Staurastrum spp.

star desmids

Worldwide fresh water (soft, nutrient-poor)

Native to North America

Overview

Staurastrum spp. is a large genus of single-celled green algae in the family Desmidiaceae, the desmids, living mostly in clean, soft, slightly acidic fresh water such as bog pools, lakes, and ponds. Each microscopic cell is divided into two mirror-image halves, called semicells, joined at a narrow waist, a hallmark of the desmids. In Staurastrum spp. the semicells are often drawn out into several radiating arms or spines, so that seen from the end the cell looks star-shaped or triangular, which gives the genus its name. Cells are typically 0.0008-0.004 inch (20-100 micrometres) across, green from their chloroplasts, and either drift in the plankton or rest among submerged plants. The radiating arms and spines are thought to slow sinking and deter tiny grazers. Staurastrum spp. reproduces mainly by simple cell division, with each daughter cell growing a new half, and occasionally by conjugation, in which two cells fuse to form a thick-walled resting spore. The genus is diverse and is studied as an indicator of clean, nutrient-poor, soft water, and many species decline where water is polluted or enriched. Cell shape and ornament, seen under a microscope, separate the many species.

Native Range

Staurastrum spp. lives in fresh water worldwide, especially in clean, soft, slightly acidic bog pools, lakes, ponds, and ditches. It is most diverse in nutrient-poor waters and is found among the plankton and among submerged plants.

Suggested Uses

Staurastrum spp. and other desmids are used as indicators of clean, soft, nutrient-poor fresh water, and their decline signals pollution or enrichment. The genus is a popular subject in microscopy and in teaching algal symmetry and diversity. It is grown in laboratory culture for research.

How to Identify

Identify under a microscope by the single green cells split into two mirror-image halves joined at a narrow waist, with the halves drawn out into radiating arms or spines so the cell looks star-shaped or triangular end-on. The symmetrical, ornamented semicells separate Staurastrum spp. from other desmids and green algae; species are told apart by cell shape and spine pattern.

Appearance

Colors

Foliage Colors

green

Bloom Information

Staurastrum spp. does not flower. It reproduces mainly by cell division, each half-cell growing a new mirror-image half, and occasionally by conjugation, where two cells join to form a thick-walled resting spore. Populations rise in clean, soft water during the warmer, well-lit months.

Growing Conditions

Water & Climate

Water Needs

High

Care & Maintenance

Care Guide

Staurastrum spp. lives only in clean, soft, often slightly acidic fresh water and is sensitive to pollution and nutrient enrichment, which favour coarser algae over desmids. It cannot be cultivated like a garden plant, though it is grown in laboratory culture in soft, low-nutrient media under moderate light. The genus persists in healthy bog pools, lakes, and ponds, and disappears as water quality falls. Clean, undisturbed, nutrient-poor water sustains it.

✓ Toxicity

Non-toxic

Algae