Xanthidium antilopaeum

The genus Xanthidium is characterized by biradiate cells furnished with a series of spines along the outer  margin. Usually, the semicell centre is more or less inflated and sculptured by granules or large scrobicles.

The most common species of this genus is X. antilopaeum. It is marked by hexagonal semicells the apical and lateral angles of which as a rule are furnished with two stout spines each.

Quite a number of varieties have been described, mutually differing in the disposition of the marginal spines and the central pattern of scrobiculae. Some of those varieties are that different from the nominate variety that they might be considered species of their own.

Of the varieties herewith represented, the nominate variety (var. antilopaeum) in the Netherlands is of rather common occurrence  in various mesotrophic, slightly acidic to slightly alkaline water bodies whereas var. planum appears to be confined to acidic moorland pools and var. laeve is predominantly encountered in oligotrophic quaking bog hollows.

Two cells of Xanthidium antilopaeum var. antilopaeum.

Cell dimensions (L x B): ca  70 x 75 µm.

<<image on the left:

Xanthidium antilopaeum var. laeve differs from the nominate variety by a widely open cell sinus.

image © Henk Schulp

image on the right:

Xanthidium antilopaeum var. planum is marked by downwards projected lateral spines

image © Henk Schulp