in the Chlorophyceae, Sphaeropleales and Scenedesmaceae convention. Scenedesmus obliquus and Acutodesmus obliquus remain search names for the same taxon concept; generic authorities differ in treatment, not in evidence for three aquarium organisms. A green suspension, photograph or similar colony does not inherit any of those names. Retain group-level wording unless traceable provenance and suitable diagnostic evidence support a species or strain conclusion.
Morphology and dimensions: The stored 6–25 µm range is a broad guide for an individual cell, not a diagnostic boundary. Exact sources report 5–10 µm for NIES-2279, 8.1–12.3 µm for UTEX 3031 and a historical 5–27 µm description. Cell organisation and morphology vary with strain and culture conditions. Record several intact cells with a calibrated scale, state whether a measurement concerns a cell or a coenobium, and do not identify a sample from size or shape alone.
Habitat and microhabitat: Freshwater is the catalog context, not a complete distribution or salinity claim. NIVA-CHL 105 has River Nile, Egypt, freshwater provenance, but that locality belongs to a named strain and is not the species' native origin or global range. Water-column samples, surface films and cultured suspensions can contain different communities. Green biomass is an observation context; it does not establish Tetradesmus, purity, a nutrient cause, toxicity or a universal aquarium response.
Role in the food web: Tetradesmus obliquus is primary-producer biomass. A named culture was used as food in a defined experiment, supporting a conditional producer-to-consumer relationship rather than a general claim for green water. Strain, growth phase, concentration, nutritional composition and receiving consumer determine whether that relationship applies. A visible suspension may be mixed material, so it does not prove live-food value, benefit, hazard, stocking suitability or an ecological diagnosis.
Observation, culture, and ecological relationships
Where to look and how to sample: Separate a documented culture from unknown green water. For named material, retain the strain label, source, vessel, date and portion sampled. For an aquarium observation, record water-column, film, debris or other-surface origin with the visible trend and local context. These sample types can contain different communities. One drop documents only examined material; it cannot establish absence elsewhere, name a coloured suspension or transfer a collection identity to local biomass.
How to observe and identify: Use a calibrated scale and compare several intact cells and fields, recording preparation and sample history. The 6–25 µm guide can help describe a cell but cannot distinguish T. obliquus from related green microalgae or resolve a strain. No fixed magnification value is stored: 400× may aid observation but is not a universal identification threshold. Where the exact taxon matters, use diagnostic morphology or molecular comparison rather than a single image, size or coenobium.
Presence and meaning in an aquarium: A green suspension records pigment or biomass in that sample, not confirmed Tetradesmus, water quality, toxicity, disease, safe feed or a treatment target. Interpret it with location, timing and measured system context. Freshwater is the card context, while a Nile provenance belongs only to one named strain; neither point supplies a global range, a native-origin claim or a salinity instruction. Do not promote colour, abundance or a historical name into a diagnosis or management conclusion.
Culture, maintenance or use: Starter culture means traceable material, not any green water that resembles a microalga. NIES-2279 is documented as axenic, unialgal and clonal at its recorded state, but those attributes and collection conditions do not transfer to another lot. A named culture can be evaluated in a defined food-web setting, yet the sources provide no universal home-culture recipe, feeding ration, transfer rule or consumer recommendation. Keep strain and condition evidence with each culture.
Documented ecological relationships: The documented relationship is directional: Tetradesmus biomass was supplied as food in a consumer experiment. This supports the primary-producer and conditional live-food labels, not an assumption that every strain, culture phase or green suspension is nutritious, clean or accepted by a consumer. Food value depends on the culture, growth state, concentration and preparation, as well as the receiving organism. Record provenance before transferring a published food-web role to local material.
Risks, prevention and limits: This is not a therapy or chemical-control card. The evidence does not support medication, algaecides, removal, disinfection, a fixed prevention regime or a universal aquarium-control protocol from observing Tetradesmus or green water. Control is evidentiary: retain strain and sample provenance, distinguish documented material from unknown biomass, and assess context before interpreting a visible change. Do not treat unknown green water as axenic starter culture, safe feed or proof of a problem.
Geographic origin and distribution
Origin
Cosmopolitan or introduced
Identification and observation data
- Record type
- Species
- This is a species-level entry for Tetradesmus obliquus under the catalog convention Chlorophyceae, Sphaeropleales, Scenedesmaceae and Tetradesmus. Scenedesmus obliquus and Acutodesmus obliquus are historical search names for the same taxon concept, not separate aquarium organisms. A supplier label, green suspension or similar coenobium does not establish a species or strain. Keep an unknown observation at a broader green-alga level unless traceable provenance and suitable diagnostic evidence support a narrower conclusion.
- Recognition confidence
- Medium
- Identification confidence is medium only when several intact cells, a calibrated scale, sample history and suitable comparison evidence agree. The 6–25 µm guide, a green colour, one image or a coenobium cannot resolve Tetradesmus obliquus or a strain. Published dimensions differ among named material, and culture conditions alter morphology and organisation. No fixed magnification is a species threshold; use curated morphology or molecular evidence when an exact identity changes a research, culture or feeding decision.
- Biological group
- Chlorophyceae
- Tetradesmus obliquus is a green microalga in the phytoplankton-and-microalgae group. The group label describes photosynthetic biomass, not an identity for every green-water event. The sealed ranks retain Chlorophyceae, Sphaeropleales, Scenedesmaceae and Tetradesmus, while Scenedesmus and Acutodesmus remain transparent historical combinations. Do not use the group label, a colony shape or suspended colour to convert an unknown aquarium sample into the named species.
- Ecological functions
- Primary producer, Live food
- Primary producer and live-food are conditional roles. Tetradesmus obliquus makes photosynthetic biomass, and a named culture served as food in a defined consumer experiment. That evidence does not show that another strain, an arbitrary culture or spontaneous green water is nutritionally suitable, clean or accepted by a chosen consumer. Growth state, concentration, preparation, nutritional composition and receiving organism remain material conditions before a published producer-to-consumer relationship can be transferred.
- Aquarium impact
- Context-dependent
- Impact is context-dependent. Green biomass can be an observation in a freshwater aquarium, but it is not confirmed Tetradesmus, a water-quality measure, a toxin finding, a disease diagnosis, a safe feed or a management target. One named Nile strain establishes only its own freshwater provenance, not a species origin or global range. Interpret a visible change with its sample location, timing, other organisms and measured conditions rather than treating colour or abundance as a conclusion.
- Culture and management
- Dedicated starter culture
- Starter culture means traceable named material maintained for a defined purpose. NIES-2279 is recorded as axenic, unialgal and clonal, but those are accession-specific observations rather than promises for every Tetradesmus culture. The evidence provides no universal home-culture recipe, food-safety claim or transfer rule. Preserve the strain label, source and current condition, and do not replace an uncertain culture with unknown green water or treat a supplier name as proof of identity, purity or suitability.
- Typical size
- 6 µm – 25 µm
- The stored 6–25 µm range is a broad, cell-level observation guide for Tetradesmus obliquus, not a species or strain boundary. Exact material spans 5–10 µm for NIES-2279, 8.1–12.3 µm for UTEX 3031 and a historical 5–27 µm description. Measure several intact cells with a calibrated scale and state whether the number concerns a cell or a coenobium. Size, shape or one colony alone cannot identify the taxon, culture quality or food value.
- Visible to the naked eye
- No, not as an individual
- Individual cells are not naked-eye identifiable. Dense green biomass or a film can be visible, but that observation does not establish Tetradesmus obliquus, a named strain, purity, safety, food quality or the cause of the change. A sample may contain other algae, microbes and debris. Retain the sample context and examine representative material with a scale before assigning a taxon or an ecological meaning to visible green water; visibility is not a substitute for diagnostic evidence.
- Useful starting magnification
- No universal threshold supported by reliable evidence
- No fixed magnification value is stored because no retrieved exact-taxon source makes 400×, or another setting, a universal observation or identification threshold. Magnification can record how representative cells were examined, but it cannot itself resolve the species, a strain, culture purity or food quality. Use a calibrated scale, multiple intact cells and provenance; where exact identity matters, apply curated specialist morphology or molecular comparison appropriate to the question.
Links to Aquarium SOS
Microworld ecological network
Links based on documented kinship, food webs, biofilms, and ecological functions.
